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Physicists Detect Gravitational Waves, Proving Einstein Right

nytimes.com

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Re: Physicists Detect Gravitational Waves, Proving Einstein Right

#291

Post by pbhjpbhj »

21 wrote: post #75
tomp wrote: post #23

Earlier quoted context omitted.

If this events are so rare (that we don't even know how rare they are), how is it possible that they achieved the required certainty (5 sigma)? I guess you could count one looong wave as a series of one-time events/measurements, but it could as well be a loooong interference.

This is about detection. To put it another way, you need a single black swan to prove that black swans exists (to whatever sigma).

Isn't the point though that the gravitational wave observatories are looking specifically for "black swans" rather than just observing swans generally. So when a swan with a lower reflectivity is observed then it now fits the "black swan" profile. Could be just a swan covered in soot; you need more data to show that this swan is always black or that the lower reflectivity wasn't caused by a measuring anomaly, etc.

I may have pushed the analogy too far!

Re: Physicists Detect Gravitational Waves, Proving Einstein Right

#292

Post by sandworm101 »

pistle wrote: post #243
sandworm101 wrote: post #105

Earlier quoted context omitted.

>> that shortly after the detector came online we just happened to observe the exact moment a billion years ago that two black holes collided? Counterintuitive, but yes. Because it happened billions of years ago, it happened a long long way away. The sphere of objects billions of years away/ago is far larger than those closer to us. So such a detector should be detecting exponentially more very old objects than new o…

If one event happens 1B years ago 1B light years away and another event happens at .5B years ago .5B light years away... how would we know there are two events?

The wave may contain the information necessary to describe the event that created it. If you know, perhaps by frequency, that the wave came from two super-massive black holes spinning around each other at a given rate, then you know how massive each hole should be. From that you can predict the energy of the wave. And from that you know how far away the event must be for the energy behind the wave to have spread so thin. It's basically the same process as calculating distance via cepheid variable stars.

Re: Physicists Detect Gravitational Waves, Proving Einstein Right

#293

Post by valarauca1 »

SaberTail wrote: post #212
sandworm101 wrote: post #181

Earlier quoted context omitted.

If gravitons have mass, then the universe is too strange to exist. Gravity is an interaction that defines the presence of matter (see dark matter). For the object that transmits that force between masses to itself have mass ... how can a black hole then project gravity? Imho whatever is carrying gravity between masses cannot itself have a mass.

What do you think of the strong nuclear force? Gluons are the force carriers between color-charged particles. And gluons themselves have a color charge. So gluons transmit force between each other. Does that mean the universe is already too strange to exist? By the way, this is why the strong nuclear force has such a short range. Gravity has infinite range as far as we can tell, so that makes it unlikely that the gra…

Photon's and gravitons have to be masses because Gravity and Light and interact with matter at finite distances.

If your 1 billion light years from earth, you are still effected by the Earth's gravity (well its likely smaller then experimental error but never mind that it still exist).

So there needs to be gravitons from Earth flooding the entire sphere of space for 1 billion light years around the Earth. All these gravitons have mass, and are emitting their own gravitons. Which all have mass and energy! Where is this mass and energy coming from? It really can't, it violates the laws of thermodynamics. But so does Dark Energy so who knows.

Re: Physicists Detect Gravitational Waves, Proving Einstein Right

#294

Post by rdancer »

yaks_hairbrush wrote: post #261
rdancer wrote: post #172

Earlier quoted context omitted.

But gravitational waves are a phenomenon without equivalent. Nothing like that had been observed before. (Am I wrong?) W̶h̶e̶n̶ ̶t̶h̶e̶ ̶L̶H̶C̶ ̶d̶e̶t̶e̶c̶t̶e̶d̶ ̶H̶i̶g̶g̶s̶,̶ ̶f̶o̶r̶ ̶e̶x̶a̶m̶p̶l̶e̶,̶ ̶t̶h̶e̶y̶ ̶h̶a̶d̶ ̶b̶e̶e̶n̶ ̶f̶i̶n̶d̶i̶n̶g̶ ̶p̶a̶r̶t̶i̶c̶l̶e̶s̶ ̶f̶o̶r̶ ̶m̶i̶l̶l̶i̶o̶n̶s̶ ̶o̶f̶ ̶m̶a̶n̶-̶y̶e̶a̶r̶s̶,̶ ̶a̶n̶d̶ ̶ s̶o̶ ̶i̶t̶ ̶s̶t̶a̶n̶d̶s̶ ̶ t̶o̶ ̶r̶e̶a̶s̶o̶n̶ ̶t̶h̶a̶t̶ ̶t̶h̶e̶y̶ ̶o̶n̶l̶y̶ ̶n̶e̶e̶d̶e̶d̶…

This comment is making the page formatting gross. Those special characters with the strike-throughs make the entire page over-wide, thus requiring horizontal scrolling to read comments.

The browser layout engine should break on the spaces (Chrome does). They are just normal spaces, the combining character should have no effect. You have a bug somewhere.

Also, I cannot edit nor delete it now, so tough luck!

        " "    SPACE	                        Basic Latin
               0x0020
        "̶"     COMBINING LONG STROKE OVERLAY	Combining Diacritical Marks
               0x0336

Re: Physicists Detect Gravitational Waves, Proving Einstein Right

#295

Post by nerfhammer »

jballanc wrote: post #259
gradi3nt wrote: post #221

Earlier quoted context omitted.

So that's wayyyyyyy outside our galaxy? Any idea how many galaxies fit into a 1 billion ly sphere around the milky way? I'm guessing a shit ton, which makes the detection of a bh merger seem more realistic to me. That's some serious range!

It was mentioned during the press conference today that gravitational waves are not affected by interstellar/intergalactic dust the same way light is. In theory, once our detectors are good enough we should be able to use gravitational wave astronomy to peer all the way back to the big bang!

So, we'll finally be able to hear what god said at the start of the universe?

Re: Physicists Detect Gravitational Waves, Proving Einstein Right

#296

Post by valarauca1 »

tizzdogg wrote: post #177
lutorm wrote: post #149

Earlier quoted context omitted.

https://www.black-holes.org/gw150914 has some visualization of the event. There is the initial inspiral, and then there is a ringing afterwards. However, the entire event is over in a fraction of a second, which may be a "blip" to humans, but is very long when things happen at the speed of light.

Thanks, that's helpful. It's hard to get my head around the idea that an event so massive can be over so "quickly", without any residual longer-lasting effects.

>without any residual longer-lasting effects

A massive ripple in the very fabric of reality?

Re: Physicists Detect Gravitational Waves, Proving Einstein Right

#297

Post by jug »

ScottBurson wrote: post #176

This made me wonder how far we are from being able to create and detect gravitons. The Wikipedia page on gravitons [0] addresses this question: Unambiguous detection of individual gravitons, though not prohibited by any fundamental law, is impossible with any physically reasonable detector. The reason is the extremely low cross section for the interaction of gravitons with matter. For example, a detector with the mas…

Related to this... According to Kip Thorne, this recent discovery alone places an upper bound of maximum mass for a graviton, if it exists and has mass, at no more than 10^-55 grams. Since otherwise the observed waves would have been distorted. It's cool that we are already seeing conclusions drawn from this observation. This single obsrrvation. https://starguyspeaks.wordpress.com/2016/02/11/on-gravitatio...

Re: Physicists Detect Gravitational Waves, Proving Einstein Right

#298

Post by bobinator606 »

amai wrote: post #178

On November 25, 1915 (at the time of WWI) Einstein presented the actual Einstein field equations to the Prussian Academy of Sciences. Almost exactly 100 years later on September 14, 2015 LIGO observed the first gravitational-wave signal. Is that a coincidence?

No. Spooky Action at a Distance.

Re: Physicists Detect Gravitational Waves, Proving Einstein Right

#299

Post by TheOtherHobbes »

swamp40 wrote: post #164
boardwaalk wrote: post #138

If they build a third observatory, can they triangulate where in the universe the events are occurring?

Yes. There is a third one (VIRGO) near Pisa, Tuscany - a French/Italian collaboration. Unfortunately it was not online for this event. There is also one being built in Tokyo, and another being planned in India.

There's also a planned project called eLISA which will use satellites to increase accuracy and sensitivity.

https://en.wikipedia.org/wiki/Evolved_Laser_Interferometer_S...

Re: Physicists Detect Gravitational Waves, Proving Einstein Right

#300

Post by bobinator606 »

cft wrote: post #85
QuadrupleA wrote: post #82

One thing I don't quite understand - how can the "chirp" from LIGO be unambiguously categorized as extraterrestrial in origin? The waveform shown onscreen in the NYtimes video looks like an extremely noisy signal - not sure if that's the actual sampled data or just an artistic rendition. Couldn't there be a variety of physical disturbances that explain a sine-tone sweep like that, given how sensitive the instrument i…

There are two independent sites, 2000 miles apart. Additionally, each site has two perpendicular experiments: one shows contraction when the perpendicular one shows expansion. Orientations at both sites are aligned I presume.

And there is a third which was offline at the time, and 2 more being worked on. This is no the last experiment.
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