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Comment by layer8 | Hacker News Reader

TLDR: Billions of years from now, our Milky Way galaxy and the Andromeda galaxy are expected to merge. New data show that the outer galaxy boundaries have likely already started colliding. This post contains photos and video illustrating the impending merger and showing how the Andromeda galaxy will appear in Earth’s night sky over the next 7 billion years.

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It's events like these that make me wish for some form of afterlife

I'd rather live long enough to see them.

Then work on extending human lifespan. This is something the average HN contributor could be making progress towards. E.g. make a YC company working on capability advancement in biotech, or enabling technologies like atomically precise manufacturing.

7 billion years has got to be a bit of a stretch goal, even if you're very bullish on biotech...

Do we know of anything that has that type of lifespan outside of celestial bodies like planets?

Both the earth and sun are about ~4.5 billion years old. 7 billion is completely off the charts.

M type dwarfs can easily have a lifespan in the main sequence spanning many trillions of years with even their red giant phases estimated to outlasting even the main sequence of stars of our size.

A steller mass black hole's estimated lifespan would of course make even these seem like an eyeblink by comparison.

well i suppose by then earth will be long gone.

The article says that our sun will go red giant in 7 billion years, so the earth will exist in 5 billion years to see the merger.

However, the sun will grow in energy output until going red giant, so the planet will be uninhabitable by then.

When the sun is in its red giant phase its surface will be beyond the orbit of the Earth.

Not that it will matter to any humans living billion of years from now, who will have the capability to move old blue Earth a safe distance out.

You're being mighty generous on assuming humans will still be around by then. Not many other species have made it that long.

Something descended from humans then.

I plan on being around that long though.

Indeed, current theories of stellar evolution place the extinction of life on Earth in the range on hundreds of millions of years, due to the increase of its luminosity. For example here's a description of a better climate model [1] extending the time until the surface temperature reaches 70 degrees Celsius to one billion years, whereupon feedback of the water content of the atmosphere results in boiling away all liquid water.

So while the sun may be nowhere near the end of its life, the time of Earth lying in its "Goldilocks zone" is much shorter.

[1] https://www.sciencedaily.com/releases/2013/12/131216142310.h...

I think this is the correct link ("tm" got stripped): https://www.sciencedaily.com/releases/2013/12/131216142310.h...

Thanks! - I should know better than to copy & paste a link without trial-clicking the result.

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