Why is light slower than gravity?

You Wrote: "Why does the total eclipse of the sun by the moon occur approximately 38 seconds before the maximum gravitational pull?"

Please provide a link or a reference where you have seen this information.

You Wrote: "Does this not imply that gravity is faster than light? Any other explanations for this?"

No, if anything it would imply that light travels faster than gravity. Think about it, you're saying you're seeing the eclipse (light) before gravity is maximized (gravity). That means the light got to you first. It doesn't matter anyway because light and gravity travel at the same speed. If you can provide a reference or link describing the 38 second difference, we'd have a better chance of explaining.

Think carefully about what is happening during a solar eclipse.The light is coming from where the sun WAS, the gravity is coming from where the sun IS.(the earth and moon are orbiting the sun)

If Jupiter, for instance, was orbiting where the sun appeared to be(assuming gravity equal to the speed of light) instead of where the sun is, the orbit would gradually increase distance every orbit, as would all the planets.So would all the stars in the galaxies.Assume instantaneous gravity, and the error disappears.

You Wrote: "Think carefully about what is happening during a solar eclipse.The light is coming from where the sun WAS, the gravity is coming from where the sun IS.(the earth and moon are orbiting the sun)"

First of all, the Moon and Earth are moving, not so much the Sun. Regardless, gravity doesn't act instantaneously as you're suggesting as that would violate general relativity. Gravity travels at the speed of light.

You Wrote: "If Jupiter, for instance, was orbiting where the sun appeared to be(assuming gravity equal to the speed of light) instead of where the sun is, the orbit would gradually increase distance every orbit, as would all the planets.So would all the stars in the galaxies.Assume instantaneous gravity, and the error disappears."

This doesn't make any sense at all.

The Earth accelerates toward a point 20 arc seconds in front of the visible Sun, (Where the Sun will appear to be in 8.3 minutes.) In other words, the acceleration Now is toward the True, Instantaneous direction of the Sun Now, and is Not parallel to the direction of the arriving solar photons Now. This indicates that gravity and light do not have the same propagation speed.

All orbit calculations are based on instantaneous gravity. If a delay is introduced(C), conservation of angular momentum is destroyed.

An example:

If Neptune is attracting the Sun towards it's present position, and the Sun is attacting Neptune towards it's present position,the two forces act in sync.

However, if Neptune is attracting the Sun to it's previous position, and the Sun is attracting Neptune to it's previous position,(when gravity started out across space), the result will be an increase in angular momentum of the system, which does not agree with observations.

Please explain this disparity if gravity propagates at the same speed as light.

Perhaps I am stumbling on something very simple.I am anxiously awaiting enlightenment.

You Wrote: "The Earth accelerates toward a point 20 arc seconds in front of the visible Sun, (Where the Sun will appear to be in 8.3 minutes.) "

Alright, lets discuss the basics. The Sun appears to rotate around the Earth, but this is an ILLUSION. In fact, the Sun barely moves at all as compared to the orbit of the Earth. It just sort of sits there in the center of the solar system. The Earth rotates on its axis, creating the motion for the Sun in our sky. If the Earth were to rotate faster, the Sun would move faster through the sky, if the Earth were to rotate slower the Sun would move more slowly though the sky. When you say "20 arc seconds", you are measuring the Earths rotation which has nothing to do with gravity. It's the revolution of the Earth about the Sun that has to do with gravity. Somehow, and I have no idea how, you aren't getting this important but straight forward concept and it is the source of your confusion.

You Wrote: "Perhaps I am stumbling on something very simple.I am anxiously awaiting enlightenment."

Here is a link regarding the speed of gravity. It contradicts what your trying to say, so I'm sure you'll ignore it:

http://math.ucr.edu/home/baez/physics/Relativity/GR/grav_speed.html

Thanks for the link.It makes a lot of sense.I do not ignore contradictory information, I embrace it.To do otherwise would indicate a closed mind.I am always open to other observations and theories of our universe.This has given me much food for thought, and I will be consuming it with whetted appetite.Again, my thanks, Mr Pink.

...light is coming from where the sun WAS, the gravity is coming from where the sun IS...

Isn't this using the assumption as a conclusion?

Check out Development Ephemerides of the JPL for more info on this disparity.

How are you so sure and assuming with so much accuracy that the gravitational pull or the g-beems of the earth's or the sun's are faster then the light???

Roger

The link you posted referred to two classes of observation, newtonian and relativistic. They appear to be different because one is a direct observation and the other is computationally derived. I believe our esteemed guest is embracing the Newtonian view without regard for the differences in propogation between the photons of light energy and the distortion of space/time that is gravity. Light propagates linearly while gravity propogates as a circular field distortion. When these differences are accounted for with friend Einstiens equations the speeds are very similar. IMHO

Let's eliminate the eclipse complication and ask: "If the sun were to suddenly disappear without a trace, would we see it disappear (about 8 minutes later) and cease orbiting what was it simultaneously?" Gravitational waves are fundamentally different (quadrapole moments as the most fundamental form of "radiation." Energy and momentum conservation makes formation of a dipolar gravitational radiator unlikely) and propagate very differently than does light, but would we experience the effects of each at the same time? Maxwell's equations describe the propagation of light. What fixes the speed of gravitational waves and how close is this figure to c? (And worse, why and what evidence supports it?)

-e

Hi europium, you wrote: "If the sun were to suddenly disappear without a trace, would we see it disappear (about 8 minutes later) and cease orbiting what was it simultaneously"

The effect of 'disappearance' of the Sun would ripple out as both a drop in e.m. radiation and a drop in gravitational field strength at the same rate (c). So we will loose our sunlight and our orbit simultaneously, or at least as close as can be. Studies of binary pulsars have shown the reality of gravitational radiation and placed a limit on its propagation speed of c±0.1%. The 'best buy' is that it is exactly c, as Einstein predicted.

When nothing disturbs a system, the gravitational field is "static", or better stated, the gravitational field changes with the free falling system. There are no gravitational waves in such a 'static' system. It is only when something happens to change the spacetime geodesics (free fall paths) of stars and planets that ripples appear in the gravitational field. Those ripples propagate at the speed of light.

This (somewhat) explains why the gravitational force vector always points to the 'real' position of the gravitating mass and not to its observed position. It's the 'static' nature of gravity that distinguishes it from light.

Regards, Jorrie

Yes. In the scenario I describe, the waves show up when the Sun suddenly and hypothetically vanishes. They'd better! The rate at which binary pulsars dissipate energy not only brackets the velocity of the gravitational "radiation," but also characterizes the radiation as having a quadrapolar moment. A dipolar radiator loses energy faster than what is observed to be the case in these celestial ballets, and this, too, confirms other aspects of Einstein's work.

-e

Hi europium, just so frustrating that some 3 years of science runs at the various LIGO sites have not shown one gravitational wave!

I suppose it's just unlucky that no suitable event happened close-by. So now more money is needed for more sensitivity to enlarge the volume of space covered and making a detection more probable in the next three years, I suppose...

Jorrie

At least we have Gravity Probe B's successes showing us that frame-dragging - a kissin' cousin of gravity waves - indeed exists. And can you just imagine the magnitude of frame dragging going on in and around these binaries as they spiral in? But, you know, I've seen little in the way of references to accelerational frame dragging. Have you? It's unbearably complicated and researchers tend to sidestep it for that reason, but accelerational frame dragging may explain something of the dearth of gravity waves if the rotational energy of these pairs is being dissipated more by stretching and wrapping spacetime than in wiggling it, for lack of better terms. I'm speculating here, of course, but waves aren't the only way to dissipate energy.

-e

You know, Jorrie, what's so interesting about c is that the propogation speed of both light and gravity waves (to within experimental error) is the same - c; yet the two, gravity and light, are fundamentally different beasts altogether. As if there is a deeper reality that underlies both with each having this fundamental connection in common. What is that connection, I wonder? And why is c what it is for both and not something else, different for each? Enquiring minds want to know...

-e

Do you mean why does light arrive first, making it faster? Gravity takes its time and likes to throw its weight around? Light's just too impatient.

when it comes to speed, light will rank higher than gravity, and till know we havent figured out any gravity wave, but we cant just deny its existence.

There are few rules of thumb I know, which can help you to solve any such problem;

1> Light is influenced by gravity. Just influenced(bent etc)

2> Gravity is dependent on mass, light is not.

So gravity can become more powerful than light, as in cases of black holes etc.

Light has to physically travel-may be fast-but takes a definite time delay.

Gravity is always there -an invisible force-does not have to travel. Hence no travelling delay

Hi MUKULMAHANT, you wrote: "Gravity is always there -an invisible force-does not have to travel. Hence no travelling delay"

You are correct for a static field, as I defined in my first post above, but not for a changing gravitational field.

It's a bit like when you push against a wall with a pole - the force is sort-of always there. However, change the pushing force at your end and the change will propagate to the wall at the speed of sound in the pole. So then there is a travelling delay.

Regards, Jorrie

Jorrie,

Is there a 38 second delay between the total eclipse of the sun by the moon and the maximum pull of gravity?

David

Hi David, it depends on what you mean by the "maximum pull of gravity", in precise terms.

Thinking about 500 seconds for the light of the Sun to reach us and only 1.25 seconds for light from the Moon, I cannot see any relation to 38 seconds!

Regards, Jorrie

Jorrie,

At http://home.netcom.com/~sbyers11/grav11d.htm

"...This is a review,... and quote,... and graph of the Saxl and Allen gravity research work demonstrating and measuring the earth's surface gravity perturbations that occur during a solar eclipse. This section is to present the view that the gravity perturbations are caused by planetary gravitational shielding as described with this radiation and shadowing model of gravity. The radiation and shadowing model clearly predicts an increase in gravity within the umbra and penumbra of the eclipse shadow...."

I would ask the original submitter to give the reference for the 38 second delay. The study appears to contradict ALL currently accepted theories about gravity. However, I may not have read closely enough.

Any theory should be able to predict measurable results.

David

Hi David, you gave the link http://home.netcom.com/~sbyers11/grav11d.htm, which I perceive as a 'cranky' site, one of the many anti-relativity sites out there. Maybe entertaining to read, but IMO, technically a waste of time...

During a perfect alignment of the Sun, Moon and Earth, the Moon and Sun's tidal gravity effect is largest where they are directly overhead - this causes the Earth's 1g at the surface to be slightly diminished there - stock-standard Newton!

The resulting 'bulge' in the crust does have a time lag and that also influences the time profile of the gravity there. I do not think the writer(s) of the referenced site understand the tidal effects all that well...

Regards, Jorrie

Jorrie,
please can you explain what is the gravitational pulse and how it can be measured ?

Speaking of a lower scale than colapsing stars, does it ever happen that the gravitational field is not a steady state ?
can you mention examples ?

Thanks Giuseppe

Hi giuseppe, you asked: "please can you explain what is the gravitational pulse and how it can be measured ?"

I do not know what "gravitational pulse" means, but a gravitational waves is a theoretical construct from Einstein's theory of relativity that lots of people are trying to measure directly. If you Google or Wikipedia the term, you will find an enormous amount of data on it.

I have devoted a chapter of my eBook Relativity 4 Engineers to the topic and it is available as free download from the website Relativity 4 Engineers.

Regards, Jorrie

"I have devoted a chapter of my eBook Relativity 4 Engineers to the topic and it is available as free download from the website Relativity 4 Engineers."

-----

A cursory read doesn't reveal any discussion of frame-dragging. Do you discuss it in your book?

I will read your book cover-to-cover shortly. Today has been hectic with me doing my tax return so that I can include my tax info on my daughter's tuition funding applications. Forms. The Pox on forms. And bureaucracy.

-e

^That's one thing harder to understand then relativity.

Hi Europium, you wrote: "A cursory read doesn't reveal any discussion of frame-dragging. Do you discuss it in your book?"

I did originally have frame dragging in a section on Kerr (spinning) black holes, but I 'chickened out' of it because I felt uncomfortable with my understanding of the math. In such a case I could not translate it into 'engineering spin', so I dropped it.

I am planning to publish something on my site and also in the CR4 Blog - I'm afraid, no date yet!

Regards. Jorrie

Looking forward to it, as always.

-e

to Jorrie...

Me Too!! I will add it as an appendum to your book!

to Europium

I have been trying to train our teenager to use the garbage can (aka dust bin)... but the dog also loves to dig through it for treasure... so we move it out of the dog's reach when we are gone... so later, when we come back, the garbage can is not there, so she (the teenager) uses the floor. Who do I get rid of?? the teenager? the dog? or the floor?...

Bill

From past experience a dog is infinitely easier to train than a teenager and not having a floor make walking somewhat difficult so the teenager is definitely the one to get rid of.

Hang in there though teenagers eventually grow up and with any luck will leave home so there is a light at the end of the tunnel.

Hi Bill, you said: "Me Too!! I will add it as an appendum to your book!"

Thanks for the confidence!

I'm posting a short article on rotating black holes on my CR4 Blog this week, but the "proper" treatment is still some distance off!

Regards, Jorrie

Relativity 4 Engineers

I missed all these in every college/University!

You are a good teacher

Thanks

Hi MUKULMAHANT, you said: "I missed all these in every college/University!"

So did I and it took me a long time to come even close to understanding it...

Thanks for the compliment!

Regards, Jorrie

Is it possible that this referred to a specific eclipse? If so, it would be because the paths of the Earth around the sun and the moon around the earth are not circular.

Fyz