Gravity Waves

[Emma]

Last year on September 15, the LIGO (Laser Interferometer Gravitational-Wave Observatory) and Virgo interferometer detected the gravitational wave of the collision of two binary black holes. They spent the last several months checking their observations to make sure that what they saw, actually happened and wasn't a glitch (like the infamous faster-than-light mistaken observation not too long ago). Yesterday, February 11th, they announced that they have confirmed their findings.

This really is a revolutionary discovery in science and absolutely is the most important one made thus far in this century. Our observations very closely matched what was predicted by General Relativity. And that made it all the more exciting.

All the observational data indicates that only a black hole-black hole pair could have given us the results we observed. A pair of any other objects, like a black hole with a neutron star, would not have been able to orbit each other with those the masses that were observed (35 solar masses for the larger object, 29 for the smaller) at the distances observed (less than 250 km), and at the observed frequency of 75 Hz.

“This is transformational,” said Prof Alberto Vecchio, of the University of Birmingham, and one of the researchers at Ligo. “We have observed the universe through light so far. But we can only see part of what happens in the universe. Gravitational waves carry completely different information about phenomena in the universe. So we have opened a new way of listening to a broadcasting channel which will allow us to discover phenomena we have never seen before,” he said.

“This observation is truly incredible science and marks three milestones for physics: the direct detection of gravitational waves, the first detection of a binary black hole, and the most convincing evidence to date that nature’s black holes are the objects predicted by Einstein’s theory.”

https://www.theguardian.com/science...scovery-hailed-as-breakthrough-of-the-century

Before now we weren't even exactly sure that the objects we've been detecting that we've been calling black holes really were the black holes described by general relativity. And now thanks to this new observation, we know that indeed they are.

Here's a very simple simulation of what a merger of a binary black hole pair looks like and a visualization of the gravity waves it generates, which is what was detected.

 

[Mr. Ister]

I still don't fully understand the data output that we're seeing (and that video almost gave me a seizure) but I understand the importance of gravity in the space-time dimension so I at least have some semblance of perspective for the impact of this finding. I'm interested to see what other things we can directly apply this to now, versus things that will take decades to resolve using these new data collection methods.

 

[Emma]

It can be confusing yeah. The equations themselves that were used to predict this are too complicated for humans to complete quickly enough to be of any use, it has to be done by super computers. But the data itself can be understood. I can try to explain as best I can if people have any specific questions.

As far as the data is concerned, to the layman what's important is that the top two graphs, which represents the waves that we saw), look very much like the middle pair of graphs, which represent what the equations of general relativity assumed that such a wave generated by a paid of objects with the characteristics we observed ought to look like. And that was an extremely important part of this. As it backs up our understanding of Relativity and confirms that it has real world relevance that we can apply to future understanding of the universe. Which can lead to new technologies that have every day use for the common person, like how satellites are such a critical part of daily life now (and they depend on an understanding of general relativity to operate properly).

 

[Djinn]

Why is it every couple of years we still manage to learn something previously, completely unknown about gravity that has us going back to the beginning on just how the hell it works?

 

[Mr. Ister]

cause people still don't really know that much about stuff in general

 

[Emma]

I found a much better visualization of a black hole merger and what the gravity waves look like and how those graphs I listed are supposed to represent them.


Also worth watching is Professor Steven Hawking's thoughts about the finding.


He makes the same points I made before, as well as referencing how it also confirms some of the black hole theories he helped formulate in the 1970s. I understand everything he said, so if anyone has questions about and of it, I could try to explain.

Notably, it seems to have given us an opportunity to understanding the growth and evolution of black holes. Before now, we only had a reasonable understanding of brand new black holes newly formed from supernova explosions, and supermassive black holes at the centers of galaxies. We've had little exposure to mid ranged black holes of a few dozen solar masses. From our understanding, such black holes cannot form directly and they must grow to that size after initially forming. And our first direct observation that confirms the existence of relativity-described black holes just happened to be of the types of black holes we understand the least about, middle-sized ones of a few dozen solar masses. These two were 36 solar masses and 29 solar masses. And since what we observed was a collision between two of them, it confirms the idea that black holes gain mass by colliding and absorbing other black holes and that they don't have to be formed directly from more massive star (which we think are too unstable to exist and would have collapsed into much smaller black holes long before reaching sizes of a few dozen solar masses).

 

[Emma]

Well it has been a few months and now the LIGO detector has found another gravity wave from a second collision of black holes. This helps confirm that the first detection wasn't just a fluke. What is interesting is that the two black holes in this collision are much smaller than the ones in the previous collision. Because of their smaller size, they orbited each other a bit slower when they approached their final collision and the resulting gravity waves were visible to LIGO for a full second. And, the resulting black hole from the collision was a whole solar mass smaller than the two individual black holes were. Which means that a mass equal to the mass of our sun was converted directly into energy which would be 1.787 x 10^47 Joules, a ridiculously large number, roughly 137 times more energy than our sun will release in its entire lifetime before advancing to the red giant phase.

More about it here:
http://www.seeker.com/more-gravitational-waves-discovered-by-ligo-1860493586.html