Editing 1473: Location Sharing

{{comic
| number    = 1473
| date      = January 14, 2015
| title     = Location Sharing
| image     = location_sharing.png
| titletext = Our phones must have great angular momentum sensors because the compasses really suck.
}}

==Explanation==
{{incomplete|First draft.}}

In this comic, [[Megan]] is visiting a website on her mobile phone. After loading it, the website {{w|Location-based service|asks for her location}}, which Megan permits the phone to give. The choice between allowing or denying a website or app access to certain information is common among smartphones. The term "location sharing" specifically refers to when a smartphone user shares their location with such an entity. An example is a weather app which would need your location in order to find the correct forecast.

Megan is then asked her {{w|momentum}}, which she denies. The joke is based off of the Heisenberg {{w|uncertainty principle}}, which, in quantum mechanics, states that one cannot accurately know both the location and momentum of any particle simultaneously. In the context of the comic, Megan acknowledges the website's attempt to violate the uncertainty principle by saying "nice try".

It might also refer to security problems that appear if an untrusted application is given access to the gyroscope data.  Access to gyroscope data can be used for reading passwords entered into the on-screen keyboard or even guessing keyboard strokes on a keyboard lying on the same table as the phone.

It could also be an attempt to get [[Megan]] to unwillingly reveal her weight, as the her weight can be inferred by dividing the momentum with her velocity (the velocity is obtained via the location information). That could also explain the "Nice try" remark.

The title text refers to the inclusion of {{w|gyroscope}}s in modern cell phones that measure angular momentum, mostly to detect when the phone is tilted, but also used in a few mobile games. Randall suggests the poor accuracy of the compasses in mobile phones (measuring the angular position) is due to the gyroscopes being too good. (If both the gyroscope and the compasses were completely accurate, it would violate the uncertainty principle). Modern phones also include varied technologies (such as GPS) to pinpoint the user's location, with varying degrees of accuracy.

There is no way to measure absolute momentum directly in a mobile phone (well, anywhere else either). This is done normally by differentiating the position in time (from GPS signal) or by integrating the accelerometer signal. In the first case you obtain the average speed, the second technique is subject to numerical error adding up in time.

The uncertainty principle has previously been referenced in [[824: Guest Week: Bill Amend (FoxTrot)]]. It has also been discussed in relation to the two comics [[1404: Quantum Vacuum Virtual Plasma]] and [[1416: Pixels]].

==Transcript==
:[Megan is holding her phone. Above her is the text she can see on the screen:]
:This website wants to know your location.
:[Two buttons are below this text. The first is white with a black frame and black text. The second (the chosen button) also has a black frame, but inside the frame is a black rectangle with white text. Around the chosen button are small lines indication rays.]
:Deny
:'''Allow'''


:[Megan is holding her phone.]


:[Megan is holding her phone. Above her is again the text she can see on the screen. She makes a comment this time.]
:This website wants to know your momentum.
:[Two buttons are below this text. The first (the chosen button) has a black frame, but inside the frame is a black rectangle with white text. The second is white with a black frame and black text. Around the chosen button are small lines indication rays.]
:'''Deny'''
:Allow

:Megan: Nice try.

{{comic discussion}}
[[Category:Comics featuring Megan]]