8 ms·

The Absurdity of Detecting Gravitational Waves (2017) [video]

108 points by basicplus2 8y ago

phkahler 8y ago
This seems like a thing to build on the moon.
- _Microft 8y ago
  Or even better - make it space based: https://en.wikipedia.org/wiki/Laser_Interferometer_Space_Antenna https://en.wikipedia.org/wiki/Laser_Interferometer_Space_Ant...
  - imnobody 8y ago
    Unfortunate to see NASA was forced to withdrawal (for budgetary concerns).
    - sleavey 8y ago
      LISA has now been funded by ESA with a small contribution from NASA. It is slated for launch in the late 2020s / early 2030s.
- sleavey 8y ago
  Funnily enough, the moon has recently been used to constrain the gravitational wave stochastic background [1], i.e. the space-time strain created by the stochastic gravitational wave emission of all massive bodies in the universe. [1] https://journals.aps.org/prd/abstract/10.1103/PhysRevD.90.102001 https://journals.aps.org/prd/abstract/10.1103/PhysRevD.90.10...
- stefanough 8y ago
  This is actually a plot point in Greg Egan's Diaspora. A moon-based laser interferometer is used to detect an impending neutron star merger that will have catastrophic results for biological life on Earth.
sillysaurus3 8y ago
Happy to see Veritasium getting some attention on HN. You may have seen his previous video from 2014, Facebook Fraud: https://www.youtube.com/watch?v=oVfHeWTKjag https://www.youtube.com/watch?v=oVfHeWTKjag One of my favorite videos is on his alternate channel, 2veritasum. Survivor Bias: https://www.youtube.com/watch?v=_Qd3erAPI9w https://www.youtube.com/watch?v=_Qd3erAPI9w
- RachelF 8y ago
  He's a great presenter, not the normal dumbed down documentaries that are fashionable these days. He actually tries to explain things, not just waffle and make the watcher feel good. He recently made a full length movie: https://www.vitamaniathemovie.com/ https://www.vitamaniathemovie.com/
TomMckenny 8y ago
I wonder if gravity wave detection could be ever be precise enough for communication. I wonder this because it occurs to me that one possible answer to Fermi's paradox is that aliens don't use Radio or other EM to chat. And maybe they don't leak it because they move energy and information around more efficiently than we do.
- meowface 8y ago
  Even if tons of intelligent civilizations happened to be radiating gravitational waves (or some other form of radiation which travels at or very close to the speed of light) encoded with information directly towards Earth right now, it's very likely we'd never receive them in the next million years due to the vastness of the universe.
  - roywiggins 8y ago
    What about all of the intelligent civilizations who were doing it a million years ago? With a million years for waves to fill space, you'd think we'd be able to hear something.
    - LoSboccacc 8y ago
      Not necessarily, immagine scanning all radio frequencies except you don’t know neither modulation nor the symbols transmitted. Separating something from noise is a challenge on itself especially if signals are compressed or encrypted
    - meowface 8y ago
      Maybe. Or maybe the time range of broadcasts that reached our solar system was several millions or even billions years ago. Or maybe it was as recent as 10,000 years ago, but we had no way of detecting or decoding them. Or maybe nearly all of the intelligent life existent in the universe doesn't yet have the capability to transmit information via gravitational waves or other resilient media. Or maybe humans really are one of the first instances of intelligent life in the universe, and the broadcasts won't start coming until millions of years from now... or never. And the most disappointing/intriguing part is there's a good chance humanity will never, ever know the answers and will never have any confirmation or denial of any of those possibilities. Or if they do, it might be so far into the future that humanity as a concept will cease to exist. The universe is just too big.
ArtWomb 8y ago
No concrete data on actual funding increases, but it appears the success of LIGO and gravity wave detection has kicked off a renaissance in basic research into fundamental theories of gravitation itself. With a space-based gravity wave detector in various stages of development. And the possibility that gravitons have been indirectly observed already. Is Gravity Quantum? https://www.scientificamerican.com/article/is-gravity-quantum/ https://www.scientificamerican.com/article/is-gravity-quantu...
- v_lisivka 8y ago
  LIGO is scaled up version of Michelson-Morley experiment, so we should ask very different kind of question.
mysterypie 8y ago
I figured that one tube is stretched by the gravitational waves and the perpendicular tube is unaffected, so you're measuring the difference between the two tubes. Simple and easy to understand. However, the video mentioned that both light and the detection apparatus are stretched by the same degree and the physicist says "the light does get stretched and that part doesn't do the measurement for us"[1] -- which makes me think that the simple and easy explanation is not quite right. There's some subtlety that I think I'm missing. [1] https://m.youtube.com/watch?v=iphcyNWFD10&t=376s https://m.youtube.com/watch?v=iphcyNWFD10&t=376s (6min 16sec into the video)
- AnsisMalins 8y ago
  Light takes different amounts of time to travel down the stretched vs squeezed tube.
  - deleted 8y ago
    [deleted]
  - stultifying 8y ago
    Yes, the speed of light cannot exceed its limitation, and as one channel stretches in length, it simply requires more time to travel that length at the constant maximum speed. The fixed channel remains the same, and covers the unstretched distance, so the light, traveling at the same constant speed reaches the end of the unchanged channel within less time than the other channel. Or invert the same effect for cases where one channel is compressed to a shorter length, since waves oscillate. So both circumstances may be encountered. Some photons will traverse a compressed distance at a fixed speed, other photons will traverse a stretched distance. Meanwhile, the other perpedicular path is neither stretched nor squashed, and the photons in that channel demostrate the difference when compared to the effected channel. So no matter what happens, the rate of travel is locked at the upper limit of 186,000 miles per second, whether all of space, energy and matter is squashed in a slightly smaller volume, or expanded to fill a slightly larger volume, the relativistic distances do not change, and the rate of passage of time does not change.
- Certhas 8y ago
bajsejohannes 8y ago
One thing the book Black Hole Blues (Janna Levin) brought home to me was the absurdity of actually getting this project done. Now that it's complete, it's easy to say that it was obviously a good idea. It's another thing entirely to bet huge budgets on something that doesn't seem very likely to succeed.
acranox 8y ago
I got to visit LIGO in Louisiana a few years back. I remember they lamented that it was not as remote as they really wanted. The detector picked up nearby hunting activity, and logging activity in the woods. And they had to shut down measurements for a couple hours every week when the liquid nitrogen truck drove in due to the road vibrations it created. It’s an awesome experiment. And it requires huge computational resources to process all the data they take in.
- pinko 8y ago
  The seismic isolation is much better since the Advanced LIGO upgrade completed in 2014 -- when were you there? (I'm also happy to answer any computing questions; that's my area.)

108 points by basicplus2 8y ago

phkahler 8y ago

This seems like a thing to build on the moon.

_Microft 8y ago
Or even better - make it space based: https://en.wikipedia.org/wiki/Laser_Interferometer_Space_Antenna https://en.wikipedia.org/wiki/Laser_Interferometer_Space_Ant...
- imnobody 8y ago
  Unfortunate to see NASA was forced to withdrawal (for budgetary concerns).
  - sleavey 8y ago
    LISA has now been funded by ESA with a small contribution from NASA. It is slated for launch in the late 2020s / early 2030s.
sleavey 8y ago
Funnily enough, the moon has recently been used to constrain the gravitational wave stochastic background [1], i.e. the space-time strain created by the stochastic gravitational wave emission of all massive bodies in the universe. [1] https://journals.aps.org/prd/abstract/10.1103/PhysRevD.90.102001 https://journals.aps.org/prd/abstract/10.1103/PhysRevD.90.10...
stefanough 8y ago
This is actually a plot point in Greg Egan's Diaspora. A moon-based laser interferometer is used to detect an impending neutron star merger that will have catastrophic results for biological life on Earth.

sillysaurus3 8y ago

Happy to see Veritasium getting some attention on HN. You may have seen his previous video from 2014, Facebook Fraud: https://www.youtube.com/watch?v=oVfHeWTKjag https://www.youtube.com/watch?v=oVfHeWTKjag One of my favorite videos is on his alternate channel, 2veritasum. Survivor Bias: https://www.youtube.com/watch?v=_Qd3erAPI9w https://www.youtube.com/watch?v=_Qd3erAPI9w

RachelF 8y ago
He's a great presenter, not the normal dumbed down documentaries that are fashionable these days. He actually tries to explain things, not just waffle and make the watcher feel good. He recently made a full length movie: https://www.vitamaniathemovie.com/ https://www.vitamaniathemovie.com/

TomMckenny 8y ago

I wonder if gravity wave detection could be ever be precise enough for communication. I wonder this because it occurs to me that one possible answer to Fermi's paradox is that aliens don't use Radio or other EM to chat. And maybe they don't leak it because they move energy and information around more efficiently than we do.

meowface 8y ago
Even if tons of intelligent civilizations happened to be radiating gravitational waves (or some other form of radiation which travels at or very close to the speed of light) encoded with information directly towards Earth right now, it's very likely we'd never receive them in the next million years due to the vastness of the universe.
- roywiggins 8y ago
  What about all of the intelligent civilizations who were doing it a million years ago? With a million years for waves to fill space, you'd think we'd be able to hear something.
  - LoSboccacc 8y ago
    Not necessarily, immagine scanning all radio frequencies except you don’t know neither modulation nor the symbols transmitted. Separating something from noise is a challenge on itself especially if signals are compressed or encrypted
  - meowface 8y ago
    Maybe. Or maybe the time range of broadcasts that reached our solar system was several millions or even billions years ago. Or maybe it was as recent as 10,000 years ago, but we had no way of detecting or decoding them. Or maybe nearly all of the intelligent life existent in the universe doesn't yet have the capability to transmit information via gravitational waves or other resilient media. Or maybe humans really are one of the first instances of intelligent life in the universe, and the broadcasts won't start coming until millions of years from now... or never. And the most disappointing/intriguing part is there's a good chance humanity will never, ever know the answers and will never have any confirmation or denial of any of those possibilities. Or if they do, it might be so far into the future that humanity as a concept will cease to exist. The universe is just too big.

ArtWomb 8y ago

No concrete data on actual funding increases, but it appears the success of LIGO and gravity wave detection has kicked off a renaissance in basic research into fundamental theories of gravitation itself. With a space-based gravity wave detector in various stages of development. And the possibility that gravitons have been indirectly observed already. Is Gravity Quantum? https://www.scientificamerican.com/article/is-gravity-quantum/ https://www.scientificamerican.com/article/is-gravity-quantu...

v_lisivka 8y ago
LIGO is scaled up version of Michelson-Morley experiment, so we should ask very different kind of question.

mysterypie 8y ago

I figured that one tube is stretched by the gravitational waves and the perpendicular tube is unaffected, so you're measuring the difference between the two tubes. Simple and easy to understand. However, the video mentioned that both light and the detection apparatus are stretched by the same degree and the physicist says "the light does get stretched and that part doesn't do the measurement for us"[1] -- which makes me think that the simple and easy explanation is not quite right. There's some subtlety that I think I'm missing. [1] https://m.youtube.com/watch?v=iphcyNWFD10&t=376s https://m.youtube.com/watch?v=iphcyNWFD10&t=376s (6min 16sec into the video)

AnsisMalins 8y ago
Light takes different amounts of time to travel down the stretched vs squeezed tube.
- deleted 8y ago
  [deleted]
- stultifying 8y ago
  Yes, the speed of light cannot exceed its limitation, and as one channel stretches in length, it simply requires more time to travel that length at the constant maximum speed. The fixed channel remains the same, and covers the unstretched distance, so the light, traveling at the same constant speed reaches the end of the unchanged channel within less time than the other channel. Or invert the same effect for cases where one channel is compressed to a shorter length, since waves oscillate. So both circumstances may be encountered. Some photons will traverse a compressed distance at a fixed speed, other photons will traverse a stretched distance. Meanwhile, the other perpedicular path is neither stretched nor squashed, and the photons in that channel demostrate the difference when compared to the effected channel. So no matter what happens, the rate of travel is locked at the upper limit of 186,000 miles per second, whether all of space, energy and matter is squashed in a slightly smaller volume, or expanded to fill a slightly larger volume, the relativistic distances do not change, and the rate of passage of time does not change.
Certhas 8y ago

bajsejohannes 8y ago

One thing the book Black Hole Blues (Janna Levin) brought home to me was the absurdity of actually getting this project done. Now that it's complete, it's easy to say that it was obviously a good idea. It's another thing entirely to bet huge budgets on something that doesn't seem very likely to succeed.

acranox 8y ago

I got to visit LIGO in Louisiana a few years back. I remember they lamented that it was not as remote as they really wanted. The detector picked up nearby hunting activity, and logging activity in the woods. And they had to shut down measurements for a couple hours every week when the liquid nitrogen truck drove in due to the road vibrations it created. It’s an awesome experiment. And it requires huge computational resources to process all the data they take in.

pinko 8y ago
The seismic isolation is much better since the Advanced LIGO upgrade completed in 2014 -- when were you there? (I'm also happy to answer any computing questions; that's my area.)