The Nobel Prize in Physics 2017: Popular Information

INTRODUCTION

In the last blog, I'm going to talk about popular information about physics in 2017, in this blog, I'm going to write about popular information about physics in 2017. This is the link to what I want to write https://www.nobelprize.org/uploads/2018/06/popular-physicsprize2017.pdf

The topic of the Nobel Prize in Physics in 2017 is about detecting gravitational waves that contract spacetime when objects having mass accelerate. RAINER WEISS and KIP S. THORNE, together with BARRY C. BARISH, the scientist, and leader who brought the project to completion, have ensured that more than four decades of effort led to gravitational waves finally being observed in LIGO (the Laser Interferometer Gravitational-Wave Observatory) which located in the steppes of the northwest USA, outside Hanford and in Livingston in the southern swampland of Louisiana. The distance between the two observatories is just over 3,000 km away (Look at the figure on page 5).

WHAT ARE GRAVITATIONAL WAVES?

I talked about Einstein's equation in the article 'The Nobel Prize in Physics 2020: Popular Information', and when we impose some conditions to this equation not the same as black holes' conditions, we can lead to the solution that represents waves that travel contracting spacetime and speed of the waves is the same speed as the speed of light. To detect electromagnetic waves are easy for us, but to detect gravitational waves are very very hard for us. For example, in this case, even when two black holes which one mass is 36 times larger than the sun's one and the other mass is 29 times larger than the sun's one collide with each other, the accuracy of measurement of the contraction of the spacetime is equivalent to measuring the distance of 10 light-years with an error of a strand of hair. The total cost of LIGO until first detecting gravitation waves is about six hundred twenty million dollars. Gravitational waves can be used to measure black holes that can't detect by using electromagnetic waves.

HOW TO DETECT GRAVITATIONAL WAVES?

Look at the figure on page 4. This figure represents the structure of the gravitation waves detector. I talked that gravitational waves propagate while contracting spacetime so it seems impossible to detect gravitational waves but one of the properties of electromagnetic waves such as light, laser beams, and so on is that their speed is no affection the coordinate system whether an inertial or a non-inertial system, so we can detect gravitational waves to use the difference in the distance between two laser beams.

Frist, Shine the laser beam towards the reflector. Next, in the reflector, the laser beams split two laser beams, and reflect in the mirror which locates four kilometers away. Finally, the two laser beams return to the starting point. If there are no gravitational waves (strictly, the condition of occurring gravitational waves is that objects have mass accelerate but gravitational waves from objects around us are too small to detect, so we can neglect small gravitational waves), there is no contracting spacetime, so the two beams strengthen each other. but If there are gravitational waves, there is contracting spacetime, so the two beams weaken each other. 

l said above, The distance of contracting spacetime is several thousand times smaller than nucleus out of four kilometers, so we have to consider the influences of quantum mechanics, thermal vibrations, and so on. To detect gravitational waves, a lot of technologies have been developed.