Light barrier
In my previous blogs, we have seen the evidence that light moves only at one speed and its consequences for our understanding of time itself. But why is it that nothing can move faster than with the vacuum speed of light?
Indeed, if you put more energy into a car, the car will go faster. If we keep burning more and more rocket fuel, can we not surpass any speed given to us, at least in principle?
barriers
The answer is: no!
We are very much used to barrier-free velocities: we could cycle with 10 mph or 20 mph. And yet, the vacuum speed of light is a hard limit: no object can travel speedier, and not even information can spread faster. The universe is like a bubble, and we are like fish in the sea that cannot break through the ocean's surface.
Sir Issac Newton (1643-1727)
Newton is the founder of Classical Mechanics, which excellently describes all our physics affairs in everyday life. There is, of course, a connection between (kinetic) energy and the speed of a car, and true: the higher the energy of the vehicle, the higher its speed. In fact, according to Newtonian mechanics, if we quadruple the (kinetic) energy of a car, we double its speed.
Assume a space rocket flies through space with 1% of the speed of light, that is with 3,000 km per second. If we quadruple its energy seven times, we will travel faster than the speed of light according to Newton - in fact, the rocket's speed would be 1.28 times that of light.
If you have followed my previous blogs, you might suspect that this is not what happens - the flow of time changes, and the story is different from what we are used to in everyday life.
There is a bit of mathematics involved, which I am not going to discuss or derive here. Let's first check why we think that Newtonian physics is excellently describing our daily routines. Assume a car is driving at 70 mph, and we quadruple its (kinetic) energy. Newton says that the vehicle then travels at 140 mph. If you do the maths, the car is, in fact, short of 140 mph by 0.000,000,000,000,000,004 mph. For every practical purpose in everyday life, the flow of time is universal, and Newton's predictions are coming true to a staggering precision.
Approaching the barrier of light
Things pan out differently when we move with a speed comparable to the speed of light. We keep quadrupling the spacecraft's energy; the speed increases, but with smaller and smaller amounts. We would need an infinite amount of energy to approach the light barrier, let alone surpass it.