Is the universe expanding faster than the speed of light? | Alex Filippenko and Lex Fridman

TL;DR

The radius of the observable universe is larger than its age due to the expansion of space itself.

Transcript

this might be a fun question to ask to kind of explore the idea of the expanding universe yeah so the the radius of the observable universe is 45.7 billion light years yeah and the age of the universe is 13.7 yeah billion years that's less right than the radius of the universe yeah how's that possible so that's a great question so that and i meant ... Read More

Key Insights

• 🤕 The observable universe is larger than its age due to the expansion of space between galaxies.
• 🙂 Light doesn't exceed the speed of light locally, but the expansion of space causes the estimated distance traveled to be greater.
• 🙂 In an accelerating universe, objects can move apart faster than the speed of light due to the expansion of space.
• 🙂 Space itself can expand faster than the speed of light, according to the principles of relativity.

Questions & Answers

Q: How is the radius of the observable universe larger than its age?

The expansion of space between galaxies causes light to traverse additional distance while it is traveling towards us, leading to a larger observable universe radius.

Q: Does the light traveling through expanding space exceed the speed of light?

Locally, the light does not exceed the speed of light. The expansion of space causes the distance that the light has already traveled to expand, giving the illusion of faster travel.

Q: Can objects in an accelerating universe move apart from each other faster than the speed of light?

Yes, in an accelerating universe, objects can move apart from each other faster than the speed of light, as the expansion of space itself can exceed the speed of light.

Q: Is there any limitation in relativity that prevents space from expanding faster than the speed of light?

No, there is nothing in special or general relativity that prevents space itself from expanding faster than the speed of light. This is observed by cosmologists and is not contrary to Einstein's theories.

Summary & Key Takeaways

• The observable universe has a radius of 45.7 billion light years, which is greater than its age of 13.7 billion years.

• The expansion of space between galaxies causes light to traverse a greater distance, leading to the apparent discrepancy.

• Locally, light does not surpass the speed of light, but the expanding space gives the illusion of faster travel.