An earthquake is a sudden and sometimes violent shaking of the ground.
Scientists refer to a narcotic as a drug that stops pain, but the word can be used in other ways as well.
Gravity is a fundamental force that attracts objects with mass to other objects with mass. It decreases with distance.
A theory is an explanation of how part of the world works. It’s one that’s been tested many times and in many ways.
Plastics are made of long polymer chains and can take on many shapes. Unfortunately, they stick around for a long time.
Amphibians are ectotherms that live dual lives — they start off in water, breathing with gills, and end up breathing air with lungs.
A chemical is anything made of two or more atoms bonded together in a fixed structure. Chemicals make up the world around us.
Asteroids, meteors and meteorites are all space rocks. But one is in orbit, another is in the atmosphere and the third is on the ground on Earth.
Vaccines help the body develop immunity to a disease. They are biological mixtures that imitate a disease so the body can defend itself.
Carbohydrates are molecules with carbon, oxygen and hydrogen. Animals break down these chemicals in food to get energy.
What do solar energy, the solar year and solar flares have in common? They’re all related to the sun.
People leave things where they’ve been — old buildings, trash heaps and human skeletons. Archaeology is the study of those left-behind things.