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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

#81

Post by mberger »

MR4D wrote: post #60
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.

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. This is probably only to LEO. Its hard to estimate but going by the geostationary payload, it would be one third of that, so triple the amount of flights. At a cadence of 2 launches per week it would take 4.5 years to launch all of it. ( 450 launches / 2 launches per week / 50 weeks a year)

1. https://en.wikipedia.org/wiki/Sunjammer_(spacecraft)

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

#82

Post by NoMoreNicksLeft »

DelaneyM wrote: post #50
saalweachter wrote: post #42

Earlier quoted context omitted.

Nah, you just need a simple Bond Villain Plot. Step One: build a machine that can cool the Earth, solving global warming Once and For All. Step Two: demand the governments of the Earth pay you $1 trillion to turn it off at the appropriate time.

I mean, a trillion dollars to solve global warming sounds like a pretty good deal to me?

Shit, I think the US spent several times that per year, without even a good plan to pay it back. Does that mean the United States is irresponsible, or the amount is just so trivial they can't be bothered? Who cares, it's some other administration's problem.

Solving global warming, turning off the earth iceball machine when it's time? Easily worth $100 trillion. OP just has no supervillain potential.

"I demand the sum of... $1 million dollars!" -- Dr. Evil

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

#83

Post by Timber-6539 »

From the article: "The team's work raises intriguing questions about Earth's long-term future. A recent theory proposed that over the next 250 million years, Earth would evolve towards Pangea Ultima, a supercontinent so hot that mammals might become extinct."

I'll keep this handy as a smart quip next time someone tries to convince me that human-led climate warming is a thing.

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

#84

Post by adolph »

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…

> They block out most but not all of the sun.

Interesting to think about:

  * How much mass could be positioned at L1 before changing the gravitational proposition of L1?
  * How large an object could be positioned at L1 before it exceeded the practical bounds of L1?
  * Presumably the object would reflect rather than absorb solar radiation. How would it deal with other solar ejecta?

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

#86

Post by JohnFen »

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…

> Growing up I honestly thought that planets evolved into a sort of natural stable state that I guess I assumed would last

This seems to be another expression of the truth that "people tend to mistake the limits of their view for the limits of the world."

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

#87

Post by macintux »

JohnFen wrote: post #86
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…

> Growing up I honestly thought that planets evolved into a sort of natural stable state that I guess I assumed would last This seems to be another expression of the truth that "people tend to mistake the limits of their view for the limits of the world."

Rumsfeld’s unknown unknowns.

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

#88

Post by JohnFen »

t00 wrote: post #85

From what I could gather from the paper, low CO2 leads to a potential ice age. Why the worldwide rush to reduce CO2 then?

Too little would be bad, yes, but too much is also bad. We can reduce CO2 by a huge amount and still have more than the amount needed for a temperate world.

We are so far over the desired greenhouse gas levels that it's a crisis and reducing it is necessary if we're to continue being able to live in relative comfort. We're not even near the ballpark of having so little greenhouse gas that this would be a worry.

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

#90

Post by robinzfc »

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…

Or maybe they showed up 200 years ago and thought: this is a very nice planet, except it's a bit too cold. What can we (compel the natives to) do to make it some 6 degrees warmer on average so that it is perfect for us? And the rest is history.
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