The end of the world.

AnarkiThreeXSix

<a href="http://www.exitmundi.nl/" target="_blank">Exit Mundi</a>

This thread reminds me of that site.. A Collection of End-Of-World Scenarios. Fun times. <img src="style_emoticons/<#EMO_DIR#>/biggrin-fix.gif" style="vertical-align:middle" emoid=":D" border="0" alt="biggrin-fix.gif" />

lolfighter

<!--quoteo(post=1613340:date=Mar 10 2007, 09:03 PM:name=Gwahir)--><div class='quotetop'>QUOTE(Gwahir @ Mar 10 2007, 09:03 PM) [snapback]1613340[/snapback]</div><div class='quotemain'><!--quotec-->
a large solar flare will destroy Earth's magnetic field and normal solar radiation will kill all life on the planet. Except certain backteria like the kind that grows on nuclear reactor rods.
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That's not the end of the earth at all. That'll just make the surface nice and crispy.

Drfuzzy

Humans will kill themselves, dont be silly.

Rob

Somebody invent the Dr. Device from Ender's Game. That'll fix us. Not at all ironic, though.

Thaldarin

Hm actually what world were you referring to? The end of the world... of warcraft perhaps?

AnarkiThreeXSix

<!--quoteo(post=1613764:date=Mar 12 2007, 07:30 AM:name=Thaldarin)--><div class='quotetop'>QUOTE(Thaldarin @ Mar 12 2007, 07:30 AM) [snapback]1613764[/snapback]</div><div class='quotemain'><!--quotec-->
Hm actually what world were you referring to? The end of the world... of warcraft perhaps?
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We can only hope.

a_civilian

<!--quoteo(post=1613363:date=Mar 10 2007, 05:03 PM:name=AnarkiThreeXSix)--><div class='quotetop'>QUOTE(AnarkiThreeXSix @ Mar 10 2007, 05:03 PM) [snapback]1613363[/snapback]</div><div class='quotemain'><!--quotec-->
<a href="http://www.exitmundi.nl/" target="_blank">Exit Mundi</a>

This thread reminds me of that site.. A Collection of End-Of-World Scenarios. Fun times. <img src="style_emoticons/<#EMO_DIR#>/biggrin-fix.gif" style="vertical-align:middle" emoid=":D" border="0" alt="biggrin-fix.gif" />
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Another fun site: <a href="http://qntm.org/destroy" target="_blank">How to destroy the Earth</a>

Bloo

Don't be silly. We all know that all humans will die in the great apocalypse. except <a href="http://en.wikipedia.org/wiki/Jehovah's_Witnesses" target="_blank">Jehovah's Witnesses</a>. Which will remain to repopulate the earth which the apocalypse destroyed.

Moving_Target0

Religious view: See Revelations in the bible, or consult your nearest holy book / scripture.

Scientific view: We get hit by a celestial body, or the sun collapses upon itself and turns into a black hole.

a_civilian

The sun is not sufficiently massive to form a black hole. It does not exceed the <a href="http://en.wikipedia.org/wiki/Chandrasekhar_limit" target="_blank">Chandrasekhar limit</a> even at its present mass (let alone at its mass after it <a href="http://en.wikipedia.org/wiki/Planetary_nebula#Origins" target="_blank">throws off most of its matter</a>) and cannot collapse past electron degenerate matter.

Also, even if it did collapse to a black hole, there is no reason to believe that would destroy the earth; the earth would simply be orbiting a black hole.

Moving_Target0

<!--quoteo(post=1614384:date=Mar 14 2007, 09:57 PM:name=a_civilian)--><div class='quotetop'>QUOTE(a_civilian @ Mar 14 2007, 09:57 PM) [snapback]1614384[/snapback]</div><div class='quotemain'><!--quotec-->
The sun is not sufficiently massive to form a black hole. It does not exceed the <a href="http://en.wikipedia.org/wiki/Chandrasekhar_limit" target="_blank">Chandrasekhar limit</a> even at its present mass (let alone at its mass after it <a href="http://en.wikipedia.org/wiki/Planetary_nebula#Origins" target="_blank">throws off most of its matter</a>) and cannot collapse past electron degenerate matter.

Also, even if it did collapse to a black hole, there is no reason to believe that would destroy the earth; the earth would simply be orbiting a black hole.
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Either way, we'd be screwed.

BlackMage

we orbit the sun (s) because of it's gravity (g<i> sub </i>s).
gravity is a function of mass g(m<i> sub </i>s)=g<i> sub </i>m<i> sub </i>s=g<i> sub </i>s
if the sun somehow manages to collapse, it'll still have the mass of the sun (m<i> sub </i>s). therefore g(m<i> sub </i>s) will remain constant. therefore g<i> sub </i>m<i> sub </i>s (and therefore g<i> sub </i>s will remain constant.)

(<i> sub </i>=subscript)

Faskalia

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we orbit the sun (s) because of it's gravity (g<i> sub </i>s).
gravity is a function of mass g(m<i> sub </i>s)=g<i> sub </i>m<i> sub </i>s=g<i> sub </i>s
if the sun somehow manages to collapse, it'll still have the mass of the sun (m<i> sub </i>s). therefore g(m<i> sub </i>s) will remain constant. therefore g<i> sub </i>m<i> sub </i>s (and therefore g<i> sub </i>s will remain constant.)

(<i> sub </i>=subscript)
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e=mc^2/(sqrt(1-v^2/c^2))

Our sun is emitting energy.
Because energy and mass are equivalent, it is loosing mass. Meaning that the suns gravity field is weakening, while it consumes itself.

BlackMage

e=mc^2 is for mass-energy conversions. matter can move from a high-energy state to a low-energy state while being conserved.

lolfighter

But Sol WILL lose a lot of matter when it finishes its red giant phase and collapses to a white dwarf. Will it keep enough gravity to avoid losing it's grip on earth? Of course, even if it doesn't, that'll just send the planet speeding out of the solar system and across the galaxy. But still not destroy it.

TheSavior

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But Sol WILL lose a lot of matter when it finishes its red giant phase and collapses to a white dwarf. Will it keep enough gravity to avoid losing it's grip on earth? Of course, even if it doesn't, that'll just send the planet speeding out of the solar system and across the galaxy. But still not destroy it.
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Assuming we don't collide with Saturn or something on the way out.

a_civilian

<!--quoteo(post=1614753:date=Mar 15 2007, 07:29 PM:name=Black_Mage)--><div class='quotetop'>QUOTE(Black_Mage @ Mar 15 2007, 07:29 PM) [snapback]1614753[/snapback]</div><div class='quotemain'><!--quotec-->
e=mc^2 is for mass-energy conversions. matter can move from a high-energy state to a low-energy state while being conserved.
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Er, that's not true. Change of energy state <i>is</i> a mass-energy conversion. Matter falling to a lower energy state loses potential energy, but since energy and mass are equivalent, it loses mass.

For instance, when an electron falls to a lower energy state within an atom, it emits a photon which carries off the energy (mass) the electron lost.

Or you can compare the masses of the reactants and products. The reactions occurring in the sun (proton-proton cycle and CNO cycle) essentially convert 4*hydrogen-1 into helium-4. Compare the masses of the two - the lost mass is released as gamma ray photons and neutrinos.

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e=mc^2/(sqrt(1-v^2/c^2))

Our sun is emitting energy.
Because energy and mass are equivalent, it is loosing mass. Meaning that the suns gravity field is weakening, while it consumes itself.
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At its current luminosity, the sun loses about 2.1*10^-21 its mass each second. If its luminosity remains unchanged, in 5 billion years (about its remaining lifetime) it will have lost about 1/123 of its current mass. (Actually such a high number is impossible given only hydrogen fusion, which releases about 1/140 the mass of the reactants, so either an assumption is wrong or a number is wrong. But the true number would only be lower.)

The mass of the sun could never, of course, dwindle to zero simply because it is impossible for a nuclear fusion reaction to consume all of the mass of the reactants.

Rob

But, won't the sun just eat us as a big red giant before it even collapses to a white dwarf? We'll be dead long before we see whether it becomes a black hole or not. Probably a good thing, too, I don't want to be ripped apart forever, even if it doesn't feel like forever to me...

I guess according to some observer, I'm doing something painful forever already right now... OMG! MAKE IT STOP.

a_civilian

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But, won't the sun just eat us as a big red giant before it even collapses to a white dwarf? We'll be dead long before we see whether it becomes a black hole or not. Probably a good thing, too, I don't want to be ripped apart forever, even if it doesn't feel like forever to me...<!--QuoteEnd--></div><!--QuoteEEnd-->
Not necessarily - life on earth will certainly be impossible at that stage, but it is uncertain whether the earth will actually be engulfed by the sun.

Mantrid

If we're still haven't gone anywhere else and are still hanging out around the earth by the time the sun becomes a red giant, we deserve to be destroyed.

Faskalia

<!--quoteo(post=1614753:date=Mar 16 2007, 12:29 AM:name=Black_Mage)--><div class='quotetop'>QUOTE(Black_Mage @ Mar 16 2007, 12:29 AM) [snapback]1614753[/snapback]</div><div class='quotemain'><!--quotec-->
e=mc^2 is for mass-energy conversions. matter can move from a high-energy state to a low-energy state while being conserved.
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oO

Ahm, NO!

In fact two single protons are heavier than two paired neutrons!

Matter can move from a high energy state to low low energy state and conserve its own mass only according to Newton. But Newton physics are just approximations, that only work on a very specific scale. If you want to play with molecules or astronomic objects then Newton will fail you miserably. The reason, why we use Newton and not Quantum physics, when we want to know how much potential energy a ball has on top of the Kilimancharu is, that we want to finish calculations, before the universe ceases to exist. So what we do is take an Error into account, every time we use newton. The scale of the error makes Newton work, cause in RL it doesnt matter for most processes, when our cereals have stored 1100 KJ of potential energy, instead of 1100+1,34*10^-34 KJ.

Everything in physics is an approximation. Heck even all except 1 quantum calculations are approximations, simply because you just CANNOT solve the "Schrdinger-Gleichung" for a 3-body-problem (3 Krperproblem).

BlackMage

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Er, that's not true. Change of energy state <i>is</i> a mass-energy conversion. Matter falling to a lower energy state loses potential energy, but since energy and mass are equivalent, it loses mass.
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I have a 1kg brick. I raise it to a height of 1m. It now has potential energy. I let the brick go, PE is converted to KE. The total ME in the system is constant (air resistance negligible.) Show me a mass conversion.

also, an atom has to be hit by a photon before it can be fired. the atom's mass is unaffected. not only that, a photon exists in a quantum superstate of mass-energy. i don't like getting into quantum physics.

lolf: i'm trying to give Sol as much mass as possible at the end of the thought experiment so that it has as much of a chance of collapse as possible. i even negated its rotation which can increase the critical mass by an absurd amount.

we're working on the stellar scale here, not the subatomic. you can pull all the relativistic speed exceptions you want but quantum physics can be (mostly) ignored on this scale.

a_civilian

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I have a 1kg brick. I raise it to a height of 1m. It now has potential energy. I let the brick go, PE is converted to KE. The total ME in the system is constant (air resistance negligible.) Show me a mass conversion.<!--QuoteEnd--></div><!--QuoteEEnd-->
When you raise the brick, its mass increases by (approximating g as constant) 1kg*1m*g/c^2 = 1.1*10^-16 kilograms. If the brick were sent out to infinity its mass would increase by about 7.0*10^-10 kilograms.

E=mc^2, not E=mc^2+E[p] (where E[p] is the potential energy). m[0]c^2, the rest mass or "invariant mass" energy, <i>is</i> the potential energy. (Invariant refers to its invariance under change of reference frame.)

When you release the brick, it loses invariant mass (though its relativistic mass remains constant until it hits the ground and transfers it into the surroundings).


Essentially unrelated side note: the notion of mass-energy conversion only makes sense if "mass" refers to the invariant mass m[0] and "energy" refers to kinetic energy E[k]. Then E = mc^2 = m[0]c^2 + (m-m[0])c^2 = m[0]c^2 + E[k].

If you're referring to relativistic mass m and total energy E, then mass <i>is</i> energy, and there is no sense in which one can be physically converted to the other.

(Also I edit way too much...)

lolfighter

I think that based on what we know, the prevailing belief, currently, is that Sol will NOT engulf the earth during its red giant phase. It will expand to where earth's current orbit is, but its gravity will also weaken, shifting earth's orbit further out. The planet will be deliciously golden-brown toasted, but not swallowed up. Mercury and Venus are boned however.