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0 pointsAllegedAlec7y ago0 comments

I like how Paulien Hogeweg phrased it too: "thinking in the most interesting simplification" [0]

I always thought the 'but models are wrong' is quite a weak excuse. Newtonian physics is a wrong model of how the universe works. Using it though; we put a man on the moon. Einsteinian physics are incomplete, but it allows us to use satellites moving at roughly 10KM/s to pinpoint our location to within a few metres.

A model's usefulness is not about how accurately it describes what is happening, but about whether it describes what happens at a certain meso-scale accurately.

[0]: http://www.labtimes.org/labtimes/issues/lt2011/lt07/lt_2011_...

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phkahler7y ago

>> Einsteinian physics are incomplete, but it allows us to use satellites moving at roughly 10KM/s to pinpoint our location to within a few metres.

Funny. I know how GPS works and that knowing the SAT locations is critical, but I never thought about how fast they are moving. They need to transmit their own position and time with great accuracy. In particular, don't they have to transmit their time and position at the time of transmission? That is a more interesting problem than I realized.

PeterisP7y ago

GPS satellites aren't really transmitting their location at any particular time, they're transmitting the so-called ephemeris and almanac data that has information about their orbits so that you can calculate their position at the time of transmission.

crankylinuxuser7y ago

And if you have a ADALM-PLUTO, you can download the brdc file (ephermis) and spoof all 12 satellites to a location of your choosing here: ftp://cddis.gsfc.nasa.gov/gnss/data/daily/2019/brdc/

https://github.com/Mictronics/pluto-gps-sim-win32

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