Gravity Waves, Just the Fact(oids)
For those who couldn't make it through the epic tome I just posted. Just the factoids from the gravitational wave announcement:
- The LIGO project has announced what is pretty solid evidence that they have successfully detected gravitational waves. The video of the actual announcement is here.
- Gravity is, effectively, distortions in the shape of space, caused by the presence of massive objects (the earth, the sun, black holes, galaxies...)
- Gravitational waves are a 'traveling' version of that distortion, theoretically detectable at great distances from the original source
- These waves are created by very massive, fast-moving stellar objects, like black holes or neutron stars
- The actual waves cause a tiny, tiny distortion in space -- on the order of 1/10,000th of the width of a proton. It takes special techniques to even have a chance to detect them.
- Gravitational waves were predicted by Einstein (in 1916!) as a consequence of the theory of relativity, and were one of the few remaining unproven predictions of that theory.
- The event that was detected that led to this announcement happened in September. The intervening time has been used to get peer review and rule out other possible sources of the signal (experimental error, etc)
- There are two (and will soon be more) LIGO installations, geographically separated, to eliminate the possibility that local effects (like earthquakes) would be picked up and mistaken for actual signals
- The signals from the two locations, along with the predictions for them, and the two signals overlaid with each other, are visible here
- The event happened in roughly 200ms, with the majority of the energy being released in the final 20ms
- The frequency of the event is, if converted to audio, within the range of human hearing. You can listen to it here (two versions -- one at the actual frequency, one shifted upwards so humans can hear it better)
- This is probably the closest any of us will ever be to actually being able to directly listen to the universe.
- The event detected happened ~1.3 billion years ago, and involved two black holes
- The black holes were orbiting each other at roughly half the speed of light during the final moments of their merger
- The black holes were 29 solar masses and 36 solar masses. The resulting black hole was 62 solar masses
- The missing 3 solar masses were converted into energy in the form of gravitational waves
- The majority of this energy was released during the last 20ms of the event, making the energy output of the event briefly exceed the energy output of every other star in the rest of the visible universe by a factor of 50.
- This is not a weak, "oh, that looks kinda like what we expected, maybe this is gravity waves" kind of signal. The signal has a statistical certainty of above 5.1σ, which means it's almost certainly not some sort of random artifact.
- The statistical certainty doesn't rule out the possibility that we're measuring some other effect not gravitational waves, but given the extremely close match to the predictions of behavior and scale, that is rather unlikely.
- Gravitational waves are potentially an incredibly valuable astronomy tool, because they are not blocked by the things that block visible light (dust, bright objects, the universe not being transparent yet right after the big bang), so observations made via gravitational wave can not only supplement other types of observation, but can also makes observations that just aren't otherwise possible.
- You can read the actual paper here
- A good article with a lot of deeper info is available at physicsworld
- This list of bulletpoints has a bit of handwaving to save space
- I am not a scientist, please don't quote me as an authority, though I don't think I made any glaring errors (beyond handwaving) in the above
