Gravity = magic... well so does...

First of all, we don't need to prove gravity. We don't believe in it. We believe in gravitation. It sounds like semantics, but they are two entirely different theories, and saying they're the same is like saying evolution and creationism are the same. Gravity, like creationism is powered by magic and started by God (as Newton believed) while gravitation and evolution are brilliant theories by brilliant scientists that are still misinterpreted and ignored by silly people. Secondly, we can prove the earth is accelerating. Jump off a chair, and the Earth will accelerate up to meet you, then you will feel a force as your velocity changes to match that of the Earth at the particular moment. You will always still feel a force, because the Earth is always accelerating. If you fall far enough, the Earth will merely splatter you across its surface like a fly on a particularly large windscreen.

Quote from: markjo on August 18, 2008, 08:01:34 PM

Actually, PI is the ratio of a circle's circumference and its diameter.

No it isn't.

First of all, we don't need to prove gravity. We don't believe in it. We believe in gravitation. It sounds like semantics, but they are two entirely different theories, and saying they're the same is like saying evolution and creationism are the same. Gravity, like creationism is powered by magic and started by God (as Newton believed) while gravitation and evolution are brilliant theories by brilliant scientists that are still misinterpreted and ignored by silly people. Secondly, we can prove the earth is accelerating. Jump off a chair, and the Earth will accelerate up to meet you, then you will feel a force as your velocity changes to match that of the Earth at the particular moment. You will always still feel a force, because the Earth is always accelerating. If you fall far enough, the Earth will merely splatter you across its surface like a fly on a particularly large windscreen.

Explain it. I have a 5 page thread in FEQ&C, still without one.

Quote from: General Douchebag on August 19, 2008, 01:10:49 AM

First of all, we don't need to prove gravity. We don't believe in it. We believe in gravitation. It sounds like semantics, but they are two entirely different theories, and saying they're the same is like saying evolution and creationism are the same. Gravity, like creationism is powered by magic and started by God (as Newton believed) while gravitation and evolution are brilliant theories by brilliant scientists that are still misinterpreted and ignored by silly people. Secondly, we can prove the earth is accelerating. Jump off a chair, and the Earth will accelerate up to meet you, then you will feel a force as your velocity changes to match that of the Earth at the particular moment. You will always still feel a force, because the Earth is always accelerating. If you fall far enough, the Earth will merely splatter you across its surface like a fly on a particularly large windscreen.

Sure... whats pushing earth up? Magic? sure sounds like it to me... iw ill change my avatar from rockets to magic.

Quote from: spacemanjones on August 19, 2008, 05:16:15 AM

Quote from: General Douchebag on August 19, 2008, 01:10:49 AM

First of all, we don't need to prove gravity. We don't believe in it. We believe in gravitation. It sounds like semantics, but they are two entirely different theories, and saying they're the same is like saying evolution and creationism are the same. Gravity, like creationism is powered by magic and started by God (as Newton believed) while gravitation and evolution are brilliant theories by brilliant scientists that are still misinterpreted and ignored by silly people. Secondly, we can prove the earth is accelerating. Jump off a chair, and the Earth will accelerate up to meet you, then you will feel a force as your velocity changes to match that of the Earth at the particular moment. You will always still feel a force, because the Earth is always accelerating. If you fall far enough, the Earth will merely splatter you across its surface like a fly on a particularly large windscreen.

Sure... whats pushing earth up? Magic? sure sounds like it to me... iw ill change my avatar from rockets to magic.

What has been pulling you down towards the earth for all 12 years of your life with an endless supply of energy? Im gonna guess magic

Secondly, we can prove the earth is accelerating. Jump off a chair, and the Earth will accelerate up to meet you, then you will feel a force as your velocity changes to match that of the Earth at the particular moment. You will always still feel a force, because the Earth is always accelerating. If you fall far enough, the Earth will merely splatter you across its surface like a fly on a particularly large windscreen.

The potential energy does indeed come from the field, and this energy can be considered as part of the rest mass of the system as a whole.

When the object falls into the black hole, the potential energy that existed within the field is converted into kinetic energy. This kinetic energy is associated with the moving mass, but still contributes to the rest mass of the system as a whole. Thus the rest mass of the system remains unchanged during the process. (To some extent I am oversimplifying because there is no meaningful distinction between kinetic and potential energy on a global scale within the framework of general relativity. But the basic idea is correct.)


When an object falls into a black hole you are also correct to say that it will be accelerated up to the same speed that light would be traveling by the time it reaches the event horizon.


To understand why a non-infinite amount of energy suffices to accelerate the object up to the speed of light, it helps to consider a few strange things about black holes.

One important thing is gravitational time dilation. Time ticks more slowly the closer you get to the event horizon, and would tick infinitely slowly for a clock held in position at the event horizon (relative to a clock infinitely far from the event horizon.) This means that in a certain sense (as measured by a clock at infinity) even light itself never reaches the event horizon, and actually comes to a stop as it arrives there. Of course from a local perspective the light is still going the normal speed. It is just from the global perspective that it comes to a stop. Thus, from the global perspective the falling object is not really accelerated up to the speed of light because light itself is falling more slowly by the time it reaches the horizon.

Another useful way to look at is is from the perspective of conversion of mass into energy. If you were to gradually lower the object instead of letting it fall, you would extract energy from the object in the form of work that could be done by the rope. Thus, by the time the object actually reached the event horizon, all of the mass-energy of the object (E=mc^2) would have been extracted in the form of work, and the object itself would cease to exist just as it crossed the event horizon. All of the mass of the object would have been converted into energy, and the mass of the black hole itself would be unchanged as the "ghost" of the object (completely depleted of mass-energy) crossed the horizon.

If instead of extracting this energy you allow the object to fall, you are basically allowing it to keep its energy. The energy that you allow the object to keep during its fall is simply E=mc^2 where m is the rest mass of the object. Thus, it does not take an infinite amount of energy to accelerate the falling object up to the speed of light, but instead takes the entire rest-mass energy equivalent of the object.

Thus, you could say that the object has in a certain sense been converted into pure energy by the time it crosses the horizon and has no rest mass of its own, although it does contribute to the rest mass of the system as a whole.

On a related note, when atoms emit light, they do so because electrons shift from one energy level to another. This energy can be considered as a certain well-defined fraction of the mass of the atom as a whole. When light from atoms on the surface of a massive star is observed, it is seen that the light is red shifted because of gravity. This means that less energy is emitted by the atoms from the perspective of the outside observer far from the star. But since this energy is a constant fraction of the mass of the atoms, it means that the atoms themselves making up the star have less mass (as determined by an outside observer) because they are deep within a gravitational potential well.

By the time an atom reaches the event horizon of a black hole, the only mass it possesses (from the perspective of an outside observer) is mass due to motion. Thus, if it were brought to a stop at the event horizon it would have no mass of its own from the perspective of the outside observer.

Hope these ideas make sense!!

First of all, that can also be said about three other forces; Electromagnetism, Strong force, and Weak force. In example, where does the atom get the energy to keep the electron in an orbit around the nucleus? The answer is simply that all of these forces are static. There is no energy transferred from "the force", to the object. (unless it completely leaves the field of, i.e. the earth, like some satellites.

Lets look at an example:

You have a ball, 5 meters in the air. Then it has a certain amount of potential energy, which can be calculated by the formula: E=mgh. when you drop it, it immediately starts to accelerate towards the earth, and this means its kinetic energy increases. While its kinetic energy increases, the potential energy also drops at an equal rate. Immediately before it hits the ground, the energy gained (which you think is from the earth) because of the accelerating, is also lost, because of the drop in height. This means the energy gained, or lost, is always zero. Simplified, this means that loss in height is always the same as gain in speed

I would also like to add that Einstein's theory of relativity predicts some energy to be lost due to gravity waves. This has also been measured indirectly in a double black hole system, which were spinning around each other., but this is so little, it's not worth mentioning in the case of the earth, because the effect is so small.

I am going to be honest, and I admit that I am moving into uncharted waters, so I am rather going to pass on an answer I found on www.advancedphysics.com, which is the same question, but for a black hole instead of the earth, but it is still the same principle.

Quote

The potential energy does indeed come from the field, and this energy can be considered as part of the rest mass of the system as a whole.

When the object falls into the black hole, the potential energy that existed within the field is converted into kinetic energy. This kinetic energy is associated with the moving mass, but still contributes to the rest mass of the system as a whole. Thus the rest mass of the system remains unchanged during the process. (To some extent I am oversimplifying because there is no meaningful distinction between kinetic and potential energy on a global scale within the framework of general relativity. But the basic idea is correct.)


When an object falls into a black hole you are also correct to say that it will be accelerated up to the same speed that light would be traveling by the time it reaches the event horizon.


To understand why a non-infinite amount of energy suffices to accelerate the object up to the speed of light, it helps to consider a few strange things about black holes.

One important thing is gravitational time dilation. Time ticks more slowly the closer you get to the event horizon, and would tick infinitely slowly for a clock held in position at the event horizon (relative to a clock infinitely far from the event horizon.) This means that in a certain sense (as measured by a clock at infinity) even light itself never reaches the event horizon, and actually comes to a stop as it arrives there. Of course from a local perspective the light is still going the normal speed. It is just from the global perspective that it comes to a stop. Thus, from the global perspective the falling object is not really accelerated up to the speed of light because light itself is falling more slowly by the time it reaches the horizon.

Another useful way to look at is is from the perspective of conversion of mass into energy. If you were to gradually lower the object instead of letting it fall, you would extract energy from the object in the form of work that could be done by the rope. Thus, by the time the object actually reached the event horizon, all of the mass-energy of the object (E=mc^2) would have been extracted in the form of work, and the object itself would cease to exist just as it crossed the event horizon. All of the mass of the object would have been converted into energy, and the mass of the black hole itself would be unchanged as the "ghost" of the object (completely depleted of mass-energy) crossed the horizon.

If instead of extracting this energy you allow the object to fall, you are basically allowing it to keep its energy. The energy that you allow the object to keep during its fall is simply E=mc^2 where m is the rest mass of the object. Thus, it does not take an infinite amount of energy to accelerate the falling object up to the speed of light, but instead takes the entire rest-mass energy equivalent of the object.

Thus, you could say that the object has in a certain sense been converted into pure energy by the time it crosses the horizon and has no rest mass of its own, although it does contribute to the rest mass of the system as a whole.

On a related note, when atoms emit light, they do so because electrons shift from one energy level to another. This energy can be considered as a certain well-defined fraction of the mass of the atom as a whole. When light from atoms on the surface of a massive star is observed, it is seen that the light is red shifted because of gravity. This means that less energy is emitted by the atoms from the perspective of the outside observer far from the star. But since this energy is a constant fraction of the mass of the atoms, it means that the atoms themselves making up the star have less mass (as determined by an outside observer) because they are deep within a gravitational potential well.

By the time an atom reaches the event horizon of a black hole, the only mass it possesses (from the perspective of an outside observer) is mass due to motion. Thus, if it were brought to a stop at the event horizon it would have no mass of its own from the perspective of the outside observer.

Hope these ideas make sense!!

.

Nope, he's an avid RE debater. It makes me feel good to be FE.