The missing 0.7% of mass becomes energy. The Sun converts about 4 million tonnes of mass into energy every second!
Fusion: light nuclei JOIN to make a heavier one.
- Powers the Sun and all stars
- Fuel: hydrogen isotopes (from seawater)
- Little long-lived waste
- Needs ~100 million °C on Earth: very hard!
Fission: a heavy nucleus SPLITS into lighter ones.
- Used in today’s nuclear power plants
- Fuel: uranium or plutonium
- Makes long-lived radioactive waste
- Chain reactions must be carefully controlled