Is the Hubble Deep Field evidence for inflation in the early universe?

In summary, the Hubble Deep Field shows galaxies as distant as 13 billion light years away, which is close to the estimated age of the universe. The question is whether these galaxies should appear closer together due to the universe expanding less at that time. However, it is difficult to accurately measure the separations between these galaxies because we are mostly seeing the brightest ones. Tests of separations between galaxies and the cosmic microwave background indicate that the universe has a positive spatial curvature. This raises questions about the expansion and inflation of the universe.
  • #1
joeydendron
3
0
Apologies in advance if this is a stupid question.

I'm told the Hubble Deep Field shows galaxies as distant as 13 billion light years away.

13 billion years isn't far off the apparent age of the universe - 13.75 billion years, says Wikipedia, from estimates based on the Hubble constant.

I'm wondering (and here's the intellectual nose-dive) whether that's long enough ago that those old galaxies should appear "bunched up" - visually closer to each other because we're seeing them at a point in history when the universe had expanded significantly less than it has by now? Or... was most of the expansion in the first billion years (in which case I'll stagger around for a couple of weeks worrying about how it managed to expand at 13 times the speed of light).

If anyone can shed any light on my confusion, I'd be really grateful.

Thanks in advance!
 
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  • #2
The redshift of objects in the HUDF (Hubble Ultra Deep Field) are approximately ten at the greatest. This means that when the light from these objects was emitted, the universe was ~10 times smaller (11 to be precise...).

Inflation ocurred when the universe was very very young, ~ 10^-30 seconds after the big bang or something like that. Way earlier than any structure in the universe had formed, and way earlier than we can hope to (ever) observe directly.
 
  • #3
The high redshift deep field galaxies existed in a smaller spacetime region, but, few had yet formed.
 
  • #4
joeydendron said:
Apologies in advance if this is a stupid question.

I'm told the Hubble Deep Field shows galaxies as distant as 13 billion light years away.

13 billion years isn't far off the apparent age of the universe - 13.75 billion years, says Wikipedia, from estimates based on the Hubble constant.

I'm wondering (and here's the intellectual nose-dive) whether that's long enough ago that those old galaxies should appear "bunched up" - visually closer to each other because we're seeing them at a point in history when the universe had expanded significantly less than it has by now? Or... was most of the expansion in the first billion years (in which case I'll stagger around for a couple of weeks worrying about how it managed to expand at 13 times the speed of light).

If anyone can shed any light on my confusion, I'd be really grateful.

Thanks in advance!
Yes, absolutely. And they do! These sorts of tests, looking at the typical separations between galaxies, are our most sensitive tests of the overall spatial curvature of our universe. But you have to realize that to do this test accurately, one of the main things you have to take into account is the fact that when we look really far away, often times we're only seeing the absolute brightest galaxies that far back. So it often turns out not to be feasible to test separations between galaxies as far back as the furthest galaxies we can possibly see (because we're only seeing a small fraction of the galaxies).

So, for the most part, we look at galaxies that are much closer (though still pretty far away, say a few billion light years), and add in the cosmic microwave background (at a redshift of z=1089, when the universe was over a thousand times smaller) for really far-away data.
 
  • #5
These are suitably thought-provoking answers - thanks for taking time to post! I'll do some searching for reading about expansion vs. inflation now.

Have a good week everyone

Dave
 

1. What is the Hubble Ultra Deep Field (UDF)?

The Hubble Ultra Deep Field is an image captured by the Hubble Space Telescope in 2003 that shows a small section of the sky with an incredibly high level of detail. The image is made up of hundreds of individual images taken over the course of 400 orbits around Earth, and it has allowed scientists to study some of the oldest and most distant galaxies in the universe.

2. How does the UDF relate to inflation in the early universe?

The UDF is important in the study of inflation because it provides a glimpse into the early universe, only about 400 million years after the Big Bang. By studying the properties and distribution of galaxies in the UDF, scientists can gain insight into the conditions and processes that led to the rapid expansion of the universe during the inflationary period.

3. What have scientists learned from studying the UDF?

Scientists have learned a great deal about the early universe from studying the UDF. They have been able to observe and measure the properties of galaxies from a time when the universe was much younger and smaller than it is today. This has allowed them to test theories about the formation and evolution of galaxies, as well as the overall structure and expansion of the universe.

4. How has the UDF impacted our understanding of the universe?

The UDF has greatly expanded our understanding of the universe and its history. By studying the distant galaxies in the UDF, scientists have been able to confirm the validity of the Big Bang theory and the concept of inflation. They have also been able to gather data on the early stages of galaxy formation and the distribution of matter in the universe.

5. What are some potential future uses for the UDF?

The UDF will continue to be a valuable tool for scientists in the future. As technology and techniques improve, the data from the UDF can be re-analyzed and used to answer new questions about the early universe. Additionally, the UDF can serve as a reference point for future observations and studies of distant galaxies and the expansion of the universe.

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