Will the Milky Way and Andromeda Collide Despite the Expanding Universe?

In summary, the conversation discusses the collision of the Milky Way and Andromeda galaxies in 2.5 - 3 billion years, despite the fact that the universe is expanding at an accelerating rate and objects are receding from each other. It is explained that this collision is possible because some objects, like galaxies in close proximity, are gravitationally bound and not affected by the expansion. It is also mentioned that while our local group of galaxies may eventually be all we can see due to expansion, there is speculation that dark energy may weaken and allow gravity to bring everything back together. However, the speaker believes that it is safer to assume that expansion will continue.
  • #1
buddhakan
3
0
I am a molecular biologist but cosmology is my "hobby". I have some questions about some seeming inconsistencies I have heard on TV treatments of cosmological topics. Here is the first: I hear the the Milky Way and the Andromeda galaxy will collide in 2.5 - 3 billion years. If the universe is expanding at an accelerating rate, and every object in the universe is receding from every other object (which I also hear often), then how is this collision possible?
 
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  • #2
Every object is not receding from every other. Some objects are close enough together that they are gravitationally bound to each other, defeating expansion.
 
  • #3
That means our local group of galaxies will eventually be all of the universe we can see. However it remains to be seen if the expansion will continue, some are holding out that maybe dark energy will weaken at some point thus giving gravity a chance to pull everything back together. Personally I think we can only go on what we see and that is to assume expansion will continue.
 

Related to Will the Milky Way and Andromeda Collide Despite the Expanding Universe?

1. What is the expansion of the universe?

The expansion of the universe refers to the continuous increase in the distance between galaxies and other celestial bodies. This phenomenon was first observed by astronomer Edwin Hubble in the 1920s and has been confirmed by numerous studies since then.

2. How does the expansion of the universe occur?

The expansion of the universe is believed to be driven by dark energy, a mysterious force that permeates all of space and causes it to stretch at an accelerating rate. This expansion also results in the stretching of light waves, causing them to appear redder in color, known as redshift.

3. Is the expansion of the universe uniform?

No, the expansion of the universe is not uniform. It varies based on the distance between objects and the amount of dark energy present. The expansion is greater in areas with more dark energy, causing objects to move away from each other at a faster rate.

4. How does the expansion of the universe relate to the Big Bang theory?

The expansion of the universe is a key piece of evidence for the Big Bang theory. The theory states that the universe began in a highly dense and hot state and has been expanding and cooling ever since. The ongoing expansion is a result of the initial explosion of the Big Bang.

5. Will the expansion of the universe ever end?

This is still a debated topic among scientists. Some theories suggest that the expansion will continue indefinitely, while others propose that the expansion will eventually slow down and possibly reverse, leading to a "Big Crunch" where the universe collapses back in on itself. More research and observations are needed to determine the ultimate fate of the expansion of the universe.

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