BBC Relativity Slip-up

Boy what I would give for a space-time curvature straightener!

I thought it was that mass created the curvature of spacetime through the action of gravity.

But surely it works in reverse, most of these things do. Curvature causes gravitational-like effects through its deflection of the geodesics, so can spacetime be curved without mass? Either curved spacetime create mass, so that all mass is simply the result of a convoluted and possible higher dimension spacetime, or gravity can exist without mass.

Im getting confused...

Quote: "I thought it was that mass created the curvature of spacetime through the action of gravity."

Closer to mark would be: "mass (or energy) creates curvature of spacetime, which manifests itself as gravity." I believe that there cannot be gravity without mass or energy (through E = mc^2).

So gravity can be explained as geometry. But what if the geometry was there to start with? In the absence of matter, spacetime must be absolutely flat, or there would then appear to be gravity without mass.

Has anyone thought about this yet?

Jorrie; Just a comment; Quantification of Curosity Should Indicate IQ. Curiosity value is higher the smarter a person is. It is easily seen in children. Thanks for the read: Fris.

"Gravity is caused by space-time curvature, yes, but mass? What do you think?"

Is this true, or is space-time curvature caused by gravity?

I have always been under the impression, purely from my education and not from my own theories or research, that the attractive force between two objects is a function of their masses and distance between their centers of mass.

Which came first, the chicken or the egg?

The chicken: its only takes 1 egg to make one chicken, but 2 chickens to make one egg

Actually:

The chicken: It only takes 1 egg to make one chicken, 1 chicken to make 1 egg,

but 2 chickens to make one egg, that will make 1 chicken.

Is this scaleable? If one chicken can make one egg and two chickens can only make one egg, what happens if there are three chickens. Four, five, six... eight million three hundred twenty thousand six chickens? Beyond that I don't care.

Luckily I prefer beef. Otherwise the 'two chickens to make one', logically leading to chick-stinction would scare me. In any case, the egg came first because dinosaurs used that technology, too.

As to space-time and the stuff around it. IMnsHO gravity, the wave, arises from atoms themselves. Concepts like space-time curvature explain the viewed physical results by trying to apply form to the grid itself. Sort of like saying, "according to the formula the stock market should have risen, but didn't, so the graph paper has a fold in it."

At the risk of sounding like the guy with the software-driven morphing triangles, gravity is just the resulting incoherent wave caused by electrons orbiting protons. Like all waves, it does not 'travel', rather occurs everywhere at once. Unlike light it does not seem to decompose (or 're-compose' depending upon your point of view) into matter with a finite speed and which we can perceive.

Quoting 'jdst': "... gravity, the wave, arises from atoms themselves ..... gravity is just the resulting incoherent wave caused by electrons orbiting protons. Like all waves, it does not 'travel', rather occurs everywhere at once."

To me it sounds like you are mixing up gravity and gravitational waves. Mainstream physics holds that what we call gravity is essentially a static field - no propagation. Disturbances in that field are called gravitational waves that propagate at the speed of light. And gravity caused by orbiting electrons...?

If you know about scientific literature that says this, I would love to know about them!

Actually I know very little. But there is a possibility things are as simple as they seem at first. I sort of object to the quantum physics guys and their "Theory of Everything" attitude that after a couple of thousand years of studying a 4 billion-year-old (as far as we can tell) universe, they can bring it all down to some bizarre math.

The more I hear from Hawking and his compatriots - who I will admit are w-a-y more brilliant than I - the more I see three blind guys and an elephant.

Take, for example, the big bang. Maybe our bang is like one of the hundreds of sparkles in a fireworks display. We haven't been around long enough to see far enough outside the sphere of our own small burst to realize we are one of many, many small bursts derived from several much larger bursts, which, themselves came from one giant burst after the package rocketed up into the evening sky.

And then there's the guy on the ground with a bunch more rockets - some the same and some quite different.

Hi Jorrie, ahah! you have posed one of the BIG questions, NASA I believe are scheduling an experiment to test for gravitational anisotropy, which apparently varies with orientation in space. Visitor to MIT Plasma Science and Fusion Center, Mikhail Gersheyn, well and truely upset the apple cart again, by demonstrating anisotropy. Sir Isaac Newton, was unable to determine if the force of gravity was a pull or a push? I have that funny feeling in my bones, that a few decades from now, physics teachers will be deriding 20th century science as the sad misguided century where they may be telling their students;

"In those days, ignorant fools disregarded the 'ether' which of course we all now know is responsible for the anisotropy of the gravitational 'push' ...some deluded scientists, if you can forgive us for calling such ignorant stupid fools 'scientists' even went so far as to declare that gravity was a constant! "(Much laughter from the students)....We shall see?

As usual I had to run off and look stuff up after reading a post.

Hyperdictionary tells me that 'anistropy' means directional. Well, of course gravity is directional - in the Northern Hemisphere it makes everything fall down, and in the Southern things fall up.

If gravity worked in all directions it would cancel itself out, wouldn't it?

Ahah! A man after my own heart, research always pays off, ahem!...correction...NASA may be scheduling a mission to try to detect if a 'variation' in gravitational 'anistropy' exists. i.e. The 'push' hypothesis is akin to a pressure being applied from all directions, but when two objects are close they are pushed together, not pulled. There are dozens of links on the net, some more 'Off the Wall' than others, but generally the maths holds up.

A joke from the floor of the 1997 University Of Memphis sponsored conference of the American Mathematical Society: "A Physicist and a mathematician are flying cross-country together. Each is keeping a diary of the trip. They fly over a white horse in Iowa, The physicist writes, 'There is a white horse in Iowa.' The mathematician writes, 'There exists, somewhere in the Midwest, a horse, white on top.' "

So what about plasma? As the electrons are no longer orbiting the protons does that mean that the plasma has no mass?

Surely it does travel, thats called a gravitational wave. If it occured instantaneously it would mean that an event could occur before the information being transmitted from the thing that caused it (make the spacetime diagram and see), so it must travel at the speed of light.

If gravity travelled faster or slower than light, imagine how it would affect spacetime curvature. Shocking.

Quoting mysticgohan: "So what about plasma? As the electrons are no longer orbiting the protons does that mean that the plasma has no mass?"

I'm not too sure to which post you are replying. In my post #25 above, I frowned upon it too: "And gravity caused by orbiting electrons...?" This is a fairly obvious fallacy!

Yes, changes in gravity propagates at the speed of light, but if there is nothing disturbing a mass in it's orbital free-fall equilibrium, the gravitational field seems to follow the mass without deformation, i.e., apparently instantaneously.

Re:- "Changes in gravity propagates at the speed of light" Fascinating, I would be thrilled to know how it was measured. Did they calculate it from astronomical observations? or was it a 'lab' experriment?

I saw a great lab experiment, recently on the net from GlobalSpec. Two large perforated cylinders of brass. The top one suspended just a fraction from the lower and set slowly spinning, it was observed that when the six holes alligned, a laser reflected off a pollished surface detected a minute perturbation. I believe results will not be available for quite some time.

Re:- "I would be thrilled to know how it was measured. Did they calculate it from astronomical observations? or was it a 'lab' experiment?"

Gravitational waves have not been detected directly yet. There are BIG projects going to do just that, i.e. LIGO and LISA. In observing pulsars with companion stars, astronomers were able to observe the loss of orbital energy of the pair due to the radiation of gravitational waves. This agreed very well with Einstein's relativity theory, so one can expect that the speed of gravitational waves will also agree with Einstein's prediction - "c". There's a whole chapter on gravitational waves and their detection in my eBook and website.

Thanks Jorrie, your link has gone streight to my 'Favourites' ...Well Smart Website, as we would say in Lancashire. As an aside, I checked out LISA, almost as soon as I got on broadband, what do I find? portrait photographs of the family! displaying very trim Victorian waists. The 'L' & 'I' stand for Long Island. Grandson of the trim Lady,(The Princess Royal) celebrated his birthday yesterday, and so did our Prime Minister's Wife. Jamie Fife's pater was fascinated all his life with things cosmological. He also shared the same birthday. 23rd Sept. One project that Charles Southesk, James Fife's father, would have liked to promote, would have been for a 'Sea Urchin' of regular telephoto lenses (reflex) mounted on standard camera bodies, located at several observatories, to constantly monitor the heavens. Now that high definition digital is with us, who knows? It might make a rather fine website to log onto? I note we have just witnessed the first supernova from zero hour. We could so easilly have missed it starting.

("Über einen die Erzeugung und Verwandlung des Lichtes betreffenden heuristischen Gesichtspunkt"), The Paper Albert Einstein won his Nobel Prize for. on the Photoelectric Effect. No prizes for guessing in who's honour this observatory proposal is intended to celebrate. A 360 degree panoramic view of our cosmos 24:7:365.

No.

But if I were right, then plasma would not generate gravity itself. I would assume a way to test that would be to measure the attraction between, say Earth and a container filled with whatever, turn the whatever into plasma and see if the attraction changes.

As my rather simple mind understands it, mass exists whether or not it is being affected by gravity. In other words, being shot by a bullet on earth or on the moon hurts as much even though the bullet weighs considerably less on the moon.

Quote: "But if I were right, then plasma would not generate gravity itself. I would assume a way to test that would be to measure the attraction between, say Earth and a container filled with whatever, turn the whatever into plasma and see if the attraction changes."

Basically, plasma is mass and all mass generates gravity (or rather spacetime curvature) to some degree or other. Weight is not a property of a body, because it depends on the strength of the gravitational field. Mass (more precisely, rest mass) is a property of the body, independent of any gravitational field.