Gravitational/Scalar Waves

[Ant Sinclair]

 

 

A little while back on most news channels there were big announcements as regards Gravitational Waves.

The team collaboration that was mentioned being called Ligo.

The team used a Laser Interferometer to measure these gravitational waves.

Obviously to those with an interest in cosmology many questions arise when contemplating gravitational waves such as;

Which direction did they come from, what's their source, what frequencies are they, are the waves pure ie no distortive ripples riding on them and the list goes on, but, one question that popped into my imagination when thinking about the waves and has intrigued the most, was - did the gravitational waves pass through us - Or - did we pass through them???

 

Not a single I On it's own in there Strange - don't want you getting paranoid now do I

[swansont]

They passed through us. Since gravitational waves travel at c, they have no rest frame.

[Ant Sinclair]

They passed through us. Since gravitational waves travel at c, they have no rest frame.

 

That's a very confident statement swansont, don't waves 'travel' in a direction, doesn't our Solar System, Galaxy even Super Cluster travel at significant velocities through the 'void'? Edited April 10, 2017 by Ant Sinclair

[swansont]

That's a very confident statement swansont, don't waves 'travel' in a direction, doesn't our Solar System, Galaxy even Super Cluster travel at significant velocities through the 'void'?

 

 

As I stated, anything traveling at c cannot have a rest frame. There is no physics that one can use to say the wave was sitting there and we passed through it. No matter our speed relative to something else, the waves are always moving at c. To the extent that we can consider ourselves in an inertial frame, we can analyze everything as if we were at rest.

[Ant Sinclair]

As I stated, anything traveling at c cannot have a rest frame. There is no physics that one can use to say the wave was sitting there and we passed through it. No matter our speed relative to something else, the waves are always moving at c. To the extent that we can consider ourselves in an inertial frame, we can analyze everything as if we were at rest.

If, if there were an electromagnetic wave of say 900 million metres in length, and this wave was travelling towards Earth and there were detectors on standby, from the moment it reached us, how long would the detectors detect the wave for?

Edited April 10, 2017 by Ant Sinclair

[swansont]

If, if there were an electromagnetic wave of say 900 million metres in length, and this wave was travelling towards Earth and there were detectors on standby, from the moment it reached us, how long would the detectors detect the wave for?

 

 

Approximately 1 second

[Strange]

A little while back on most news channels there were big announcements as regards Gravitational Waves.

The team collaboration that was mentioned being called Ligo.

The team used a Laser Interferometer to measure these gravitational waves.

Obviously to those with an interest in cosmology many questions arise when contemplating gravitational waves such as;

Which direction did they come from, what's their source, what frequencies are they, are the waves pure ie no distortive ripples riding on them and the list goes on, but, one question that popped into my imagination when thinking about the waves and has intrigued the most, was - did the gravitational waves pass through us - Or - did we pass through them???

 

 

Here is an overview of the first gravitational wave detection: http://stuver.blogspot.it/2016/02/LIGO-FirstDetection.html

And of the second: http://stuver.blogspot.it/2016/06/GW151226.html

 

 

Direction: because there were only two detectors, they could only get an approximate direction. In future this will be determined more accurately as more detectors start running.

http://www.thephysicsmill.com/2016/03/06/direction-ligos-gravitational-waves/

 

Source: the merging of two black holes

 

Frequencies: for the first detection, they rose to a peak of about 250 Hz (that is the rate at which the two black holes were orbiting one another before they merged).

 

Pure: because the signal is so weak, it is accompanied by a lot of noise. I think that the raw data doesn't look very "pure".

 

And, yes, the gravitational waves pass through everything, causing a slight stretching and squishing. This is so small it is barely detectable. More here:

http://stuver.blogspot.it/2012/07/journey-of-gravitational-wave-i-gws.html

http://stuver.blogspot.it/2012/06/q-what-would-gravitational-wave-feel.html

 

And more detail than you could ever need here: https://cplberry.com/2016/02/23/gw150914-the-papers/

[Ant Sinclair]

Approximately 1 second

I would have approximated just over three seconds if it were travelling at C, but to continue, if I remember correctly hadn't Ligo been 'waiting' for these waves to arrive here at Earth, once the wait was over, ie they arrived, how long were they detected for, and if any, when are more expected?

[Strange]

I would have approximated just over three seconds if it were travelling at C, but to continue, if I remember correctly hadn't Ligo been 'waiting' for these waves to arrive here at Earth, once the wait was over, ie they arrived, how long were they detected for, and if any, when are more expected?

 

 

The pulse last about 1/10th of a second. They took about 1.4 billion years to get here.

 

They have already detected at least one more event. I think it is too early to say how frequent such events are.

[Mordred]

Far more common than we are able to detect

[Ant Sinclair]

The pulse last about 1/10th of a second. They took about 1.4 billion years to get here.

 

They have already detected at least one more event. I think it is too early to say how frequent such events are.

Strange, when I replied to swansont I quoted his post so HE would be notified that I had replied to HIM, is it not considered behaving ignorant 'chipping' like You just Have Again?

[swansont]

I would have approximated just over three seconds if it were travelling at C, but to continue, if I remember correctly hadn't Ligo been 'waiting' for these waves to arrive here at Earth, once the wait was over, ie they arrived, how long were they detected for, and if any, when are more expected?

 

 

Sorry, early morning (pre-caffeine) math. You are correct. ~3 seconds.

 

The LIGO chirp was a few tenths of a second

https://www.ligo.caltech.edu/image/ligo20160211a

 

We don't know when the next signal will arrive. Predicting when two distant (and perhaps invisible) objects will collide is not currently possible.

Strange, when I replied to swansont I quoted his post so HE would be notified that I had replied to HIM, is it not considered behaving ignorant 'chipping' like You just Have Again?

 

 

You asked a question of a factual nature. It's fair game for anyone with access to such facts to respond.

[Ant Sinclair]

Sorry, early morning (pre-caffeine) math. You are correct. ~3 seconds.

 

The LIGO chirp was a few tenths of a second

https://www.ligo.caltech.edu/image/ligo20160211a

 

We don't know when the next signal will arrive. Predicting when two distant (and perhaps invisible) objects will collide is not currently possible.

 

 

You asked a question of a factual nature. It's fair game for anyone with access to such facts to respond.

As far as your last quote from your last post swansont I don't agree, when I'm in meetings/discussions if a particular person is addressed normally folk wait for that particular to respond, you must do things differently in the US.

 

As regards your other quotes thank you, having just looked at your link it shows the 'gravitational' wave lasted approximately 0.45S, with a 'Strain' scale of +1 to -1, what exactly in simple terms is the 'Strain' indicating?

[swansont]

As far as your last quote from your last post swansont I don't agree, when I'm in meetings/discussions if a particular person is addressed normally folk wait for that particular to respond, you must do things differently in the US.

 

As regards your other quotes thank you, having just looked at your link it shows the 'gravitational' wave lasted approximately 0.45S, with a 'Strain' scale of +1 to -1, what exactly in simple terms is the 'Strain' indicating?

 

 

the scale is -1 to 1 x 10^-21

 

It's the fractional change in length, ∆L/L

[Phi for All]

As far as your last quote from your last post swansont I don't agree, when I'm in meetings/discussions if a particular person is addressed normally folk wait for that particular to respond, you must do things differently in the US.

 

 

!

Moderator Note

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No more comments about the participation of others. They are perfectly free to engage in discussion as long as they obey the rules.

 

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[Velocity_Boy]

Ironically I just came across this old article in a magazine a couple weeks ago. And I just found an online version of it. I think it speaks of this topic very accessible and interestingly. Seems we might finally be getting a handle on what gravity is really comprised of, instead of just having to rely on that old worn placeholder term "gravitrons." Which we really didn't even know what they were comprised of or why or how. Just like we are now with Dark Energy. No clue. Just know it's there. LOL

 

Anyway...you might like this...........

 

https://cosmosmagazine.com/physics/measuring-gravity-have-we-finally-cracked-it

[Strange]

Ironically I just came across this old article in a magazine a couple weeks ago. And I just found an online version of it. I think it speaks of this topic very accessible and interestingly. Seems we might finally be getting a handle on what gravity is really comprised of, instead of just having to rely on that old worn placeholder term "gravitrons." Which we really didn't even know what they were comprised of or why or how. Just like we are now with Dark Energy. No clue. Just know it's there. LOL

 

Anyway...you might like this...........

 

https://cosmosmagazine.com/physics/measuring-gravity-have-we-finally-cracked-it

 

 

Interesting article. I hadn't come across this before (but I bet swansont has). It does hint at possibilities for new physics. But it seems somewhat off topic ...

[imatfaal]

Ironically I just came across this old article in a magazine a couple weeks ago. And I just found an online version of it. I think it speaks of this topic very accessible and interestingly. Seems we might finally be getting a handle on what gravity is really comprised of, instead of just having to rely on that old worn placeholder term "gravitrons." Which we really didn't even know what they were comprised of or why or how. Just like we are now with Dark Energy. No clue. Just know it's there. LOL

 

Anyway...you might like this...........

 

https://cosmosmagazine.com/physics/measuring-gravity-have-we-finally-cracked-it

 

No you have misunderstood the article. This article is regarding metrology - the science of measurement which is very interesting and can to lead to deeper insight but is not explicitly concerned with the more theoretical/ontological sides of the pursuit.

 

The Graviton is not a placeholder - it is a prediction of one of the most accurate models we have; it's just we haven't been able to identify one yet. We know an incredible amount about gravity and whilst we are still missing a quantum theory of gravity - we must not despair and claim we know nothing. GR is perhaps the pinnacle of early 20th century thinking - it is a set of work that is still being expanded upon and we have just managed to start proving some more parts of it; the existence of gravitational waves being the most recent.

 

G is just a multiplier really - it is smallish because our units are anthropocentric and cause it to be that way; there is no deep significance in 6.67e-11 m3 kg-1 s-2. In planck units it is 1. Only the dimensionless units can really be interesting in their magnitude - ~1/137 (fine structure constant) is the prime example

[Ant Sinclair]

Attached is a graph from Caltech's website showing the 'gravitational wave' event.

The article says the frequency cycled from around 35Hz to approximately 250Hz.

The second graph from Georgia Tech shows the event to last about 0.2S.

 

What significance does the event duration identify if any?

[Velocity_Boy]

 

 

Interesting article. I hadn't come across this before (but I bet swansont has). It does hint at possibilities for new physics. But it seems somewhat off topic ...

 

 

Yeah, thanks. And, yeah, sorry (lol) it IS a bit off-topic down here at this portion of the thread. I posted it after reading the OP too quickly and thinking it concerned the nature of Gravity here on Earth. Instead of a detected boradscast or otherwise emitted pulse. I have a bad habit of reading posts too quicly sometimes before responding. Will try to watch that!

Edited April 11, 2017 by Velocity_Boy

[Strange]

Attached is a graph from Caltech's website showing the 'gravitational wave' event.

The article says the frequency cycled from around 35Hz to approximately 250Hz.

The second graph from Georgia Tech shows the event to last about 0.2S.

 

What significance does the event duration identify if any?

 

The event duration (and the frequencies involved) is what allows the source to be identified as the "inspiral" and merger of two black holes. The frequencies and duration are dependent on the masses of the black holes. The final "ring down" phase after the peak is defined by the mass of the resulting single black hole. In this way, the total energy radiated away as gravitational waves can be estimated.

 

The top half of this image shows the relationship between the black holes and the waveform:

[Ant Sinclair]

The event duration (and the frequencies involved) is what allows the source to be identified as the "inspiral" and merger of two black holes. The frequencies and duration are dependent on the masses of the black holes. The final "ring down" phase after the peak is defined by the mass of the resulting single black hole. In this way, the total energy radiated away as gravitational waves can be estimated. The top half of this image shows the relationship between the black holes and the waveform:

 

Wouldn't the actual event last a relatively long time?

How does that transpose into 0.2S?

[imatfaal]

Wouldn't the actual event last a relatively long time?

How does that transpose into 0.2S?

 

The entire event lasts an unimaginable time (billions of years) - but the final brutally apocalyptic inspiral/ringdown is short (fractions of a second). It is the tremendous amount of energy over such a short time (practically nothing on a cosmological scale) that means we can detect the event. The black holes which merged were estimated to have been formed over 10 billion years ago - I would assume they have been orbiting closer and closer ever since. During that last 20 milliseconds the event was pumping out more energy than all the starlight of all the observable universe! So, to summarize, it is a slow drawn out event with an incredibly explosive finale - our instruments are only sensitive enough to notice the final part of the final part

[Ant Sinclair]

The entire event lasts an unimaginable time (billions of years) - but the final brutally apocalyptic inspiral/ringdown is short (fractions of a second). It is the tremendous amount of energy over such a short time (practically nothing on a cosmological scale) that means we can detect the event. The black holes which merged were estimated to have been formed over 10 billion years ago - I would assume they have been orbiting closer and closer ever since. During that last 20 milliseconds the event was pumping out more energy than all the starlight of all the observable universe! So, to summarize, it is a slow drawn out event with an incredibly explosive finale - our instruments are only sensitive enough to notice the final part of the final part

I like the description, it's quaint

 

From reading of Mr Hawkins and his predecessors our thoughts of black holes seem to change with time.

Would you agree it's just one proposed mechanism and may or not be correct?

 

I wonder why 0.2S, when I look at the graph of Ligo's first event it looks closer to about 0.17S, speaking of Ligo's first event leads to it's second captured event that looks nothing like the first, the one we've discussed so far.

[imatfaal]

who is Mr. Hawkins? Please don't say you mean Dr. or Professor Stephen Hawking; accuracy is important and so is politeness.

 

And our ideas and understanding of extreme phenomena which are at high cosmological distances obviously change with each new observation - but I see no huge volte-face.

 

Eyeballing a graph is not a great way to decide on the timing of an event - but frankly who cares; we measured an event and it looked just as we expected for that sort of scenario.

 

The second event was different I believe in that one of the blackholes had considerable spin on its axis at merger and they were both smaller so the detectable finale was spread out over a longer period