No thing goes faster than light

Physics WEB ^ | Physics in Action: September 2000 | Aephraim M Steinberg

[mlo]

"Nothing can travel faster than the speed of sound."

"A nuclear explosion inside our atmosphere will undoubtedly cause an uncontrollable chain reaction that will ignite the atmoshpere and incinerate the Earth."

...Physical Law's were made to be broken.

But those weren't physical laws. Those were someone's shortsighted technological estimation. Physical laws are a whole different kettle of fish.

[spunkets]

The integrals always account for some physical interaction proposed in the theory. If numerical methods are used, they are simply finding a numerical solution to the integrals.

[oldvike]

Ahhhh.... brain hurting..... must try to understand this..... LOL

So basically, to get from one side of the univers to the other using a worm hole, the universe would have to be spherical? You would have to be able to bend two points in space to the point that they are right next to each other?

[UberVernunft]

An experimental measurement of the speed of gravity:

"While current observations do not yet provide a direct model-independent measurement of the speed of gravity, a test within the framework of general relativity can be made by observing the binary pulsar PSR 1913+16. The orbit of this binary system is gradually decaying, and this behavior is attributed to the loss of energy due to escaping gravitational radiation. But in any field theory, radiation is intimately related to the finite velocity of field propagation, and the orbital changes due to gravitational radiation can equivalently be viewed as damping caused by the finite propagation speed. (In the discussion above, this damping represents a failure of the "retardation" and "noncentral, velocity-dependent" effects to completely cancel.)"

"The rate of this damping can be computed, and one finds that it depends sensitively on the speed of gravity. The fact that gravitational damping is measured at all is a strong indication that the propagation speed of gravity is not infinite. If the calculational framework of general relativity is accepted, the damping can be used to calculate the speed, and the actual measurement confirms that the speed of gravity is equal to the speed of light to within 1%. (Measurements of at least one other binary pulsar system, PSR B1534+12, confirm this result, although so far with less precision.)"

Does Gravity Travel at the Speed of Light?

[Mr. K]

There is a theory which states that if ever anyone discovers exactly what the Universe is for and why it is here, it will instantly disappear and be replaced by something even more bizarre and inexplicable.

There is another theory which states that this has already happened.

[UberVernunft]

If numerical methods are used, they are simply finding a numerical solution to the integrals.

But the integrals are derived from a theoretical set of equations. You could develop a strictly numerical approach based on the original equations -- thus integrals would never be utilized. The integrals are typically derived from a perturbation expansion of the original *physical* equations.

[Aurelius]

BUMP

[UberVernunft]

So basically, to get from one side of the univers to the other using a worm hole, the universe would have to be spherical?

The general "shape" of the universe doesn't really matter.

You would have to be able to bend two points in space to the point that they are right next to each other?

Not quite. Think of a wormhole as two portals connecting different parts of the universe. You go in one portal and you end up somewhere else in the universe.

[medlarebil]

Oh yeah? What about whiskey through a Kennedy?

Ah, jealousy again rears its ugly head. How transparent you are.

[epluribus_2]

Yes, you see a red or blue shift, but the light still appears to be going at 3X108 m/s, no matter how fast you are going. Since light always appears to go at this speed, traveling at high velocity causes distances and time to distort.

unless what is happening is the "appearance" of distances and time distort, not the reality. Light will always "look" like it's going 3*10^8 but may actually change speed in a reality we cannot measure. (by observation that requires light)

[Redcloak]

The heart of Einstein's theory is that light is always observed moving at 3x10⁸ m/s no matter the observer's location. Our perception of time and distance changes to compensate for this. Thus c apears constant whether you're moving or stationary.

[spunkets]

The theoretical equations themselves are differential equations. Their sol'n involves solving an integral by whatever method.

Feynman diagrams are used in QED, quantum electrodynamics, they represent all possible interactions that may occur. A path integral is used to find the minimum energy for each interaction. The sum of these interaction energies is the total E. Without writing down the possible interactions of any particular situation the original theoretical eq. is useless, because the solution involves finding the energy that is a sum of all possible interactions. Without knowing the terms in the sum the actual sum can never be totaled. Each term in the sum involves finding the minimum energy for the particular interaction, that's where the path integral, or it's equivalent enters as a necessity.

[Bloody Sam Roberts]

Gee whiz prof, I just don't happen to have all my reference books with me at work. I guess since you don't remember ever hearing it, it must not have ever been said. Sorry. My error. Just give me an "F" for today's class.

[UberVernunft]

The theoretical equations themselves are differential equations. Their sol'n involves solving an integral by whatever method.

Sorry but this is incorrect. Pick up a book on numerical methods and you'll find many ways of numerically solving differential equations that do not involve integrals or integrating.

[UberVernunft]

Feynman diagrams are used in QED, quantum electrodynamics, they represent all possible interactions that may occur. A path integral is used to find the minimum energy for each interaction. The sum of these interaction energies is the total E. Without writing down the possible interactions of any particular situation the original theoretical eq. is useless, because the solution involves finding the energy that is a sum of all possible interactions. Without knowing the terms in the sum the actual sum can never be totaled. Each term in the sum involves finding the minimum energy for the particular interaction, that's where the path integral, or it's equivalent enters as a necessity.

All you've done is described in a round about way the perurbation expansion typically used in solving the QED equations. It is simply a mathematical method of solving the original equations.

[Future Snake Eater]

Time is a conceptual error caused by our finite minds trying to understand the unknowable.

Yeah, I've heard that before. Time doesn't exist, it is merely a human invention used to identify and separate one moment of action from the next. Kinda bizarre thinking, but not without logic.

[UberVernunft]

The theoretical equations themselves are differential equations. Their sol'n involves solving an integral by whatever method.

I should also point out that even if a numerical approach to the QED equations were to yield a set of integrals, these would tyically *NOT* be the same set of integrals that correspond to Feynman diagrams.

[js1138]

I don't think any scientist ever said that nothing can go faster than sound. There is no reason to believe that because we have always overcome "barriers" in the past, we will therefore break the light barrier.

Things easily observable by men in ancient times have traveled faster than sound. No one has ever observed anything traveling faster than light -- at least nothing that meets the most minimal standard for being called a "thing".