The coolest thing I read last week

The timing pulses in question can be thought of as places in the transmitted wave trains where there is a particular phase reversal of the circularly polarized electromagnetic signals. At such places the electromagnetic field tensor passes through zero and therefore provides relatively moving observers with sequences of events that they can agree on, at least in principle.

from “Relativity in the Global Positioning System” by Neil Ashby

Really that paragraph has everything. Timing Pulses. Wave Trains. Phase Reversal. Tensor Fields Passing Through Zero. Seriously it’s amazingly cool. I can barely comprehend what it’s on about, and that’s just from the introduction. But it just emits a level of sci-fi geekery that you rarely find. Just one of the daily gems I get from twitter. Specifically from Nick Porcino (Meshula), go follow him.

I now have to go make something where a tensor field passes through zero.