The gravitational waves were detected in February 2016, which was the very first time. After a few months, the scientists again detected another gravitational waves, and they found more details of how the waves were generated by spinning of black holes.
By the way, it sounds too far from our daily lives, doesn’t it? You may wonder about what those scientists are doing? What is the gravitational wave? Why is the black hole?
You can read the theoretical details in other “enthusiastic” websites or papers, but I would like to explain it in terms of what we have.
You know electromagnetic waves that are used for many of our technologies, such as cell phones, radios, wireless network, etc. In fact, the waves are created with electrically charged particles. More precisely, oscillation of the particles emit electromagnetic waves, which was experimentally proven a long time ago.
Now, we can get back to the gravitational wave. Gravity is induced by its mass. If we analogize this to the electromagnetic wave, oscillation of mass can generate the wave of gravity. That is also derived from what Einstein predicted.
Then, why was it really difficult to detect the gravitational wave? This is because the gravitational force is way too much weaker than the electromagnetic force. It depends on particles, but if the electromagnetic force is 1, the gravitational force is 0.0000000000 0000000000 0000000000 0000000001.
Therefore, in order to detect the gravitational wave, the mass to be oscillated must be very large. Black holes are actually very massive.
Let’s summarize it. The gravitational waves are similar to electromagnetic waves. However, the gravitational waves are very weak, so the massive black holes had to be used for the experiment and the technologies also had to be highly sophisticated.