[harwoodleon]

I was watching the ISS live feed going over North West Africa and up to Italy. The landscape was red and arid and it struck me just how ‘Mars like’ it looked.

It got me thinking that Earth could be facing the same destiny many aeons from now. It’s hard to imagine with the amount of H2O on the planet right now, but if it can happen to Mars (the atmosphere is stripped away), it could happen here I suppose.

But I wonder if a Venus situation is more likely first, because of our proximity to the Sun?

This discovery certainly makes me feel that lifecycle of planets is an awesome thing.

[cletus]

It's not even a question: the Earth is absolutely facing the same fate. The Sun is getting hotter and in ~1 billion years the Earth will be uninhabitable by us in its current form.

Eventually (~4-5B years) the Sun will expand while in its dying stages and probably swallow the Earth.

What can we do? That's actually quite "easy". I mean "easy" in the essence that no weird new physics is required, it's just an engineering problem, albeit a massive one. Then again, we have a lot of time. So there are essentially three things we can do:

1. Reduce the amount of light and heat hitting the Earth. Example: large arrays of solar power collectors at the L1 Lagrange point. If the Sun is 10% hotter in 1B years and you reduce the light hitting the Earth by ~10% it about evens out. The captured energy can be put to use and I expect it wouldn't even be noticeable from Earth. The Sun will just be slightly dimmer;

2. You can move the Earth. Many people are familiar with gravity assists for spacecraft. Obviously gravity affects both bodies but the spacecraft is so low-mass it has no discernable effect on the larger body. Imagine taking large rocks and flying them past the Earth. The net interaction can be that the Earth moves slightly faster. Do this over a long enough time frame and you can move the Earth's orbit outwards.

3. The Sun itself can be manipulated to remove mass from it, particularly Helium.

A lot can be done in a billion+ years.

[T-A]

> A lot can be done in a billion+ years.

Indeed, to the point that talking about it in terms of what "we" could do about it in ordinary engineering terms becomes pointless.

A billion years ago, the first multicellular plants were beginning to move onto land; animals were still water-bound single cells who would have to wait another couple hundred million years to discover sex. Whatever life still exists on Earth a billion years from now will presumably be as far removed from us as we are from those ancient ancestors.

https://en.wikipedia.org/wiki/Timeline_of_the_evolutionary_h...

[jjcon]

Very interesting - couldn't we also just evolve to live with a hotter sun in a billion years or will it affect other systems so much that life for humanoids will be more difficult?

[cletus]

A lot of problems ultimately turn into energy problems.

Lack of recycling comes down to it mostly being uneconomic to do so. There can be a labor component to this too but the energy cost matters. A lot of labor can be automated, which then also becomes an energy problem.

It's highly likely that in 1B years, we'll have access to energy many orders of magnitude higher than we do now and it'll probably be much cheaper. My personal prediction is the space-based solar power collection is likely to be dominant. The big unknown is fusion. Personally I'm not yet convinced fusion will ever be economical, but that's a whole other topic.

We live in hot, dry climates now (eg the Middle East). What makes that possible is simply energy for food and water production, climate control and so on.

It'll likely be worse for other life on Earth but that too is an energy problem. Also, we have no real idea of what life will look like in 1B years since we'll likely have gone through several mass extinction events between now and then.

And of course, in the last 1B years we've largely gone from single-celled and early multi-cellular organisms to what we have now.

[rowanG077]

Evolution like that won't happen in a modern society like we have where we care for everyone and fight against nature.

I'd imagine evolution is possible but only under collapse of civilization as we know it.

[cletus]

So this opinion is a fairly popular one but I'm not sure there's any factual basis for it.

The idea is simple: there's little evolutionary pressure to adapt because technology and society can deal with issues that once would've been fatal.

There are a bunch of issues that still affect survivability though: recklessness, propensity for violence, inability to survive in modern society, addiction issues, mental health issues, etc. We can expect all of these to improve but go away entirely? That's less certain.

Even if you ignore mortality issues, the other side of natural selection is how many offspring you have and how many of them survive to have their own offspring. If a group with trait A has an average of 2 children each but trait B have an average of 3, it's not too many generations before B becomes dominant.

Evolution is also relatively slow and not smooth. We only identified DNA ~50 years ago and mapped the human genome in the last 10-15. It's a bit early to refute observational evidence.

Remember too that certain traits that were once advantageous can become a disadvantage or they only become a disadvantage in certain circumstances. Take the modern abundance of food. Some people have genes that predispose them to storing excess, others less so. 1000 years ago, that was probably an advantage. Now? Less so, both in terms of health effects related to, say, obesity, but also in terms of finding a mate and having offspring given changing societal standards for beauty (not universal of course).

[rowanG077]

Oh definitely. I didn't mean evolution is halted. I mean evolution that would protect us better against the elements in this case.

[GekkePrutser]

But in such a society we'll figure out how to adapt ourselves using DNA modification, doing evolution's job for it. We're getting pretty close already and a billion years is more than enough.

But we'll have other challenges first like finite resources and our self-destructive tendencies. We'll have made bigger fish to fry before we can even make it a billion years

[jeffdn]

The combination of two processes -- tectonic activity and the increased luminosity of the sun -- will mean that surface water no longer exists at that time.

[yosito]

> in ~1 billion years the Earth will be uninhabitable by us in its current form

In ~1 billion years, "we" won't be inhabiting anything in our current form. If humanity/primates haven't gone extinct by then, they will have evolved completely beyond our current form.

[idiotsecant]

4. Develop into a matrioshka brain civilization and mine all the rocky planets for materials to convert to solar computronium.

A billion years is a long time. I feel like this or extinction are the only two real scenarios.

[krisoft]

About North Africa: archeological findings seems to imply that what is now the Sahara desert was much more lush and wet relatively recently. We have human made cave paintings of river animals in areas which are very dry nowadays. It is thought that the area dried out relatively suddenly about 5k years ago. That is basically yesterday as far as geological timescales go.

When I learned about this I got kinda scarred. If the climate of an area can change this drastically all of a sudden that means to me that the climate system is a lot less stable than I previously have thougt.

[jandrewrogers]

Something similar happened on a smaller scale in North America with Lake Lahontan[0], which covered much of Nevada after the last ice age. If you walk the old shoreline up on the mountainsides, it is not uncommon to find evidence of the neolithic people that lived on its shores before it disappeared.

[0] https://en.wikipedia.org/wiki/Lake_Lahontan

[MayeulC]

https://en.wikipedia.org/wiki/African_humid_period

IIRC one of the causes might be orbital precession, which could lead to a re-greening in a few millenia.

[mixmastamyk]

The much larger mass, gravity, and magnetic field of Earth prevents large scale atmospheric losses. Whether we have the resources to ignite another Venus remains to be seen.

[exporectomy]

Remains to be seen or is already known to be impossible? All the carbon in fossil fuels originally came from the atmospheric CO2, didn't it? And it was never as hot as Venus. What are the steps we would need to take to make it as hot as Venus in any kind of physically possible scenario?

[virtue3]

You are drastically under-estimating the effects of other compounds in the atmosphere.

Methane is a really good example.

HFCs were a great bit of disaster for a bit there as well.

from: https://en.wikipedia.org/wiki/Greenhouse_gas#Impacts_on_the_...

"The contribution of each gas to the greenhouse effect is determined by the characteristics of that gas, its abundance, and any indirect effects it may cause. For example, the direct radiative effect of a mass of methane is about 84 times stronger than the same mass of carbon dioxide over a 20-year time frame[27] but it is present in much smaller concentrations so that its total direct radiative effect has so far been smaller, in part due to its shorter atmospheric lifetime in the absence of additional carbon sequestration. On the other hand, in addition to its direct radiative impact, methane has a large, indirect radiative effect because it contributes to ozone formation. Shindell et al. (2005)[28] argues that the contribution to climate change from methane is at least double previous estimates as a result of this effect.[29]"

[mixmastamyk]

Too many variables to account for.

Didn't mean to imply we could get "as hot as" Venus, which is unlikely due to our distance from the Sun. But hot enough to boil water? Possibly, given a runaway chain reaction. Not sure.

[heavyset_go]

> It’s hard to imagine with the amount of H2O on the planet right now, but if it can happen to Mars (the atmosphere is stripped away), it could happen here I suppose.

Mars' atmosphere isn't protected by a strong magnetic field because the planet isn't geologically active, unlike the Earth. Gasses escape from the Earth into space constantly, but not at a rate that will leave the Earth like Mars before the sun becomes a red giant.

In billions of years, the sun will expand and probably blast away the Earth's atmosphere before possibly engulfing it later.

[pfdietz]

The Earth will lose its oxygen first, then enter a moist greenhouse. This is all long before the sun becomes a red giant.

https://phys.org/news/2021-03-simulations-earth-oxygen-rich-...

(the summary there is inaccurate; CO2 will be increasingly absorbed by weathering of rocks as the Earth heats, until photosynthesis fails and oxygen levels collapse.)

[heavyset_go]

Nice, thanks for the link.

[kibwen]

I'm no astrophysicist, but I'm under the impression that the effect of the magnetosphere is popularly overstated. Rather, the reason that Earth still has its atmosphere and Mars doesn't is that Earth has the gravity to hold onto it more tightly, and Mars is just too small. Hence why Venus, which also (curiously) has no dynamic magnetosphere, still has an atmosphere: it's 80% the mass of Earth (compare Mars, which is 10% the mass of Earth).

[heavyset_go]

The death of Mars' magnetosphere allowed solar wind plasma to strip away its atmosphere in the past[1]. Mars once had a much denser atmosphere when its dynamo was active, and the stripping of its atmosphere happened when the dynamo died.

[1] http://redplanet.asu.edu/?p=2035

[vkou]

Titan is ~Mars-sized, yet it has an atmosphere thicker than that of the Earth.

It may be safe to say that both factors are at play, here.

[jeffdn]

Titan is largely protected by Saturn's powerful magnetosphere, which does a lot to help, I imagine.

[moaaps]

Isnt this the rift valley?

[5faulker]

And here's we are at a paradox, where one side is attempting to escape imminent danger by traveling outside Earth, and in doing so potentially accelerating its instability.