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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

#121

Post by sand500 »

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.…

Does it have to be a sheet of material? If all we want to do is shade the earth, we could launch a few million KGs of glitter into low earth orbit or to the Sun-Earth L1.

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

#122

Post by goodgoblin »

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…

this is such a good idea for a movie

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

#123

Post by WalterBright »

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.

The simulation theory is indistinguishable from any religious explanation.

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

#124

Post by WalterBright »

anonporridge wrote: post #58
nullhole wrote: post #19

Earlier quoted context omitted.

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…

> The aliens could disguise their motives for a while, claiming to be there to help counteract global warming. Seemingly benevolent aliens just here to help us fix our mess, but ultimately just want to sneakily take our stuff, is fun trope. https://www.gateworld.net/sg1/s4/2010/

"To Serve Man"

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

#125

Post by WarOnPrivacy »

SketchySeaBeast wrote: post #108
WarOnPrivacy wrote: post #100

Earlier quoted context omitted.

> That's a giant claim you just made like it's fact. You are correct. That is absolutely a thing I did.

But it doesn't make any sense, given we do not have good evidence of alien civilizations, not to mention Dyson spheres.

> But it doesn't make any sense, given we do not have good evidence of alien civilizations, not to mention Dyson spheres.

Also correct. Even past that, we haven't been mass-cataloging stars long enough for a Dyson sphere to be constructed and remove a star from our view.

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

#126

Post by digging »

slashdev wrote: post #26
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.

Or you could just smack it with a really big rock. That nicely sterlizes the planet too, so you can reseed it with life from your planet after to make it more comfortable. Honestly it's all kind of silly because distances are so vast. It makes little sense to travel to a distant star - much better to build space habitats in your own star system. And even if you were going to do that for some crazy reason, there's no…

> a really big rock ... nicely sterlizes the planet

Have you seen Earth? We've been hit with a big rock, we've turned out atmosphere into poison, and had several other mass extinctions, none of which sterilized the Earth.

Unless you mean a Theia-level rock to turn the entire surface into lava, but you risk changing the mass, composition, and satellite system of the planet. At that point it's a different planet entirely, so I don't know why you would expend all that energy. Just find another planet to live on.

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

#127

Post by SketchySeaBeast »

WarOnPrivacy wrote: post #125
SketchySeaBeast wrote: post #108

Earlier quoted context omitted.

But it doesn't make any sense, given we do not have good evidence of alien civilizations, not to mention Dyson spheres.

> But it doesn't make any sense, given we do not have good evidence of alien civilizations, not to mention Dyson spheres. Also correct. Even past that, we haven't been mass-cataloging stars long enough for a Dyson sphere to be constructed and remove a star from our view.

So why make the initial claim "And we know civilizations can afford those because we can no longer see their stars."? Is it humor or irony I'm missing?

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

#128

Post by digging »

downsplat wrote: post #106

I remember it was one of the remarkable take-away points of nonlinear system dynamics, aka chaos theory: the weather/climate system doesn't even have an "average regime" that it converges on. You can average over longer periods of time, and the resulting sequence doesn't necessarily converge to a single limit. Pretty mind boggling when you think about it. Long term enough, "this place's climate" doesn't even exist.

This is clear even without that knowledge if you take a long enough view. The sun will eventually boil our oceans, and then later the solar system will spend the vast majority of its existence in total darkness.

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

#129

Post by philipkglass »

apothegm wrote: post #117
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?

It's the carbonate-silicate cycle. Erosion of silicate rocks (which form most of the Earth's crust) by chemical weathering consumes CO2 from the atmosphere and turns it into thermodynamically stable carbonates. Those carbonates can eventually be subducted and their CO2 released again by heat from the Earth's interior.

https://personal.ems.psu.edu/~jfk4/PersonalPage/ResInt2.htm

The carbonate-silicate cycle, which plays a key role in stabilizing Earth's climate over long time scales, is shown in Fig. 2. The cycle begins when atmospheric CO2 dissolves in rainwater, forming carbonic acid, H2CO3. Through a process termed "weathering", this weak acid dissolves silicate rocks on the continents, releasing Ca++, Mg++, HCO3- (bicarbonate), and SiO2 (dissolved silica) into solution. The products of weathering make their way down to the oceans in streams and rivers. There, organisms such as the planktonic foraminifera that live in the surface ocean use them to make shells out of calcium carbonate (CaCO3). When the organisms die, they fall down into the deep ocean, where most of the shells redissolve. Some of the calcium carbonate survives, however, and is buried in sediments on the seafloor. The seafloor spreads from the midocean ridges and, at some plate margins, is carried down subduction zones. The carbonate minerals recombine with SiO2, which by this time is the mineral quartz, to reform calcium and magnesium silicates and release gaseous CO2. This CO2 is vented into the atmosphere through volcanoes, thereby completing the cycle.

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

#130

Post by lumost »

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…

This reminds me of the game "SPORE" in the last stage, you flew around in a spaceship conquering planets. The game had a balance problem, but while the space combat was difficult - it was rather easy to fly around a planet really quick "Terraforming". Remove the entire atmosphere, then add the atmosphere back and plant a colony.

As a bonus, the other aliens in the game didn't view destructive terraforming as equivalent to WMDs - you could do this without even declaring war.

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