So I saw a short on YouTube talking about how they proved a prediction Einstein made about double pulsars falling towards each other at the rate of 7 mm a day. My question; how the hell can they measure two stars that are roughly the size of LA, but the mass of our sun, moving 7 mm closer each day while in orbit of each other lightyears away? At that distance it’s gotta be a couple pixels on whatever they’re using to view them right?
In: Planetary Science
Nobody can actually *see* the pulsars, it’s all about timing. The pulsars each produce a sweeping “lighthouse beam” of radio waves that sweeps past us, creating a regular sequence of pulses (hence the name). When a pulsar is closer to us in its orbit the pulses arrive a bit early, when it’s far away the pulses arrive a bit late, so by measuring that we can precisely calculate how long it takes to complete an orbit.
By observing for many years using clocks with nanosecond accuracy, we can see the orbital period changing slightly, and from this (and knowing how gravity and orbits work) we can calculate the change in the radius of the orbit.
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