Simply, gravitational waves are ripples in the fabric of space and time. However, exploring that itself is confusing. If space was a giant trampoline, things that have mass would cause the trampoline to bend; the more mass something has the more the trampoline is distorted. Thus, the more mass something has, the more space gets bent and distorted by gravity.
The reason Earth goes around the sun is because the sun is very massive and causes a large distortion of space and time. So if you roll a marble on the trampoline around say something larger like a bowling ball in a straight line, it will move in a circle because of the distortion. There is no actual force pulling planets, just the bending of space.
Gravitational waves are produced whenever masses accelerate, changing the distortion of space. Everything with mass and energy can make them — just waving your hand creates gravitational waves, but they are virtually undetectable. Gravity is relatively weak in the scale of other forces in the universe, so you need something very massive while moving very fast to make ripples big enough to detect. The two most common masses looked at are black holes and neutron stars.
It takes a lot to observe this phenomenon. It is observed by measuring the space between two things. Gravitational waves cause two points to get stretched or compressed, but you can’t just observe them by measuring because the ruler would be stretched as well. There is one ruler that does not get stretched, and that is the speed of light. If the space between two objects is stretched, the time it takes light to travel from point A to point B would increase, and it the space is compressed the light takes less time to go from point A to point B. Scientists do this by using LIGO.
LIGO’s is a laser interferometer gravitational wave observatory. It has 4 kilometer (2.5 mile) long tunnels and uses a laser to measure the distance between the ends of the tunnels. When a wave comes through, it stretches space in one direction and compresses it in the other. By measuring the lasers as they bounce between different points, physicists can determine if the space has compressed or stretched. The precision needed is extraordinary. To detect a gravitational wave, you need to measure a change in length by one part in 100,000,000,000,000,000,000,000. That’s like being able to tell a stick 1,000,000,000,000,000,000,000 meters long shrunk by one millimeter.
The effect of a gravitational wave is so miniscule that it gets confused with other “noise” or waves. So scientists need to use a smart data analysis technique. Scientists are hoping to identify the patterns of these waves by measuring what they get versus what they expect. It is almost like trying to hear someone in a loud party.
Scientists have been searching for these waves for over a decade and have finally found them, after upgrades to LIGO. The importance of this discovery is the fact that it gives us a whole new way to observe, explore and research space.
Waves from the Big Bang would tell us about how the universe was formed. Waves also form when black holes collide, which is actually the way they were detected, supernovas explode or massive neutron stars wiggle. Detecting these cosmic events, give us insight to the extreme forces of the universe.
Gravitational waves can also help scientists to understand the most fundamental laws of the universe, as predicted by Einstein with his General Theory of Relativity. Finding them could prove the theory correct or show where it is wrong. It is helping us discover the theory of everything.