A gravitational wave is an invisible (very fast) wave in space. Gravitational waves travel at the speed of light (or 186,000 miles per second). As these waves travel, anything in their path is compressed and expanded.
We have known about these for a long time. More than 100 years ago, the great scientist Albert Einstein made many ideas about gravity and space.
Einstein predicted that something special would happen when two large objects, such as planets or stars, orbit each other. He believed that such motions could cause ripples in space. When a stone is thrown, these ripples spread like ripples in a pond. Scientists call these space ripples gravitational waves.
What causes gravitational waves?
When objects move at very high speeds, very powerful gravitational waves are created. Some examples of events that can cause these are:
- When a Star Explodes (Supernova)
- When two massive stars orbit each other
- When two black holes orbit each other and merge
But these types of objects that cause gravitational waves are very far away from us. And sometimes such events produce only small or weak gravitational waves. Therefore, these waves are very weak when they reach the earth. This makes detecting these waves a difficult task.
How do we know that gravitational waves exist?
In 2015, scientists first detected gravitational waves. For this, they used a very sensitive instrument called LIGO (Laser Interferometer Gravitational-Wave Observatory). These types of waves are caused by the collision of two black holes. This black hole collision happened 1.3 billion years ago. But, these waves did not reach Earth until 2015!
Einstein was right!
The first detection of these is a very important event in world science. Previously, everything we knew about the universe came from studying light waves. By studying these, we now have a new way to learn about the universe.
Gravitational waves help us learn many new things about our universe. We can also learn a lot about gravity from this!
How to detect gravitational waves?
As this wave travels through the Earth, space contracts and expands. LIGO can detect this contraction and expansion. Each LIGO observatory has two “arms” that are more than 2 miles (4 km) long. As a gravitational wave passes through LIGO’s arms, the length of the arms changes by a very small amount. The LIGO observatory uses lasers, mirrors and ultra-sensitive instruments to detect these tiny changes.
This process is better explained in the following animation. (astrolearn)
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