What is Gravity? Why are gravitational waves important?


What is Gravity?

Astronomers observe the universe across the electromagnetic spectrum, using optical and radio frequencies. Since the emissions of each of these frequency ranges provide different information, we observe the celestial object of interest from a different angle.

Gravitational waves are different from anything else on the electromagnetic spectrum. In 1915, Albert Einstein, with his general theory of relativity, paved the way for a completely different view of gravity.

Rather than treating gravity as a force pushing or pulling objects with mass in different directions, he described it as a twist in space-time. In other words, gravity means that space (and time) around an object with mass is bent, and this bending determines how objects passing through space will move.

Although Einstein’s theory seems counterintuitive at first, we can observe the effects predicted by this theory right now.

Gravitational waves create a whole new way of observing the universe

For example, this theory says that time moves slower on Earth than on orbiting GPS satellites. This slowdown, however small, makes a difference. This is called ” time dilation ” as a result of the warping of space-time. If we do not make small-time adjustments in satellite communication, we cannot go where we want to go.

Another consequence of the general theory of relativity is this: As objects travel through curved spacetime, they cause ripples called gravitational waves. These waves propagate through space.

As we can hear gravitational waves. No further work is underway to understand what these waves are saying.

Why did we have to wait 100 years before we could hear the sound of gravitational waves?

First of all, these waves are very, very small, about one-thousandth of the diameter of the proton nucleus – so for them to occur on scales that we can detect, very violent events must occur.

In this process, it compresses space in one direction and stretches it in the other direction. The predicted frequencies of these fluctuations are within the human audible range.

In addition, they cannot be detected without very sensitive detectors.

The technology to capture gravitational waves is the most sensitive measurement system ever designed

Physicists use a technique called laser interferometry to detect even the slightest deviation in space-time. In this technique, a concentrated beam of light is sent in different directions, going back and forth between two mirrors before being sent to a detector. If a gravitational wave passes during all these travels, the distance between the mirrors changes by very small amounts, and this change is considered as the difference in the two signals.

In addition to the extremely weak signals from gravitational waves, the presence of a large amount of ambient noise to suffocate these signals makes it even more difficult to capture signals.

Above all, the path of the laser must be quite long. The Laser Interferometer Gravitational-Wave Observatory (LIGO) is therefore designed to be 4 kilometers long in both directions.

Also, the detectors must be suspended in the air in order not to be affected by the vibrations on the ground. What’s more, LIGO has two separate detectors to avoid being fooled by misleading signals; one is in Hanford, Washington State, and the second is in Livingstone, Louisiana. Thus, it is guaranteed that the signal does not originate from a local source.

The gravitational waves observed with millisecond intervals from two detectors on September 14, 2015, were thus cleared of any possibility of error.

1.3 billion years ago, when multicellular life was about to emerge on Earth, two black holes orbiting each other were getting closer and closer. As these two dense objects got closer, they accelerated at close to half the speed of light under the influence of their common gravitational field. Thus, they created the perfect environment for the formation of gravitational waves.


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