# Tag Info

1 vote

### Stellar aberration without relative motion between source and observer

There are three sources of abberation: annual (due to the orbit of the Earth) diurnal (due to its rotation) and secular (due to the relative motion of the solar system. The secular aberration is ...
• 93.6k
1 vote

### Stellar aberration without relative motion between source and observer

It's impossible to measure instantaneous aberration because there is no reference angle to compare against. What can be measured is the variation of aberration over the course of a year. In 6 months, ...
• 2,643
In comoving coordinates, the distance $d_\mathrm{PH}$ to the particle horizon (PH) is equal to the conformal time $\eta$ that has passed since the Big Bang, times the speed of light $c$. That means ...