Astronomy

15 ideas, each explained on one page with a 60-second lesson you can play right there.

Anthropic principle The anthropic principle explains that we observe physical constants suitable for life because observers cannot exist in a universe without them.
Copernican Principle The Copernican principle states that Earth occupies an average position in space and that humans are not privileged observers of the universe.
Doppler Effect The Doppler effect changes the observed pitch or frequency of waves when a source and observer move relative to each other.
Doppler Effect of Light The Doppler effect of light shifts the wavelength and frequency of electromagnetic waves when a light source and observer move relative to each other.
Drake Equation The Drake equation is a mathematical formula that estimates how many active, communicative alien civilizations exist in our galaxy.
Fermi Paradox The Fermi paradox exposes the clash between the high statistical odds of alien life across billions of stars and our complete lack of evidence for it.
General Relativity General relativity explains gravity as the warping of space and time by mass and energy, replacing Newton's concept of an attractive force.
Gravitational time dilation Gravitational time dilation is the actual difference in how fast time passes for objects at different distances from a heavy mass.
Great Filter The Great Filter argues that an evolutionary barrier makes advanced life rare.
Panspermia Panspermia is the scientific hypothesis that microscopic life originated elsewhere and spreads across the universe inside rocks and comets.
Rare Earth hypothesis The Rare Earth hypothesis argues that simple life may be common, but complex, multicellular life requires an extremely rare set of circumstances.
Space Exploration Space exploration is the physical investigation of outer space using uncrewed robotic probes and human spaceflight.
Special Theory of Relativity The Special Theory of Relativity is a physics theory describing the relationship between space and time for objects moving at constant speeds.
Speed of Light The speed of light is the universal speed at which electromagnetic waves and massless particles travel through a vacuum, which is empty space.
Time Dilation Time dilation is the difference in elapsed time measured by two clocks due to relative speed or gravity.