Feeling Your Weight

One g is the normal pull of Earth's gravity — the force you feel standing still. Two g's means you feel twice your normal weight. Zero g means weightlessness.

G-forces aren't really about gravity at all. They measure acceleration relative to free fall. A fighter pilot pulling a tight turn at 9 g feels nine times heavier, and blood drains from the brain toward the feet.

Where your body meets g-forces:

• Standing still: 1 g
• Fast elevator start: about 1.2 g
• Roller coaster loop: 3-5 g
• Car crash at 50 km/h: roughly 30 g.