Time standards are now based on atomic clocks. A promising second standard is based on pulsars, which are rotating neutron stars (highly compact stars consisting only of neutrons). Some rotate at a rate that is highly stable, sending out a radio beacon that sweeps briefly across Earth once with each rotation, like a lighthouse beacon. Suppose a pulsar rotates once every 1.596 806 448 872 75 4 ms, where the trailing 4 indicates the uncertainty in the last decimal place (it does not mean 4 ms).

Question

Time standards are now based on atomic clocks. A promising second standard is based on pulsars, which are rotating neutron stars (highly compact stars consisting only of neutrons). Some rotate at a rate that is highly stable, sending out a radio beacon that sweeps briefly across Earth once with each rotation, like a lighthouse beacon. Suppose a pulsar rotates once every 1.596 806 448 872 75  4 ms, where the trailing  4 indicates the uncertainty in the last decimal place (it does not mean  4 ms). 
(a) How many times does the pulsar rotate in 21.0 days?

(b) How much time does the pulsar take to rotate 3.0  106 times? (Give your answer to at least 4 decimal places.)
 s

(c) What is the associated uncertainty of this time?
  s

bobpursley · Answer

I will be happy to critique your thinking.