Topic
Gravity
9 articles
Astronomy
Why can’t we feel the Earth spinning?
Standing still at the equator, you are being carried eastward faster than an airliner flies. Nothing rattles, nothing leans, and a dropped ball falls straight down. For two thousand years that was the best argument against the Earth moving at all.
Physics
Why does a bicycle stay up?
Standing still it falls over the moment you let go. Rolling, it will cross a field on its own with nobody on it. Everybody has heard the explanation involving spinning wheels, and somebody built a bicycle specifically to test it.
Physics
Why does toast land butter-side down?
Everybody assumes this is a joke about bad luck, or that the butter weighs one side down. Ten thousand drops by a thousand schoolchildren say it is real, and the culprit turns out to be the height of your kitchen table.
Physics
Why doesn’t a spinning top fall over?
Set a top going and it leans at an angle that would flatten anything else on the table, then stays there, drifting round in a slow circle. Nothing is propping it up, and gravity has certainly not let go of it.
Astronomy
Why are there two high tides a day and not one?
The Moon is only ever on one side of Earth, yet the sea climbs the beach twice a day. The second high tide arrives from the direction the Moon is not.
Biology
How does a tree lift water to its highest leaf?
The tallest tree alive is taller than a thirty-story building, and the leaves at the very top stay wet all day. No pump ever built can raise water a tenth of that far.
Astronomy
Why can’t light climb back out of a black hole?
Light is the fastest thing there is, and nothing has ever overtaken it. Yet there are places it sets off from and never leaves. The explanation most people are given was worked out in 1783, and it is wrong.
Astronomy
Why do we only ever see one side of the Moon?
Every human being who has ever lived has looked up at the same face of the Moon. The other half stayed hidden until a camera flew behind it in 1959. Something lined the Moon up, and it is still working today.
Physics
Why won’t a wheel full of weights turn forever?
Hang weights around a rim so that one side is always the heavy side, and the wheel should keep falling over itself and never stop. Engineers have drawn that wheel for eight hundred years. Not one has ever run.