# Uncertainty of time

1. Sep 8, 2004

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 1.424 806 448 872 75 2 ms, where the trailing 2 indicates the uncertainty in the last decimal place (it does not mean 2 ms).
(a) How many times does the pulsar rotate in 21.0 days?
(b) How much time does the pulsar take to rotate 1.0 x 10^6 times? (Give your answer to at least 4 decimal places.)
(c) What is the associated uncertainty of this time?

For this problem I am unsure of how the uncertainty is calculated. I understand parts a and b but not C. Please help.

Last edited: Sep 8, 2004
2. Sep 8, 2004

### humanino

Why don't you use upper and lower possible values for the period, calculate the two corresponding answers and make the difference between them ?