I was packing up some gifts to ship last night and re-used a bunch of the air pillows that Amazon uses.
I got to wondering - instead of air, wat would happen if the pillows were filled with helium? Would there be enough helium in the box to provide a useful weight reduction vs the cost of helium? This wouldn’t be useful on something sent by Parcel Post that’s already fairly cheap, but might be worth doing on a priority overnight package. Taking off a pound would net some significant savings. (Want nine pounds delivered tomorrow morning? Cough up about $120 for FedEx!)
As a side note, it would certainly provide amusement at the receiving end when they open the box and the packing materials start floating out!
Tipsy Turtle (an old mid to late 80’s Saturday Night Live cartoon skit) tried this and demanded payment from the Post Office becasue his package floated off the scale (he was shipping a helium filled ballon in the box).
I don’t think his money scheme worked.
Titpsy Turtle Theme song IIRC: Woman’s voice: Hey Tipsy Turtle walking down the street tell me what you’re gonna do. Tipsy: First I’m gonna bother everybody I meet then I’ll probably go home and get drunk.
I have no idea how I still remember that. I don’t remember seeing them in reruns.
also, helium would leak through the plastic and you’d soon have no cushion left whatsoever. Most plastics are pretty porous to helium atoms; heck helium is used to leak check piping in some manufacturing applications. Plus you’d need a BIG box to hold enough pillows/balloons to make any significant weight difference.
You can look at light that’s being reflected by the pipe. Helium, like all gases, has a unique ‘transmission spectrum’. It absorbs certain wavelenghts of light, so that when you refract white light coming through helium gas, you don’t see a smooth rainbow-pattern smear, but instead a smooth rainbow-pattern smear with little gaps in the wavelengths that helium absorbs.
If it were any other gas, you’d see the gaps in different places.
This is actually how they discovered helium, I’m told (looking at the emission spectrum of the sun, hence the name after the old sun god Helios). But I don’t know if this is how they would actually do it for pipe inspection. That part’s just a guess.
You use a mass spectrometer. That’s a device that ionizes gas and accelerate it with an electrical field, and see how far it bends in a magnetic field. That gives you the charge/mass ratio. You can tune it to only detect singly ionized helium.
I’ve used one but I don’ t know if it was a typical design. This helium leak detector was basically a vacuum pump connected to a mass spectrometer tuned to detect helium. To find leaks in a vacuum chamber, you’d hook up the leak detector to the chamber and use it to pump out the air. Then you go around with a helium tank and squirt helium at suspect spots (weld joints and connectors). When you hit the leak, helium gets sucked up into the chamber and into the mass spectrometer.
The only problem is that it is not sensitive enought to detect very small leaks. I used a halide torch detector to find leaks so small in pits and cracks in copper water lines that it took a magnifying slass to see them. The pipe was pressurized with “Freon” and the sniffer tube run around the pipe. Any halide gas (the freon) would turn the flame in the torch purple and the leak could be marked for repair.
Interestingly, even though the parcel might be lighter, the mass wouldn’t be reduced by helium packaging; since a great deal of the transportation by post involves accelerating the package laterally, the cost saving to the carrier would not be proportionally reduced.
The mass of the air displaced by the helium is greater than the mass of the Helium that displaces it. That is why the helium filled package is lighter than the corresponding air-filled package. The savings, if any, would be exactly proportional to the change in weight/mass.
There’s only one way to change the mass/weight ratio: change the gravity field. Since the helium package travels exactly the same route as an air-filled one would, any gravity fluctuations along the path are irrelevant. Inertial mass is (according to our most exacting measurements) completely equivalent to gravitational mass, so you can’t even use an ‘inertial’ argument to claim the mass isn’t reduced.
Right. the mass will be the same, but its weight will be somewhat less. And I don’t care what it costs the carrier to laterally accelerate a box. I just want my FedEx bill to be less!
So… it sounds like it would take so much helium to get a significant weight reduction that the box would be so large that I’d be paying “dim weight” (dimensional weight) - they assign additional weight to large but light boxes due to the space they occupy.
I’m sorry, I think you might be missing it still by just a bit. Think of it in terms of a rigid cube. A cube filled with helium at 14.7 psia is going to weigh less overall than a cube filled with air at 14.7 psia, because its mass is less. Each helium molecule has a realtive weight of about 4. Whereas an average air molecule is just over a relative weight of 28. Remember, when talking Ideal Gases, 1 mole of gas occupies 22.4l of space at 1 atm. And if those molecules in the mole are made up of lighter atoms, then the mass is less.
Think of it as stuffing a box with tennis balls, and with billiard balls of approximately the same size. Of course, I’m still talking Ideal Gases here, but the general principles hold.
If you measure the force required to laterally accelerate the rigid cube with helium at 1g, it will be shown that it is indeed made up of less mass. And if you put the cubes on a scale, the helium cube will exhibit less weight.
NYR407, I can’t believe someone beat me to it! Tippy Turtle was the first thing I thought of upon seeing this thread.
I loved how, when the package floated off the postman’s scale, Tippy began pounding on the desk shouting, “I WANT MY MONEY, I WANT MY MONEY!!” (he figured that since it floated, the Post Office must owe him!)
Also, a few quick calculations shows that since Helium only has a lifting force of about 1 gram per liter, a box that was one cubic foot in size would only lift one ounce total (i.e. the packaging would probably weight many times that).
