wasser_1@viking.DEC (John A. Wasser) (06/03/85)
The Twin Paradox occurs because of the contraction along the direction of travel of objects moving at high speed relative to the observer. Lets take a trip from Earth to a star 10 light-years away at a speed where the contraction is 1/2. Lets call this speed .5c (which is wrong). (V would realy be 211,985,280m/s or c/sqrt(2) or about .707c) The ship leaves Earth at this speed, goes to the star and instantly reverses direction (this will simplify the example). Observer on the ship moving relative to the Earth/Star system: Due to the contraction, the distance from the Earth to the star looks like 5 light years. Traveling 5 light years at .5c takes ten years. Reversing direction and traveling the other way also takes 10 years so the total trip time (measured in the ship) is 20 years. Observer on the Earth/Star system moving relative to the ship: Due to the contraction, the length of the ship seems to be half its normal length. The distance to the star is still 10 light-years because the observer is not moving along the vector between the Earth and the star. The Earth/Star system move past the ship for 20 years at .5c. At this time the star end of the Earth/Star system has reached the (stationary) ship. The system now reverses direction and moves past the ship in the opposite direction. In another 20 years of moving at .5c, the Earth has once again reached the ship. The total trip time (measured on the Earth) is 40 years. Much of this I derived for my own edification after reading "Einstein for Beginners". It explains why the speed limit on light implies contraction. -John A. Wasser Work address: ARPAnet: WASSER%VIKING.DEC@decwrl.ARPA Usenet: {allegra,Shasta,decvax}!decwrl!dec-rhea!dec-viking!wasser Easynet: VIKING::WASSER Telephone: (617)486-2505 USPS: Digital Equipment Corp. Mail stop: LJO2/E4 30 Porter Rd Littleton, MA 01460