The Theory of Relativity

Ugh, Einstein and his theories.

Albert Einstein, the worlds most renowned physicist was well, really smart. Some enthusiasts come close to worshipping him for his intellect and ingenuity.

His theory stated that the speed of light was constant, meaning that everywhere in space light travelled at the same speed (and yes light does have a speed). This was a huge for astrophysicists because they now had a universal constant(something that doesn’t change) to measure speed. Before his theory was proved, we couldn’t even calculate the speed of earth in orbit because it had to be relative to something.

To explain this, imagine two cars driving at the same speed on a road. If they drivers look at each other they look as if they are still but, if someone is standing on the side of the road they see them moving pretty fast. On the other hand, someone who is running will see the cars moving slower than the person standing on the side of the road. Einstein stated this and said that the speed of an object is relative to the observer.

So, if we say that the sun is still relative to us it might actually be moving extremely fast throughout space with us in its orbit and we wouldn’t even notice. I hope now you understand why this discovery was huge for scientists studying space. This was called the special theory of relativity.

The curvature of spacetime that I talked about in the previous blog was also discovered by Einstein, in his general theory of relativity. This theory stated that massive objects cause a distortion in spacetime which we know as gravity.

The evidence for this comes with an effect called gravitational lensing.

The image shows us what looks like a circular galaxy but, it not really circular. The bright object in the middle is so massive that it bends light around it making the galaxy appear as if it is round.

The image above is a perfect explanation for this effect. It shows us that this massive object is bending light around it and indirectly causing distortion in spacetime.

Einsteins theory also stated that time does not pass at the same rate for everyone. His theory stated that the faster you move through space, the slower time passes for you. He explained it with the following example:

Imagine there is a clock on a wall and it reads 1:00pm a person is standing watching the clock and you start travelling at the speed of light away from the clock this means that you are travelling as fast as the light that caused you to see the time. This will result in you seeing 1:00pm but for the person standing next to the clock time will pass normally, therefore timepasses slower for you than the person watching the clock.

Einstein’s famous equation ‘E=mc^2’ where ‘E’ is energy, ‘m’ is mass and ‘c’ is the speed of light, means that mass and energy are manifestations of the same thing which also means that the faster you travel the more mass you appear to have which is why Einstein also said that matter cannot travel faster than light, effectively making the speed of light a ‘universal speed limit’. And because at the speed of light mass would become infinite it would require an infinite amount of energy to move which is impossible.

image credits for gravitational lensing: http://www.ita.uni-heidelberg.de/research/bartelmann/images/curvature.jpg