How can the Universe expand faster than the speed of light during inflation?
Some sources indicate that the big bang caused an expansion which traveled faster than the speed of light. How can this be?
You ask a good question, one whose answer lies in the subtle difference between expansion that is faster than the speed of light and the propagation of information that is faster than the speed of light. The latter is forbidden by fundamental physical laws, but the former is allowed; that is, as long as you are not transmitting any information (like a light pulse), you can make something happen at a speed that is faster than that of light. The expansion of the Universe is a "growth" of the spacetime itself; this spacetime may move faster than the speed of light relative to some other location, as long as the two locations can't communicate with each other (or, in terms of light rays, these two parts of the Universe can't see each other). According to the theory of inflation, the Universe grew by a factor of 10 to the sixtieth power in less than 10 to the negative thirty seconds, so the "edges" of the Universe were expanding away from each other faster than the speed of light; however, as long as those edges can't see each other (which is what we always assume), there is no physical law that forbids it.
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.
- Could the Universe have expanded faster than the speed of light at the Big Bang?
- If the universe is 15 billion years old, how can it be larger than 15 billion light years across?
- How fast is the Universe expanding?
- What happens to a substance if its speed is more than the speed of light?
- How do scientists slow light down?
- Is the universe expanding faster than the speed of light?
- Can I communicate faster than light?
- Wait, I'm still confused why information can't travel faster than the speed of light.
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 72319 times since November 9, 2002.
Last modified: April 25, 2005 10:13:11 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)