It took 100 years, but finally, scientists proved Albert Einstein's theory that gravitational waves exist.
The waves were predicted as part of Einstein's General Theory of Relativity nearly 100 years ago. It was the theory of the physics behind the workings of our world and the universe.
The idea was that the waves are like ripples in space, caused by some of the violent and energetic processes in the Universe. For example, two black holes crashing into each other.
Now a group of scientists, including ones from from CalTech, MIT and the LIGO Scientific Collaboration finally found the gravitational waves.
David Reitze is the executive director of the LIGO observatory at CalTech.
"We have detected gravitational waves. We did it! (applause)"
Reitze spoke with others at a press conference in Washington, DC this past week. The scientists announced they were able to see ripples in the fabric of space time.
This is what the waves sounded like. Listen for the "chirp" sound at the end:
What are these gravitational waves? Well, imagine throwing a rock into a pond. When the rock hits the flat surface of the water, it creates ripples or waves. Spacetime is like the surface of the water. So that means gravitational waves are like the ripples moving out from where the rock hits the water.
It might be hard to understand, but those gravitational waves expand and contract space and time as they move through space. And when they get to the Earth, the waves pass through, and contract and expand the planet as the wave goes by.
It was Einstein who said these gravitational waves should be observable.
But these are not huge waves. They are very, very small, which is why it took so long to find them. You cannot see them with your eyes. They are smaller than the size of an atom.
How did the scientists find them?
They used a giant scientific tool called LIGO—which stands for the Laser Interferometer Gravitational-Wave Observatory. The billion-dollar LIGO project is two L-shaped observatories. One is in Louisiana and one in Washington state.
Their job was to watch for these gravitational waves. They have been looking on and off since 2002.
For years, scientists have been watching two black holes in another galaxy faraway. The two were spinning around each other, moving closer and closer together. When they finally crashed into each other, it was with such power and force, that gravitational waves rang throughout the universe, like a giant bell.
Those waves, traveling at the speed of light, finally reached the Earth, some 1.3 billion years later. They are the same waves that the scientists announced this past week.
The National Science Foundation tweeted that each of the black holes was thought to be 29 to 36 times the mass of our sun.
So, what does this discovery mean?
Abhay Ashtekar is a Penn State physicist, who was not on the discovery team. He said:
"Our understanding of the heavens changed dramatically."
I'm Anne Ball.
1.gravitational adj. [力] 重力的，[力] 引力的
A neutron star has a gravitational field strong enough to generate X-rays.
2.ripple n. 波纹；涟漪；[物] 涟波 vi. 起潺潺声 vt. 在…上形成波痕
Gleaming ripples cut the lake's surface.
3.chirp n. 唧唧声；喳喳声；[通信] 啁啾声 vi. 吱喳而鸣；尖声地说；咂嘴打招呼 vt. 吱喳而鸣；尖声地说；咂嘴向…打招呼
The crickets chirped faster and louder.
4.observable adj. 显著的；觉察得到的；看得见的 n. [物] 可观察量；感觉到的事物
Mars is too faint and too low in the sky to be observable.
5.tweet n. 小鸟叫声；自录音再现装置发出的高音；推特 vi. 吱吱地叫；啾鸣
Avoid sending a tweet in the heat of the moment.
1.They used a giant scientific tool called LIGO—which stands for the Laser Interferometer Gravitational-Wave Observatory.
stand for 代表；支持；象征；担任…的候选人
AIDS stands for Acquired Immune Deficiency Syndrome.
I would like to see him stand for re-election.
2.Their job was to watch for these gravitational waves. They have been looking on and off since 2002.
on and off 断断续续地，不时地
Sam was flicking a flashlight on and off.
It rained on and off all day.