Braingle: 'Weight, How is That Possible?' Brain Teaser

Weight, How is That Possible?

Science brain teasers require understanding of the physical or biological world and the laws that govern it.

Puzzle ID:	#34428
Fun:	(2.94)
Difficulty:	(2.39)
Category:	Science
Submitted By:	bigSWAFF_69_
Corrected By:	RomanG417

We all know that if you weigh yourself on the moon, it is less than your weight on the Earth. Can you tell me something that actually weighs more on the moon than on Earth?

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Comments

natureluver Dec 16, 2006	Yay 1st 1! good teaser
Punk_Rocker Dec 16, 2006	Wow, that's interesting. Good teaser!
_numpty_ Dec 16, 2006	Except that the helium balloon would burst dut to the pressure difference.
leftclick Dec 17, 2006	I'm not sure this one's quite right. I hope I don't start anything here but... The reason the balloon floats on Earth is because, while it does have weight (and can, in fact, be weighed, e.g. in a vacuum) that weight is less than that of the air around it (hence "lighter than air") If it does in fact "fall" on the moon, that is because there is no atmosphere. (I think it would have to be quite close to the moon's surface for this to happen, because of the moon's weak gravitational field) Weight is a product of mass and gravity. The mass of the balloon is constant (it is always made up of the same molecules). Gravity is lower on the moon than the Earth. Therefore, the weight of the helium balloon is less on the moon than it is on the Earth! (I also agree with Numpty, although I was assuming it was a "special" balloon made of some NASA style rubber that can withstand such pressure differences )
Kiroho Dec 18, 2006	leftclick is correct. The Helium does in fact weigh less on the moon as well. It is just that on the moon there is no heavy atmosphere for it to float upon.
unklemyke Dec 19, 2006	And, While we're being picky and scientific, it is not true that thebaloon cannot be weighed on earth. If you attach it to a spring balance, you will find out that it has negative weight, or - as the fly boys call it - "lift."
stil Jan 02, 2007	Our science museum weighs gases [in sealed jars] in a vacuum. Lower gravity would keep to proportions. In a dome pressurized to one atmosphere, a balloon would have its same lifting capacity, but its ascent would be slower because whole air accelerates into volume of space beneath the rising balloon under weaker gravity.
coolcow35 Jan 03, 2007	I voted easy and boring because it is.
LeafFan4life Feb 28, 2007	swaff thinks hes cool.....that is all i will say you guys try to determine what I mean by thinks
Jimbo Mar 06, 2007	Well I kinda liked it until I read the comments. I tend to agree that the answer is wrong and it should have been a science teaser anyway. I should have thought a bit further and realised that with a bit of physics, the mass of the molecules can be calculated and muliplied by the gravitational constant. You don't need to weigh it to determine its weight! Go Mathematics!!!
al111 Nov 03, 2007	Not really situation more of a science one but still it was ok 7/10
TRomo9999 Dec 23, 2007	Very clever, Keep up the good work!
Herman Apr 30, 2008	Yup, above comments are right. At least get a teaser's answer right before you submit it. I need some of that NASA rubber for, well, you get the idea....
monkeybar Nov 03, 2010	yes and no. clever for evryday talk but not very good for a scientist.
Skybet Oct 22, 2011	I agree that its not technically "right" but I think he means accouting for atmospheric differences between the Earth and Moon too, not just gravity. More of a trick for me but still works.
JasonD Apr 01, 2012	I believe this version is fine, and it DEFINITELY belongs in this category. Now somebody should make a version refuting this and put THAT in the science category.
Babe Jan 13, 2013	All I can say is "Ho Hum!" (
cutebug Jan 13, 2013	I'll check it out on my next trip to the moon. And to GW
auntiesis Jan 13, 2013	Didn't get it, but I'm not a science kinda gal. Lots of information in the comments that I didn't know.
spikethru4 Jan 13, 2013	If, as unclemyke says, the balloon has a negative weight on Earth, but a positive weight on the Moon due to the lack of atmosphere, then surely it does, in fact, weigh more on the Moon than on Earth?
elentir Jan 14, 2013	@spikethru4 - The balloon on earth doesn't really have negative weight. It's just that the buoyancy of the balloon gives it the appearance of negative weight. You still weigh the same either on land or in the water, but your buoyancy in water gives the impression that you weigh less. If you measure the weight of a balloon in a vacuum chamber (this removes any buoyancy effect and the balloon will not float) both on earth and on the moon, the weight will be significantly less on the moon.
spikethru4 Jan 15, 2013	Thanks, @elentir, that's a good explanation. I wasn't altogether comfortable with the concept of 'negative weight', since the mass must be positive and the gravitational force is positive, therefore weight must also be always positive. It's clear now that the air resistance is a separate force that counteracts the weight, giving a resultant force in the opposite direction (i.e. upwards).