Rotating Question Curious About Astronomy? Ask an Astronomer

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

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!

December 2002, Dave Rothstein (more by Dave Rothstein) (Like this Answer)

Still Curious?

Get More 'Curious?' with Our New PODCAST:

Related questions:

More questions about Cosmology and the Big Bang: Previous | Next

How to ask a question:

If you have a follow-up question concerning the above subject, submit it here. If you have a question about another area of astronomy, find the topic you're interested in from the archive on our site menu, or go here for help.

Table 'curious.Referrers' doesn't existTable 'curious.Referrers' doesn't exist

This page has been accessed 34763 times since December 21, 2002.
Last modified: October 18, 2005 6:53:05 PM

Legal questions? See our copyright, disclaimer and privacy policy.
Ask an Astronomer is hosted by the Astronomy Department at Cornell University and is produced with PHP and MySQL.

Warning: Your browser is misbehaving! This page might look ugly. (Details)