Solving Violations of Causality with U > c

  • Thread starter Thread starter runevxii
  • Start date Start date
  • Tags Tags
    Causality
runevxii
Messages
7
Reaction score
1
I'm having trouble working this problem. I don't know where to begin.
Here's the problem:

Let P and Q be any events, P causing Q via propagation of some signal. Let the speed of the signal, call it U, be greater than the speed of light c. In S, the time seperationg is given by delta_t and the spatial separation is given by delta_x, with both events occurring on the x-axis.

In an intertial frame that has velocity v(less than c) along the x-axis and observe these same two events. Show that if v is chosen such that c^2/U < v < c, then in this fram causality is violated, that is the order of the events is reversed, Q occurring before P.
 
Physics news on Phys.org
Nevermind I got it, but thanks if you were trying!
 
Hello everyone, I’m considering a point charge q that oscillates harmonically about the origin along the z-axis, e.g. $$z_{q}(t)= A\sin(wt)$$ In a strongly simplified / quasi-instantaneous approximation I ignore retardation and take the electric field at the position ##r=(x,y,z)## simply to be the “Coulomb field at the charge’s instantaneous position”: $$E(r,t)=\frac{q}{4\pi\varepsilon_{0}}\frac{r-r_{q}(t)}{||r-r_{q}(t)||^{3}}$$ with $$r_{q}(t)=(0,0,z_{q}(t))$$ (I’m aware this isn’t...
Hi, I had an exam and I completely messed up a problem. Especially one part which was necessary for the rest of the problem. Basically, I have a wormhole metric: $$(ds)^2 = -(dt)^2 + (dr)^2 + (r^2 + b^2)( (d\theta)^2 + sin^2 \theta (d\phi)^2 )$$ Where ##b=1## with an orbit only in the equatorial plane. We also know from the question that the orbit must satisfy this relationship: $$\varepsilon = \frac{1}{2} (\frac{dr}{d\tau})^2 + V_{eff}(r)$$ Ultimately, I was tasked to find the initial...
Back
Top