1,171 reputation
515
bio website
location
age
visits member for 2 years, 2 months
seen yesterday

2d
comment Do clocks measure conformal time (new argument)?
I assume that the light pulse used in the clock travels through an optic fiber so I do not have to use a FRW null geodesic equation for that light pulse. Therefore I don't need to consider the co-moving length of the clock itself.
2d
comment Do clocks measure conformal time (new argument)?
i know proper length = comoving length * a(t)
2d
comment Do clocks measure conformal time (new argument)?
The co-ordinate length $\Delta x$ is an arbitrary constant co-moving co-ordinate length used in the null geodesic equation of freely propagating light that by definition has the same size as the fixed proper length $\Delta L$ of the clock. I use the equality of $\Delta x$ and $\Delta L$ to write down a relationship between an interval of proper time $\Delta t$ and an interval of time measured by the clock $\Delta \tau$. In my argument I do not need to consider the changing co-ordinate length of the fixed proper length clock itself.
2d
comment Do clocks measure conformal time (new argument)?
But in my model of a light clock the light pulse is sent down an optic fiber of fixed proper length $\Delta L$. The interval of time that it takes $\Delta \tau=\Delta L / c$ is not itself an interval of proper time $\Delta t$ because it does not propagate through space so it does not obey the null geodesic equation $c\Delta t/a(t)=\Delta x$.
2d
comment Do clocks measure conformal time (new argument)?
I understand that for a co-moving observer in a FRW Universe the proper time elapsed is the same as the cosmological time $t$. But my model of a co-moving clock, which seems perfectly reasonable, measures conformal time $\tau=\int dt/a(t)$ instead.
2d
revised Do clocks measure conformal time (new argument)?
added 87 characters in body
2d
comment Do clocks measure conformal time (new argument)?
Ok so what's wrong with my reasoning?
2d
revised Do clocks measure conformal time (new argument)?
deleted 2 characters in body
2d
revised Do clocks measure conformal time (new argument)?
deleted 78 characters in body
2d
asked Do clocks measure conformal time (new argument)?
May
21
revised Can't derive FRW Christoffel symbol
added 11 characters in body
May
21
revised Can't derive FRW Christoffel symbol
added 337 characters in body
May
21
asked Can't derive FRW Christoffel symbol
May
17
comment Momentum conservation in FRW spacetime
Does a Killing vector in the x direction imply that x-momentum is conserved for a particle travelling on a geodesic?
May
17
asked Momentum conservation in FRW spacetime
Apr
21
awarded  Popular Question
Apr
17
revised Light clocks measure conformal time - detailed argument
added 364 characters in body
Apr
16
comment Light clocks measure conformal time - detailed argument
Ok - I see what i've done wrong now!
Apr
16
accepted Light clocks measure conformal time - detailed argument
Apr
15
revised Light clocks measure conformal time - detailed argument
added 52 characters in body