6 ms·

What Will It Mean If LIGO Detects Gravitational Waves?

49 points by oneworld 11y ago

oneworld 11y ago
Great explanation of what it might mean: http://www.forbes.com/sites/startswithabang/2016/02/09/what-will-it-mean-if-ligo-detects-gravitational-waves/#34ef8e7e4726 http://www.forbes.com/sites/startswithabang/2016/02/09/what-... Also, how effing cool is it that we are able to detect changes in spacetime itself!
- dang 11y ago
  An announcement of an announcement is always off-topic here, so we changed the URL from http://www.ligo.org/news/media-advisory.php http://www.ligo.org/news/media-advisory.php to that article, which is much more substantive. Thanks! The announcement itself, of course, will be on topic when it happens, but we can be patient.
  - porsupah 11y ago
    FWIW, there's also https://www.theguardian.com/science/2016/feb/09/watch-this-spacetime-gravitational-wave-discovery-expected https://www.theguardian.com/science/2016/feb/09/watch-this-s..., with no adblock issues.
    - dang 11y ago
      Ok, we changed to that from http://www.forbes.com/sites/startswithabang/2016/02/09/what-will-it-mean-if-ligo-detects-gravitational-waves/#34ef8e7e4726 http://www.forbes.com/sites/startswithabang/2016/02/09/what-....
- qubex 11y ago
  We've been “detecting space-time distortions” by means of falling for quite some time.
- jack9 11y ago
  > Sure, it travels through space at the speed of light, but it itself is a ripple in the fabric of space I don't believe that's been proven yet. I was under the impression that this was an experiment to provide evidence of the speed of gravity propagation.
  - Florin_Andrei 11y ago
    Sure, it's not been actually measured yet, but if it does anything different from that, we would have to do a pretty massive rewrite of several chapters of physics. It's a little unlikely. That being said, of course, anything could happen. Nature is not bound to follow our assumptions.
mrfusion 11y ago
And conversely what would it mean if we never detect gravity waves? Are there any reasonable theories that posit that gravity waves don't exist?
- deleted 11y ago
  [deleted]
- madaxe_again 11y ago
  That general relativity is either incomplete or wrong. It would mean that gravity either propagates far more rapidly or far more slowly than we think. Given however that c is considered and so far demonstrably the maximum velocity of information propagation in this spacetime, instantaneous propagation seems unlikely, particularly given the Mercury orbital confirmation. That all said, we may be looking at things naively.
  - ars 11y ago
    It could also mean that there are no objects large enough to produce gravity waves we can detect. Black holes for example dilate time, and may either not exist (since they take infinite time to form), or may produce gravity waves that are too time dilated (i.e. slow) to detect.
    - madaxe_again 11y ago
      That too. It could also mean that something unknown to us (dark matter halo?) dampens gravitational waves on earth - which is what ESA's eLISA would get around, if it is the case.
    - semi-extrinsic 11y ago
      > Black holes (...) take infinite time to form This is wrong, and based on not taking into account that in GR, simultaneity is not only a relative thing, but also a local thing. There is much more detail in several great answers to this Stack Exchange question: http://physics.stackexchange.com/questions/5031/can-black-holes-form-in-a-finite-amount-of-time http://physics.stackexchange.com/questions/5031/can-black-ho...
madaxe_again 11y ago
I'm curious as to why ligo is the only project ever mentioned, particularly given that they have to work with virgo and geo600 to be able to triangulate their observations - a two axis interferometer only gives you partial information. Better PR team?
- camillomiller 11y ago
  In Italy there's a lot of buzz around Virgo (located near Pisa), but I had the impression that it's mostly national talk, too.
  - madaxe_again 11y ago
    Yeah - I visited virgo years ago when they were about to start calibration - it's super cool, but then again, I think michelson-morely interferometers are cool as a category. They were invented for a not dissimilar purpose - testing the properties of the luminiferous aether seeing if light and matter moved at different rates depending on the earth's motion through the aether. The result was negative, and a patent clerk got thinking. Now his ideas are being put to the test with the same apparatus. So cool.
- ISL 11y ago
  If you look carefully at the press release, the group that's presenting on Thursday is the LSC, the LIGO Scientific Collaboration, which includes VIRGO and GEO. It's one big group, as everyone in the field shares hardware techniques and analysis techniques.
  - madaxe_again 11y ago
    Yes, I know that, but the press only mention ligo. I'd assume because it's the only American one.
- gaur 11y ago
  The new Virgo detector is not operational yet. GEO600 is operational, but it is much less sensitive that the Ligo detectors.
cornholio 11y ago
I hope Forbes realizes that blocking access to users with add blockers is not only a way to get rid of freeloaders, but also a way to ensure those people avoid Forbes altogether in the future and also avoid passing around Forbes links, since not everybody can see them. Alienating your audience is a very expensive mistake and the cost savings related to page serving are negligible. While I can turn off my add blocker, I won't, my mother can't because she's not aware I have installed one for her and has no idea what it is and what it does.
- robhu 11y ago
  They do not detect uBlock Origins.
  - e40 11y ago
    With the 3rd-party filter "Anti-Adblock Killer | Reek‎" enabled.
- wiwillia 11y ago
  I hear what you're saying, but I'm not sure I agree with the argument that this approach is not in their interest (I also use an ad blocker by the way, not preaching just being practical). I would bet that ~50%+ of people are choosing to disable their ad blocker to view Forbes content once they got stopped (I did), and that that the value driven by that increase in ads served outweighs the cost of not having the small % of users who refuse to turn off ad blockers not share their links. I can also 100% guarantee they split tested this, before rolling it out, to make sure it was the right cost/benefit choice.
- mastazi 11y ago
  Not the same article, but I suspect this one inspired the Forbes one, and it seems to provide more details: http://www.nature.com/news/gravitational-waves-5-cosmic-questions-they-can-tackle-1.19337 http://www.nature.com/news/gravitational-waves-5-cosmic-ques... > a way to ensure those people avoid Forbes altogether in the future I have an ad blocker and never ended up doing this. I either forget which websites are "blocking ad blockers", or I just click without checking the source, especially if the link is in the home of a site I trust like HN.
deleted 11y ago
[deleted]
antognini 11y ago
Not only will the discovery of gravitational waves confirm an important prediction of general relativity, but it will be the first test of GR in the strong gravity regime. So far, all the tests of GR have been in the weak gravity regime, where Newton's law of gravity is approximately correct. The precession of Mercury's perihelion, gravitational redshift, the gravitational deflection of light, and the measurement of frame dragging by Gravity Probe B have all been probing similar regions of parameter space --- slow velocities (compared to the speed of light) and weak gravity (i.e. far from the event horizon of a black hole). If the rumors are true that LIGO has detected the merger of two black holes, the observed waveform will be the first test of the predictions of general relativity in the strong gravity limit. This is the most interesting limit because this is where physics diverges the most from Newtonian gravity. Moreover, it's much easier to detect deviations from general relativity in this limit. LIGO's detection won't be the only test of GR in the strong gravity limit for too long, however. The Event Horizon Telescope has been trying to directly observe the event horizon of the supermassive black hole at the center of the Milky Way (or its shadow, anyway) and should have its first images within a few years.
polemic 11y ago
Am I right that this is basically this is a super high tech Michelson–Morley experiment, to detect waves instead of aether?
- InclinedPlane 11y ago
  That's exactly what it is.

49 points by oneworld 11y ago

Great explanation of what it might mean: http://www.forbes.com/sites/startswithabang/2016/02/09/what-will-it-mean-if-ligo-detects-gravitational-waves/#34ef8e7e4726 http://www.forbes.com/sites/startswithabang/2016/02/09/what-... Also, how effing cool is it that we are able to detect changes in spacetime itself!

dang 11y ago
An announcement of an announcement is always off-topic here, so we changed the URL from http://www.ligo.org/news/media-advisory.php http://www.ligo.org/news/media-advisory.php to that article, which is much more substantive. Thanks! The announcement itself, of course, will be on topic when it happens, but we can be patient.
- porsupah 11y ago
  FWIW, there's also https://www.theguardian.com/science/2016/feb/09/watch-this-spacetime-gravitational-wave-discovery-expected https://www.theguardian.com/science/2016/feb/09/watch-this-s..., with no adblock issues.
  - dang 11y ago
    Ok, we changed to that from http://www.forbes.com/sites/startswithabang/2016/02/09/what-will-it-mean-if-ligo-detects-gravitational-waves/#34ef8e7e4726 http://www.forbes.com/sites/startswithabang/2016/02/09/what-....
qubex 11y ago
We've been “detecting space-time distortions” by means of falling for quite some time.
jack9 11y ago
> Sure, it travels through space at the speed of light, but it itself is a ripple in the fabric of space I don't believe that's been proven yet. I was under the impression that this was an experiment to provide evidence of the speed of gravity propagation.
- Florin_Andrei 11y ago
  Sure, it's not been actually measured yet, but if it does anything different from that, we would have to do a pretty massive rewrite of several chapters of physics. It's a little unlikely. That being said, of course, anything could happen. Nature is not bound to follow our assumptions.

mrfusion 11y ago

And conversely what would it mean if we never detect gravity waves? Are there any reasonable theories that posit that gravity waves don't exist?

deleted 11y ago
[deleted]
madaxe_again 11y ago
That general relativity is either incomplete or wrong. It would mean that gravity either propagates far more rapidly or far more slowly than we think. Given however that c is considered and so far demonstrably the maximum velocity of information propagation in this spacetime, instantaneous propagation seems unlikely, particularly given the Mercury orbital confirmation. That all said, we may be looking at things naively.
- ars 11y ago
  It could also mean that there are no objects large enough to produce gravity waves we can detect. Black holes for example dilate time, and may either not exist (since they take infinite time to form), or may produce gravity waves that are too time dilated (i.e. slow) to detect.
  - madaxe_again 11y ago
    That too. It could also mean that something unknown to us (dark matter halo?) dampens gravitational waves on earth - which is what ESA's eLISA would get around, if it is the case.
  - semi-extrinsic 11y ago
    > Black holes (...) take infinite time to form This is wrong, and based on not taking into account that in GR, simultaneity is not only a relative thing, but also a local thing. There is much more detail in several great answers to this Stack Exchange question: http://physics.stackexchange.com/questions/5031/can-black-holes-form-in-a-finite-amount-of-time http://physics.stackexchange.com/questions/5031/can-black-ho...

madaxe_again 11y ago

I'm curious as to why ligo is the only project ever mentioned, particularly given that they have to work with virgo and geo600 to be able to triangulate their observations - a two axis interferometer only gives you partial information. Better PR team?

camillomiller 11y ago
In Italy there's a lot of buzz around Virgo (located near Pisa), but I had the impression that it's mostly national talk, too.
- madaxe_again 11y ago
  Yeah - I visited virgo years ago when they were about to start calibration - it's super cool, but then again, I think michelson-morely interferometers are cool as a category. They were invented for a not dissimilar purpose - testing the properties of the luminiferous aether seeing if light and matter moved at different rates depending on the earth's motion through the aether. The result was negative, and a patent clerk got thinking. Now his ideas are being put to the test with the same apparatus. So cool.
ISL 11y ago
If you look carefully at the press release, the group that's presenting on Thursday is the LSC, the LIGO Scientific Collaboration, which includes VIRGO and GEO. It's one big group, as everyone in the field shares hardware techniques and analysis techniques.
- madaxe_again 11y ago
  Yes, I know that, but the press only mention ligo. I'd assume because it's the only American one.
gaur 11y ago
The new Virgo detector is not operational yet. GEO600 is operational, but it is much less sensitive that the Ligo detectors.

cornholio 11y ago

I hope Forbes realizes that blocking access to users with add blockers is not only a way to get rid of freeloaders, but also a way to ensure those people avoid Forbes altogether in the future and also avoid passing around Forbes links, since not everybody can see them. Alienating your audience is a very expensive mistake and the cost savings related to page serving are negligible. While I can turn off my add blocker, I won't, my mother can't because she's not aware I have installed one for her and has no idea what it is and what it does.

robhu 11y ago
They do not detect uBlock Origins.
- e40 11y ago
  With the 3rd-party filter "Anti-Adblock Killer | Reek‎" enabled.
wiwillia 11y ago
I hear what you're saying, but I'm not sure I agree with the argument that this approach is not in their interest (I also use an ad blocker by the way, not preaching just being practical). I would bet that ~50%+ of people are choosing to disable their ad blocker to view Forbes content once they got stopped (I did), and that that the value driven by that increase in ads served outweighs the cost of not having the small % of users who refuse to turn off ad blockers not share their links. I can also 100% guarantee they split tested this, before rolling it out, to make sure it was the right cost/benefit choice.
mastazi 11y ago
Not the same article, but I suspect this one inspired the Forbes one, and it seems to provide more details: http://www.nature.com/news/gravitational-waves-5-cosmic-questions-they-can-tackle-1.19337 http://www.nature.com/news/gravitational-waves-5-cosmic-ques... > a way to ensure those people avoid Forbes altogether in the future I have an ad blocker and never ended up doing this. I either forget which websites are "blocking ad blockers", or I just click without checking the source, especially if the link is in the home of a site I trust like HN.

deleted 11y ago

[deleted]

antognini 11y ago

Not only will the discovery of gravitational waves confirm an important prediction of general relativity, but it will be the first test of GR in the strong gravity regime. So far, all the tests of GR have been in the weak gravity regime, where Newton's law of gravity is approximately correct. The precession of Mercury's perihelion, gravitational redshift, the gravitational deflection of light, and the measurement of frame dragging by Gravity Probe B have all been probing similar regions of parameter space --- slow velocities (compared to the speed of light) and weak gravity (i.e. far from the event horizon of a black hole). If the rumors are true that LIGO has detected the merger of two black holes, the observed waveform will be the first test of the predictions of general relativity in the strong gravity limit. This is the most interesting limit because this is where physics diverges the most from Newtonian gravity. Moreover, it's much easier to detect deviations from general relativity in this limit. LIGO's detection won't be the only test of GR in the strong gravity limit for too long, however. The Event Horizon Telescope has been trying to directly observe the event horizon of the supermassive black hole at the center of the Milky Way (or its shadow, anyway) and should have its first images within a few years.

polemic 11y ago

Am I right that this is basically this is a super high tech Michelson–Morley experiment, to detect waves instead of aether?

InclinedPlane 11y ago
That's exactly what it is.