# Can we make a floating metal ball? **URL:** \ **Category:** Factual Questions\ **Created:** [March 15, 2008, 4:33pm UTC](https://boards.straightdope.com/t/can-we-make-a-floating-metal-ball/441462 "2008-03-15T16:33:50Z")\ **Posts on this page:** 5\ **Page:** 2
**Author:** ![Mijin](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mijin/32/9369_2.png) [@Mijin](https://boards.straightdope.com/u/Mijin)\ **Post date:** [March 16, 2008, 2:51pm UTC](https://boards.straightdope.com/t/can-we-make-a-floating-metal-ball/441462/21 "2008-03-16T14:51:31Z")
[QUOTE=Squink] Make the sphere big enough, and vacuum or special light gases are no longer needed: “Of a sphere with a radius of 1320 feet, the weight of the enclosed air is 1000 times greater than the weight of the sphere’s structure. If that volume of air was heated only one degree, the sphere would begin to float!” [/QUOTE] That’s quite some hot air balloon though. It’s a heck of a lot of air to heat, even if by only one degree. And then what? The sphere would barely float (since I presume 1320 must be the absolute minimum size), lose heat to its environment, and drift back down again. Playing devil’s advocate, I suppose a sphere based on a greenhouse effect could achieve a temperature gradient of 1 degree with its environment using sunlight only. But still, you wouldn’t want a metallic material for such a sphere – you need something transparent and insulating – and that’s what the OP is about. ---
**Author:** ![Derleth](https://avatars.discourse-cdn.com/v4/letter/d/b9e5f3/32.png) [@Derleth](https://boards.straightdope.com/u/Derleth)\ **Post date:** [March 16, 2008, 3:08pm UTC](https://boards.straightdope.com/t/can-we-make-a-floating-metal-ball/441462/22 "2008-03-16T15:08:29Z")
[QUOTE=Q.E.D.] Somehow, I think there would be severe FAA restrictions on a floating quarter-mile sphere. [/QUOTE] So we’ll just guide our ship to new lands. ---
**Author:** ![rbroome](https://avatars.discourse-cdn.com/v4/letter/r/838e76/32.png) [@rbroome](https://boards.straightdope.com/u/rbroome)\ **Post date:** [March 17, 2008, 2:57am UTC](https://boards.straightdope.com/t/can-we-make-a-floating-metal-ball/441462/23 "2008-03-17T02:57:33Z")
[QUOTE=Q.E.D.] Somehow, I think there would be severe FAA restrictions on a floating quarter-mile sphere. [/QUOTE] but it would be very easy to spot on radar! ---
**Author:** ![Jragon](https://avatars.discourse-cdn.com/v4/letter/j/e19b73/32.png) [@Jragon](https://boards.straightdope.com/u/Jragon)\ **Post date:** [March 17, 2008, 3:17am UTC](https://boards.straightdope.com/t/can-we-make-a-floating-metal-ball/441462/24 "2008-03-17T03:17:21Z")
[QUOTE=Q.E.D.] Somehow, I think there would be severe FAA restrictions on a floating quarter-mile sphere. [/QUOTE] As long as they don’t send in any pesky blue hedgehogs we’ll be fine! _Plays Death Egg Music from Sonic 3 & Knuckles_ Alternate ending: So long as they don’t send in any X-Wings we’ll be fine _Plays Imperial march_ ---
**Author:** ![The\_Flying\_Dutchman](https://avatars.discourse-cdn.com/v4/letter/t/9fc348/32.png) [@The\_Flying\_Dutchman](https://boards.straightdope.com/u/The_Flying_Dutchman)\ **Post date:** [March 18, 2008, 4:47am UTC](https://boards.straightdope.com/t/can-we-make-a-floating-metal-ball/441462/25 "2008-03-18T04:47:03Z")
Really hard to follow some of this stuff, but what I want to know, given that there is technology to manufacture “foamed” metal is if we are closer to a reasonable solution for the OPs requirements by using a foamed metal skin (closed cell for vacuum retention) of say 50% density. My guess is that there would be 8 times the resistance to buckling. [Previous page](https://boards.straightdope.com/t/can-we-make-a-floating-metal-ball/441462.md?page=1)