What Is a Gravitational Wave? A gravitational wave is an invisible (yet incredibly fast) ripple in space. Gravitational waves speed is same as speed of light (186,000 miles per second). These waves squeeze and stretch anything in their path as they pass by that means that they can also squeeze and stretch the timeline. This wave is an invisible ripple in space. Watch the video to know more about gravitational waves theory - https://youtu.be/EKHQav_oH6c Related article: What Happens if a Asteroid Hits the Earth? The Discovery We’ve known about gravitational waves for a long time. More than 100 years ago, a great scientist named Albert Einstein came up with many ideas about gravity and space. Einstein predicted that something special happens when two bodies—such as planets or stars—orbit each other. He believed that this kind of movement could cause ripples in space. These ripples would spread out like the ripples in a pond when a stone is tossed in. Scientists call these ripples of space gravitational waves. What causes gravitational waves? The most powerful gravitational waves are created when objects move at very high speeds. Some examples of events that could cause a gravitational wave are: \tWhen a star explodes asymmetrically (called a supernova) \tAlso when two big stars orbit each other \tWhen two black holes orbit each other and merge But these types of objects that create gravitational waves are far away. And sometimes, these events only cause small, weak waves. The waves are then very weak by the time they reach Earth. This makes this waves hard to detect. How do we know that gravitational waves exist? In 2015, scientists detected gravitational waves for the very first time. They used a very sensitive instrument called LIGO (Laser Interferometer Gravitational-Wave Observatory). These first gravitational waves happened when two black holes crashed into one another. The collision happened 1.3 billion years ago. But, the ripples didn’t make it to Earth until 2015. How are these waves detected? When a gravitational wave passes by Earth, it squeezes and stretches space. LIGO can detect this squeezing and stretching. Each LIGO observatory has two “arms” that are each more than 2 miles (4 kilometers) long. A passing gravitational wave causes the length of the arms to change slightly. The observatory uses lasers, mirrors, and extremely sensitive instruments to detect these tiny changes. The first detection of gravitational waves was a very important event in science. Before this, just about everything we knew about the universe came from studying waves of light. Now we have a new way to learn about the universe—by studying waves of gravity.