> If dark energy really is Einstein’s constant, the standard model portends a bleak future: The universe will keep speeding up, forever, becoming darker and lonelier. Distant galaxies will eventually be too far away to see. All energy, life and thought will be sucked from the cosmos.
The laws of thermodynamics pretty much guarantees this anyways does it not?
Thermodynamics says there will be equilibrium, not that it will be all dark. But all the visible stars will run out at some point, and since nothing new can get into that sphere, each place in space will be "dark" at some point.
What about the CMBR, I've never heard anyone say that's decaying, but surely it's not an infinite source of energy?
The CMB is red-shifting due to the expansion of the universe. If the big bang was infinite then the CMB is also infinite, but at some point it becomes so redshifted that photons from it have a wavelength larger than the Hubble volume.
The collision probably won't do much more than trigger a period of star formation – although that will be accompanied by an increase in supernova frequency as the most massive of the newly-born stars quickly burn out in mere millions of years.
like two flammable gas clouds colliding perhaps. Literally one of the most energetic processes in the known universe, with 100x the rate of star formation.
Why would you be concerned? Earth and everything living on it will be long dead by then, and probably gone and swallowed by the sun. And maybe the Sun dies before that, too. So what would be particularly concerning about merging of our galaxy with another one?
> Earth and everything living on it will be long dead by then
How do you know? It's not far fetched to think that, if humans don't go extinct in the meantime, they will continue to find ways to shape the world according to their needs. By the time the Sun goes red giant, we may well have found a way to alter the orbit of Earth. By the time the Sun goes supernova, we may be able to move to another star. Who knows.
But let's not get distracted. We need to tackle climate change first. That's our first self-made extinction challenge.
Hmm, yes, I don't. I just honestly don't get why that galaxy collision is concerning. What's the concern? For whom? Four billion years is very, very long compared to humankind's evolutional history. Homo may be 2 My old, that's 1% of the time it takes the sun to rotate a single time around the center of the galaxy. Sol completed already ~20 rotations since it exists. Homo's whole history is 1/2000th the time ntil Andromeda will arrive. So, what's the concern? Humankind will not exist for many, many hundreds of millions of years.
> It's not far fetched to think that, they will continue to find ways to shape the world according to their needs.
Humans fixing Earth's and Humanity's problems is totally out of character. I did not even consider it.
Earth's death is certain. Sun's death is certain. Galaxy collision might even go unnoticed for quite a while -- it's not like millions of stars would crash into each other -- very unlikely. It's more like a reshaping, but what's concerning about that? More supernovas around us? Yeah, maybe.
But why is it more concerning that any other demise? It is an interesting question, I think, about perceived danger.
Existence, universe, galactic processes and time scales are very fascinating. I do loose sleep over it, but because it is impossible to grasp, so marvellous and unlikely. And it is treated like shit by too many of my fellow earthlings. My worries are much closer and much more concrete than a galaxy collision, and I think much more urgent.
> How do you know? It's not far fetched to think that, if humans don't go extinct in the meantime, they will continue to find ways to shape the world according to their needs.
I'd say it's pretty far-fetched to imagine humans caring about things 7 generations into the future, let alone 3e7 generations.
> By the time the Sun goes red giant, we may well have found a way to alter the orbit of Earth. By the time the Sun goes supernova, we may be able to move to another star. Who knows.
We already know how to meaningfully alter Earth's orbit over such timescales[0], the sun won't go super-nova anyway (too small)[1], and we know what it would take to increase its lifetime by a few orders of magnitude even if organising ourselves on the numerical and time scales required is beyond us[2].
But even maximally extending the lifespan of Sol would take us to perhaps 100 trillion years if we're very lucky, and that's if we actually engage in the exact kind of long-term thinking that people currently criticise the Longtermism movement for even daring to consider.
Stellar Husbandry, wild! Obviously anyone in to sci-fi might have come across the idea of meddling with a star somehow, but I'd never thought to classify it all under the umbrella term stellar husbandry.
I don't think climate change, even if it lives up to the most alarmist of predictions will make humanity extinct. We'll all be gone regardless of that. A functioning civilization is composed of humans (at least in our case), and every generation of humans must have as its first priority the task of making more humans to replace the oldest (dying) generation. The fertility rate is sub-replacement, the effects of a demographic implosion cause more fertility rate issues, not less, and so that will accelerate. Too neurotic to have sex and make babies. Climate change wasn't what you needed to tackle after all.
The laws of thermodynamics pretty much guarantees this anyways does it not?