LIGO and speed of gravitational waves

In summary, LIGO is a gravitational wave detector that uses high-power laser beams to measure changes in test mass distances. It was first proposed by physicist Joseph Weber, who claimed to have detected gravitational waves in the late 1960s. However, his results were met with skepticism and current experiments, such as LIGO and LISA, are still ongoing. LIGO employs a 4-kilometer long vacuum pipe in the shape of an L with test masses at each end. The laser beams are bounced back and forth multiple times to increase the sensitivity of the detector. Gravitational waves can pass through anything and have the ability to squeeze and stretch masses, but they are hard to detect due to their small amplitude. Understanding the concept of propagation
  • #1
kurious
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LIGO may have failed to detect gravity waves because they move faster than light and so have a greater wavelength than expected and probably a lower amplitude too.
 
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  • #2
Gravitational waves "effect" speed of light. :confused: How would you explain gravitational lensing?

The standard view of the space time fabric reveals mass can warp that fabric.

Hulse and Taylor were very specific in regards to the energy released from the rotation. So these gravitational waves take something with them and the photon is effected by it?

Strong energy congregations also warp space. If photon is held to localized event, then I guess you would have to understand the evolution to the Weber bar? :approve: ?
 
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  • #3
The energy of the waves is still the energy that Ligo predicts for them.
The amplitude would be smaller though.
 
  • #4
kurious said:
The energy of the waves is still the energy that Ligo predicts for them.
The amplitude would be smaller though.

Maybe I am confusing things here.

It is known that from predictions of GR that gravitational waves can go through anything.

In the late 1950s, Weber became intrigued by the relationship between gravitational theory and laboratory experiments. His book, General Relativity and Gravitational Radiation, was published in 1961, and his paper describing how to build a gravitational wave detector first appeared in 1969. Weber's first detector consisted of a freely suspended aluminium cylinder weighing a few tonnes. In the late 1960s and early 1970s, Weber announced that he had recorded simultaneous oscillations in detectors 1000 km apart, waves he believed originated from an astrophysical event. Many physicists were sceptical about the results, but these early experiments initiated research into gravitational waves that is still ongoing. Current gravitational wave experiments, such as the Laser Interferometer Gravitational Wave Observatory (LIGO) and Laser Interferometer Space Antenna (LISA), are descendants of Weber's original work.

http://physicsweb.org/article/news/4/10/4


The measurement is performed by bouncing high-power laser light beams back and forth between the test masses in each arm, and then interfering the two arms' beams with each other. The slight changes in test-mass distances throw the two arms' laser beams out of phase with each other, thereby disturbing their interference and revealing the form of the passing gravitational wave.

http://www.ligo.caltech.edu/LIGO_web/PR/scripts/facts.html


The larger the gravitational wave detector, the more sensitive it has the potential to be. LIGO employs a 4-foot diameter vacuum pipe arranged in the shape of an L with 4-kilometer (2.5-mile) arms. Since gravitational waves penetrate the Earth unimpeded, these installations need not be exposed to the sky and are entirely shielded in a concrete cover. At the vertex of the L, and at the end of each of its arms, are test masses that hang from wires and which are outfitted with mirror surfaces. These mirrors are the sensors of gravitational waves. The main building situated at the vertex serves as the observatory's control center and houses vacuum equipment, lasers, computers, and personnel. Ultrastable laser beams traversing the vacuum pipes measure the effect of gravitational waves on the test masses. Confident detection of the very weak waves predicted requires two installations vastly separated.

http://www.ligo.caltech.edu/LIGO_web/PR/scripts/facts.html
 
  • #5
The amplitude would be smaller because to have the same energy a wave of greater wavelength would need to have smaller peaks.These waves still pass through anything.

If Weber did detect those oscillations SIMULTANEOUSLY at 1000km separation
then he must have been right about their origin.

Why are the laser beams bounced back and forth so many times?
 
  • #6
kurious said:
Why are the laser beams bounced back and forth so many times?

As in post above


The slight changes in test-mass distances throw the two arms' laser beams out of phase with each other, thereby disturbing their interference and revealing the form of the passing gravitational wave.

There were difficulties with the bars in terms of resonance and problems of Earth's interference. I'd have to double check.

http://www.auriga.lnl.infn.it/auriga/guy_wave.jpg
 
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  • #7
Gravity waves squeeze masses together and pull them apart.
Are they two waves with different polarities?
 
  • #8
kurious said:
Why are the laser beams bounced back and forth so many times?

The change in distance between the two arms of the experiment is very slight, and therefore hard to detect. For this example, let's use a change with a negative value; a contraction which decreases the distance between the two arms. Let's assume that the original distance between the two arms is 1000. Never mind "1000 whats?", the unit of measure does not matter, but let's assume that in this unit of measure, "one" represents the amount of change that the sensor is capable of detecting. If we simply send a beam straight across from one arm to the other, and a gravity wave passing by decreases the distance between the two arms .1, then the total length of the laser was originally 1000, and it has been shortened by .1, which is too little to detect.

However, if we bounced a beam back and forth between the two arms about 100 times, the total length of the beam is 100,000. When the distance between the two arms is decreased, the laser takes a trip that is .1 shorter each time it crosses between the two arms. After 100 trips, the laser's total distance traveled is shortened by a factor of 10 units of measure, which is easily detectable.
 
  • #9
So the compression would last for at least 10^ - 5 seconds?
 
  • #10
kurious said:
Gravity waves squeeze masses together and pull them apart.
Are they two waves with different polarities?

Sometimes it is confusing thinking aboiut tipping lightcones, but to have considered the photon being held to the brane( an event that has happened) and to see that the gravitational waves are not limited? They can leave to the bulk.


This might not make sense, but if it does, maybe someone can answer from that perspective.

The clarification on flexiing tubes of LIGO helps clarify things greatly, but has not answered Glast :smile:
 
  • #11
It will be unsuccessful until then the essence of gravitation will be understood.
Application of concept " propagation" for gravitation is the main mistake.
Propagation and gravitation are an opposite consepts.
It is possible to apply them with attachment “anti” for one relative another.


Michael
 
  • #12
Michael F. Dmitriyev said:
Application of concept " propagation" for gravitation is the main mistake.
Michael

Let's focus on this then.

I might have some problems understanding from the persepctive Taylor's demonstrations?

From Mercury and the Daisey we learn to graduate to higher defintions with Taylor and Hulse.

The same phenomenon is more dramatically seen in the binary pulsar PSR 1913+16 where the periastron advances by about 4.2 degrees per year.

http://astrosun2.astro.cornell.edu/academics/courses//astro201/merc_adv.htm

This information had to be going somewhere? :smile:

Gravitatinal Radiation

Relativity predicts that the binary system will lose energy with time as orbital energy is converted to gravitational radiation.
 
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  • #13
sol2 said:
Let's focus on this then.

I might have some problems understanding from the persepctive Taylor's demonstrations?

From Mercury and the Daisey we learn to graduate to higher defintions with Taylor and Hulse.



This information had to be going somewhere? :smile:

Gravitatinal Radiation
In the first - it is a drama of bygone days (some millions or billions years).
You can’t to do the conclusions about this one today.
In the second- it is not bad to have an own opinion except quoting.


Michael
 
  • #14
It will be unsuccessful until then the essence of gravitation will be understood.
Application of concept " propagation" for gravitation is the main mistake.

It is obvious I am not comprehending something you are, why I set the stage for you to speak further. The question is still out there and I wanted to show that from this point I would need some clarifications from you to understand your statements.

Are you saying LIGO is failure because of the statements you are supplying?

So please go ahead and I'll add coments after. By what I respond, you will know if I understood.

Regards
 
  • #15
sol2 said:
It is obvious I am not comprehending something you are, why I set the stage for you to speak further. The question is still out there and I wanted to show that from this point I would need some clarifications from you to understand your statements.

Are you saying LIGO is failure because of the statements you are supplying?

So please go ahead and I'll add coments after. By what I respond, you will know if I understood.

Regards
I only want to say here, that experiments based on incorrect representation about an object of researches, can’t be successful.
I try to show my vision of this problem in my threads "Dimensions", “ What is a force? ” and others. Agree, I can’t begin all over again in each thread of a forum. Therefore I invite you and other participants there for the further discussion.

Michael
 
  • #16
kurious said:
LIGO may have failed to detect gravity waves because they move faster than light and so have a greater wavelength than expected and probably a lower amplitude too.

Gravity waves like light could be transverse waves that propagate through the ether at speed c.
However, an event such as supernova may cause longitudinal waves that propagate through the ether. It is likely that these will travel 10 times (or more) the speed of light and be undetectable by LIGO equipment.
 
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  • #17
wisp said:
Gravity waves like light could be transverse waves that propagate through the ether at speed c.
However, an event such as supernova may cause longitudinal waves that propagate through the ether. It is likely that these will travel 10 times (or more) the speed of light and be undetectable by LIGO equipment.
Gravitation does not need in traveling. It is an action itself. Note the speed of light is absolute and single speed existing at microlevel.

Michael
 
  • #18
Michael F. Dmitriyev said:
Gravitation does not need in traveling. It is an action itself. Note the speed of light is absolute and single speed existing at microlevel.

Michael

True. But if the gravitational effect changes because of some distant event, it does so at the speed of light, hence the gravity wave idea.
 
  • #19
wisp said:
True. But if the gravitational effect changes because of some distant event, it does so at the speed of light, hence the gravity wave idea.
Yes, locally gravitation attracts with a speed of light. This is a process of attraction itself. But globally there is no delay at all to start this attraction.
It exist always and everywhere.

Michael
 

FAQ: LIGO and speed of gravitational waves

How does LIGO detect gravitational waves?

LIGO (Laser Interferometer Gravitational-Wave Observatory) uses two 4-kilometer-long laser interferometers to detect tiny distortions in space-time caused by passing gravitational waves. These distortions are measured by comparing the travel time of laser beams between two perpendicular arms of the interferometer. If a gravitational wave passes through the detector, it will cause a slight difference in the travel time of the laser beams, which can be measured and detected.

How fast do gravitational waves travel?

According to Einstein's theory of general relativity, gravitational waves travel at the speed of light, which is approximately 299,792,458 meters per second. This means that gravitational waves have a speed of about 186,282 miles per second.

Are gravitational waves affected by the speed of their source?

No, according to the theory of general relativity, gravitational waves are not affected by the speed of their source. This means that whether the source of a gravitational wave is moving or not, the wave will still travel at the speed of light.

Can gravitational waves be used for communication?

No, gravitational waves cannot be used for communication. This is because they are extremely weak and can only be detected by highly sensitive instruments like LIGO. Also, gravitational waves are not able to carry information in the same way that electromagnetic waves (such as radio waves) can.

How does the speed of gravitational waves compare to the speed of light?

The speed of gravitational waves is equal to the speed of light, according to the theory of general relativity. This means that both travel at approximately 299,792,458 meters per second. However, the two types of waves have different properties and are used to study different phenomena in the universe.

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