Gravity… when we think about it we would remember the famous Newton’s law of gravity -every particle in the universe is attracted to every other particle in the universe based upon their masses. And he concluded gravity is a pull.
Now after 200 years of Newton’s theory. Einstein, one of the greatest minds on the planet came up with the fascinated concept called the “Theory of Relativity” and changes the way we look at the most basic things of the universe like space and time. He explained gravity is a curvature in the 4-dimensional space-time proportional to the object masses. With this, he also explained a much more interesting concept called gravitational waves, which has revolutionized the way we study the Universe.
But what are these gravitational waves? What makes them so special. Let’s find the answer to these questions.
In simple words,
Gravitational waves are ripples in the curvature of space-time, caused by accelerated masses, that propagate as waves outward from their origin at the speed of light.
Baffled? Let me explain this…
In-order to understand gravitational waves, and why they are so important – you need to have a clear idea of gravity and a little knowledge about Einstein’s General Theory of Relativity.
Albert Einstein published his theory of general relativity in 1916, and in it, he explained that time and space are inseparably linked with each other. Together they form the fabric of space on which the whole Universe is built on called space-time.
According to Einstein – Gravity is a curve in the surface caused by the warping of space-time. Any object with mass creates a depression in the space-time into which objects with less mass will fall into the curve and start rolling across the depression-like it’s being attracted to the other mass (this is considered as object’s gravitational field).
For Example: Imagine a big rubber sheet that stretched nice and flat, and take a bowling ball put right in the middle of the rubber sheet, now the rubber sheet will be curved, then roll a marble close to the bowling ball, it will fall toward it and start rolling in the curved trajectory. It seems like the marble is attracted to the bowling ball, but it is just following the path or curvature created in the rubber sheet. This is the model of how gravity works.
Now, let’s look into,
What are gravitational waves?
If mass distorts space-time, then mass under acceleration must create ripples in the space-time. As if you toss a stone in a pond it will create waves that ripple out across the water’s surface. Similarly, massive objects accelerating in space-time will create waves that ripple out across the universe at the speed of light these are called gravitational waves.
What causes Gravitational Waves?
Any object with mass under acceleration will produce gravitational waves. That includes humans, cars, planets, etc., Earth does create these waves as it is accelerated by the sun’s gravity.
But the masses and accelerations of these objects are far too small to make gravitational waves big enough to detect. Among the four fundamental forces of nature, gravity is an extremely weak force. So, In-order to find them we need to look for an extremely massive object to generate a gravitational wave strong enough to be measured on earth.
Some of those extremely massive objects are found in outer-space like:
- Rapidly accelerating black holes fuses into one supermassive black hole.
- Neutron stars.
- Massive stars blowing up at the ends of their life span.
As these objects are located millions of light-years away from us. By the time these waves reach us, they become very weak. This makes gravitational waves very hard to detect.
How can we detect gravitational waves?
Well, you can’t see the effects of gravitational waves, but you can measure how they affect an object they pass through. As these waves pass by anything, they will stretch and compress it. So, when a gravitational wave passes the Earth, it will make the planet slightly stretch in one direction and compress in the other. This is what LIGO (Laser Interferometer Gravitational-Wave Observatory) is designed to detect.
LIGO observatory has two arms that are stretched over 2 miles in an L-shape. When gravitational-wave pass through Earth, it causes stretching and squeezing of the planet. This will create slight changes in the length of the arms indicating the gravitational wave has passed through.
Well, it is not that easy to detect these waves, because the amount of change they create is extremely small. It is equivalent to the thousand part of the diameter of a proton. That’s why detecting these waves is an extremely challenging task. After a long wait, we finally detected these ripples of space-time on September 14, 2015.
Why the Discovery of Gravitational Waves so Important?
The discovery of gravitational waves opens up an entirely new era of Astrophysics. Scientists believe that gravitational waves will help us to know more about the early universe. Because these waves move through the very fabric of the space, which can carry the information about the origin of the universe that was created 13.8 billion years ago, and also help us to find answers for many -mysteries of the cosmos like dark matter, etc.
Let us wait and watch what these gravitational waves reveal in the future.