Summary
Summary Notes on physics
- Course
- Phy 1124
- Institution
- University Of Ottawa (U Of O )
Summary of 3 pages for the course Phy 1124 at U of O (Notes on physics)
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What Makes a Clock a Good Clock?● Most readers will be wearing a quartz wrist watch, hearing the ticks of a
mechanical mantlepiece clock or long case clock, and looking at their iPads,
tablets, computers, phones or similar, but all three clocks will be showing slightly
different times.
● Pulsar clocks differ in one important respect from everyday life clocks: the
intervals between ticks are increasing. The Crab pulsar's tick's intervals have
increased by 0.6 ms over 42 years.
● A clock using the Crab Nebula as its regulator is about 80,000 times better than a
household long case, or grandfather, pendulum, clock, because its rate of time
loss is increasing with each tick by 1.4 1014 seconds.
PAGE 28
● The Crab nebula clock is slowing down with each tick, but the amount by which it
is slowing down is increasing far more rapidly than the number of ticks.
● The Crab nebula clock out-paces the long case clock with compound interest,
and after 42 years, the long case clock is 4 days 13 hours and 12 minutes late.
PAGE 29
● Pulsars make very good clocks, comparable in their performances with the best
atomic clocks of just a few years ago.
● The long case clock was losing three minutes per week. It could either have been
a steady loss of time or the variations could have been much wilder.
PAGE 34
● In order to regulate a clock, we must distinguish between its accuracy (how well
the clock's reading agrees with the correct time at a particular instant) and its
stability (how much its readings vary randomly over a period of time after it has
been well regulated).
Pulsar Clocks
● Pulsars' spins are slowing down, so a clock based upon a pulsar's ticks would
drift, but the rate of drift would also be accelerating.
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