While moving to Pluto would cause drastic “weight loss”…

…it won’t do a thing for your mass.

The science museum where I work (<3!) has a scale that displays how much you would weigh on various astronomical bodies. I was standing nearby when a family from the UK stepped on, and one of the mothers expressed mild dismay that the display didn’t show both pounds and kilograms. I just had to jumpĀ in.

The display would be very uninformative if it displayed kilograms, as the number would be the same for every single planet. While pounds are a unit of force (like the Newton), kilograms are a measure of mass, not weight.

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Scientific Pet Peeve #1: Mass vs. Weight

Everyone has their pet peeves; unsurprisingly, at least a few of mine are science related.

Most people wouldn’t give a second thought to hearing someone say that something “weighs” twenty kilograms. I physically shudder whenever I hear or read such phrasing- and when I was a textbook editor, said shuddering was usually channeled straight into my red pen. Some of the first things you learn or teach in an intro physics class are the facts that mass is measured in kilograms, weight is measured in Newtons (or pounds), and mass and weight are not the same thing.

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