Science works: the GPS case

 Relativity theory is a great practical example of how, and why, science actually works.

Science is true because it works *). Science allows us to drive cars, fly airplanes, make video-calls, cure diseases, and save lives.

But science requires education to be discussed. Otherwise it's like magic **). People without scientific education cannot understand its language, and cannot distinguish science from magic. 

This is how you get stupid conspiracy theories, religion, and antivaxers.

As a great example, here's a great story about our GPS navigation. 

You know, we open Google maps or Waze on our phone, and it gives us precise directions on how to get home. Behind this every day tool there's an incredible amount of another and engineering. 

Gps positioning works by measuring and comparing frequencies of signals sent by satellites. 

There are 30 GPS Satellites orbiting the Earth. Designing satellites and sending them to orbit the earth is an incredible scientific and engineering accomplishment in itself. 

Each satellite broadcasts towards Earth a signal with: the satellite’s location in space, and the exact time the signal was sent. 

Each phone has a GPS receiver that continuously listens to the signals from 2-4 satellites, and continuously measures its distance from them based on the time needed by the signal to reach the phone. Then the phone calculates its own position, based on 1-4 such distances (theoretically min 4 for correct trilateration, but you can get reasonable estimations with less, if using additional local data such as GSM towers and wifi-s).

And the beauty part? Nothing would work without taking into account Einstein's theory of relativity. 

Because the clock of each satellite is slightly different from the clock of your phone and the time on Earth. Because satellites move faster, and their gravity field is lower.

So the time of their signals must be continuously updated to account for this difference.

This is why we know that relativity theory works. Because we can place satellites in orbit with precision, and we can then calculate the position of every phone also with incredible precision, by adjusting for the time difference between objects in space, correctly predicted by Einstein 100 years ago, when there were no satellites, phones or GPS.