Author Topic: Gravitational waves: rumors of their discovery  (Read 3396 times)

Re: Gravitational waves: rumors of their discovery
« Reply #15 on: February 11, 2016, 01:22:13 PM »
http://www.sciencemag.org/news/2016/02/gravitational-waves-einstein-s-ripples-spacetime-spotted-first-time

Quote
Long ago, deep in space, two massive black holes—the ultrastrong gravitational fields left behind by gigantic stars that collapsed to infinitesimal points—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 proton—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 holes—the ultrastrong gravitational fields left behind by gigantic stars that collapsed to infinitesimal points—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 proton—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 time—4:50 a.m. in Louisiana and 2:50 a.m. in Washington—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 hole—which is made of pure gravitational energy and gets its mass through Einstein’s famous equation E=mc2—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 masses—3 solar masses less than the sum of the initial black holes. The missing mass vanished in gravitational radiation—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.”




 :06: :08: :bravo_2:

Offline trdsf

Re: Gravitational waves: rumors of their discovery
« Reply #16 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?
"It's hard to be religious when certain people are never incinerated by bolts of lightning." -- Calvin and Hobbes
"Confused? At a loss for what to do? Wow, sounds like you're human. Good luck." -- Welcome to Night Vale

Offline josephpalazzo (OP)

Re: Gravitational waves: rumors of their discovery
« Reply #17 on: February 11, 2016, 02:15:42 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.

Offline josephpalazzo (OP)


Re: Gravitational waves: rumors of their discovery
« Reply #19 on: February 11, 2016, 06:21:45 PM »
JUST A REMINDER........


Offline Baruch

Re: Gravitational waves: rumors of their discovery
« Reply #20 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.
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Offline josephpalazzo (OP)

Re: Gravitational waves: rumors of their discovery
« Reply #21 on: February 12, 2016, 04:36:56 AM »


(Image removed from quote.)

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


Offline josephpalazzo (OP)

Re: Gravitational waves: rumors of their discovery
« Reply #22 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


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.

Re: Gravitational waves: rumors of their discovery
« Reply #23 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.

Offline josephpalazzo (OP)

Re: Gravitational waves: rumors of their discovery
« Reply #24 on: February 12, 2016, 11:35:18 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...:-)

Re: Gravitational waves: rumors of their discovery
« Reply #25 on: February 12, 2016, 11:36:56 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.

Offline josephpalazzo (OP)

Re: Gravitational waves: rumors of their discovery
« Reply #26 on: February 12, 2016, 12:01:03 PM »
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.

Re: Gravitational waves: rumors of their discovery
« Reply #27 on: February 13, 2016, 09:39:50 AM »
A graphic explanation of g-waves given by PhD Comics:

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?
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Offline josephpalazzo (OP)

Re: Gravitational waves: rumors of their discovery
« Reply #28 on: February 13, 2016, 11:03:19 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.

Offline Baruch

Re: Gravitational waves: rumors of their discovery
« Reply #29 on: February 13, 2016, 11:21:33 AM »
Quantum clock at 8.6 × 10−18 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.
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