Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

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

sydney.edu.au

Post reply on HN
Print view View original

141–150 of 193 posts

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

#141

Post by slashdev »

itronitron wrote: post #35
slashdev wrote: post #26

Earlier quoted context omitted.

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…

I was thinking the deep freeze might be useful in preserving some potential food sources, assuming it happens quickly enough. But I agree sterilizing the planet provides some advantage as well.

Aliens probably would not be able to eat Earth life.

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

#142

Post by tambourine_man »

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?

The hack is to find emergent behavior so that you don’t need to simulate every atom. That’s what we did with classic thermodynamics. Extremely simple rules that accurately describe crazy complex systems.

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

#143

Post by apothegm »

philipkglass wrote: post #129
apothegm wrote: post #117

Earlier quoted context omitted.

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 play…

So this basically also depends on a thriving population of shellfish to fix the carbon?

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

#144

Post by tzs »

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…

> 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.

Maybe their own star system is not safe for them. Say a political or religious minority that the majority would like to exterminate.

> And even if you were going to do that for some crazy reason, there's no shortage of uninhabited planets out there. There's no need to commit planetary genocide of an alien race.

If they've got cheap and easy FTL, sure. But suppose they don't have FTL. They are going the slow way, using a generation ship. At launch they may only know that their destination has a habitable planet but not know if it has intelligent life already.

Their generation ship environment might not be reliable enough for them to want to risk trying to move on to another star if it turns out the first habitable plant already has intelligent life.

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

#145

Post by ajuc »

sand500 wrote: post #121
mberger wrote: post #81

Earlier quoted context omitted.

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.

They would attract each other and clump into a loose ball.

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

#146

Post by shagie »

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?

From a few years ago - https://www.nytimes.com/interactive/2021/12/01/science/coron...

> To better understand the coronavirus’s journey from one person to another, a team of 50 scientists has for the first time created an atomic simulation of the coronavirus nestled in a tiny airborne drop of water.

> To create the model, the researchers needed one of the world’s biggest supercomputers to assemble 1.3 billion atoms and track all their movements down to less than a millionth of a second. This computational tour de force is offering an unprecedented glimpse at how the virus survives in the open air as it spreads to a new host.

> ...

> Once the virus was loaded into an aerosol, the scientists faced the biggest challenge of the project: bringing the drop to life. Dr. Amaro and her colleagues calculated the forces at work across the entire aerosol, taking into account the collisions between atoms as well as the electric field created by their charges. They determined where each atom would be four millionths of a billionth of a second later.

> To carry out this vast set of calculations, the researchers had to take over the Summit Supercomputer at the Oak Ridge National Laboratory in Tennessee, the second most powerful supercomputer in the world. Because the machine was in high demand, they could run their simulation only a few times. “We only have so many shots to actually see if we can get this thing to actually fly,” Dr. Amaro said.

> The first run was a disaster. Tiny flaws in their model caused the virtual atoms to crash into one another, and the aerosol instantly blew apart. “It basically explodes,” Dr. Amaro said.

> After half a dozen rounds of adjustments, the aerosol became stable. The researchers ran the calculations all over again to see what happened inside the aerosol an instant later. All told, they created millions of frames of a movie that captured the aerosol’s activity for ten billionths of a second.

-----

Aside: the "four millionths of a billionth of a second" is 4fs or 4x10^-15 seconds - https://www.wolframalpha.com/input?i=four+millionths+of+a+bi...

> 0.4 x time for a typical water molecule vibration

The corresponding press release: https://www.olcf.ornl.gov/2021/11/16/we-know-covidisairborne...

The abstract presented - https://sc21.supercomputing.org/proceedings/tech_paper/tech_...

Preprint of paper that matches the abstract mentioned in the ornl press release - https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8609898/

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

#147

Post by WalterBright »

iszomer wrote: post #134
WalterBright wrote: post #123

Earlier quoted context omitted.

The simulation theory is indistinguishable from any religious explanation.

It can be from a secularization point of view.

People have rejected religion, and simply invented another one to replace existing ones.

People who believe in the simulation also tend to try and influence it (Scott Adams does), using a method indistinguishable from prayer.

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

#148

Post by mcguire »

thaumasiotes wrote: post #133
WalterBright wrote: post #123

Earlier quoted context omitted.

The simulation theory is indistinguishable from any religious explanation.

Things are weirder than that. It's also indistinguishable from the "brain in a vat" theory, which everyone has heard of and which nobody finds interesting. It escapes me why anyone finds "simulation theory" more interesting than that.

Solipsism isn't even refutable.

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

#149

Post by luma »

huytersd wrote: post #111
adastra22 wrote: post #109

Earlier quoted context omitted.

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?

I’d recommend reading up on Heisenberg’s Uncertainty Principle to understand why what you suggest is, to our knowledge, physically impossible.

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

#150

Post by mcguire »

Timber-6539 wrote: post #83

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.

250 million years vs five decades.
Post reply on HN