Physics Discussion Thread

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member_29325
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Re: Physics Thread.

Post by member_29325 »

It's been over a year and that hasn't yet wiped us out, so what happened? They broke up and flew apart?
The two black holes combined and formed a larger black hole...being safely a few million light years away, we could only hear the Death-metal-vocals type of disturbance here...thankfully. Good question -- that implies either even stars produce weak waves (unlikely given the amount of mass turned to gravitational energy) or the gravity waves weaken over distance for some reason. Not explained in the pop sci material on this topic, and the original paper is TLO;DR.
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Re: Physics Thread.

Post by UlanBatori »

Now the other obvious question which will be lynched as "con-descending", "silly", "disgraceful" etc:

So these Einsteins are claiming that they detected a gravitational wave BECAUSE TWO black holes collided - and then turning around and saying: AHA! This is the first real evidence of the EXISTENCE OF BLACK HOLES.

As I saw it described (kindergarten/CNN level as befits me) some graduate student is jumping up and down claiming that he had modeled two black holes colliding, and this signal was EXACTLY like that. This is called SFP (Self-fulfilling prophecy).

Isn't this circular logic? What if it was something completely else, like someone pulling the flush on the ISS? Gurgle-gurgle, whoosh-gurgle-gurgle, as I recall.. :idea: If I were to construct an acoustic model of that, convert it to a gravitational equivalent and convert back, I would something like what they have posted on-line.

Both LIGOs were in the western USA, hain? Where was the ISS at the time I wonder....

What if it was (ThiruV's words, absolutely mine since I am so :eek: by this discovery and anyway, I fell off a tomato truck only yesterday):

What if it IS a DeathMetal Band that they detected? The undergraduate (wo)manning the detector late at night sent the music to her two buddies in the two places, and those two happened to open the file at the same time, with volume turned up high? And they just happened to be directing their Smartphone music feed through the LIGO's $B A/D converters and Sub-Sub-Sub-Woofers because that is so cool?

OK, I will be using a LIGO detector to detect the Gravitas Wave from that, amidst the Silence Of Phyicists Ignoring Disrespectful Posts. :shock:

P.S. In for a paisa, in for a karod. U need to read the deep scientific paper on MOTM That Paper outlines the theory that The Duchy of Fenwich wanted to construct a gold-plated pakistan for the Duke, and the entire US-Soviet-UN funded Space Program had that as its total objective.
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Re: Physics Thread.

Post by UlanBatori »

On a roll here...
So I read that this signal "took 1.5 billion years to reach here, and was here only for 200 milliseconds".

Interesting. So this whole Blackhole-blackhole chai-biscoot took only 200ms, or was this the spread-out FRONT of the shock wave? But I have a deeper pooch. So the BB (Big Bang) was supposed to have occurred 4 billion years ago? And led to a pretty widely dispersed distribution of matter? Then how long did it take, for a galaxy to form, and then concentrate into the start of a black hole, and then the black hole ate up ALL the matter around it (hypothesis on why no flash in other spectral regions)? What is the probability of TWO such clean blackholes developing inside the first 2.5 billion years from the BB, and of meeting in one place?

And after all this time of detecting gravitational waves from ALL OVER the Duniya, this is the FIRST such that they detected? Given the probability of this occurrence, why is it wrong to wonder about the probability of the explanation being true?
Most probable explanation right now: ISS flush. I bet they DO have two pakistans on the ISS that go "whoosh-gurgle-gurgle"
Last edited by UlanBatori on 17 Feb 2016 20:48, edited 1 time in total.
member_22733
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Re: Physics Thread.

Post by member_22733 »

UB ji..... are you being serious?

A black hole is a mass that is so dense that tge escape velocity at its event horizon is speed of light.

Now imagine two orbiting black holes of whatever mass, what will be their angular velocity when they merge? What will be their radial velocity in non relativistic terms when their event horizons combine?
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Re: Physics Thread.

Post by UlanBatori »

Yes, but will the whole interaction be over in a fraction of a second, given the sheer sizes? Mind-boggling. MAY be true, but most supernova events go on for several days or weeks, hain? Wouldn't such a BB-BB collision cause a degneration into chaos, and the expulsion of at least some matter (i.e., several galaxies' worth) out the side? Wouldn't that cause a truly cosmic glow for several days? Where is that?

Or.. did Time compress from years into milliseconds? What is the address of the No-Bill Pissiks Committee again, pls?
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Re: Physics Thread.

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So these Einsteins are claiming that they detected a gravitational wave BECAUSE TWO black holes collided - and then turning around and saying: AHA! This is the first real evidence of the EXISTENCE OF BLACK HOLES.
I think black hole existence was proved by lensing effect of light being affected by gravity of very large objects -- this was done a while back. The new development is being able to measure gravitational waves AFAICT.
As I saw it described (kindergarten/CNN level as befits me) some graduate student is jumping up and down claiming that he had modeled two black holes colliding, and this signal was EXACTLY like that. This is called SFP (Self-fulfilling prophecy).
Yes, I thought this is what they did, but that cannot be right, because if these gravity waves are travelling at the speed of light, then the first instant at which we can even know about the collision is when the waves reach earth, and unless these scientists were watching these two black holes about to collide (at a speed faster than light), this could not have been predicted....unless the calculation was to figure out how many milliseconds it would take gravitywave/light to reach one LIGO from the other (say X milliseconds), and then work backward to find signals that were exactly X milliseconds apart in the output of the two LIGOs and that were identical (six-sigma variance), and then they would work backwards to map an event to match the wave...though I unable to see how they managed to do that without some sort of triangulation. questions, questions....have to read that paper within the next 50-60 years.

Given the size of the universe (and just our own galaxy cluster) such events are likely to happen often in a *cosmic scale*, i.e., in the order of thousands to 100K years. We must have been extremely lucky to have this happen just after building LIGO. maybe god exists after all to bless us with this discovery. </joke>
Last edited by member_29325 on 17 Feb 2016 21:11, edited 1 time in total.
UlanBatori
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Re: Physics Thread.

Post by UlanBatori »

I am going to refer to that paper in my next NSF proposal from Ulan Bator. From what i have been told, "NSF does not accept et al in the References, you have to list out all authors". It will be very interesting to get the paper citation into BibTex, but then, hellooo!!! My References file will be 10 times as large as my Project Description file. Sure to get accepted!
(What the heck! Nothing else has worked! :(( )
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Re: Physics Thread.

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UlanBatori wrote:Yes, but will the whole interaction be over in a fraction of a second, given the sheer sizes? Mind-boggling. MAY be true, but most supernova events go on for several days or weeks, hain? Wouldn't such a BB-BB collision cause a degneration into chaos, and the expulsion of at least some matter (i.e., several galaxies' worth) out the side? Wouldn't that cause a truly cosmic glow for several days? Where is that?

Or.. did Time compress from years into milliseconds? What is the address of the No-Bill Pissiks Committee again, pls?
A supernova event is over in the order of a microsecond or so. The time it takes for the iron core of a star to collapse into a neutron star or a black hole is in the order of microseconds. It releases enough gamma rays to blow up the outer layer of the whole star into a nebula, which absorbs the gamma rays and transmits it into xrays, which then get absorbed by the outermost layer and get converted into lower frequency radiation. The primary process is just microseconds long, the secondary process takes days.
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Re: Physics Thread.

Post by UlanBatori »

I thought this is what they did, but that cannot be right, because..
Exactly. As Laurel said to Hardy: "NOW U r using MY brain!".
figure out how many milliseconds it would take gravitywave/light to reach one LIGO from the other
AFAIK, the places are only about 1000 km apart. So yes, they have precision of one part in 10^22 in measuring time, but.. (never mind, the RPGs are already coming, don't need to expand further).

Added: Thanks, Lokesh. So at least one mystery is resolved. But where is(are) the glowing nebula(e)?
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Re: Physics Thread.

Post by navneeet »

from PIB

Cabinet grants ‘in-principle’ approval to the LIGO-India mega science proposal
The Union Cabinet chaired by the Prime Minister Shri Narendra Modi has given its ‘in principle’ approval to the LIGO-India mega science proposal for research on gravitational waves. The proposal, known as LIGO-India project (Laser Interferometer Gravitational-wave Observatory in India) is piloted by Department of Atomic Energy and Department of Science and Technology (DST). The approval coincides with the historic detection of gravitational waves a few days ago that opened up of a new window on the universe to unravel some of its greatest mysteries.

The LIGO-India project will establish a state-of-the-art gravitational wave observatory in India in collaboration with the LIGO Laboratory in the U.S. run by Caltech and MIT.

The project will bring unprecedented opportunities for scientists and engineers to dig deeper into the realm of gravitational wave and take global leadership in this new astronomical frontier.

LIGO-India will also bring considerable opportunities in cutting edge technology for the Indian industry which will be engaged in the construction of eight kilometre long beam tube at ultra-high vacuum on a levelled terrain.

The project will motivate Indian students and young scientists to explore newer frontiers of knowledge, and will add further impetus to scientific research in the country.

***


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(Release ID :136479)
member_29325
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Re: Physics Thread.

Post by member_29325 »

So I guess no one is coming out and saying, we know from calculations that two black holes of size X & Y collided, except, we do not know where that happened, if it did. But all our mathematical calulations have been verified by 1004 people in the field, so this is as good as being a fact....still is only part of the picture, if anyone asks me, which they won't. In some ways, this is argument by authority, as in all the luminaries that back this,...which makes me a tad uncomfortable like all arguments from authority (which is usually what the religious people do). But maybe I am just being impatient and this will be proven eventually. I guess everyone is thrilled that they have a way to detect gravity waves, that no one can see and that is all around us at all times, like some sort of omnipresent thingie.
Last edited by member_29325 on 17 Feb 2016 21:16, edited 1 time in total.
UlanBatori
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Re: Physics Thread.

Post by UlanBatori »

Lokesh: From Wikipedia:
Type 1a SuperNova:

Within a few seconds, a substantial fraction of the matter in the white dwarf undergoes nuclear fusion, releasing enough energy (1–2×1044 J)[58] to unbind the star in a supernova explosion.[59] An outwardly expanding shock wave is generated, with matter reaching velocities on the order of 5,000–20,000 km/s, or roughly 3% of the speed of light. There is also a significant increase in luminosity, reaching an absolute magnitude of −19.3 (or 5 billion times brighter than the Sun), with little variation.[60]
That's what I would have thought: the inside of a White Dwarf is still a few tens of thousands of kilometers in diameter, hain? Take a while for fusion to go through all its steps.
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Re: Physics Thread.

Post by johneeG »

UB & Thiru saars,
something to interest you:
Here’s the first person to spot those gravitational waves

By Adrian ChoFeb. 11, 2016 , 11:30 AM

Today, physicists working with the Laser Interferometer Gravitational-Wave Observatory (LIGO) announced that after decades of effort they had detected gravitational waves—ripples in spacetime itself—set off by the explosive collision of two massive black holes. But which of the 1000 scientists who work on LIGO, a pair of gargantuan instruments in Livingston, Louisiana, and Hanford, Washington, was the first to see the long-awaited signal?

The honor fell to a soft-spoken postdoc who plays classical piano and has published two fantasy novels. His tale shows how elaborate plans devised to keep LIGO team members guessing whether a signal is real or a purposefully planted fake broke down, leaving one lucky physicist and, soon, the entire LIGO collaboration sitting on a thrilling secret.

Marco Drago wasn’t in Louisiana or Washington, or even the United States. Instead, the 33-year-old postdoc from Padua, Italy, was at his office at the Max Planck Institute for Gravitational Physics in Hanover, Germany, where members of the LIGO team work on data analysis. There, Drago oversees one of four data “pipelines,” automated computer systems that comb through the raw data coming out of the two detectors looking for potentially interesting signals. On 14 September 2015, while Drago was on the phone with a LIGO colleague in Italy, his pipeline sent him an email alert—of which he receives about one each day—telling him that both LIGO detectors had registered an “event” (a nonroutine reading) 3 minutes earlier, at 11:50:45 a.m. local time. It was a big one. “The signal-to-noise ratio was quite high—24 as opposed to [the more typical] 10,” he says.

In fact, the signal was so strong that Drago didn’t believe it was real—and with good reason. A gravitational wave from a distance source stretches space by an infinitesimal amount, and to detect that rhythmic stretching LIGO employs two gigantic optical devices called interferometers, which essentially act as gigantic rulers. To test the incredibly complicated devices, LIGO physicists have developed mechanical systems to give them a shake and “inject” a fake signal. The signal Drago saw was so perfect it seemed too good to be true, he says. “No one was expecting something so huge, so I was assuming that it was an injection.”

Here’s where the story departs from the previously prepared script. Injections can be done in two ways: out in the open when researchers are tuning up the machines and secretly when they are taking data. Those latter “blind injections” are meant to keep researchers on their toes. Only four LIGO leaders know when such injections are made, and that information is supposed to be revealed only after a potential signal has been thoroughly scrutinized and written up for publication. That’s how things unfolded in 2010, when LIGO researchers learned at the last minute that a possible signal was in fact a blind injection. So if all had gone as anticipated, Drago might have simply noted the alert and carried on as usual, assuming the truth would come out in the end.

This time, however, the tale of the detection took a different turn.
That’s because on 14 September 2015, LIGO physicists were still tuning up their machines after a 5-year, $205 million upgrade. Researchers had intended to start their first data run with the new rigs on that day, but several systems—including the injection system—were not ready to go, says David Reitze, a physicist and executive director of LIGO at the California Institute of Technology in Pasadena. So instead, LIGO leaders opted to continue a shakedown test known as an engineering run for another week. Thus, when the signal came, Drago knew that the injection system was not supposed to be working. He immediately set out to verify that and ended up alerting the entire collaboration to the signal.

Drago’s first step was to ask his fellow postdoc in Hanover, Andrew Lundgren, whether anybody in the collaboration had performed an open injection that hadn’t been properly logged. Lundgren could find no evidence of such an event. Next, Drago and Lundgren called the control rooms in Livingston, where it was just after 5:00 a.m., and Hanford, where it was just after 2:00 a.m., to see whether anybody had monkeyed with the detectors or noticed any peculiar behavior. He reached only one of the facilities—“Livingston, I think,” he says—but was told all was normal.

I’m going to call up my family and say, ‘You know, I was the first to see this.’
Marco Drago

Finally, about an hour after receiving the alert, Drago sent a broadcast email to the entire LIGO collaboration. “I asked if anybody was aware of anything that could be an injection,” Drago says. Nobody said yes. But that email alerted everyone that the instruments had seen a whopping big signal that, at least on the face of it, could not be a blind injection—exactly what they were not supposed to know. A few days later, collaboration leaders sent around a notice saying that the signal probably was not an injection. Within LIGO, the cat was out of the bag.

Once researchers realized they had a potential discovery on their hands, they ended the engineering run and switched to data-taking mode, in which the devices are supposed to operate without any adjustments. Officially, that 18 September 2015 change marked the beginning of revamped LIGO’s search for sources. But actually, scientists were trying primarily to collect enough data to validate the already observed signal, says Gabriela González, a physicist at Louisiana State University, Baton Rouge, and spokesperson for the LIGO scientific collaboration. To measure the background noise and estimate the statistical significance of the signal, researchers needed 5 days’ worth of data from both detectors running simultaneously. By 5 October 2015, they had it.

The team spent much longer than that making sure they had not somehow been fooled by a signal that had been injected either inadvertently or even as part of some elaborate prank. But such scenarios proved untenable, Reitze says. “You’d need a whole team of insiders with a wide variety of technical abilities,” he says.

As the analysis continued and the results were written up, LIGO leaders struggled to keep a lid on their news. “It was a challenge,” González says, “but from the beginning we explained [to the collaboration] the need for confidentiality” while the analysis was ongoing. “You cannot make an announcement and then say, ‘Oops! Sorry, we were wrong!’” Still, word of the discovery slowly leaked out, especially through social media and on theorists’ blogs. González says she found it stressful addressing—or ignoring—inquiries, especially from journalists. “It’s been a lot of pressure, answering to people, not answering to people,” she says. “But we never lied.”

But now that the blockbuster news is out, LIGO researchers are free to talk. And Drago says he’s glad about that: “I’m going to call up my family and say, ‘You know, I was the first to see this.’”
Posted in:

Scientific Community Space Gravitational waves

DOI: 10.1126/science.aaf4039
Adrian Cho
Link
"Blind Injection" Stress-Tests LIGO and VIRGO's Search for Gravitational Waves

The LIGO Scientific Collaboration and the Virgo Collaboration completed an end-to-end system test of their detection capabilities at their recent joint collaboration meeting in Arcadia, CA. Analysis of data from LIGO and Virgo's most recent observation run revealed evidence of the elusive signal from a neutron star spiraling into a black hole. The collaboration knew that the "detection" could be a "blind injection" -- a fake signal added to the data without telling the analysts, to test the detector and analysis. Nonetheless, the collaboration proceeded under the assumption that the signal was real, and wrote and approved a scientific paper reporting the ground-breaking discovery. A few moments later, according to plan, it was revealed that the signal was indeed a blind injection.

While the scientists were disappointed that the discovery was not real, the success of the analysis was a compelling demonstration of the collaboration's readiness to detect gravitational waves.
LIGO and Virgo scientists are looking forward to observations with the advanced detectors which are expected to contain many real signals from the distant reaches of the universe.
Is it real?

In the subsequent days and weeks, numerous teams of scientists tried to get definitive answers to many questions. The event was seen strongly in the two LIGO detectors, less strongly in the Virgo detector, and nothing was seen in the less sensitive GEO detector. Could the event be explained as an accidental coincidence of noise fluctuations? The initial estimate was that the chance of the event being due to noise in the detectors was "much less than 1%", but much more work was required to say how much; after careful analysis, the teams agreed that such a noise coincidence might happen once in 7,000 years.

Could the detectors have exhibited some never-before-seen instrumental effect just then, maybe one that could somehow be correlated between sites that are separated by thousands of kilometers? Despite many investigations and much thought, no plausible scenario for this could be found (except for a blind injection).

After studying all of the evidence, the hundreds of scientists in the collaborations convinced themselves and each other that this was not an instrumental artifact.
Documenting the "Evidence":

The scientists gathered all this information together in a paper entitled "Evidence for the Direct Detection of Gravitational Waves from a Black Hole Binary Coalescence". (Coalescence refers to the inspiral of the two stars, their merger into a single perturbed black hole, and the "ringdown" into a final quiet black hole, all through the emission of gravitational waves). A second paper described the parameter estimation procedures and results. A third summarized the search for binary coalescence and the overall results (only one event was observed above the background noise).

Material was prepared for the open release of data relevant to this event, and a whole suite of resources for education and public outreach was assembled. The event was renamed "GW100916", for the year, month and date that it was recorded.
Link



It seems they can fake these signals(why am I not surprised). The fakes can be both openly done and secrets done. Secret fakes are called 'blind injection'. And only 4 people know about it. It seems that last time, in 2010, all the analysts in that place were fooled and they wrote all the papers and publications thinking that these signals were real. And after that it was revealed to them that it was fake i.e. blind injection. Now, they say that this is real. The interesting part is that a normal analyst at LIGO apparently has no clue if a signal is fake or if its 'real'. He just assumes it to be true even though he knows that it can be faked both openly and secretly. And the secret fakes are only known to 4 people who will decide if its real or fake. If those 4 people say its real, then its real.

Now, question in my mind is: if those analysts working at LIGO have no clue if these are real or fake, then how are others supposed to verify if these are real or fake?
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Re: Physics Thread.

Post by member_22733 »

Batori saheb,

That's a type 1a supernova. It's a slightly different process than the one I described. Its a dead star eating up a live star and going supernova.
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Re: Physics Thread.

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I doubt any physicist would have knowingly faked results that could tarnish not just the LIGO project but the name of science itself among the lay public, where science has its fair share of enemies among the religious fundamentalists and the flat earthers, but humans are "complicated" (i.e., they can do pretty crazy things for pretty stupid reasons, so who knows...not under the purview of science).

But the setup has multiple people at the top who had access to fake signals and they have means avoid faking signals without anyone's knowledge but only after signing into a "log book", which is probably some encrypted computer login application. So I think we can be reasonably sure this was not faked by those who had the authority and the means to do so...but then all of this is more of a hope than a certainty.
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Re: Physics Thread.

Post by johneeG »

The bigger point is that there is no independent way of verifying if this is real or fake. There is only one LIGO right now. Even in that institute only 4 people know about secret fakes(called blind injections). Last time it was faked according to their own admission and all of these same analysts were fooled into believing that it was real. And they had written papers and publications until finally it was revealed to them that it was fake. BTW, all this is directly on their official website. So, this is not some 'conspiracy theory'.

Anyway, its a huge money guzzler. This whole thing costs about 500 million to 1 billion. And most of it seems to funded by US tax payer money.

- huge money involved -> tax payer money.
- known fakes(blind injections) in the past.
- not verifiable independently.
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Re: Physics Thread.

Post by Vayutuvan »

sanjaykumar wrote:Oh yes Fred Hoyle wrote The Black Cloud, haven't read it but he argued for panspermia with Wickersinghe.
Thanks. AFAIK, Poul Anderson writes more fantasy than hard SF. I have three Fred Hoyle hardcover SF books. I have to see if one of them is this. I don't remember reading this book.
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I am sure the physicists know as well as anyone else, that they cannot do a pons-fleischmann (cold fusion) on this just because no one else will be building a LIGO. Doing so will damage the very foundations of the credibility of science, and bring back pseudoscience with a vengeance. Sure hope that is not the case...we would all be set back by a couple of centuries if that happens....or maybe we are already a few centuries behind mentally as a race of humans.
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Re: Physics Thread.

Post by Vayutuvan »

johneeG: This is just ridiculous. What exactly would the Physics community gain by doctoring data? You realize that you are leveling a very serious charge against the whole STEM community - not just Physics people only. That kind of skepticism is not in the domain sciences, not even in the domain of analytic philosophy or otherwise.
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vayu tuvan wrote:johneeG: This is just ridiculous. What exactly would the Physics community gain by doctoring data? You realize that you are leveling a very serious charge against the whole STEM community - not just Physics people only. That kind of skepticism is not in the domain sciences, not even in the domain of analytic philosophy or otherwise.
No, I didn't level any allegation. I just stated the facts related to this issue. I deliberately avoided making any conclusion. If the facts of the case make it suspicious to you, thats your opinions. Or you can choose to keep your faith. Either way, its your faith and your choice. Don't blame me.
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Post by member_29325 »

At some level, faith on the honesty of the people involved is central to believing all the results from them, at this time, mostly because there is only one LIGO and one group in charge of it.

We can only know for sure when more such events are detected and mapped to actual events in the universe, or another LIGO is built somewhere with all the copious funds governments seem to have today, in order to validate these results and beat down all skeptics.
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Post by TSJones »

....all the same, even though some skepticism is warranted until verified in some manner, I'm not bettin' against these guys and gals.
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Re: Physics Thread.

Post by Amber G. »

UlanBatori wrote:Now the other obvious question which will be lynched as "con-descending", "silly", "disgraceful" etc: . :(( :(( .
Ooooohhh..claiming victimhood like JNU students being treated harshly.. How sad :(
..blah blah ..So these Einsteins ..blah blah .. BECAUSE TWO black holes collided - blah blah ...Isn't this circular logic? ..blah blah ....What if .. pulling the flush on the ISS? .blah blah .... Gurgle-gurgle, whoosh-gurgle-gurgle, blah blah .. Duchy of Fenwich .. blah blah ..a gold-plated pakistan... blah blah...
No (No "this" is not circular logic).. but don't let me stop.. please carry on with all your theories..As some very :mrgreen: wiseman in brf :mrgreen: said <click for link>
Sometimes it is better to keep one's mouth shut and let everyone wonder whether one is stupid, than to open it and remove all doubt
Now when such eminent personalities like JohneeG are joining, I am going to sit back and enjoy all posts about fake science, (except bhaskara wheels of course).. as some one said.. this is more entertaining than a circus.. hey! now why go through non-mentionable forums while one find all the entertainment right here on brf. :-o
Carry on! :mrgreen:
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TSJones wrote: ....all the same, even though some skepticism is warranted until verified in some manner, I'm not bettin' against these guys and gals.
Agree, skepticism is warranted in pretty much all topics related to science, though level of skepticism can be toned down depending on other factors like the credibility and number of people involved...but still not a certainty. In this case, the fact that false positive was not generated can still be questioned, which would imply that the people involved are not credible, which is raised by UB's skeptical line of questioning. Chances are pretty good that these results will get validated down the line by other LIGOs and eLISAs, hopefully within our lifetimes...assuming govts don't stop funding such endeavors around the globe...expensive tools these are.
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Post by johneeG »

Amber G. wrote:
Now when such eminent personalities like JohneeG are joining, I am going to sit back and enjoy all posts about fake science, (except bhaskara wheels of course).. as some one said.. this is more entertaining than a circus.. hey! now why go through non-mentionable forums while one find all the entertainment right here on brf. :-o
Carry on! :mrgreen:
AmberG,
the funny part is that you seem to be highly enthusiastic about discussing Bhaskara wheel whenever I mention any other scientific topic. Yet, when I was actually talking about Bhaskara wheels, you were more interested in talking about some other maths problems. Whats more, you yourself admitted that you were lying about the maths problem also. It seems to me that you have nothing say on the topic itself and frequently deflect from the topic at hand.

Oh btw, concerns about it being fake were first expressed by those same analysts themselves. And I actually didn't call this fake. I said it has a history of fakes by their own admission(which they call blind injection) and that its not independently verifiable. They are facts. If you don't like them, its your problem.
UlanBatori
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Re: Physics Thread.

Post by UlanBatori »

Gets better and better.

So now it is down to "leveling serious charges.." :eek:
Let us do what the famous Dilip D'Souza called A Thought Experiment. Presumes the ability to think, but let's not go there 4 now.

Suppose u r Abdul bin Kabul, graduate student from Gujranwala, Pakistan. U got admitted into this LIGO thing which you thought was LEGO, and they assigned you the job of sitting watch on the LIGO system that was down. It's 2AM. U r busily watching Debbie Dus Dallas on the 60-inch ultra HD LIGO monitor with ur Bose headphones on. Suddenly you see the cursor on your other computer monitor begin to move. Like someone has just logged on.

U wonder who, so U quickly shut down D^3 and creep out into the hallway - there is a small light on in one of the cubicles of the Top Pissikists. Despite ur bravery, having skiied downhill leaving ur Northern Flight Infantry behind in 1999, u begin to shake - may be a mugger?

U peek very gingerly. Oh! It's Dr. ******! No problem, she's so high up in the hierarchy, she must have access to even the budgets. Probably getting that budget request together that she was talking about the other day, that had to go all the way to the POTUS for approval. She goes to Langley, VA every month, they say. Heck, u ain't gonna mess with HER!! U r terrified of her as it is, and she controls the budget!

When "WHAMMO!" U forgot that ur wireless headphones were on. When u come to, ur r on the floor, and it's 3AM.

U look on the computers. Looks like there was a power outage. Oops! U forgot to set the backup working. U check: All data and commands for past 3 hours are gone. So is the light in Dr. *****'s cubicle.

What do you do next day? What do u do when the "news" is released? Do you "level serious charges?" Do u invite ppl to come and do data recovery on the disks, which will bring up D^3? :shock:

The point to note is: there WAS some way to "inject" a spurious signal into ****ALL** the LIGO systems simultaneously/ with 0.4 millisecond delay. You did NOT have to go to space and set off a black-hole collision to generate that data - there was an alternative path into the data stream.

Sorry, I am not buying stock in this. May not do as well as my oil, natural gas and gold stocks are doing. :((
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Re: Physics Thread.

Post by A_Gupta »

ThiruV wrote:Ok, so looking at all the nice videos of two stars circling each other and emitting gravity waves, it seems odd that they got this one odd blip, and attributed it to a cataclysmic two-star event. If these waves are continuously generated when two stars spiral into each other, shouldn't the LIGO people be able to detect pulses from the stars, rather than one short blip that everyone is celebrating? Does this mean LIGO is going to periodically announce results, or is the circus over for now? Can't they detect some other binary system that will be giving out similar gravity waves?
Yes.
Via: http://www.forbes.com/sites/startswitha ... 2cab1a40da

Link to image (embedded image is too big)
http://blogs-images.forbes.com/startswi ... 00x900.jpg
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Re: Physics Thread.

Post by sanjaykumar »

Okay, instead of mere reportage, reddit has some interesting discussion. Looks like I was on the right track.


Perhaps most of all, the fact that this opens up an entirely new method of astronomy, one that ultimately will allow us to probe the most extreme densities and energies that exist in our Universe! Finally, this result gives us some confidence that we’ll eventually be successful in measuring the gravitational waves of the Big Bang, and learning about the fundamental origins of the universe.


And:

Shouldn't the Interferometer pick up gravitational waves from a lot of places at the same time?


Good question. The answer is that LIGO can only detect extremely powerful events, like black holes colliding, and those events don't happen very often (even given the size of the universe). Moreover, the events are very short-lived, so that also prevents them from overlapping. (But no mention of the age of the universe).
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Re: Physics Thread.

Post by A_Gupta »

Amber G. wrote:
I remember the event very well so let me tell a personal story which may give some perspective..
When the discovery was "announced", not through a paper, but via a press conference by university's (Utah U) big shots, I tired to read the original paper, but it was not out.


The Caltech nuclear physicists were asking immediately, where are the neutrons, where are the neutrons? -- which fusion ought to have produced.
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Re: Physics Thread.

Post by A_Gupta »

UlanBatori wrote:They must have paid big $$ to generate a sound track so purely evil that I cannot go to sleep after listening to it. :eek:
So this is the thing I cannot comprehend, among many other things. Even at speed of light, are the Black Holes so small in extent that an "interaction" is over inside a "blip"? Should it not have taken a lot longer for each interaction? OK, half a second is 90,000 miles...
How big is the diameter of the event horizon of a Black Hole?
The interaction was going on for quite a while as the two black holes spiraled into each other. Unfortunately, the range of frequency and amplitude that LIGO can detect limits it to the final merger.

In this case, the event horizons of the black holes were of the order of 100 km.

Anyway, if you want to disbelieve the result, one of its foundations is rather formidable numerical solutions of non-linear partial differential equations of general relativity. A relatively recent overview of so-called Numerical Relativity is here: http://arxiv.org/abs/1405.4840
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Re: Physics Thread.

Post by A_Gupta »

FYI, the existence of gravitational waves is not really in doubt.
1993 Nobel Prize in Physics:
http://www.nobelprize.org/nobel_prizes/ ... dread.html

PS: more on the Hulse-Taylor binary pulsar:
https://en.wikipedia.org/wiki/PSR_B1913%2B16

and

http://arxiv.org/abs/1011.0718v1
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Re: Physics Thread.

Post by sanjaykumar »

Interestingly, it was an Indian who seems to have first proposed, in 1970:

Scattering of Gravitational Radiation by a Schwarzschild Black-hole

http://www.nature.com/nature/journal/v2 ... 936a0.html
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Re: Physics Thread.

Post by A_Gupta »

A high-level view of LIGO technology:
https://www.ligo.caltech.edu/page/ligos-ifo
TSJones
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Re: Physics Thread.

Post by TSJones »

A_Gupta wrote:FYI, the existence of gravitational waves is not really in doubt.
1993 Nobel Prize in Physics:
http://www.nobelprize.org/nobel_prizes/ ... dread.html

PS: more on the Hulse-Taylor binary pulsar:
https://en.wikipedia.org/wiki/PSR_B1913%2B16

and

http://arxiv.org/abs/1011.0718v1
the Mongol is not saying there in no gravitational waves. Mongol knows better than to go against Einstein guru dev. he is highly skeptical that:

a. the equipment can detect such an event and of the grad students who do the actual labor who could be loosey goosey. evidently Mongol has experience with students somewhere along the line.

and

b. currently there is no way to independently verify the results, no comparative observations.

so, Mongol is stirring the pot.
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Re: Physics Thread.

Post by UlanBatori »

Hey, I have the GREATEST respect for the integrity of hard-working, underpaid, underappreciated graduate students. Used 2 b one myself at one time.
But as for uber-ambitious faculty types at universities... let us just say that they give serpents and idiots a bad name. ABSOLUTELY NOTHING is beneath them. And **THERE**, sadly, I have too much hard experience and no doubts at all.

The signs are bad if you have been burned enough to know what to look for. "Signal looked EXACTLY LIKE what we had expected". A bit too pat, that, hain? Do you believe that YOUR model of a black hole, let alone TWO black holes, is really that accurate? You know THAT much about physics at its extremes?

So AmberG, sorry, but I mean what I said about certain entities having learned nothing from the cold fusion case.
I say, look carefully at the finances of the LIGO project, and projections for further funding b4 you go too far awarding Nobel Prizes etc etc. I have no doubt that gravity waves exist, or that there is something to Einstein's (erroneous of course) calculations.

Personally, I believe in the Quantum Teleportation and Action at A Distance religion, so I have to diss all this "speed of light" stuff. :mrgreen:
Last edited by UlanBatori on 18 Feb 2016 05:38, edited 1 time in total.
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Re: Physics Thread.

Post by A_Gupta »

Well, we will know more reasonably soon. A Japanese and an Italian instance of LIGO will come on line within the next few years.

Hey, the initial confirmation of Einstein's theory - the deflection of light by the sun, measured by Eddington, was a one-of, and wasn't repeated for quite a while.
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Re: Physics Thread.

Post by A_Gupta »

Ulan Batori - intelligent skepticism is good, it is an essential and unalienable part of science.
Do you believe that YOUR model of a black hole, let alone TWO black holes, is really that accurate? You know THAT much about physics at its extremes?
Actually, yes, outside of the event horizon, black holes are actually very simple objects. E.g, take a look at the Hulse+Taylor pulsar. What happens depends on tidal effects of the two neutron stars on each other, for instance, and computing that requires an equation of state for neutronium - which introduces some uncertainties. No such problems with black holes.
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Re: Physics Thread.

Post by UlanBatori »

I look at black holes as being similar to supersonic flow. The existing models are simple because so little is really known. The experimental points (of which there are very few) "sort-of" match the curves from the simple transform like 1/SQRT(M^2-1) or 1/SQRT(1-M^2) {which is similar to the Lorentz Xform, right?) , but in reality, there HAVE to be differences: these transforms come from very linearized theories which are themselves approximations. In this case the two black holes were circling / spiralling at at 0.6 times the speed of light, which means a huge increase in their already humongous mass per relativity? (Lorentz-Mie transform?) In that regime, physics really behaves so simply? So the real test will come when the squiggles in the Whoosh-gurgle-gurgle are explained by "Aha!" moments, unanticipated in Einstein's derivations but predicted by the more exact, grander theories if any. If THOSE happen, I'll start believing.

What is inside BH is probably many many GALAXIES. Meaning BILLIONS of solar systems!!! Does all the mass get uniformly scrunched down to some incredibly homogeneous mishmash, borderline between mass and energy? How MUCH mass? Relativistically increased to near infinity because of the high speeds of rotation? I am sure my utter ignorance shows, but this is all just so far over my head. The merger of two blackholes is far more complex. So these had the same sense of rotation, to roll up like vortices in a shear layer? Do they behave EXACTLY like vortices in a shear layer? At what point does the equivalent of viscosity take over? What does a supersonic vortex look like, anyway? No supersonic tornadoes that I know if, but the Concorde did have tip vortices..

Let's see.. hopefully the Japanese gizmo will validate future events, but overall, the revelation of those "artificial test signals" only served to immensely reduce my confidence level. It's like arguing that many of the currency notes that you get at the bank are bogus, but this million-rupee note is absolutely 400% genuine because everyone denies that it is also counterfeit. Hardly inspires confidence.
Last edited by UlanBatori on 18 Feb 2016 06:08, edited 1 time in total.
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Re: Physics Thread.

Post by Yayavar »

What was the reasoning behind 'artificial signals'? the above write-up says to keep scientists 'on their toes'. That seems odd. Is it a common practice to insert false-positives to see if the fellow scientists are paying attention?

The above question does not mean I doubt the results - dont have the expertise. Just curious about what seems to me an odd way to keep colleagues alert especially as the 'false' signal was revealed only after papers had been written up for publication.
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Re: Physics Thread.

Post by UlanBatori »

Usually it would be to check for nonlinearities in the sensors. Like, the signal is really a sine wave, but does the sensor say sawtooth? It must be to get the "transfer function" between reality and the sensor outputs. They have to put in their best guess of "expected signal". Now here they say the amplitude was far ABOVE the expected levels, yet they seem to have got pretty clean signals. Either the sensor design was very conservative (much more sensitive than they had believed) or ... something else. Perhaps many more such events will be detected, but I wonder why none has. Note that there are supernova events like once or twice a year, probably MUCH closer to earth than 1.5 Billion light years - so they should be detectable though they are not nearly as cataclysmic as a BH collision. Just rambling, I have absolutely no idea what I am rambling about.
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