Exploring the Expansion and Convergence of the Universe: A Scientific Discussion

In summary, the conversation discusses the possibility of the expansion rate of the universe being independent from the expansion rate of matter within it. The concept of local clumping is also mentioned as a possible explanation for this phenomenon, but it is unlikely due to the vastness of the observable universe and the small speeds involved in local clumping. The conversation also touches on the idea of expanding space and its role in solving the problem of a special location in the universe.
  • #1
Glenn
Hi,
I have read a bit about open, closed, and flat universes, Hubbles Constant, the accellerating universe, big bag, big cruch, etc...

Is it possible that the expansion rate (+ or -) of the universe might be independant of the expansion rate (+ or -) of the matter within it?

Is it possible that the universe might continute to expand while the matter within it might start to converge under the force of gravity?

Have these options been explored?

-Glenn
 
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  • #2
Before anyone could explore it you would have to define how you distinguish between "the expansion of the universe" and "the expansion of the matter in it".
 
  • #3
Cosmological models with expanding space in which the matter isn't just "carried along with the space" aren't very easy to write down. You can't really construct a homogeneous and istotropic universe in which you have some preferred cosmological frame that most of the matter in the universe is moving greatly with respect to.

Think in terms of matter particles moving around on the surface of a balloon: how can the matter have no preferred locations or directions of motion without the average motion across the balloon's surface being zero?

You could construct a solution in which matter is all expanding from or collapsing toward some particular point on the balloon's surface, but that would violate the cosmological principle -- there would be a special location in the universe (that we would have to just happen to be located at). That's the kind of problem that expanding space was supposed to solve in the first place.

In any case, I would guess that the luminosity-redshift relations in such as scenario would differ from conventional Big Bang predictions, but I don't know if anyone has ever bothered to work it out.
 
  • #4
Originally posted by Glenn


Is it possible that the universe might continute to expand while the matter within it might start to converge under the force of gravity?

local clumping is always a possibility

(you know about the Great Attractor in the hydra-centaurus direction, towards which the virgo cluster and its hangers-on are falling-----the speeds involved are on the ordr of 300 km/s or a THOUSANDTH of c)

however it is not hard to see that any particular local clumping can never involve more than a tiny fraction of the galaxies in the observable universe--just by a practical comparison of speeds

first of all, the great bulk of the observable is at redshift greater than 2----to take a random cutoff for calculation purposes (you probably know that a quasar has been observed with redshift 6.4 and the CMB has redshift 1100, so in the big picture 2 is a small redshift)

anything with cosmological redshift of 2 or more is in a part of space which is receding from us at a speed greater than c

(for an online calculator that gives the recessionspeeds for various redshifts, google "Siobahn Morgan" and find her astronomy course materials, the current Fall 2003 semester)

maybe largescale clumping is not a theoretical impossibility but the usual falling speeds (a thousandth) are just too tiny to
counteract the typical recession speeds (several times c)
 

1. What is the expansion of the universe and how does it occur?

The expansion of the universe refers to the continuous increase in the distance between galaxies and other celestial bodies. This expansion is driven by a force known as dark energy, which is a mysterious force that counteracts the force of gravity and causes the universe to expand at an accelerating rate.

2. What evidence do we have for the expansion of the universe?

One of the main pieces of evidence for the expansion of the universe is the observation of redshift in the light emitted from distant galaxies. This redshift is caused by the stretching of light waves as they travel through an expanding universe. Other evidence includes the cosmic microwave background radiation and the observed distribution of galaxies in the universe.

3. What is the role of dark matter in the expansion of the universe?

Dark matter is believed to play a crucial role in the expansion of the universe. It is thought to make up about 27% of the universe and its gravitational pull helps to slow down the expansion caused by dark energy. Without the presence of dark matter, the expansion of the universe would be much faster.

4. How does the expansion of the universe lead to the convergence of galaxies?

As the universe expands, the distance between galaxies increases. However, gravity still plays a role in attracting galaxies to one another. This results in the convergence of galaxies towards each other, forming clusters and superclusters. This convergence is thought to be the result of the expansion of the universe slowing down due to the effects of dark matter and gravity.

5. How does the study of the expansion and convergence of the universe impact our understanding of the origins of the universe?

Studying the expansion and convergence of the universe provides valuable insights into the origins of the universe. It allows us to better understand the fundamental forces that govern the behavior of the universe, such as dark energy and dark matter. It also helps to support the Big Bang theory and provides evidence for the evolution of the universe over time.

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