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Re: Excuse Me - Could I Interrupt

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Posted by pmb on February 28, 2000 12:14:00 UTC

re - I don't know why you guys are doing this to each other - I don't know why he is doing what he is. Can't seem t say anything without getting flamed.

For me - Every time I go to a forum and either disagree with someone or I correct something they said I get flamed. Especially if I dig too deep into the body. In this case I figured I simply ignore zc and not read anything which he posted. Then he started to spam all of my posts.

re - ..you both know orders of magnitude more than anyone else at this forum, and I'm sure no one has slightest idea what you guys are talking about most of the time. - That's why I try to phrase things to be as intuitive as possible. Sometimes the person asking the question isn't quite sure what the question should be since he may nmot be familiar with the physics [after all that's why he's asking right? :-) ]. In the case of the electron question below I assumed that he wanted to know why the electrons simply don't attract each other and collapse. i.e. How can atoms exit at all? So I posted a sumplemental answer follwing zc - flames insued.

: In any case I can't figure out how gravity could be velocity dependent. - Think of it like this. The mass (i.e. mass-energy aka relativistic mass etc) of the body increases as it's velocity increases. Mass is a source of gravity. Then the gravity increases. But momentum and stress (i.e. pressure) are also sources of gravity too. So it's a tad complicated.

re - Velocity with respect to what frame? - Ah! Good question. If you are in frame O and I am in frame O' then we will detect different values of gravitational accelertion. Take the case of directed flow of radiation, light a laser beam. The beam of light generates a gravtational field. In your frame O a test particle (non-zero but small rest mass) in free-fall will accelerate towards the beem. If the frame O' is moving in the direction of the radiation then I will observe the radiation to have a lower frequency and thus lower energy. The gravitational acceleration of a test body will be less than that measured in O. Had O' been moging, relative to you, in the opposite direction of the radiation flow then the opposite would be true. In this case there is not frame in which the source is at rest so one must be carefull.

On the other hand we could have long thin rod. Let's say it lies on the x-axis. We will call the frame in which the rod is at rest O. If we then move along the rod in either the +x or -x direction then the gravitational acceleration will increase.

re - Does this mean that if I am standing on a massive body that I will weigh more when the body has a velocity with respect to the Lab frame, and that the scale will have different readings for different observers depending on their respective relative velocities? - Absolutely. A moving body weighs more than the same body at rest. But s you can see it can get tricky i.e. moving with respect to what?

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