About LIGO and Gravitational Wave Detection.

[JohnSSM]

I have a question about the subject of gravitational waves that LIGO is searching for in their split laser light experiments. The question arose after i read an article about LIGO.

The article describes the 2 detectors separated by 1865 miles, because the scientists have estimated that the wavelength of gravitational waves would be 1865 miles.

Considering that general relativity is based upon geometry and math and no medium is actually described, even though they often use "fabric of space time" in such ways, do they consider gravitational waves to simply be geometrical entities as well? I grasped the possibility of the idea that gravity can be explained by relative motions and energies, and that it is a geometrical phenomenon that creates a relative effect we call gravity. But now, thinking about waves travelling through space, driven by an event which is billions of years old (big bang), its hard to imagine that geometrical and relative effects could account for that.

Other general questions about gravitational waves.

DO they have a direction or vector as other types of waves? Cant we use the direction that a waveform is travelling to figure the origin of the wave? OR at least the direction from which the wave was last influenced? If they were trying to encounter the wave by estimating the wavelength, wouldnt they also need to set up the experiment on the proper vector of the waveform? Many antennas work in this way. Is LIGO essentially a huge antenna? If so, it just makes gravity seem much more real than a geometrical effect of relativity.

[ajb]

Considering that general relativity is based upon geometry and math and no medium is actually described, even though they often use "fabric of space time" in such ways, do they consider gravitational waves to simply be geometrical entities as well?

In essence yes. Gravitational waves are small ripples in the local geometry of space-time.

 

 

Cant we use the direction that a waveform is travelling to figure the origin of the wave?

By using more than one detector it should be possible to identify the location in sky of the source. This is one reason that people are interested in building a global network of detectors.

[altamash(einstein)]

First of all, its a rumour about the gravitational waves, scientists have not successfully detected ripples/ curvature of spacetime,whenit comes to big bang ripples, all we have is dust in the wind. In March of last year, a team of astronomers working with the BICEP2 telescope at the South Pole caused a flurry of excitement when they claimed to have discovered evidence for primordial gravitational waves, ripples in space-time triggered by a growth spurt in the universe’s early days.Gravitational waves are thought to have been produced when the universe went through an incredibly rapid period of inflation in the fractions of a second after the big bang. Discovering them, and thus proving inflation to be true, is central to many of our theories about the early universe. Some cosmologists even argue that finding the primordial waves would be indirect evidence that parallel universe exist

The Universe began about 13.8 billion years ago and evolved from an extremely hot, dense and uniform state to the rich and complex cosmos of galaxies, stars and planets we see today.

An extraordinary source of information about the Universe’s history is the Cosmic Microwave Background, or CMB, the legacy of light emitted only 380 000 years after the Big Bang.

ESA’s Planck satellite observed this background across the whole sky with unprecedented accuracy, and a broad variety of new findings about the early Universe has already been revealed over the past two years.

But astronomers are still digging ever deeper in the hope of exploring even further back in time: they are searching for a particular signature of cosmic ‘inflation’ – a very brief accelerated expansion that, according to current theory, the Universe experienced when it was only the tiniest fraction of a second old.

This signature would be seeded by gravitational waves, tiny perturbations in the fabric of space-time, that astronomers believe would have been generated during the inflationary phase.

Interestingly, these perturbations should leave an imprint on another feature of the cosmic background: its polarisation.

When light waves vibrate preferentially in a certain direction, we say the light is polarised.

The CMB is polarised, exhibiting a complex arrangement across the sky. This arises from the combination of two basic patterns: circular and radial (known as E-modes), and curly (B-modes).

Different phenomena in the Universe produce either E- or B-modes on different angular scales and identifying the various contributions requires extremely precise measurements. It is the B-modes that could hold the prize of probing the Universe’s early inflation.

“Searching for this unique record of the very early Universe is as difficult as it is exciting, since this subtle signal is hidden in the polarisation of the CMB, which itself only represents only a feeble few percent of the total light,” says Jan Tauber, ESA’s project scientist for Planck.

Planck is not alone in this search. In early 2014, another team of astronomers presented results based on observations of the polarised CMB on a small patch of the sky performed 2010–12 with BICEP2, an experiment located at the South Pole. The team also used preliminary data from another South Pole experiment, the Keck Array.

They found something new: curly B-modes in the polarisation observed over stretches of the sky a few times larger than the size of the full Moon.

The BICEP2 team presented evidence favouring the interpretation that this signal originated in primordial gravitational waves, sparking an enormous response in the academic community and general public.

However, there is another contender in this game that can produce a similar effect: interstellar dust in our Galaxy, the Milky Way.

[ajb]

First of all, its a rumour about the gravitational waves, scientists have not successfully detected ripples/ curvature of spacetime

I think the question is about direct detection of gravitational waves. We have some more indirect evidence, as you say from the CMBR and studies of binary pulsars.

[altamash(einstein)]

Nope, We Have Not Detected Gravitational Waves (Yet) Leaked news from teams studying the early universe says the signal hailed as our first peek at space-time ripples really is just dust

image: http://thumbs.media.smithsonianmag.com//filer/8f/bd/8fbd1cc4-210a-410c-98dc-fc3fc6dead80/bicep_2_sunset__bicep2.jpg__800x600_q85_crop.jpg

 

when it comes to big bang ripples, all we have is dust in the wind. In March of last year, a team of astronomers working with the BICEP2 telescope at the South Pole caused a flurry of excitement when they claimed to have discovered evidence for primordial gravitational waves, ripples in space-time triggered by a growth spurt in the universe’s early days. However, a leaked press release has teased the results from a long-awaited joint analysis between BICEP2 and a European space telescope team, the Planck collaboration. As many had feared, the release says that the signal was caused by something much more mundane: dust.

 

 

Gravitational waves are thought to have been produced when the universe went through an incredibly rapid period of inflation in the fractions of a second after the big bang. Discovering them, and thus proving inflation to be true, is central to many of our theories about the early universe. Some cosmologists even argue that finding the primordial waves would be indirect evidence that parallel universes exist.

Using powerful telescopes like BICEP2 and Planck, astronomers have been hunting for signs of these waves in the cosmic microwave background (CMB), ancient light that was emitted just 380,000 years after the big bang and that now permeates the cosmos. Theory says that the waves would have created a distinct swirly pattern in the CMB known as B-mode polarization.

 

This is what BICEP2 reportedly discovered last year. Their analysis, based on three years of observing a single patch of sky, showed a B-mode pattern that was even stronger than expected—almost double the strength it should be based on preliminary studies carried out by Planck in 2013. However, this polarization signal can be caused by other phenomena, such as charged particles moving around in our galaxy’s magnetic field and, most notably, emissions from intergalactic dust. The BICEP2 researchers did correct for possible contamination from other sources, but it was unclear if the values used were accurate.

 

“A number of papers have been written over the last year taking a closer look at the data and trying alternative methods of doing the analysis,” says Phil Bull of the University of Oslo, Norway. “Many of these suggested that polarized dust emission from our own galaxy could be significantly more important than the BICEP2 team originally thought.”

 

A cross-correlation of data from Planck, BICEP2 and the Keck Array has been eagerly anticipated by astronomers for months. BICEP2 could only study a small part of the sky in a small wavelength range. Planck was able to look at more of the sky in other parts of the spectrum known to be dominated by dust emission, enabling the collaborations to combine forces to identify and isolate the dust within the signal.

 

Now comes the killer blow for BICEP2. According to the leaked release, which has since been taken offline, the new analysis of polarized dust emission within our galaxy by Planck, BICEP2 and Keck confirms that BICEP2 “significantly underestimated” the amount of dust contributing to their data.

 

“To be blunt, the BICEP2 measurement is a null result for primordial gravitational waves,” writes Peter Coles of the University of Sussex, UK, in a blog post today. “It’s by no means a proof that there are no gravitational waves at all, but it isn’t a detection.”

 

The data now show that the BICEP2 signal is only very slightly larger than the contribution from intergalactic dust itself. Once the polarized emissions from dust have been subtracted from the B-mode signal, the remainder is too small to be considered a detection, the Planck team says in the release. The document appeared on an official Planck website in French, but according to a translation, the team says the gravitational wave signal is at most half as strong as previously estimated. A full paper on the results of the joint analysis has been submitted to the journal Physical Review Letters, and a preprint is now online.

 

“The sad thing is that the more data you add in, the more the gravitational wave signal seems to fade,” says Andrew Pontzen of University College London, UK. “But it’s possible they’re homing in on a signal, just at a lower intensity than originally thought. This search is far from over.”

 

 

Nope, We Have Not Detected Gravitational Waves (Yet) Leaked news from teams studying the early universe says the signal hailed as our first peek at space-time ripples really is just dust

image: http://thumbs.media.smithsonianmag.com//filer/8f/bd/8fbd1cc4-210a-410c-98dc-fc3fc6dead80/bicep_2_sunset__bicep2.jpg__800x600_q85_crop.jpg

 

 

217702110266

When it comes to big bang ripples, all we have is dust in the wind. In March of last year, a team of astronomers working with the BICEP2 telescope at the South Pole caused a flurry of excitement when they claimed to have discovered evidence for primordial gravitational waves, ripples in space-time triggered by a growth spurt in the universe’s early days. However, a leaked press release has teased the results from a long-awaited joint analysis between BICEP2 and a European space telescope team, the Planck collaboration. As many had feared, the release says that the signal was caused by something much more mundane: dust.

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(Update: ESA has now posted a news release confirming that the joint analysis has found no conclusive evidence for gravitational waves.)

 

Gravitational waves are thought to have been produced when the universe went through an incredibly rapid period of inflation in the fractions of a second after the big bang. Discovering them, and thus proving inflation to be true, is central to many of our theories about the early universe. Some cosmologists even argue that finding the primordial waves would be indirect evidence that parallel universes exist.

Using powerful telescopes like BICEP2 and Planck, astronomers have been hunting for signs of these waves in the cosmic microwave background (CMB), ancient light that was emitted just 380,000 years after the big bang and that now permeates the cosmos. Theory says that the waves would have created a distinct swirly pattern in the CMB known as B-mode polarization.

 

This is what BICEP2 reportedly discovered last year. Their analysis, based on three years of observing a single patch of sky, showed a B-mode pattern that was even stronger than expected—almost double the strength it should be based on preliminary studies carried out by Planck in 2013. However, this polarization signal can be caused by other phenomena, such as charged particles moving around in our galaxy’s magnetic field and, most notably, emissions from intergalactic dust. The BICEP2 researchers did correct for possible contamination from other sources, but it was unclear if the values used were accurate.

 

“A number of papers have been written over the last year taking a closer look at the data and trying alternative methods of doing the analysis,” says Phil Bull of the University of Oslo, Norway. “Many of these suggested that polarized dust emission from our own galaxy could be significantly more important than the BICEP2 team originally thought.”

 

A cross-correlation of data from Planck, BICEP2 and the Keck Array has been eagerly anticipated by astronomers for months. BICEP2 could only study a small part of the sky in a small wavelength range. Planck was able to look at more of the sky in other parts of the spectrum known to be dominated by dust emission, enabling the collaborations to combine forces to identify and isolate the dust within the signal.

 

Now comes the killer blow for BICEP2. According to the leaked release, which has since been taken offline, the new analysis of polarized dust emission within our galaxy by Planck, BICEP2 and Keck confirms that BICEP2 “significantly underestimated” the amount of dust contributing to their data.

 

“To be blunt, the BICEP2 measurement is a null result for primordial gravitational waves,” writes Peter Coles of the University of Sussex, UK, in a blog post today. “It’s by no means a proof that there are no gravitational waves at all, but it isn’t a detection.”

 

The data now show that the BICEP2 signal is only very slightly larger than the contribution from intergalactic dust itself. Once the polarized emissions from dust have been subtracted from the B-mode signal, the remainder is too small to be considered a detection, the Planck team says in the release. The document appeared on an official Planck website in French, but according to a translation, the team says the gravitational wave signal is at most half as strong as previously estimated. A full paper on the results of the joint analysis has been submitted to the journal Physical Review Letters, and a preprint is now online.

 

“The sad thing is that the more data you add in, the more the gravitational wave signal seems to fade,” says Andrew Pontzen of University College London, UK. “But it’s possible they’re homing in on a signal, just at a lower intensity than originally thought. This search is far from over.”

 

[ajb]

Nope, We Have Not Detected Gravitational Waves

Nobody here has said that we have detected gravitational waves, and for sure not directly.

 

In fact, the BICEP2 team withdrew their claim to have found the first evidence for gravitational waves in the CMBR. The most likely explanation for what they detected is, as you say dust. Both BICEP2 and Keck Array experiments have found no conclusive evidence of primordial gravitational waves, but still the CMBR is probabily a good place to look..

[Strange]

First of all, its a rumour about the gravitational waves, scientists have not successfully detected ripples/ curvature of spacetime,

 

This is partly true. Curvature of spacetime has been detected, in several ways. Gravitational waves have not (yet) been detected.

 

I get the impression that parts (most? all?) of the rest of your post is copied from elsewhere. Could you please make it clearer what is your own material and what you are quoting (and where from). Thanks.

[altamash(einstein)]

 

This is partly true. Curvature of spacetime has been detected, in several ways. Gravitational waves have not (yet) been detected.

 

I get the impression that parts (most? all?) of the rest of your post is copied from elsewhere. Could you please make it clearer what is your own material and what you are quoting (and where from). Thanks.

yes, i have searched this stuff and pasted it here

Edited January 16, 2016 by altamash(einstein)

[StringJunky]

yes, i have searched this stuff and pasted it here

It's OK to use online stuff (part of an article anyway) but it is important you attribute authorship with a link and separate your writing from your quotes. It's called 'plagiarism, otherwise, which is illegal and not just against forum rules.