Parallax
- demo using your 2 eyes
- represent position of earth 1/2 year apart
- separation 4 inches rather than 2 AU!
- place one finger 1.5 ft. away and one finger 3 ft. away
- blink from eye to eye
- note apparent shift of fingers compared to distant wall
- nearer finger moves twice as far
- This is parallax
- by measuring angle, distance can be inferred
- Small Angle Formula, naturally!
- If stars are much further than 1 AU away, parallax very small
- empty step in 100x “scales of universe” tour
- nearest star 4 ly ~ 200,000 AU
- maximum parallax 1 arcsec, a very small angle to measure