When we look back to the Big Bang, why don't we see the universe as a tiny speck of matter? (Intermediate)

When we look at the furthest object we can see through the Hubble Telescope, it is said we are looking at the edge of the Universe. If we are looking at light that is coming into the telescope from billions of years in the past, it looks to me like we are seeing a very contracted Universe and not the Universe as it would actually appear in real time. It follows that if we could see objects whose light was sent 15 billion light years ago, all we would see would be a small speck of matter surrounded by empty space. I know this is not the case, but I do not know why. Could you explain this to an amateur?

We do see the universe as it was when it was much smaller, but that doesn't mean it will look like a small speck. The reason is that we are inside the part of the universe we can see. In any direction we choose to look, we can see light which was emitted in the last 13 billion years or so from that direction, from any object that was close enough to us then such that as the universe expanded, it is still close enough for its light to reach us now. Therefore, we can see objects all around us. (For an example of what we do see when we look back as far as we can - not with the Hubble Telescope, by the way - have a look at this picture or see the related questions below.)

Or another way to look at it: if we did see a small speck, where in the sky would you expect it to be located? There is nothing special about any particular direction that would cause us to see the "universe" there and not somewhere else. In effect, what we see is a small speck, only it is spread out across the entire sky, and we are inside it!

This page was last updated June 27, 2015.

About the Author

Dave Rothstein

Dave is a former graduate student and postdoctoral researcher at Cornell who used infrared and X-ray observations and theoretical computer models to study accreting black holes in our Galaxy. He also did most of the development for the former version of the site.

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