Kids playing tetherball using centrifugal force Who first explained centrifugal force? When something is going straight, it always keeps going straight unless something else stops it or turns it. (The [...]
Light takes years to reach us from these stars far away in space. What is a light-year? A light-year is the distance that light can travel in one year - [...]
What is electricity? A bolt of lightning in the sky What is electricity made of? Everything in the universe is made of atoms. Those atoms are made of electricity. Atoms are [...]
This is a sphere. A sphere is a three-dimensional circle. Or you could say that a sphere is the set of all the points that are at the same distance from the center [...]
An Islamic astrolabe (832 AD) Who invented the astrolabe? About 140 BC, the Greek astronomer Hipparchus of Rhodes invented the science of trigonometry. What's trigonometry? Greek astronomy History of astronomy All our [...]
Volcano erupting Volcanoes are places where the plates of the Earth's surface have cracks in them, so that the very hot melted rocks that are under the tectonic plates bubble [...]
Evaporated sea salt Salt molecules are a combination of chlorine atoms and sodium atoms. These atoms mix together easily and, once they are mixed, the salt molecule is very stable [...]
In the Hadean Eon, Earth was covered with active volcanoes like this one. Why is it called the Hadean Eon? Scientists named the Hadean Eon after the Greek god Hades, [...]
Earthquake in Peru - Earthquakes can split the ground open! What causes earthquakes? What causes earthquakes? Earthquakes happen when the moving tectonic plates that make up the surface of the Earth [...]
Copper ore in Iran What is metal? Metals are atoms that attach themselves to other atoms in a particular way. Metal atoms, because of how their electrons are arranged, lose [...]
