Question

The theory which resolves both the horizon and flatness problems is called:

A) DecouplingB) RelativityC) InflationD) Big Bang

Question

The main difference between a “normal” galaxy and an active one is:

A) fuel supplyB) active galxies have a black hole at the center, but “normal”galaxies don'tC) “normal” galaxies can only be EllipticalD) an active galaxy is a Quasar

QuestionWe know that all the Galaxies must have been at one point in the distant past because ___________.

A) all observations of distant galaxies show that they are moving away from us with a velocity proportional it their distance from usB) the Universe is flatC) local galaxies are sometimes moving towards us and sometimes moving away from usD) space-time can travel faster than the speed of light

Extraterrestrial Life (as We Know It)

“Life as we know it” is generally taken to mean carbon-based life that originated in a liquid-water environment.

Requirements?

Extraterrestrial Life (as We Know It)

“Life as we know it” is generally taken to mean carbon-based life that originated in a liquid-water environment.

Requirements?Liquid water, protection from radiation, temperate climate

What are some important characteristics of living organisms?

Characteristics of a Living Organism

Reacting to environmental stimuli

Taking in nourishment and growth/healing

Reproducing and passing on characteristics

Genetic changes (mutations/evolution)

Extraterrestrial Life

Assumptions of mediocrity:

Life on Earth depends on just a few basic molecules.

Elements are common to all stars.

Laws of physics the same everywhere => life fairly common in the cosmos.

The Miller-Urey experiment attempts to recreate the chemical conditions of the primitive Earth in the lab, and synthesize building blocks of life.

ET Life in the Solar System?

Besides the Earth, which bodies in our solar system are most likely to harbor life?

The Moon and Mercury lack liquid water, protective atmospheres, and magnetic fields.

Venus has far too much atmosphere.

Planet most likely to harbor life

Mars, but No Liquid water Atmosphere is thin Lack of magnetism and ozone layer

Jovian moons Titan and Europa!

The Drake Equation

number of technological, intelligent civilizations in the Milky Way

rate at which new stars are formed (avg. over galactic lifetime)

= x

fraction of stars having planetary systems

x

average number of habitable planets within those planetary systems

xfraction of those habitable planets on which life arises

xfraction of those life-bearing planets on which intelligence evolves

fraction of those planets with intelligent life that develop technological society

average lifetime of a technological civilization

xx

Each term is less certain than the preceding one! Only in last ten years have we addressed the second term.

Contact?

How might we go about trying to determine whether or not technologically advanced civilizations exist in our galaxy?

SETI Search for ExtraTerrestrial Intelligence

- Listens for radio signals from alien worlds

Clear window on the cosmos? - Electromagnetic spectrum, as viewed from Earth, is a noisy place

Microwave Window - in radio part of EM spectrum - Photons travel relatively unhindered through the interstellar medium, at the speed of light

- Natural noise is at a minimum

The Water Hole

Barney Oliver dubbed the spectral region between H and OH the Cosmic Water-Hole.

"Where shall we meet our neighbors?" he asked. "At the water-hole, where species have always gathered."

The Water Hole