What is the Velocity?

There is no set velocity for either magnetism or gravity. Both of these are forces, and as such will cause an object to accelerate. Gravity will cause an object to accelerate vertically down at 9.8m/s^2. Similarly with magnetism you may calculate the force and use it to determine the acceleration acting on an object. Using the kinematic equations you can determine velocity at after a given period of time or distance using the known acceleration.

There is a velocity to how fast force fields propigate outwards, as the field strength can vary. Gravity for instance is not 9.81 m/s² consistently everywhere, that is just an approximate value on the surface of the earth, which still varies all over the surface of the earth (standing next to the Sierras, or even an iron ore deposit would give a different g than say on a deep alluvial fan somewhere in Louisiana or at sea). As I understand it the wave front for changing magnetic, electric and gravitational fields in a vaccum moves near the speed of light. the media through which these are transmitted effects the rate at which they travel, just like light speed is affected by the media.

Speed is a scalar quantity which refers to "how fast an object is moving".

Velocity is a vector quantity which refers to "the rate at which an object changes position".

Do you have any clue what you are asking or is this an attempt, as I have observed in other threads, to be incorrigibly clever?

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.

Neither magnetism nor gravity posesses velocity. These are forces which may impart velocity into bodies being acted upon by their attractive force.

Do some research on them.

So you have a particle or wave that does not move according to your good self.

Very interesting view....not heard it before.

To save me visiting a well known Internet "knowledge" site...please tell me how gravity and Magnetism are transmitted and if they are not a particle or wave could you tell me what they are in particle terms...spin / colour / etc which allows them not to move....i.e. remain static

In reply to : Do some research on them.

I think for myself , thanks and I think Gravity and Magnetism have a velocity and I think it might be faster than light....that is why I post the connectivity thread.

I await your reply.

Thanks.

I am ecstatic for you. It's obvious that you think for yourself. Have a great life.

I agree totally LYN,great to see a feller thinking for himself, then it BEGS the question, what the hell is he doing on this forum? Annoying other posters for one!

Posted and deleted....nevermind.

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If these are forces, then obviously they possess velocity by the well know relation F= ma = m x v/t. This implies that force be it magnetic or gravtational is a menfestation of velocity.

BB Raina

Ergo, forces must also posses mass!

er... what's wrong with this picture?

Yes, of course. When a body of some mass enters these forces it moves with a certain velocity which will be determined by the strength of these forces. In case of gravitational force a body moves with a constant velocity of about 10 m/sec/sec.

I thought that m/s² was an acceleration, which entails nonconstant velocity. A falling object moves faster and faster. Please clarify.

I have the velocity of light as 299,792,458 meters per second but what is the velocity of?

This is your question exactly as you wrote it. You are the one fixated on the question, so I am bringing to light the evidence that you are asking nonsense.

i belive according to general relativity the propagation of gravitational waves are limited by the speed of light. for instance, if the moon were to be obliterated in one fell swoop, the earth would not instantaneously feel the effects, but rather feel them in a couple seconds when the resulting gravity wave, (traveling not faster than the speed of light) to get to earth.

The question was or is still :

I have the velocity of light as 299,792,458 meters per second but what is the velocity of?

1 : Magnetism.

2 : Gravity.

The

1 : Magnetism.

2 : Gravity. bit was the answers or opinions I wanted

So answer the question please.

If there is anything you don't understand about the question I will happily answer.

I kind of thought I (and others have). So I am at a loss to help.

Maybe you can try popping into a local university and buying one of the physics professors a good ale and pick their brain.

If there is anything you don't understand about the question I will happily answer.

It is not about the question any more, it is about you trying to lay an egg which has not been fertilized. To early Mate, way to early!

Magnetic waves and gravity waves both move at a speed equal to the speed of light in a vacuum.

Thank you for a wonderful explanation and something for me to look at.

Yes looking at gravity in a lab would be very awkward.

Very interesting about the new observation experiments planned but how will the accuracy be from all what you mention.

These supernova maybe moving relative to so much and around so much "locally" (only a few million light years.) and we will be observing from much further than this and the information will take so long to get to us observing ; that by the time we have the information a new unknown will have taken place and change the results when known.....or is the velocity of gravity as I suspect close to but not actually infinite.

Do you know what technology they are going to use to carry out this experiment ?

In reply to "the motion of a massive object creates a distortion in the curvature of spacetime"...do not all objects do this no matter how big or small ?...or is it really down to size , and how big do the objects have to be to generate this effect ?

In reply to : even though electromagnetic interactions certainly move at the speed of light...I was under the impression that electromagnetic interactions were slower than light , but that is only what I hear not what I know.

Are gravitational patterns like those of magnetism i.e. the old iron fileing on paper with a bar magnet ?

Sorry to simplify things but ; is this what you say ?

Something that is moving around an object and "spinning" itself ( and maintaining an expected orbit.) only allows for gravity to be at the same velocity as light according to general relativity....and that can only be measured with the retardation or time delay of the distance moved by the respective body's and that we do not yet have the technology or the mathematics to measure the events that you mention and therefore will not yet know the speed of gravity but it is probably around the speed of light anyway.

Thanks for a really intelligent and knowledgeable answer and sorry for any of my other questions if they seem dumb.

Regards.

Philip.

The instrumentality most likely to succeed in detecting a passing gravity wave is the ultra-long baseline laser interferometer.

You see, based upon the mathematics of General Relativity, it is believed that a passing gravity wave will cause a slight expansion/contraction of the local space, much like a passing wave on the surface of a pond. Unfortunately, at laboratory scale, this would require measured accuracy to the quantum level, which most believe to be impossible and which is certainly beyond our technical capability at this time. To measure a passing gravity wave thus requires making accurate measurements at very long distances.

While an under-grad at Penn State Erie, I proposed just such an instrumentality. I wanted to construct and launch a dozen full-spectrum observatory platforms and launch them out to the very edge of the solar system, and then link them all together and to Earth with lasers. This would have given us a laser interferometer with a baseline of light-hours, which should have given us the requisite sensitivity to detect a gravity wave. It would have also given us a full-spectrum space-based observatory with an effective aperture the size of our entire solar system.

NASA is now going forward with a somewhat less ambitious design called LILO, using three satellites at L2 with a baseline of one million kilometers. This may have some success, but I have my doubts, as the baseline is rather short and L2 is deep withing both the Earth and Solar gravity wells. A longer baseline in "flat" space would seem more likely to succeed. Unfortunately, my proposal was a bit too ambitious (and expensive) to be taken seriously from an under-grad. *Sigh*

No disrespect to the poster, it may even be their original work, but since when did unaccredited quotation merit a GA?

http://www.xs4all.nl/~johanw/PhysFAQ/Relativity/GR/grav_speed.html

Particles are waves and vice versa as far as I know.

In reply to : Gravity is less understood.

It seems to be as surely the whole universe is bound together by gravity but how does the one edge of the universe transmit it's gravity to the other side at such a speed as slow as light ?

Is it like an ever expanding spring ? and will it decrease in its efficiency over time as the universe expands ( I am not sure it is expanding , I was just told this and was not there when the universe started to measure it's size in relation to now.)

Will light slow down as a result of the expansion of the universe as with gravity or will both remain constant ?...whatever the velocity of each is to start with.

Gravity is related to distance but light is apparently constant and massless.

So if light is massless gravity must be also ; possibly it has a negative mass just to travel faster than light and traverse the universe without hindrance.

Dear Dr ,

In reply to : When you speak of magnetism, you are speaking of a field effect, one which does not in fact propagate through space-time.

Is not a field effect such as magnetism part of particle physics and therefore transmitted or propagated.

I mean if a object were on its own in its own universe it would have nothing to gravitate towards , and now another object suddenly enters this universe would not the 2 objects instantly "see" through gravitational forces each other and now we energy entering the equation in the form of attraction , so now we the famous possibly E = mc²

And this is my point as there must be a mass part and therefore a particle or wave transmitting this energy and I ask the question how fast does it travel and the same for magnetism.

In reply to : Some have speculated that they may even propagate at many times the speed of light or even instantaneously. Of course instantaneous propagation would make detection even more difficult that it already is.

I am thinking it is faster than light maybe near instantaneous if not instantaneous actually along with magnetism.

Thanks for your interest and I would be interested in your reply.

Magnetic fields, like light and radio waves are electromagnetic waves. Both propagate at the speed of light and are massless.

The problem is one where you are confusing a force, such as a magnet exerts on a block of steel and the propagation of a magnetic wave.

Here is an experiment. Place a strong magnet in space. Now instantly place a steel sphere nearby. The steel sphere instantly feels the effect of the magnetic field it has been immersed into. There is no delay. It's like jumping into a pool of water. You get wet right away, but when you dog jumps in at the other end you don't feel the resulting wave from the dog entering the pool until it has propagated to you location.

Now, imagine the same experiment with two permanent magnets and the second the magnet was an electromagnet that can be controlled by a voltage.

If you unplug one of your stereo speakers and plugged the output of your amp to that imaginary electromagnet (with a really long cable), then put on Led Zeppelin, crank the volume all the way, what would happen?

Well, if you did this in a public place and charged admission you would have to pay royalties to the band... But... The permanent magnet would experience a force that would vibrate the permanent magnet back and forth, toward and away from the electromagnet, but the permanent magnet would move with a slight delay compared to the excitation signal applied at the electromagnet. This delay is the propagation speed of the electromagnetic field through space.

Dear contributors

When I posted my first reply I used my signature line as an answer. It has been ignored, so I think now is a good time to go a bit further on about this. I am not a specialist in this field but no one else here seems to be either, so i might as well.

There is a second kind of gravity.

This accepts that gravity (the first kind) does exist. It is a force that increases the larger the mass or density of an object is and gives the object the ability to attract other objects. Just like a balanced formula or thought can. If it has substance that is.

Depending on the size, distance the attracted object is from the attracting gravity field (not magnetic), the smaller object will always travel towards the larger object. The amount of gravity that the smaller object has on the larger mass is a negligible amount but would still have to be considered in any formula. To formulate this is impossible.

This is proof that thoughts of substance give an idea attraction.

This is (abstract) proof that thoughts of substance give an idea, theory, formula, statement attraction, as one says "One is attracted to an idea". Although a thought or the processes that leads to it or that comes from it, are not of a physical (measurable) nature, they could be still seen and evaluated as something real. They seem to portrait the same properties as "real" gravity.

It is the gravity of logic thought.

If thought had no substance, mass, logic it could not be reacted to or reflected upon, although this happens all the time. From Portugal in this given case. In other words, the question has no gravity and that I feel attracted to this subject is more due to the thoughts of others on this.

The OP's question, is hypothetical and more of a provocation than any thing else. It can not be answered and if not, can't satisfy a trained critical mind. Never mind the extent of an experimental set up. It is about as hard as it is for me to prove what I am stating above. The satisfaction I get from my approach, concept is instantaneous though.

So that it becomes visible, measurable, tangible and weigh-able to the world.

I ran out of space in my signature line and choosing a short version has compromised what I really meant to say. Maybe this longer version helps to convey what I was trying to get at.

It is a joy to use ones brains for such an experiment but to end up with a bullet proof conclusion, formula (in both cases) is really infantile and beats the aim of trying to find that "God Particle" and then be able to play around with it, at will. As if there would not be more important things to do with ones time.

Operating the scales is a demanding exercise though.

Very demanding indeed, but still quiet enjoyable, I find. By the time we have worked out a formula for the question at hand, we might as well live and deal with the realities of logical thought and its influence on this world. One thought at a time. You know, it is swampy ground and wriggling can cause one to be sucked in.

I hope this warrants an attractive reply, Ky.

Obviously we don't know yet. Kudos to Klearzen for his extensive knowledge on the subject. It's a stimulating exercise to think about though and this is why I looked. Maybe when or if you meet your "higher power" he'll tell you! I doubt it'd be a comprehensible number though. (like the US debt)

I wonder if Tesla knew? Seems he had a tiny bit of insight on the subject.

I did not look anywhere for this answer thanks it was just a thought.

I do not believe everything I read on the internet.

I await any replies from yourself to my post's on this subject.

I was hoping to find someone with some knowledge but if you just copy and paste then you might as well send me a link to a catalogue for electronic components ( Radio Spares is a favorite choice but do feel free to send a link to Farnell if you are daring enough.)

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"I do not believe everything I read on the internet."

And yet you seek answers on an internet forum.

You're right I was off topic but I forgot to hit the button. That's what the rating is for so just give me an off topic rating.

And no I don't feel like giving you an answer because (after reading other posts) you only insult those that don't agree with you. This tells me that you aren't even listening to those that have different opinions (or maybe even knowledge of the questions you asked). I was merely pointing out the fact that you don't trust others but you seek their answers anyway (sounds a little like trolling).

I do admire the fact that you come up with these questions and theories on your own but if you don't know how to communicate with people they're worthless.

Oops I forgot to hit the button again...

Dont worry Cingold, I hit the button for you, The GA one.

Damn, i see i got modded, oh well i suppose it serves me right for falling for Portis' nonsense.

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Enough said already, just now i get "modded"

These 3 are independent and different phenomena. Gravity is rate of change of velocity (acceleration). Your question is like 1 meter = how many gramme or 1 hour = how many kilometers!!!!

I am sorry but gravity is not the rate of change of velocity.

It is a force which causes what you say.

"Gravity is rate of change of velocity (acceleration)."

I don't believe you can quantify gravity that way. The definition of gravity is one of four of the fundamental forces of the universe (gravity, electromagnetism, Strong Force, and Weak Force). The Strong and Weak forces are nuclear forces or interactions.

The attribute of gravity is that objects of mass attract each other. This is different than an object of mass that simply accelerates.

You can also show that your definition is wrong when you consider that you are sitting on a chair in front of your monitor reading this post. Your butt (excuse my candor) is pressing down on the chair by the force of gravity. It is not accelerating downward.

Another example is two objects of mass that attract each other in free-space. When they finally contact (assume an inelastic collision) they come to rest together. The net velocity between them is zero, yet they are still bound together by the gravitational force.

I disagree,

F = ma

If you have a force (whatever is holding your butt to the chair, ie gravity) and mass (some have more than they would like), you have acceleration. You do not need velocity to have acceleration.

and...

a = Δv/Δt = (vfinal - vinitial) / (tfinal - tinitial)

a = acceleration

Δv = change of velocity

Δt = change in time

For an object at rest, v = 0 (both initial and final). Run the numbers, a = 0.

Conversely, F = ma, or F = m * (Δv/Δt). When Δv = 0, F = 0.

Lastly, force of gravity, F = G (m1*m2 / r^2)

Where G = Gravitational constant.

Notice that acceleration is not part of the formula.

So, how can you have acceleration without velocity? Show me the math?

Try using this equation to argue your point:

F = GMm/R²

• F is the force of attraction between two objects in newtons (N)
• G is the universal gravitational constant in N-m²/kg²
• M and m are the masses of the two objects in kilograms (kg)
• R is the distance in meters (m) between the objects, as measured from their centers of mass

Exactly! You beat me to my own edit, thanks! ;-)

dt = 0 therefore dv/dt = undefined (lim t-> 0 = infinity)

What if you are sitting for 5 minutes (300 seconds)? Δv/Δt = 0 not undefined.

Run the math again, Δv/Δt ==> 0/300 = 0.

Your proof doesn't hold up in this case.

Simple, Δt ≠ dt

Is your position that F = ma is not correct, or that when you are sitting in a chair that no force is acting on you? One or the other would have to be true given your argument.

Your simple answer does not make sense.

Δt = delta t or t(initial) - t(final).

If you are not convinced, look up the equation for and the definition of acceleration for yourself. I think you will have to agree that a = [v(initial) - v(final)] / [t(initial) - t(final)].

In other words, acceleration is the change of velocity per change in time.

I am not saying the F=ma is not a valid formula, it is just it is not the right formula for your argument. Now, you could use it if you fell out of your chair. ;-)

However, for sitting static in a chair it should be: F = GMm/R^2

That is the correct formula for the force imparted by your butt and the chair.

Δv/Δt gives you the average acceleration from t₀ to t₁

it does not (necessarily) give you the acceleration at t₁

Acceleration due to gravity is constant, so instantaneous and average acceleration are the same quantity.

So, that still hasn't proved your argument.

I guess someone owes me some money for a faulty education and text books. My understanding is F=ma is a fundamental law of physics which always applies to any mechanical analysis, static or dynamic (no need to drag quantum effects into this which builds on but does not contradict relativistic physics). F=mg is an extrapolation of the general law F=ma.

We can take gravity out of this completely by looking at a ball attached to a rope and spun in a circle at a constant velocity. At any time after t₀ there will be a ∆t but ∆v = dv = 0 and a = v²/r (the ever popular centripetal acceleration)

I think the difficulty come in from accelerations popular (common) usage versus its scientific meaning.

Anyway... it's good to have a spirited discussion on CR4 without it getting personal.

Cheers, Jim

Jim,

Sure, this is about physics and not personalities. ;-)

There all kinds of equations for all kinds of things, but that doesn't mean that every situation uses the same equation.

Okay. F=ma may give you the force of a human in a chair on Earth, but it is not quite right for the application of my original thread. Why, because it doesn't take into account the system, only the acceleration produced by one mass on another.

If you have two equal masses stuck together by mutual gravitation the equation surely fails. Let's do an example. Imagine two Earths clinging to each other. What is the net force between them. Your method:

F=ma = 6.0 × 10^24 kg * 9.8 m/s^2 = 5.9 x 10^25 Newtons

The method I proposed with:

G = 6.67300 × 10^-11 (Gravitational constant)

r = 12750 meters (Distance between center of two masses or Earths)

F=GMm/r^2 = (6.67300 × 10^-11 * 6.0 × 10^24 kg * 6.0 × 10^24 kg) / (12750^2) = 1.48 x 10^31 Newtons

I am hoping I did my math correctly. The formulas are right. You will see two different results. Not even close.

F=ma works when the one body's mass is insignificant compared to another's mass, but not even close when the two masses are of similar scale. It doesn't apply in every case.

In reply to

Acceleration due to gravity is constant, so instantaneous and average acceleration are the same quantity.

Does this not apply only on Planet Earth surely gravity can be different strengths on different planets stars black holes etc ?

So the g is the same on the surface of the earth as it is on say on the surface of the moon? I am not even sure that it is the same across the surface of the earth over relatively short distances (is the gravitational constant over the Pacific Ocean the same as over the Andes?). So if you are moving above the surface and the gravitational strength happens to be different at different locations would F=ma vary?

You are right, but the original point of the discussion was about the idea that F=ma (specifically acceleration) describes gravity, which I countered that it is an inaccurate description and the formula in not the correct formula.

While you are right that gravity varies throughout the Earth's geoid, the error really doesn't support nor negate the original claims.

However, if you want to get technical, for short delta t (times, i.e., seconds) acceleration can be assumed to be constant for the free-fall equation of acceleration near or on Earth.

Would you agree?

I guess that would depend on the precision of the acceleration we wanted. If Dt were substantially smaller than the precision of Da, then yes, but if not then no. Of course in real-world applications, such very high precision would be overwhlemed by other more ambiguous terms like air resistance.

Well said.

I agree with you.

it was a bad formula for the discussion.

I thought the definition of velocity is a change in direction or speed.

See Post #2. A simple definition.

I found it for myself but refuse to wriggle just for your entertainment

no, a change in direction requires an acceleration

Everything I ever learned tells me that gravity and magnetism are forces. Unless there is some parallel universe out there, forces impart velocity or acceleration, they have none of their own. I would have to agree with the other posters. You are one of the most arrogant people I've ever seen on this forum.

Me thinks the question should be "What would the speed be of the theoretical graviton?"

And magnetism is propagated at C.

I thought that scientists had found that the Higg's Boson transmits gravity.

would not the graviton be part of this particle ?

No, both are still hypothetical entities and the Higg's Boson is believed to be a fairly massive particle. The graviton no one seems to know what to do with it because it doesn't fit the Standard Model and has issues in other theoretical models such as String, etc.

The problem with the "graviton" is that in order to work requires faster-than-light transmission.

Eh? Why?

Because the effects of gravity occur instantaneously (or near so) across space. The model with a graviton requires a particle exchange.

It depends on which model you use to do your calculations. If you use Newtonian physics, gravity must act instantaneously.

If you use Special Relativity to perform the calculations you use C as the propagation speed.

Not sure what you mean by particle exchange. Gravity is a force, like magnetism.

Within the standard model the 4 fundamental interactions (forces) all have a particle interaction.... well, except for gravity which is still not understood. In the Weak interaction it is between leptons, in the Strong between hadrons, in Electromagnetic interactions it is electrons and photons and with gravity it is...... and yes, it is assumed that if there is a graviton its velocity =c.

That is a good explanation of the four interactions.

So, are we on a different discussion now or are you trying to reinforce your point that gravity has a speed greater than light? I am a little confused.

I don't think we are on a different discussion. You questioned the idea of particle exchange within the 4 forces and I answered. As for faster-than-light graviton, I recall that one of its fundamental flaws within the standard model is a break with relativity to get it to "work". I'm not advocating the existence of a graviton, faster than c or otherwise. I don't think it exists, or a Higgs-Boson. And I think the standard model is going to fall on its face when we finally understand the nuances of gravity.

Cheers.