Plans for near future of E@H ?

Tom*
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Its hard to wait when they

Its hard to wait when they might need our help to verify a posible

detection of gravity waves at the LIGO.:-)

http://www.msn.com/en-us/news/technology/scientists-struggle-to-stay-grounded-after-possible-gravitational-wave-signal/ar-CCpXnV?li=BBnbfcL&ocid=iehp

Mike Hewson
Mike Hewson
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Oh great, rumor again

Oh great, rumor again .....

Quote:
Krauss said he was 60% confident that the rumour was true, but said he would have to see the scientists’ data before drawing any conclusions about whether the signal was genuine or not.


Yes. The data could be relevant. You certainly couldn't rule out the possibility that knowledge of the data plays a role in making scientific claims. This will morph into a factoid by sunset.

Quote:
“They’ve done studies, you know. 60 percent of the time, it works every time.†— Brian Fantana { Anchorman }


I'll stick my neck right out here and assert that tweeting is not a LIGO collaborative mechanism.

Mike.

I have made this letter longer than usual because I lack the time to make it shorter. Blaise Pascal

Bernd Machenschalk
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The pipeline that runs on

The pipeline that runs on Einstein@Home will probably not be the first to detect or verify gravitational waves. The sources that E@H is aiming to detect produce the faintest type of gravitational waves, the advantage being is that the sensitivity is limited almost exclusively by the amount of data that could be collected and processed, i.e. by "observation time" and computing power. This means that that we need a lot of time taking data first, and then quite a bit to analyze that completely.

"extremely violent events" (as memtioned in the article) are presumably rare, but the gravitational waves emitted from these are much "louder", shorter and easier to detect, even with much less computing power than what Einstein@Home offers. This will probably be the type of gravitational waves that will be detected (and verified) first, independently of Einstein@Home.

BM

BM

Gary Roberts
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This is the bit that made me

This is the bit that made me groan

Quote:
Gravitational waves are generated in the most exotic, strange locations in nature, such as at the edge of black holes at the beginning of time. We are pretty certain they exist, but we’ve not been able to use them to probe the universe.


My immediate questions are:-

1. Does "beginning of time" refer to what we call the big bang?

2. What is referred to by "pretty certain they exist". Black holes -- or GW??

3. If black holes, how many existed at the "beginning of time"? I would have thought zero but am I wrong??

4. How long after the big bang was it when the first black holes could have been formed?? I imagined a big enough star had to fire up, burn and die violently to get a black hole - perhaps I'm wrong here too??

5. If GW was referred to in "certain they exist", the last sentence makes more sense. Otherwise how do you use a black hole to "probe the universe"??

My immediate reaction to needing clarification, is that stories like this are really just click bait. A tantalising headline pretty much devoid of useful content.

I have a question for Bernd :-). Have there been any "extremely violent events" since advanced LIGO data taking commenced? I would think the veracity of the "rumours" floating around might be directly proportional to some high multiple of the number of such events :-). Wouldn't it just be ironic if (by good luck) no such events occurred before the first available data was distributed here :-).

We could just get lucky :-).

Cheers,
Gary.

Mike Hewson
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RE: This is the bit that

Quote:
This is the bit that made me groan


I groaned rather more .... ;-)

Quote:
Quote:
Gravitational waves are generated in the most exotic, strange locations in nature, such as at the edge of black holes at the beginning of time. We are pretty certain they exist, but we’ve not been able to use them to probe the universe.

My immediate questions are:-

1. Does "beginning of time" refer to what we call the big bang?


May as well. ;-)

Quote:
2. What is referred to by "pretty certain they exist". Black holes -- or GW??


Both. Gravitational theory as current validated would be consistent if so.

Quote:
3. If black holes, how many existed at the "beginning of time"? I would have thought zero but am I wrong??


Yes indeed. Density = matter per volume is the key to making BH's.

Quote:
4. How long after the big bang was it when the first black holes could have been formed?? I imagined a big enough star had to fire up, burn and die violently to get a black hole - perhaps I'm wrong here too??


There are ( probably ) black holes other than 'stellar' ie. can circumstances exist by any means ? Collapsing stars are one way to get the massive density required.

Quote:
5. If GW was referred to in "certain they exist", the last sentence makes more sense. Otherwise how do you use a black hole to "probe the universe"??


For "probe" read : use observation to know more than you would otherwise. Scientific method etc.

Quote:
My immediate reaction to needing clarification, is that stories like this are really just click bait. A tantalising headline pretty much devoid of useful content.


Slow news day probably. Need to keep the advertising revenue up etc. There is no scientific content to the story's origin, as stated the data remains unseen by Mr Krauss because he is not privy to it. What has been generated is a sociology remark ie. the ants are busy so they must have found something to eat. There could have been a test injection : a double blind technique to test the processes of the collaboration. Or whatever.

NB. Mr Krause's comments are quite correct regardless of factual outcome ie. it is true that there is a rumor ( even if there wasn't one, there will be now ). We will get denial of the rumor validating a truth next .....

There's an old ( Zen ? ) saying : don't confuse the Moon with the finger that points at it. :-0

Cheers, Mike.

( edit ) That is, look at the sky and not the finger. In this case I'll wait for comment from one who actually knows something.

I have made this letter longer than usual because I lack the time to make it shorter. Blaise Pascal

Bernd Machenschalk
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RE: Have there been any

Quote:
Have there been any "extremely violent events" since advanced LIGO data taking commenced? [...] Wouldn't it just be ironic if (by good luck) no such events occurred before the first available data was distributed here

Well, the real irony is that we only know of such an event from the gravitational waves we detect of it (unless the event is pretty near and emits electromagnetic waves as well so we can actually see it - which, however, is much more rare).

Statistics, however, is against Einstein@Home here: "initial" LIGO would have seen such an event every few years if it happened to be online at that time, so we had to be pretty lucky. With the much improved sensitivity of "advanced" LIGO we hope to see such an event much more frequently.

BM

BM

AgentB
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RE: RE: Have there been

Quote:
Quote:
Have there been any "extremely violent events" since advanced LIGO data taking commenced? [...] Wouldn't it just be ironic if (by good luck) no such events occurred before the first available data was distributed here

Well, the real irony is that we only know of such an event from the gravitational waves we detect of it (unless the event is pretty near and emits electromagnetic waves as well so we can actually see it - which, however, is much more rare).

If an event is detected, how accurate will LIGO be at pinpointing it's position? Put in layman's terms is LIGO more like an ear trumpet (we heard a noise over there), or Galileo's first telescope (we see amazing details)?

Mike Hewson
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RE: If an event is

Quote:
If an event is detected, how accurate will LIGO be at pinpointing it's position? Put in layman's terms is LIGO more like an ear trumpet (we heard a noise over there), or Galileo's first telescope (we see amazing details)?


The ear trumpet. A given interferometer has this antenna function ( signal sensitivity vs direction ) :

... the 'average' on the right graphic has some 'puckers on the peanut' where it is deaf to signals from those directions where no differential length change in the arms is generated by the passing GW ( hence no change in photon relative phase b/w arms ). You could legitimately call this an omnidirectional pattern. So a single interferometer is awful in disambiguating direction ( annoyingly the highest precision in directions is where you detect nothing !)

This is why there is a worldwide network of receivers. So some wave arrives at the Earth from some source direction in the sky. It travels at a finite speed - we expect that to be the speed of light - and so will not arrive at any inteferometer simultaneously with any other. There will be some time sequence of detections of the same waveform across the network. Now we know to high degree the light travel time b/w intererometers ( because we built them on a well surveyed planet ) and so one can solve for sky position(s).

The question now becomes how well we can locate source direction. In theory at least three interferometers will be sufficient to fix, but that's a loose generality. One reason why a southern hemisphere inteferometer was desired ( the LIGO in India is being built ) was to cover the northern hemisphere 'deaf' regions. But like all receivers of wave-like phenomena you are still stuck with instrument aperture and signal wavelength determining the angular resolution of the sky solution(s). The best aperture we can get is the earth's diameter and the wavelength depends on the source mechanisms that generates it. Hence other ideas like LISA.

{ AFAIK the Holy Grail here would be firm knowledge/detection of different signal types ( GW + EM ) from the same physical object. Interestingly I don't think the relatively poor sky resolution of GW compared to EM will be necessarily insurmountable here. If you listen to a rock band the overall tune is the same though expressed by many instruments in detail. For example if a time series pattern of general signal features is determined by both a GW recording and an EM recording then it would be reasonable to attribute them to nearby/co-located processes. Suppose I burgle your house : you may hear a bump in the night as I trip over your cat and you will see light play all over the wall as I also drop my torch. :-) }

Cheers, Mike

I have made this letter longer than usual because I lack the time to make it shorter. Blaise Pascal

AgentB
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RE: { AFAIK the Holy Grail

Quote:
{ AFAIK the Holy Grail here would be firm knowledge/detection of different signal types ( GW + EM ) from the same physical object.

Thanks Mike that explains a few things, we are overdue a nearby supernova, hopefully we'll also get a few neutrinos to waken the neighbours.

Mike Hewson
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RE: RE: { AFAIK the Holy

Quote:
Quote:
{ AFAIK the Holy Grail here would be firm knowledge/detection of different signal types ( GW + EM ) from the same physical object.

Thanks Mike that explains a few things, we are overdue a nearby supernova, hopefully we'll also get a few neutrinos to waken the neighbours.


Yes, what a good idea. I could use my neutrino hover board .... surf the district upon the neutrino back wash ...

Cheers, Mike.

I have made this letter longer than usual because I lack the time to make it shorter. Blaise Pascal

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