Thursday: Scientists to provide update on gravitational waves
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11-02-2016, 10:26 PM
RE: Thursday: Scientists to provide update on gravitational waves
Moms, here is a nice video that makes what I said earlier much clearer.

https://youtu.be/s06_jRK939I
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11-02-2016, 11:00 PM
RE: Thursday: Scientists to provide update on gravitational waves
I saw a segment about this on the nightly news, earlier!

Glad to have heard it from there first! Scientific announcements should happen more often! Thumbsup

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11-02-2016, 11:14 PM
RE: Thursday: Scientists to provide update on gravitational waves
(11-02-2016 11:00 PM)TheGulegon Wrote:  I saw a segment about this on the nightly news, earlier!

Glad to have heard it from there first! Scientific announcements should happen more often! Thumbsup

Yes, loud and often. Yes As opposed some person's butt being in the news. No
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11-02-2016, 11:30 PM
RE: Thursday: Scientists to provide update on gravitational waves
I am curious but mostly ignorant. The updated wikipedia entry about this describes a 7 millisecond distortion. How does a distortion like that manifest? It seems like GPS or communication with long distance probes would be disrupted somehow if time... flexed? Thickened? Surged?

This event happened 1.5 billion years ago, and it got to us last September. It traveled at some non-instantaneous speed. So presumably at some point this had already happened to, say, Vega but not yet to us. What would be different there and here in the time between?

It's hard for me to even frame my questions well.
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12-02-2016, 10:36 AM
RE: Thursday: Scientists to provide update on gravitational waves
(11-02-2016 11:30 PM)I Am Wrote:  I am curious but mostly ignorant. The updated wikipedia entry about this describes a 7 millisecond distortion. How does a distortion like that manifest? It seems like GPS or communication with long distance probes would be disrupted somehow if time... flexed? Thickened? Surged?

This event happened 1.5 billion years ago, and it got to us last September. It traveled at some non-instantaneous speed. So presumably at some point this had already happened to, say, Vega but not yet to us. What would be different there and here in the time between?

It's hard for me to even frame my questions well.

It is, essentially, the difference in path length for two beams of light. You compare the phase to measure that difference - that's what any interferometer does.
(light oscillates as it travels - if the two beams travel different lengths, they will have oscillated different amounts, which is measurable)

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17-02-2016, 07:31 PM
RE: Thursday: Scientists to provide update on gravitational waves
Gravity wave travel at the speed of light. Nothing's supposed to go faster because that might violate causality, which is the sort of thing that only grandfather-murdering bastards do. Personally, I'm hoping that this is one bit that Einstein got wrong or that we can find a way to sneak around it.

Gravity waves are incredibly hard to detect because they have an incredibly minute effect on us. That's party because gravity in general isn't a particularly strong force. You need to assemble a decent sized asteroid before you notice it's pull and that's right under your feet. This happened 1.3 billion light-years away. So the net effect on the 4 km long detectors was to change their distance by about 1/10,000th of the size of a proton. No, I don't know how they measure that. Don't worry about adjusting your clocks any time soon though.

Gravity waves are produced by any accelerating mass. The gravity waves produced when you tromp on your gas pedal are so ridiculously small that they're probably undetectable. Though I expect the NSA to give it a try. And acceleration includes rotary motion like orbitting. So to make gravity waves that we can detect, we need a really big mass that's in a decently fast orbit, or is reasonably close. Neutron stars, black holes, Yo Mama, that sort of thing. Happily, there aren't many nearby so we need them to be going fast to detect them.

Once upon a time there were two black holes. That's less accurate than "circa 1.3 billion years ago" but much classier. All scientific papers should start this way. The smaller one was a mere 29 times the mass of our sun, the larger was a chubby 36 solar masses. They had spent their lives slowly orbitting one another making gravity waves that hardly rattled the dishes in neighboring solar systems. But making gravity waves takes energy. Energy that is deducted from orbital velocity. Over time the black holes slowly began to orbit closer, and closer. Of course, orbitting closer means orbitting faster. Orbitting faster means making bigger waves, loosing energy faster, spiralling inward more rapidly.

It's a catastrophic runaway called an "inspiral". Sort of analogous to areobraking except without the air and the more energy you loose the faster you go. In the last instants before their merger, these two black holes were moving at about 60% of the speed of light. The black hole created by the merger was only 62 solar masses because in the last few milliseconds of their inspiral the parent black holes converted roughly three times the mass of our sun into energy, mosty gravitational waves. The power output was roughly 50 times greater than the rest of the observable universe and shattered the record for the most energetic event ever observed by our species.

Why is this cool?

- It poved that Einstein was right. 'Cause we needed reminding. It is a pretty nifty confirmation of the theory of special relativity.

- We have discovered that binary black holes exist and have observed their merger. We have watched black holes mate. That's right, a novel medium for observing the universe and somebody's already using it for porn. Or for the sentimental folks in the crowd, last September you got a very gentle hug from a new born black hole 1.3 billion light-years away.

- Unlike light, gravity barely even notices matter. That's a problem when you're trying to measure it but it's brilliant as an observational tool. If we can get gravity wave detectors sensitive enough to measure more regular and reliable sources then we ought to be able to use it to image the interior of the sun or look into the heart of the Milky Way. Fun stuff like that.

- Gravity waves can see dark matter. It's the one force that the damned stuff does interact with so we might be able to use it to observe the dark matter structure of the universe.

- The cosmic gravity wave background. The little white lie that's told about the cosmic microwave background is that it's the light from the Big Bang. That isn't quite right. The early universe is so intensely energetic that light can't go anywhere. The entire thing is one ridiculously opaque fog of super-heated plasma. The CMB is actually light from the universe when it had cooled for about 400,000 years. We can't see back any earlier. If we can make gravity wave detectors that are very, very accurate we might be able to detect the CGWB from when the universe was less than a yoctasecond (billionth of a billionth of a billionth of a second) old. When it was about the size of a beach ball.

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Flesh and blood of a dead star, slain in the apocalypse of supernova, resurrected by four billion years of continuous autocatalytic reaction and crowned with the emergent property of sentience in the dream that the universe might one day understand itself.
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