Astronomy

The limits of the visible Universe

Advance the scale factor and compare the Hubble sphere, particle horizon and event horizon. They answer three different questions about light.

Actual application image

The model and its limits

Flat matter–radiation–Λ model, with Ωr=0.00009. Horizons are proper distances at the selected epoch; the display compresses distance for readability.

Equations used in the module

Equations
D_p=a(c/H₀)∫₀ᵃ da/(a²E); D_e=a(c/H₀)∫ₐ^∞ da/(a²E); R_H=c/H

Astronomy

Send identical light pulses from a compact star. Increase compactness and compare the emitter’s clock with a distant observer’s clock.

Astronomy

Approach the final contact of two compact stars. Compare gravitational-wave frequency and inspiral time as their masses change.

Astronomy

Scrub through 25,772 years. Follow the axis around the ecliptic pole and see why the pole star changes.