Space Time and Gravity

[xelasnave]

I am fascinated by gravity and enjoy my own unusual ideas as some of you who know me already know.
The concept of space time seems to me to provide a geometric explanation of gravity and I think I must be missing something and ask does anyone have a concept of how gravity actually works..that is how does one object communicate with another its "being there" (without using the rubber sheet and the bowling ball explanation if possible).
alex

[sheeny (Al)]

Good question Alex!

The only other concept I've heard about other than the rubber sheet analogy is the graviton particle theory. In practice they are probably the same... at least until experiment can distinguish one from the other, and see which one is closer to reality.

I'm not sure that I'm particularly up to date on gravitational theory or particle physics, but I believe the graviton is predicted by one or more theories but hasn't been detected . Is that right?

...of course there's always the old faithful "Gravity sucks" theory!

Al.

[AGarvin]

Hi fellas,

There is really only one viable theory of gravity and that's Einsteins General Theory of Relativity, which says that space curves in the presence of mass. The greater the mass, the greater the curvature. The "ball on rubber sheet" analogy is a sometimes confusing way it illustrate this concept.

Also, one of the underlying concepts of GR is the principle of equivalence, that is, being in a gravitation field, such as standing on the surface of the earth, is equivalent to uniform acceleration. Based on this, gravity is like rolling down a hill of space. The greater the mass, the steeper the hill gets the closer you get to the "bottom" (ie, the source) and the faster you go.

The idea of the graviton comes from Quantum Mechanics. In QM, everything has to be quantised. Just as the photon is a quanta of electromagnetic radiation and the gluon is a quanta of the strong nuclear force, so to gravity must be quantised. Under this theory, gravity would be the exchange of gravitons between masses.

Unfortunately, the mathematics of both theories fall apart trying to explain this, GR at small scales around the Planck length, and QM just all over.

Cheers,
Andrew.

[xelasnave]

Thank you very much for your interest and input. I like the sound of the QM approach as I guess it is this physical interaction that I am trying to nail down. It is how the messages are conveyed by the not yet found particles I find interesting. I can not get my head around the "mass curves space concept" and it is not for the want of trying.
alex

[robagar]

um, the GR equivalence principle states that gravity is indistinguishable from acceleration.

I don't like the bowling ball on the rubber sheet thing either. Apart from the fact that the emphasis is on the third dimension (ie down) when it's supposed to be a 2D model, it also appears to rely on gravity itself to to pull the marble or whatever in towards the bowling ball.

Not that I have any better way of visualising curvature of 4D spacetime I'm afraid :-/

[AGarvin]

um, the GR equivalence principle states that gravity is indistinguishable from acceleration.

Indeed I should have chosen my words more accurately and have corrected my original post accordingly. What I should have said was non-inertial motion. Why I simply didn't say acceleration ....

[sheeny (Al)]

Alex,

An interesting book to read is "The Elegant Universe" - it's also available as a DVD (I have both). It tries to cover a lot of the GR / QM unification work that is being attempted by string and brane theory in layman's terms. I'll post more details if interested when I get home and have access to the book.

Like all attempts to explain extreme physics/maths in layman's terms it has to make assumptions about what the reader/viewer knows and also some approximations to simplify concepts, but I think it does a reasonable job. There are holes in the explanation where I don't understand things, and there are other bits that, for me, are a bit over simplified, but on the whole it's not bad.

Al.

[robagar]

btw, yesterday was the 87th anniversary of the first observation of gravitational deflection of starlight by Arthur Eddington, the first experimental evidence for curved spacetime

[josh (Luke)]

Gravity is one of the signs that the universe is putting the breaks on after the bang.It wants to put itself back together again.
Perhaps it will all be drawn back together and squished after all.

[xelasnave]

Thank you all for your interest. My curiosity is how the gravity message gets from one object to another. I have notions that "star light" provides a universal radiation pressure, a pushing force which is observed as an attraction between objects. My thoughts are gravity results from an imbalance in the pressure caused by one object shielding another from the "universal pressure". Without formulea or experimental observation and prediction my idea in simply an idea. But how it really works (if different to my idea ) I would like to understand. what "things" travel between stuff to trigger gravity.
alex

[Starcrazzy]

hmmm...don't know about that...any "pressure sheilding "would surely accumulate at the fringes of galaxies and indeed the universe causing areas of Less pressure and therefore less gravity..And also your theroy doesn't account for the vector of gravity..the direction in which the force acts..Like the out of the box thinkin but...There are some that believe gravity leaks into other dimensions which is why its such a weak force (compared to the other 3) which would give us a way of communicating between dimensions..There are serious attempts underway to capture a "gravity Particle"..As far as i know they have yet succeded..

[xelasnave]

Believe me if we got to chat I can answer all
alex

[Starcrazzy]

exellent...would love to hear it mate...i have had an ongoing umm, lets call it a debate, with a really really clever bloke..its been going on for about 3 years..we are debateing the age of the earth, of the universe for that matter...He is a YOUNG EARTHER...he believes the bible tells the real creation story, and puts the age of the earth at around 5000 years...an easy thingg to disprove i hear you say...well...this guy keeps the argument going by putting the science that i use into question...i say things like, carbon dateing, the decaying of beta particles of certain atoms over time...he will say stuff like, yea, but that method would need a constant level of radioactive particles in the environment over the entire time...aarrrgghhh....its been going on fer years...we both love the challenge...so...don't be afraid to post a long post explaining your theory...i have found that in trying to explain something to someone else often helps clear it up for myself aswlell...does that make any sence??

[xelasnave]

Dont encourage him or you wont get rid of him .... have you ever followed those instructions? I pursued my ideas on astronomydaily.com (black hole forum) and I feel that my work to date in the area entitles me to the title of crackpot.
I simply feel that the ideas about gravity does little to explain its workings and with the current approach needing dark matter to make everything work I felt the world needed direction ..so hence my input.
I fancied that the number of photons and minute particles (dust nature) and atomic particles may be enough to form a pressure.. I call it gravity rain to demonstrate how we would be pressed to the surface by the inflow of stuff...it comes from the other side of the planet also but the pressure from that side reduced because of the presence of the planet. If you think about it at any point and every point there is there will be particles from every point of the Universe passing thru it at C at every direction, from every direction, from everywhere... I feel there would exist a resultant pressure. In true Morosophic fashion I can fit anything into this idea, optics and momentum are easilty explained
There is plenty to sink it but I use it in an effort to find someone who can explain in a nuts and bolts fashion how gravity works ... so far my idea is the only "nuts" and bolts model I can find.
alex

[Starcrazzy]

exellent...love it...have yopu heard of the casimir effect??
if ya havn't..google it..u will love it...it sort of fits with your theory and is a well documented and experimentally proven effect relating to the zero point energy of the universe, which is from my understanding, what your sort of prodding at...I however have a problem with this line of thought...because einstein's energy matter equivilance formula's dictate that energy as well as matter would cause a warp in fabric of space time..and if there is all this zero point energy and it is in the abundance that they say it is, well then the universe would be looped back in on itself...sort of like a massive black hole??not sure if thats the exact way to put it, but there it is...my problem ina nuts and bolts fasion(well nearly)..Basically a cosmic "pressure" in my humble opinion, wpould cause major problems with the warping of spacetime...
Ps, i could be wrong but isn't the universe's expansion accelerating at the fringes??Even all the theoretical dark matter can't seem to put the brake on??dunno...what do ya think??

[xelasnave]

Yes I know of the effect.
As to space time what are we talking about here, after all my looking into it, I find space time is described as ..similar to a pythagras theorum (to demomstrate lenght depth and high) with a "negative" time line. I am not sure that it exists in th ereal world an is little more than a math description of an unreal world that never the les can be described and measured by "space time".. the curvature seems to me a decription of how to calculate distance taking into account c.. I would like to hear a description of how matter warps space time... the rubber sheet seems to me to use the very thing (gravity ) it seeks to describe as if it were irrelevant and un noticed in the role play.
I see no reason to find a physical looping back of the Universe upon itself if such pressure were found to be more significant than currently thought. That is a dictate of the math known to this point however I think there is always an implication that there can always be more to the story. I mean I am only trying to describe how all the Universe works in complete contadiction to current cosmology so there will be a few loose ends. However as far as the gravity idea goes I say this. If you open your mind to the proposition it makes sense ..My system gets rid of the necessity of dark matter and would explain why locally galaxies are being pushed together yet at a ceratin distance the Universal pressure is able to act so as to force them apart. I recon the Cosmological Constant may have been an attempt to describe the pushing force (I predict) however Eienstein had to drop it when Hubble came out with "facts"... his observations of galxy recession. I wonder how he may have developed the idea if timing had been different. Radiation pressure is considered now although only somwhat locally in Super Nova ( and after) situations. However radiation is not insignifficant.. recently 20% more of some kind was found to exsist which to me underlined the imporance of this form of energy within the Universe.
When pushed to determine the edge of the Universe few will say there is one, however there is nothing beyond the Universe..so we have something without sides top or bottom..limitless. However if there is nothing on the outside or indeed no outside I ask into what is the Universe expanding, a difficult problem as there is nothing beyond our Universe (so they say). Space does no exsist for a billion light years and then we get to a fence on the other side of which we find..nothing?? cant happen. I have difficulty with the Observations that lead us to see the Universe as Expanding as the question to my mind is "if it is expanding..to where does it expand?" "Into what". There can be no such thing as "nothing" only "space" which covers all over so where can it expand to?? Now we need some fast talking to get past that point.
As to where we may find the fringe of the Universe I dont know. Last I heard was the Universe is 160 billion light years across a distance covered in 13 billion light years..yet at 160 billion light years as a chosen dimention is it expanding into billions of light years of "nothing".
The current explanations call upon some difficult propositions so the difficult proposition I ask one to consider as to the possible opperation of gravity in the manner I present.. in that context I feel it is not that outrageous..
I can see no begining or end to space and feel what ever perception we may have that space is expanding may be wrong, we may be witnessing nothing more than a local "eddy" past which things are different and reveal the Universe as we cant see it.
alex
alex

[Starcrazzy]

Ok..ok..im hitting the hey now, iwill postulate a retort (lol) as i slip into slumber..But a quick note before i go, a good example of matter warping space can be found in the experiments with distant stars being acculted by large masses such as planets, other stars, galaxies and of course, your old friend,,,the black hole..or do you mean to say that the pressure wave is what causes the difraction??in a sort of particle capture mechanism??hmmmm...no sleep for me tonight...
cheers
ps..have you read hawkings latest book...the universe in a nutshell??you probably have, but if not, i will loan you my copy...you'll get a kick out of it

[xelasnave]

Think of the pressure from all directions caused by stuff travelling at c as light passes an object Sun, Black Hole or Galaxy such object sheilds the "particles" with the result that the greater presence of particles from the "exposed" side.. the light is accordingly pushed to the area of less pressure (gravity effect). Now I know Dr Eienstein has an idea on this also so you have the rubber sheet is doing it or the "particle" pressure is doing it. It is called an Aristotleian approach but hey I dont make decisions that affect anyone so what the heck. Mmmm book on the Universe I was going to write one but what the heck I could read one instead. Thanks.
Steven Hawkins approach to the Universe is similar to the Pope.. both models have a beggining and an end one model took 7 days for initial creation and the other model 300,000 years one model says the clock has run for 13.5 billion years and the other model says it has run for 6000 years. Personally I recon if we find there is a God behind all this there would be no start or finish which is very mortal in conception, for if it is not this way we will have to look for where "he/she/it/all" grew up.
alex
alex

[Starcrazzy]

oh yea..im startin to smell what ya cookin...with it coming from all directions that would explain why the effects are uniform on both sides of a planet and so forth hey??very clever..ok..so it seems in order to see if the theory hold up i reckon we need to reverse the time line back to some time after the big bang...around the time when light started to shine..so we would have an incrdeibally dence and hot region full with this immense "pressure" from particles hitting eachother at c..now..it is known that the effects of Gravity weren't strong enough to contain the outward expansion of all these particles..if your theory wwere correct then all particles in this dense soup wopuld have anearly infinate sheilding from all the other particles causeinfg an infinate force of "g"..OR..the partcles would not be sheilded enough because of the massive amounts of "c" travelling particles which would cause the early universe to expand out in a puff and not allow thwe gradual concraction of matter to form thwe stuff we love looking at so much...im not sure which one (if either) would be correct...but whatever the mechanism of gravity, it wasn't strong enough in the early universe to contain all the partlcles after the big bang, and for a pressure sheilding situation surely the pressure in this eraly stage would have been ginormous....dunno...but its great fun ..
ps..as for the age of the universe thing....don't get me start6ed...lol....

[xelasnave]

I find it understandable that humans must have "a start" and not to have one seems beyond comprehension, however I say why not.
We all except almost without question that it is possible for the "seed" of the Universe to appear from nowhere in "nothing" and in that nothing created "space" and without further input of energy or matter or any other thing being added from "outside" , and thereupon to expand at an inconceivably rate which would see its "edges" if it had them travelling at many times the speed of light (if there was anything we could relate the speed to that is and of course there isnt???)...To me, after many years of seeing the wisdom in the theory, when it is put as I have done so above, and it be a fair statement generally, I dont think a Universe without a begining is any stranger than the current view that all there is can fit on the head of a pin at T plus .000000001 secs after "ignition". It is a long time ago so who knows really what happened how it happened (let alone why it happened if it took place that way). I know what they know but I recall steady state was the rock solid view maybe 30 years ago for many scientists... oh the olden days when we were savages? my point is the world was once flat and it took a crack pot to point out the misconception and also why those of high intelligence were fooled by the "view" of their then "observable Universe".
I liked your thoughts to fit it into the big bang plan. You certainly seem to grasp what I am trying to convey. Think about gravity lensing to get the idea quickly.
AND a qualification.. although I am seriously interested in "everything" and perhaps more in "nothing" (and the implications of the difference between nothing and "space") and above all gravity, at my age I dont give my soul to any stand.. things change new things get discovered etc ..but I enjoy a chat
Thanks for your interest and input.
alex