Looking back 10 billion years

  • Thread starter UncleFungus
  • Start date
  • Tags
    Years
In summary, we continue to observe galaxies born during the early part of the universe's existence, with some being 10 billion light years away. Due to the expansion of the universe, galaxies do not all appear on the same side of the sky and there is no central point in the universe. The universe itself was created and has no edges or center. The commonly used balloon analogy helps to explain this concept.
  • #1
UncleFungus
4
0
We continue reaching further and further back in time by observing galaxies that were born during the early part of the universe's existence. Some of the furthest galaxies we can see are 10 billion light years away, that is, their light has taken that long to reach us.

In light of the Big Bang, if these galaxies are at the edge of the visible universe wouldn't they all appear on the same side of the sky?

That is, the light from galaxies of the same age on the "other" side of the universe has not reached us yet?

Actually, wouldn't all the galaxies at the edge of the universe that we can see all be concentrated in one general area of the sky?
 
Astronomy news on Phys.org
  • #2
UncleFungus said:
We continue reaching further and further back in time by observing galaxies that were born during the early part of the universe's existence. Some of the furthest galaxies we can see are 10 billion light years away, that is, their light has taken that long to reach us.
correct, the earliest are around 300M years after big bang.


In light of the Big Bang, if these galaxies are at the edge of the visible universe wouldn't they all appear on the same side of the sky?
Nope - we live IN the universe remember.
The universe was created at a point, it then spread out into nothingness (not empty space - but really nothingness!)

We aren't at any special central point in the universe, in fact for some slightly difficult to picture reasons there isn't a centre of the universe.
Whichever direction we look we see further back in time, until ultimately at the microwave background we see the energy that filled the universe before any matter was created.
 
  • #3
mgb_phys said:
We aren't at any special central point in the universe, in fact for some slightly difficult to picture reasons there isn't a centre of the universe..

For sure this is what I'm not seeing. I think of the Milkyway as halfway from the peach pit to the skin, give or take a few million light-years. I guess when dealing with such massive distances and space-time fluctuations one needs to abandon geometrical thinking.

Thanks for the reply.
 
  • #4
On the scale of the galaxy stars aren't randomly distributed - they are clumped in the
centre of the galaxy and in a thin disk, that's easy to see (at least with dark skies)

But the milky way is really tiny backyard stuff.
It's only about 100,000lyr across compared to a universe 80Bn lyr in size and is only one of 100Billion galaxies in the universe.
The few galaxies near us are clumped together because they feel each other's gravity - but as you look further out into space the galaxies are randomly spaced.
 
  • #5
UncleFungus said:
For sure this is what I'm not seeing. I think of the Milkyway as halfway from the peach pit to the skin, give or take a few million light-years.
Wait. What?

You think the universe is a sphere like a peach and we are somewhere halfway from the centre?

No. We are at the centre. As is every other point in the universe. Everywhere is the centre.
 
  • #6
Well, no, I don't actually believe there is a peach pit in the "center" of the universe. But it is rather difficult (for me) to really understand the concept of "everywhere is the center". I do understand the notion that everything in the sky is moving away from everything else in the sky, which may or may not lead one to hypothesize everywhere is the center. Of course, if everything is moving away from me then I must be in the center.

I'm sure I'm not visualizing the time-space dialation/expansion correctly, but I assume that the universe was once a singularity, so the big bang began at a point and the universe is expanding from that point in every direction. That assumption, however wrong, leads me to the peach-pit analogy.
 
  • #7
The important (and tricky) bit to 'get' is that the universe wasn't empty space and everything then exploded out of one point at the centre.

It was the universe, ie. empty space and time itself, that was created.
Now the tricky bit - the universe is 4dimensional so in 3d has no edges and no centre.
The normal example is to imagine a 2d world on a balloon - as the balloon inflates every point on it seems to be moving away from any point on the surface - there is no centre point on the surface and no edge.
The universe is like that - except we are a 3d planet on the surface of a 4d balloon!
 
  • #8
Thanks for the thoughtful response. I'll need to chew on that one for a while.
 
  • #9
The often-used analogy is that of the skin of an idealized balloon which is being inflated. Initially, all points on its surface are close together. As the balloon expands, every point on its surface recedes from every other point. There is a centre of expansion - the centre of the balloon - but this centre is not part of the skin. The same holds for our universe: the centre of expansion is something other than a point in space.

The reason the analogy uses a two-dimensional surface is that it can then use the third spatial dimension to represent concepts like the centre and the curvature of the skin. The equivalent for a three- (four-) -dimensional space (-time) is naturally much harder for our three-dimensional spatial imagination to process.

ETA: Double-post...
 

1. How do scientists look back 10 billion years?

Scientists use various techniques such as telescopes, satellites, and computer simulations to study the light and other signals from objects that are 10 billion light years away, allowing them to look back in time.

2. What information can be gathered from looking back 10 billion years?

By looking back 10 billion years, scientists can observe the evolution of the universe, the formation of galaxies and stars, and the expansion of space. They can also gather data on the composition and structure of the early universe.

3. How far can scientists look back in time?

Scientists can look back up to 13.8 billion years, which is the estimated age of the universe. This is possible because light travels at a fixed speed and takes time to reach us, allowing us to see objects as they were in the past.

4. How does looking back 10 billion years help us understand the present?

Studying the early universe can provide insights into the fundamental laws of physics and the origins of the universe. It also allows us to understand the current state of the universe and make predictions about its future.

5. What challenges do scientists face when looking back 10 billion years?

One of the main challenges is the vast distances involved, which means that the signals we receive are very faint and require advanced technology to detect. Another challenge is that the universe was very different 10 billion years ago, so scientists must use complex models to interpret the data accurately.

Similar threads

  • Astronomy and Astrophysics
Replies
12
Views
1K
  • Astronomy and Astrophysics
Replies
3
Views
585
  • Astronomy and Astrophysics
Replies
11
Views
1K
  • Astronomy and Astrophysics
Replies
9
Views
975
  • Astronomy and Astrophysics
Replies
6
Views
2K
  • Astronomy and Astrophysics
Replies
2
Views
1K
Replies
1
Views
1K
  • Astronomy and Astrophysics
Replies
25
Views
2K
  • Astronomy and Astrophysics
Replies
17
Views
2K
  • Astronomy and Astrophysics
Replies
18
Views
3K
Back
Top