Space NEWS #9 (Gravitational waves detected!)

those news are extremely important for modern science, lets just see what is it about.

So today, 11.2.2016 gravitational waves were for the first time detected directly. I already wrote post about gravitational waves here, but anyway in short those are the ripples in space-time made by object accelerating through space-time. Such gravitational waves were predicted by Einstein in his theory of relativity but it took a long time to detect them.

Why? Well gravity is very weak force compared to other fundamental forces so there must be a great of source of so we are able to detect those waves.

This time the source here were two merging black holes. All this information is important since they are black holes which means that they are heavy (36 and 29 solar masses) and also they are merging which means that this acceleration is pretty huge when they rotate towards each other. They merged a black hole of 62 solar masses, the missing mass was converted to gravitational waves, not kidding.

As Phil Plait writes:

And the amount of energy is staggering: This single event released as much energy as the Sun does in 15 trillion years.

How did scientists find this out?

On this video you can watch how it works, anyway here you go if you do not like links:

There is a laser in closed tube. This laser fires hitting glass which splits it on two parts with one beam going in the right angle to the other. Both hit mirrors which are hundreds of meters away. The beams bounce back hitting the mirror which means that they come together. Normally their wavelength will cancel out:

Above the red line is the wave that when everything is normal is canceled out (it is straight line) but when gravitational wave passes one mirror will move a little bit so the light will not cancel but rather go through, towards detector. Here you go, you have just found a gravitational wave!


Gif from here.


Gravitational waves

before I start to write about gravitational waves, let me explain how electromagnetic waves work.

Electromagnetic waves are just light which we see from candle for example. The thing is that in such a candle atoms oscillate and in the process of burning electrons are jumping on more energetic levels, orbitals. When this happens they want to go back right away, so they emit photon and fall back on the lower orbital. Such a photon then travels towards you and you can sense it with your eye.

But all of those atoms oscillate because there is huge temperature in the candle (800°C). They move back and forth creating waves of photons because some photons are closer together as the atom moves to the maximum of oscillation. As it goes back the photons are more stretched apart creating the gap in the wave. This is called electromagnetic wave.

If you had really good eye and somebody would walk away from you with candle, the light would not stop but you would observe the light come towards you in wave, in quantum. The frequency would get smaller and smaller but it would never disappear and would always appear with the same luminosity.

Now when you have gravity this can happen too in what is called gravitational wave. Such a wave is a result of shaking with something that interacts with gravity. The problem here is that gravity is such a weak force that you just can not observe it on candle and you need some kind of star.

Here comes two neutron stars which were found to be rotating rapidly around each other. As they rotate they create the ripples in space time, gravitational waves. In 1993 the Nobel prize was awarded to two guys who were able to indirectly observe how this system of two neutron stars was losing energy emitting those waves, they were observed to be slowly getting closer and closer to each other.

Physicists are trying to observe gravitational waves directly with tremendously precise methods using lasers but it was not yet achieved.


Picture is from here.