# How does your smartphone know your location?

The mechanism that your phone uses to know the location of the user originated from quantum physics.

### Satellite

What a satellite does is that it broadcasts signals that venture from space to the phone at the speed of light. The time when the signal arrives, the phone records it and thus by calculating it gets the distance of the time through the basic calculation method of distance=c x time, where ‘c’ is the speed of the light and time determines how long the signal has traveled.

### Atomic Clocks

Atomic clocks are so exact that they would not lose or gain a second no matter if they run for the next 300 million years. These are the clocks that work because of quantum physics. And all clocks should have a constant frequency. To be specific , they should carry out some repetitive action so that equal increments of time are marked.

### Quantum Physics

The transition between two energy levels of an atom in the tik-tok of an atomic clock is maintained by transition. This is where quantum physics comes into effect. According to quantum mechanics, though energy is carried by atoms, they won’t be able to take on any arbitrary amount. Rather, atomic energy is focused on a precise set of levels which are called quanta.

So, in case an atom transition occurs from a certain energy level to another, quantum mechanics emphasizes that the energy difference would be equal to a characteristic frequency, multiplied by constant. This is where the change in energy will be equal to a number known as Planck’s constant that times the frequency. This characteristic frequency is what actually one need to make our clock

### GPS Satellites

Cesium and rubidium is what GPS satellites depend upon as frequency standards. IN cesium 133, the characteristic frequency will be 9,192,631,770 Hz which is 9 billion per second. Each cesium 133 atom in the universe oscillated at a common frequency. So, with the help of an atomic clock, the accurate reading to within 1 billionth of a second is observed.

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