Physics
- The search for a steady beat
From sundials and water clocks to quartz and caesium: how each clock counts something that repeats, and why the second is now defined by an atom.
- 9min read
- 10min listen
- 31questions
- Ibn al-Haytham
The eleventh-century scholar who showed that we see by light entering the eye, and who made experiment the test of a theory in optics.
- 8min read
- 10min listen
- 25questions
- Magnetism and electromagnetism
In 1820 a compass needle swung beside a wire carrying current, and electricity and magnetism turned out to be one force. The motor, the power station and light itself follow from it.
- 9min read
- 11min listen
- 34questions
- Electricity
Charge, current, voltage and resistance, from static on a doorknob to the circuits in a house, and why a bird can sit safely on a power line.
- 9min read
- 11min listen
- 31questions
- Light
Your eyes send nothing out. Light comes in, and an idea first tested in a dark room in Cairo still explains the mirror, the rainbow and the red of a sunset.
- 9min read
- 10min listen
- 34questions
- Heat
Why metal feels colder than wood in the same room, why a hot drink always cools, and why no engine can turn all of its fuel into motion.
- 9min read
- 10min listen
- 28questions
- Gravity
Why astronauts float although gravity is nearly as strong up there, why the Moon never falls down, and how a man in a shed weighed the Earth in 1798.
- 8min read
- 10min listen
- 28questions
- Energy
Work, joules and watts, why energy changes form but is never used up, and where a car’s energy goes when it brakes.
- 9min read
- 9min listen
- 28questions
- Forces
What a net force does to an object, why forces always come in pairs, how a rocket speeds up in empty space, and how a lever trades distance for force.
- 9min read
- 10min listen
- 33questions
- How things move
Speed, velocity and acceleration, how Galileo timed a fall, what an astronaut’s hammer and feather did on the Moon, and why steady motion cannot be felt.
- 8min read
- 11min listen
- 30questions