How is it that we see farther out in space (farther back in time) than in the past?
Many a times we read about how telescopes and probes look back in time. We seem to be able to look back further as we move farther from the earth. For example the recent "probe" which took a "picture" of the universe at age 380,000 years after the big bang.
Now I understand that the light or radiation that we observe started out light years before we observed it and therefore we are acutally seeing back in time when we observe this. But how do these observations go further back in time as we move away from the earth ? This could only be possible if were travelling at faster than light speed and therefore have the ability to move a few light years back from the earth and look at light which left its origin even earlier.
It's not the case that space-based telescopes can see farther away (farther back in time) because they're far away from the Earth. At least, that's not the direct reason.
The reason why we can get impressive pictures of the very distant universe now that we couldn't get 20 years ago is because the technology is better. So we can build better telescopes that are more sensitive. The proximity of a space-based telescope to the Earth is only an issue in the sense that the Earth is a big source of light pollution across a broad region of the spectrum. So a telescope that's far away from the Earth doesn't have to worry about interference from the Earth.
For example, Spitzer (formerly the Space Infrared Telescope Facility (SIRTF)), an infrared telescope that was launched in August 2003, is in an orbit that puts it 15 million kilometers away from the Earth. The idea is to keep it away from the visible and infrared light of the Earth. If it was closer to the Earth, then it wouldn't be as sensitive. So in that sense, you're right that there's a link between how far you are from the Earth and how far away you can see, but it's not quite the kind of link that you describe.
Get More 'Curious?' with Our New PODCAST:
- Podcast? Subscribe? Tell me about the Ask an Astronomer Podcast
- Subscribe to our Podcast | Listen to our current Episode
- Cool! But I can't now. Send me a quick reminder now for later.
- Why is looking out into space the same as looking back in time?
- Can we look back far enough in time to see the Big Bang?
- Why is the Hubble Space Telescope in space?
- What are the advantages and disadvantages of using a telescope in space?
- Where is the Spitzer Space Telescope?
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 33923 times since March 9, 2003.
Last modified: October 18, 2005 6:44:39 PM
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)