I think this was the link i meant to post earlier. This one says 80000 years
When peering thousands of years into the future, there are certain things we can count on -- evolution, extinction, plate tectonics, climate change and, quite possibly, the eruption of a supervolcano. What else does the Earth's far future hold?
science.howstuffworks.com
Ice down to NY is a little worse that that picture tbh. Alot of europe if not all covered in ice.
This glacial cycle has been going for a couple million years, there's no particular reason to think the next one (in 50-100 kya) will be any worse than the ones that came before. In North America the glaciers seem to advance farther south because the geography of Canada favors their growth, whereas the geological record is clear that most of Germany and France, and the southern UK, are ice-free during most glacial periods.
There
have been full planet-wide freezes - look up Snowball Earth sometime - but not in nearly a billion years, and with the hotter Sun we have now it might be impossible for that to happen anymore.
The most common one I've seen is 250-300 million years in which phase the increase in luminosity of the sun will distrupt the carbon cycle and gradually render multicellular life impossible (bacterial life will probably hundreds of millions of years after that).
The mechanism by which the Sun is brightening is well-understood: as helium "ash" accumulates in the core, the temperature and fusion rate have to increase to maintain pressure equilibrium with the overlying layers. Because of this, the luminosity increases by about 1% per 100 million years.
What is less well understood is how the Earth will respond. Pessimistic models have the Earth going into Venus-like runaway greenhouse within 100 million years. Optimistic models have various effects counter-balancing the luminosity effect and keeping the Earth habitable for as much as another couple billion years. Somewhere in the middle is the model you mentioned.
Interesting synopsis but I humbly disagree. I think it is presumptuous to think we could receive and interpret a signal from another species. We can't understand the majority of species on our own planet, so how could we understand someone from another planet?
Think of it this way, if an ET sent us a signal less that 100 years ago, we would not even know, and we definitely wouldn't have replied. To the ET, it might just seem we are being a bad neighbour or an ignorant one.
The argument you're responding to is an old one, most famously stated as the Fermi Paradox. The points roughly go:
- Even if the only possible means of interstellar travel is via slow probes and generation ships, it takes less than a billion years to cross the Milky Way
- Expanding at such a slow pace, each colony would have ample time to send ships to two or more unvisited stars, so the number of visited systems would expand exponentially
- Thus, if a species became capable of interstellar travel, you could expect that it would expand to visit every star in the galaxy in less than a billion years
- The galaxy is billions of years old, and contains billions of potentially life-bearing planets. Unless the above scenario is impossible for some reason, you would expect it to have happened by now.
Depending on who you ask, this means that interstellar travel is impossible, that intelligent life inevitably destroys itself, or that the above has in fact happened and for some reason we just haven't noticed. I once had the pleasure of a fascinating dinner with Jill Tarter, at the time director of the SETI project. She left me tentatively convinced that the most likely answer is the last one, but that after becoming long since adapted to life in interplanetary and interstellar space, there would be little reason to venture down into the deep gravity wells. We are most likely to find evidence of alien life by conducting archaeology out in the asteroids and icy moons in the outer solar system.
