Embed Size (px)
DESCRIPTION
a re-brand of the existing magazine new scientist
Citation preview
N N E W S C I E N T I S T4 April 2011www.newscientist.com issue 01
G o o g l e s ’ M o o n
B r i a n C o x
T e r r e s t r i a l F o s s i l s
U n i v e r s e E x t r e m e s
C r e a t i n g S t a r s
4 April 2011 3
New Scientist4 N
Uk
Lacon House, 84 Theobald’s Road,
London WC1X 8NS
Tel +44 (0) 20 7611200
Fax +44 (0) 20 7611250
To Subscribe
UK and International
Tel +44 (0) 8456 731 731
The price of the New Scientist annual
subscription is UK £143, Europe € 228,
USA $154, Canada ¢182, Rest of World
$293, Postmaster: Send address changes to
New Scientist, PO Box 3806, Chesterfield,
MO 63006-9953, USA.
Contacts
Editorial
Tel +44 (0) 20 7611 1202
opinion2newscientist.com
Picture Desk
Tel +44 (0) 20 7611268
Who’s who
newscientist.com/people
Contact Us
newscientist.com/contact
Enquiries
Tel +44 (0) 20 76111202
© 2011 Reed Business information ltd,
England
New Scientist is published weekly
by Reed Business ltd.
ISSN 0262 4079
c o n t e n t s
12
33
16
4 April 2011 5
News
Cosmology
Tourist Space
Creating Stars
Terrestrial Fossils
Googles’ Moon
Brian Cox
Planet Planet
Universe Extremes
Snowflake Galaxies
Artificial Satellite
Geminid Meteors
4
6
10
12
16
28
32
36
38
54
56
60
12
38
56
New Scientist6 N
Covered in spiders’ webs, these cocooned trees in Sindh, Pakistan, are an unexpected result of floods that hit the region in 2010. To escape from the rising waters, millions of spiders crawled up into trees. The scale of the flooding and the slow rate at which the waters receded, have left many trees completely enveloped in spiders’ webs. Although slowly killing the trees, the phenomenon is seemingly helping the local population. People in Sindh have reported fewer mosquitos than they would have expected given the amount of stagnant water in the area. It is thought the mosquitoes are getting caught in the spiders’ webs, reducing their numbers and the associated risk of malaria.
Trees cocooned by spiders could reduce malaria risk.
N e w s
World's wind and waves have been rising for decades.
Fake Mars ship Lands.
Mars500 has landed. On 14 February, three crew members from the simulated mission to Mars stepped out of the windowless mock spaceship where they hace spent the past eight months, and into a small room with a sandy floor and twinkling lights. After two more ‘Mars Walks’, they will be reunited with the other three crew members and start the eight-month ‘journey’ back to Earth.
Wind speeds and wave heights over the world’s oceans have been rising for the past quarter-century. It’s unclear if this is a short-term trend, or a symptom of longer-term climatic change. Either way, more frequent hurricanes and cyclones could be on the horizon. Ian Young at the Australian National University
in Canberra and colleagues analysed satellite data from 1985 to 2008 to calculate wave heights and wind speeds over the world’s oceans. They found that winds had strengthened – speeding up over most of the world’s oceans by 0.25 to 0.5 per cent, on average, each year. Overall, wind speeds were 5 to 10 per cent faster than they had been 20 years earlier. The trend was most pronounced for the strongest winds. For instance, the very fastest 1
per cent of winds were getting stronger by 0.75 per cent per year, says Young. Average wave height was also on the rise, but less so; and the highest waves showed the strongest trend. The results were compared against conventional measurements taken from deep-water buoys and numerical modelling. “There is variability, but the same general features are observed,” Young says.
6 0 S E C O N D S
Portraits of a comet.
Early on 15 Feruary, NASA’S Stardust spacecraft flew past comet Tempel 1, taking 72 pictures on the potato-shaped object. When New Cisnrist went to press, the close-ups had not been released. NASA hopes to compare them with snaps taken by the Deep Impact mission to Tempel 1 in 2005.
4 April 2011 7
The Power of one brain.
In 2007, all the general computers in the world could together perform 6.4 10 instructions per second. That roughly equals the number of nerve impulses produced by one human brain each second.
Cold Cure
To banish an impending cold, take a zinc supplement at the first sniffle. Areview of 15 trials showed zinc administered in syrup, lozenges or tablets within 24 hours of symptons appearing significantly reduced the secerity and length of the illness, possibly through zinc’s antiviral properties.
Stolen DNA
Around 1 in 10 gonorrhoea bacteria include a small chunk of human DNA in their genetic make-up - the first DNA has been found to have jumped from a mammalian genone to bacterial one. What role, if any, the human DNA performs in the bacterium remains a mystery.
Wind speeds and wave heights over the world’s oceans have been rising for the past quarter-century. It’s unclear if this is a short-term trend, or a symptom of longer-term climatic change. Either way, more frequent hurricanes and cyclones could be on the horizon. A Young at the Australian National University in Canberra and colleagues analysed satellite data from 1985 to 2008 to calculate wave heights and
World’s wind and waves have been rising for decades.
Sea salt may be hampering Japan nuclear recovery.
Corrosive salt from seawater may be adding to problems at the Fukushima Daiichi nuclear plant, damaged two weeks ago by the megaquake and tsunami in Japan. The flood swept away backup power units meant to keep cooling water flowing through the reactors in an emergency, forcing the plant’s operators to use seawater to cool its reactors and ponds storing spent fuel. Concerns are now arising about the effect of salt deposits in reactors and cooling systems as the water is boiled away by intense heat from the fuel.
As much as 26 tonnes of salt may have accumulated in reactor unit 1, and twice that amount in the larger units 2 and 3, according to estimates in The New York Times by Richard Lahey, who was General Electric’s chief of safety research for boiling water reactors when the company installed them at Fukushima Daiichi. Lahey told the newspaper that an international group of nuclear experts is informally urging Japanese emergency workers to try to flood the vessels with fresh water as soon as possible to flush the salt deposits back out to sea.
wind speeds over the world’s oceans. They found that winds had strengthened – speeding up over most of the world’s oceans by 0.25 to 0.5 per cent, on average, each year. Overall, wind speeds were 5 to 10 per cent faster than they had been 20 years earlier. The trend was most pronounced for the strongest winds. For instance, the very fastest 1 per cent of winds were getting stronger by 0.75
per cent per year, says Young. Average wave height was also on the rise, but less so; and the highest waves showed the strongest trend. The results were compared against conventional measurements taken from deep-water buoys and numerical modelling. “There is variability, but the same general features are observed,” Young says
New Scientist8 N
The
biggest
questions
are still
unanswered. We
do not know the
true size of the
universe, even whether
it is infinite or not.
4 April 2011 9
Cosmologists study the universe as a whole: its birth, growth, shape, size and eventual fate.
Hubble found that most galaxies are red shifted: the spectrum of their light is moved to longer, redder wavelengths. This can be explained as a doppler shift if the galaxies are moving away from us. Fainter, more distant galaxies have higher red shift, implying that they are receding faster, in a relationship set by the hubble constant. The discovery that the whole universe is expanding led to the big bang theory. This states that if everything is flying apart now, it was once presumably packed much closer together, in a hot dense state. A rival idea, the steady-state theory, holds that new matter is constantly being created to fill the gaps generated by expansion. But the big bang largely triumphed in 1965 when Arno Penzias and Robert Wilson discovered cosmic microwave background radiation. This is relic heat radiation emitted by hot matter in the very early universe, 380,000 years after the first instant of the big bang.
The growth of the universe can be modelled with Albert Einstein’s general theory of relativity, which desribes how matter and energy make space-time curve. We feel that curvature as the force of gravity. Assuming the cosmological principle (that on the largest scales the universe is uniform), general relativity produces fairly simple equations called Friedmann models to describe how space curves and expands. According to these models, the shape of the universe could be like the surface of a sphere, or curved like the surface of a saddle. But in fact, observations suggest that it is poised between
I n t r o d u c t i o n C o s m o l o g yCosmologists study the
universe as a whole:
its birth, growth, shape,
size and eventual fate.
Npace-time curve
New Scientist1 0 N
the two, almost exactly flat. One explanation is the theory of inflation. This states that during the first split second of existence, space expanded at terrifying speed, flattening out any original curvature. Then today’s observable universe, grew from a microscopic patch of the original fireball. This would also explain the horizon problem - why it is that one side of the universe is almost the same density and temperature as the other. The universe is not totally smooth, however, and in 1990 the COBE satellite detected ripples in the cosmic microwave background, the signature of primordial density fluctuations. These slight ripples in the early universe may have been generated by random quantum fluctuations in the energy field that drove inflation. Topological defects in space could also have caused the fluctuations, but they do not fit the pattern well. Those density fluctuations form the seeds of galaxies and galaxy clusters, which are scattered throughout the universe with a foamy large-scale structure on scales of up to about a billion light years. All these structures form because gravity amplifies the original fluctuations, pulling denser patches of matter together.
In simulations, however, visible matter does not supply enough gravity to create the structure we see: it has to be helped out by some form of dark matter. More evidence for the dark stuff comes from galaxies that are rotating too fast to hold together without extra gravitational glue. Dark matter can’t be like ordinary matter, because it would have made too much deuterium in big-bang nucleosynthesis. When the universe was less than 3 minutes old, some protons and neutrons fused to make light elements, and cosmologists calculate that if there had been much more ordinary matter than we see, then the dense cauldron would have brewed up a lot more deuterium than is observed. Instead, dark matter must be something exotic, probably generated in the hot early moments of the big bang - maybe particles such as WIMPs (weakly interacting massive particles) or lighter axions, or, less likely, primordial black
holes. An alternative to dark matter is modified Newtonian dynamics, or MOND, a theory in which gravity is relatively strong at long range.
Another dark mystery emerged in the 1990s, when astronomers found that distant supernovae are surprisingly faint - suggesting that the expansion of the universe is not slowing down as everyone expected, but accelerating. The universe seems to be dominated by some repulsive force, or antigravity, which has been dubbed dark energy. It may be a cosmological constant (or vacuum energy) or a changing energy field such as quintessence. It could stem
from the strange properties of neutrinos, or it could be another modification of gravity. The WMAP spacecraft put the standard picture of cosmology on a firm footing by precisely measuring the spectrum of fluctuations in the microwave background, which fits a universe 13.7 billion years old, containing 4% ordinary matter, 22% dark matter, and 74% dark energy. WMAP’s picture also fits inflationary theory. However, a sterner test of inflation awaits the detection of cosmic gravitational waves, which the rapid motions of inflation ought to create, and which would leave subtle marks on the microwave background. The density of dark energy is far smaller than the vacuum energy predicted by quantum
Cosmology
Dark matter
Dark energy
4 April 2011 1 1
theory. That is seen as an extreme example of cosmological fine tuning, in that a much larger value would have torn apart gathering gas clouds and prevented any stars from forming. That has led some cosmologists to adopt the anthropic principle - that the properties of our universe have to be suited for life, otherwise we would not be here to observe it.
The biggest questions are still unanswered. We do not know the true size of the universe, even whether it is infinite or not. Nor do we know its topology - whether space wraps around on itself. We do not know what caused inflation,
or whether it has created a plethora of parallel universes far from our own, as many inflationary theories imply. And it is not clear why the universe favours matter over antimatter. Early in the big bang, when particles were being created, there must have been a strong bias towards matter, which the standard model of particle physics cannot explain. Otherwise matter and antimatter would have annihilated each other and there would be almost nothing left but radiation. The fate of the universe depends on the unknown nature of dark energy and how it behaves in the future: galaxies might become isolated by acceleration, or all matter could be destroyed in a big rip, or the universe might
collapse in a big crunch - perhaps re-expanding as a cyclic universe. The universe could even be swallowed by a giant wormhole. And the true beginning, if there was one, is still unknown, because at the initial singularity all known physical theories break down. To understand the origin of the universe we will probably need a theory of quantum gravity.
Cosmology
N
Hubble found that most
galaxies are red
shifted: the specrum
of their light
is moved to
longer, redder
wavelengths.
Unanswered questions
New Scientist1 2 N
On 26 February, two days after NANA’s space
shuttle Discovery blasted off on its final
flight, a plane loaded with researchers soared
over Cape Canaveral, Florida, home to the
shuttle’s launch pad, in preparation for a very
different era of space science.
These lucky few were training to conduct experiments aboard a new generation of spacecraft built by commercial outfits like Virgin Galactic. The vehicles’ primary purpose will be to ferry tourists to the edge of space, about 100 kilometres above Earth’s surface. But it is the potential to expand research in astronomy, planet formation, and other disciplines that had scientists salivating at a recent meeting on the science applications of space tourism in Orlando, Florida. “We’re entering a regime where the space scientist is going to be able to go into the field the same way that geologists and biologists and oceanographers do,” says Daniel Durda of the Southwest Research Institute (SwRI) in Boulder, Colorado. On 28 February, SwRI signed the first contracts to fly scientists to space on vehicles made by Virgin Galactic and XCOR. The flights are expected to be up and running by 2013 or sooner. When they do, what can we expect to learn from the on-board experiments? Science has already been done on the International Space Station, the shuttle, satellites and high-altitude balloons. But Alan Stern, who is leading the new programme at SwRI, says that the planned flights, which will include a few minutes of weightlessness, will make a unique contribution.
For starters, he is excited by the prospect of solving an enduring mystery about the moon’s atmosphere, which began with NASA’s crewed Apollo missions to the moon in the 1970s. From lunar orbit, NASA astronauts reported complex and unexplained light shows just before sunrise, including shafts of light that appeared suddenly and seemed to radiate from the moon’s horizon. Potential explanations include excited sodium atoms in the moon’s tenuous atmosphere and sunlight glinting from dust particles. Without measurements it is not possible to confirm or rule out these ideas. In principle, a telescope could do the job, by detecting the wavelength of the light, but it would need to be positioned so that the moon’s shadow blocks most of the sun’s light. Short of going back into lunar orbit, the only way to do this is to send a spacecraft into the path of a solar eclipse. That can’t be guaranteed with existing telescopes in fixed orbits around Earth, nor high-altitude balloons, which drift with the wind. Uncrewed sounding rockets, which launch from fixed sites, are also unsuitable. Yet it should be relatively simple to pull off with a telescope on either Virgin Galactic or XCOR’s vehicles, which are designed to be launched at least once a day from ordinary runways anywhere in the world. “It’s a problem that you can solve better with these suborbital vehicles than with any other tools we have,”
T o u r _ _ _ _ _ _ _ _ _ i s t S p a c e
4 April 2011 1 3
tourism vehicles in development have done so yet. But there are grounds for optimism. Virgin Galactic’s SpaceShipTwo is closely based von its predecessor SpaceShipOne that safely flew to space and back three times in 2004. Suborbital spaceflight is also easier than the orbital variety in some respects. The vehicles have lower-power engines, need far less fuel and don’t experience the tremendous heat of re-entering the atmosphere from orbit. “I don’t have any doubt that five years from now, multiple space lines will be operating large numbers of suborbital flights,” says Stern. “It’s going to change things in ways we probably can’t imagine.”
to the so called “ignorosphere”, a region above the reach of balloons and below the orbits of satellites. The results of these experiments could help improve climate models. This is also the ideal vantage point for spotting potentially dangerous asteroids that spend most of their time closer to the sun than is the Earth. These tend to be lost in the glare of the daytime sky for ground-based telescopes. Faith Vilas of the Planetary Science Institute in Tucson, Arizona, and Luke Sollitt of the Citadel in Charleston, South Carolina, are designing a telescope to fly on suborbital vehicles to do this and other kinds of astronomy. All of these experiments rely on firms getting their vehicles safely flying to space and back, which is not guaranteed since none of the space
N
T o u r _ _ _ _ _ _ _ _ _ i s t S p a c e
says Stern, who presented the idea at the recent conference. Suborbital vehicles are also ideally positioned to carry out experiments probing the origins of our solar system. The planets formed from dust grains in a nebula that swirled around the infant sun. But it is not clear why colliding grains stuck together to form larger and larger objects, rather than bouncing off each other or shattering, as rocks in laboratories on Earth often do. A simulation in microgravity might give us an answer. Enter Blue Origin, which also makes suborbital vehicles, headed by Jeff Bezos, founder of Amazon. It has already agreed to fly a suite of dust collision experiments on an uncrewed flight Suborbital spacecraft will allow frequent access
New Scientist1 4 N
Many major observatories already have – or are developing – systems that use powerful lasers to project pinpoints of light high in the atmosphere. These serve as artificial guide stars for adaptive-optics systems that correct for less-than-ideal “seeing” (atmospheric turbulence). When everything works, celestial targets can be recorded with astonishing clarity. Most observatories use a single laser-generated beacon, which limits how much of the telescopic field can be manipulated using adaptive optics. Typical targets are discrete objects like close-spaced double stars or compact clusters. But a new development at Gemini South
On 22 January, researchers test-fired
a laser that created a tight five-
star “constellation” in the sky above
Cerro Pachón.
On 22 January, researchers test-fired
a laser that created a tight five-
star “constellation” in the sky above
Cerro Pachón.
Many big
observatories
point a single
laser at the sky to
measure atmospheric
turbulence. Recently, the
Gemini South telescope tested
a five-laser system.
4 April 2011 1 5
observatory (shown) high in the Chilean Andes holds promise for extending adaptive optics’ high resolution to much wider fields. On 22 January, researchers test-fired a laser that created a tight five-star “constellation” in the sky above Cerro Pachón. With an output of 50 watts – 1000 times more powerful than a typical handheld unit – the laser is tuned to sodium atoms’ strong yellow emission at 589 nanometres. After being split into five separate beams, the laser light illuminates sodium atoms naturally present in a layer within the mesosphere, about 90 kilometres high. Those atoms then fluoresce at the same wavelength
to create five artificial stars, each about 1 arcsecond across, at the corners and center of a 1-arcminute square. Gemini South is the first facility to use this multiple-beam technique with a sodium laser. Project leader Celine d’Orgeville explains that Gemini’s Multi-Conjugate Adaptive Optics (MCAO) system should allow the observatory’s 8.1-metre aperture to record ultrasharp views over fields up to 2 arcminutes across [1/15 of the apparent width of the moon]. Sometime next year astronomers hope to start using the MCAO system to study objects ranging from just-born stars to distant galaxies.
At least two other facilities are pursuing adaptive-optics systems that employ multiple guide stars. In 2007 the European Southern Observatory’s Very Large Telescope tested a system that uses natural guide stars, but its use is limited because of the scarcity of suitable telescopic fields. That same year the MMT Observatory in Arizona (shown) tested a system that uses a powerful green laser to create multiple artificial stars using Rayleigh scattering in the lower atmosphere. N
Many big
observatories
point a single
laser at the sky to
measure atmospheric
turbulence. Recently, the
Gemini South telescope tested
a five-laser system.
New Scientist1 6 NCreating Stars
4 April 2011 1 7Creating Stars
On 22 January, researchers
test-fired a laser
that created a
tight five-star
“constellation”
in the sky
above Cerro
Pachón.
New Scientist1 8 N
There are many sound scientific reasons
to go back to the moon, but there is one
that I believe deserves more attention:
to go fossil hunting.
It sounds like a non-starter. The moon is lifeless, always has been and probably always will be. But that very deadness makes it enormously important, both to those searching for clues to how life got started on Earth, and also on other planets. It's possible that the moon's surface holds an unprecedented fossil record of life on Earth and from around our solar system. Here on Earth, the oldest unambiguous evidence for life dates back to 3.5 billion years ago. There is more tenuous evidence that life existed as long as 3.8 billion years ago, but this is based on controversial interpretations of rock chemistry rather than fossils of life itself. Either way, life on Earth seems very ancient indeed - until you consider the age of the planet, now reliably dated at about 4.6 billion years old. Did it really take a billion years after the formation of our planet for life to find a way? Not necessarily. Many biologists see no reason why it couldn't have started earlier. Problem is, if life did get going earlier than 3.5 billion years ago, the prospects for finding evidence of it are not good. Despite searching ever more inaccessible and inhospitable locales, such as northern Greenland and the jocularly named North Pole region in Western Australia, geologists have yet to find pristine sedimentary rocks - the kind that could contain fossils or chemical signatures of life - older than 3.5 billion years. Thanks to plate tectonics and Earth's restless atmosphere, everything older has been eroded, melted or squeezed out of existence.
4 April 2011 1 9
New Scientist2 0 N
For all we know there could have been whole armies of bacteria, or even multicellular organisms, much earlier than 3.5 billion years ago. There are still undoubtedly other places on Earth with old rocks, but the list of unexplored places grows smaller every year.
However, the moon's surface is almost certainly littered with Earth rocks, many of which could well be older than anything found at home. Because the moon has no atmosphere and no plate tectonics, anything that lands there stays in pristine condition. The moon might just be the place to find the answer to the frustrating question of when life really began on Earth. Over the past 20 years or so it has become abundantly clear that planets and moons, including our own, regularly exchange large quantities of material flung into space by asteroid impacts. The most famous of such impacts on Earth happened 65 million years ago, at the end of the Cretaceous period, and was almost certainly responsible for the demise of the dinosaurs. From what we know about the violence of that event, it seems reasonable to assume that asteroids crashing into Earth can indeed fling material into space. Proof of the event can be found in any layer of sedimentary rock spanning the Cretaceous/Tertiary (K/T) boundary. A thin but distinctive "impact layer" separates the older Cretaceous rocks from the younger Tertiary ones. Back in 1980, father and son team Luis and Walter Alvarez of the University of California, Berkeley, showed that these impact layers are composed of oxidised sediment, centimetres thick in places. Crucially, these layers contain tektites, small bits of Earth rock which have been flung into space and melted on re-entry into the atmosphere. The Alvarez team also showed that these impact layers are composed of small amounts of the killer asteroid mingled with larger quantities of the Earth's crust gouged out by the impact.
Terrestrial Fossils
Pristine landscape
4 April 2011 2 1
That bits and pieces of crater and asteroid are spread all over the world is eloquent testament to the violence of the event, and evidence that most of the ejected crust took to space or even circled the globe before finally falling back to Earth. But the crucial question is whether the impact propelled significant quantities of terrestrial material to the moon. An article published in the journal Icarus in 2002 (vol 160, p 183) makes it clear that while most of the K/T impact material found its way back to Earth, an appreciable quantity broke free and headed out on a space voyage. Some of it is surely still out there; most, however, fell onto other bodies of
our solar system. Some landed on Mars; some on Venus and even on Mercury. But the largest quantity of material came to rest amid the lunar regolith. And those bits of rock might just carry the remains of life - microbes, plants, even bits of some very surprised T. rex - from that distant and very bad day on Earth. Finding remnants of Cretaceous life on the moon would certainly be a novelty, but would be unlikely to tell us anything that we did not know. The real find would be bits of unaltered sedimentary rock older than 3.5 billion years, which might contain fossils, as well as organic signals of microbial activity from around the time life was getting started on our planet.
The idea of searching the moon for evidence of early life on Earth was first proposed in 1999 by John Armstrong when he was a graduate student wrestling with the problem of Earth's missing sedimentary record at the University of Washington in Seattle. He was inspired in no small way by the controversy over the meteorite ALH 84001. Discovered in Antarctica in 1984, the meteorite rose to prominence in 1996 when David McKay of Johnson Space Center in Houston, Texas, claimed that it contained fossils of bacterial life. It was a remarkable claim, given that the meteorite clearly came from Mars. Thanks to chemical data from NASA's 1976 Viking
Terrestrial Fossils
The command
module is coated
with reflective material
to mirror the Sun’s
heat. About 12 feet
in diameter
weighing 12,000
pounds.
New Scientist2 2 NTerrestrial Fossils
Battered
highlands
on thelunar
farside,looking
south in a view
covering an area
about the size
of switzerland.
4 April 2011 2 3Terrestrial Fossils
Battered
highlands
on thelunar
farside,looking
south in a view
covering an area
about the size
of switzerland.
New Scientist2 4 N
Astronaut Alan Bean
holds a special
sample container
designed to
aid studies of
the lunar
enviroment.
4 April 2011 2 5
missions, it is possible to distinguish bits of Mars from the far more common meteorites originating in the asteroid belt. Indeed, one of the great surprises for meteorite hunters was the realisation that many hunks of Mars lay among thousands of catalogued meteorites on Earth. The consensus now is that ALH 84001 doesn't contain fossils, but even so the meteorite showed that planetary rocks could routinely travel vast distances across the solar system. It also breathed new life into the concept of panspermia, the idea that microbes could travel from planet to planet, or planet to moon, on rock blasted into space by an impact. Studies done by Joe Kirschvink, a specialist in palaeomagnetism from the California Institute of Technology in Pasadena, later showed that microbes could survive both the initial impact and the fiery descent onto a gas-cloaked planet
or a jarring thud on some airless wasteland such as the moon. Kirschvink and his then
graduate student Ben Weiss tested this out by looking at the magnetic
properties of meteorites. Since heat can destroy a magnetic
field, the two reasoned that if you could still
detect a magnetic signal in the
interior of a
meteorite, the temperature must have stayed below 100 °C, even if the exterior had been scorched. A cool interior could ensure the safe passage of any microbial life buried deep inside the rock, as well as fossils and chemical signals of past life. Armstrong reasoned that if impacts can propel near-pristine Martian rocks to Earth, surely it was possible for pristine Earth rocks to end up on the moon. In 2001, he teamed up with fellow graduate student Llyd Wells and a post doc named Guillermo Gonzalez to begin the serious work of calculating whether a large impact on the Earth could send appreciable amounts of Earth material to the moon. They decided that acceptance of the idea that there are early Earth rocks on the moon requires two demonstrations. First, calculate how big the impact would need to be to propel crust material beyond the planet's gravitational pull. Second, you would need to show that the frequency of these events was high enough for appreciable quantities of material to land on the moon. If such travel required the sort of impact caused by rare, gigantic events such the K/T event or even bigger, then there would be very little chance of the moon harbouring enough terrestrial material to justify either crewed or robotic missions to search for it. If, however, more modest-sized impactors would do the job, there is a good chance of finding Earthly treasures on the moon - maybe even Venusian and Martian ones too, for all the planets have undergone periodic bombing by asteroids.
How big an impact would be required to propel Earth rocks
all the way to the moon? The energy of an impact is related
to several factors: the size of the impactor,
its velocity, the angle at which
it strikes and the
composition of the impactor and the rocks it hits. It turns out that even a relatively small asteroid, 100 metres in diameter and leaving craters a kilometre across, would be capable of ejecting rocks that could reach the moon. It is hard to know how often an impact this size strikes the Earth, because terrestrial craters are quickly eroded away. But since the moon has a similar impact history to the Earth, the frequency of craters a kilometre across or greater on the moon leads to an estimate of how often these kinds of impact events have occurred on Earth. It seems the rate is roughly once every 100,000 years recently, and far more frequently in the distant past. Armstrong and his colleagues also modelled the volume of Earth material that would be likely to reach the moon. Astonishingly, they calculated that the impact of a body 100 metres in diameter would deposit about 120 kilograms of fairly pristine Earth rock on each 100 square kilometres of the lunar surface. And given the many thousands of such impacts on Earth throughout its history, this is just a fraction of the total amount. Even a conservative estimate suggests there must be thousands, perhaps even a few millions of tonnes of Earth rock up on the moon. So what about the age of the material? Much of the crucial missing interval on Earth coincided with (but was not caused by) the heavy bombardment - a solar system-wide event that happened between 4.2 and 3.8 billion years ago. We only have to look at the crater-pocked face of the moon to see how destructive that barrage of material was. During the bombardment it has been estimated that the Earth was struck by thousands of asteroids that were K/T sized or bigger, perhaps up to a thousand kilometres across. The largest may have been as big as Texas is wide. Most of the terrestrial material on the moon is likely to be about the right age. And if life ever got going on Mars and Venus, chances are it was around this time too. There is ancillary evidence that the lunar regolith does indeed contain Earth material. In the 1970s, NASA geologists discovered that more than 1 per cent of the 380 kilograms of moon rock brought back by the Apollo missions was not lunar. At the time they assumed that
Terrestrial Fossils
Heavy bombardment
New Scientist2 6 NTerrestrial Fossils
4 April 2011 2 7Terrestrial Fossils
Alan Shepard and Edger
Mitchell visited this
boulder field,
which shows a
3-foot-high
boulder at
left.
New Scientist2 8 N
The moon might be
our best chance of
discovering our own
origins, or even if
there was once life on
Mars or Venus. For
that reason alone we
have to go back.
Terrestrial Fossils
Earthrise
seen for
the first time
by human eyes.
Apollo 8 astronaut
William Anders took
this photograph, which
looks southwest
towards Crater Gibbs.
4 April 2011 2 9
most, if not all, of it came from the asteroid belt. Most of it probably does. But some is likely to be from Earth. According to Armstrong, there should be roughly 3 grams of Earth material in the lunar samples. We won't know for sure until someone takes a look. But as a result of Armstrong's work there is renewed interest in looking at the material brought back from the moon, though to date no one has gone back to look at the moon material already here in terrestrial collections in Houston. Back in 2002, Armstrong's publication was interesting, but largely irrelevant given the total lack of planned missions to the moon. Now, however, there is a real possibility of putting his ideas into practice. With the emergence of a new mission for NASA, active planning for a return to the moon is now under way. Looking for fossils on the moon is firmly on the to-do list. As it routinely orbits us, so close yet so far, the moon might be our best chance of discovering our own origins, or even if there was once life on Mars or Venus. For that reason alone we have to go back. N
Terrestrial Fossils
New Scientist3 0 N
On your marks, get set, lift-off: everyone
from garage inventors to aerospace
magnates is racing for the Lunar X Prize.
computers back on Earth. The winner will
G o o g l e s ’ M o o n
Under the harsh sun, shining out
of a pitch-black sky, a four-wheeled
rover zigzags across the cratered
lunar surface. It seems to be looking
for something. Every so often it stops
to sift through the dusty soil, before
moving on again. But one of these
pauses lasts longer than the rest.
Suddenly, an antenna extends skyward,
pointing at the fat blue marble
385,000 kilometres away. Humans back
on Earth who subscribe to Red Rover’s
Twitter feed get the news within
seconds: “We’ve found water!”
That, at least, is the script of
David Gump’s dream. He is part of a
team that is building Red Rover and
plans to send it to the moon. He is
confident that it will not only kick-
start a new era of lunar exploration,
but will also win his team a $20
million prize in the process.
That money is the top award on offer
in the Google Lunar X Prize (GLXP),
money that the internet giant is
putting up as a way of galvanising an
entrepreneurial 21st-century space
race. By the standards of space
exploration this may not be big bucks,
but it has been enough to motivate 29
entrants from around the world. They
are a diverse bunch, including teams
of scrappy young hackers, buttoned-up
defence contractors, and veterans of
the Soviet space programme. There’s
even a team of self-styled wizards.
The top prize will go to the first
to land a robotic rover on the moon,
drive or fly it at least 500 metres
from its landing point, and send
video, still images and data to
Google’s computers back on Earth. The
winner will not only have
unique bragging rights, but
also a proven method for extracting
profitable information about
the moon.
Apart from a handful of deliberate
crash landings, neither human nor
machine has graced the moon’s
surface since 1976. The new missions
could revive long-abandoned dreams.
The moon’s far side, for example,
offers unique opportunities for
observing the universe. Because it
is permanently shielded from the
noise of the world’s radio traffic,
it would be an ideal site for
instruments designed to detect the
faint remnants of the universe’s
formation. Other benefits could also
flow from a moon landing. Any water
that can be extracted from the lunar
surface could be used to fuel voyages
to Mars and beyond. The moon could
even be home to the first permanent
human settlements outside Earth.
The neglect of the past 35 years
is scarcely surprising, given the
ruinous cost of past lunar missions.
At its peak, the Apollo programme that
took men to the moon was consuming
roughly $5.2 billion, or 5.3 per cent
of the US federal budget. The Soviet
Union’s Luna programme was no less
of a budget-buster. That era of vast
projects masterminded by national
space agencies is now over. Even NASA
is discovering that private space
entrepreneurs can innovate far more
cheaply, and that the offer of prize
money can help to get them started.
The earliest of the prize
competitions, the $10 million Ansari
X Prize, called for the private
development of a reusable piloted
space vehicle.
4 April 2011 3 1
It was won in 2004 by Scaled Composites, a company based in Mojave, California, with its SpaceShipOne craft - but its winnings were dwarfed by the estimated $25 million it spent on development and testing. This highlights a problem with competitions like the GLXP. Even for a successful entrant, the prize money alone may not cover development costs. In fact, according to William Pomerantz, who runs the GLXP, on average, the teams will need to spend about $60 million. So the GLXP aims to encourage projects that
can also profit from an existing market: the hunger of organisations such as NASA
and the European Space Agency (ESA) for data. For those who
fail to win the top prize, there is a $5 million prize for
the runner-up, as well as a smattering of
prizes totalling $5 million for
advances such as
travelling significantly more than 500 metres or finding evidence of lunar water (see “Water from a stone”). NASA is supporting the GLXP, and has advised Google on the competition rules. Last year, NASA itself promised a total of $30 million through its Innovative Lunar Demonstrations and Data (ILDD) programme to six projects to collect data that can be used for future robotic and human lunar missions. As it happens, all the winners are also GLXP contenders. But even for outfits that did not receive any of the ILDD funds, the programme signposts the existence of a commercial market that GLXP contenders will be able to tap into long after Google has dispensed its prize money. The Google contest has pulled in talent from all corners of the world. By the time the contest’s sign-up window closed at the end of 2010, 33 teams had signed up, of which 29 are still in the running. They come in all shapes and sizes. Red Rover’s creator, a company called Astrobotic, is partnered with two powerhouses: Carnegie Mellon University in Pittsburgh, Pennsylvania, and Raytheon, a defence contractor based in Waltham, Massachusetts. At the other end of the spectrum is FREDNET, a loose and far-flung collaboration of engineers and tinkerers working in their garages at
weekends. Team Selenokhod includes veterans of the Soviet Union’s Luna
programme, whose robots brought back lunar samples in the 1970s.
No matter what their pedigree, all
of the teams have their
work cut
out for them. First they will need to figure out where on the moon to land their rovers. As lunar water is believed to be concentrated at the poles, most of the competitors are focusing on these regions. Then there’s the question of how to land. C-Base Open Moon, a consortium of hackers based in Berlin, Germany, is proposing a hard landing cushioned only by air bags, inspired by the successful landings on Mars by the rovers Spirit and Opportunity. Other teams will opt for a soft landing using pulsed thrusters and impact-absorbing crushable honeycomb pads. Having arrived safely on the moon, the next task will be to navigate across its surface. The proposed methods reflect the teams’ diverse backgrounds. Astrobotic’s Red Rover is a wheeled design not fundamentally different from that used for NASA’s Mars rovers, except that it has four wheels rather than six. Its pyramidal body is covered in solar panels and crowned with a pair of camera sensors, making it look as though it has a small head with two eyes. C-Base Open Moon has come up with something less conventional: a two-wheeled contraption that calls to mind an 18th-century artillery piece. Tucked between its two massive wheels is an assortment of solar panels, cameras and other equipment. Some competitors are doing away with wheels altogether. Take the lander Talaris, for instance, the brainchild of the Next Giant Leap (NGL) consortium of Boulder, Colorado, which includes scientists from the Massachusetts Institute of Technology and the Charles Stark Draper Laboratory based close by in Cambridge. The lander will use pulsed thrusters to bound across the lunar surface in leaps of up to 5 kilometres. By abandoning the tried-and-tested technology of wheels and solar-powered motors, NGL hopes to have come up with a means of locomotion that could be used by landers on future missions to Marsor an asteroid. Whatever technologies are chosen for locomotion and for the lander’s sensors, they will have to contend with the moon’s
extremely harsh environment. The dust that covers the lunar surface is both sticky
and abrasive, and has been shown to cause a surprising amount of
damage. Another hazard is
Agony of choice
New Scientist3 2 N
the wildly varying temperature of the moon’s surface: at the equator it rises to 120 °C but plummets at night to -150 °C. Red Rover’s solar panels will face the sun at all times, not only to maximise the power they produce, but also to shade the vehicle from the direct heat of the sun. Gump says the company is fitting its moon buggy with components that can survive a complete shutdown during the two frigid weeks that constitute one lunar night. All this assumes, of course, that the contestants can find a way to get their lander to the moon without a launch vehicle of their own. The obvious option is to pay someone else to get it there. As well as established launch operators NASA, ESA and the Russian space agency Roscosmos, there are emerging private companies like SpaceX, which scored recent successes with its Falcon 9 rocket. Launch costs are typically at least $10,000 per kilogram, so hauling even a modest moon buggy of a few hundred kilograms could cost millions - enough to bankrupt at least half the teams. Pomerantz says his organisation has made a deal with SpaceX that it will waive any profit from launching GLXP missions. And for anyone prepared to launch from Florida soil, the state has agreed to add a further $2 million to any prize money they win. Several competitors, including Rocket City Space Pioneers, have discussed cooperating in a single launch, and then releasing their missions simultaneously. Wendell Mendell of NASA’s Lunar and Planetary Exploration Office says NASA, ESA or Roscosmos might even consider flying GLXP missions for free. Now wouldn’t that be an ironic start to the brave new world of privately funded space exploration.
Googles’ Moon
N
4 April 2011 3 3Googles’ Moon
Red Rover
Astrobotic’s creation has an
asymmetric shape so that all
the solar panels can face
the sun for maximum
exposure while the
large radiator
at the back of
the vehicle
remains
in
New Scientist3 4 N
Bria
n Co
xThe media-savvy British
physicist talks about his music
career, his TV work and why
the UK government should bet
big on science.
It’s big space, isn’t it?
It’s 93 million miles to the Sun: that’s a long way. It takes light eight minutes to do that. There are 100bn galaxies in the observable universe. If you take a 5p coin and hold it 75 feet away, the space in the sky it would obscure would hold 10,000 galaxies. It’s mindblowing. I don’t think anyone has a grasp of that other than to say: it’s big.
You recently answered claims that experiments with the Large Hadron Collider at CERN in Geneva might swallow the planet by saying: “Anyone who thinks the LHC will destroy the world is a twat.” Ever worry that you might have phrased that more delicately?
It’s not a comment, it’s a statement of fact, isn’t it? It’s factually accurate! It’s been everywhere, that. If you’re lucky you get one quote on your gravestone and that’ll be mine. It’s like with Bruce Forsyth: “Nice to see you, to see you nice.” I gave a talk in Florida the other week, and I walked on stage and said that and everyone was like: “Wahey!”
Should scientists be similarly robust when it comes to the arguments raging around climate change?
You mean swear more? I don’t know whether it’s because I’m from Oldham but I believe in a straight-talking version of science. There’s nothing mystical about it. We are too delicate with people who talk crap sometimes. But issues like climate change are difficult for scientists because they’re not politicians and there’s obviously a toxic confluence of agendas there.
Brian Cox
N
N
N
B
B
B
4 April 2011 3 5Brian Cox
Brian Cox
on his new
series ‘Wonders
of the Universe’.
“Anyone who thinks
the LHC will destroy
the world is a twat.”
New Scientist3 6 NBrian Cox
I don’t have a strong
view on religion, other
than illogical religion.
Young earth creationism,
for example: bollocks.
N
N
N
N
N
N
Brian at the
start of
‘Wonders
of the
Univesre’
4 April 2011 3 7
Where does your field of expertise lie?
I work in an area called diffraction. It’s interesting for lots of technical reasons.
What first inspired you?
I was born in March 1968 and my father says I watched the moon landings. I always knew I wanted to be an astronomer or someone who explored space or a physicist.
What about your career as a pop star?
I went to see Duran Duran with my sister in Leeds when I was about 15. The Seven and the Ragged Tiger tour. I thought: that looks brilliant, so I learned to play keyboards. I actually met Nick Rhodes recently… he just laughed. But it panned out perfectly.Joined my first band when I was 18, made a couple of albums, toured with Europe, supported Jimmy Page. Left that band and joined D:Ream. ‘97 was the last thing I did – the election.
You played “Things Can Only Get Better” at the Royal Festival Hall the night Labour won. What was that like?
The song had gone back into the charts so we did Top of the Pops that morning. Then we went to a hotel which Labour had got us, overlooking the Houses of Parliament. Sat there, watched all those classic moments. Portillo getting voted out! Then they rang and said: “We’ve won”, so we went and played. Robin Cook and everyone dancing…
You met Tony Blair at the time. Did he strike you as being all right?
Yeah. He still does. I bumped into him last year in Oxford and we had a brief chat. Blair’s government was good for science. Funding is having a blip now. It’s odd because it’s such a small amount of money [we’re talking about].
You’re called “the rock star physicist”. Do colleagues give you funny looks?
Careers don’t tend to be long in rock, and I left to do physics at the right time. My colleagues know I’ve been in bands, and I don’t just make TV programmes – I do try and use that platform to have arguments about science funding and so on, so I don’t think there’s much resentment. There can be, and it’s reasonable, because if you’re an academic and have a lot of admin to do… well, I’ve got out of that a bit. But if I’m off in Hawaii filming for the BBC, it doesn’t look great.
Brian Cox
In the first episode of your new TV series, we see you flicking through a book you had as a child called The Race Into Space. Does today’s world live up to the vision of the future you enjoyed then?
That’s a disappointing book when you look at it now! It says we were going to be on Mars by 1983. I met the head of exobiology at one of the big Nasa research institutes who knew the rocket pioneer Wernher von Braun from back in the early 60s. He told me they had a plan to go to Mars with the Saturn V rockets. If the programme hadn’t been cancelled in the late 70s, they could have done it.
Historically, we’ve often thought we’re getting close to cracking the secrets of the universe. Are we?
I honestly think the wheels are coming off our picture of the way the universe works at the moment. We don’t know what 96% of the universe is made of – that tells us that we don’t understand something fundamental. It reminds me of the start of the 20th century when quantum mechanics and relativity were about to appear.
We wouldn’t expect a dog to understand the mysteries of the universe, so why should we imagine that we can?
It’s an open question, whether it’s too complicated. All you can do is point back to history to note that we’ve been successful on this reductionist journey up to now. But there’s no reason…
Have you ever believed in God?
No! I was sent to Sunday school for a few weeks but I didn’t like getting up on Sunday mornings. But some of my friends are religious. I don’t have a strong view on religion, other than illogical religion. Young earth creationism, for example: bollocks.
You went to Alaska for your new series. What would you have said to Sarah Palin if you’d met her in a bar?
I would have started by asking: “Why do you think the Earth is only 6,000 years old?” I would have tried to convert her…
Interview by Caspar Llewellyn Smith
N
N
N
N
N
N
N
B
B
B
B
B
B
N
N
N
N
N
B
B
B
B
B
New Scientist3 8 N
Two planets found
sharing one orbit.
4 April 2011 3 9
Update on 5 March: Lead researcher Jack Lissauer says: “Further study of the light curve of this target produced an alternative interpretation wherein one of the co-orbital candidates (KOI 730.03) has a period that is twice what we originally estimated. We think that this new interpretation, without co-orbital candidates, is more likely to be correct. We will continue to acquire Kepler data andground-based observations ... so we can reach a better understanding of this interesting, multi-resonant, system.” Buried in the flood of data from the Kepler telescope is a planetary system unlike any seen before. Two of its apparent planets share the same orbit around their star. If the discovery is confirmed, it would bolster a theory that Earth once shared its orbit with a Mars-sized body that later crashed into it, resulting in the moon’s formation. The two planets are part of a four-planet system dubbed KOI-730. They circle their sun-like parent star every 9.8 days at exactly the same orbital distance. Gravitational “sweet spots” make this possible. When one body (such as a planet) orbits a much more massive body (a star), there are two Lagrange points along the planet’s orbit where a third body can orbit stably. These lie 60 degrees ahead of and 60 degrees behind the smaller object. For example, groups of asteroids called
Trojans lie at these points along Jupiter’s orbit. In theory, matter in a disc of material around a newborn star could coalesce into so-called “co-orbiting” planets, but no one had spotted evidence of this before. “Systems like this are not common, as this is the only one we have seen,” says Jack Lissauer of NASA’s Ames Research Center in Mountain View, California. Lissauer and colleagues describe the KOI-730 system in a paper submitted to the Astrophysical Journal (arxiv.org/abs/1102.0543). Richard Gott and Edward Belbruno at Princeton University say we may even have evidence of the phenomenon in our own cosmic backyard. The moon is thought to have formed about 50 million years after the birth of the solar system, from the debris of a collision between a Mars-sized body and Earth. Simulations suggest the impactor, dubbed Theia, must have come in at a low speed. According to Gott and Belbruno, this could only have happened if Theia had originated in a leading or trailing Lagrange point along Earth’s orbit. The new finds “show the kind of thing we imagined can happen”, Gott says. Will KOI-730’s co-orbiting planets collide to form a moon someday? “That would be spectacular,” says Gott. That may be so, but simulations by Bob Vanderbei at Princeton suggest the planets will continue to orbit in lockstep with each other for the next 2.22 million years at least. N
P l a n e t P l a n e t
New Scientist4 0 N
U n i v e r s e E x t r e m e s
4 April 2011 4 1
U n i v e r s e E x t r e m e s
New Scientist4 2 N
A journey towards the hottest climes of the cosmos must start by passing the sun, the fiery centre of our solar system. With a surface temperature of 5800 kelvin, our star is far from chilly, but it is no cosmic record breaker either. Blue supergiants, whose greater mass compresses their cores and stokes the nuclear fires within, run at more than 50,000 K. Even that is surpassed by some white dwarfs, compact spheres of heat left behind when a smallish star burns out. One such stellar cinder, called HD62166, measures a scorching 200,000 K and lights upa vast nebula with its painfully bright atmosphere. Plunging deep inside a star will take you to even more hellish realms. The largest supergiant stars may have core temperatures of more than a billion kelvin. For a stable star, the theoretical upper limit is about 6 billion kelvin. At this temperature, matter within the star starts to emit photons that are so dangerously energetic they can create pairs of electrons and positrons when they collide. The result is a runaway reaction that obliterates the star in a colossal explosion. The first suspected sighting of such a “pair-instability supernova” came in 2007, when a brilliant and exceptionally long-lasting stellar explosion was observed, suggesting the existence of a star far bigger than had previously been thought possible. During a supernova, stellar temperatures can briefly rise far above 6 billion kelvin. In 1987, a star was seen exploding in the Large Magellanic Cloud, a satellite galaxy of our own Milky Way some 160,000 light years away from us. Neutrinos from its heart detected on Earth
The
hottest
thing in the
universe.
revealed an internal temperature of about 200 billion kelvin. That’s nothing, though, compared with whatever produces a gamma-ray burst. These brief flashes of ultra-high-energy light are spotted once or twice a day by specially tuned telescopes. CRBs are thought to mark the birth of black holes, either when a giant star’s core collapses or when two ultra-dense neutron stars collide. Somehow the gravitational energy is turned into a tight beam of gamma rays and other radiation. While the details of this process are currently unknown, it must involve a fireball of relativistic particles heated to something in the region of a trillion kelvin (1012 K). Closer to home is a place that is even hotter: not a natural inferno, but a detector cavity 100 metres or so beneath the generally temperate outskirts of Geneva in Switzerland. There, between 8 November and 6 December 2010, nuclei of lead atoms were smashed together for the first time at CERN’s Large Hadron Collider in an attempt to mimic some of the universe’s opening moments. The result was the highest temperatures ever recorded on Earth, a subatomic fireball registering several trillion kelvin. That experiment gives us a clue to where the universe’s extreme of heat lies. Not in the here and now, but the way back when. Looking into the heart of the big bang, the singularity of temperature and density in which our universe began, the maximum temperature is just a matter of how many zeros you can write before our understanding of physics breaks down. That’s probably somewhere in the region of 32.
Universe Extremes
4 April 2011 4 3Universe Extremes
The
first
suspected
sighting of
such a “pair-
instability
supernova” came
in 2007, when a
brilliant and
exceptionally
long-lasting stellar
explosion was observed.
New Scientist4 4 N
The
coldest thing in the
universe.
Universe Extremes
A gas
cloud
called the
Boomerang
nebula, 5000
light years away,
has a temperature
of only 1 K.
4 April 2011 4 5
Space itself is neither hot nor cold. In the absence of stuff with thermal vibrations, temperature has no meaning. But there are plenty of cold things in space. In our solar system, the coldest known spot is quite close by. In 2009, NASA’s Lunar Reconnaissance Orbiter found permanently shadowed craters near the south pole of the moon that were at only 33 kelvin (-240 °C)-colder even than any temperature yet measured on dark and distant Pluto. As exploration continues and measurements improve, that record is likely to pass to some moon or dwarf planet much further from the sun, perhaps with its own sheltered and frigid craters. Beyond our solar system there are certain to be some even chillier rocks, and the coldest of all these lonely wanderers are likely to be found in intergalactic voids. Warmed only by the weak microwave afterglow of the big bang and a
Universe Extremes
glimmer of distant starlight, their temperature would be no more than 3 K. Since the 2.7 K microwave background bathes the entire universe, you might imagine that nothing could be colder than this. Not so. A gas cloud called the Boomerang nebula, 5000 light years away, has a temperature of only 1 K. The nebula is expanding rapidly, which actively cools its gas in the same way that expansion chills the coolant in a domestic refrigerator or aircon unit. Whether the Boomerang retains its status as the coldest known natural object remains to be seen, but this is one area in which humans have no trouble outdoing nature. In 2003, a cloud of sodium atoms in a lab at the Massachusetts Institute of Technology was chilled to 0.45 nanokelvin, less than half-a-billionth of a degree above absolute zero - far colder than any temperature the wider universe seems to have a use for.
New Scientist4 6 N
Speed is relative. There is no absolute standard for “stationary” in the universe. Perhaps the nearest thing is the all-pervasive cosmic microwave background radiation. Its Doppler shift across the sky - blue in one direction, red in the other - reveals that, relative to the CMB, the solar system is rattling along at 600 kilometres per second. Microwaves are rather insubstantial, though, so we don’t feel the wind in our hair. Distant galaxies are also moving at quite a rate. Space is expanding everywhere: the more space you are looking through the faster the galaxies you see are moving away from us. Far enough off, galaxies are effectively retreating faster than light speed, which means we can never see them because their radiation can’t reach us. While such inaccessible extremes may have abstract appeal, speed becomes much more interesting if you are moving fast relative to some large object nearby - something you can see whoosh past your windows, or something you might just crash into. Within our solar system, Mercury, the messenger of the gods, is the fastest-moving planet, with an orbital speed of about 48 kilometres per second; Earth manages only about 30 km/s. In 1976, Mercury was outpaced for the first time by a human artefact, the Helios 2 solar probe, which reached more than 70 km/s as it whizzed by the sun. Sun-grazing comets that swoop in from the outer solar system trump both, skimming past the solar surface at up to 600 km/s. Speed does not guarantee escape: a few hit the sun and are swallowed. The outer reaches of the Milky Way are also home to some oddly busy bodies: “hypervelocity stars” speeding past the rest of the galaxy at up to 850 km/s. The theory is that they were flung out
The
fastest thing in the
universe.
Universe Extremes
4 April 2011 4 7
in a close encounter with the giant black hole in our galaxy’s centre. Black holes make particularly effective cosmic slingshots because of their peerlessly powerful gravity. Some also create magnetic tornadoes that squirt out tenuous jets of matter at more than 99 per cent of the speed of light. The spinning neutron stars we know as pulsars also perform high-speed magnetic magic. Pulsars can rotate up to 1000 times a second, which means their surfaces move at up to 20 per cent of the speed of light. Far enough away from the surface, the magnetic field projected by the pulsar can even move faster than light. That is not in conflict with the laws of physics as the magnetic field carries no energy or information. These superfast fields are perhaps the source of the powerful, regular pulses of radiation pulsars send our way. Tiny variations in the timing of those pulses could soon be used to detect gravitational waves, travelling space warps predicted by Einstein’s relativity. Even solid objects can approach light speed, with the aid of a black hole’s gravity. At a hole’s event horizon, a single rock will simply disappear without a splash, but two rocks on different trajectories could collide with one another. According to calculations posted online last year by Tomohiro Harada at the University of Tokyo, Japan, and his colleague Masashi Kimura, the rotation of the black hole whips up a whirlpool in the surrounding space and increases the maximum collision speed. The upshot is that somewhere in the universe, two rocks caught in the grip of a rapidly spinning black hole could be hurtling towards one another at close to the speed of light.
Universe Extremes
The spinning neutron
stars we know as
pulsars also perform
high-speed magnetic
magic. Pulsars
can rotate up
to 1000
times a
second.
New Scientist4 8 N
R136a1
is a star
in the Large
Magellanic
Cloud that is
as bright as
almost 9 million suns.
4 April 2011 4 9
Everyday units are far too small to cope tidily with the brilliance of the cosmos. Instead, astronomers use the sun, and its dazzling light output of 4 × 1026 watts, as a standard lamp. The sun is in fact an above-average star in terms of brightness, but some stellar show-offs outshine it by far. The most luminous example clearly visible to the naked eye is Epsilon Orionis, the middle star of Orion’s Belt. This blue supergiant is 1300 light years away and 400,000 times as bright as the sun. Much further away within our galaxy, or obscured by dust, are yet brighter stars such as the unstable Eta Carinae, which pumps out as much light as 5 million suns. In July 2010, astronomers found a new record breaker. R136a1 is a star in the Large Magellanic Cloud that is as bright as almost 9 million suns. With a mass estimated to be 250 times that of the sun, this freakish body is heavier than anyone thought possible, at least for a star made from the kind of chemical mixture available in the gas of the Milky Way and its neighbours. Could it be built from an almost pure source of hydrogen
The
brightest thing in the
universe.and helium gas that had somehow survived uncontaminated since the early days of the universe, or is there something wrong with our theories of stellar structure? Some massive stars burn brighter still - but only for a few weeks and at the cost of their lives (see “What’s hot”). A supernova called SN 2005ap, in a galaxy 4.7 billion light years away, qualifies as the brightest stellar explosion on record, peaking at about 100 billion suns. Gamma-ray bursts emit even more energy than a supernova, and they can pack it into a matter of seconds rather than spreading it over several weeks. A burst can make even our solar unit seem absurdly feeble: its luminosity can equal more than 1018 suns. If such explosions seem unsatisfyingly transient, then the brightest steady lights in the universe are quasars, in which a massive black hole feeds on a copious supply of stars and gas. As this doomed material spirals inwards it becomes white hot, and it can shine with the light of more than thirty trillion suns.
Universe Extremes
New Scientist5 0 N
In medieval cosmology, the universe was a nested series of perfect crystal spheres that carried the sun, moon, planets and stars. We now know that space is rather messier, but does it hold anything to mirror that vision of spherical perfection? Planets themselves are pulled into fairly tidy spheroidal shapes by the force of their own gravity. The most prominent of Earth’s bumps and its deepest wrinkles, from mount Everest to the Mariana trench, point in or out by less than 0.2 per cent of the planet’s radius. If it weren’t for the slightly squashed shape caused by Earth’s daily rotation - pulled in at the poles, bulging at the midriff - our home would make a good cosmic pool ball. Earth is positively craggy compared with neutron stars. Their huge density (see “Heavyweight division”) results in a surface gravity something like 200 billion times as strong as Earth’s. That is enough to flatten out all but the slightest irregularity: a neutron star’s Everest would probably be no more than 5 millimetres high. As these stars are typically 10 to 15 kilometres across, that Himalayan height is less than one part in a million of the stellar radius. For a period of 16 months during 2004 and 2005, we launched our own balls into space that rivalled neutron stars for roundness. Gravity
The
roundest thing in the
universe.
Universe Extremes
4 April 2011 5 1
Probe B was a satellite designed to look for distortions in space-time created by our planet’s great mass, which are predicted by Einstein’s general theory of relativity. One of these is an effect called frame-dragging, in which space is dragged around with the rotation of the Earth. Gravity Probe B used four gyroscopes based on small spheres of quartz polished so thoroughly that they have no irregularities larger than 0.4 parts in a million. Relativity happens to offer us something rounder even than that probe’s spheres. A black hole’s event horizon marks the region from which no light can escape to reach the eye of a distant observer. It isn’t exactly a surface: you couldn’t run a hand over it and marvel at its new-shave smoothness. But soon astronomers may be able to discern images of some black hole event horizons and eventually give us a sharp picture of these pseudosurfaces which are perhaps the nearest thing in nature to perfect roundness. Observing matter falling in to an event horizon could be a sterner test of Einstein. If we see shreds of gas on orbits slightly different from the predictions of relativity, we may need a new theory of gravity. And of course if black holes turn out not to have the expected event horizon, that would be a shocker.
Universe Extremes
Earth is positively craggy
compared with neutron
stars. Their huge
density results in a
surface gravity
something like
200 billion
times as
strong as
Earth’s.
New Scientist5 2 N
segue 1
remained
undiscovered
until 2006
because its total
light emission
is only 300 times
that of our sun.
4 April 2011 5 3
Galaxies are supposed to be glittering jewels, studded with billions of bright stars and glowing nebulae. Not so Segue 1, the dark horse of the galactic neighbourhood. Segue 1 is only 75,000 light years away, making it a near neighbour of the Milky Way, yet it remained undiscovered until 2006 because its total light emission is only 300 times that of our sun. That is odd. Segue 1’s few stars are moving around quite fast, so its gravity must be reasonably strong, implying that it contains at least a million solar masses of matter. Very little of that can be accounted for by visible stars and gas, suggesting that almost all of it must be exotic dark matter. Studying dwarf galaxies like Segue 1 could tell us more about dark matter. For example, if the cores of these galaxies are less dense than predicted by the standard assumptions of how cold dark matter should behave, it could mean that the stuff is warm, or prone to self-destruct, or made from ultra-light particles that are inherently fuzzy. Even better would be finding a “dark star” - a cool, fat blob of gas gently warmed from within by decaying dark matter. Such beasts are thought to have existed in the very early universe, and there may still be a few around today, but none has yet been spotted. Meanwhile CERN’s Large Hadron Collider is being used to hunt for possible dark-matter particles, so perhaps the hottest thing on Earth will soon illuminate the dimmest thing in space.
The
darkest thing in the
universe.
Universe Extremes
New Scientist5 4 N
At the modest temperatures and pressures of Earth’s surface, the densest known material is the metallic element osmium, which packs 22 grams into 1 cubic centimetre, or more than 100 grams into a teaspoonful. Even osmium is full of fluff, however, in the form of electron clouds that separate the dense atomic nuclei. Although rarefied, these clouds are robust, and even the immense pressures deep within the planet can only compress solid matter to a modest degree. Far greater pressure is found within the collapsed core of a giant star, a remnant we know as a neutron star. There, matter is in some exotic and ultra-dense form - most probably neutrons, and possibly a few protons and electrons, packed cheek-by-jowl. One cubic metre of “neutronium” matter from the centre of a neutron star could have a mass of up to 1018 kilograms, or a million billion tonnes. An even denser hypothetical material may yet exist in the cores of neutron stars: quark matter, in which protons and neutrons dissolve into their constituent particles. The latest evidence is against it, though. Two newly discovered neutron stars are so heavy that they would probably squeeze a quark-matter core into oblivion. The clues to what really lies at the heart of a neutron star may come through studying starquakes, the juddering explosions of energy that happen when the crust of a neutron star ruptures. Neutronium, or perhaps quark matter, may be the densest form of matter in the cosmos, but it is probably not what the densest object is made of. Compress a neutron star even further, and it will turn into a black hole. Not that all black holes are particularly dense: in fact the big ones, as measured by their event horizons, are quite tenuous. A supermassive black hole in the nearby
galaxy M87 has a mass 6.4 billion times that of our sun but a density of only 0.37 kilograms per cubic metre, making it lighter than air. On the other hand, the smallest known black hole - a minnow called XTE J1650-500 - is only 3.8 times the mass of the sun, but its density is just over 1018 kilograms per cubic metre. Find one of these warps in space-time that is just a little smaller, and it will overtake neutronium in the density stakes. Microscopic black holes might also have been forged during the big bang, when quantum fluctuations in a hugely dense universe could have led to regions so dense that they collapsed. Such micro-holes might yet reveal themselves in sudden bursts of radiation: if so, this could give us an insight into the scale of quantum fluctuations in the nascent universe, and perhaps what processes actually drove the big bang. Inside a black hole’s event horizon things get even stranger. The theory of relativity tells us that all that mass is squeezed down to a mathematical point of infinite density - though the theory almost certainly breaks down at such extremes as quantum effects begin to scramble space-time. Here, where gravity meets the quantum world, is the great frontier of fundamental physics. It is by considering such extremes as black-hole singularities that theoreticians hope to understand the most profound basis of reality. Does a black hole’s heart conceal a fuzz-ball of wobbling strings? Or a space-sucking quantum wormhole? We don’t know, although back-of-the-envelope calculations suggest an upper limit on its density of 5 × 1096 kilograms per cubic metre, called the Planck density. The densest thing in the universe can probably be no denser than that - whatever it actually is.
The
densest thing in the
universe.
N
Universe Extremes
4 April 2011 5 5
Microscopic black
holes might also
have been
forged during
the big
bang.
New Scientist5 6 N
It has long been assumed that these most massive of galaxies form when two smaller spiral-shaped galaxies collide. But there is an alternative theory in which a cloud of gas collapses in on itself to form a dense core of stars which then grows larger by assimilating smaller galaxies over time. This is similar to how ice crystals build up around a microscopic dust grain as it falls to Earth, forming a snowflake. Now there is evidence that a massive elliptical galaxy called NGC 1407 formed in this way. Duncan Forbes of Swinburne University of Technology in Hawthorn, Victoria, Australia, and colleagues used the colours of the star clusters in NGC 1407 to estimate its chemical composition. They found the concentration of heavy elements was highest at the core’s centre, decreasing towards its edges, which tallies with the gas cloud collapse theory. That’s because the gravity at the cloud’s centre would be stronger than at its edges, concentrating the heavy elements produced in stars there. N
S n o w f l a k e G a l a x i e s
4 April 2011 5 7
S n o w f l a k e G a l a x i e s
They may be monsters of
the universe, but elliptical
galaxies can start life in the
same way as snowflakes.
New Scientist5 8 N
On Friday, NASA’s Messenger spacecraft is set to become the first probe to go into orbit around Mercury. The planned year-long mission could reveal why the sun-baked planet is the densest in the solar system and whether it harbours any ice in darkened craters at its poles.
Messenger launched in 2004 and flew past Mercury three times as it followed a looping path designed to bring it into orbit around the planet. Before that, only one other spacecraft had visited Mercury – NASA’s Mariner 10probe, which flew past the rocky world three times in 1974 and 1975. “Mercury has been comparatively unexplored, considering its proximity in our solar system,” principal investigator Sean Solomon of the Carnegie Institution of Washington in DC said at a new briefing on Tuesday. That is set to change on Friday, when Messenger will burn its thrusters for about 15 minutes, beginning at 0045 GMT, to slow it down enough to be captured into orbit by the planet’s gravity. The manoeuvre will use up about a third of the fuel the probe carried when it launched. It is designed to go into an elongated, 12-hour orbit that passes within 200 kilometres of Mercury’s surface at its closest point and 15,000 km at its farthest.
Even if all goes as planned, it will not send any images back to Earth immediately, as its instruments will remain off for about a week. “It’s in the interest of the spacecraft health and reduction of risk,” Solomon said. He said that even though the probe has been as
On Friday, NANA’s Messenger spacecraft
is set to become the first probe to go into
orbit around Mercury. The planned year-
longmission could reveal why the sun-
baked planet is the densest in the solar
system and whether it harbours any ice in
darkened craters at its poles.
Artif
icia
l Sa
tell
iteNafety first
4 April 2011 5 9
The probe will
begin regular
observations
of the
planet on
4 April.
New Scientist6 0 N
close to the sun as it will be then, it has never been in orbit around the planet and subjected to the heat radiated by its surface. The first image taken from orbit will be released on 29 March, according to the mission team. The probe will begin regular observations of the planet on 4 April, when it will use seven instruments to study the composition of the planet’s surface, measure its topology and record the planet’s magnetic field. Studies of the composition of the surface could help reveal why Mercury is denser than any other planet in the solar system, with an enormous two-thirds of its mass made up of its metal core. Three theories compete to explain this phenomenon. Denser, metal-rich planetary building blocks may have been drawn closer to the sun before the planet formed. Or the sun might have vaporised part of the planet’s rocky exterior, early on in its life. Or, as many scientists suspect, an impact with a similar-sized object blasted away the planet’s outer layers. Each scenario would have left behind a unique
combination of surface rocks. “We can test the ideas with chemical remote sensing,” said Solomon, though he says it is likely that a number of different processes may have contributed to the planet’s high density. Because the probe will follow an orbit that takes it very close to the planet’s north pole, it will try to determine if any craters there host ice – as ground-based radar observations suggest. Using cameras and a laser altimeter, the probe will measure the topography of the craters, determining the depth of their floors, the height of their rims and whether they are permanently in shadow – thought to be a key requirement for ice to survive on a planet whose sunlit side is hot enough to melt lead. It will also use its instruments to look for signs of the ice boiling off.
Giant impact
N
4 April 2011 6 1
New Scientist6 2 N
4 April 2011 6 3
New Scientist6 4 N
Mention meteors, and casual skywatchers usually think of the annual Perseid shower on display every August.
But the Geminid meteor shower of mid-December ties or even surpasses the Perseids as the year’s richest and most reliable meteor display. Geminid meteors come from 3200 Phaethon, an asteroid discovered in 1983. This year the Geminids are predicted to peak on Tuesday morning around 1100 GMT, more or less. That’s excellent timing for North America, especially out west. The moon that night is only a day past first quarter and sets around midnight or 1 am local time, depending on where you live. Even before then, on Monday evening, the moonlight isn’t bright enough to dampen the shower’s visibility too much – and the Geminids, with their radiant [apparent origin] near the stars Castor and Pollux, pick up steam as early as 8 or 9 pm. But the radiant is highest around 2 am, so the morning hours are the usually the most productive. Bundle up as warmly as you possibly can, and lie back in a dark spot with an open sky. You may see as many as two meteors a minute on average if you have a very dark sky and are watching after midnight. If your sky is not too light-polluted, you might try making a careful meteor count and reporting it to the International Meteor Organization. Such counts by amateurs supply much of what we know about meteor showers’ behaviour. For your count to be useful, you’ll need to follow the procedures described here or at the IMO’s website. Don’t forget that the shower lasts more than one night. Counts are especially needed on nights away from the maximum, because fewer people are watching. In any case, enjoy the show!
Mention meteors, and casual
skywatchers usually think of the
annual Perseid shower on display
every August.
N
4 April 2011 6 5
G e m i n i d M e t e o r s
New Scientist6 6 N
4 April 2011 6 7
New Scientist6 8 N
S a v e 2 0 %S u b s c r i b e t o d a y
Subscribe to New Scientist for a stimulating mix of science and technology
Recieve New Scientist magazine every week, plus full online access to www.newscientist.com including our 15 year online archive.
Push your mind to its limits with:
New innovations and ideas - Keep up to date with the advances that are set to transform the world around us.
Scientific discoveries - Explore the latest topics that interest you. Read exclusive interviews with pioneers of scientific development.
The last word - The most baffling questions in science answered. Guaranteed to feed your inquisitive mind.
Subscribe today and save 20%, this offer must end 30th April 2011.
c a l l t h e h o t l i n e o n+44 (0) 8456 731 731 and quote 5058or visit www.newscientist.com/s/5058
N N E W S C I E N T I S T
4 April 2011 6 9
N E X T W E E K S I S S U E
N N E W S C I E N T I S T11 April 2011www.newscientist.com issue 02
M i l k M i l e s
P l a n t W a v e s
U n n a t u r a l S e l e c t i o n
D e a d l y W e a t h e r
E v o l u t i o n a r y P u s h
New Scientist7 0 N
