Wikipedia:Reference desk/Archives/Science/2022 December 29

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December 29

What will the Andromeda–Milky Way collision look like?

Assuming the Andromeda–Milky Way collision is really going to happen, if there would be anyone on Earth left to see it, what would it look like? Would it look like a great lot of stars getting brighter and brighter, then getting dimmer and dimmer again? JIP | Talk 19:56, 29 December 2022 (UTC)

Stars will remain the roughly same but their configuration will change, with the Milky Way band gradually disappearing. Ruslik_Zero 20:08, 29 December 2022 (UTC)

The Hubble Space Telescope captured this image of two colliding galaxies. Located 300 million light-years away in the constellation Coma Berenices, the view has been nicknamed “The Mice” because of the long tails of stars and gas emanating from each galaxy. Otherwise known as NGC 4676, the pair will eventually merge into a single giant galaxy. Philvoids (talk) 20:31, 29 December 2022 (UTC)

That picture is taken from the viewpoint of an outside observer. What I was asking about is, assuming humanity still existed on Earth when the collision comes to pass, what would it look like to an observer standing on the Earth and looking at the Andromeda galaxy approaching the Earth. I presume the galaxy would eventually start appearing to the naked eye as it does on the space telescope photographs. What would it look like when it comes even closer? Would the sky be engulfed in the interstellar gas which shows up so prominently in the space telescope photographs, or is it too sparse to be visible when viewed right up close? JIP | Talk 23:50, 29 December 2022 (UTC)

From within, it would depend on whether the observer is in a starburst region. Inside that area there would be a lot of bright, new stars with short lives. Outside those areas where stars are created quickly, it would look about the same as always, just rearranged. After the starburst is over and things have settled down, the star population would be increasingly older stars with little interstellar matter. See starburst galaxy for more -Messier 82 is the closest example, and Messier 81 has brightened up too. But the view from inside would depend on whether you're in a star-creating region. That area, though, might be a little hazardous, with a higher frequency of supernovas and gamma ray bursts.Acroterion (talk) 23:59, 29 December 2022 (UTC)

Thank you, this gives me more information about the scenario. JIP | Talk 00:04, 30 December 2022 (UTC)

"Short" and "quick" on astronomical time scales, but not on a human time scale. To the unaided observer, the night sky would not change perceptibly from year to year. The occasional (super)nova would be an exception, but these would still be relatively rare events.  --Lambiam 10:24, 30 December 2022 (UTC)

The Andromeda galaxy (or at least the central, brightest part) is already visible to the naked eye, assuming you're in a properly dark place (hard to find these days in Europe, but in Finland you should be OK) and have good eyesight. As it gets closer, it gets brighter and larger, but the surface brightness doesn't change. The Andromeda galaxy will remain a dim feature in the sky. At some point, tidal forces will warp and disrupt the disks of the galaxies, so that bright band of the Milky Way will get diluted and disappear. We can only see it now because we have a very long line of sight within the disk. At the same time, gas gets stirred up, leading to a burst in star formation and supernova rate, leading to a lot of clusters of bright stars, visible by naked eye from all over the merging galaxy pair. That could be quite spectacular, if the changes weren't so slow that you could never notice it on human timescales. PiusImpavidus (talk) 10:19, 30 December 2022 (UTC)

I have seen M31 from the outskirts of a medium-sized city. —Tamfang (talk) 18:48, 30 December 2022 (UTC)

Now, M33 is more of a challenge. I've seen it with the naked (well, bespectacled) eye in the UK a few times, but in recent decades only from decently dark sites, one of which had an astronomical observatory built on it. {The poster formerly known as 87.81.230.195} 51.194.245.235 (talk) 19:58, 30 December 2022 (UTC)

Now here's a challenge. Apparently all seven planets are visible after sunset - that's Mercury, Venus, Mars, Jupiter, Saturn, Uranus and Neptune (the last two by telescope only) though not in that order. This state of affairs will not last, because Mercury will fade in the next few days. 89.243.13.100 (talk) 21:40, 30 December 2022 (UTC)

Human extraterrestrial life?

Here's a question for you: could humans adapt to life on Mars, Europa, Enceladus, or Titan? 67.215.28.226 (talk) 20:48, 29 December 2022 (UTC)

Have humans adapted to life in the far north, does an Inuit with a nice fur coat count as adaptedas far as you are concerned? NadVolum (talk) 22:13, 29 December 2022 (UTC)@

No. I am asking without a spacesuit? 67.215.28.226 (talk) 22:18, 29 December 2022 (UTC)

Only if a massive terraforming project was undertaken. ←Baseball Bugs ^{What's up, Doc?} carrots→ 22:36, 29 December 2022 (UTC)

Okay, thank you. ;) 67.215.28.226 (talk) 22:54, 29 December 2022 (UTC)

Essentially the same question was asked earlier this month: Could humans somehow adapt to new planets / satellites (like Titan)?  --Lambiam 10:16, 30 December 2022 (UTC)

And still we are unable to answer questions here which call for speculation, not to mention the biomedical information involved. Elizium23 (talk) 02:41, 31 December 2022 (UTC)

There's no problem with discussing biology or medicine. Medical diagnosis and advice are what we avoid.  Card Zero  (talk) 03:51, 31 December 2022 (UTC)

Recent human evolution discusses some of the ways in which humans continue to adapt to their environments. If placed in an extra-terrestrial environment for many generations – in some kind of artificial habitat – humans could be expected to adapt further. Dramatic evolutionary change happens slowly, for complex organisms like humans that reproduce slowly. An adaptation such as improved tolerance for the planet's gravity, or for the Martian_soil#Dust_hazard, would take fewer millenia than a major change such as being able to breathe the atmosphere: 20 million years of hominid evolution hasn't been enough time for anything so dramatic to happen on earth, for instance there are no humans living under the sea (without the aid of equipment).  Card Zero  (talk) 05:46, 31 December 2022 (UTC)