LIGO gravitational wave announcement

[query grind]

But everyone has access to the information obtained using it.


To anyone with the necessary intellectual capacity and the willingness to put in the time and effort required to understand the science, yes.

Oh well, that's a relief.

 

[query grind]

When I was a PhD student someone asked one of my fellow students who was constructing a knock-out mouse (a mouse with a gene deactivated): "What will you do for your PhD if your mouse has no phenotype" [ie no noticeably biological difference from the wild-type mouse].

The answer is, of course, you make sure your mouse has a god-damn phenotype - you haven't spent 3 year just to produce a mouse that is identical to the unmutated version.

So has the Physics community ever massively over-invested in a big ticket project? Some multi-billion dollar project that failed to met expectations?

 

[Pixel42]

The point of the experiment was surely to find out what effect knocking out a gene has. The fact that has no effect, if indeed it does not, is just as interesting - possibly more so - than any effect it does have.

ETA: Experiments that failed to produce the expected results have historically been the most interesting. The Michaelson-Morley experiment and the project to measure how quickly the acceleration of the universe was decreasing in the 1990s (which actually established that it was increasing) spring immediately to mind.

 

[SusanB-M1]

Anyone here NOT running seti@home since they had a PC?

I did have it years ago, but it didn't get on with my Super|Nova software, I'm sorry to say.

 

[query grind]

The point of the experiment was surely to find out what effect knocking out a gene has. The fact that has no effect, if indeed it does not, is just as interesting - possibly more so - than any effect it does have.

No, the point of the experiment was to produce an interesting paper and get a post doc position in a lab with an excellent track record of obtaining grants.

Not trying to derail, but does the pressure ever come on the physics community to justify a multibillion investment and would there ever be an incentive to ham up a less than unequivocal result?

 

[Pixel42]

No, the point of the experiment was to produce an interesting paper and get a post doc position in a lab with an excellent track record of obtaining grants.

And I'm saying that a paper which describes how knocking out a gene has no effect is an interesting paper, especially if that was not the expected result. Possibly more interesting than one that describes a result which was expected.

Not trying to derail, but does the pressure ever come on the physics community to justify a multibillion investment and would there ever be an incentive to ham up a less than unequivocal result?

The point of such experiments to find something out. If the result is not what was expected, that's often even more exciting than if it was. See my ETA to my previous post.

 

[Lukraak_Sisser]

No, the point of the experiment was to produce an interesting paper and get a post doc position in a lab with an excellent track record of obtaining grants.

Not trying to derail, but does the pressure ever come on the physics community to justify a multibillion investment and would there ever be an incentive to ham up a less than unequivocal result?

As someone who has worked in that field, Pixel42 hits the nail on the head. Experiments are done to determine what a gene does. Knocking it out and NOT getting a phenotype can produce quite interesting papers.
Faking a phenotype on the other hand can produce quite short careers once your successor starts working with it and has an instant 'my predecessor was wrong paper'

As for the usual 'What use is this right now' question. That is not why fundamental science is done. If that is your interest, go to industrial science. Fundamental science is humanities non-ending quest to determine the answer to the question 'Why?'. And sometime that leads to extremely useful practical science, often a century or so later.

 

[MaartenVergu]

"ripples in the fabric of space and time." Nice words, but no human being can really grasp what it means. No scientist can grasp: a big bang, spacetime, quantumphysics, singularities etc. You think you understand these things because you gave it a fancy name. It is beyond our human capacity to actually understand what's going on in this world on these levels.

 

[query grind]

As someone who has worked in that field, Pixel42 hits the nail on the head. Experiments are done to determine what a gene does. Knocking it out and NOT getting a phenotype can produce quite interesting papers.
Faking a phenotype on the other hand can produce quite short careers once your successor starts working with it and has an instant 'my predecessor was wrong paper'

Can you link to any of these interesting papers?
It is fairly hard to prove scientific fraud, mostly those who get caught are careless or use photoshop (pretty much the same thing)
The only one I know of off the top of my head is Sphingosine-1-phosphate receptor-2 knock-outs.
A Japanese group and an American group both published a knock-out of these gene about the same time. The Japanese group was shown to have used photoshop to create their results and were forced to retract - I presume the PhD student didn't have much of a career after that. The American group reported very similar results and didn't use photoshop.

I know nothing about physics - which is why I was interested in Pixel's opinion of whether they might be susceptible to inflating results. She says absolutely not and I certainly have no expertise to dispute her.

I do know something about life sciences - and anyone is who suggests it isn't packed with non-reproducible results is delusional.

 

[Pixel42]

I know nothing about physics - which is why I was interested in Pixel's opinion of whether they might be susceptible to inflating results. She says absolutely not and I certainly have no expertise to dispute her.

I certainly wouldn't say "absolutely not", I'm sure there are physicists who are so wedded to their pet theory they might be tempted to exaggerate or misinterpret - even fabricate - their results. But where large scale experiments are concerned the intention is to find answers to specific questions; whatever the answer turns out to be, the experiment was successful.

So for example if the LHC had finished its search for the Higgs Boson without actually finding it, that experiment would have been successful. The answer, whilst not the expected one, would have galvanised physicists to find out what was wrong with the models that predicted the existence of the Higgs boson. Indeed when the LHC was first fired up I read some interviews with physicists who declared they would be more excited by a negative result than a positive one. Likewise if LIGO had run for decades and never detected gravitational waves that would also have been an exciting result, because it would have meant that there was something seriously wrong with the General Theory of Relativity.

 

[Lukraak_Sisser]

Can you link to any of these interesting papers?
It is fairly hard to prove scientific fraud, mostly those who get caught are careless or use photoshop (pretty much the same thing)
The only one I know of off the top of my head is Sphingosine-1-phosphate receptor-2 knock-outs.
A Japanese group and an American group both published a knock-out of these gene about the same time. The Japanese group was shown to have used photoshop to create their results and were forced to retract - I presume the PhD student didn't have much of a career after that. The American group reported very similar results and didn't use photoshop.

I know nothing about physics - which is why I was interested in Pixel's opinion of whether they might be susceptible to inflating results. She says absolutely not and I certainly have no expertise to dispute her.

I do know something about life sciences - and anyone is who suggests it isn't packed with non-reproducible results is delusional.

The ones of the top of my head are ones I worked on myself, and I do not like to link on a public forum in order to maintain (maybe the illusion) that I can retain some anonymity online.
I can point you in a direction though. I worked on yeast genetics, rRNA biosynthesis in particular. About half the proteins in the rRNA synthesis complexes can be knocked out without a direct phenotype. A pubmed search on the current reviews about the subject and the subsequent literature should give you all the examples you'd like.
In a similar vein, the psaE protein in the cyanobacterial photosystem can be removed without a physical phenotype as other proteins get upregulated to compensate.

 

[thedopefishlives]

"ripples in the fabric of space and time." Nice words, but no human being can really grasp what it means. No scientist can grasp: a big bang, spacetime, quantumphysics, singularities etc. You think you understand these things because you gave it a fancy name. It is beyond our human capacity to actually understand what's going on in this world on these levels.

I'm sorry, is there a reason why we can't? As far as I'm aware, we actually have a pretty good grasp of what time is, and how space-time works.

 

[slyjoe]

That's exactly right. In fact, you can see both effects in that image: first the time-of-flight alone (which is measured very accurately) constrains the source to a narrow 360º ring. On top of that, they have the difference in intensities at the two sites, which (less accurately) tells you at what angle the wave passed through each detector, and that rules out a subset of the TOF-compatible ring.

I agree - rwguinn, ben_m and Cl1mh4224rd got what I was getting at. There aren't a lot of laymen descriptions of how the arms and detectors work; remember that the detector (the point) has inputs from the two arms. A fair description:

...Because light is a wave, the two laser beams combine to make an interference pattern of bright and dark areas, or “fringes,” at that light sensor. Analyze the fringes, and you can tell how far each light wave traveled to cover the distance between the mirror and the sensor. More importantly, you can tell if that distance is changing over time. If a gravitational wave passes by, one arm of the observatory’s “L” should be stretched while the other gets squeezed, producing a telltale change in the fringe pattern.

http://www.pbs.org/wgbh/nova/next/physics/advanced-ligo/

 

[Elind]

That's exactly right. In fact, you can see both effects in that image: first the time-of-flight alone (which is measured very accurately) constrains the source to a narrow 360º ring. On top of that, they have the difference in intensities at the two sites, which (less accurately) tells you at what angle the wave passed through each detector, and that rules out a subset of the TOF-compatible ring.

I don't know how or if the two arms can give a direction indication, but surely "intensity" difference must be a measurement artifact. How can a gravity wave that has traveled for a billion light years or more be weakened by a few hundred miles of travel?

 

[ctamblyn]

I think ben m is referring to the intensity difference due the fact that the sensitivity of each detector varies with direction (see here for a diagram), and the two detectors (the Livingston Observatory and the Hanford Observatory) have different orientations in space, being some 3000 km apart.

 

[Cl1mh4224rd]

"ripples in the fabric of space and time." Nice words, but no human being can really grasp what it means. No scientist can grasp: a big bang, spacetime, quantumphysics, singularities etc. You think you understand these things because you gave it a fancy name. It is beyond our human capacity to actually understand what's going on in this world on these levels.

Don't project.

 

[query grind]

The ones of the top of my head are ones I worked on myself, and I do not like to link on a public forum in order to maintain (maybe the illusion) that I can retain some anonymity online.
I can point you in a direction though. I worked on yeast genetics, rRNA biosynthesis in particular. About half the proteins in the rRNA synthesis complexes can be knocked out without a direct phenotype. A pubmed search on the current reviews about the subject and the subsequent literature should give you all the examples you'd like.
In a similar vein, the psaE protein in the cyanobacterial photosystem can be removed without a physical phenotype as other proteins get upregulated to compensate.

Neither of which are mice and the process of knocking-out a gene is a lot simpler. There is nothing surprising about knocking-out a gene and showing no phenotype, just when the investment is high it is less rewarding to report it.

The point I am asserting is the bigger the investment in time or money, the greater the psychological pressure to come up with positive results.

So in the physics area are there areas of big investments coming up with "exciting" negative results?

 

[Elind]

I think ben m is referring to the intensity difference due the fact that the sensitivity of each detector varies with direction (see here for a diagram), and the two detectors (the Livingston Observatory and the Hanford Observatory) have different orientations in space, being some 3000 km apart.

I see. Thanks

Has there been anything on what the wavelength of such an event is? My point is that if it is far larger than the detector then any expansion/contraction of space would seem to be more or less the same in all dimensions.

 

[RecoveringYuppy]

I see. Thanks

Has there been anything on what the wavelength of such an event is? My point is that if it is far larger than the detector then any expansion/contraction of space would seem to be more or less the same in all dimensions.

LIGO is senstiive to wavelengths in the range ~100 to ~1000 KM IIRC, if that is what you're asking.

 

[Michel H]

I see. Thanks

Has there been anything on what the wavelength of such an event is? My point is that if it is far larger than the detector then any expansion/contraction of space would seem to be more or less the same in all dimensions.

The wavelength is much larger than the detector size, but this doesn't mean that orientation is irrelevant. Think about an incident (polarized) long wavelength electromagnetic wave (instead of a gravitational wave), and assume your linear antenna is perpendicular to the electric field of this e-m wave, you get no signal. Now assume the antenna is parallel to the E-field: you can get a signal, even if your antenna is small compared to the wavelenth (think e.g. of a portable radio receiver receiving in the medium wave band at 360 m https://en.wikipedia.org/wiki/Medium_wave).