I understood how LIGO works but one question I have is, how did scientists conclude the gravitational waves they detected are from a collision of 2 black holes that happened before 1.3 Billion/Million years ago.
Could someone explain ?
Physicists Detect Gravitational Waves, Proving Einstein Right
461–470 of 502 posts
Re: Physicists Detect Gravitational Waves, Proving Einstein Right
#462Earlier quoted context omitted.
Surely you are thinking of Sonar?
No, this came up on Hacker News recently: https://news.ycombinator.com/item?id=10810390
Gravity for navigation, perhaps ... but I believe they use magnetic fields, not gravitational fields, to detect other subs (and also some rather sophisticated real-time degaussing to prevent said detection): https://news.ycombinator.com/item?id=10979452
Re: Physicists Detect Gravitational Waves, Proving Einstein Right
#463Earlier quoted context omitted.
I'm assuming that the same rules apply as do in straight RF detection. A signal becomes a decent signal at 6db above noise and gets exponentially better every 6db above that. Something 20db above noise is rock solid reliable.
Uhh, 20db isn't the same as 20s/n ratio though?
SNR = 10log(Ps/Pw), solving
Ps/Pw = 10^(SNR/10) = 10^(20/10) == 100
A signal 20db above the noise, you could put your eye out with it.
db is confusing, when you're talking voltage it's 20log(Vs/Vw) And in absolute terms engineers talk about the power over 1mW.
Myself I get miffed a bit because people have been conditioned to think in terms of trying to pull facts out of crappy data sets using poorly thought out statistics. However in a lot of engineering and physics fields the data is often really good. Often good enough that you can work off a single measurement.
Re: Physicists Detect Gravitational Waves, Proving Einstein Right
#464But there is no "fabric of space-time". Time is a mental concept, it cannot be detected.
Whatever they have detected or calculated is something else.
Re: Physicists Detect Gravitational Waves, Proving Einstein Right
#465I'm wondering no-one mentioned Electric Universe which is the greatest opponent of this gravitational hocus-pocus religion. It would be much more beneficial to the humanity to focus smart peoples' attention to Birkeland currents or plasma or to the recent experiments of the SAFIRE project. They have several series on their youtube channel: https://www.youtube.com/user/ThunderboltsProject/videos
You ... must be trolling.
Re: Physicists Detect Gravitational Waves, Proving Einstein Right
#466I sometimes wonder why tech people like space-related stuff so much. It is a major news indeed and a feat of science and technology, but why is space so popular? Because it's otherworldly, large-scale and kind of making you feel empowered or united? I'm probably more interested in mundane, obscure and humble stuff, so this disproportionate popularity of space-related news is always baffling to me.
I believe it's all about the thrill of discovery. We know Earth comparatively well and there's simply not many areas left where a major discovery can be made. Sure, there's still much to learn, but these advances are made in small, incremental steps rather than major leaps. Space, on the other hand, is still largely a mystery, just like the oceans were for our ancestors.
Re: Physicists Detect Gravitational Waves, Proving Einstein Right
#467Earlier quoted context omitted.
> Imho whatever is carrying gravity between masses cannot itself have a mass. Forget gravitons, this already exists in pure general relativity. Spacetime is curved around a massive object, and that curvature contains energy. That's just another word for mass, so the curvature itself exerts gravity. This creates more curvature (...etc etc). This is one of the reasons as to why Einstein's equations are nonlinear. Note…
Only electrons get mass from the Higgs mechanism. Most of your mass comes from your protons and neutrons (or rather the energy "stored" in the bonds between the quarks that make them up).
You're talking about binding energy, and that's not where the majority of mass comes from.
All massive particles get their mass from the Higgs field.
Re: Physicists Detect Gravitational Waves, Proving Einstein Right
#468Earlier quoted context omitted.
Photon's and gravitons have to be masses because Gravity and Light and interact with matter at finite distances. If your 1 billion light years from earth, you are still effected by the Earth's gravity (well its likely smaller then experimental error but never mind that it still exist). So there needs to be gravitons from Earth flooding the entire sphere of space for 1 billion light years around the Earth. All these g…
> Photon's and gravitons have to be masses because Gravity and Light and interact with matter at finite distances. Photons don't have mass. If they had mass they couldn't travel at the speed of light.
The speed of light is the limit of time conduction in this universe.. It is the clock speed of the great animation
Re: Physicists Detect Gravitational Waves, Proving Einstein Right
#469Earlier quoted context omitted.
> For comparison, the sun makes up about 99.8% of the Solar System mass (500x as much mass as all the planets, dust, etc. combined). That leaves just 0.2% for all the planets, dust, Oort cloud, Kuiper belt, etc. So ... no.
Google "sun percentage mass solar system" and the highlighted answer is "By far most of the solar system's mass is in the Sun itself: somewhere between 99.8 and 99.9 percent." Please don't just disagree when you don't know what you are talking about.
I think you've misinterpreted my post. The "No" was in response to this:
> That always confused me. We have an Oort cloud, whose members we cannot resolve very well/at all. Why do we assume only our star has such a thing? If all stars did, that isn't enough mass to explain dark matter?
No, that isn't enough mass to explain dark matter, since it's only 0.1% to 0.2% of the mass of the solar system.
The text I quoted was in complete agreement with what you and others have posted. I was pointing out that the questioner's point had already been answered.
Re: Physicists Detect Gravitational Waves, Proving Einstein Right
#470Earlier quoted context omitted.
You are suggesting possible future events that would provide evidence for a multiverse. That does not make something a falsifiable theory. Analogy: it could happen that tomorrow Jesus Christ descends from the heavens and brings the day of reckoning. That would prove Christianity to be true, but the fact that this could happen does not make Christianity a falsifiable theory. A falsifiable theory is a theory that predi…
Ok. What if spacetime folds back onto itself over a very long distance? Wouldn't that be (viewed locally, with our limited instruments) as if another version of spacetime touches upon our version of spacetime?
Physics will always be based on observations. Consciousness is fundamentally hinged TO observation. I'd argue that the way your brain works is more fundamental to reality than the physics causing a Mhz of conduction throughout your synapses. In summary, all bullshit theories are possible in spirit of deceit. For why should good senses be wasted on a cohesive system when the mind is simply a slave to its own devices?