Gravitational Waves

As I understand it ?

I haven't a f**king clue.

whas dat?

I think it's a massive step forward but I've no real understanding of what's going on. Einstein said gravitational waves would exist, It looks like that's been verified, a new branch of physics/astronomy appears to have been opened and I'm excited even though I don't know WTF it's all about.

I find that a surfeit of sherry (as if such a thing were possible) leads to the sensation of gravitational waves. 

As Dean Martin so eloquently put it : "you haven't drunk too much if you can still lie on the floor without having to hold on."

GraemeH posted:

How significant is the proof that gravitational waves exist?

G

Significant in the field of theoretical physics. Einstein's general relativity theory now has 100% of his predictions confirmed. Einstein considered that the detection of gravitational waves was essentially impossible in practice and never expected their existence to be observed. Any competing theories that would not explain gravitational waves have taken a big step back. Not as easy to see the immediate practical application of the confirmation of their existence, but the gaps between what seems purely scientific and practical application can be quite narrow. e.g. - there would be no GPS systems without the theory of relativity and no modern electronics without quantum theory.

Tony2011 posted:

whas dat?

I don't understand them, yet never doubted their existence as I find myself helplessly attracted to them.

I think it is amazing that space is suffused with constant gravitational noise, much as it is filled with light and other EM radiation. The scale is bizarrely miniscule but essentially every event of gravitational significance sends a ripple of gravity out into the universe. For now we can only detect the most massive changes (two black holes colliding) but who knows what else we can uncover. For now we have only ever inferred black holes from their influence on other structures-this is effectively a direct observation of them for the first time.

I think that is what it is anyway...

I also love the idea we are 'listening' to an event 4.25 billion light years away with some rods buried under the ground in Louisiana

Bruce

It gives you a way of looking at the universe not based on electromagnetic radiation. The only application I can see is observing black holes. Any Nobel prize should have gone to Einstein. Personally I had no doubts that they existed - just very difficult to detect.

winkyincanada posted:

 

 e.g. - there would be no GPS systems without the theory of relativity and no modern electronics without quantum theory.

I don't think that's entirely  true - although using the Theory of Relativity enables us to keep the Atomic Clocks in the Space Vehicles, more closely aligned with those on the ground. Consequently, the "arithmetic" that your GPS receiver has to perform is a bit "easier" to do.

In practice the clocks in the space vehicles are adjusted (to count fewer transitions to define each minute) to account for relativity and gravitation effects predicted by Einstein and this keeps them very closely aligned with those on the ground. But the inevitable mis-alignment has to be accounted for and incorporated into the Space Vehicle radio transmissions and taken into account in the 4-D space-time calculation by your receiver to give you your position.

I think.

As I understand it, there is a limit to how far back in time we can see with telescopes. We can see the cosmic microwave background, dating back to ~380,000 years after the Big Bang, but not beyond it. Before then, the universe was too hot and dense for light to travel very far without colliding into matter.

With this new discovery, we can apparently "listen" to these ancient noises produced by the effects on gravity by stars and black holes. And unlike light, nothing stops these gravitational waves. They can be detected here on earth, and we can make models to understand their signatures. Physicists are very exited that, for the first time, we now have the chance to understand what happened much earlier in the creation of the universe - much closer to the Big Bang itself.

ATB.

Hook

I liked their early stuff.

I believe what Don is saying is that without an understanding of the theory of relativity we wouwld have been scracthing our heads wondering why our lovely new shiny GPS satellites were giving fixings way off from where they should be

Understanding the theory allows us to compensate for those relative effects and gives an accuracy of 5-10 meters whereby without that understanding the fixes would be out by up to 10 km by the end of the day

As Don inferred this is counteracted by slowing down the ticking frequency of the atomic clocks before the satellites were launched

A man in a pub told that so it must be true :-)

I think we are confusing Special and General Relativity here. The GPS clocks are to do with Special Relativity. Nothing to do with gravitation whatsoever.

And the colliding black holes observed were only 3 billion light years distant. The most distant object seen using conventional telescopes would be the quasar ULAS J1120+0641, which is 29 billion light years away!

And there was I thinking that the age of the universe was about 13.7 billion years and that Special Relativity was just a subset of General Relativity. 

It's a pity Brian Cox no longer posts on here, even if just to see who would argue with him 

It's something to do with mirrors and smoke I think!

I would love to see the interactions between Dr Bri and certain other members. 

He has quite a good repartee on his Twitter posts. Not sure his language would get through the silly nanny filter here though.

I don't understand when it's said black holes can bend or even stop time due to its density - yet the Big Bang , as much as containing all the universe within a small point happened within a moment, surely from such density time would have unraveled at a very slow pace. Not so much a Big Bang , more a very slow Big Bang thats still banging !

I suppose that as there was nothing outside that point of singularity there was no reference frame in which the concept of time existed.

I just don't have a brain for this sort of thing. I get broadly what it is that is being evidenced, just not why it matters. I was with Will Self on his large Hadron Collider walk (not literally), largely agreeing with his wry cynical stance on the probable real value to human kind.

G

Anyone heard of a guy called Eric Hovind.  He is an American Creationist, who will love to pull this scientific  discovery to pieces.    I often watch him for a good laugh,  He states,but does not necessarily believe the universe is 4000 years old LOL LOL.

He is obviously in it for the money he makes from gullible people.

staffy posted:

He is obviously in it for the money he makes from gullible people.

The same could be said about the thousands of scientists making a bloody good living from all this Higgs Boson/Gravitation Pulse, etc. hocus pocus.

I'm with Graham, this kind of research is of no use to anybody. (except the scientists). Who cares when or how the universe was created.

Dozey posted:

I think we are confusing Special and General Relativity here. The GPS clocks are to do with Special Relativity. Nothing to do with gravitation whatsoever.

The atomic clocks in the GPS satellites are affected less by relative speed and more by gravity. Typical figures quoted are 7 micro seconds slower per day by speed and 45 micro seconds per day faster by less gravity. The overall outcome is that the satellite clocks run faster than the earth clocks by 38 micro seconds per day.

Changing these 38 micro seconds into 38,000 nano seconds per day brings things into perspective. Light travels at 1 foot per nano second. For GPS to be precise, clock times need to be known to within (say) 10 to 20 nano seconds. A 38,000 nano second timing error would translate into a 10km position error each day and continue to accumulate - unless the "arithmetic" in the GPS receiver took this time difference into account. Which it has to, but only to the extent of a few nano seconds rather than thousands of nano-seconds !

Rather than have clocks with 38,000 ns per day differences, (which would make the arithmetic a bit more difficult), the satellite clocks are adjusted before launch to compensate for these effects predicted by Einstein in his Special and General theories of relativity . In practice, simply changing the definition of the number of atomic transitions that constitute a 1 second interval (and consequently a nano second) achieves this aim. If the revised definition is right, the satellite clock, once in space, will count off seconds (and nano seconds) at the same rate as earth clocks.

Satellites don't always achieve their predicted orbit and hence the gravity effect isn't always accurately compensated..........so the "arithmetic has to take these, and other errors, into account in order to re-set the clocks in GPS receivers to "Atomic" time accuracy.

Hope this helps.

robgr posted:

I believe what Don is saying is that without an understanding of the theory of relativity we wouwld have been scracthing our heads wondering why our lovely new shiny GPS satellites were giving fixings way off from where they should be

Understanding the theory allows us to compensate for those relative effects and gives an accuracy of 5-10 meters whereby without that understanding the fixes would be out by up to 10 km by the end of the day

As Don inferred this is counteracted by slowing down the ticking frequency of the atomic clocks before the satellites were launched

A man in a pub told that so it must be true :-)

 

The man in the Pub helped me draft my comments in the post above, so I can confirm it must be true !

Presumably now that they have detected these gravitational waves they will be able to put to rest the theory of directionality of cables......