Of great fascination to me is speed – a simple but often overlooked little quality representing the rate of change of position over time. One of the really exciting things about speed is that you would assume it is infinitely large; one can quite easily construct an argument for numbers being infinitely large (take the largest number in the universe, add one and you have a larger number therefore there cannot be a largest) – so would this not work for speed? If I am travelling at say 1,000,000 m/s I can add 1, so now I am going faster and so on and so on. Well the logic breaks thanks to light and Einstein.
In short, when you travel fast time travels slow. This is called time dilation – it really exists and we will prove it in a future post. However for the purpose of today; know that it is a fact. But what is oh so exciting about this is that not only does time slow down, there is no asymptotic property; it just reaches a stopping point (brain: pop). What is the stopping point? Well naturally the speed of light, c. My favorite representation of this is:
Q: You are travelling at the speed of light and fire a gun off in front of you. Is the bullet moving faster than you?
A: You didn’t even fire the gun, because time has stopped.
This gives the curious yet exciting fact that light never ages. The light created by the big bang has not aged a second. Lucky light… kind of… although the light, bless it can’t really do anything at all because time isn’t running for it. It is trapped. Actually sounding a lot less fun.
A human being cannot reach the speed of light because as we speed up our mass increases compared with the mass at rest which is found by taking the product of the rest mass and the Lorentz factor. So what this basically means is if you put discrete packets of energy into speeding something up the returns would diminish. As you start to creep to even a small(ish) fraction of c the energy going into making the object more and more massive increases a huge amount. Remember the most famous of all the equations relating energy to mass – energy is proportional to mass at a constant of c squared; or 9.00 x 10^16 (m/s)^s. Now that is a huge constant.
Currently the fastest speed ever reached with a human inside comes from Lunar 10 with a speed of 24,791 mph. As impressive as this is, expressed in mph the speed of light is 671,000,000 mph – so we have achieved 0.004%. The limits of human speed are currently well beyond even comprehending the effects of time dilation seriously – there is a long way to go but that isn’t to say we are not trying. It is a brave and interesting pursuit – and one very much worth keeping an eye on.