Eternity

From

Here to Eternity Lee Angelina Ka Yan Wong Ka Wing

Outline  Runaway  Balance  Red

in Sun

Giant

 Death 1 March, 2008

Moist Greenhouse

throes From Here to Eternity

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Runaway Moist Greenhouse  Huge

amount of CO2 is being released

 Temperature

increases  H2O vaporized  Water

vapor is a powerful greenhouse gas  Temperature increases further  More H2O vaporized  Process 1 March, 2008

goes on until the oceans boil dry From Here to Eternity

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Runaway Moist Greenhouse  Too

hot for water vapor to condense in troposphere (lowest layer of atmosphere)  Water vapor goes up to reach stratosphere (where the ozone layer is)  Water vapor is subject to photolysis γ H 2O( g )  → 2H ( g ) + O ( g )

 Hydrogen 1 March, 2008

atoms produced From Here to Eternity

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Runaway Moist Greenhouse  Escape

velocity for Earth is vescape

2GM E = RE

The numerical value is 11.2 km s-1  The distribution of hydrogen atoms is 3 2

mv 2 − 2 2 kT

 m  N ( v ) = 4πN 0   ve  2πkT  1 March, 2008

From Here to Eternity

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Runaway Moist Greenhouse  Portion

of hydrogen escape from Earth is N  m  = 4π   N0  2πkT 

3 2

∫

∞

mv 2 − 2 2 kT

ve

vescape

dv

The numerical value for 673 K is 0.0055%  All hydrogen escape in 1.8 billion years  Earth will lost all the water

1 March, 2008

From Here to Eternity

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Balance in Sun  For

the time being, Sun exists in a stable, settled balance state  Slight contraction of the Sun increases its central density  Temperature increases and speed up the nuclear fusion reactions  Extra heat make the Sun expand back out 1 March, 2008

From Here to Eternity

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Balance in Sun  Slight

expansion cools the interior  The nuclear fusion reactions slow down  Slowing energy production makes the Sun to re-contract  The Sun is in stable, settled balance state for 90% of its life time

1 March, 2008

From Here to Eternity

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Red Giant  Most

of the hydrogen gas in the core of the Sun undergoes fusion  The core becomes mostly helium and is surrounded by hydrogen layers  Energy production rate decreases  The core contracts due to gravity

1 March, 2008

From Here to Eternity

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Red Giant  The

gas in the core is compressed  Temperature of the core increases  Ignite the nuclear fusion of hydrogen gas in the shell just outside the core  Hydrogen-burning shell pushes the outer layer outward  Rapid expansion of the Sun causes it to become more luminous 1 March, 2008

From Here to Eternity

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Red Giant  The

Sun will swell to more than 200 times its current size  Luminosity is L = 4πR 2σT 4

The Sun becomes more luminous

1 March, 2008

From Here to Eternity

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Red Giant  The

Sun begins to blow off a strong wind that carry a quarter of the solar mass  The Sun loses a quarter of gravitation pull  Orbits of planets expand outward 1 March, 2008

From Here to Eternity

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Red Giant  Tides

act on the Sun due to the planets  Self-rotation of Sun is slower than the orbital motion of Earth  The Sun will track the position of the Earth in orbit

1 March, 2008

From Here to Eternity

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Red Giant  Tides

act on the Sun due to the planets  Self-rotation of Sun is slower than the orbital motion of Earth  The Sun will track the position of the Earth in orbit

1 March, 2008

From Here to Eternity

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1 March, 2008

From Here to Eternity

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1 March, 2008

From Here to Eternity

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1 March, 2008

From Here to Eternity

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Death Throes  Sun

becomes a red giant for a second time  Sun will throw off its massive outer layers completely to form a planetary nebula

1 March, 2008

From Here to Eternity

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Death Throes  Sun

becomes a tiny white dwarf  Jupiter and Saturn are too massive to interact with the solar system gravitationally in a serious way  Our solar system becomes chaotic system  Objects would be colliding, being flung away to interstellar space, or falling onto the Sun 1 March, 2008

From Here to Eternity

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Death Throes  If

Earth survived, it would orbit the white dwarf quietly and stably  Sun would cool closed to absolute zero  At this time, the Milky Way would have already merged with the Andromeda Galaxy to form a large elliptical galaxy

1 March, 2008

From Here to Eternity

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Death Throes A

random white-dwarf remnant to pass close enough to tear Earth from its orbit and send it loose into the now-dark galaxy  If Earth can avoid collision with central black hole, passing stellar remnants would fling it out of the galaxy completely  Cosmic expansion carry the galaxy away  Earth would become utterly alone 1 March, 2008

From Here to Eternity

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