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NASA National Aeronautics and Space
Administration Pioneer and Voyager craft
Sent off on missions to transmit images of Jupiter, Saturn, and outer solar system
No communication from Pioneer craft anymore
Eventually it will be the same for Voyager craft Voyager 1 is the most distant human-made object
in spaceStill transmits data! :o
not only transmission of data, also have plaques detailing a man and woman, the solar system, and other information showing where Earth is locatedEach Voyager probe also has a “golden record” with recorded sounds and pictures of Earth
Each of the Pioneer space probes that have left the solar system carries the plaque from the previous slide.
It’s hoped that other planetary life forms that think enough like humans might find one of the probes and be able to use the plaque information, even millions of years from now, to locate Earth.
We are going to think about the implication of sending information about humans into space.
With your partner(s), discuss the following questions. Record your thoughts in point form. What does our sending information like this out
into space suggest about our own ideas of the universe?
What does the plaque information assume about the nature of any aliens who might acquire it?
If you were to design your own plaque, what would you like to put on it? Why?
If the plaque can last a million years, will it outlive the human race? Explain your answer.
Would aliens capable of finding the plaque already know about Earth because of our radio transmissions?
Is the most likely finder of the plaque going to be future human space travellers who have forgotten their early roots? Explain your answer.
Our ancestors used astronomical phenomena to: Mark the passage of time Foretell the changing seasons Indicate direction during travels
Aztecs and Mayans developed accurate calendars over generations of observation and recording
During the Renaissance (15thc.) relied heavily on knowledge gathered by Islamic astronomers for more than 800 years
Two important annual events for our ancestors: Summer solstice (northern hemisphere)
Near June 21 start of summer Longest day of the year
Winter solstice (northern hemisphere) Near December 21 start of winter Shortest day of the year
Solstices are opposite in southern hemisphere
Stonehenge was used to mark summer and winter solstices 4500 years ago Ancient African cultures also used this
method
It means a day when the hours of daylight and hours of night are of equal length. Vernal/spring equinox
Around March 21 Autumnal/autumn equinox
Around September 21 Mayans built towers (1000CE) to celebrate these
Egyptians built pyramids and monuments to align with the seasonal position of certain stars
First Nations used large rocks to build medicine wheels Key rocks were aligned with bright stars that rose
at dawn (Aledebaran, Rigel, Sirius) Also used to predict right time of year to
plant/harvest crops or prepare for hunting and fishing
Geocentric Model2000+ yrs ago, Earth
was believed to be the centre of the universe
Using Plato’s work, Aristotle first described the earth-centred (geocentric) model
Stars didn’t move? They were attached to the outside sphere
Geocentric motionPtolemy helped many
astronomical phenomena to be forecasted (moon phases)
Retrograde motion: apparent reversal o the planets’ path relative to the starry backdrop
Heliocentric model Improvements in
technology changed thinking
Proposed by Greeks in 500 BCE
Polish astronomer Nicholas Copernicus revived the idea
Sun is at the centre of our universe (Sun-centred) and planets orbited around SUN
Two key things about planetary orbit helped support the heliocentric (sun-centred) model1. Orbital radius
A planet’s distance from the Sun The shorter this is, the faster the planet moves in its orbit
Because of the Sun’s gravity being stronger when you’re closer to it
Earth is moving faster than Mars, Mars is faster thanJupiter
100 yrs later, more solid evidence was brought on by the invention of the telescope (binoculars) Galileo Galilei
Two key things about planetary orbit helped support the heliocentric (sun-centred) model1. Elliptical orbits
This model could not predict planetary motion very accurately, just like the geocentric model
Kepler figured it out Using much of the observations from his teacher,
Tycho Brahe, found that the planets were ELLIPSES, NOT CIRCLES
Everyone supports this idea now, and we use it to study other star-and-planet systems
1. In the northern hemisphere, what is the:(a) summer solstice and when is it?(b) winter solstice and when is it?
2. What is the main difference between the geocentric model and then heliocentric model?
3. Define retrograde motion and make a sketch to support the definition.
4. The orbits of the planets are not exactly circular. What shape are they?
Sundials Used for more than 7000 years to measure
time Quadrant
Measures the stars’ height above the horizon
AstrolabeMakes accurate charts of star positions
Cross-staffLevi ben Gerson invented this to measure
the angle between the moon and any given star
Telescope was invented in the late 16th cent. Refracting telescope
Two lenses gather and focus starlight Has a size limit (1m diameter) glass warps
Reflecting telescope Uses mirrors instead of lenses to collect visible
light Often located high on mountaintops to get the
clearest view Hubble Space telescope is one of these Space-based is better than ground-based
because they escape light and air pollution, weather,
Use radio waves emitted by objects in spaceLess affected by weather, can detect during day
and nightRadio waves not distorted by clouds, pollution,
or atmosphere like light wavesThese telescopes helped establish the BBT by
detecting CBR (microwave radiation leftovers)Also detected enormously powerful energy
sources at the edge of the visible universe Called quasars
Put out as much energy as a WHOLE GALAXY, but may not be larger than a solar system
Don’t know too much about them yet – but we’re working on it