Goal: To understand the fate of the most relevant things to us in the

universe.• Objectives:• 1) To learn about the end of Life on Earth• 2) To learn about the future fate of Earth• 3) To learn about the fate of Our galaxy• 4) To learn about the fate of The Local

Group• 5) To learn about The end of stars• 6) To learn about The end of matter

End of Life on Earth

• We will ignore the possibility that mankind destroys itself in a way that kills everything on the earth.

• We will also ignore the possibility that some really large object or other unpredictable astronomical even destroys all life.

• So, we are just looking at life on earth in general assuming that nothing unplanned happens.

The sun gets brighter

• Slowly over time the sun gets brighter.

• The sun is 30% brighter now than it was 4 billion years ago.

• Eventually this will become a problem for life on Earth.

• Once the temperatures on Earth get over 140 degrees life will perish.

Mitochondrial DNA

• Mitochondrial DNA needs to split for there to be reproduction.

• However Mitochondrial DNA won’t split for temperatures > 140 degrees F.

• So, once temperatures get above that (due to a brighter sun) then you cannot have reproduction. You might still have life surviving for a time, but if it cannot reproduce it is doomed to extinction.

• However, it will be 1-2 billion years before this can happen.

Other issues

• The other issues involve water.• The first is that water is slowly leaving

Earth. • A very small amount gets to the upper

atmosphere where it is broken down by solar UV rays into Hydrogen and Oxygen.

• They Hydrogen then escapes.• In 2 billion years the earth will loose its

water.

Last issue

• If the Earth were to warm up too much the water vapor content would increase.

• Water vapor is a greenhouse gas (the most prevalent) and a 3 C rise in temperature gives a 20% rise in water vapor levels.

• This heats the earth more.• At some point the oceans would release the Carbon

Dioxide that they carry and the earth would experience a “runaway” greenhouse effect and become as hot as Venus.

• Assuming we don’t do it to ourselves it will take about 1-2 billion years for this to happen.

For last 3 billion years of Earth’s life

• Earth will be a lifeless planet.• Eventually the sun will turn into a red giant (5

billion years from now).• The earth will be baked and the surface will be

melted (temperatures will increase by a factor of 30!).

• The sun will grow 100 million miles in radius.• The earth may or may not be eaten by the sun

(depending on how much mass the sun looses the earth may be able to get far enough away to survive).

6 billion years from now

• The sun will shed its outer layers and become a white dwarf the with time cools to a black dwarf.

• If the earth did not get eaten then the earth might actually escape from the sun (if the sun looses enough mass) or the earth will just go into a higher orbit.

• Either way the earth will now freeze and stay frozen until its final end.

Our galaxy

• Our galaxy – as we know it – probably has a much shorter time to live than our planet.

• In 2-3 billion years our galaxy will probably collide and then merge with Andromeda.

• The merger time may take a billion years, or if Andromeda just grazes us we may all do another pass.

• When the merger is finished there will be a new galaxy (begin naming contest now! And please don’t let us astronomers call it the Andromeda Way galaxy…).

• This won’t affect us though.

Our Local Group

• Our local group is speeding towards the Virgo cluster at 600 km/s (or 0.005 light years/year).

• Since Virgo is 50 million light years away our Local Group will merge with the Virgo cluster in about 25 billion years (give or take 5 billion).

• So, in 20-25 billion years we will be in the Virgo Cluster – thus ending our Local Group.

End of stars

• Eventually all of the dust and gas in our universe will be used up.

• Once this happens you can no longer make stars.

• This will take 100 trillion years – after which the only main sequence stars in existence will be brown dwarfs.

In 100 trillion years

• All that will be left:

• Black Holes

• Neutron Stars (Quark Stars)

• White Dwarfs

• Planets/moons ect

• Brown Dwarfs

1 quadrillion years

• In 1 quadrillion years all the planets will have been stripped from what remains of the dead stars (white dwarfs, ect).

• This will be done very slowly over time via gravitational perturbations of passing objects.

• The planets will here forth wonder alone in the heavens until the end of their days.

1019 years

• Because of gravitational interactions of passing stars in this time span most of the stars of every galaxy are expected to be tossed out of their galaxies.

• Note this is 10 million trillions or 10 quintillion years.

• In 100 quintillion years whatever has not escaped falls into the central black hole due to gravitational radiation – so galaxies are no more.

1036 years

• This is 1000 decitillion years.

• This is the estimated half life of a proton.

• So, after this it is expected that half of the protons in the universe will have decayed!

• All of the protons decay by 1040 years.

• After that the only things left are photons and black holes!

• This is the ultimate fate of the earth.

Black Holes

• As was mentioned, the space just above the black hole can radiate Hawking Radiation.

• When the temperature of the universe falls to extremely low levels then the black hole can loose energy.

• The smallest black holes die first (at about 1040 to 10100 years from now), but the giant ones in the cores of galaxies can last for 10150 years!

Photon age

• The entire universe is now photons.• These photons will get lower and lower in energy

with time as the universe expands (and at an ever increasing rate).

• At this point the universe is at its lowest energy level and any life that survived the rest could not survive anymore (no energy to tap into).

• And the universe just dies…• We have no idea what will happen to space or

time after this point.

Big Rip

• Since the expansion of the universe will continue to accelerate that means that clusters of galaxies will get smaller (tougher to keep them together).

• If the acceleration is fairly constant there is not much of an affect on the outcome of the universe.

• However, if that acceleration increases it is possible to have a Big Rip.

What is a Big Rip

• A Big Rip is the universe being pulled apart (even the atoms) by the expansion of the universe.

• First clusters would fling apart, then galaxies, then stars and planets, ect.

• Furthermore this would mean that the observable universe would shrink greatly with time.

How long do we have?

• Well, the soonest is 20 billion years from now although it is likely to be much further away than that.

Conclusion

• Nothing is forever, not even our galaxy.

• Everything has an end it seems – perhaps even our universe itself.

• However that all a very long time away.

• The greater concern is that we don’t wipe ourselves out in the next 100-200 years so that we can actually worry about this events billions of years in the future.