So how fast do you think things go?
According to our friend Wikipedia a greyhound can travel upto 74 kilometres per hour (km/h), the Onager or Wild Ass (also my nickname for my sister) can run short sprints at 70 km/h. It is pretty well known that the fastest animal is the Cheetah who can travel at an amazing 120 km/h. The fastest human is currently Usain Bolt ran his World Record 100m sprint at just over 10 metres per second, and according to a recent scientific paper can produce more energy than a bullet as it leaves a gun.
But what is the fastest something can go? We've already talked about infinity which is the largest something can be, so is there an infinite speed? Can somethings in space just go as fast as they like? Well through out history scientists had this battle over and over again, is there a cosmic speed limit?
Well yes, yes there is.
All the stars we see in the sky, the light from them has taken hundreds even millions of years to reach us.
*Credit to Wikipedia for the photo
If you can just make out the little red dot there, that is Proxima Centura, our near star friend. The light from this star takes just over 4 years to reach us (4.367 years to be exact). This is because light has a speed limit, it is the fastest thing in the Universe, light can travel at a maximum speed of
299,792,458 metres per seecond (m/s). Some things happen at this limit which I'll talk about at another post.
Why light travels at this speed is another question, it is a constant number that always appears in the maths. Some scientists have suggested that if light could travel at an infinite speed limit it wouldn't exist at all! (See what I mean about the philosophical?!)
What do you think? How does it make you feel to know that we always see the past of stars?