4:48 AM
1

I have been thinking about this for ages and it has been driving me crazy. I was convinced that rainbows are always complete circles that appear to be arcs because they cross the horizon. Then, I saw videos like this, where the rainbow appears to reach the ground and continues to move away until ...

8 hours later…
12:33 PM
2

I understand that the Ricci tensor is derived from the Riemann tensor, but I know that the Weyl tensor is also derived from the Riemann tensor. So is it possible to calculate the Weyl tensor from the Ricci tensor or Ricci scalar and if so how?

6 hours later…
6:34 PM
1

Let's say, if i apply a specific force on an object on a theoretically frictionless surface, will it move at constant velocity forever? If i apply newton 2nd law, F = ma, there will be a certain acceleration, so will the object move at constant velocity or a increasing velocity(constant accelerat...

1 hour later…
7:51 PM
2

Wikipedia says that for a beam splitter $$\begin{bmatrix}E_{c}\\ E_{d} \end{bmatrix}=\begin{bmatrix}r_{ac} & t_{bc}\\ t_{ad} & r_{bd} \end{bmatrix}\begin{bmatrix}E_{a}\\ E_{b} \end{bmatrix}$$ the demand $\left|E_{c}\right|^{2}+\left|E_{d}\right|^{2}=\left|E_{a}\right|^{2}+\left|E_{b}\right|^{2}$ ...