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Is the speed of light the same as the speed of gravity?
A new more accurate test is being carried out on Sunday to try and confirm whether or not this is true. The results of this potentially have far reaching implications, as this is the fundemental hypothesis for Einstein's general theory of relativity.
One or two sites have reported this, but I noticed it at news.bbc.co.uk/1/hi/sci/tech/2238452.stm
Interesting.
It could also open new doors on the "dark energies" and their interactions with gravity.
I have ever think the "anti-gravity" phenomenon which may keep on expanding the universe could also be a better physical basis than the speed of gravity.
I'll wait to know more about the results.
it takes light 8 1/2 min to travel aprox 93 million miles... if the sun could instantly turn off its gravitational pull it would take 8 1/2 min for us here on earth to feel the effect.
Very strange... I was under the impression that the assumption was that gravity effects moved instantaneously.
Quote:
From here.
Indeed, it is widely accepted, even if less widely known, that the speed of gravity in Newton's Universal Law is unconditionally infinite. (e.g., Misner et al., 1973, p.177) This is usually not mentioned in proximity to the statement that GR reduces to Newtonian gravity in the low-velocity, weak-field limit because of the obvious question it begs about how that can be true if the propagation speed in one model is the speed of light, and in the other model it is infinite.
Quote:
NFO Page
In the simple Newtonian model, gravity propagates instantaneously: the force exerted by a massive object points directly toward that object's present position. For example, even though the Sun is 500 light seconds from the Earth, Newtonian gravity describes a force on Earth directed towards the Sun's position "now," not its position 500 seconds ago. Putting a "light travel delay" (technically called "retardation") into Newtonian gravity would make orbits unstable, leading to predictions that clearly contradict Solar System observations.
ok...too put it simply, If I have a Ginormus Rope which is fastened at Point A, and I'm at Point B, the minute I let go at Point B, the rope will fall at Point A....
It's a stream of energy, If it is broken, it fall's on both side's :)
- Noia
PS: Dark Energy is related to Simple Harmonic Motion's
The important question about all of this is:
so where does this leave Star Trek?
Shiraz
thought this mite be of intrest to some of you out there
http://www.eutopia.no/Pawels.htm
In response to Terr's and pandora's posts, I'm not convinced that these conclusions are valid.
From a mathematical point of view, if you take Einstein's theories as a starting point, then you can derive Newton's equations from them, if you ignore the speed of light/gravitational speed. In mathematical terms you are disregarding second order parts of the equations, as for most practical purposes, they have no effect on earth.
Introducing 'retardation' into Newton's framework seems way off target, given that Einstein's model includes this, which is lost when you you change to a Newtonian framework.
The speed of light is app 186,000 miles a second. The affects of gravity appear to be instantly transmitted.
i know it may not be relevant but i have to ask what happens when i body(if it could) achieve speed equal or more than that of light , i know its mass will be infinite but than what will it explode or it will travel through time?
As you, say according to Einstein's theories this is not possible, because you would need an infinite amount of energy to get a body to the speed of light.Quote:
Originally posted here by dev_ocean
i know it may not be relevant but i have to ask what happens when i body(if it could) achieve speed equal or more than that of light , i know its mass will be infinite but than what will it explode or it will travel through time?
However, there has been speculation that certain fundemental particles can travel backwards in time - there have even been one or two scientific experiments that appear to show this to be true. Very strange!
The reason that gravity appears to be instantly transmitted, is that it is very difficult to destroy an object (star, planet etc.) - even if it expodes or becomes a black hole then it still has the same mass, and hence exerts the same gravitational affect (more or less). To some extent it is the 'more or less' bit that is being tested today.
well, the theories are just that - theories - and they don't explicitly forbid faster than light travel, so you can't say that it is not possible.Quote:
according to Einstein's theories this is not possible
on the particles traveling back in time...they are anti-particles traveling forward in time, same thing. for example, an anti-electron traveling forward in time (as they do) is the same as an electron traveling backwards in time. and you say darkes that there have been experiments that have proved this to be true. this i am not sure of, but i will go look in a minute. but if it is true, then it may be possible to construct an anti-gravity bubble(or a bubble of gluon particles traveling back in time) around a body, to shield it from the crushing centerfugal forces of gravity (or gluon praticles traveling forward in time) and attain a speed of that equal to or greater than the speed of light. in saying that though, anti-particles are supposed to anniliate particles, and vice-versa, so good luck trying to maintain that bubble.
but don't take my word for it, check it out yourself.
on your travels check out String Theory...another theory...around since the 60's...explains light as vibrations in the 5th dimension( with time as the forth dimension, the vibrations would be in the 5th, or the 4th spacial dimension), with gravity residing in a higher dimension. the fundamental belief with String Theory is that things simplify in higher dimensions.
ooh just remembered...didn't some guy encode music on a laser beam and make it travel 5 times faster than light? light has mass (because it is effected by gravity) just like we have mass, just alot more that a photon of light................
oooohOOOOOOH, last point to ponder. in StarTrek when they go to "warp" and travel faster than light, they are effectively TIME TRAVELLING!!!forward. aRRRRR, capt'n Kirk failed to carve this into his log.
The3ntropy said in his antipoint comment to me
"The speed of light is 166,666.6(repeating)"
Since this comment is entirely wrong I inquired who the sender was. This is his email back to me:
"I gave you negatives because you are providing false information. If you don't know something, keep your mouth shut. And if you want to post information and facts, look them up or know them before you do.
Also it was a one line post in an interesting thread."
__________________
--en·tro·py
1.) A measure of the disorder or randomness in a closed system.
2.) The tendency for all matter and energy in the universe to evolve toward a state of inert uniformity.
3.) Inevitable and steady deterioration of a system or society.
____________________________________________________________________
I admit my post was a one liner......poeple have a right to neg that if it's a post building ploy.
BUT the speed of light "166,666.6 (repeating)" ???
He is in need of some schooling. rotflmao
I Gave an approx. speed of 186,000 miles per second and that is the accepted constant for the speed of light.
the reason this is not possible is the same as the answer to your question... as a physical mass approached the speed of light, setting aside the fact that it would need an infinite amount of energy, the objects mass would decrease exponentially, before eventually disappearing altogether. hehe cool, huh?Quote:
Originally posted here by dev_ocean
i know it may not be relevant but i have to ask what happens when i body(if it could) achieve speed equal or more than that of light , i know its mass will be infinite but than what will it explode or it will travel through time?
and about gravity traveling at the same speed as light, yes the effects of gravity SEEM instantaneous, so do the effects of light to us, the speed is not within our perceptual range. that having been said, given what i know about light and gravity, i think light is actually slower, because light is waves, and gravity has to do with the movement of sub-atomic particles, which in the field of lasers, are emited by chemical lasers, which are said to be faster than normal lasers, which are light. i could be wrong.
Clearly if gravity *can* travel faster than light, then maybe we can use it to communicate with aliens too far away for EM radiation to reach them within our lifetimes.
Sure there might be minor technical issues with creating large enough gravity waves for aliens to recieve them :)
I suspect not however and I have read that it travels at exactly c
from some things i've read, gravity doesn't exactly "travel" at "speed".
it is one of the four fundamental forces in our physical universe, and is a cosmological side effect of a property that causes matter to attract other matter. hence gravity forms a 'field' around large bodys, whose effects are felt less the farther away from the large body you are.
gravity does not suddenly "travel" to one side of a large body, making gravitys effects on that side stronger. nor does it "travel" out into space. its more like a dense fog, that thins and clears the further away from the large body you go.
http://www.ldolphin.org/vanFlandern/gravityspeed.htmlQuote:
Standard experimental techniques exist to determine the propagation speed of forces. When we apply these techniques to gravity, they all yield propagation speeds too great to measure, substantially faster than lightspeed. This is because gravity, in contrast to light, has no detectable aberration or propagation delay for its action, even for cases (such as binary pulsars) where sources of gravity accelerate significantly during the light time from source to target By contrast, the finite propagation speed of light causes radiation pressure forces to have a non-radial component causing orbits to decay (the "Poynting-Robertson effect"); but gravity has no counterpart force proportional to v/c to first order. General relativity (GR) explains these features by suggesting that gravitation (unlike electromagnetic forces) is a pure geometric effect of curved space-time, not a force of nature that propagates.
So it seems to have been determined by experiment that gravity is detected
instantaneously, and not with a delay, which could be measured if it only
exerted its effects at the speed of light. So, even though the strength
of the gravitational field is weaker with distance, you could still instantly
detect motion in a distant object because its gravitational pull would be from
its new position as soon as it moved, and not with a delay.
So, maybe with this knowledge, we could fashion a communication technology
that would communicate without the limitation of light speed. This would have to be
made practical before you could ever hope to talk to aliens in distant galaxies.
What good would it be for them to recieve your transmission many lifetimes
after it was sent?
:cool:
the spoeed of light may be 186,262 miles per second but the effects of gravity are not instantaneous as it depends on where you are in the universe, the laws that relate to relativity are based on a universal rule not bound by here on earth !
just thought i would point that out as a few of the posts are assuming the rules that apply here on earth ! Which are based on the earths mass and the moon and the sun etc etc !
Ok folks here's my two cents on the subject . . . I see gravity commonly referred to as a force but it really better thought of as a "weak" effect of attraction between masses. All masses, visible or not, are effecting all others simultaneously. The problem is that gravity, being "weak" is effected greatly by the distance between masses; it becomes an "observable" effect in the local vicinity of the mass.
There are still weird things we don't understand about the whole mess. For example, our galaxy Milky Way is in a cluster of galaxies called the Virgo cluster which includes, I believe M81, the Andromeda galaxy and maybe 4 other galaxies in the same general vicinity of space. As with all other observable matter, the whole Virgo cluster is hurtling thru space away from the "center" of the Universe. The issue is that the Andromeda galaxy has been observed to be accelerating towards Milky Way. A look towards the acceleration vector, for the source of this effect, is empty space. Impossible. So the scientists have placed a massive object where none can be seen called "the Big Kahuna". Meanwhile M81 will collide with Milky Way in some odd billion years on it's way to "the Big Kahuna". I don't know about you, but I am really perplexed by this observation.
Something to think about: how could a black hole prevent light from escaping if gravity was constrained to the speed of light? Must it not be capable of imparting a vector acceleration greater than the speed of light (simultaneous qualifies here) opposite to the photon's vector of travel?
Just something I thought... If gravity moves instantly, why does gravity "fade out" the further away it get's. I mean Jupiter pulls on us, if I jump Jupiter pulls me up or down or whatever, but because it's so far away and our own earth so close, we will not feel it, if it's even there. If it traveled instantly it has to have resistance in some way.
Also if you pull a rope two ways, and you release one end it won't instantly move sideways. The rope has a mass wich has to gain some speed first wich needs a force (you) and energy. It takes time for the rope to actually start moving.
Another thing, Einstein and a lot of other people based these theories on their experience, thoughts and test. They're still theories though. Something is true if it's not not true and you never know that for sure. It also could just be a big mess of nonsence. Who made the idea of a forth, fifth etc. dimension. Who says that even exists. Do we have prove that we live in a three dimensional world anyway. If time is a forth dimension something and we experience it in this dimension, then mass has to be in higher dimensions to. If you think about it a bit it's almost stupid to call length or hight a dimension. Of course there have been many test and experiments. Somehow people got some effect in the 9th dimension or something.
Maybe it's just a weird idea of humans. Also if you make a list of dimensions like this :
dimension 1
dimension 2
dimension 3
what would be here:
dimension 1,1 dimension 1,2 dimension 1,3
dimension 2,1
dimension 3,1
or even in a "third" dimension etc. etc.
Just some thoughts of me... hope it made some sence
Neel
Hrm everyohne is saying the results of gravity are instantaneous...but is that with the light we already have here. or do we have to wait for the light to come from the object that causes the gravitational pull to see the affects?
"Put your hand on a hot stove for a minute, and it seems like an hour. Sit with a pretty girl for an hour, and it seems like a minute. That's relativity."
-Albert Einstein-
It's not all that relavent to this discussion, but I thought I'd share it anyways. Such a splended little quote.
Take care,
::Chelle::
"Put your hand on a hot stove for a minute, and it seems like an hour. Sit with a pretty girl for an hour, and it seems like a minute. That's relativity."
-Albert Einstein-
It's not all that relavent to this discussion, but I thought I'd share it anyways. Such a splended little quote.
Take care,
::Chelle::
The Gravitational force is the weakest of the four fundamental forces, but the one with the longest range. Scientiest theorize that each of our thoughts, with electrical impulses and chemical reactions, cause a small gravitational shift that has a ripple effect on the universe. Of course this effect in impossible small, but if we could build a device capable of detecting these tiny changes, perhaps a mind-reading machine could be built... weird stuff.
Alright. A few words on Gravity.
First, to address a few questions in Neel's post.
Gravity does not 'fade out', per se.
Gravity is the force of attraction between two masses. It is proportional to the mass of each of the bodies, and to the distance between them. It's expressed by the following formula: F == ((G*m*n) / r^2 )
Where F is the force, G is the Gravitational Constant, m and n are the associated masses, and r is the distance between them.
G == 6.67259*10^-11 N*m^2/kg^2, assuming the Kilogram-Meter-Second system of measurements.
The reason for the lessening effects of gravity over a distance can be visualized if you think of gravity as operating as lines of force. The closer to the body that the lines are, the denser they are. As they travel outward, they spread apart, and anything that they act upon will be acted on by fewer of the lines, as it were, than a closer body.
With the tug on the rope--you're confusing gravity and inertia. In order for the metaphor to hold, you have to use an imaginary sort of rope--one with no mass, and no tendency to stretch. A better example might be a metal rod that you're only allowed to pull. The free end of the rod will move instantly with any force on the other end, as the two ends are connected ridgidly. Being massless, there's no inertia to worry about.
Now, I'm fairly sure that the concept of the speed of propogation of the gravitational force is pretty much meaningless. After all, according to the law of conservation of matter and energy, the total amount in the universe must remain constant. Believe it or not, energy also affects gravity. If you were to turn a pound of bananas into energy, a pure conversion, and contain this energy, it would still have the same 'mass' as the bananas did.
Thus, in order to measure such a propogation, would one not have to create some sort of mass, and then measure it's effects on the rest of the universe? It's not terribly likely that that's going to happen, assuming that the laws of physics stay constant.
What they could be measuring, instead, is the propogation of gravity waves. These are fluctuations in the gravitational field, brought on by moving masses. Think of it like a couple of ducks swimming in a pond. The wakes that they leave will collide, and cause all manner of interesting patterns.
For those who are interested, the results are in.
Einstein was correct - gravity does travel at the same speed as light.
It is definitely not an instantaneous force, so his General theory of relativity still holds good.
There are reports in the scientific newsletters, but a brief summary can be found at http://newsvote.bbc.co.uk/1/hi/sci/tech/2639043.stm ,which also has the links to the other journals.