studiot

Perhaps that's the difference between proving (or disproving) something and explaining something. If you set out to prove or disprove a statement then you need to present the necessary flow of logical argument in full, without appeal to ouside authority, however august. If you set out to explain something to someone (and I have seen you do this well several times at SF) then it is legitimate to say "this is the (standard) text on the subject, read section XXX" Incidentally there are many, many texts on relativity. Macomb, Dodson & Poston, The Manchester Physics series and even Griffiths spring to mind, although none are 'popsci'.

Have you ever read any of Martin Gardner's work, or that by my other reference? https://www.google.co.uk/#q=martin+gardner

Relativity. And there is no "proof." That's pretty good evidence though. Lizzie L, on 22 Feb 2014 - 3:49 PM, said: The spatial dimensions are right circular and the temporal dimension is hyperbolic. Here is the article on it, from John Baez: http://math.ucr.edu/...symmetries.html Here is the hyperbolic trig Lorentz transform: t → (cosh s)t + (sinh s)x x → (sinh s)t + (cosh s)x y → y z → z where, s, the "rapidity", is related to the ordinary velocity v by v = tanh s Well we seem to be getting somewhere in the second part of that post, since I can now see that you are talking about conic sections and their properties, when you use the word hyperbolic, not for instance, hyperbolic differential equations or other possible meanings of the word. So please spell out exactly what you do mean when you say Time is hyperbolic, space is circular.

Well perhaps it's just me but I can't see an attachement in your post.

???

It's difficlt to know what to say in a thread that has clearly wandered off topic from a discussion of the general provenance of sources of any form to the specific bashing of a particle genre of writing. I have been following this thread but so far only objected to some of the attitude of the OP, and it seems that several others have agreed with me. I agree with Ophiolite. There are many popsci writings that are far from trash. The writings of the late Martin Garden and the not so late Ian Stewart come to mind. Further surely the response to any input should be tailored to the level of sophistication of any discussion. We do not try to explain Joule's experiment to a 16 year old via Noether's theorem for good reason. So it follows that the level of any references should be commensurate with the level of the discussion.

+1 querulous I would start my list with the The Shorter Oxford.

Why would you restrict this to solid matter? Do you mean what is usually called solid state physics or do you mean some form of continuum mechanics? Have you done any counts to see if there is enough frequency of posting to warrant separating this stuff out into its own forum?

Well, that is not the relativistic view. Relativity proves time is hyperbolic. Spacetime's basic group is the Poincare group. Time is not right circular. What proof do you have that they are incompatible for you to be able to say this?

An electric current is what happens when there is a net movement of electric charge in a particular direction. Charge is regarded as being 'carried' by various bodies, also called charge carriers. It does not exist by itself. Two types of carrier you will encounter in biology are electrons (negative carrier) which are sub atomic particles (smaller than atoms and part of them) and ions which are atoms (or molecules) with an excess of electrons (negative carrier) or a deficiency of them (positive carrier). Positive charges moving in one direction are equivalent to negative charge moving in the opposite direction. Your instructor meant the movement of electrons when referring to charge current and the movement of ions when referrring to ionic current. Ionic currents normally occur in solution, since ionisation is one way that solutes can dissolve in solvents.

You have made that mathematical statement several times, but there is the view that time is a simply useful parametrisation for many equations.

c) The position vector is the vertical value of the y coordinate of the mass. The seismometer works by having a rigid frame. That is the dimension d does not alter during the motion. So the position vector for the mass can be obtained by noting that the base of the frame is at y, the top at y+d and the mass a distance x down from the top. Can you make an equation of this ? d) The mass suffers two vibrations, the one due to the seismic excitation ( the y) and the one due to its own resonance The (x). The result depends upon the relative constants of the dashpot and the spring, which control the resonant response and how close it is to the excitation frequency. Does the force of gravity make any difference? Remember also (it was what you deduced in parts A & B) that the ground force Asin(wt) does not act directly on the mass. Are any of the forces acting on the mass actually sinusoidal? Further is Y not a force but a distance ?

If two objects are in relative motion does not the separation change, unless that relative motion is zero?

But that velocity is perpendicular to r so are they in relative motion?

Go on.

What were parts A and B? They usually hang together so one leads on to the next. What exactly do you not understand about C and D? You have noted that despite the two axes shown in the sketch this is a one dimensional problem (ie x is not horizontal)? Finally I take it that the spring and dashpot are vertically aligned through the centre of gravity of the mass, so there is no twisting of the mass.

In relation to time and the foregoing discussion about physical and real, consider the following: In space, positions x, (x+10) and (x-10) are all physical and real since I can move my boat from one to the other and back again as many times as I like and place it in any one of them if I am a good enough sailor. But in time I can only observe my boat in the present. I cannot move it to the future or the past or observe it there. So does this make the present physical and real, but the future and past non-physical and non-real?

There is the issue of the motion. Apparent mass gain appears to observers in relative motion. What is the relative motion of two observers at say r/2 and r from the centre of rotation? Does their separation alter?

Of course, John is quite right, the only entity for which A = -A is zero so you are just working on keeping zero to itself. I was thinking about the general trig sum of two angles. CAST is a way of remembering which trig function is positive in which quadrant, here is a list.

Consider alpha = 20 degrees and beta = 50 degrees. Are you really offering that cos (20+50) = - cos (70) ? Some of these statements depend upon which quadrant your sum ends up in, have you heard of CAST?

Does Hooke's law matter? By the looks of things rkt was suggesting calibration. I was going to suggest something like that myself, along with what we used to call a spud gun (that used a coil spring).

[math]I = \int {\frac{{du}}{{1 - {u^2}}}} [/math] [math] = \frac{1}{2}\ln \frac{{1 + u}}{{1 - u}}[/math] [math] = \frac{1}{2}\ln \frac{{1 + \sin x}}{{1 - \sin x}}[/math] [math] = \ln |\tan \left( {\frac{\pi }{4} + \frac{x}{2}} \right)|[/math] [math] = \ln |\sec x + \tan x|[/math]

Well done for doing it yourself. +1

Because you have made d(1/cosx) in your line 1 equal to sinx in your line 2 rather than sinx/cos2x So work your integration by parts out again.

You have the right idea with your 1/1 but with the wrong part of the integral [math]I = \int {\frac{1}{{\cos x}}dx} [/math] [math] = \int {\frac{{\cos x}}{{{{\cos }^2}x}}dx} [/math] [math] = \int {\frac{{\cos x}}{{1 - {{\sin }^2}x}}dx} [/math] If we make the substitution sinx=u [math] I = \int {\frac{{du/dx}}{{1 - {u^2}}}} dx = \int {\frac{1}{{1 - {u^2}}}} du[/math] This has three different (logarithmic and trigonometric) forms. Does this help?