“Gravitational waves are akin to sound waves that travelled through space at the speed of light. Up to now humanity has been deaf to the universe. Suddenly we know how to listen. The Universe has spoken and we have understood.” (source)
The quote above comes from David Blair, a gravitational researcher at the University of Western Australia. After 100 years of searching, physicists have finally confirmed the existence of Einstein’s gravitational waves. It is easily one of the biggest discoveries in astrophysics within the last century, and will no doubt help us to better understand the universe and the true nature of reality.
They detected these waves by observing the warping of space-time that was created by a collision between two black holes more than one billion light years from Earth. Scientists are saying that this first detection of these waves will usher in a completely new era for astronomy.
The research was conducted by the Ligo Collaboration, and was published today in the journal Physical Review Letters. LIGO is the laser interferometer gravitational wave observatory, and it works by bouncing lasers back and forth in two 4-km long ripples, allowing physicists to measure incredibly small changes in space-time.
“It is the first ever direct detection of gravitational waves; it’s the first ever direct detection of black holes and it is a confirmation of General Relativity because the property of these black holes agrees exactly with what Einstein predicted almost exactly 100 years ago.” (source)
So, what does this actually mean? According to Einstein’s theory of General Relativity, space-time can become curved by anything giant in the Universe. When dramatic, cataclysmic events occur, like stars exploding or black holes colliding, these curves can ripple out throughout space as gravitational waves. Think of it like dropping a rock into a pond; the force of the rock meeting the water creates a ripple effect.
The reason scientists have struggled to detect them for so long is because the ripples take so much time to reach us, and by the time they do they’re approximately one billionth of the diameter of an atom. They are produced by moving masses, and just like electromagnetic waves, they travel at the speed of light; while doing so they stretch and squash spacetime.
What’s also interesting about the discovery is that the signal almost perfectly matches up with what scientists predicted gravitational waves would look like, based on Einstein’s theory of General Relativity.
Here is a picture of the signal with the predictions overlaid:
According to LIGO researcher Eric Thrane from Monash University In Australia, “the discovery of this gravitational wave suggests that merging black holes are heavier and more numerous than many researchers previously believed. This bodes well for detection of large populations of distant black holes . . . It will be intriguing to see what other sources of gravitational waves are out there, waiting to be discovered.” (source)
Below is a little excerpt from Physical Review Letters that provides more details about LIGO, and the implications of this new discovery:
With Advanced LIGO’s result, we are entering the dawn of the age of gravitational wave astronomy: with this new tool, it is as though we are able to hear, when before we could only see. It is very significant that the first “sound” picked up by Advanced LIGO came from the merger of two black holes. These are objects we can’t see with electromagnetic radiation. The implications of gravitational-wave astronomy for astrophysics in the near future are dazzling. Multiple detections will allow us to study how often black holes merge in the cosmos and to test astrophysical models that describe the formation of binary systems [9, 10]. In this respect, it’s encouraging to note that LIGO may have already detected a second event; a very preliminary analysis suggests that if this event proves to have an astrophysical origin, then it is likely to also be from a black hole binary system. The detection of strong signals will also allow physicists to test the so-called no-hair theorem, which says that a black hole’s structure and dynamics depend only on its mass and spin. Observing gravitational waves from black holes might also tell us about the nature of gravity. Does gravity really behave as predicted by Einstein in the vicinity of black holes, where the fields are very strong? Can dark energy and the acceleration of the Universe be explained if we modify Einstein’s gravity? We are only just beginning to answer these questions – Physical Review Letters
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