Physics Question

joe-90 · 10 Sep 2012

Where have I said that gravity doesn't travel at light speed?

What I've been saying is that if the sun disappears INSTANTLY - then its gravitational field would disappear INSTANTLY.

No experiment can prove that because the question doesn't make sense in our universe. Matter cannot disappear at all - but if it could it would take with it the gravity it possessed.

Why can't you get that into your head?

calorific · 10 Sep 2012

delete

joe-90 · 10 Sep 2012

jeds said:
Tonka,

Just bringing this forward in case you missed it. I think there are only really two possibilities; one being that that no force exists without a source - in which case the force disappears the moment the sun disappears. I'm ignoring that one for the time being. The second possibility is that the gravitational force leaves the source and travels at close to speed of light - in which case when you take the Sun away there would be a delayed reaction. What I can't see in my mind is that the force could exert at maximum for eight and a half minutes and then the Earth would suddenly fly off. It seems far more logical to me that there would be an immediate reduction in force which would increase as time and distance elapsed. I'd be interested to know what you think.

He didn't miss it, he just can't answer it.

I can answer it though.

You make a fundamental error in thinking that gravitons in transit affect our planet. They do not.

Water droplets from the sky (rain) can only wet you when they land. The droplets in transit have no effect on you until they arrive.

The same with gravitons.

Only gravitons that reach the earth effect us, the gravitons in transit do not. That must mean the earth is held in place by the very last of the arriving gravitons - just like you get wet up to and including the final water droplets when it rains.

It's a complete nonsense and a shambles of a theory.

matt1e · 10 Sep 2012

Hi all, first post in a while as been working away, and since gravity has always fascinated me then what better thread than this one

UriBentMySpoon said:
Whos wins? Scientists and their experiments or Joe's brain?

Joe's brain, and Scientists and their experiments as they are both correct
ie the effect if gravity is instantaneous
not sure that I'm with the "curvature of space time" believers but I'm certainly with Joe on the fact that gravity has no "delay" as light does

Matt

jeds · 10 Sep 2012

joe-90 said:
jeds said:

Tonka,

Just bringing this forward in case you missed it. I think there are only really two possibilities; one being that that no force exists without a source - in which case the force disappears the moment the sun disappears. I'm ignoring that one for the time being. The second possibility is that the gravitational force leaves the source and travels at close to speed of light - in which case when you take the Sun away there would be a delayed reaction. What I can't see in my mind is that the force could exert at maximum for eight and a half minutes and then the Earth would suddenly fly off. It seems far more logical to me that there would be an immediate reduction in force which would increase as time and distance elapsed. I'd be interested to know what you think.

Click to expand...

You make a fundamental error in thinking that gravitons in transit affect our planet. They do not.

First of all, the graviton theory isn't mine. Secondly, I don't necessarily think it to be the case. Tonka put forward the idea that a graviton exists and if it does its effects would be limited to the physical rules governing other known particles. In other words it would travel at something close to, but not more than, the speed of light. He went on to say that in the unlikely event of the Sun suddenly disappearing nothing would happen to the Earth for about eight and a half minutes. Taking that as a premise I am trying to think as to how it might work.

joe-90 · 10 Sep 2012

Yes but think about the rain analogy. Only the stuff that hits us wets us. So how does that work with gravitons? Only the gravitons that hit us effect us.

matt1e · 10 Sep 2012

jeds said:
First of all, the graviton theory isn't mine. Secondly, I don't necessarily think it to be the case. Tonka put forward the idea that a graviton exists and if it does its effects would be limited to the physical rules governing other known particles. In other words it would travel at something close to, but not more than, the speed of light. He went on to say that in the unlikely event of the Sun suddenly disappearing nothing would happen to the Earth for about eight and a half minutes. Taking that as a premise I am trying to think as to how it might work.

It wouldn't work as gravity has no delay the effect would be instantaneous

you might find This paper interesting

Matt

TheOriginalTonkaToy · 10 Sep 2012

joe-90 said:
Yes but think about the rain analogy. Only the stuff that hits us wets us. So how does that work with gravitons? Only the gravitons that hit us effect us.

Yes do think about the rain analogy. Only the stuff that hits us wets us - very true but after the condensation stops in the cloud there are still drops falling - those drops will eventually wet us too until the final drops reach us and the rain finally ceases.

Good analogy

TheOriginalTonkaToy · 10 Sep 2012

jeds said:
TheOriginalTonkaToy said:

jeds said:

Tonka, I follow your argument most of the way but I'm struggling with the following: Your explanation makes it sound like the gravitons beaming towards the Earth in space can have a holding effect on their own with no body to pull against. In other words right up to the point that the last graviton arrives at the Earth the Earth would be held by those gravitons. But how can this be? Do the two bodies held together by gravity not rely on each other for stability. More akin to a rope holding two bodies together. Cut the rope holding the Sun and earth together and the effect would be instant. One part of the rope would fly off with one of the bodies and the other with the other. The rope could not hold either in place on it's own.

Click to expand...

Think of the rope being shaken to produce a wave that travels along it, now make that rope very very long stop shaking the end suddenly. It'll take a while for the pre-existing waves already on the rope to cease and the rope to become still. That's a reasonable analogy

Click to expand...

Thanks.

Can I take this another step. The waves on the rope must have a cumulative effect. The more of them there are the more the effect. Lets say more waves = more gravitatianal force. With the sun in place the rope is full of waves = maximum gravitational force. Take the sun away and the waves don't disappear immediately but they must reduce. So there are two possibilities; one is that gravity remains at maximum whilst any number of waves remain in the rope. Those waves career towards Earth and when the last one arrives the Earth flies off into space. This doesn't seem logical to me. A more obvious answer is that the reduction in gravitational force would be very small to begin with but would steadily increase as the waves reduce. So the Earth may not immediately fly off as if there was no gravity but it would notice an instant effect that would increase until the waves were completely decayed. And of course that reduction would be non-linear because of the rapidly inceasing distance.

PS. (to others - not Tonka) If you can't give an answer to this without adding an insult I'd prefer you didn't bother.

It's an interesting idea but if we assume that the force is carried by a gauge boson (it's a reasonable assumption given that the other fundamental forces are carried by gauge bosons) then there will be inevitably be quanta involved. This suggests that you won't see a gradual attenuation but rather a drop from one level directly to another.

TheOriginalTonkaToy · 10 Sep 2012

joe-90 said:
jeds said:

Tonka,

Just bringing this forward in case you missed it. I think there are only really two possibilities; one being that that no force exists without a source - in which case the force disappears the moment the sun disappears. I'm ignoring that one for the time being. The second possibility is that the gravitational force leaves the source and travels at close to speed of light - in which case when you take the Sun away there would be a delayed reaction. What I can't see in my mind is that the force could exert at maximum for eight and a half minutes and then the Earth would suddenly fly off. It seems far more logical to me that there would be an immediate reduction in force which would increase as time and distance elapsed. I'd be interested to know what you think.

Click to expand...

He didn't miss it, he just can't answer it.

I can answer it though.

You make a fundamental error in thinking that gravitons in transit affect our planet. They do not.

Water droplets from the sky (rain) can only wet you when they land. The droplets in transit have no effect on you until they arrive.

The same with gravitons.

Only gravitons that reach the earth effect us, the gravitons in transit do not. That must mean the earth is held in place by the very last of the arriving gravitons - just like you get wet up to and including the final water droplets when it rains.

It's a complete nonsense and a shambles of a theory.

Don't make assumptions or answer on my behalf Joe. I do have a life outside of the Internet you know.

joe-90 · 10 Sep 2012

TheOriginalTonkaToy said:
Don't make assumptions or answer on my behalf Joe. I do have a life outside of the Internet you know.

Yeah sure mate. I've heard the rumour about life out there but I'm not buying it.

UriBentMySpoon · 11 Sep 2012

joe-90 said:
Where have I said that gravity doesn't travel at light speed?

What I've been saying is that if the sun disappears INSTANTLY - then its gravitational field would disappear INSTANTLY.

No experiment can prove that because the question doesn't make sense in our universe. Matter cannot disappear at all - but if it could it would take with it the gravity it possessed.

Why can't you get that into your head?

I think Joe is slowly starting to get it. You are excepting that gravity, its effect, travels at light speed? The change from mass to no mass will mean a change in gravity, that effect will take time to reach us.

At the sun then yes the gravity "stops" as soon as the Sun disappears, it takes time for that effect to take place lesewhere though.

And again, the question is about gravity changing in an instant, how long would it take to effect a body at x distance away.

The Sun disappearing is a framing device for the question so that people can understand what I am getting at. Everyone else understood that apart from you apparently.

And no I cannot find a real world recorded instance where a sun has just disappeared because that is impossible as many people have pointed out but that does not matter in terms of the question.

Does this prove me wrong? No! I have pointed out real world instances of sudden gravity change and its measured delay, I have pointed out that general relativity predicts gravity travelling at the speed of light.

You show me where it has been proved or even shown possible that gravity, or its disappearance, effects everything instantly, which is what you have stated because you have worked it out with your brain.

A sudden change in the gravity disturbance caused by the Sun will take approx 8 1/2 minutes to reach us.

noseall · 11 Sep 2012

joe-90 said:
Where have I said that gravity doesn't travel at light speed?

The original question read.....

If the Sun was to completely disappear in an instant, we would notice the light had gone out in the 8 1/2 minutes approx it takes for light to travel here, my question is, how soon after the Sun has disappeared would the lack of the Suns gravitational pull take effect?

To which Joe wrote....

Straight away.

..and also wrote.....

If you look at the hammer swinging thing in the Olympics then when the guy lets go of the handle - it happens straight away. It doesn't take any time to reach the hammer. Same with the sun and earth

I would say Joey lad that you clearly said that gravity does not travel at light speed by inferring that the change would take place straight away. I'm no Einstein but this suggests that you think the effects of gravity move faster than c.

joe-90 · 11 Sep 2012

No guys you just aren't getting it. Mass deforms space and creates a gravity zone. Take that mass away and the gravity zone has gone with it. The question makes no sense in our universe so why do you expect the answer to make any sense in our universe? Gravity and mass are inseparable. You cannot have mass without gravity, ergo, you cannot have gravity without mass. If you think you can - then give me an example (they won't).

noseall · 11 Sep 2012

joe-90 said:
Take that mass away and the gravity zone has gone with it.

And so that leads us to the OP's question the one that all of us have been banging on about.

DOES THE EFFECT OF SUDDEN GRAVITY LOSS OF ONE BODY HAVE AN INSTANT EFFECT ON DISTANT PLANETS OR DOES IT TAKE TIME?

Joe, you said the effects would be INSTANT.

No one is disputing the relationship betwixt mass and gravity are they.

Physics Question

calorific

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