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What made Earth a giant snowball 700M years ago? Scientists have an answer

sydney.edu.au

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Re: What made Earth a giant snowball 700M years ago? Scientists have an answer

#111

Post by huytersd »

adastra22 wrote: post #109
huytersd wrote: post #101

Earlier quoted context omitted.

I wonder if we’ll get to a computational space where we can completely simulate every atom in a small closed system. Are we there yet? Can you simulate at the atomic scale and get a perfect representation of reality or do we have to try and simulate something smaller?

We can get up to 100 or so lightweight atoms (the real limiter is the number of electrons, not the number of atoms. Larger atoms cost more). Maybe a thousand or so on supercomputers. Quantum computing will change this though.

Is it an absolutely perfect simulation? Like would we know the exact future of those hundreds of atoms in perpetuity?

Re: What made Earth a giant snowball 700M years ago? Scientists have an answer

#112

Post by ianburrell »

SketchySeaBeast wrote: post #34
WarOnPrivacy wrote: post #14

Earlier quoted context omitted.

> Have you done the calculation how much material is required for such an endeavor? It's a tiny fraction of what's required for a proper Dyson sphere. And we know civilizations can afford those because we can no longer see their stars. For anyone who's hung up on saving nickle, we could do a low budget Worldring² or even thriftier Shadow Squares®. ²Nivenlarry ®Larry Niven

> And we know civilizations can afford those because we can no longer see their stars. That's a giant claim you just made like it's fact.

It is especially big claim because there have been recent searches for Dyson Spheres and none of have been found. I think the Gaia spacecraft covered most of the visible half of the galaxy.

Dyson Spheres would be really obvious, emitting infrared radiation unlike normal stars.

Re: What made Earth a giant snowball 700M years ago? Scientists have an answer

#113

Post by justinator »

huytersd wrote: post #101
duxup wrote: post #17

A recent PBS documentary did a great job talking about all the changes the earth has gone through: https://www.pbs.org/wgbh/nova/article/the-history-of-earth-i... They had a series on planets and some of their history too. Growing up I honestly thought that planets evolved into a sort of natural stable state that I guess I assumed would last until the sun or other external force decided otherwise. But it’s interestin…

I wonder if we’ll get to a computational space where we can completely simulate every atom in a small closed system. Are we there yet? Can you simulate at the atomic scale and get a perfect representation of reality or do we have to try and simulate something smaller?

There's a chance - however small - that WE live in that simulation.

Re: What made Earth a giant snowball 700M years ago? Scientists have an answer

#114

Post by simonh »

huytersd wrote: post #107
simonh wrote: post #104

Earlier quoted context omitted.

It's a bit of a stretch perfectly simulating one proton, I'm afraid. https://www.quantamagazine.org/inside-the-proton-the-most-co...

Oh wow. Maybe that can be a new scale measure of technological capability based on how much of reality we can perfectly simulate.

If you think about it, a computer's not going to be able to perfectly simulate it's own physical operation, so the limit of a system's ability to simulate things is it's own complexity.

Re: What made Earth a giant snowball 700M years ago? Scientists have an answer

#115

Post by at_a_remove »

duxup wrote: post #17

A recent PBS documentary did a great job talking about all the changes the earth has gone through: https://www.pbs.org/wgbh/nova/article/the-history-of-earth-i... They had a series on planets and some of their history too. Growing up I honestly thought that planets evolved into a sort of natural stable state that I guess I assumed would last until the sun or other external force decided otherwise. But it’s interestin…

Well, it's a really good start. Total insolation is a great, ah, trend marker. Higher insolation planets tend to be warmer.

Of course, insolation itself stops looking less like a number and more like a function. After all, you're getting photons of different wavelengths (pretend the sun in question is a blackbody) and so that feeds into absorption, reflection, and transmission of each frequency component versus the local atmosphere.

Local atmosphere is a function of surface gravity, orbital velocity (you have to scoop up those gases after all), geologic activity, possible tidal lock, and temperature. Whoops! Back to where we started.

But it is still a great trend. Very low-mass planets are in some ways easier to model. If they are far from a star, any gases that wouldn't escape would freeze and just fall down as another layer of the planet. If they are close to a star, you're just not going to have much atmosphere for long.

Once you are big enough to retain an atmosphere, stuff can get wonky.

Re: What made Earth a giant snowball 700M years ago? Scientists have an answer

#116

Post by ianburrell »

WarOnPrivacy wrote: post #14
baxtr wrote: post #5

Earlier quoted context omitted.

Have you done the calculation how much material is required for such an endeavor? I bet there are more cost effective approaches.

> Have you done the calculation how much material is required for such an endeavor? It's a tiny fraction of what's required for a proper Dyson sphere. And we know civilizations can afford those because we can no longer see their stars. For anyone who's hung up on saving nickle, we could do a low budget Worldring² or even thriftier Shadow Squares®. ²Nivenlarry ®Larry Niven

The flaw with your theory is Dyson Spheres don't hide the star. They convert visible light into infrared light. No energy conversion is perfect and always produces waste heat. Dyson Sphere basically looks like a really large star.

The infrared star stands out because it is different than normal stars.

Re: What made Earth a giant snowball 700M years ago? Scientists have an answer

#117

Post by apothegm »

twojacobtwo wrote: post #39

> Co-author Professor Dietmar Müller from the University of Sydney said: Geology ruled climate at this time. We think the Sturtian ice age kicked in due to a double whammy: a plate tectonic reorganisation brought volcanic degassing to a minimum, while simultaneously a continental volcanic province in Canada started eroding away, consuming atmospheric CO2. Research: > Duration of Sturtian “Snowball Earth” glaciation l…

How would erosion consume CO2?

Re: What made Earth a giant snowball 700M years ago? Scientists have an answer

#118

Post by digging »

justinator wrote: post #113
huytersd wrote: post #101

Earlier quoted context omitted.

I wonder if we’ll get to a computational space where we can completely simulate every atom in a small closed system. Are we there yet? Can you simulate at the atomic scale and get a perfect representation of reality or do we have to try and simulate something smaller?

There's a chance - however small - that WE live in that simulation.

More likely that if it's even possible, the chance is near 100%.

However, it actually doesn't matter in any way whatsoever.

Re: What made Earth a giant snowball 700M years ago? Scientists have an answer

#119

Post by philipkglass »

mberger wrote: post #81
MR4D wrote: post #60

Earlier quoted context omitted.

I wonder how that would look from a feasibility perspective... Let's see - Earth's radius is 6,378 km. Area exposed to the sun therefore would be 6,378 * 6,378 * 3.14 = 127,731,695 [1] If you wanted to block just 1% of the light, that would take a shade of 1 million square kilometers, which would be equivalent to a shade that is 1,130 km on a side. Seems like it would be tough to do given all the dust and rocks float…

Interesting. That area would be roughly one million Sunjammers[1]. One Sunjammer is 1200 m^2 and wights 32 kg. To lift all this would be 32 million kg or 32000 tons. One Starship launch is designed for 250 metric tons when expendable so it would take 128 launches. Add in some fudge factor for orbital burns and I figure 150 launches would do it. Doesn't seem insurmountable. Edit: Seems I misread the Starship capacity.…

1 million square kilometers is 1 trillion square meters, or 833 million Sunjammers. It would take 3748 years to launch them at 2 Starship launches per week.

Re: What made Earth a giant snowball 700M years ago? Scientists have an answer

#120

Post by digging »

nullhole wrote: post #19
itronitron wrote: post #3

Seems like a low risk approach for taking over a planet would be to just park a large shade between the planet and it's star then let it enter a deep freeze. Then you could just remove the shade and let the planet warm back up before settling down.

That'd make for a good story setup: aliens park a shadeship (c) at L1 and wait. They block out most but not all of the sun. After some time (months? years?), conditions on Earth become unbearable, so earthlings have to mount an attack. Kind of like the movie Sunshine, but with more believable physics. Edit: as a bonus, it could take place in ~50-100 years, when global warming has gotten worse. The aliens could disgui…

> Warnings from a lone scientist would be ignored.

A good movie plot, but I imagine in reality it would be obvious from the start that this would be a possibility and no scientists would be caught off-guard when the shade just didn't get removed. I can be almost certain as well that large factions of humans would "know" (believe, based on no facts) that is was happening all along and there would be incredible conflict across Earth as we figured out how to deal with this gentle attack, even before it was certain that is was an attack.

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