Speed of Light and Size of the universe

In summary, the age of the universe is approximately 13.73 billion years old and its diameter is 93 billion light years. The universe's expansion does not violate the speed of light, as it is the space between points that is expanding. Tachyons, which are hypothetical particles, may be able to travel faster than light but would also travel backward in time. However, there is no evidence to support their existence.
  • #1
Praelly
2
0
Hello, I am quite new to this forum, but have been lurking around reading your posts for some time now.

I have one question that has bothered me for some time. Scientists have been observing the universe with advanced technology, and seem quite certain that their observations indicate the age of the universe is approximately 13.73 billion years old, and that the "diameter" of the observable universe is 93 billion light years. My question is how is this possible if supposedly nothing can move faster than the speed of light? I've read somewhere that the universe itself expands with a speed greater than c, and I've also stumbled upon tachyons. Which also supposedly moves faster than light. I was wondering which "things" are limited to the speed c, and why is it this way?

This does not make any sense to me. I've watched numerous documentaries where physicists say that nothing can move faster than light. Have they not studied the universe's expansion, or is this just a matter of course?

I hope some of you can shed some light on this topic for me, I haven't found any good explanation to this yet..
 
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  • #2
Hi,

This is quite a common question. My suggestion is to read this article: http://www.astro.princeton.edu/~aes/AST105/Readings/misconceptionsBigBang.pdf [Broken]
and come back with any further questions you may have.
 
Last edited by a moderator:
  • #3
I'll give you a nutshell answer:

Nothing can travel locally faster than the speed of light, but there is no such constraint on points billions of light years apart. It is not the points that are moving faster than c, it is the space between them that is expanding. Locally, those points are relatively stationary.
 
  • #4
Thanks! That article was very helpful.

But I'm still wondering about the tachyons, if they even exist why can they travel faster than c without receding speed
 
  • #5
Praelly said:
Thanks! That article was very helpful.

But I'm still wondering about the tachyons, if they even exist why can they travel faster than c without receding speed
Tachyons are hypothetical particles; there is no reason to believe they exist. The point is that relativity does not forbid particles traveling faster than c, but it does forbid them slowing down to c. Also, they would travel backward in time.
 

1. What is the speed of light?

The speed of light is approximately 299,792,458 meters per second in a vacuum. This is the maximum speed at which all matter and information in the universe can travel.

2. How was the speed of light determined?

The speed of light was first accurately measured by Danish astronomer Ole Rømer in the 17th century using observations of the moons of Jupiter. Since then, it has been repeatedly measured and refined using different methods such as the Fizeau experiment and the Michelson-Morley experiment.

3. Can the speed of light be exceeded?

According to Einstein's theory of relativity, the speed of light is the absolute limit for the speed of any object in the universe. It is not possible for anything to travel faster than the speed of light.

4. How does the speed of light relate to the size of the universe?

The speed of light plays a crucial role in determining the observable size of the universe. Since the universe is approximately 13.8 billion years old and the speed of light is finite, we can only see objects that are within a certain distance from us. This is known as the observable universe, which has a radius of about 46.5 billion light-years.

5. How do scientists use the speed of light to study the universe?

Scientists use the speed of light to measure distances in the universe and calculate the age of objects. They also use it to study the effects of relativity and understand the behavior of matter and energy in extreme environments, such as black holes. Additionally, the speed of light is an important factor in modern technologies such as GPS and telecommunications.

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