Governing The Laws of Relativity?

[us.2u]

Can the speed of light & gravity have various velocitys? The reason I ask is a brighter light, faster than a dimmer one? & is a stronger force of gravity faster than a weaker force? some argue that darkness is the abscence of light, but if that is so; is light the abscence of dark? or maybe they're equal relatively speaking? your thoughts?...us.2u

[swansont]

The speed of light through different media depends on the index of refraction. This is a frequency dependence, though not an intensity dependence.

 

However: c is the speed of light in a vacuum, and this is the same for all light. There are a lot of experimental results that confirm this. The speed of gravity is also c according to general relativity, and there are some measurements that confirm this as well.

[gib65]

Can the speed of light & gravity have various velocitys?

 

Gravity doesn't have a velocity. If anything, it would have an acceleration, but even this is only in a manner of speaking. It makes more sense to ask what's the velocity of an object falling in a gravitational field after a certain amount of time after being dropped from rest. And then you'd have to specify what the force of that gravitational field is (the Earth's gravity is more powerful than the moon's).

 

some argue that darkness is the abscence of light, but if that is so; is light the abscence of dark?

 

Of course it is, but only semantically. Physically, light is a collection of photons, particles of electromagnetic energy. Darkness is only the absence of such particles, therefore darkness is not a thing that's there.

 

Can the speed of light...have various velocitys?

 

Light travelling through air or water travels slower than through a vacuum. As far as I know the speed of light is pretty much constant in a vacuum though (300,000 km/s if I'm not mistaken). However, I remember reading that some studies have shown that this speed limit was faster at the beginning of our universe. Anyone want to back me up on this?

[Tom Mattson]

Gravity doesn't have a velocity.

 

He's talking about the velocity with which gravitatioal effects propagate.

 

Case in point: The Sun is 8.3 light minutes away from Earth. If the sun were to suddenly vanish, would we fly away from our orbit instantly? 8.3 minutes later? Some other time?

 

The answer would depend on the velocity of gravity.

[us.2u]

Gravity doesn't have a velocity. If anything, it would have an acceleration, but even this is only in a manner of speaking. It makes more sense to ask what's the velocity of an object falling in a gravitational field after a certain amount of time after being dropped from rest. And then you'd have to specify what the force of that gravitational field is (the Earth's gravity is more powerful than the moon's).

 

But gravitity must have decelration as well, as to when an object hits the ground so as the object slows; gravitys properties must change so that it isn't a constant any more is that correct?...us.2u

[gib65]

He's talking about the velocity with which gravitatioal effects propagate.

 

Oh, yes, I wasn't thinking about this. My mistake.

[JLydon]

Can the speed of light & gravity have various velocitys? The reason I ask is a brighter light, faster than a dimmer one? & is a stronger force of gravity faster than a weaker force? some argue that darkness is the abscence of light, but if that is so; is light the abscence of dark? or maybe they're equal relatively speaking? your thoughts?...us.2u

 

 

I myself do not know the answer, being this is the first night I've ever been interested in physics and space in general, I shouldn't.. BTW, I'm new to the forum.. But I don't feel his questions on light or gravity, I'm not sure if it's an avoidance of the question or you're just not understanding it.. Let me rephrase if I'm understanding correctly... Does brighter light move at a faster pace than dimmer, less powerful light?? And for the gravity question.. In two different gravitational scenarios, You have object (1) , considering objects have a maximum velocity we'll say the distance between the two points (A) and (B) would end before maximum velocity is reached.. Ok, on Earth object (1) is dropped from a resting position from point (A) to (B) and the same expirement is performed on the Moon, the Moon being the only variable.. Would the stronger gravitational pull create a higher velocity in object (1) between points (A) and (B).. While typing this I've come up with a question of my own... Does the strength of gravitational pull determine an objects maximum velocity??? If I sound terribly uneducated, my schooling ended in the 9th grade. Thanks

[JLydon]

After thinking my question over, I easily answered it myself... Every object has a specific maximum velocity, UNLESS some other form of energy is put into it.. Therefore higher gravity (more power) would cause a higher maximum velocity..

[JLydon]

Gravity doesn't have a velocity. If anything' date=' it would have an acceleration, but even this is only in a manner of speaking. It makes more sense to ask what's the velocity of an object falling in a gravitational field after a certain amount of time after being dropped from rest. And then you'd have to specify what the force of that gravitational field is (the Earth's gravity is more powerful than the moon's).

 

But gravitity must have decelration as well, as to when an object hits the ground so as the object slows; gravitys properties must change so that it isn't a constant any more is that correct?...us.2u[/quote']

 

I don't believe gravity has a deceleration, the deceleration would depend on the object breaking the fall.. IE A stone falls through the tree tops, it decelerates as it hits the leaves, and then hits the ground to stop.. The gravitational pull is constant, even when the object isn't in motion..

[us.2u]

I don't believe gravity has a deceleration, the deceleration would depend on the object breaking the fall.. IE A stone falls through the tree tops, it decelerates as it hits the leaves, and then hits the ground to stop.. The gravitational pull is constant, even when the object isn't in motion..'So why is it then if we cast a stone across a river or throw one across a field it slows to a stop without obstuction? Is this friction greater than gravity? If so surely gravity cannot be constant?'....us.2u

[swansont]

I don't believe gravity has a deceleration, the deceleration would depend on the object breaking the fall.. IE A stone falls through the tree tops, it decelerates as it hits the leaves, and then hits the ground to stop.. The gravitational pull is constant, even when the object isn't in motion..'So why is it then if we cast a stone across a river or throw one across a field it slows to a stop without obstuction? Is this friction greater than gravity? If so surely gravity cannot be constant?'....us.2u

 

You have to look at all of the forces to deduce the motion; I'm not sure what you mean by 'slows to a stop without obstruction' since the behavior will depend on what direction you throw it. Gravity (acceleration) near the earth's surface is approximately constant; any fluctuations are from mass distribution variations.

[us.2u]

You have to look at all of the forces to deduce the motion; I'm not sure what you mean by 'slows to a stop without obstruction' since the behavior will depend on what direction you throw it. Gravity (acceleration) near the earth's surface is approximately constant; any fluctuations are from mass distribution variations.

 

 

I don't understand 'Directional Throw' also I see gravity moderately as a brake- not "Acceleration" unless there is a type of 'centrifugal force' initated by Earths rotation which I believe would make gravity near the Earth constant; but I feel relativity dosen't quite add up here unless of course I'm failing to see what is really happening...us.2u

[swansont]

I don't understand 'Directional Throw' also I see gravity moderately as a brake- not "Acceleration" unless there is a type of 'centrifugal force' initated by Earths rotation which I believe would make gravity near the Earth constant; but I feel relativity dosen't quite add up here unless of course I'm failing to see what is really happening...us.2u

 

Anything that happens to change velocity is, by definition, an acceleration.

 

You need to be more specific in your objections. I don't understand what you're discussing.

[us.2u]

Anything that happens to change velocity is' date=' by definition, an acceleration.

 

You need to be more specific in your objections. I don't understand what you're discussing.[/quote']

 

 

Thanks Swansont I misunderstood; but all seems clear now...us.2u

[Einstein Jr.]

The sun does have different stages it goes through because it is a star and not an actual planet. One day that star will burn out and we may be hurled into the orbit of a totally different planet possible eliminating natural light altogether.

[JLydon]

I don't believe gravity has a deceleration, the deceleration would depend on the object breaking the fall.. IE A stone falls through the tree tops, it decelerates as it hits the leaves, and then hits the ground to stop.. The gravitational pull is constant, even when the object isn't in motion..'So why is it then if we cast a stone across a river or throw one across a field it slows to a stop without obstuction? Is this friction greater than gravity? If so surely gravity cannot be constant?'....us.2u

 

 

Again, when you throw the stone across a river or across the field, the force you put into it with your own strength is stronger than the force of gravity, but since the force you put into the stone doesn't posses perpetual motion, it will slow down obviously and fall to the ground because gravity's strength has now overcome the lossed energy you put into the stone.. All the while gravity was present, it's just when you release the stone the energy is greater than gravity..

[arkain101]

Gravity is a force in which matter contains.

 

The amount of mass is what determines the force of the gravity, and the distance in which you are from the gravity source the lower the force becomes.

 

Bodies of mass have a gravitational constant. With earth, it is aproximatly 9.8m/s squared acceleration force. The moons constant is less but by no means should its gravity force be any slower than earths. The only difference is in how fast it can accelerate a body of mass. A feather and a truck will fall the same speed on the moon. But since gravity accelerates an object it should be the same speed anywhere you find it. It appears that larger bodies of mass contain more of what makes gravity to cause a more higher accelerating force.

The problem though is that the further you get away from a source the less the gravity is. So if you were to test how fast gravity could cause an object to hurl towards its source you would run into the problem that the further you take it away the slower the it will accelerate.

 

lets run an experiment on the go here.

 

You take an apple 1000miles away from the moon (and we are assuming no other forces of gravity excpet the moon are involved in the experiment)

You also take an equal apple 500miles away from the moon.

and 1 mile before the moon you have a speed trap device that measures their velocity.

I beleive in theory since the gravitational constant changes as you increase the distance between two objects that the speed of the 2 apples would be equal at the 1 mile mark.

It would be so very difficult to measure how fast gravity can make something go because you always run into the source right when you really starting to accelerate.

unless you could find use a source of almost infinate mass and gravity, then I suppose you could work it out.

[Locrian]

Bodies of mass have a gravitational constant. With earth, it is aproximatly 9.8m/s squared acceleration force.

 

9.8m/s^2 is not the gravitational constant. The gravitational constant is the same everywhere. 9.8m/s^2 is the acceleration on a body near the surface of the earth. It differs far from the surface.

 

I beleive in theory since the gravitational constant changes as you increase the distance between two objects that the speed of the 2 apples would be equal at the 1 mile mark.

 

Countless experiments on gravity have been done, and they disagree with you. Just sum up the work done by gravity over those distances and convert it from kinetic energy to velocity. You'll see that the speed would be different.

[alext87]

The gravitational constant is 6.67 x 10^-11 and is the constant which is applies across the whole universe. The gravitational constant does not change as object get further away from each other however the force of gravity does by the inverse squared law.

 

Earlier somebody stated that gravity has no velocity however, if the sun was removed suddenly the Earth would continue in the same orbit (as if still orbiting around the sun) for 8 more minutes. The Earth would go dark and at the sametime the Earth would change course!!!!

[arkain101]

Quote:

Originally Posted by arkain101

Bodies of mass have a gravitational constant. With earth, it is aproximatly 9.8m/s squared acceleration force.

 

 

9.8m/s^2 is not the gravitational constant. The gravitational constant is the same everywhere. 9.8m/s^2 is the acceleration on a body near the surface of the earth. It differs far from the surface.

 

Quote:

I beleive in theory since the gravitational constant changes as you increase the distance between two objects that the speed of the 2 apples would be equal at the 1 mile mark.

 

 

Countless experiments on gravity have been done, and they disagree with you. Just sum up the work done by gravity over those distances and convert it from kinetic energy to velocity. You'll see that the speed would be different.

 

I agree, I am incorrect. I should of used more of a questioning way of explaining what I was thinking than more of a lecture.

[us.2u]

As I presume magnetism light & gravity are c; then surely they must all be constant? I presume by that none of them can be variable, or that would contradict them being a constant would it not?...us.2u

[us.2u]

Einstein predicted the speed of gravity equals the speed of light, but it's never been proven.

 

 

Albert Einstein

 

Sunlight takes 8 1/3 minutes to travel to Earth. Scientists believe gravity has the same property.

 

"If you had some monster or deity able to pick up the sun and completely move it away from our solar system instantaneously, what would happen to the Earth?" asked Ed Fomalont, an astronomer with the Radio Astronomy Observatory, on CBC Radio's As It Happens.

 

Fomalont said the Earth would continue in its orbit around the sun for another 8 1/3 minutes until the sun and its gravity disappeared – the gravitational time lag would equal the time lag of light. Then the Earth would go in a straight line.

 

Since no one can move the sun, astronomers had to find another way to measure the speed of gravity.

 

Jupiter meet quasar

 

Fortunately, on Sept. 8, Jupiter passed close to the light coming from a quasar, a star-like object billions of light-years away. The alignment offered astronomers their chance.

 

Astrophysicists used the alignment and their modern telescopes to test Einstein's assumption that light and gravity travel at the same speed.

 

'You can't bet against Einstein. I'd bet 100 to 1 that he's right'

-Ed Fomalont

Radio and optical astronomers are able to measure the direction to celestial objects in the sky very well. They knew the quasar was going by as Jupiter happened to be almost in front.

 

Jupiter's gravity should have nudged the light coming from the quasar, causing it to appear to shift its position slightly in the sky.

[LucidDreamer]

Does brighter light move at a faster pace than dimmer, less powerful light??

No. If both the dim light and the bright light are traveling through the same medium then they will travel at the same speed. Light is made of "particles" called photons. Bright lights have more photons than dim lights, or at least more photons reach the person observing the two lights. Bright and dim are determined by intensity, which is the amount of photons.

[CanadaAotS]

Earlier somebody stated that gravity has no velocity however' date=' if the sun was removed suddenly the Earth would continue in the same orbit (as if still orbiting around the sun) for 8 more minutes. The Earth would go dark and at the sametime the Earth would change course!!!![/quote']

 

has anyone done any experiments confirming the speed of gravity?

Also, if nothing can go faster then the speed of light and say a planet was hurtling toward you, would the speed of gravity have to go through some kind of time dialation (like light) ?

[swansont]

Einstein predicted the speed of gravity equals the speed of light' date=' but it's never been proven.

[/quote']

 

You say this, but then go on to provide quotes and descriptions of an experiment that confirmed this very thing, to about 10% IIRC. There are also measurements from binary pulsar systems that arrive at the same conclusion with higher precision. So "never been proven" is a gross overstatement, unless you are just playing at semantics with the inductive nature of science.