Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

What's really happening here?

  1. Jun 25, 2003 #1
    If we look in the distant past we see evidence that the rate of universal expansion is increasing. If we look in the recent past we see that our own galactic cluster and many around it, including the huge Coma cluster, are headed toward a "great attractor". These are definitly opposing scenarios.

    Does the rate of expansion reverse at times?
  2. jcsd
  3. Jun 25, 2003 #2

    not all of the galaxies we observe our red shifed. local regions will clump together, but then continue to expand. the distanct past was going through a period of hyperinflation, so there was no time to have the galaxies clump together.
  4. Jun 26, 2003 #3
    Generally the Universe is expanding, but locally it might seem different because of the gravitation.
  5. Jun 26, 2003 #4


    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    There is "small-scale" (and I use that term very loosely) non-expansion if there is enough gravitational effect in a particular region (like in a galaxy or a galaxy cluster), but the overall universe is expanding.
  6. Jun 27, 2003 #5

    Ivan Seeking

    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    I have read that anti-gravity [or whatever dark energy is] dominates in the regions between galaxies. Is the nature of deep inter-galactic space fundamentally different than the space in between stars? Is this related to the distribution of dark matter?
  7. Jun 27, 2003 #6
    Firstly, they are not opposing scenarios. You're confusing the issue here - space itself is expanding. Within that expansion mass can experience velocity and mass. So in the scenario you describe, there is simply the motion of mass within expanding space.

    However, to that I should also point out that I am still very much against the "standard candle" explanation of the expansion of the universe acceleratnig. :) There are too many easily flawed assumptions involved to take the idea seriously. Unfortunately, it has fast become a paradigm in its own right. :(
  8. Jun 27, 2003 #7
    Re: Re: What's really happening here?

    First, welcome to the board and thanks for your input.

    I know about "space is expanding" and the dynamics of gravity and the universal expansion, I'm just trying to get people to ask a few questions as opposed to accepting "ober dictum". And yes, I agree that there are too many assumptions used to justify too many conclusions, especially in Cosmology where expermental data is thin and hard to come by. People don't always recognize that any hypothesis carries many often unstated assumptions.

    I beleive the road to discovery lies in asking the right question. There are usually far fewer right questions than right answers, so looking for the right answer is like looking for a needle in a haystack. But if you ask the right question the right answers will come thick and fast.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook