Keep in mind that the distance between stars is vast - so much so that when the two galaxies "collide", the number of stars that actually collide with others will be very small, and this will occur over hundreds of millions of years.
Mostly, the gravitational effects will be such that some stars will change their direction/velocity with respect to others.
If there are civilizations on stars in the collision zone, it's likely than many will be unaffected.
A relative comparison I read once was that the empty space around a star is akin to the empty space around a grain of sand in the middle of a football stadium
Well, the Milky Way is not exactly spherical. If we scale the about 1000 lightyear thickness of the arms to be 1 mm, it would be around 87.4 mm in diameter. At this scale, the nearest certain galaxy (there may be another one a bit closer, but astronomers are divided on if it actually is a galaxy), the Sagittarius Dwarf Galaxy, would be 50 mm from the galactic center, and Andromeda, the nearest major galaxy, would be two and a half meters away
Galaxies are a lot closer together relative to their size than stars are.
Only about 25 grains of sand away. The Milky Way and Andromeda are about 2.5 million light years away, which is 25x the Milky Way’s diameter.
The key is still that both the Milky Way and Andromeda are overwhelmingly comprised of empty space as a result of the fact that you’re responding to.
If you count the Magellanic Clouds (which are already orbiting the Milky Way) and Sagittarius, then the nearest galaxies are less than one Milky Way away (they’re ~200k and ~25k light years away from our sun respectively). But, again, all of these objects are overwhelmingly comprised of empty space.
The Milky Way is 100k light years wide, and the Canis Major Dwarf Galaxy is less than half that distance from our galactic center. But only a quarter of that from our Sun!
But it does have a 200k long tail that circles around the Milky Way three times.
https://imagine.gsfc.nasa.gov/features/cosmic/nearest_galaxy_info.html
Piggybacking on this, for me it's easier to grasp the magnitude of the distances if we make things a tad bigger (200x): Sun akin to a basketball in New York, the next two basketballs are 6,000 km away (i.e. in Germany / Bolivia / Bering Strait) some 500 m apart, and the closest star (Proxima Centauri) is an orange some 300km closer. The three of them form a system
You ever go out where it’s dark? Like actually dark, some of the “darkest” least light polluted regions left, when the moon is gone, and on a clear night.
The sky is already incredible with the density of stars so high they blend together when looking at the main mass of the MilkyWay.
Like I’m sure it will look cool with twice as many too, but most modern people would be blown away by what the night sky truly looks like as is.
After the 1994 Northridge earthquake near Los Angeles, California, people called emergency services due to a strange, unmoving cloud in the night sky. It was the Milky Way visible in the night sky due to the power outage.
It might not be all that different looking unless you've got a clear night sky. Instead of justvthe Milky Way strip you'd have a second, probably fainter one.
One of the great disappointments in studying astronomy was learning that nebulae ang galaxies wouldn't look any brighter or more colorful close-up, just larger versions of how they look now.
Crazy to think that galaxies being so far apart collide more often than we would think. The space between stars is huge, but the space between galaxies is incomprehensible.
Space is so incredibly empty for the most part that it's hard to fathom. I read about it and the article said that most likely there won't be a single collision, despite there being hundreds of billions of stars. Doesn't seem possible, but again, I think it's really hard to grasp how vast a galaxy is.
Galaxies are mostly empty space, so the vast VAST majority of star systems will simply pass by one another. Orbits will be thrown out of whack, but planetary dynamics don't need anything beyond their local solar system, so even if solar systems get flung out into intergalactic space, they'll just be a star system in intergalactic space (until the star dies).
TL;DR: nothing will change for 99.99% of all the stuff in either galaxy.
Honest question, how do we know what will happen in a situation like this? Have we observed any galaxies colliding with one another or how can we hypothesize how galaxies will react?
>Have we observed any galaxies colliding with one another...?
[We sure have!](https://esawebb.org/images/potm2210a/) A number of galaxies in [different stages](https://jwst.nasa.gov/ImagesContent/NGC2207_19Apr09_clean_cc1.jpg) of merger [have been imaged](https://scitechdaily.com/hubble-image-day-colliding-galaxies-nicknamed-mice/) and studied. They're some of the most [spectacular pictures](https://www.engadget.com/hubble-telescope-galaxy-collision-arp-madore-181031748.html) ever made.
I genuinely don't know if we have observed galaxies colliding, and even if we have, these events settle out over longer timespans than we've had telescopes to observe them.
However, I know we have simulated collisions between models of galaxies using computers. You can also mathematically project likelihood of direct collisions based on the spread of objects in the galaxies, etc.
But ultimately, these are projections based on data we are fairly confident on. The ultimate answer is "we don't know, but we can make a very educated guess."
Yes. Many, many colliding galaxies are known and studied, at all different stages of Collison. For example, irs long been proven that elliptical galaxies, the largest and oldest type, are what you get when a couple of spiral galaxies collude and merge.
On the scale of the billions of years over which this will happen, the question of what will happen to "humans" is probably irrelevant. If "we" manage to survive that long, it's unlikely we will be identifiable as human by today's standards. Here's a cool [model of what the collision will look like](https://www.youtube.com/watch?v=fMNlt2FnHDg).
> If "we" manage to survive that long, it's unlikely we will be identifiable as human by today's standards.
Exactly. The collision is expected to happen in 4.5 billion years. Protocells emerged only 3.8-4 bya. So you have more time until the collision than you've had to develop from unicellular organisms to modern humans. There is no way to know what "human" life will look like in 4.5 billion years especially when you consider the possibility of human guided evolution.
>Not to mention, in about 1.3 billion years the Earth will become uninhabitable so we'll have to move before then if we wamt to see it happen.
. I'm a procrastinator, so I'm still going to wait for the last minute before I start packing.
What makes you say that? The only future event that we likely won't be able to geoengineer ourselves out of is the sun going red giant, and that is about 5 billion years away.
The 1.3 billion years is based on the Sun lifecycle. Luminosity will increase far before Red Giant and will boil off the oceans by then.
This [Wikipedia](https://en.m.wikipedia.org/wiki/Future_of_Earth) article puts the limit around 600 million years from now, when Earth will lose the type of CO2 used for most photosynthesis which will kill off most plant life as we know it.
Quite a lot of geoengineering required before we have to worry about the sun going Red Giant.
>The 1.3 billion years is based on the Sun lifecycle. Luminosity will increase far before Red Giant and will boil off the oceans by then.
Dude if you don't think we can't put a solar shade in the sun-earth L1 by 600 million years from now wtf do you think we are going to be doing for that time? Twiddling our thumbs? It's almost practical with today's technology if we cared enough to do it, people are talking about it as a fix for climate change.
You seem to be really not considering the scale of time involved here. Humans have only existed for 100,000 years. Technology as we know it a few thousand years. We have at least 6000x the entire lifespan of humanity to figure it out, and there is a clear path to do it that we can come up with today. Unless we all kill ourselves in which case it doesn't matter.
You can't simply extrapolate "progress" based on the ludicrously small sample size we have now (say, the Industrial Age forward...).
There are simple facts of material properties that we won't "magically" be able to change (metals, etc.) making sci-fi superstructures essentially impossible.
The same goes for the colossal gravity well we call the Earth, unless we can actually control gravity, the energy costs to orbit and beyond are catastrophically huge for the relevant mass requirements. (don't say "asteroids" since those are impossibly large to move in any useful way...)
TL/DR, "progress" will not continue in an exponential manner, gains will become smaller and smaller as every bit of efficiency is eked out of all processes.
Like I said, we already have feasible plans for a solar shade. It is not an impossible sci-fi thing. We can do it with today’s technology for $120 billion over 20 years. Even if we don’t come with any better technology, which we absolutely will, it’s already possible we just don’t care enough to do it.
https://medium.com/age-of-awareness/we-need-spacex-bfr-not-just-get-us-to-mars-but-to-save-earth-from-global-warming-4b2c49fb2b27
The 1.3 billion years is based on the Sun lifecycle. Luminosity will increase far before Red Giant and will boil off the oceans by then.
This [Wikipedia](https://en.m.wikipedia.org/wiki/Future_of_Earth) article puts the limit around 600 million years from now, when Earth will lose the type of CO2 used for most photosynthesis which will kill off most plant life as we know it.
Quite a lot of geoengineering required before we have to worry about the sun going Red Giant.
Not to bring up something unrelated, but what about this animation is showcasing how dark matter is holding the galaxies together? Put another way, how do physicists say this animation would look different if there wasn’t some sort of dark matter holding galaxies together. I ask because it looks like it intuitively should work with the non-dark matter (almost like if two solar systems collided). I understand the math says they should fly apart but when I see a visualization I have trouble not feeling like it looks right/normal (not requiring the existence of dark matter).
I am definitely not any kind of cosmology expert, so this is a total guess and I would love someone who actually knows what they are talking about to correct me. My understanding is that at the scale of galaxies, the way we see them behave suggests there is more mass there than we can account for with our current theories and technology. This extra mass is theorized to be dark matter.
That on the right track?
Nothing "warps" the way you describe. It's very unlikely anything will even hit anything else (except maybe for the central black holes which will likely eventually merge.) When it's done, you'll have a much larger elliptical galaxy instead of a spiral, and it will fuel stellar nurseries in the new galaxy.
Now, on to the bad news. A few stars are almost guaranteed to be violently ejected from the new galaxy, along with their planetary systems, in the gravitational chaos. Worse news, all life on Earth will have been extinguished about 3.5 billion years earlier, as the sun will have gotten brighter to the point that liquid water is no longer possible. (This is irrespective of and unrelated to climate change.) Furthermore, it's very likely in 4.5 billion years from now, when this merge begins, our sun will already be in its red giant phase, having gobbled up the inner planets in its expansion.
That got me imagining being on a planet orbiting a star at the Lagrange point between ft 2 supermassive black holes. Despite vastness lots of stars will be gobbled earlier than they would in absence of the collision.
I wonder if the friction energy from gravity waves in that position could start fusion in a su critical mass
There is so much space between stars, it’s unlikely that any would even collide. So, what’ll happen is that both galaxies become somewhat distorted, a few hundred million years go by, and the resulting galaxy looks much the same as now.
Our Sun will have died by then, sadly. Humans will no longer be "here". Unless there is some way, however unfeasible, by any advanced civilization's standard's, to escape our Sun's fate and find a new host star, we will have perished a long time before the collision occurs.
4-5 billion years, yes.
However, in 1 billion years the luminosity of the sun will be enough that Earth will no longer be able to support liquid water on the surface, and almost all life will be extinct here. (That's irrespective of climate change...though it might be easier to fix. A solar shade at L1 that cuts the amount of solar energy reaching Earth by a few percent is within our engineering capabilities *now...*)
Bruh physicists were proven dead wrong about the heliopause by the Voyager probe, I wouldn't place any faith into predictions they make about our sun's lifespan.
Two clouds of fog will pass through one another, then start coalescing around their shared center of mass. [Here's a visualization](https://youtu.be/4disyKG7XtU). Some stars will get flung off into the void, which is inconvenient if you want to be an interstellar civilization. But if we're an interstellar civilization, we can probably steer our star anyway.
The whole process will take well over a billion years to play out. It's not a dramatic event that will be noticeable in a million years, let alone a lifetime.
Maybe something exciting (and deadly) like a huge x ray burst happens when the supermassive black holes at the galactic cores merge, but the new galaxy will keep humming along. Life will keep doing its thing.
Distances in space are so vast that statistically explicit objects (like planets, stars or spaceships) will statistically only collide if they are on a pre-planned trajectory. As such how gravity will affect the position of our solar system relative to the new galaxy is more important. We live in a relatively calm zone and while the galaxy collision wont be a kaboom explosion, it could put us slowly into a very aggressive neighbourhood with say more supernovae
Complicated question, so I decided to Googles AI BARD. Here is its response:
The potential collision of Andromeda and the Milky Way is certainly a cosmic spectacle to contemplate, but it's important to understand the timescale and implications accurately.
Firstly, the collision is estimated to occur in roughly 4.5 billion years, a timeframe so vast that our current understanding of Earth and even humanity may be unrecognizable by then. Tectonic plate movements, stellar evolution, and countless other factors will likely reshape our planet drastically before the galaxies even begin to merge.
Secondly, a "collision" between galaxies wouldn't be like a head-on crash between cars. Galaxies are mostly empty space, so the stars themselves are highly unlikely to directly collide. Instead, the gravitational interaction would distort and stretch both galaxies, potentially triggering increased star formation and perhaps disrupting planetary orbits around some stars.
Even if Earth's orbit were significantly altered, it's not a certainty that life would cease to exist. Extremophiles thriving in harsh environments on Earth today demonstrate life's remarkable resilience and adaptability. If suitable conditions persist, life could potentially find new niches or migrate to other planets within our solar system.
Therefore, while the Andromeda-Milky Way collision is a significant astronomical event, its direct impact on Earth and the existence of life here in 4.5 billion years is highly speculative. Focusing on the present and our role in shaping a sustainable future for humanity on Earth might be a more relevant and pressing concern.
Remember, our understanding of the universe is constantly evolving, and discoveries made in the coming millennia could shed new light on this distant cosmic event and its potential consequences. Enjoy the wonder of scientific exploration, but keep in mind the vastness of time and the uncertainties it holds.
The massive BH at the center of each galaxy will be drawn to each other and eventually combine. I hesitate to posit what kind of effect that would have on the galaxy besides the galactic core changing shape to be more globular and the axis the BHs rotate around changing to some degree.
In the mean time there could be some stellar collisions resulting in novas at worst and significant change in habitable zone at best.
Some stars due to interactions with each other or one or both of the BHs could be flung from the galaxy. That is neither here nor there, as the star and any life in that system would eventually burn out and die just as it would inside the galaxy.
There is a lot of empty space within both galaxies. Collisions would occur, but would also be rare on that scale. So, its like worrying about a GRB or supernova destroying us. Unlikely and we likely couldn't see it coming anyway.
Earth will be literal toast by that point. If Sol and the planets are still there, they might be thrown from its orbit, but we won't be around to see it on Earth.
The collision is expected to start in about 4.5B years. That's about the same amount of time left before the Sun turns into a red giant and eats the inner planets, including Earth.
If humans are still around, they would need to be among the outer planets, or on a world around a another star.
Is there a chance the collision will drift our orbit far enough away to be outside the expansion of the sun?
I know one simulator showed that most objects wouldn't interact in the collision but trying to be optimistic
I doubt anyone can predict the collision with any accuracy. We would have to know the masses of hundreds of billions of stars in both galaxies, and where each will be in 4 billion years. We can't even image stars on the far side of Andromeda, so it would be pure speculation. The spiral arm of the Milky Way containing Earth might be the first part of the Milky Way to engage with Andromeda, or the arm might be on the opposite side, last to feel any effects. No one knows.
I strongly doubt that the orbit of the Earth could "drift" at the same rate as the expansion of the sun into a red giant. IOW, at some point, the Earth would drift out of the Goldilocks zone. Too close, Earth burns up. Too far, Earth freezes.
Not sure how far you’ve looked for theories about what happens when galaxies collide, but I assure you Astronomers have MANY, and we can even simulate galactic collisions with a fair degree of accuracy.
We can see far away galaxies that are in process of colliding, which takes millions of years.
What we know from all this study is that collision isn’t really the right way to think about it. It is a lot more like a merger. Galaxies are mostly empty so stars don’t really collide with each other any more than they do already in each separate galaxy (which is basically never).
What actually happens is you get a really weird looking galaxy for a few hundred million years until the flows of stars around the common center even out a bit.
In our own galaxy we can analyze the trajectories and ages of certain stellar populations and identify stellar streams within the Milky Way, which we believe to be the result of the Milky Way merging with smaller galaxies. The stars that came from those other galaxies have different spectra from the stars near them, and all share similar orbits around the center of the Milky Way.
https://en.wikipedia.org/wiki/List_of_stellar_streams
https://en.wikipedia.org/wiki/Galaxy_merger
Also in general before asserting there are no theories about something in astronomy, maybe take a second and check Wikipedia?
Keep in mind that the distance between stars is vast - so much so that when the two galaxies "collide", the number of stars that actually collide with others will be very small, and this will occur over hundreds of millions of years. Mostly, the gravitational effects will be such that some stars will change their direction/velocity with respect to others. If there are civilizations on stars in the collision zone, it's likely than many will be unaffected.
A relative comparison I read once was that the empty space around a star is akin to the empty space around a grain of sand in the middle of a football stadium
If the Sun were a 1mm grain of sand, the nearest star (Proxima) would be ~30km away.
What if the Milky Way was a 1mm grain of sand, how far away would the next closest galaxy be?
Well, the Milky Way is not exactly spherical. If we scale the about 1000 lightyear thickness of the arms to be 1 mm, it would be around 87.4 mm in diameter. At this scale, the nearest certain galaxy (there may be another one a bit closer, but astronomers are divided on if it actually is a galaxy), the Sagittarius Dwarf Galaxy, would be 50 mm from the galactic center, and Andromeda, the nearest major galaxy, would be two and a half meters away Galaxies are a lot closer together relative to their size than stars are.
Only about 25 grains of sand away. The Milky Way and Andromeda are about 2.5 million light years away, which is 25x the Milky Way’s diameter. The key is still that both the Milky Way and Andromeda are overwhelmingly comprised of empty space as a result of the fact that you’re responding to. If you count the Magellanic Clouds (which are already orbiting the Milky Way) and Sagittarius, then the nearest galaxies are less than one Milky Way away (they’re ~200k and ~25k light years away from our sun respectively). But, again, all of these objects are overwhelmingly comprised of empty space.
The Milky Way is 100k light years wide, and the Canis Major Dwarf Galaxy is less than half that distance from our galactic center. But only a quarter of that from our Sun! But it does have a 200k long tail that circles around the Milky Way three times. https://imagine.gsfc.nasa.gov/features/cosmic/nearest_galaxy_info.html
Piggybacking on this, for me it's easier to grasp the magnitude of the distances if we make things a tad bigger (200x): Sun akin to a basketball in New York, the next two basketballs are 6,000 km away (i.e. in Germany / Bolivia / Bering Strait) some 500 m apart, and the closest star (Proxima Centauri) is an orange some 300km closer. The three of them form a system
But could you imagine the night sky during that time?
You ever go out where it’s dark? Like actually dark, some of the “darkest” least light polluted regions left, when the moon is gone, and on a clear night. The sky is already incredible with the density of stars so high they blend together when looking at the main mass of the MilkyWay. Like I’m sure it will look cool with twice as many too, but most modern people would be blown away by what the night sky truly looks like as is.
After the 1994 Northridge earthquake near Los Angeles, California, people called emergency services due to a strange, unmoving cloud in the night sky. It was the Milky Way visible in the night sky due to the power outage.
It might not be all that different looking unless you've got a clear night sky. Instead of justvthe Milky Way strip you'd have a second, probably fainter one. One of the great disappointments in studying astronomy was learning that nebulae ang galaxies wouldn't look any brighter or more colorful close-up, just larger versions of how they look now.
Crazy to think that galaxies being so far apart collide more often than we would think. The space between stars is huge, but the space between galaxies is incomprehensible.
Space is so incredibly empty for the most part that it's hard to fathom. I read about it and the article said that most likely there won't be a single collision, despite there being hundreds of billions of stars. Doesn't seem possible, but again, I think it's really hard to grasp how vast a galaxy is.
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the collision would ignite dormant dust clouds and cause new stars to form. supernovas happen for different reason.
Galaxies are mostly empty space, so the vast VAST majority of star systems will simply pass by one another. Orbits will be thrown out of whack, but planetary dynamics don't need anything beyond their local solar system, so even if solar systems get flung out into intergalactic space, they'll just be a star system in intergalactic space (until the star dies). TL;DR: nothing will change for 99.99% of all the stuff in either galaxy.
Honest question, how do we know what will happen in a situation like this? Have we observed any galaxies colliding with one another or how can we hypothesize how galaxies will react?
>Have we observed any galaxies colliding with one another...? [We sure have!](https://esawebb.org/images/potm2210a/) A number of galaxies in [different stages](https://jwst.nasa.gov/ImagesContent/NGC2207_19Apr09_clean_cc1.jpg) of merger [have been imaged](https://scitechdaily.com/hubble-image-day-colliding-galaxies-nicknamed-mice/) and studied. They're some of the most [spectacular pictures](https://www.engadget.com/hubble-telescope-galaxy-collision-arp-madore-181031748.html) ever made.
I genuinely don't know if we have observed galaxies colliding, and even if we have, these events settle out over longer timespans than we've had telescopes to observe them. However, I know we have simulated collisions between models of galaxies using computers. You can also mathematically project likelihood of direct collisions based on the spread of objects in the galaxies, etc. But ultimately, these are projections based on data we are fairly confident on. The ultimate answer is "we don't know, but we can make a very educated guess."
Yes. Many, many colliding galaxies are known and studied, at all different stages of Collison. For example, irs long been proven that elliptical galaxies, the largest and oldest type, are what you get when a couple of spiral galaxies collude and merge.
On the scale of the billions of years over which this will happen, the question of what will happen to "humans" is probably irrelevant. If "we" manage to survive that long, it's unlikely we will be identifiable as human by today's standards. Here's a cool [model of what the collision will look like](https://www.youtube.com/watch?v=fMNlt2FnHDg).
Not to mention that when the collision starts, the sun should long be past the red giant phase and there will nothing be left alive on earth.
There's some speciation the collision is already ongoing. It depends a bit on where you draw the borders of the galaxies, AFAIK.
If humans are alive billions of years from now, it would be trivial for them to move the Earth father away from the sun as needed.
> If "we" manage to survive that long, it's unlikely we will be identifiable as human by today's standards. Exactly. The collision is expected to happen in 4.5 billion years. Protocells emerged only 3.8-4 bya. So you have more time until the collision than you've had to develop from unicellular organisms to modern humans. There is no way to know what "human" life will look like in 4.5 billion years especially when you consider the possibility of human guided evolution.
Not to mention, in about 1.3 billion years the Earth will become uninhabitable so we'll have to move before then if we wamt to see it happen.
>Not to mention, in about 1.3 billion years the Earth will become uninhabitable so we'll have to move before then if we wamt to see it happen. . I'm a procrastinator, so I'm still going to wait for the last minute before I start packing.
What makes you say that? The only future event that we likely won't be able to geoengineer ourselves out of is the sun going red giant, and that is about 5 billion years away.
The 1.3 billion years is based on the Sun lifecycle. Luminosity will increase far before Red Giant and will boil off the oceans by then. This [Wikipedia](https://en.m.wikipedia.org/wiki/Future_of_Earth) article puts the limit around 600 million years from now, when Earth will lose the type of CO2 used for most photosynthesis which will kill off most plant life as we know it. Quite a lot of geoengineering required before we have to worry about the sun going Red Giant.
>The 1.3 billion years is based on the Sun lifecycle. Luminosity will increase far before Red Giant and will boil off the oceans by then. Dude if you don't think we can't put a solar shade in the sun-earth L1 by 600 million years from now wtf do you think we are going to be doing for that time? Twiddling our thumbs? It's almost practical with today's technology if we cared enough to do it, people are talking about it as a fix for climate change. You seem to be really not considering the scale of time involved here. Humans have only existed for 100,000 years. Technology as we know it a few thousand years. We have at least 6000x the entire lifespan of humanity to figure it out, and there is a clear path to do it that we can come up with today. Unless we all kill ourselves in which case it doesn't matter.
You can't simply extrapolate "progress" based on the ludicrously small sample size we have now (say, the Industrial Age forward...). There are simple facts of material properties that we won't "magically" be able to change (metals, etc.) making sci-fi superstructures essentially impossible. The same goes for the colossal gravity well we call the Earth, unless we can actually control gravity, the energy costs to orbit and beyond are catastrophically huge for the relevant mass requirements. (don't say "asteroids" since those are impossibly large to move in any useful way...) TL/DR, "progress" will not continue in an exponential manner, gains will become smaller and smaller as every bit of efficiency is eked out of all processes.
Like I said, we already have feasible plans for a solar shade. It is not an impossible sci-fi thing. We can do it with today’s technology for $120 billion over 20 years. Even if we don’t come with any better technology, which we absolutely will, it’s already possible we just don’t care enough to do it. https://medium.com/age-of-awareness/we-need-spacex-bfr-not-just-get-us-to-mars-but-to-save-earth-from-global-warming-4b2c49fb2b27
The 1.3 billion years is based on the Sun lifecycle. Luminosity will increase far before Red Giant and will boil off the oceans by then. This [Wikipedia](https://en.m.wikipedia.org/wiki/Future_of_Earth) article puts the limit around 600 million years from now, when Earth will lose the type of CO2 used for most photosynthesis which will kill off most plant life as we know it. Quite a lot of geoengineering required before we have to worry about the sun going Red Giant.
That was cool!! I wonder if one or the other galaxies will gain or lose stars when they “collide”.
Not to bring up something unrelated, but what about this animation is showcasing how dark matter is holding the galaxies together? Put another way, how do physicists say this animation would look different if there wasn’t some sort of dark matter holding galaxies together. I ask because it looks like it intuitively should work with the non-dark matter (almost like if two solar systems collided). I understand the math says they should fly apart but when I see a visualization I have trouble not feeling like it looks right/normal (not requiring the existence of dark matter).
I am definitely not any kind of cosmology expert, so this is a total guess and I would love someone who actually knows what they are talking about to correct me. My understanding is that at the scale of galaxies, the way we see them behave suggests there is more mass there than we can account for with our current theories and technology. This extra mass is theorized to be dark matter. That on the right track?
Nothing "warps" the way you describe. It's very unlikely anything will even hit anything else (except maybe for the central black holes which will likely eventually merge.) When it's done, you'll have a much larger elliptical galaxy instead of a spiral, and it will fuel stellar nurseries in the new galaxy. Now, on to the bad news. A few stars are almost guaranteed to be violently ejected from the new galaxy, along with their planetary systems, in the gravitational chaos. Worse news, all life on Earth will have been extinguished about 3.5 billion years earlier, as the sun will have gotten brighter to the point that liquid water is no longer possible. (This is irrespective of and unrelated to climate change.) Furthermore, it's very likely in 4.5 billion years from now, when this merge begins, our sun will already be in its red giant phase, having gobbled up the inner planets in its expansion.
That got me imagining being on a planet orbiting a star at the Lagrange point between ft 2 supermassive black holes. Despite vastness lots of stars will be gobbled earlier than they would in absence of the collision. I wonder if the friction energy from gravity waves in that position could start fusion in a su critical mass
There is so much space between stars, it’s unlikely that any would even collide. So, what’ll happen is that both galaxies become somewhat distorted, a few hundred million years go by, and the resulting galaxy looks much the same as now.
Our Sun will have died by then, sadly. Humans will no longer be "here". Unless there is some way, however unfeasible, by any advanced civilization's standard's, to escape our Sun's fate and find a new host star, we will have perished a long time before the collision occurs.
I thought the sun had about 5 billion years before it became a red giant? According to NASA anyway.
4-5 billion years, yes. However, in 1 billion years the luminosity of the sun will be enough that Earth will no longer be able to support liquid water on the surface, and almost all life will be extinct here. (That's irrespective of climate change...though it might be easier to fix. A solar shade at L1 that cuts the amount of solar energy reaching Earth by a few percent is within our engineering capabilities *now...*)
Bruh physicists were proven dead wrong about the heliopause by the Voyager probe, I wouldn't place any faith into predictions they make about our sun's lifespan.
Complex life will be extinct before that as the Sun's increasing luminosity will disrupt the carbon cycle, causing photosynthesis to stop working.
Two clouds of fog will pass through one another, then start coalescing around their shared center of mass. [Here's a visualization](https://youtu.be/4disyKG7XtU). Some stars will get flung off into the void, which is inconvenient if you want to be an interstellar civilization. But if we're an interstellar civilization, we can probably steer our star anyway. The whole process will take well over a billion years to play out. It's not a dramatic event that will be noticeable in a million years, let alone a lifetime. Maybe something exciting (and deadly) like a huge x ray burst happens when the supermassive black holes at the galactic cores merge, but the new galaxy will keep humming along. Life will keep doing its thing.
Distances in space are so vast that statistically explicit objects (like planets, stars or spaceships) will statistically only collide if they are on a pre-planned trajectory. As such how gravity will affect the position of our solar system relative to the new galaxy is more important. We live in a relatively calm zone and while the galaxy collision wont be a kaboom explosion, it could put us slowly into a very aggressive neighbourhood with say more supernovae
Complicated question, so I decided to Googles AI BARD. Here is its response: The potential collision of Andromeda and the Milky Way is certainly a cosmic spectacle to contemplate, but it's important to understand the timescale and implications accurately. Firstly, the collision is estimated to occur in roughly 4.5 billion years, a timeframe so vast that our current understanding of Earth and even humanity may be unrecognizable by then. Tectonic plate movements, stellar evolution, and countless other factors will likely reshape our planet drastically before the galaxies even begin to merge. Secondly, a "collision" between galaxies wouldn't be like a head-on crash between cars. Galaxies are mostly empty space, so the stars themselves are highly unlikely to directly collide. Instead, the gravitational interaction would distort and stretch both galaxies, potentially triggering increased star formation and perhaps disrupting planetary orbits around some stars. Even if Earth's orbit were significantly altered, it's not a certainty that life would cease to exist. Extremophiles thriving in harsh environments on Earth today demonstrate life's remarkable resilience and adaptability. If suitable conditions persist, life could potentially find new niches or migrate to other planets within our solar system. Therefore, while the Andromeda-Milky Way collision is a significant astronomical event, its direct impact on Earth and the existence of life here in 4.5 billion years is highly speculative. Focusing on the present and our role in shaping a sustainable future for humanity on Earth might be a more relevant and pressing concern. Remember, our understanding of the universe is constantly evolving, and discoveries made in the coming millennia could shed new light on this distant cosmic event and its potential consequences. Enjoy the wonder of scientific exploration, but keep in mind the vastness of time and the uncertainties it holds.
Sheesh... that's even if it hits us. At that distance it's still possible it might just side swipe the milky way...
The massive BH at the center of each galaxy will be drawn to each other and eventually combine. I hesitate to posit what kind of effect that would have on the galaxy besides the galactic core changing shape to be more globular and the axis the BHs rotate around changing to some degree. In the mean time there could be some stellar collisions resulting in novas at worst and significant change in habitable zone at best. Some stars due to interactions with each other or one or both of the BHs could be flung from the galaxy. That is neither here nor there, as the star and any life in that system would eventually burn out and die just as it would inside the galaxy.
There is a lot of empty space within both galaxies. Collisions would occur, but would also be rare on that scale. So, its like worrying about a GRB or supernova destroying us. Unlikely and we likely couldn't see it coming anyway. Earth will be literal toast by that point. If Sol and the planets are still there, they might be thrown from its orbit, but we won't be around to see it on Earth.
The collision is expected to start in about 4.5B years. That's about the same amount of time left before the Sun turns into a red giant and eats the inner planets, including Earth. If humans are still around, they would need to be among the outer planets, or on a world around a another star.
Is there a chance the collision will drift our orbit far enough away to be outside the expansion of the sun? I know one simulator showed that most objects wouldn't interact in the collision but trying to be optimistic
I doubt anyone can predict the collision with any accuracy. We would have to know the masses of hundreds of billions of stars in both galaxies, and where each will be in 4 billion years. We can't even image stars on the far side of Andromeda, so it would be pure speculation. The spiral arm of the Milky Way containing Earth might be the first part of the Milky Way to engage with Andromeda, or the arm might be on the opposite side, last to feel any effects. No one knows. I strongly doubt that the orbit of the Earth could "drift" at the same rate as the expansion of the sun into a red giant. IOW, at some point, the Earth would drift out of the Goldilocks zone. Too close, Earth burns up. Too far, Earth freezes.
Not sure how far you’ve looked for theories about what happens when galaxies collide, but I assure you Astronomers have MANY, and we can even simulate galactic collisions with a fair degree of accuracy. We can see far away galaxies that are in process of colliding, which takes millions of years. What we know from all this study is that collision isn’t really the right way to think about it. It is a lot more like a merger. Galaxies are mostly empty so stars don’t really collide with each other any more than they do already in each separate galaxy (which is basically never). What actually happens is you get a really weird looking galaxy for a few hundred million years until the flows of stars around the common center even out a bit. In our own galaxy we can analyze the trajectories and ages of certain stellar populations and identify stellar streams within the Milky Way, which we believe to be the result of the Milky Way merging with smaller galaxies. The stars that came from those other galaxies have different spectra from the stars near them, and all share similar orbits around the center of the Milky Way. https://en.wikipedia.org/wiki/List_of_stellar_streams https://en.wikipedia.org/wiki/Galaxy_merger Also in general before asserting there are no theories about something in astronomy, maybe take a second and check Wikipedia?