Recent content by haruna

Well, this is a pretty straightforward question : Why do the hairs on the beard of very old men thin out and fall off leaving bald in the face, so to speak? I am asking this question with Raymond Smullyan in mind. In photographs, he certainly has much less beard now that he's 95, than 20 years ago.

I am sorry in advance, if I lack the expertise and terminology to explain rigorously what I mean, but I am trying my best. To give you an idea, consider a metric with ds=\sqrt{dx^{2}-dy^{2}}. A creature applies the Pythagoras' theorem there, with the manner I described above. If a line segment...

Hello, I am having a problem about the nature of the measurements of the intervals ds's forming out of infinitesimal displacements dx's of the coordinates and the actual meaning of the measurements of the same dx's, in flat metric spaces. I am certain that this must be a trivial problem...

In unison with Mach's principle any coordinate change of flat spacetime resulting in space-time interval other than: ds^2 = -dt^2 + dx^2 + dy^2 + dz^2 must produce tidal forces ( see Newton and rotating bucket ). Tidal forces are an immediate outcome of curved space-times, hence GR.

I remember having read in an excellent article by Demetrios Christodoulou once, that one must view the speed of light as playing the role of infinite speed, a speed that can never be reached. Indeed, if you define the speed as rapidity http://en.wikipedia.org/wiki/Rapidity, the hyperbolic...

Thanks a million! This is it!

Hello again, Two days ago, I started a thread asking about the same question more or less, and I was thinking that the matter was clear now in my mind, because I had made an error in my calculations... Before I begin, I want to admit that my English is not very good, and my exposition to...

Oops. This is not right! The correct statement is: I forgot to rotate the velocity 3 or (4-vectors in the general case) to point both in the x-direction.

Yes, thank you both. I can see my mistake now, tho not for the reason you've just pointed out. You see, when i move along one of the two masses bringing its speed to a standstill, I add the momenta vectorially by transferring the one component of momentum to the other moving mass. My...

Hello to everybody, the question seems trivial in my mind, yet, is it legal to say that there is not unique frame of 0 total momentum in the Minkowski spacetime plane? I am thinking of two non-accelerating equal masses on a horizontal plane, one is moving horizontally, the other...