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Why are we crashing with Andromeda?

  1. Feb 26, 2013 #1
    If the galaxies are moving away from each other.
  2. jcsd
  3. Feb 26, 2013 #2


    Staff: Mentor

    overall the galactic trend is moving away but that doesn't mean thatindividual galaxies cant be gravitationally attracted and collide.
  4. Feb 26, 2013 #3
    I assume the Earth will be dry by them due to the swelling of the dying sun. How will future generations cope with these catastrophic events?
  5. Feb 26, 2013 #4
    We have a few things going on. All galaxies interact gravitationally with each other and rotate. Close pairs of galaxies are bound by the gravity of the dark matter surrounding them, drawing them together and resisting the expansion. As it happens, our own galaxy, the Milky Way, finds itself in a close pair having a approximation of each radial and transverse velocities, masses of both, rotational curve to be on collision using a predicting methods like newtons second law in solving a 2 body problem, timing argument and dynamical systems for simulations.
  6. Feb 26, 2013 #5
    Two cars collide in an instant. I assume this collision will take 1-2 million years. Will there be any humans left to observe this? Or should I say whatever we evolve into?

    It is hard to accept that all the cumulative knowledge of MAN will be gone.
  7. Feb 26, 2013 #6


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    When the Andromeda Galaxy and our Galaxy "collide" there will be little or no chance of our solar system hitting anything. There is an awful lot of empty space between stars! There will be global gravitational effects, but locally it won't be noticed.
  8. Feb 26, 2013 #7


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    Dearly Missed

    McCartney, mathman is right. No need to be apprehensive. But if you are interested there are large computer simulations of such events, showing short animated movies of the calculated process of meeting and merger of galaxies.

    The results can be pretty. The spiral arm structures get disrupted in a kind of splat. But that doesn't mean stars and planets BUMP. It is gravitational interaction of very large scale structures. The orbits of large assemblies of stars that were going around a center---the orbits are slowly distorted, so the overall shape of things changes (but without substantial amounts of bumping.) Tidal forces can strip some assemblies of stars off and fling bunches of them out. Galaxies can pass slowly THRU each other and almost separate and then fall back together. the results, as I recall, are pretty, but non-threatening.

    I don;t have the links but you might search with some google words like computer simulation galaxy collision, or something like that. Or just search colliding galaxy movie. If you find anything nice please share it. I would like to see the stuff again.
  9. Feb 26, 2013 #8


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    Galactic collisions rarely involve stars. Instead, the gaseous content takes the biggest hit. This promotes starburst activity, which will make things very interesting for the probable elliptical galaxy that will result from the collision.
  10. Feb 26, 2013 #9
    Wish granted
    heres one specifically on the milky way and Andomeda
    http://www.galaxydynamics.org/tflops.html [Broken]
    Last edited by a moderator: May 6, 2017
  11. Feb 27, 2013 #10
    Thanks to you and others.

    I am feeling better about this. Some readings have suggested that the sun could get thrown out or that the sun could end up way too close to the center black hole. IN other words the solar system would not be in the optimal zone.
    Last edited by a moderator: May 6, 2017
  12. Feb 27, 2013 #11


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    Andromeda is over 2 million LY away from the Milky Way. You are obsessing over less than nothing. The predicted collision won't happen for 4 billion years.
  13. Mar 9, 2013 #12
    Don’t worry. The chances of mammals reaching that point are very small.

    The following link lists some of the possible ways that the world will end before that time.

    The way things look now, I have series doubts about our species lasting even a thousand years. Think of it like that. What will the world be like one thousand years from now?

    Global warming and other environmental problems will take precedence in my value system. How can someone worry about what happens four billion years from now and not worry about what may happen in one hundred? Or in fifty?

    Life on earth started with thermophilic bacteria and it may very well end with thermophilic bacterial.
  14. Mar 9, 2013 #13
    I think we will evolve into some other species and they will talk about us as their ancestors. No different than we talking about the chimps.

    The world could end tomorrow, in a thousand years or in one million years. We don't really know. The end could very well be the malfunction of the sun. We may have to colonize one of the moons of Jupiter which may very well be much warmer by them.

    Global warming is probably better than an Ice Age.
    Last edited by a moderator: May 6, 2017
  15. Mar 9, 2013 #14
    Considering as I live in Canada maybe by the time I die I'll be living in the new tropics
  16. Mar 9, 2013 #15
    A one million year Ice Age is much worse than having to move a bit more inland after the melting of the ice caps.
  17. Mar 9, 2013 #16
    Really? Do you have any idea how much has happened in the last 4 billion years?

    The current candidate for most recent common ancestor between human beings and chimpanzees is Ardipithicus, which lived about 16 million years ago.

    So let us say 4 billion years divided by 16 million is 250. So 4 billion years is about 250 times the span that separates chimpanzees from human beings.

    The common ancestor of all animals lived on or about 700 million years ago.

    As far as the fossil evidence goes, the common ancestors of all life were bacteria. Although we can't really tell details about the bacteria, it appears that our most recent common ancestor between cyano bacteria and human beings lived about 4 billion years ago.

    Four billion years ago, even the atmosphere was different. There was no oxygen in the atmosphere.

    Out of the millions of extant species on earth, maybe about four were present about 400 million years ago. I am not even sure these are species. These may be larger taxons.

    There are very few species of animals or plants at our level of complexity that remain after 10 million years. There isn't a single species of animals that formed 550 million years ago that has remained alive to this day.

    The first of the human species seems to have evolved about 200,000 years ago. The first human-like cultures seem to have developed a mere 200,000 years ago. Every civilization that we know lasted less than 4000 years. Most only a few hundred.

    If some remnant of our genome survives 4 billion years ago, they may not see us as their ancestors any more than we see ourselves as the the descendent of extremophile bacteria.

    I am not trying to be pessimistic. Maybe some version of the human mind will exist 4 billion years from now. However, there will be a lot of trials until then. If any organism remotely analogous to us survives that long, then it will have survived numerous trials of equal intensity to the expanding sun. We probably won't be able to survive nearly that long without branching out to other star systems. In this case, we will have probably colonized several newly formed stars that could last another billion years.

    At that point, the expansion of our sun won't even appear like an inconvenience.
    Last edited: Mar 10, 2013
  18. Mar 10, 2013 #17
    That animal had to be a complex organism and somehow did not end up in a dead end road. I will say that I read somewhere that at one point the ancestor of man almost did not make it before leaving Africa.

    I guess less complex organisms can adapt with much greater facility than complex organisms, but this is applicable to short time spans.

    Humans will be no more, but hopefully we evolve. To evolve we would need an enormous amount of time, but, it is possible. Several million years is not much in relationship to the Earth's lifespan. In many ways humans are a miracle of evolution. That we got here is truly incredible and it is interesting to discuss where we are going.

    Galactic travel will always be difficult. At most when the sun swells the moons of the gas giants may be warmer and habitable. That may buy us some time before the death of the sun.
  19. Mar 10, 2013 #18
    By the time the death of the sun comes about we wouldnt even recognize the technology we could achieve by then.
    As far as global warming their are developed ways which we can feasibly remove the excess CO2 levels. One method involved lifting nutrients from
    the Ocean floor encouraging
    the growth of algea. Which like
    plants thrive on CO2. Their is
    a couple other expensive
    methods. One reason why
    those arent in operation is th
    at they are still studying the
    impact it would have. However we do have the tech to reduce CO2 levels.
    You seem to sell human ability short. We are highly adaptable. I have no doubt that one day we will leave Earth and colonize other planets. Despite all the
    challenges. Hopefully we take the lessons we leaned in Earth with us so we don't make the same mistakes.
    Given enough warning and time to prepare Mankind will survive.
  20. Mar 10, 2013 #19
    I am just talking about historical precedent. There has been no species of organism that has shown any capacity of surviving 4 billion years. Human beings are a recently evolved species that evolved about 200,000 years.

    The oceans will probably dry out within 2 billion years, with or without man-made global warming. The sun is slowly heating up right now, well before it turns into a red-giant. It has been warming up for more than 5 billion years. An unexpected asteroid just hit earth, killing a few people and doing a lot of damage. We know there are larger asteroids out there. We know that calderas such as opened up at the PT extinction are still a possibility.

    The question was, "What will future generations do to meet the challenge of the sun turning into a red giant." Well, you just made one of many important points. Strange that you don't connect the statements that you make.

    In order to survive some of the other challenges that the human-something will face, humans will have to colonize other planets. "We" may have to colonize other planets just to survive the drying out of the oceans and the loss of our atmosphere. Once we colonize other planets, the expanding sun won't be such a big problem. Even the "humans" still on earth will just have to pick up stakes and leave.

    You pointed out that if we survive in recognizable form for four billion years, we will have a technology that we can't even imagine today. If we can't imagine it, then we can't even conjecture about what we will do when the sun expands.

    In fact, the question implies that the expanding sun will be a problem. If we are in outer space already, I can't see why it would even be a serious problem.

    What we do when the sun expands, if we get there at all, will be highly contingent on what solutions we find to the challenges in between.

    Sorry. I just noticed that this is the astronomy section not the science fiction section. Speculation like this is a little beyond astronomy or even cosmology. By your definitions, one can't even imagine the solutions. So I think that I will stop here.
  21. Mar 10, 2013 #20
    The gravitational effects will result in starbursts followed by a firework of supernovae. Oort clouds will be destabilized resulting in an increased number of comets. Planetary systems will cross protostellar clouds, nebulae or Oort clouds of other stars. The central black holes will cross areas with high matter density turning temporarily into quasars. Finally the black holes will merge.

    I think this would be noticed locally if there is still somebody left.
  22. Mar 10, 2013 #21
    From what I have read humans will develop some sort of technology to deflect solar energy and this will be deployed to the entire upper atmosphere. This will help when the sun warms up even more, but it will be band-aid treatment.

    Ideally some of the moons of the gas giant planets are available and will be much warmer when the sun gets really hot. However, eventually andromeda will come and the moons around the giant planest will not be safe.

    Sadly interstellar travel with not be of any help at that time. Intergalactic travel will probably always be out of the question.

    We are doomed!
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