Editing 89: Gravitational Mass

{{comic
| number    = 89
| date      = April 14, 2006
| title     = Gravitational Mass
| image     = gravitational_mass.jpg
| titletext = She's so fat the attraction goes up as the CUBE of the distance instead of the square
}}

==Explanation==
[[Black Hat]] launches into what appears to be an in-depth exposition about the {{w|Equivalence principle|equivalence of gravity and inertia}}. As he notes, an object's "inertial mass" (the degree to which it resists a change in velocity) and its "gravitational mass" (the degree to which it attracts and is attracted by other objects) are the same. He states that there isn't an obvious reason why they should be related like this, suggesting that a high-inertia, low-gravity (or a low-inertia, high-gravity object) should be possible.

However, it transpires that this whole speech is just a convoluted build-up to a {{w|"Yo mama" joke}} along the lines of "she's fat and not that attractive." Black Hat then can't be bothered with, or can't figure out, the lengthy route to his punchline, so just goes for a straightforward insult instead.

A well known joke format goes: "Yo' momma's so fat, when she X, she Y." For example: "Yo' momma's so fat, when she sits around the house, she sits ''around'' the house!" Variations play with the format, for example: "Yo' momma's so fat, she fell in the Grand Canyon and got stuck!"  A "Yo' Momma" joke also appears in comic [[681: Gravity Wells#Cut outs and sketches|681: Gravity Wells]] to the right of Jupiter.

The title text is a play on the law of gravitational attraction, which diminishes as the square of the distance, so if the distance between two objects doubles, the attraction is reduced to a quarter, and if the distance is halved, the attraction quadruples. Black Hat is saying that the attraction goes up as the cube, so if the distance is halved, the attraction increases eight-fold, and decreases eight-fold when the distance doubles. This implies that "your momma is so fat, she breaks the laws of physics (and does so in a way that she isn't as attractive as physics would dictate, given enough distance)." The title text is slightly ambiguous; it seems to say that as distance increases, the attraction increases, but it doesn't explicitly state whether the distance is increasing or decreasing.

Note: Contrary to Black Hat's explanation, and as per Albert Einstein's theory of {{w|general relativity}}, the reason that objects have equal gravitational and inertial mass is that anything with mass or energy causes a warping of space-time that causes all other objects (including such objects that classically shouldn't be affected, like photons) to experience the same gravitational acceleration.

==Transcript==
:[Black Hat standing.]
:Black Hat: Gravitational mass is identical to inertial mass. That is, the amount of inertia something has and the amount of gravity it has are effectively the same. What's interesting is that there doesn't seem to be any reason this should be true. One could imagine an extremely large object with lots of resistance to force and no gravity (or vice versa), but this is never observed.
:[Black Hat still standing. The panel is now shorter.]
:Black Hat: You know what? I'm just gonna skip the rest of the buildup and say it: Yo mama's fat.
{{comic discussion}}
[[Category:Comics featuring Black Hat]]
[[Category:Physics]]
[[Category:Your Mom]]
[[Category:Science]]
[[Category:Math]]
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