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I'm am really confused as to how Martin Rees has written such a poor article. He's bloody Astronomer Royal. I suspect a ghostwriter.

a) Gravitational waves do NOT "shake the mirrors". They make spacetime contract in orthogonal directions around and within the beam tube (and of course elsewhere) thus causing the light to travel a tiny bit further in the tube, thus causing interference by moving the two beams out of phase.

b) As I posted the other day - what about Virgo? What about GEO600? I feel really sorry for the scientists who've spent decades working on this as part of a global collaboration to now have LIGO take all of the credit for this discovery.




Physicist here. You're off base.

a) Saying "gravitational waves don't shake the mirrors, it's length contraction" is as confused as saying "the Sun doesn't pull on the Earth, it bends spacetime around it". In each case, you're describing the same mechanism with different words. The whole point of the equivalence principle is that gravitational forces are equivalent to changing the local inertial frame. Ultimately, the Einstein field equations are what they are, but both types of description in words are correct (and inexact).

b) Virgo and GEO600 didn't detect gravitational waves. LIGO did.


Just a bit more background on (b) - from the paper in Phys. Rev. Lett. (https://dcc.ligo.org/LIGO-P150914/public):

"Only the LIGO detectors were observing at the time of GW150914. The Virgo detector was being upgraded, and GEO 600, though not sufficiently sensitive to detect this event, was operating but not in observational mode."

The GW150914 event was the strongest one observed in the period LIGO was operating:

"Detected with ηc = 20.0, GW150914 is the strongest event of the entire search."

So, the strongest event happened to occur when the other detectors were not running.


Also a physicist. I may have let my passion for what the guys at virgo have been up to bias my judgment - visited years ago when they were commissioning the place, and had a long, long discussion about the problems they overcame, mostly around optics and noise, which they shared solutions for with the ligo folks. Now the paper is out I've untwisted my knickers as I can see they've cited the teams around the globe. The media up until that point kinda gave the impression it was a sole effort.

Giant's shoulders and all that.


Re b): Virgo will hopefully soon, and I think they did give appropriate credits to GEO600 in the press conference.


Blame the sub-editors at the Telegraph, what's left of them (or more accurately it's CE Murdoch MacLennan and the weirdo Barclay Brothers that own it). That paper has been on a gradual downwards trajectory in quality for a long time now, and it's rare thing that it produces anything resembling actual journalism.

It's gradually morphed from being a Times for mildly xenophobic Conservatives (big C) into a Daily Mail for toffs.


From Yes, Prime Minister in '87:

The Morning Star is read by people who think the country ought to be run by another country. The Daily Telegraph is read by the people who think it is.

https://www.youtube.com/watch?v=DGscoaUWW2M


> Gravitational waves do NOT "shake the mirrors".

That depends on what gauge you're working in. What you say is true for the TT gauge, but not for other choices of gauge. See, e.g., section 1.3 of Maggiore's Gravitational Waves book.


a) He says just that, three paragraphs before he uses the shorthand "shakes" - which is in quotes, indicating the inaccuracy of the usage.


True, but it's a poor analogy. I've read many of his books - and it feels like this got editorialised or ghostwritten into "wrong" - he is usually a precise and excellent explainer of complex concepts.


Maybe he makes mistakes, or has trouble explaining some concepts, from time to time?


> I feel really sorry for the scientists who've spent decades working on this as part of a global collaboration to now have LIGO take all of the credit for this discovery.

You might as well say the same thing about CERN and the Higgs. That's how credit for discoveries works. You can't just give it to "the whole scientific community" so you pick the most specific attribution that makes sense.


You absolutely could though. Here's what you could say:

"Even though this discovery is our success, I would like to emphasize the fact that none of this would have been possible, had it not been for decades of work in this particular field by thousands of people who dedicated lives to pave the way for this final success. Just like Rome wasn't built in one day, such important discoveries are always the visible part of a huge network of dedicated individuals. This work will serve as a testimony to their hard work, we did build on the shoulders of giants and we'll always be grateful. Now's the time for celebration, but also for taking comfort in the knowing that the coming generations of scientists and engineers will build upon our findings for even greater discoveries in the future. To everyone, thank you."

That kind of stuff is both respectful of past discoveries in the field and creates a sense of community in science as a whole. It's much better in my opinion that singling out a couple of people, who despite their obvious hard work and brilliance, didn't single-handedly come up with the whole concept.


I don't know. Sounds a little like giving everybody a participant ribbon.

Scientists and engineers, more than anybody, understand that they are standing on the shoulders of giants.


I watched the press conference, and they pretty much did that. Generally, I feel that in physics, this is well handled. That's what citations are for.


Yes that is respectful, and a gracious way to announce it. But you'll note they still accepted credit and get attributed with credit.


it's understood that research builds upon past research which is documented and cited. i think that accomplishes the majority of what you're saying, albeit more tersely.


Which would be ligo, virgo, and geo600. It is not possible to triangulate the origin of gravitational waves with only two detectors.

It would be like crediting one section of the beam tube at cern for detecting the higgs.


well they do tend to credit the detector at lhc for the discovery. why won't people think of the tubes and all the other wires :(


If you watch the announcements you will notice that the individual detector teams do thank them for providing them with an excellent beam to work with, etc..

Also I would like to mention that unlike in the GR wave case the detectors do make the discoveries independently. Having multiple independent detectors on one accelerator is one cheap way to take care of reproducibility of results.


> LIGO take all of the credit for this discovery.

This was one of the purposes of LIGO. To prove what what previously conjecture. So yeah, goLigo.




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