milos 2: Negde sam cuo da pocinje da lebdeti

Would a balloon filled with vacuum instead of helium float?

If you have read the article How Helium Balloons Work, then you know that a liter of air at sea level weighs about 1.25 grams. A liter is 1,000 cubic centimeters, or about 61 cubic inches -- the size of a 1-liter soda bottle. A liter of helium, on the other hand, weighs about 0.18 grams. If you weigh a 1-liter bottle filled with air and then weigh the same bottle filled with helium, it will weigh about 1.07 grams less. If the bottle itself weighed less than a gram, you couldn't weigh it at all -- it would float! You could turn the scale upside down and put it above the floating bottle to check its negative weight! Generally, a balloon has to be several liters in size before the 1-gram-per-liter weight difference of helium vs. air is enough to overcome the weight of the balloon itself and float.

If you could somehow fill a 1-liter bottle with a vacuum, it would float even better. A perfect vacuum weighs zero grams, so a liter of perfect vacuum weighs 0.18 grams less than a liter of helium. The problem, of course, is that building a lightweight container that can hold a vacuum is not nearly as easy as building a fabric envelope that can hold helium. The phrase Nature abhors a vacuum sums it up nicely. If you could figure out a way to do it, however, you would be set -- your vacuum balloon would float!

Note that you would not need to have a perfect vacuum. Any air that you take out of the envelope will lower the weight and cause lift.

Shadowed:
Sto se tice ovog na videu - ne cudi, em je nepogodnog oblika...

Shadowed:
...em tim neujednacenih hladjenjem podsticu deformaciju

Shadowed: Medjutim, pitanje je da li postoji neki materijal kojim bi se to moglo postici.

Bojan Basic: ... — to hlađenje im je bio metod da naprave vakuum unutra, ...

Bojan Basic: Nije poenta u neujednačenom hlađenju — to hlađenje im je bio metod da naprave vakuum unutra, a pravljenje vakuuma na taj način vodi do sporije deformacije nego pravljenjem vakuuma prostim isisavanjem sadržaja.

Shadowed: Postize se vakuum hladjenjem (tj. priblizava se vakuum-u, nista od toga nije apsolutni vakuum) jer se smanjuje pritisak.

Nema veze sto je broj cestica isti.

Da, ali kada neko telo ohladis u jednom delu vise nego u drugom ono ce se deformisati a upravo je pravilan oblik bitan za izdrzavanje spoljnog pritiska (sfera bi bila najizdrzljivija).