Re: Division by zero

Am Sonntag000002, 02.02.2025 um 03:19 schrieb Ross Finlayson:

On 02/01/2025 01:36 AM, Mikko wrote:

On 2025-02-01 08:14:08 +0000, Thomas Heger said:
 

Hi NG
 I'm actually not really certain, but found an error in Einstein's 'On
the electrodynamics of moving bodies' which is quite serious.
  See page six, roughly in the middle:
 There we find an equation, which says this:
 ∂τ/∂y= 0

 Do you mean on page 899 (9th page of the article) in §3?
The operation is not division but a partial derivative.
 

Now, 'tau' is a time belonging to the moving system k.

 Yes, but it is also a number that is computed from coordinates of K.
 

This system k moves along the x-axis of system K with velocity v,
while x- and xsi-axis coincide and etha- and y axis remain parallel.
 In other words v_y is permanently zero,

 Yes,
 

 or: ∂y=0.

 No. ∂y is not a number but a part of an operator. There are points with
different values of y and ∂/∂y refers to a line where t, x, and z (but not
y) have the same value at every point.
 See https://en.wikipedia.org/wiki/Partial_derivative