Atheistforums.com

Science Section => Science General Discussion => Physics & Cosmology => Topic started by: josephpalazzo on January 12, 2016, 12:13:33 PM

Title: Gravitational waves: rumors of their discovery
Post by: josephpalazzo on January 12, 2016, 12:13:33 PM
http://www.theguardian.com/science/2016/jan/12/gravitation-waves-signal-rumoured-science?CMP=twt_gu


This would be a landmark if true. Not only a great triumph for Einstein who predicted them, but also with gr. waves, one would be able to "see" farther into the past, very near to the beginning of the Big Bang. One of last year's controversy was the result of the BICEP2, which had claimed proof of Inflation theory, as proposed by Guth/Linde, but the results were attributed to galactic dust. Now, Gr. waves could be used to confirm or not Inflation theory. 
Title: Re: Gravitational waves: rumors of their discovery
Post by: josephpalazzo on January 12, 2016, 12:54:53 PM
Here's a good video by PBS on gravitational waves and LIGO.

https://www.youtube.com/watch?v=1Tstyqz2g7o

Title: Re: Gravitational waves: rumors of their discovery
Post by: doorknob on January 12, 2016, 03:19:45 PM
awesome!
Title: Re: Gravitational waves: rumors of their discovery
Post by: Unbeliever on January 12, 2016, 05:55:24 PM
I didn't see in the article whether the GWs that may have been observed were of the cosmological variety. If they were, they could help to confirm inflation, otherwise they're still useful and interesting, but have no bearing on cosmology.

Gravity waves are like e.t. aliens - everyone believes they exist, but no one's ever seen them.
Title: Re: Gravitational waves: rumors of their discovery
Post by: Baruch on January 12, 2016, 06:07:04 PM
Quote from: Unbeliever on January 12, 2016, 05:55:24 PM
I didn't see in the article whether the GWs that may have been observed were of the cosmological variety. If they were, they could help to confirm inflation, otherwise they're still useful and interesting, but have no bearing on cosmology.

Gravity waves are like e.t. aliens - everyone believes they exist, but no one's ever seen them.

It is difficult to devise a good general purpose antenna.  But the change of orbit of binary pulsars ... tends to confirm that they are out there.
Title: Re: Gravitational waves: rumors of their discovery
Post by: Unbeliever on January 12, 2016, 06:11:30 PM
Much like dark matter. It's almost certainly there, given recent measurements, but just what it is has yet to be figured out.
Title: Re: Gravitational waves: rumors of their discovery
Post by: josephpalazzo on February 09, 2016, 04:44:06 PM
This Thursday: Scientists will provide update on the search for gravitational waves. Media Advisory says:

"Journalists are invited to join the National Science Foundation as it brings together the scientists from Caltech, MIT and the LIGO Scientific Collaboration (LSC) this Thursday at 10:30 a.m. at the National Press Club for a status report on the effort to detect gravitational waves - or ripples in the fabric of spacetime - using the Laser Interferometer Gravitational-wave Observatory (LIGO)."

If it is confirmed, this will be huge - something you can tell your grand-children...
Title: Re: Gravitational waves: rumors of their discovery
Post by: SGOS on February 09, 2016, 07:22:53 PM
Well, why not?  I guess.
Title: Re: Gravitational waves: rumors of their discovery
Post by: aitm on February 09, 2016, 07:58:30 PM
I don't suppose there is a coloring book that describes it eh?  Damn.
Title: Re: Gravitational waves: rumors of their discovery
Post by: stromboli on February 09, 2016, 08:26:00 PM
Quote from: aitm on February 09, 2016, 07:58:30 PM
I don't suppose there is a coloring book that describes it eh?  Damn.

(https://s-media-cache-ak0.pinimg.com/564x/ea/97/eb/ea97ebf2b165f909d373890592d336d4.jpg)
Title: Re: Gravitational waves: rumors of their discovery
Post by: aitm on February 09, 2016, 08:31:24 PM
Quote from: stromboli on February 09, 2016, 08:26:00 PM
(https://s-media-cache-ak0.pinimg.com/564x/ea/97/eb/ea97ebf2b165f909d373890592d336d4.jpg)

Looks like a flock of seagulls at the top of the wave….now how does that help me? Honestly you people have no consideration for those of us unfortunate enough not to have had a decent eduction because we didn't give a fuck at the time……see…..I am disadvantaged.
Title: Re: Gravitational waves: rumors of their discovery
Post by: stromboli on February 09, 2016, 08:49:50 PM
Quote from: aitm on February 09, 2016, 08:31:24 PM
Looks like a flock of seagulls at the top of the wave….now how does that help me? Honestly you people have no consideration for those of us unfortunate enough not to have had a decent eduction because we didn't give a fuck at the time……see…..I am disadvantaged.

I'm in the same boat so don't feel too bad.
Title: Re: Gravitational waves: rumors of their discovery
Post by: josephpalazzo on February 10, 2016, 06:32:58 AM
Quote from: aitm on February 09, 2016, 08:31:24 PM
Looks like a flock of seagulls at the top of the wave….now how does that help me? Honestly you people have no consideration for those of us unfortunate enough not to have had a decent eduction because we didn't give a fuck at the time……see…..I am disadvantaged.

To make things as simple: (1) we have equations that describe a wave; (2) if we solve Einstein equation in General Relativity, you get that wave equation; (3) therefore we expect that gravitational waves should exist.

This was known since 1915, the year Einstein published his theory and all the predictions from the theory, but for g-waves, the technology wasn't there to detect them. So we're over 100 years since then, and if the discovery is confirmed, well Yaaaaaaaaaahoooooooooooooo....
Title: Re: Gravitational waves: rumors of their discovery
Post by: drunkenshoe on February 10, 2016, 09:07:28 AM
http://spaceplace.nasa.gov/ligo-g-waves/en/
Title: Re: Gravitational waves: rumors of their discovery
Post by: josephpalazzo on February 11, 2016, 10:46:18 AM
IT'S CONFIRMED :1rij: :1rij:
Title: Re: Gravitational waves: rumors of their discovery
Post by: stromboli on February 11, 2016, 01:22:13 PM
http://www.sciencemag.org/news/2016/02/gravitational-waves-einstein-s-ripples-spacetime-spotted-first-time

QuoteLong ago, deep in space, two massive black holesâ€"the ultrastrong gravitational fields left behind by gigantic stars that collapsed to infinitesimal pointsâ€"slowly drew together. The stellar ghosts spiraled ever closer, until, about 1.3 billion years ago, they whirled about each other at half the speed of light and finally merged. The collision sent a shudder through the universe: ripples in the fabric of space and time called gravitational waves. Five months ago, they washed past Earth. And, for the first time, physicists detected the waves, fulfilling a 4-decade quest and opening new eyes on the heavens

The discovery marks a triumph for the 1000 physicists with the Laser Interferometer Gravitational-Wave Observatory (LIGO), a pair of gigantic instruments in Hanford, Washington, and Livingston, Louisiana. Rumors of the detection had circulated for months. Today, at a press conference in Washington, D.C., the LIGO team made it official. “We did it!” says David Reitze, a physicist and LIGO executive director at the California Institute of Technology (Caltech) in Pasadena. “All the rumors swirling around out there got most of it right.”

Albert Einstein predicted the existence of gravitational waves 100 years ago, but directly detecting them required mind-boggling technological prowess and a history of hunting. (See a timeline below of the history of the search for gravitational waves.) LIGO researchers sensed a wave that stretched space by one part in 1021, making the entire Earth expand and contract by 1/100,000 of a nanometer, about the width of an atomic nucleus. The observation tests Einstein’s theory of gravity, the general theory of relativity, with unprecedented rigor and provides proof positive that black holes exist. “It will win a Nobel Prize,” says Marc Kamionkowski, a theorist at Johns Hopkins University in Baltimore, Maryland.

LIGO watches for a minuscule stretching of space with what amounts to ultraprecise rulers: two L-shaped contraptions called interferometers with arms 4 kilometers long. Mirrors at the ends of each arm form a long “resonant cavity,” in which laser light of a precise wavelength bounces back and forth, resonating just as sound of a specific pitch rings in an organ pipe. Where the arms meet, the two beams can overlap. If they have traveled different distances along the arms, their waves will wind up out of step and interfere with each other. That will cause some of the light to warble out through an exit called a dark port in synchrony with undulations of the wave.

From the interference, researchers can compare the relative lengths of the two arms to within 1/10,000 the width of a protonâ€"enough sensitivity to see a passing gravitational wave as it stretches the arms by different amounts. To spot such tiny displacements, however, scientists must damp out vibrations such as the rumble of seismic waves, the thrum of traffic, and the crashing of waves on distant coastlines.

Gravitational waves, Einstein’s ripples in spacetime, spotted for first time
By Adrian ChoFeb. 11, 2016 , 10:30 AM
Long ago, deep in space, two massive black holesâ€"the ultrastrong gravitational fields left behind by gigantic stars that collapsed to infinitesimal pointsâ€"slowly drew together. The stellar ghosts spiraled ever closer, until, about 1.3 billion years ago, they whirled about each other at half the speed of light and finally merged. The collision sent a shudder through the universe: ripples in the fabric of space and time called gravitational waves. Five months ago, they washed past Earth. And, for the first time, physicists detected the waves, fulfilling a 4-decade quest and opening new eyes on the heavens.

Gravitational waves, Einstein’s ripples in spacetime, spotted for first time
The discovery marks a triumph for the 1000 physicists with the Laser Interferometer Gravitational-Wave Observatory (LIGO), a pair of gigantic instruments in Hanford, Washington, and Livingston, Louisiana. Rumors of the detection had circulated for months. Today, at a press conference in Washington, D.C., the LIGO team made it official. “We did it!” says David Reitze, a physicist and LIGO executive director at the California Institute of Technology (Caltech) in Pasadena. “All the rumors swirling around out there got most of it right.”

Albert Einstein predicted the existence of gravitational waves 100 years ago, but directly detecting them required mind-boggling technological prowess and a history of hunting. (See a timeline below of the history of the search for gravitational waves.) LIGO researchers sensed a wave that stretched space by one part in 1021, making the entire Earth expand and contract by 1/100,000 of a nanometer, about the width of an atomic nucleus. The observation tests Einstein’s theory of gravity, the general theory of relativity, with unprecedented rigor and provides proof positive that black holes exist. “It will win a Nobel Prize,” says Marc Kamionkowski, a theorist at Johns Hopkins University in Baltimore, Maryland.

LIGO watches for a minuscule stretching of space with what amounts to ultraprecise rulers: two L-shaped contraptions called interferometers with arms 4 kilometers long. Mirrors at the ends of each arm form a long “resonant cavity,” in which laser light of a precise wavelength bounces back and forth, resonating just as sound of a specific pitch rings in an organ pipe. Where the arms meet, the two beams can overlap. If they have traveled different distances along the arms, their waves will wind up out of step and interfere with each other. That will cause some of the light to warble out through an exit called a dark port in synchrony with undulations of the wave.

From the interference, researchers can compare the relative lengths of the two arms to within 1/10,000 the width of a protonâ€"enough sensitivity to see a passing gravitational wave as it stretches the arms by different amounts. To spot such tiny displacements, however, scientists must damp out vibrations such as the rumble of seismic waves, the thrum of traffic, and the crashing of waves on distant coastlines.

Gravitational waves, Einstein’s ripples in spacetime, spotted for first time
V. Altounian/Science
On 14 September 2015, at 9:50:45 universal timeâ€"4:50 a.m. in Louisiana and 2:50 a.m. in Washingtonâ€"LIGO’s automated systems detected just such a signal. The oscillation emerged at a frequency of 35 cycles per second, or Hertz, and sped up to 250 Hz before disappearing 0.25 seconds later. The increasing frequency, or chirp, jibes with two massive bodies spiraling into each other. The 0.007-second delay between the signals in Louisiana and Washington is the right timing for a light-speed wave zipping across both detectors.

The signal exceeds the “five-sigma” standard of statistical significance that physicists use to claim a discovery, LIGO researchers report in a paper scheduled to be published in Physical Review Letters to coincide with the press conference. It’s so strong it can be seen in the raw data, says Gabriela González, a physicist at Louisiana State University, Baton Rouge, and spokesperson for the LIGO scientific collaboration. “If you filter the data, the signal is obvious to the eye,” she says.

Comparison with computer simulations reveals that the wave came from two objects 29 and 36 times as massive as the sun spiraling to within 210 kilometers of each other before merging. Only a black holeâ€"which is made of pure gravitational energy and gets its mass through Einstein’s famous equation E=mc2â€"can pack so much mass into so little space, says Bruce Allen, a LIGO member at the Max Planck Institute for Gravitational Physics in Hanover, Germany. The observation provides the first evidence for black holes that does not depend on watching hot gas or stars swirl around them at far greater distances. “Before, you could argue in principle whether or not black holes exist,” Allen says. “Now you can’t.”

The collision produced an astounding, invisible explosion. Modeling shows that the final black hole totals 62 solar massesâ€"3 solar masses less than the sum of the initial black holes. The missing mass vanished in gravitational radiationâ€"a conversion of mass to energy that makes an atomic bomb look like a spark. “For a tenth of a second [the collision] shines brighter than all of the stars in all the galaxies,” Allen says. “But only in gravitational waves.”

(http://www.sciencemag.org/sites/default/files/styles/inline_colwidth__16_9/public/images/60212_LIGO_web.png?itok=6MM9YETh)


:06: :08: :bravo_2:
Title: Re: Gravitational waves: rumors of their discovery
Post by: trdsf on February 11, 2016, 01:29:28 PM
Saw the news on the BBC website (they cover science on the front page).  Are there any of the major predictions of General Relativity left that haven't been observed, or was this the last big one?
Title: Re: Gravitational waves: rumors of their discovery
Post by: josephpalazzo on February 11, 2016, 02:15:42 PM
Quote from: trdsf on February 11, 2016, 01:29:28 PM
Saw the news on the BBC website (they cover science on the front page).  Are there any of the major predictions of General Relativity left that haven't been observed, or was this the last big one?

Mercury's perihelion glitch: check
Bending of light: check
Gravitational redshift: check
Equivalence Principle: check
Frame-dragging: check
Gravitational waves: check

I'm not aware of any other predictions, but so far, quite impressive.
Title: Re: Gravitational waves: rumors of their discovery
Post by: josephpalazzo on February 11, 2016, 04:57:18 PM
How g-waves sound:

http://gizmodo.com/this-is-what-gravitational-waves-sound-like-1758501755



Title: Re: Gravitational waves: rumors of their discovery
Post by: stromboli on February 11, 2016, 06:21:45 PM
JUST A REMINDER........

(http://inktank.fi/wp-content/uploads/2012/08/sciencevsfaith.jpg)
Title: Re: Gravitational waves: rumors of their discovery
Post by: Baruch on February 11, 2016, 08:26:15 PM
See section on Frame Dragging ... this is also confirmed ...
https://en.wikipedia.org/wiki/Tests_of_general_relativity

On the other hand my vote is with Dark Matter and Dark Energy ... which I don't see as quantum effects IMHO, since they are large scale phenomena.
Title: Re: Gravitational waves: rumors of their discovery
Post by: josephpalazzo on February 12, 2016, 04:36:56 AM
Quote from: stromboli on February 11, 2016, 06:21:45 PM


(http://inktank.fi/wp-content/uploads/2012/08/sciencevsfaith.jpg)

If you combine the two, this is what Christians are saying:

(http://i243.photobucket.com/albums/ff277/josephpalazzo/Godwaiting14Byrs.gif) (http://s243.photobucket.com/user/josephpalazzo/media/Godwaiting14Byrs.gif.html)
Title: Re: Gravitational waves: rumors of their discovery
Post by: josephpalazzo on February 12, 2016, 06:04:44 AM
A graphic explanation of g-waves given by PhD Comics:

http://www.phdcomics.com/comics.php?f=1853 (http://www.phdcomics.com/comics.php?f=1853)


The fluctuations caused in space by these waves can be as small as a few parts in 1023. Or as the PhD Comics put it: Telling that a stick 1,000,000,000,000,000,000,000 meters long has shrunk by 5 millimeters.

For anyone trying to comprehend this, it's like the diameter of the ENTIRE  MILKY WAY GALAXY being shorter by the width of a pencil.
Title: Re: Gravitational waves: rumors of their discovery
Post by: stromboli on February 12, 2016, 09:18:23 AM
Just discovered that Kip Thorne is an ex-Mormon atheist. While drinking my coffee and sitting here in my non Mormon Starter shorts and T shirt. Good way to start the day, imo.
Title: Re: Gravitational waves: rumors of their discovery
Post by: josephpalazzo on February 12, 2016, 11:35:18 AM
Quote from: stromboli on February 12, 2016, 09:18:23 AM
Just discovered that Kip Thorne is an ex-Mormon atheist. While drinking my coffee and sitting here in my non Mormon Starter shorts and T shirt. Good way to start the day, imo.

He's one of the author of the MTW's Gravitation - the bible on GR (Thorn is the T in MTW).

At Amazon, price: $347 for the paperback. I have a copy, which I paid less than $100, a few years back then. And yes, I went through it but not all of it (1279 pages long). Because of its unorthodox math approach, it is not use very much as a class textbook.  The Hartle book is the one most used as your standard textbook in GR. I have that one too.In all I have 11 textbooks on GR. I'm not going to say how many I have on QFT...:-)
Title: Re: Gravitational waves: rumors of their discovery
Post by: stromboli on February 12, 2016, 11:36:56 AM
Quote from: josephpalazzo on February 12, 2016, 11:35:18 AM
He's one of the author of the MTW's Gravitation - the bible on GR (Thorn is the T in MTW).

At Amazon, price: $347 for the paperback. I have a copy, which I paid less than $100, a few years back then. And yes, I went through it but not all of it (1279 pages long). Because of its unorthodox math approach, it is not use very much as a class textbook.  The Hartle book is the one most used as your standard textbook in GR. I have that one too.In all I have 11 textbooks on GR. I'm not going to say how many I have on QFT...:-)

Ooh you bibliophile you.
Title: Re: Gravitational waves: rumors of their discovery
Post by: josephpalazzo on February 12, 2016, 12:01:03 PM
Quote from: stromboli on February 12, 2016, 11:36:56 AM
Ooh you bibliophile you.

You're not kidding. I have two rooms that are used as library rooms: one for all books, except physics books which I keep in the second room.
Title: Re: Gravitational waves: rumors of their discovery
Post by: PopeyesPappy on February 13, 2016, 09:39:50 AM
Quote from: josephpalazzo on February 12, 2016, 06:04:44 AM
A graphic explanation of g-waves given by PhD Comics:

http://www.phdcomics.com/comics.php?f=1853 (http://www.phdcomics.com/comics.php?f=1853)


The fluctuations caused in space by these waves can be as small as a few parts in 1023. Or as the PhD Comics put it: Telling that a stick 1,000,000,000,000,000,000,000 meters long has shrunk by 5 millimeters.

For anyone trying to comprehend this, it's like the diameter of the ENTIRE  MILKY WAY GALAXY being shorter by the width of a pencil.


Question for you Joe. Back around 2000 I was at the Madrid Deep Space Communication Complex because we were getting ready to renew Telefónica's 7 men and truck 24x7 support contract with NASA. While I was there the old phd in charge of the place talked to me about his pet project. He was working with Goddard to develop a clock that was accurate to 10-16 because they thought they might be able to use it to measure gravity waves. Going on 20 years later we still aren't there as NIST's F1 clock is only good to about 3.1 x 10-16.

The question to you is based on what you've said here what we really need is a clock that is accurate to 10-23 to accurately and easily detect and measure gravity waves? If that is true could we also use such a clock if it existed to manipulate or reproduce gravity waves?
Title: Re: Gravitational waves: rumors of their discovery
Post by: josephpalazzo on February 13, 2016, 11:03:19 AM
Quote from: PopeyesPappy on February 13, 2016, 09:39:50 AM
Question for you Joe. Back around 2000 I was at the Madrid Deep Space Communication Complex because we were getting ready to renew Telefónica's 7 men and truck 24x7 support contract with NASA. While I was there the old phd in charge of the place talked to me about his pet project. He was working with Goddard to develop a clock that was accurate to 10-16 because they thought they might be able to use it to measure gravity waves. Going on 20 years later we still aren't there as NIST's F1 clock is only good to about 3.1 x 10-16.

The question to you is based on what you've said here what we really need is a clock that is accurate to 10-23 to accurately and easily detect and measure gravity waves? If that is true could we also use such a clock if it existed to manipulate or reproduce gravity waves?

I'm not sure about those two ideas except to say they are different phenomena. A wave is produced by some mechanism: for instance plunge your finger slightly into the water and pull it up and down and you will create waves that expand circularly. Gravitational waves are a version of that with two black holes rapidly rotating about each other, disrupting enough the fabric of space-time to give g-waves strong enough for us to detect. OTHO, a clock is an apparatus that ticks. A pendulum can make a repeated tick; your wristwatch has rotating wheels to make a succession of ticks, etc. Your question: can you take g-waves into some kind of apparatus that would produce a succession of ticks ( that is, a clock)? Perhaps, but I haven't the slightest idea how that would be done.
Title: Re: Gravitational waves: rumors of their discovery
Post by: Baruch on February 13, 2016, 11:21:33 AM
Quantum clock at 8.6 × 10âˆ'18 in 2010 is most accurate on a research platform ... over 100 times more accurate than F1 clock

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

Pretty damn precise.  Metrology is sensitive stuff ... when an atomic clock can detect the change in speed of rotation of the Earth, because of the big Japan quake.
Title: Re: Gravitational waves: rumors of their discovery
Post by: PopeyesPappy on February 13, 2016, 12:09:01 PM
Quote from: josephpalazzo on February 13, 2016, 11:03:19 AM
I'm not sure about those two ideas except to say they are different phenomena. A wave is produced by some mechanism: for instance plunge your finger slightly into the water and pull it up and down and you will create waves that expand circularly. Gravitational waves are a version of that with two black holes rapidly rotating about each other, disrupting enough the fabric of space-time to give g-waves strong enough for us to detect. OTHO, a clock is an apparatus that ticks. A pendulum can make a repeated tick; your wristwatch has rotating wheels to make a succession of ticks, etc. Your question: can you take g-waves into some kind of apparatus that would produce a succession of ticks ( that is, a clock)? Perhaps, but I haven't the slightest idea how that would be done.

I guess the theory is that gravity operates at some frequency range similar to how sound, radio or light does. Gravity just works at much higher frequency than any of those. In order to detect, manipulate or reproduce those things you need a receiver or transmitter capable of reproducing the same frequency range of whatever it is you want to observe or reproduce. If gravity does operate at some frequency range then the easiest way to detect or reproduce it would require a clock capable of accurately reproducing that frequency range. What I don't know is if we currently believe that gravity operates at some really high frequency range, or if that line of thought has been rejected since I was at the MDSCC.

From what I understand about LIGO they are getting around the need for more accurate clocks by comparing the differences between two distantly separated receivers. It works. Barely. But it would be much more accurate and they would be able to see a lot more with higher frequency clocks at the two receivers.
Title: Re: Gravitational waves: rumors of their discovery
Post by: josephpalazzo on February 13, 2016, 01:02:49 PM
Quote from: PopeyesPappy on February 13, 2016, 12:09:01 PM
I guess the theory is that gravity operates at some frequency range similar to how sound, radio or light does. Gravity just works at much higher frequency than any of those. In order to detect, manipulate or reproduce those things you need a receiver or transmitter capable of reproducing the same frequency range of whatever it is you want to observe or reproduce. If gravity does operate at some frequency range then the easiest way to detect or reproduce it would require a clock capable of accurately reproducing that frequency range. What I don't know is if we currently believe that gravity operates at some really high frequency range, or if that line of thought has been rejected since I was at the MDSCC.

From what I understand about LIGO they are getting around the need for more accurate clocks by comparing the differences between two distantly separated receivers. It works. Barely. But it would be much more accurate and they would be able to see a lot more with higher frequency clocks at the two receivers.

It's not a question of being at a high frequency. For a clock to work, you need regular beats. Now atomic clocks work on QM principles that the energy levels in any atom are quantized, It's like a vending machine that accepts only 1¢, 5¢. 10¢ and 25¢. So if you try anything else it won't accept it. So, using this concept in QM with atoms for which you know precisely the energy levels, you can build clocks that are precise and reliable. In the case of g-waves, the objects producing them - black holes, for instance- you have no way of knowing if the beats that are coming in will be regular, that is the time between each beat would have to be exactly the same within a certain margin of error. Two black holes can speed up or down depending what's in their immediate environment, hence that process would not be reliable. So I guess the trick would be to manufacture these g-waves that would give you regular beats and strong enough to register on your counter, but how, since rotating black holes themselves gives waves that are so weak you need to build something the size of LIGO to detect them!!
Title: Re: Gravitational waves: rumors of their discovery
Post by: trdsf on February 13, 2016, 01:14:16 PM
Quote from: Baruch on February 11, 2016, 08:26:15 PM
See section on Frame Dragging ... this is also confirmed ...
https://en.wikipedia.org/wiki/Tests_of_general_relativity

On the other hand my vote is with Dark Matter and Dark Energy ... which I don't see as quantum effects IMHO, since they are large scale phenomena.
Dark matter and dark energy are already accounted for in General Relativity, under the term Λ (lambda) -- originally introduced as the cosmological constant when he was trying to construct a static model of the universe.  After Hubble, he just set it to zero, but the discovery of the accelerating expansion of the universe makes it possible that Λ is not zero after all.  At a minimum, the effects of dark matter and dark energy can be treated mathematically as Λ in GR, even if they're not an actual structural alteration of space itself.
Title: Re: Gravitational waves: rumors of their discovery
Post by: Baruch on February 13, 2016, 07:45:57 PM
Quote from: trdsf on February 13, 2016, 01:14:16 PM
Dark matter and dark energy are already accounted for in General Relativity, under the term Λ (lambda) -- originally introduced as the cosmological constant when he was trying to construct a static model of the universe.  After Hubble, he just set it to zero, but the discovery of the accelerating expansion of the universe makes it possible that Λ is not zero after all.  At a minimum, the effects of dark matter and dark energy can be treated mathematically as Λ in GR, even if they're not an actual structural alteration of space itself.

Except that is a cop-out.  Lambda is a cheat.  GR is wrong anyway, since QFT is right.  Like fighting over the scraps left over from Newtonian physics.  SR/GR is classical ... if Lambda explains everything, why are theoreticians and experimenters looking deeper?
Title: Re: Gravitational waves: rumors of their discovery
Post by: josephpalazzo on February 14, 2016, 11:44:15 AM
Quote from: trdsf on February 13, 2016, 01:14:16 PM
Dark matter and dark energy are already accounted for in General Relativity, under the term Λ (lambda) -- originally introduced as the cosmological constant when he was trying to construct a static model of the universe.  After Hubble, he just set it to zero, but the discovery of the accelerating expansion of the universe makes it possible that Λ is not zero after all.  At a minimum, the effects of dark matter and dark energy can be treated mathematically as Λ in GR, even if they're not an actual structural alteration of space itself.

Characterizing the cosmological constant Λ as an introduction can lead to some misinterpretation, especially those who have a superficial understanding of GR. Λ comes out of the solution to the Einstein Equations. It's legitimate, and not a cop-out solution (I know you didn't say but someone else did). What the theory doesn't do is set a value to it. That leaves it open to be determined by observation. As it stands today its value is  of the order of 10-29g/cm3, in metric units.
Title: Re: Gravitational waves: rumors of their discovery
Post by: trdsf on February 16, 2016, 04:16:05 PM
Quote from: Baruch on February 13, 2016, 07:45:57 PM
Except that is a cop-out.  Lambda is a cheat.  GR is wrong anyway, since QFT is right.  Like fighting over the scraps left over from Newtonian physics.  SR/GR is classical ... if Lambda explains everything, why are theoreticians and experimenters looking deeper?
Wrong again.

Lambda was a 'fudge factor' when Einstein inserted it in order to get the static universe he assumed and was ignored after Hubble, and only in light of the discovery of accelerating expansion has it been revived.  It's not meant to explain anything, it's descriptive, and the research is to determine if it actually does have a value, what value it has, and if it's non-zero, why it's non-zero.  I really shouldn't have to explain this.

You're also incorrect in saying GR is wrong and QM is right -- if Quantum Field Theory were right and General Relativity were wrong, then QFT would already be a theory of quantum gravity, and it is not.

GR has yet to be invalidated by an observation -- all we can say is that we know where it breaks down, not that it's incorrect.  And what we know is that both of them give nonsensical answers when they're combined.  What's most likely is not that either one is wrong, but that both are incomplete, just like Newtonian gravity was incomplete.  That incompleteness didn't make Newton useless: we still don't need anything more than Newton to calculate the flights of every spacecraft we've ever launched.  Using Einstein would only make matters unnecessarily complex, and the additional couple of decimal places gained would be irrelevant.

Whatever theory manages to combine GR and QM is going to have to duplicate their results at sufficiently low energy levels, with considerable accuracy, because we have already measured both those theories with considerable accuracy, and it doesn't matter if it's string theory, M theory, or something no one has come up with yet.  Both GR and QFT are approximations, but they are deeply and profoundly accurate approximations, and any unified theory has to be at least as accurate as both.

Keep in mind also that 'dark energy' and 'dark matter' are just labels: they don't explain anything either.  They mark the place where researchers have observed something, and don't know what it is yet, but they know something is there.  There's nothing wrong with placeholders in science -- those are the things that need further observations and research, after all.
Title: Re: Gravitational waves: rumors of their discovery
Post by: josephpalazzo on February 16, 2016, 06:42:58 PM
@trdsf

The cosmological constant is about 10-9joules per m3  in order to account for the observed acceleration of the universe. If you calculate the equivalent of a 100-watt light-bulb (3.6 x 105 joules), you would need to harvest the energy of a sphere of a 44km- or 27.5 mile-radius. And that's not counting the energy required to harvest that energy, which probably would make that enterprise a no go. The other interesting feature is that if you calculate the vacuum energy from QFT, it is 10113 joules per m3, that is, 10124bigger than the cosmological constant - that mismatch bears the name of the vacuum catastrophe.
Title: Re: Gravitational waves: rumors of their discovery
Post by: trdsf on February 16, 2016, 09:42:31 PM
Quote from: josephpalazzo on February 16, 2016, 06:42:58 PM
@trdsf

The cosmological constant is about 10-9joules per m3  in order to account for the observed acceleration of the universe. If you calculate the equivalent of a 100-watt light-bulb (3.6 x 105 joules), you would need to harvest the energy of a sphere of a 44km- or 27.5 mile-radius. And that's not counting the energy required to harvest that energy, which probably would make that enterprise a no go. The other interesting feature is that if you calculate the vacuum energy from QFT, it is 10113 joules per m3, that is, 10124bigger than the cosmological constant - that mismatch bears the name of the vacuum catastrophe.
Thank you, that was the prediction mismatch that I was trying to remember and couldn't, so I left it out rather than get it wrong.  I knew it was on the order of 10120, which is a hell of a miss.  Even astronomers -- who can get away with with a discrepancy of some 300 billion in their estimate of the total number of stars in this galaxy -- would be embarrassed by a miss that wide.  :)
Title: Re: Gravitational waves: rumors of their discovery
Post by: josephpalazzo on February 19, 2016, 05:46:41 PM
Quote from: trdsf on February 16, 2016, 09:42:31 PM
Thank you, that was the prediction mismatch that I was trying to remember and couldn't, so I left it out rather than get it wrong.  I knew it was on the order of 10120, which is a hell of a miss.  Even astronomers -- who can get away with with a discrepancy of some 300 billion in their estimate of the total number of stars in this galaxy -- would be embarrassed by a miss that wide.  :)

According to this paper, Cosmological constant and vacuum energy: old and new ideas (http://arxiv.org/pdf/1306.1527v3.pdf), the discrepancy has been reduced to 55 orders of magnitude, mainly due to the discovery of the Higgs boson, but still a long way to go...
Title: Re: Gravitational waves: rumors of their discovery
Post by: stromboli on February 25, 2016, 11:05:23 AM
https://www.youtube.com/watch?v=ajZojAwfEbs&feature=youtu.be
Title: Re: Gravitational waves: rumors of their discovery
Post by: josephpalazzo on February 25, 2016, 11:36:19 AM
Quote from: stromboli on February 25, 2016, 11:05:23 AM
https://www.youtube.com/watch?v=ajZojAwfEbs&feature=youtu.be

Good explanation from Brian Greene. Just a minor beef: these gravitational waves are ripples in spacetime, not in space. It's a common mistake that is often overlooked. But Greene should know better... I'm just knit-picking...
Title: Re: Gravitational waves: rumors of their discovery
Post by: Baruch on February 25, 2016, 12:44:58 PM
I am no fan of Dr Greene.  But I am even less a fan of Dr Kaku.  There is subtle difference between popularizing science, dumbing-down science and science boosterism.  I really like the old book by Gleick on Chaos.
Title: Re: Gravitational waves: rumors of their discovery
Post by: surreptitious57 on March 10, 2016, 02:47:55 AM
Gravitational waves propagate at light speed just as photons but do they have an infinite life
span like them also ? If they do then presumably they carry on travelling through space time
right up until the heat death of the universe. The two black holes which collided were not the
same size so why did the large one not absorb the small one ? Was this because the collision
did not actually happen at its event horizon ? Which is only where one can absorb any matter 
Title: Re: Gravitational waves: rumors of their discovery
Post by: Baruch on March 10, 2016, 07:36:14 AM
Quote from: surreptitious57 on March 10, 2016, 02:47:55 AM
Gravitational waves propagate at light speed just as photons but do they have an infinite life
span like them also ? If they do then presumably they carry on travelling through space time
right up until the heat death of the universe. The two black holes which collided were not the
same size so why did the large one not absorb the small one ? Was this because the collision
did not actually happen at its event horizon ? Which is only where one can absorb any matter

Good questions ... the conventional answer is that photons and gravitons (if gravity is quantized) travel until they are absorbed.  They don't literally go on forever ... but not-forever can be a long time.  That is why we can see "light" from the 3K event (Big Bang cooling).  By intercepting that light, we have murdered some innocent photons.

Collisions between Black Holes would be complicated ... the stuff outside the Black Hole, some of it will be absorbed by the combined Black Hole, and some of it will not.  This includes spiraling hot matter (X-ray hot) and gravitons.
Title: Re: Gravitational waves: rumors of their discovery
Post by: josephpalazzo on March 10, 2016, 02:10:50 PM
Quote from: surreptitious57 on March 10, 2016, 02:47:55 AM
Gravitational waves propagate at light speed just as photons but do they have an infinite life
span like them also ? If they do then presumably they carry on travelling through space time
right up until the heat death of the universe.

For the photon, and for any other particle with zero mass, time is a meaningless concept.

QuoteThe two black holes which collided were not the
same size so why did the large one not absorb the small one ? Was this because the collision
did not actually happen at its event horizon ? Which is only where one can absorb any matter 

The signal we get is too faint to know what is really going on. It will be one of the challenges to figure out what the g-waves say. But already we can tell it's two rotating massive objects - the strength of the collision created a gravitational field so strong that it distorted space-time in waves that spread throughout space about 50 times stronger than all the stars and galaxies in the universe.