Science You Should Know

The small stuff

• Everything is made of atoms: a nucleus of protons and neutrons, with electrons around it.
• The periodic table lists all the elements, from hydrogen (the lightest and most common) to the heavy ones.
• Water is H₂O: two hydrogen atoms and one oxygen atom.

Life

• Cells are the building blocks of all living things.
• DNA is the instruction manual inside your cells. Its double-helix shape was described in 1953 by Watson and Crick, using X-ray images made by Rosalind Franklin.
• Evolution by natural selection (Charles Darwin, 1859): living things that are better suited to their environment survive and pass on their traits.
• Photosynthesis: plants use sunlight, water and carbon dioxide to make food and release oxygen.

Health

• Germ theory: many diseases are caused by tiny organisms like bacteria and viruses.
• Antibiotics kill bacteria (Alexander Fleming discovered penicillin in 1928). They don’t work on viruses like colds and flu.
• Vaccines train your immune system to recognize a disease before you catch it.

The big stuff

• Gravity (Isaac Newton, 1687) keeps you on the ground and the planets around the Sun.
• E = mc² (Albert Einstein, 1905): mass and energy are two forms of the same thing.
• Light travels about 300,000 km per second. Sunlight takes about 8 minutes to reach us.
• The universe began with the Big Bang about 13.8 billion years ago. Earth is about 4.5 billion years old.
• The greenhouse effect: gases like carbon dioxide trap heat. Burning fossil fuels adds more, which is warming the planet.