The Speed of gravity

[john937]

The Speed of Gravity

A while back there was a thread about "What was faster? Sound, Light, or Gravity?"
http://boards.elitefitness.com/forum/showthread.php?s=&threadid=60602
The thread quickly degenerated into personal attacks with several members stating they thought gravity had no speed, that it was instantaneous.
They were wrong:
Speed of Gravity Measured for First Time
Wed Jan 8, 8:45 AM ET

By Robert Roy Britt
Senior Science Writer, SPACE.com



SEATTLE - The first accurate measurement ever taken of the speed with which
gravity propagates shows that it is equal to the speed of light, agreeing nicely with
the General Theory of Relativity.

You may or may not have ever considered whether gravity has speed. It is of great
concern to scientists. Newton thought gravity's force worked instantaneously.
Einstein thought it took effect at light speed.

Here's a way to think of the difference:

Though fast, light takes time to travel. If the Sun suddenly disappeared, it would
take about 8.3 minutes before daylight on Earth would evaporate. With the Sun gone,
gravity would cease to keep Earth in a circular orbit, and it would fly away.

If gravity works instantly, Earth would fly away the moment the Sun disappeared. If
gravity works at light speed, Earth's course would not change until 8.3 minutes
later.

Sergei Kopeikin of the University of Missouri, Columbia, and Ed Fomalont of the
National Radio Astronomy Observatory devised a clever experiment to test which of
the two assumptions is right. On several days last September, they observed a
faraway galaxy as the planet Jupiter passed near it in the sky.

Jupiter's gravity would bend the light ever so slightly, they knew. The question was
by how much. Theory predicted two separate circles, slightly offset from one another,
that the galaxy should appear to describe on the sky as Jupiter got close, closer, and
then moved away.

The results show, within a 20 percent margin of error, that gravity worked at the
speed of light. The finding was announced here today at a meeting of the American
Astronomical Society.

"We now know that the speed of gravity is probably equal to the speed of light,"
Fomalont said. "And we can confidently exclude any speed for gravity that is over
twice that of light."

That gravity works instantaneously is almost impossible, according to the study.

 

[HumorMe]

*scratches nuts* hmmmm

*reaches for my pen and my book of useless information*

*writes down new information*

*puts book back on shelf*

Next...........

 

[Imnotdutch]

My first response was gravity can't have a speed.........but the post is interesting. Is there a reasonably simple explanation as to why gravity has a speed? (I know thats prob a big question).

 

[PoyeBoy]

whats the speed of milk?

 

[Bullit]

So you've been researching this since Sept and thats all u got?
Ain't you something!

 

[Norman Bates]

My first response was gravity can't have a speed.........but the post is interesting. Is there a reasonably simple explanation as to why gravity has a speed? (I know thats prob a big question).

Forces are transferred by particles, these have to travel so that forces have effect.
Since nothing can travel faster than light speed gravity should only work with light speed at best.
The problem was that the graviton hasn´t been found so far.

That´s at least what i read in some popular science report.

and no stupid star wars jokes now

 

[john937]

So you've been researching this since Sept and thats all u got?
Ain't you something!

The amazing part is that I even remember last September ever happened.

 

[bullett]

It is generally assumed that the graviton moves at the speed of light....

ANd btw, scientists have already proved that acceleration beyond the speed of light is indeed possible.

 

[Norman Bates]

ANd btw, scientists have already proved that acceleration beyond the speed of light is indeed possible.

Can u explain some more?

 

[Imnotdutch]

Interesting reading.......

http://www.school-for-champions.com/science/gravity.htm

Speed has units of metres per second........how do you get that from the units for mass and acceleration? I know that I'm being thick.......its almost midnight here .

I understand that the object is being accelerated towards Earth (and every other object for that matter) due to gravitational force. However I am struggling to see how gravity itself has can have a speed..........geez I'm gonna have to figure this all out now

Oh and somebody tell me what a graviton is EXACTLY..........thanks.

I'm confused. We've known for a long time that The force of gravity on an object caused by the mass of the Earth equals the mass of the object (m) times the acceleration caused by gravity (g), or F = mg

Acceleration caused by gravity on Earth (the acceleration of gravity) equals 32 ft/s2 .

The weight of an object is the measurement of the force of gravity on that object. Force is created from increased acceleration, so how would gravity NOT have speed?

 

[Norman Bates]

So far, there are four basic forces in the universe:
gravitation, electromagnetism, the weak and the strong Kernkraft ( don´t know the English term).
Scientists have found out that the electromagnetic force is transferred by photons, the weak by some particles they called Z-particles and the strong by some other particle which name i forgot.

Everyone of these particles that transfer the force have been shown in experiments , except the graviton.
Most scientists believe therefore that some graviton exists that transfers gravitation, but they have not been able to find it yet.

 

[Mdguy]

You have to remember that gravity is a FORCE FIELD similar to a Magnetic Field (B) or an Electric Field (E). A force field is composed a particles that move around in a path defined by the physics of the situation and have a velocity. (the term 'speed' does not take into account direction as those who took physics should have learned) I think this is the speed they are talking about. They postulate that these particles are gravitrons. I'm not up on current physics so I don't recall if they've been found to exist or not.
I think Einstein postulated that these gravity lines have 4 dimensions in his General Theory of Relativity.

Now onto the topic of conholing...

 

[Norman Bates]

I'm confused. We've known for a long time that The force of gravity on an object caused by the mass of the Earth equals the mass of the object (m) times the acceleration caused by gravity (g), or F = mg

Acceleration caused by gravity on Earth (the acceleration of gravity) equals 32 ft/s2 .

The weight of an object is the measurement of the force of gravity on that object. Force is created from increased acceleration, so how would gravity NOT have speed?

I don´t think you can transfer Newton´s macrophysic on nuclearphysics.

 

[Code]

I don´t think you can transfer Newton´s macrophysic on nuclearphysics.

Newtonian, Nuclear and quantum physics are generally not interchangable.

 

[minion]

http://www.ldolphin.org/vanFlandern/gravityspeed.html

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.

More on the link

 

[Testosterone boy]

Alll I know is that we will have to invent a gravity device before doing manned exploration of any planet....even Mars. Bones slowly dissolve in the absence of gravity. A cosmonaut went deaf after being in space for 1 1/2 years because the bones in his ears dissolved.

 

[Tarheel]

I assume light moves at the speed of light.

And now, gravity moves at the speed of light, right?

So they are equal, or pretty close to being equal.

Now someone explain to me how black holes work again?

 

[AustinTX]

LOL; now some people are going to think that when they drop something it falls at somewhere around the speed of light.

 

[WarriorPL]

Very interesting. I still think gravity is faster though.

 

[Imnotdutch]

Very interesting. I still think gravity is faster though.

Why?

 

[Imnotdutch]

So far, there are four basic forces in the universe:
gravitation, electromagnetism, the weak and the strong Kernkraft ( don´t know the English term).
Scientists have found out that the electromagnetic force is transferred by photons, the weak by some particles they called Z-particles and the strong by some other particle which name i forgot.

Everyone of these particles that transfer the force have been shown in experiments , except the graviton.
Most scientists believe therefore that some graviton exists that transfers gravitation, but they have not been able to find it yet.

Ok thats what I needed to hear........that makes sense now.

 

[Imnotdutch]

You have to remember that gravity is a FORCE FIELD similar to a Magnetic Field (B) or an Electric Field (E). A force field is composed a particles that move around in a path defined by the physics of the situation and have a velocity. (the term 'speed' does not take into account direction as those who took physics should have learned) I think this is the speed they are talking about. They postulate that these particles are gravitrons. I'm not up on current physics so I don't recall if they've been found to exist or not.
I think Einstein postulated that these gravity lines have 4 dimensions in his General Theory of Relativity.

Now onto the topic of conholing...

Again thats the sort of info I needed........thanks. Does that mean that gravity or magnetic fields could not exist in a true vacuum?

 

[bullett]

Can u explain some more?

I had read about 6 months ago that a group in a Calif lab (UCLA??) had built a charged chamber (ions I think) about 5 feet long into which they fired an argon laser. The laser light was expelled at the other end, and the time measured for the travel of the light was faster than 186,000m/sec. It was repeatable, and verifiable. I am obviously fuzzy on the details, but I will try to find the article..

 

[Big Johnson]

Hmmm...

 

[Norman Bates]

Again thats the sort of info I needed........thanks. Does that mean that gravity or magnetic fields could not exist in a true vacuum?

Absolute vacuum does not exist. Normally, to create matter one does need energy, but for a very short time that rule can be broken and virtual matter is created that ceases to exist very shortly after. That was already verified in experimants.

Also, if you had a source of gravitation and next by a perfect vacuum , the source of gravitation would send gravitons, if they exist, into the vacuum and the perfect vacuum would be no more.

 

[Imnotdutch]

Absolute vacuum does not exist. Normally, to create matter one does need energy, but for a very short time that rule can be broken and virtual matter is created that ceases to exist very shortly after. That was already verified in experimants.

Also, if you had a source of gravitation and next by a perfect vacuum , the source of gravitation would send gravitons, if they exist, into the vacuum and the perfect vacuum would be no more.

Ah ok.........that makes more sense now. Thanks....I appreciate the explanation.

 

[Tarheel]

Can anyone explain blackholes, please

I was under the impression that they were stars with so much gravity thier light couldn't escape. But if light travels at the same speed as gravity, then the gravity could never overcome the light, and we would be able to see the star, right?

 

[john937]

You're on the right track.
The part you're missing is that we can't see black holes directly.
No light escapes them.
What we do see is the stars just outside the gravity event horizon that have not yet been swallowed by the black hole.
A star just far enough away from the center of the black hole will be able to have it's light escape the gravity of the hole.

 

[bullett]

A black hole is a star that has collapsed on itself, creating a very, very dense object that has unbelievable mass, in a very small package. The subsequent gravity from the very large mass, concentrated in such a small space creates a very strong local force, so strong that light cannot escape, and it even bends space at that point. All these are layman's definitions, and if you are really interested, you should seek higher knowledge via the Nasa site, or others pertaining to space.

Also, I think there are some guys who have a very good knowledge of Very Dense, large mass and so forth on the Anabolic board...

 

[Code]

Absolute vacuum does not exist. Normally, to create matter one does need energy, but for a very short time that rule can be broken and virtual matter is created that ceases to exist very shortly after. That was already verified in experimants.

Also, if you had a source of gravitation and next by a perfect vacuum , the source of gravitation would send gravitons, if they exist, into the vacuum and the perfect vacuum would be no more.

Matter can neither be created nor destroyed.

 

[nivek]

acceleration due to gravity is -9.8m/s² on earth
speed of light is around 3 x 10^8m/s

this according to my physics book

 

[Norman Bates]

Matter can neither be created nor destroyed.

Energy cannot be created or destroyed. Matter can be changed into energy, that´s what happening with nuclear power.
The law of the conversation of energy can be violated for a short period of time.

some cut and paste:

Do they violate energy conservation?
We are really using the quantum-mechanical approximation method known as perturbation theory. In perturbation theory, systems can go through intermediate "virtual states" that normally have energies different from that of the initial and final states. This is because of another uncertainty principle, which relates time and energy.

In the pictured example, we consider an intermediate state with a virtual photon in it. It isn't classically possible for a charged particle to just emit a photon and remain unchanged (except for recoil) itself. The state with the photon in it has too much energy, assuming conservation of momentum. However, since the intermediate state lasts only a short time, the state's energy becomes uncertain, and it can actually have the same energy as the initial and final states. This allows the system to pass through this state with some probability without violating energy conservation.

Some descriptions of this phenomenon instead say that the energy of the system becomes uncertain for a short period of time, that energy is somehow "borrowed" for a brief interval. This is just another way of talking about the same mathematics. However, it obscures the fact that all this talk of virtual states is just an approximation to quantum mechanics, in which energy is conserved at all times. The way I've described it also corresponds to the usual way of talking about Feynman diagrams, in which energy is conserved, but virtual particles can carry amounts of energy not normally allowed by the laws of motion.

 

[Code]

Energy cannot be created or destroyed. Matter can be changed into energy, that´s what happening with nuclear power.
The law of the conversation of energy can be violated for a short period of time.

I always confuse the two.

 

[Norman Bates]

I stopped reading books on physics when i learned that it isn´t helpful to pick up chicks but sometimes it is still useful to show off

 

[fistfullofsteel]

Dr. Stephen Hawkins says he has more theories than Madonna has nudes of herself taken.

 

[WarriorPL]

I see gravity as being instant, if not close to. I can tell you exactly why, but i'm too tired to type it all.

 

[Drunken_Weasel]

good read, thanks for the info!

 

[Imnotdutch]

I see gravity as being instant, if not close to. I can tell you exactly why, but i'm too tired to type it all.

I'll remind you tomorrow........

 

[Robert Jan]

Wow I did not know this i find it very interesting.

"Matter can neither be created nor destroyed."

it can. in fact, a black hole is not really all that mass tucked into little space, its no space at all. its a point.

just like any moment is not a span of time but a point in time, a black hole is not a span of space but a point in space. it has no size.

 

[Fonz]

Newtonian, Nuclear and quantum physics are generally not interchangable.

Code is very much right.

For celestial mechanics, Newtons Laws do not work.

They just work close to the surface of the earth..

The ACTUAL gravimetric equation is:

F = - G ((m1)(m2) / r^2)

Where G is the Universal Gravitational Constant.

The G simply mans that all objects in the universe attract each other with the same force.

Gravity have speed?

Thats a very interesting concept. They are currently trying to prove the existance of gravity WAVES .

Similar to what happens with light. Light can travel in waves.
(It can also travel in particles btw. Hence why light has a dual nature)

Hasn't been proven wether or not Gravity exists in waves though.

Fonz

 

[Fonz]

A black hole is a star that has collapsed on itself, creating a very, very dense object that has unbelievable mass, in a very small package. The subsequent gravity from the very large mass, concentrated in such a small space creates a very strong local force, so strong that light cannot escape, and it even bends space at that point. All these are layman's definitions, and if you are really interested, you should seek higher knowledge via the Nasa site, or others pertaining to space.

Also, I think there are some guys who have a very good knowledge of Very Dense, large mass and so forth on the Anabolic board...

A star is essentially an uncontrolled Nuclear Fusion reaction.
(Obviously large scale)

The star also has a MASS. Gravity acts on this mass just like gravity acts on earth.

Now, stellar mechanics is a fairly simple concept.

The Nuclear reaction wants to explode and the gravimetric force wants to crush it.

Normally, Nuclear Force = Gravimetric Force so the star is what we refer to as in equilibrium.

Now, as billions of years go by, the star begins to use up all of its reactionary matter(The hydrogen), which is what permits the Fusion process.

At a certain point(And in specific cases that are too complex to explain here), the stars Fusion process will be compromised, but its mass will not decrease.(In laymans terms you can refer to this as a type of atomic poisoning).

From here, since the Nuclear Fusion Energy < Gravimetric Force,
the star collapses into iself and you get a super-nova.

From here, a black hole can be formed.

Fonz

 

[Fonz]

Wow I did not know this i find it very interesting.

"Matter can neither be created nor destroyed."

it can. in fact, a black hole is not really all that mass tucked into little space, its no space at all. its a point.

just like any moment is not a span of time but a point in time, a black hole is not a span of space but a point in space. it has no size.

Thats incorrect.

Matter is not destroyed in the Event Horizon of a black hole.

It is converted into Electro-Magnetic energy.

X-Rays to be exact.

Thats how astronomers detect the presence of a black hole.

Fonz

 

[Fonz]

Very interesting. I still think gravity is faster though.

Why......

Because gravity can bend light?

Its not that simple.

Space is curved by the various gravitaional fields of the different celestial objects. Be them planets, stars of asteroids.

If Gravity had a speed = c(Lets hypothesize)

It would be like Person A running say North, and say Person B
pushing him South at the same speed.

I'm using this an analogy of a ray of light being focused
at a planet with a gravitational field.

The ray of light doesn't just stop in its tracks.

Fonz
.