APOD: LIGO Detects Gravitational Waves (2016 Feb 11)

Comments and questions about the APOD on the main view screen.
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Re: APOD: LIGO Detects Gravitational Waves (2016 Feb 11)

Post by Chris Peterson » Thu Feb 11, 2016 5:00 pm

Galaxian wrote:Oh, and Chris, GMT was an internationally recognised standard before your colony had the population of Tonga.
And now it's obsolete and deprecated.
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Re: APOD: APOD Place Holder (2016 Feb 11)

Post by Guest » Thu Feb 11, 2016 5:01 pm

Galaxian wrote:For the same reason USAliens...
Please define "USAliens"

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Re: APOD: LIGO Detects Gravitational Waves (2016 Feb 11)

Post by Chris Peterson » Thu Feb 11, 2016 5:01 pm

This announcement inspires a most peculiar feeling in me, intense excitement combined with an utter lack of surprise.
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Re: APOD: LIGO Detects Gravitational Waves (2016 Feb 11)

Post by Ron-Astro Pharmacist » Thu Feb 11, 2016 5:16 pm

I thought that was a tremendously well delivered press conference with many perspectives delivered from the standpoints the various principle investigators and many good questions answered. Very revealing - the collaborations involved and those wishing to be involved (like the US in LISA?)

I was questioning the use of interferometers a couple of days ago and I can humbly say that leather doesn’t taste very good. :thumb_down: Hmmm. Now I’m looking forward to better ones. :thumb_up: I hope we see many signals from all over the sky in a short time frame to better pinpoint other space-time disturbances which will help explain, as of today, our less puzzling universe. :doughnut:
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Re: APOD: LIGO Detects Gravitational Waves (2016 Feb 11)

Post by ShaileshS » Thu Feb 11, 2016 5:17 pm

Merger of 2 giant black holes took only 0.3 seconds ? That's it ? I thought it'd be take much longer. Maybe thousands of years if not millions even if it's very last stage of merger. What am I missing ?

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Re: APOD: LIGO Detects Gravitational Waves (2016 Feb 11)

Post by Cousin Ricky » Thu Feb 11, 2016 5:29 pm

Galaxian wrote:Yes, the engineers should celebrate the fine work they've done but this doesn't advance Science one bit.

Maybe, when Amazon sells gravity telescopes for amateurs at less than a hundred quid this event will be seen as the start of something but today it's just yet one more in a long, long, line of confirmations of GR.
And those are boring.
I disagree. Without these confirmations, how would we know whether or not we are correct? And isn't knowing (insofar as that term has meaning in science) that we're correct an advancement over predicting that we're correct?
Galaxian wrote:New physics would have been cool.
Very cool!

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Re: APOD: APOD Place Holder (2016 Feb 11)

Post by Cousin Ricky » Thu Feb 11, 2016 5:39 pm

phlloydl wrote:Why is it that Americans assume all the world understands their time zones? This is an astronomy-related web page and astronomers work in UT. So what is "11:00 am Eastern Tome" in UT, please?
That’s nothing. I’ve seen the word “miles” used in APOD explanations.

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Re: APOD: LIGO Detects Gravitational Waves (2016 Feb 11)

Post by Chris Peterson » Thu Feb 11, 2016 5:43 pm

Cousin Ricky wrote:
Galaxian wrote:Yes, the engineers should celebrate the fine work they've done but this doesn't advance Science one bit.

Maybe, when Amazon sells gravity telescopes for amateurs at less than a hundred quid this event will be seen as the start of something but today it's just yet one more in a long, long, line of confirmations of GR.
And those are boring.
I disagree. Without these confirmations, how would we know whether or not we are correct? And isn't knowing (insofar as that term has meaning in science) that we're correct an advancement over predicting that we're correct?
Of course, you're absolutely right, and this does advance science. The confirmation of theories about gravity, black holes, and black hole dynamics is important, even if not unexpected. However, arguably even more important is the proof-of-concept of gravitational wave detectors, which will now boost funding for such instruments and result in routine gravitational wave astronomy in the near future. That represents a radical advance in the sort of scientific research that will be possible. For the first time we'll see beyond the edge of the observable universe defined by electromagnetic radiation, and be able to observe things right to the instant of the Big Bang. We'll refine our understanding of cosmology in very important ways.
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Re: APOD: APOD Place Holder (2016 Feb 11)

Post by Cousin Ricky » Thu Feb 11, 2016 5:46 pm

Galaxian wrote:For the same reason USAliens (Not "Americans", as Mexicans and Canadians and South Americans all recognise that different countries with different customs exist) [...]
If we were writing in Spanish here, you’d have a point with your terminology. In Latin America, the word América does refer to the entire region. But in the English-speaking world, American without qualifiers is understood to refer to the United States of America.

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Re: APOD: LIGO Detects Gravitational Waves (2016 Feb 11)

Post by Boomer12k » Thu Feb 11, 2016 5:51 pm

Looks like I have to EAT CROW :o ...munch, munch, munch....good thing I am not a betting man.... :lol2:

Detected....5 sigma....Confirmed.....Exists.....

I guess they ARE generated...and DO...travel outward from the source....and appear to travel VAST distances....I was wrong on all counts.

Should have read more articles about them....AND I WILL...

I would rather be surprised and be wrong...than be Disappointed....

I am not Fred Hoyle, and will accept the evidence....

LONG LIVE ALBERT!!! Hope he gets a Nobel Prize....He certainly deserves it.

We are being stretched and squeezed....like a CARTOON.... :lol2:
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Re: APOD: APOD Place Holder (2016 Feb 11)

Post by BMAONE23 » Thu Feb 11, 2016 5:59 pm

Cousin Ricky wrote:Can't they just compress space-time and get us the news now? :mrgreen:
Obviously they did but it was just at the edge of the Event Horizon and needed the proper time dilation to Radiate outward

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Re: APOD: APOD Place Holder (2016 Feb 11)

Post by BMAONE23 » Thu Feb 11, 2016 6:00 pm

Guest wrote:
Galaxian wrote:For the same reason USAliens...
Please define "USAliens"
Those are USNon-residents

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Re: APOD: LIGO Detects Gravitational Waves (2016 Feb 11)

Post by Chris Peterson » Thu Feb 11, 2016 6:08 pm

Boomer12k wrote:LONG LIVE ALBERT!!! Hope he gets a Nobel Prize....He certainly deserves it.
He already did, although not for relativity. And since the Prize only goes to people who are alive, he can't get another.

The next prize in physics should go to Thorne, Drever, and Weiss. Anything else would devalue the Physics prize as much as the nomination of Trump for the Peace Prize devalued it.
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Re: APOD: LIGO Detects Gravitational Waves (2016 Feb 11)

Post by bystander » Thu Feb 11, 2016 6:15 pm

bystander wrote:Gravitational Waves Detected 100 Years After Einstein's Prediction
LIGO | NSF | Caltech | MIT | 2016 Feb 11

Gravitational Waves Caught in the Act
American Physical Society | News | 2016 Feb 11

Viewpoint: The First Sounds of Merging Black Holes
American Physical Society | Physics | 2016 Feb 11

Observation of Gravitational Waves from a Binary Black Hole Merger - B. P. Abbott et al (LIGO Scientific Collaboration, Virgo Collaboration) Astrophysical Implications of the Binary Black Hole Merger GW150914 - B. P. Abbott et al
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Re: APOD: LIGO Detects Gravitational Waves (2016 Feb 11)

Post by bls0326 » Thu Feb 11, 2016 6:16 pm

Able to pick up something that happened in less than half a second, 1.3 billion years ago. simply amazing. I have wondered how black holes got rid of all that energy from the inflow of mass.

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Re: APOD: LIGO Detects Gravitational Waves (2016 Feb 11)

Post by Chris Peterson » Thu Feb 11, 2016 6:25 pm

bls0326 wrote:Able to pick up something that happened in less than half a second, 1.3 billion years ago. simply amazing. I have wondered how black holes got rid of all that energy from the inflow of mass.
These were stellar mass black holes, which means they probably acquired very little mass from inflowing material. They were simply the mass of the remaining material after their parent suns went supernova. The resulting black hole from their merger was equal in mass to the sum of the two, less an energy-mass equivalent that was given up in the form of gravitational radiation- about 5% of the total mass.
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Re: APOD: LIGO Detects Gravitational Waves (2016 Feb 11)

Post by tomatoherd » Thu Feb 11, 2016 6:41 pm

Excuse my ignorance. But where DOES all that energy go? Re: the sticky bead thought experiment (now confirmed), if such an event put out "50 times" the peak energy of the observable universe, was "only" one-twentieth (or less) of said universe's width away from us, why weren't we all fried to oblivion? If a nearby much less "luminous" supernova could harm us, why not that? And surely there have been closer inspirals of black holes before LIGO was online. Does the bead heat up or not? Is there friction or not? Where does all that energy go??? And if that "radiation" doesn't have any local effects, maybe it IS just "in essence ripples in coordinates, with no physical meaning", like Eddington thought.

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Re: APOD: LIGO Detects Gravitational Waves (2016 Feb 11)

Post by Chris Peterson » Thu Feb 11, 2016 6:55 pm

tomatoherd wrote:Excuse my ignorance. But where DOES all that energy go? Re: the sticky bead thought experiment (now confirmed), if such an event put out "50 times" the peak energy of the observable universe, was "only" one-twentieth (or less) of said universe's width away from us, why weren't we all fried to oblivion? If a nearby much less "luminous" supernova could harm us, why not that? And surely there have been closer inspirals of black holes before LIGO was online. Does the bead heat up or not? Is there friction or not? Where does all that energy go??? And if that "radiation" doesn't have any local effects, maybe it IS just "in essence ripples in coordinates, with no physical meaning", like Eddington thought.
You have to consider the total energy, not just the intensity. This was a lot of energy, but released very rapidly.

Energy is conserved... it doesn't have to "go" anywhere. In this case, the energy density is very low, because it has been spread out by the inverse square law. You have an incredible amount of energy (three solar masses!), but spread out over an immense volume (almost a surface, but still very large). And it's not a destructive kind of energy. A very small part of it is converted into kinetic energy when it encounters mass. So the piece of the wave that passed through the Earth actually stretched the planet and resulted in the generation of some heat (gravitational energy converted to mechanical energy). Not enough to detect, but very real.

Something like this could happen very nearby and not pose any risk from the gravitational radiation. I'm not sure if a black hole merger also produces enough electromagnetic radiation to be dangerous for some distance, but I think that would be a larger concern than the gravitational waves.
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Re: APOD: LIGO Detects Gravitational Waves (2016 Feb 11)

Post by neufer » Thu Feb 11, 2016 7:06 pm

ShaileshS wrote:
Merger of 2 giant black holes took only 0.3 seconds ? That's it ? I thought it'd be take much longer. Maybe thousands of years if not millions even if it's very last stage of merger. What am I missing ?
The merger did take thousands or millions of years; however, only the last 0.3 seconds was violent enough to produce a visible detectable signal in the advanced LIGO (that, by the way, was just turned on). The next event to take place may generate a long enough quasi periodic signal that, perhaps, we can detect the final months or so as well using signal processing.
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Re: APOD: LIGO Detects Gravitational Waves (2016 Feb 11)

Post by Chris Peterson » Thu Feb 11, 2016 7:17 pm

neufer wrote:
ShaileshS wrote:
Merger of 2 giant black holes took only 0.3 seconds ? That's it ? I thought it'd be take much longer. Maybe thousands of years if not millions even if it's very last stage of merger. What am I missing ?
The merger did take thousands or millions of years; however, only the last 0.3 seconds was violent enough to produce a visible detectable signal in the advanced LIGO (that, by the way, was just turned on). The next event to take place may generate a long enough quasi periodic signal that, perhaps, we can detect the final months or so as well using signal processing.
You might argue that it's semantics, but the merger only took a tiny fraction of a second. Before that was the long process leading up to the merger.
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Re: APOD: LIGO Detects Gravitational Waves (2016 Feb 11)

Post by worley » Thu Feb 11, 2016 7:36 pm

tomatoherd wrote:But where DOES all that energy go? Re: the sticky bead thought experiment (now confirmed), if such an event put out "50 times" the peak energy of the observable universe, was "only" one-twentieth (or less) of said universe's width away from us, why weren't we all fried to oblivion? ... And if that "radiation" doesn't have any local effects, maybe it IS just "in essence ripples in coordinates, with no physical meaning", like Eddington thought.
The merger produced energy at a very high rate for a very short period of time. So the total energy was large (something like 50 times what is released by the brightest supernovas), but not enough to fry the universe. But in the intervening billion years, that energy spreads out over an enormous volume, so the energy density of the wave (energy per unit volume) is very small. On top of that, we aren't very good absorbers of gravitational waves, most of the energy propagates through us.

Compare with the statement I copied from somewhere, "It is estimated that for an instant in 1987 on the earth the neutrino luminosity of SN1987A was as large as the visible-light luminosity of the *entire universe*."

However, this does show how Eddington was wrong. Gravitational waves do show up as ripples in the coordinates, but since the ripples have an energy density, they have physical meaning.

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Re: APOD: LIGO Detects Gravitational Waves (2016 Feb 11)

Post by Craig Willford » Thu Feb 11, 2016 7:40 pm

I haven't been this excited by news coming from the astronomical community for a very very long time. This is really big news! Congratulations to all the team at LIGO!

Now that we have data of an event superimposed over the noise (see the signals at the far left of the image) perhaps we can start to draw some conclusions about the sources of the noise too. Sometimes it is amazing how you can tease out information out of seemingly random data.

So if these black holes were only 29 and 36 times the mass of our sun, then we are not even close to talking about merger of galactic cores. I would expect even the black holes holding together globular clusters to be well above that size. What are the thoughts on how common are black holes of this size, currently and billions of years ago and what are the thoughts on the origins of them?

If power output from the conversion of 3 solar masses to gravitational waves put out, for that fractional second, 50 times that of the whole universe, perhaps quite a bit of energy in the universe is tied up in gravitational waves still rippling.

Of course that energy gets absorbed (else LIGO would not have been able to detect it). How much did this event in September heat up the Earth? I presume it is indetectably small.

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Re: APOD: LIGO Detects Gravitational Waves (2016 Feb 11)

Post by neufer » Thu Feb 11, 2016 8:08 pm

Chris Peterson wrote:
Something like this could happen very nearby and not pose any risk from the gravitational radiation. I'm not sure if a black hole merger also produces enough electromagnetic radiation to be dangerous for some distance, but I think that would be a larger concern than the gravitational waves.
Advanced Weber bars that are cryogenically cooled, with superconducting quantum interference devices ( :!: ) are still 100,000 times less sensitive to such gravitational wave strain than are advanced LIGOs. Gravitational radiation strain drops off only linearly with distance so an advanced Weber bar could only have observed something like this from within our own galaxy (i.e., at a distance of ~ 13,000 light years). Needless to say, it wouldn't have had a noticeably affect on anything else.
https://en.wikipedia.org/wiki/Gravitational_wave#Detection wrote:
<<A simple device theorised to detect the expected wave motion is called a Weber bar — a large, solid bar of metal isolated from outside vibrations. This type of instrument was the first type of gravitational wave detector. Strains in space due to an incident gravitational wave excite the bar's resonant frequency and could thus be amplified to detectable levels. Conceivably, a nearby supernova might be strong enough to be seen without resonant amplification. With this instrument, Joseph Weber claimed to have detected daily signals of gravitational waves. His results, however, were contested in 1974 by physicists Richard Garwin and David Douglass. Modern forms of the Weber bar are still operated, cryogenically cooled, with superconducting quantum interference devices to detect vibration. Weber bars are not sensitive enough to detect anything but extremely powerful gravitational waves.>>
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Re: APOD: LIGO Detects Gravitational Waves (2016 Feb 11)

Post by tomatoherd » Thu Feb 11, 2016 8:14 pm

Worley wrote: " But in the intervening billion years, that energy spreads out over an enormous volume, so the energy density of the wave (energy per unit volume) is very small." And Chris wrote: "In this case, the energy density is very low, because it has been spread out by the inverse square law. You have an incredible amount of energy (three solar masses!), but spread out over an immense volume (almost a surface, but still very large)."

I realize this. But surely no one is implying that a black hole-black hole merger has never occurred in our own galaxy, just 'next door'?

Worley wrote: "On top of that, we aren't very good absorbers of gravitational waves, most of the energy propagates through us."

If local effects to that much energy are that small, even intra-galactically, then Eddington was wrong 'on a technicality' only.

And Chris wrote: "Energy is conserved... it doesn't have to "go" anywhere."

Ah... but it does. It's headed somewhere. Maybe out to the edge of the Universe. Something will absorb it; maybe nothing until it warms the feet of God.

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Re: APOD: LIGO Detects Gravitational Waves (2016 Feb 11)

Post by Chris Peterson » Thu Feb 11, 2016 8:22 pm

tomatoherd wrote:And Chris wrote: "Energy is conserved... it doesn't have to "go" anywhere."

Ah... but it does. It's headed somewhere. Maybe out to the edge of the Universe. Something will absorb it; maybe nothing until it warms the feet of God.
Well, it "goes somewhere" in the sense that it propagates. But it isn't doing any work, it isn't being transformed into other kinds of energy, except for the tiny fraction that actually interacts with matter.
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