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

sydney.edu.au

11–20 of 193 posts

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

#11
post #5

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.

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

Okay, like what exactly?

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

#12
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.

Okay, like what exactly?

"You're in the way of a construction project, sorry, but please evacuate the planet". The fake notice costs you next to nothing.

"The plans for demolition have been available on Alpha Centauri which is only 4 light years away you know."

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

#14
post #5

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.

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

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

#15

There is a fantastic BBC Horizons documentary from the 90s called Snowball Earth that was easy to find on YouTube the last time I looked, but just now I see a hot mess of search results and if it's still in there somewhere I can't find it. EDIT: found it on dailymotion and its a great story of how the radical theory was rejected then accepted. https://www.dailymotion.com/video/x7o0b66

I briefly searched and couldn't find it either - here is the IMDB for others to reference: https://www.imdb.com/title/tt0605181/

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

#16

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.

Better than nuclear weapon, no nasty fall out. Better than death star, you still have a planet afterwards.

If they had made the death star bigger, they could have done this tbh.

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

#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 interesting how throughout time the earth has dramatically changed due to “minor” changes like volcanic activity changes, the introduction of, water, oxygen, or bacteria or other chemicals.

I had thought the sun and distance from it really was the determining factor as far as the temperature generally goes.

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

#18

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.

You have to make sure it doesn't drift away from the Langrange point, which is unstable…

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

#19

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 disguise their motives for a while, claiming to be there to help counteract global warming. Warnings from a lone scientist would be ignored. Then, as things start getting too cold, their true purpose would become clear to all.

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

#20

So, Ice Ball or Venus. Seems like climate is more sensitive than we think. Man made impact or not, the whole system seems on a knifes edge of tipping towards the extremes. That we are living right now is rare in-between point.

It could be the stability of Earth's systems is just an illusion created by observer selection. If it had not been within limits, we wouldn't be here. This places no constraint on how stable it will be in the future.

Another part of the system that could be like that is the oxygen content of the atmosphere. The time constant for variation in O2 level is just a few million years (due to consumption of O2 by release of reducing gases and weathering of rocks to expose reduced materials like ferrous iron.) If it had ever dropped too much during the Phanerozoic higher life would have been wiped out. I don't believe any plausible feedback control mechanism has been discovered. In particular, fire involving plants (which couldn't have occurred before the evolution of large land plants) can be a positive feedback, as charcoal is very resistant to further oxidation and, when buried, represents a net increase in atmospheric oxygen.

Maybe, if mankind explores the galaxy, we'll find all these formerly life bearing planets where stability failed.

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