🌃 Olbers’ Paradox Calculator
Explore Olbers’ Paradox: see how night-sky brightness would grow with distance in an infinite, uniform starfield.
Why Isn’t the Night Sky Uniformly Bright?
Olbers’ Paradox asks: if the universe were infinite, static, and uniformly filled with stars, why is the night sky dark instead of blindingly bright? Each thin spherical shell of stars at distance r contributes flux proportional to (number of stars in the shell) × (brightness per star), and since a shell’s star count grows with r2 while each star’s brightness falls with 1/r2, those factors cancel — so every shell contributes equally, and the total flux from summing shells out to radius R grows as F(R) = n × L × R, without limit.
This calculator demonstrates that mathematical result directly: try increasing the radius and watch the cumulative flux grow linearly, illustrating why an infinite, unchanging, uniform starfield really would predict an infinitely bright sky.
The real universe resolves the paradox because it is not infinite in age or static: it has a finite observable horizon and is expanding, so light from the most distant, oldest stars hasn’t reached us yet (or has redshifted out of visible light) instead of piling up forever. This tool is for conceptual, educational exploration of the paradox, not a literal astronomical measurement.