Physics Tools
Eight calculators that put real astrophysics at your fingertips — black hole event horizons, stellar furnaces, light-bending atmospheres, and the expansion of the universe.
Black Hole Radius
Event horizon calculator.
PhysicsEscape Velocity
Surface escape speeds.
PhysicsStar Temperature
Wien's Law calculator.
PhysicsRedshift & Hubble
Galaxy distance & z.
PhysicsLight Travel Time
Signal lag to planets.
PhysicsStellar Magnitude
Absolute vs Apparent.
PhysicsSolar Wind Time
Sun-Earth particle travel.
PhysicsStellar Luminosity
Total star power output.
Real Astrophysics, No Textbook Required
How small would the Sun have to be to become a black hole? How fast would you need to throw a baseball to escape the Moon's gravity? These calculators answer questions like that using the same equations found in introductory astrophysics courses — from the Schwarzschild radius to the Stefan-Boltzmann law.
Each tool shows its formula and constants alongside the result, turning every quick calculation into a worked example. Planning an observing session instead? Browse the observation tools or the calculation tools, or view all 20 tools.