YouTube has the video How to travel faster than light.
Traveling faster than light is one of humanity’s dreams. Sadly, modern physics doesn’t cooperate. However there are examples where it really is possible to travel faster than light. In this video, Fermilab’s Dr. Don Lincoln tells us of these ways in which the universe breaks the ultimate speed limit.
When I start to think about astrophysical measurements, I come up with some questions that just do not make any sense. Thinking about the lessons, particularly at the end of this video, it helps me put those questions into some perspective better than my intutions give me.
I’ll leave some hint of the conundrum here in case I ever forget what the question was.
When you are talking about the farthest away object that we can see, it is about 13 billion light years away. That supposedly means that the light beam we see on our telescopes started to travel toward our telescope 13 billion years ago. So where is the object now, that was where we see it 13 billion years ago? 13 billion years ago was about the time of the big-bank that started our universe. At that time everything was contained in a little dot of space. So the object couldn’t have been 13 billion light years away from us. So how did the light leave this object that was right next to us, but taken 13 billion years to arrive here? The video above gives some hints as to what is going on.
The hint from the video is to imagine that far away object being on the skin of an inflating balloon centered around us. If the balloon is inflating so that the skin of the balloon is moving away from us faster than the speed of light at first, then the light beam from the object won’t be able to reach us until the inflation slows down.