Three. One to change it while the other two argue about how old the old one is.
Just one but every time he does he causes a blackout.
Salmon
None it is done by the automatic pilot.
1 and 12 people to say how inspiring it was
Because of his enthusiasm for Carbon-Dating.
Some old stuff just got dug up
Seven. One to install the bulb and six to figure out what to do with the old one for the next 10,000 years
