# "The Martian" and weight units [closed]

In the book (and probably in the movie too, can't remember) there's several mentions of kilograms, with no mention of the difference between kilograms on Mars and on Earth, at least if you try to lift it. Not a huge plot hole, but one has to assume that the great minds at NASA would have some emphasis on the importance of this. Are all masses calculated by volume and density, or do they have special Mars scales around, or what?

The closest mention of this is when he says something like "Yay I'm superman because I can lift like twice as much on Mars as on Earth" (ever so slightly paraphrased).

• You can freely convert between the two with surpassing ease Commented Oct 11, 2015 at 11:05
• This is much more is a physics question explaining how mass and weight are different than any of the sci-fi elements in the book or film. Commented Oct 11, 2015 at 12:11
• @Richard it's even easier to convert between mass on other planets, given that it's the exact same... Commented Oct 11, 2015 at 12:15
• Haakon, if you edit the question to make it a bit clearer what you're asking and that it's a sci-fi question rather than a physics question, I'm sure it will get reopened :-) Commented Oct 11, 2015 at 12:18
• Grams are a measure of mass, not weight. On Earth, gravity is used to calibrate scales. On Mars, Martian gravity will be used to calibrate the scale, and a kilogram on Earth will be a kilogram on Mars. An Earth scale on Mars, of course, would give the wrong weight, and would have to be recalibrated. The point is that one kilogram of a given mass will contain the same number of atoms on Mars that it does on Earth. Commented May 9, 2016 at 1:58