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Physicists Detect Gravitational Waves, Proving Einstein Right

nytimes.com

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Re: Physicists Detect Gravitational Waves, Proving Einstein Right

#391

Post by josho »

hun-nemethpeter wrote: post #389

According to this paper ( https://dcc.ligo.org/LIGO-P150914/public ) they detected the signal first at Livingston, Louisiana and 6.9ms later in Hanford, Washington. The distance between them according to wikipedia ( https://en.wikipedia.org/wiki/LIGO ) is 3002km (Ok, the 3002 km distance is on the Earth). If the gravity wave travel at the speed of light they should detect 10ms later (300 000/3002 sec = 1/100 sec = 10…

Wild guess on my part. The wave is traveling through the earth, while the distance you measured is around the circumference and therefore larger.

Too bad, you had me excited for a moment at the thought of faster than light travel.

Re: Physicists Detect Gravitational Waves, Proving Einstein Right

#392

Post by cyphar »

purpled_haze wrote: post #388
contravariant wrote: post #210

Earlier quoted context omitted.

Force carrying particles in general don't have mass. Except that some of them seem to do, which was rather puzzling for some time, but was solved using the Higgs mechanism. I can't think of an obvious reason the Higgs mechanism wouldn't work for gravitons, but I could be mistaken, it's not exactly the most intuitive area of physics. Also, keep in mind that the strong force transmits the force between colour charges w…

> Force carrying particles in general don't have mass. Massless particles don't have energy. Massless and energyless particles have no speed. I have no interest in massless and energyless particles that stand still.

Photons are massless particles that have energy. All massless particles travel at the speed of light.

Re: Physicists Detect Gravitational Waves, Proving Einstein Right

#393

Post by AnonNo15 »

josho wrote: post #391
hun-nemethpeter wrote: post #389

According to this paper ( https://dcc.ligo.org/LIGO-P150914/public ) they detected the signal first at Livingston, Louisiana and 6.9ms later in Hanford, Washington. The distance between them according to wikipedia ( https://en.wikipedia.org/wiki/LIGO ) is 3002km (Ok, the 3002 km distance is on the Earth). If the gravity wave travel at the speed of light they should detect 10ms later (300 000/3002 sec = 1/100 sec = 10…

Wild guess on my part. The wave is traveling through the earth, while the distance you measured is around the circumference and therefore larger. Too bad, you had me excited for a moment at the thought of faster than light travel.

Even ignoring the curvature of the Earth, the signal source was not necessary located on the straight line between two LIGO locations, but rather at some angle to this line. For example if the signal origin was on the line that is exactly between the two LIGO detectors, the time delay would be zero.

Re: Physicists Detect Gravitational Waves, Proving Einstein Right

#394

Post by cyphar »

Manishearth wrote: post #365
sandworm101 wrote: post #181

Earlier quoted context omitted.

If gravitons have mass, then the universe is too strange to exist. Gravity is an interaction that defines the presence of matter (see dark matter). For the object that transmits that force between masses to itself have mass ... how can a black hole then project gravity? Imho whatever is carrying gravity between masses cannot itself have a mass.

> 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).

Re: Physicists Detect Gravitational Waves, Proving Einstein Right

#395

Post by kijin »

thaumasiotes wrote: post #364
undersuit wrote: post #357

Earlier quoted context omitted.

First we need to find out how to create repulsion. Right now I'm pretty sure a graviton generator would just be a novelty device that weighs more than what it's mass would lead you to think it weighs. Maybe we could make orbital graviton beam generator that could literally suck an object off the face of the Earth.

> a novelty device that weighs more than what it's mass would lead you to think it weighs This is an interesting concept. As far as I'm aware, we have ways of measuring weight, but no way of measuring mass. How would you know whether something weighed more than it "should", based on its "mass"?

All you need is a switch to turn it on and off.

Tell someone to hold it. Turn it off. Watch them struggle with the sudden weight. Turn it back on.

Re: Physicists Detect Gravitational Waves, Proving Einstein Right

#396

Post by cyphar »

valarauca1 wrote: post #293
SaberTail wrote: post #212

Earlier quoted context omitted.

What do you think of the strong nuclear force? Gluons are the force carriers between color-charged particles. And gluons themselves have a color charge. So gluons transmit force between each other. Does that mean the universe is already too strange to exist? By the way, this is why the strong nuclear force has such a short range. Gravity has infinite range as far as we can tell, so that makes it unlikely that the gra…

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.

Re: Physicists Detect Gravitational Waves, Proving Einstein Right

#397

Post by thisrod »

4k wrote: post #29

I have a question: what does this mean for theoretical physics? (except for Einstein was right) Does it settle any major debates? Does it make any competing theory more or less likely? Sorry I am not vary knowledgeable on the topic.

This is the result the theories predicted, and there's nothing for the theorists to do except gloat. If people had kept building more sensitive detectors, and kept failing to detect gravity waves, then eventually that would have been a very big deal for theoretical physics. But it didn't happen.

On the other hand, there is now a way to see dark matter. That could enable a lot of new astronomy.

Re: Physicists Detect Gravitational Waves, Proving Einstein Right

#398

Post by thisrod »

soneca wrote: post #108

Honest question: there is any example of Einstein being proved wrong ? Was he indeed always right on his theories for phenomenons before they could be proved by experiments; or is that the case that we only hear about when he is proved right?

Try asking that question in Hiroshima :-(

Re: Physicists Detect Gravitational Waves, Proving Einstein Right

#399

Post by sqldba »

other_herbert wrote: post #346
ScottBurson wrote: post #336

Earlier quoted context omitted.

I think you must be right -- but maybe there's some other way to create them, without needing to move a mass. The ability to manipulate gravity itself might be the key to space travel.

Flying cars man! Think of the flying cars! And maybe real hover boards

"Here's a board with wheels we call a hover board!"

Re: Physicists Detect Gravitational Waves, Proving Einstein Right

#400

Post by demallien »

hun-nemethpeter wrote: post #389

According to this paper ( https://dcc.ligo.org/LIGO-P150914/public ) they detected the signal first at Livingston, Louisiana and 6.9ms later in Hanford, Washington. The distance between them according to wikipedia ( https://en.wikipedia.org/wiki/LIGO ) is 3002km (Ok, the 3002 km distance is on the Earth). If the gravity wave travel at the speed of light they should detect 10ms later (300 000/3002 sec = 1/100 sec = 10…

10ms is the absolute maximum difference in time, if the source was located on a line running through the two detectors. If the source was located on a perpendicular bisector of the line running through the two detectors, the difference in time between detections at the two detectors would be zero. Any value between the two is possible depending on the geometry.
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