gokul.er137

talking about pushing universes reminds me of Alcubierre drive. Kaku was probably describing the curvature of space time due to the presence of mass. In that sense, space does push' objects closer to the field. The curvature of space is the gravitational redshift of light. The curvature of time is the time dilation in gravitational fields. Both are explained by suitable demonstrations by extending the principle of equivalence. But again I am not sure why he described it that way. What I have given above is just my interpretation.

vp -> phase velocity vg -> group velocity generally vp ->c^2(speed of light squared)/vg Doing that and substituting does not give me a satisfactory answer. On a more conceptual note -> group velocity is the rate of change of angular velocity('delta'omega) with the change in wave number('delta'k). Phase velocity is omega/k , that is at any particular instant. So to get the group velocity I could also differentiate omega with respect to k, but I do not know anything about them either.

i was intrigued by how to solve this. the phase velocity of ocean waves is sqrt(g*lambda/2*pi) where g - acceleration due to gravity, lambda is the wavelength of the wave. The question is find the group velocity. I tried many things but was not able to get to a proper answer. Any help?

WMAP states that the shape of the Universe within two percent accuracy is flat. I have this particular question in relation with what we are discussing. - Why can't we assume that the early Universe expanded equally in all directions with a velocity of 'c' (max) for about a second or so? Then within a second, wouldn't we get the volume to be 4/3*pi*c^3?

@ physman - there is hardly any difference between what you are trying to prove and what the MM experiment tried to prove. The only difference is that you have replaced ether with wind. Anyways, it does not hold for light. The speed of light is a constant in physics. Just like the e/m ratio, G constant or Planck's constant. If you measured the ratio of the charge of electron to its mass in Andromeda, it would not change. Same for light.

Thanks for that ajb, D H. btw Griffin seems to be one helluva guy. D H - Thanks for that info. I am as of now involved in certain physics projects based on spacetime concepts with a PhD professor. Is publishing papers a good indication to top Univ's about my inclination towards physics?

Well, I am going to become a mechanical engineer but I am strongly inclined towards Astrophysics. As you say, I don't know everything. I know a decent level of relativity, quantum mechanics and pure sciences. I am constantly in the learning process and will be publishing a few papers in the near future. Plus, I am involved in a project based on Space time models. Is this an indication to the Universities that I could be a prospective student?

I do not refer to dual programs in which we end up with an engineering degree followed by a post graduate degree. Can we do them separately, like B.E. Mechanical Engineering followed by MS in Physics ? Do Universities like MIT, Caltech accept people with a degree in engineering into their Postgraduate Pure Science programs?

that idea for the most part of it got done with after maxwell. But they have not gone far enough to actually treat it like a medium or field or something like that.

possible. getting a time field into the concept would ease the calculations as far as I know provided it does not get into the way of GR

@swansont - Yes I meant the frequency. The clock will show an entirely different interpretation as it is based on the history of the frame.

I understand what you say. You mean that the clocks on the whole will show a difference when checked after the experiment. But for that particular instance when the velocity is the same, there will be absolutely no difference in the time dilation. Thanks.

I understood the length contraction idea. Thanks. But what about the time dilation again? I don't understand how the acceleration really affects the dilation at a particular time. Dilated time between 2 instances in the event = Actual time between 2 instances in the event*gamma factor. Gamma factor makes use of the velocity. Where does the acceleration come into picture?

the big crunch requires a blackhole of infinite density to take in all the matter. But then if what Hawking told is true, then not all matter that gets into a black hole comes out of it. then again it is speculation. the physics that holds true within the Universe need not hold for things outside the Universe. So, as of now, we don't have any chance of knowing.

@swansont - if we assume the masses are the same, the frequency is the same, will there be a time dilation with respect to each other? what details do you mean? I never mentioned that the length becomes 0. almost 0 is what i said. Let us say, the size of an electron. That would hardly hinder the object travelling at such a large speed. So what say?