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Post by Progenitor A on Oct 11, 2010 17:22:17 GMT 1
The big search of the GUF. If gravity waves can be measured then perhaps gravity can be united with em waves and we will know the mind of God, well anyway the mind of someone or other.
Gravity waves are very hard to detect because gravity is such a WEAK force in comparison to otherts
Never mind really
Best way of detecting then is probably done by examining th sun, but of course other stars are far more dramatic..
Imagine an asteroid crashing into the sun - the sun's mass increases, it's gravitational potential increses and this increase radiates outward(probably at c) , so we should be able to measure Delts (g). But we don't
Why?
Looking at massivelbodies, the trouble is they are far away and the gravity reaching the earth is very weak at the earth's surface, So if another star crashes into our observed star the (delka) gravity will be tiny indeed. But in theory if a masive bosy collides with a star then we will have an impulse of time period (t), and Fourier tells us that there wil be multiple frequencies harmonically related to the period ot the impact time interval (t)i.
So Fourier tells us which 'gravitational ripples'to look for - Amplitude and frequncy
Why have they not been discovered?
Do they really exist?
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Post by carnyx on Oct 17, 2010 11:58:26 GMT 1
I dunno, but it seems to me that if we take Newtons idea that gravity is about masses attracting each other, and is felt by all bodies as a force.
All bodies are aggregates of particles of mass, at certain distanced L from each other, and so exist in their own local mutual mass-attraction mesh[i/] as it were.
So when a body is next to a more massive body, there wil be a gradient of the gravity force across the particles in that body . i.e that each particle feels a differengt level of attractive force, as well as the different levels of attractive force from all the neighbouring particles, which wil be resoved by slight differences in position of each particle to its neighbours in the mesh.
So if the big external body moves away, it will cause a change to the gravitational forces at each particle, and as they are all different, a wave of re-spacing between particles wil result as they relarrange their individual spacings to their neighbour. Then we might say that gravity waves can be seen in masses, as the cascading effect of forces propagating through them, and can be observed.
Also, when we look at these aggregations of particles that make a body, they must be constrained by other bonds than simple mass-attraction. As these bonds would also be more-or-less elastic, then we could see the gravitational waves propagating at a rate proportional to the elasticity of these other bonds.
So we should see the speed of gravity waves be very high in tightly bonded bodies such as crystals, and very slow in gases where the bonds are weaker.
Therefore we could say that gravitational waves can be measured in terms of the rate of propagation of the mass-shift of particles in bodies. Or more simply as shock waves.
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Post by Mr Red on Oct 18, 2010 10:28:52 GMT 1
if I wave too much my arm gets tired. Is this a gravity wave?
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Post by carnyx on Oct 18, 2010 13:09:18 GMT 1
@mr Red
If you know your Newton, yes.
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Post by speakertoanimals on Oct 18, 2010 16:27:11 GMT 1
The earlier post was in effect talking about tidal forces, whereas gravitational waves are different, in that the passage of a gravitational wave causes distortions in a direction perpendicular to its direction of travel.
They are also non-Newtonian. According to Newton, one star orbiting another will just continue to do so. Whereas according to Einstein, such a binary star system gradually looses energy by gravitational waves, and the effect of this on the periods of the orbits of binary pulsars has been measured.
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Post by abacus9900 on Oct 18, 2010 16:42:23 GMT 1
The earlier post was in effect talking about tidal forces, whereas gravitational waves are different, in that the passage of a gravitational wave causes distortions in a direction perpendicular to its direction of travel. They are also non-Newtonian. According to Newton, one star orbiting another will just continue to do so. Whereas according to Einstein, such a binary star system gradually looses energy by gravitational waves, and the effect of this on the periods of the orbits of binary pulsars has been measured. STA, I'm happy to see that you're improving your communication skills - you were concise and jargon-free. A diagram might have helped a bit, but a good effort nonetheless.
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Post by speakertoanimals on Oct 18, 2010 18:09:10 GMT 1
Seems any idiot can understand, as long as you leave out ANY of the technical content.
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Post by abacus9900 on Oct 18, 2010 18:20:26 GMT 1
STA, seriously, what is your motivation for posting on this MB? You seem to think it is basically a waste of time, so why?
BTW, you don't have to leave out all technical content as long as you attempt to make it clear what it means. Can you do that?
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Post by Progenitor A on Oct 18, 2010 20:36:03 GMT 1
The earlier post was in effect talking about tidal forces, whereas gravitational waves are different, in that the passage of a gravitational wave causes distortions in a direction perpendicular to its direction of travel. They are also non-Newtonian. According to Newton, one star orbiting another will just continue to do so. Whereas according to Einstein, such a binary star system gradually looses energy by gravitational waves, and the effect of this on the periods of the orbits of binary pulsars has been measured. Tidal waves, too, have a motion perpendicular to the direction of propagagtion. Indeed ALL wave motions have that characteristic. How do you know a binary star sytemloses energy by gravitational waves IF gravitational waves have never been detected? Now come on! What frequencies are we looking for in gravitational waves? Fourier analysis allows us to calculate the harmonic overtones of motions of such waves given the ampliturde A and period 't' of one mass colliding with another Are you just parroting 'gravity waves' as you cliche other physical phenomena? You are also a very rude person, quite unsuited to be a 'Lecturer'
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Post by abacus9900 on Oct 18, 2010 21:09:21 GMT 1
It's almost as if she is quoting directly from some text in front of her doesn't it?
You see, if someone really knows their stuff thoroughly they should be able to explain it backwards or in any way necessary in order to make things clear. Sorry, STA doesn't seem to be able to accomplish this which does make me a little suspicious about her true credentials. Let's be honest, naymissus, all we see is text posted here by someone we don't know who could be claiming to be something they are not! Again, I wonder why an Oxford lecturer would bother to post to a MB after a hard day's lecturing to undergraduates. All a bit suspicious, if you ask me.
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Post by carnyx on Oct 18, 2010 21:35:50 GMT 1
I suspect STA is in fact a terminal in the JCR of a third-rate Uni ...an ex-PollyWollege of some kind. And who knows? -- perhaps olmy goes there.
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Post by abacus9900 on Oct 18, 2010 22:16:27 GMT 1
I suspect STA is in fact a terminal in the JCR of a third-rate Uni ...an ex-PollyWollege of some kind. And who knows? -- perhaps olmy goes there. Well, put it this way carnyx, all the famous and brilliant physicists I've seen on TV have always had the ability to put over complex ideas in a way that the ordinary person can understand. Ok, they dumb things down, but at least they give people a basic idea and if people wish to delve further then great. So, what I'm saying is that the brighter the teacher the easier it is to understand what they are trying to tell you, because they have the wit to see that people only need as much information as they can deal with at the time. If you are lecturing to an undergraduate class then, of course, that is an entirely different situation.
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Post by speakertoanimals on Oct 19, 2010 13:07:01 GMT 1
Wrong. Sound waves are longitudinal, rather than transverse. Hmm, let me see, some chaps won a Nobel prize for that............. It's quite simple really -- if system looses energy, orbits change, and that can be detected. So, predict how much energy lost by gravitational radiation if Einstein correct, predict change in orbital parameters, then go measure it. Predicted change was 76.5 microseconds a year, and here is measured values plotted with prediction: en.wikipedia.org/wiki/File:PSR_B1913%2B16_period_shift_graph.svgI prefer exceedingly rude................ Bollocks! (going for exceedingly rude you see!). We all know academics who are absolutely brilliant, world-leaders and so on, but being able to EXPLAIN their field is another matter. We have all had the utterly brilliant chap who spends an hour at the board, blocking what hen is writing, muttering inaudibly, and even in extreme cases, erasing what he has written before anyone can copy it down! In one brilliant case, I was at a conference with a french mathematician, who had to have a minder in the audience who said repeatedly 'english, professor' when the chap got excited and lapsed into his native tongue. When it comes to public engagement, most universities now admit that only few lecturers are actually ever going to be any good at this and presenting stuff to the general public is a very specific skill. As regards undergraduates, the feeling is that almost anyone should be able to do this, given a decent understanding of their subject and enough supervision, but this is not always the case. Except the blindingly obvious response is that the brilliant physicists that are just totally incomprehensible (even to their colleagues) are never going to get on TV. As I keep saying, explaining complex stuff to the masses so that they feel they understand something (even if they don't) is actually a very specialized skill, not (as some would argue on here) something that anyone who really understands the subject should be able to do. Indeed, it is daft to think that is the case (I blame whoever made that comment about explaining to an eight-year old -- ah, from Kurt Vonnegut cats Cradle: Dr. Hoenikker used to say that any scientist who couldn't explain to an eight-year-old what he was doing was a charlatan. This quote: If you can't explain something to a first year student, then you haven't really understood it. * Variant: "If you can't explain it to a six year old, you don't really understand it." has been attributed to Feynman (and Einstein), but there seems to be no reliable source as yet. ) Anyway, after that long parenthesis -- IF it were true, then all we would need to do is select the best people in a subject, and turn them into school teachers. Except we don't -- and often those that make the best teachers aren't those with the highest marks. We recognize that being able to explain and teach a subject to children is again a specialized skill, not something that follows on automatically from understanding it.
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