 So get this I saw a commercial for one of those crazy weight loss plans on TV this morning Huh, what kind of wacko fad diet is it this time? It's got to be better than that all salt one we saw Actually this promised you could eat whatever food you wanted and still lose weight sounds sketchy And you don't have to exercise either sounds really sketchy. What's the catch? There isn't any Okay, you have to go to the moon Really, let's check this out. Totally at least we'll get to visit the moon Hi, we're interested in your extraterrestrial weight loss program. Yes, of course. We'll start by taking a baseline measurement How much do you weigh now miss? You know what why don't we have the gentleman weigh himself much better the scale weighs a hundred grams newly noted now for step two lift off So this is the moon, huh? How about that sir if you'll just step up for another weighing it says 16.6 grams well there you have it look at all that weight you've lost that will be five million dollars, please We take checks and all actually your scales wrong. What? It's calibrated for Earth and it's showing his mass incorrectly. I don't understand what you're talking about We can explain there are two different quantities that can be confused mass and weight Mass is the measure of how much matter an object like my body contains on the other hand weight is a force Measures how much a planet is pulling down on an object weight is measured in units of Newtons or pounds force Mass is measured in units of kilograms or pounds mass or slugs It's funny because we're slugs. Oh, I thought you were just homeless snails Yeah, we're not Mass and weight are related, but there's a big difference between the two how they're affected by the gravity of a planet John's mass isn't different from what it was on earth He hasn't lost or gained any matter and so he's a hundred grams here there and everywhere Although I almost threw up in the rocket on the way here. I'm glad you didn't I had a guy last week throw up It cost me a thousand bucks to clean you should really get some of those little paper bags for people I'm sorry As I was saying John's mass hasn't changed, but his weight has it's smaller here on the moon than it was on earth And that's because the gravity here on the moon is smaller than the gravity on earth Six times smaller to be exact, which means my weight is six times smaller, too I weighed point nine eight Newtons on earth, but I only weigh point one six Newtons here on the moon What if we went around to other planets like in this convenient rocket ship I happen to have right here On some planets John weighs less than he did on earth Mercury Venus, but just barely Mars Uranus And Pluto Pluto. I thought you said planets. Well, it's a dwarf planet. Does that count? I guess On other planets John weighs more than he did on earth like Neptune Saturn And Jupiter, and if we head to the Sun we are a lot heavier Do you guys smell something burning? It's like an s-cargo smell We should head back Okay, so I understand the difference between mass and weight, but now I'm all confused about my scale We measure our weight on the scale, but it gives the answer on kilograms, which is the unit of mass What's the scale really measuring? The scale measures your weight, but it displays mass It's able to make the conversion because it's calibrated to include the gravity of earth But whenever you're here on the moon the scale displays the wrong mass Self by new scale But hey, I promised a weight loss and you got a weight loss five million dollars, please True, but what people really want is a mass loss program We often use the words interchangeably on earth because the gravity is not changing Yeah, I want to get rid of some of my mass right here on my stomach area Or rather Molly wants me to get rid of it I just think you could eat a little less ice cream and go for a walk every now and then