Exploring the Expanding Universe - Nova Documentary

In summary: Based on the shows I've seen, they suggest the universe is expanding. Further objects are observed as moving away faster than closer objects. But the farther objects are also older, so according to age, wouldn't that mean that the universe is slowing down? They also suggest that all objects are at a similar distance moving away at a similar speed. So, although the universe may be expanding, it appears that it's slowing down over time.
  • #1
meatym
5
0
i've seen many documentaries. most recently nova had one on the expanding universe which prompted me to send them (nova@wgbh.org) the following:

based on the nova shows I've seen, they suggest the universe is expanding.
farther objects are observed as moving away faster than closer objects.
but the farther objects are also older, so according to age, wouldn't that mean that the universe is slowing down?
also, are all objects at a similar distance moving away at a similar speed?
===
they sent a response that said they forwarded to their producers, but in the meanwhile, i thought i'd look elsewhere...

thanks in advance for any responses.
 
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  • #2
Farther objects are older to US because we can only observe them as they were in the past depending on how long light from that object took to get to us. But if you take a constant slice of time at any instant and analyze the observable universe (this is all mathematically) all objects, and I mean at the large where isotropy and homogeneity are preserved, are of course the same distance in time from t = 0. The rate at which objects recede from whatever you pick to be the origin (since you do have that freedom) is directly proportional to the distance between the object and your chosen origin. Objects all at the same distance from "the origin" will recede at the same rate.
 
  • #3
The answer to your last question is yes. The Hubble constant which is used to measure the expansion of the universe is based on an expansion speed per distance from us.

So, picture the universe expanding uniformly in all directions. So, the further away a particular object (e.g., galaxy) is, the more expanding space there is between you and it. So it appears to be moving away faster than something which is closer.

And due to the finite speed of light, the older it appears to us (not actually older...it's just that we're seeing it's past because light from its present state has not reached us yet).

So, the ancient galaxies we're seeing at great distances are not causing the universe to slow down. But since the universe expansion is actually accelerating, I suppose we're seeing those ancient galaxies from a time when the universe was expanding at a slower rate.

Clear as mud?
 
  • #4
Phobos said:
But since the universe expansion is actually accelerating, I suppose we're seeing those ancient galaxies from a time when the universe was expanding at a slower rate.
Clear as mud?

but since we are seeing the galaxies as they were a long time ago - the further away, the further back into the past - and the older the image, the faster it is moving...
that would imply to me that the galaxy's age is inversely proportionate to it's speed.
the newer the image, the slower it is moving. wouldn't that mean that things are slowing down as time goes on?
 
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  • #5
thanks for answering the other quetion, btw
 

1. What is the Expanding Universe?

The Expanding Universe is a scientific theory that states the universe is constantly growing and moving apart from itself. This theory is supported by observations of galaxies moving away from each other and the redshift of light from distant objects.

2. How was the Expanding Universe discovered?

The Expanding Universe was first discovered by astronomer Edwin Hubble in the 1920s. He observed that galaxies were moving away from each other and that the farther away a galaxy was, the faster it was moving. This led to the theory of the Expanding Universe.

3. What evidence supports the Expanding Universe theory?

Aside from the observations of galaxies moving away from each other and the redshift of light, other evidence for the Expanding Universe includes the cosmic microwave background radiation, the abundance of light elements, and the large-scale structure of the universe.

4. How does the Expanding Universe affect our understanding of the universe?

The Expanding Universe has greatly impacted our understanding of the universe. It has led to the discovery of the Big Bang theory, which explains the origin of the universe. It has also helped scientists understand the age and size of the universe, and how it has evolved over time.

5. What is the significance of the Nova Documentary on Exploring the Expanding Universe?

The Nova Documentary on Exploring the Expanding Universe provides a comprehensive and visually stunning exploration of the history and current state of the Expanding Universe theory. It also highlights the groundbreaking research and discoveries made in this field, and how they have shaped our understanding of the universe. The documentary serves as an educational and informative resource for anyone interested in learning more about the Expanding Universe and its impact on our understanding of the cosmos.

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