astro 113 week13 - GMU College of Science

© Dr. Joseph E. Pesce, Ph.D.

Astronomy 113Dr. Joseph E. Pesce, Ph.D.

The Fate of the Universe


Expand or CollapseUniverse is expanding:

³If average density of matter is low, universe will expand forever. Universe is UNBOUND²If density is just at the critical density, universe is

unbound too and will expand forever, but at an ever-decreasing rate **

³If there is enough matter, gravity can stop expansion and it will collapse. Universe is BOUND

** where we were before dark energy

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Shape of Universe1. Space is spherical,

positive curvature

2. Space is hyperbolic, negative curvature

3. Space is flat, no curvature

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Unbound, OPEN

Unbound, OPEN

Bound, CLOSED


Dark Energy³Observations of Type 1 Supernova in mid-90s

²At about 1 billion light years²Objects were fainter than should be²Tested all known possibilities

q Dustq Type of supernovaq Etc.

Why might an object be fainter than expected if it is not naturally fainter?

18-4


Dark Energy³Universe is expanding faster than expected

²Starting about 1 billion years ago

³Something is causing expansion to accelerate

³What is it?????!!!! ²Related to what caused inflation right after Big Bang

³Most of mass/energy is dark energy

18-5


The Universe18-6


Energy Budget of Universe18-7


Fate of Earth³Sun will expands in about a billion years and

engulfs Mercury and Venus³Loses mass, so Earth’s orbit increases

²But atmosphere probably boils off³About 1 billion years from now, Milky Way will

collide with the Andromeda Galaxy³Sun becomes planetary nebula about 5

billions years from now²If Earth survived, it will no longer have an

atmosphere and will become very cold

18-8


Fate of Universe³Expands forever³By about 1 billion years, only a few galaxies

close enough for us to see³Then atoms/molecules in ISM too far apart to

collapse into stars³After trillions of years, M-stars die³More trillions of years: atomic nuclei ripped

apart³Universe becomes cold and dark

18-9


Our Place in the Universe &

Life in the Universe


© 2007-2014 Joseph E. Pesce, Ph.D.

Our Place in the Universe

& Life in the Universe


³The sun with a retinue of 9 (?) planets, and many moons, asteroids, etc.²An infinitesimal speck within our galaxy

which is itself an infinitesimal speck

²We are not in any preferred position

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19-4



Our galaxy, the Milky way, contains 100 billion stars and is one of ~100 billion galaxies (10,000 billion billion stars)

The Solar System

100,000 ly

19-5


Life in the Universe³Lots of planets³Organic molecules and amino acids

everywhere³Life on earth in most �inhospitable� places³Earth life may have been �seeded�³So probably lots of low forms of life

everywhere³But what about intelligent life?

²Why haven’t we seen evidence?

19-6


Communicating with Aliens

³How?

³Message in a bottle?

²Done 4 times – very low probability

³Send message

²Directed and unintentional

³Receiving

²Project SETI

19-7


Interstellar Travel³Really really really difficult!!³Visitation, invasion, abductions by aliens

highly unlikely

19-8


Thank You!


astro 113 week13 - GMU College of Science

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