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What are those personalized audio cones above me at the museum?

codybaldwin — Mon, 23 Nov 2009 20:14:01 -0800

What are the personal/individual audio cones are museums called? Is it possible to make one at home relatively inexpensively? I can't find any information on them. This may be because I don't know what they're called, and so I couldn't really adequately look to see if this has even been asked before. Regardless, these are sort of halves of spheres that hang from above and project audio onto guests of museums. You also sometimes see them at internet and computer gaming cafe's.

So, what're they called?
How do they work?
Can I make one relatively cheaply?

Beach balls are too small. I need bigger spheres.

abirae — Tue, 01 Sep 2009 06:34:27 -0800

GiantSphereFilter: Help needed creating a 4 foot wide tennis ball. Details inside A friend of mine was hired to make props for a tv show in New York. The next one he has to make is a 4 foot wide tennis ball. He has been looking all over New York and the internet for four foot spheres to use as armature. It is trickier than you would think.

Here are some armature ideas that haven't worked so far:
- Yoga Balls - seem to max out at about 3 feet in diamater.
- Beach balls - Even when advertised as huge, have been too small when inflated.
- Hoberman Spheres, tents and umbrellas - too tricky to build on

My friend is good at this sort of thing, and may just build the sphere out of rings of pink industrial foam, but I thought the hive mind might have some good ideas for easier ways.

spherical geometry!

klanawa — Wed, 04 Feb 2009 15:52:56 -0800

can you help me compute the area of a triangle on the sphere? i have this pretty much down:

the formula for the area is:

a = R^2 ((A+B+C) - pi)

where:

a is area
R is the radius of the sphere
A, B and C are the triangle's angles

where i'm stuck is finding the angles A, B and C. i'm starting from 3 geographic (lat,lon) points. i think i pretty much get the principle there (finding the normals to the planes represented by the lines between the three points, etc.). but i can't quite make the leap.

wolfram and the rest have helped with the theory somewhat, but this math retard needs a bit of step-by-step hand-holding. i've worn out google trying to find a site that doesn't make a lot of unreasonable assumptions about my competence as a mathmatician.

Best way to tile a sphere ?

silence — Mon, 02 Jun 2008 07:07:53 -0800

How can I tile a sphere using the minimum number of differently shaped units? I have a 3 meter diameter sphere and I need to tile it using units that are each about 400 square cm (ie like a 20 x 20cm square). The units must be flat (ie, not spherical triangles). I'm currently thinking of using a geodesic tiling, but a (for instance) a 5V geodesic tiling results in (i think) 6 different tile shapes, and also has the problem that the density of tiles isn't constant over the surface - there are obvious visual artefacts where the tiles bunch up. I need to try to minimise the number of different types of unit, and to optimise the appearance so that it's as even as possible. Are there any better ways of tiling a sphere?

Mountain Marbles

Tube — Mon, 12 Nov 2007 21:40:02 -0800

Has anyone here heard of "Mountain Marbles"? I discovered this term in an issue of Mechanix Illustrated magazine from 1965. I've posted a photograph of the passage on Flickr here.

I'm curious if anyone has heard of using flowing water to "machine" a small stone into a sphere. I've read some of the Foxfire series books, and the Whole Earth Catalog, but I don't recall seeing anything about this. From the text I gather this is an Appalachian craft. Everything I know about this subject is what I've read in this tantalizing passage. Is it possible to create a stone sphere regular enough to actually play marbles with? Has anyone here done this, or even read about it elsewhere?

Perhaps Frank Wynne was pulling our leg...

Do you remember news of a strange steel sphere?

Tube — Mon, 05 Nov 2007 20:13:35 -0800

Does anyone remember news of an anomalous event that occurred in the early 1970's, namely a family finding a large steel sphere in their backyard? I remember encountering this news story many years ago, probably in Fate or Argosy magazine, and I suspect I may have read about it again in on of those Reader's Digest "Mystery" compilation volumes. The news story, as I remember it, was that one day a family found a large (perhaps 2 feet in diameter) steel sphere in their back yard. I think it occurred in one of the Southern states, perhaps Florida. It may have been made of stainless steel, and was thought much too big to be a ball bearing.

I recall this story now, in light of a comment in today's Giant Sphere post about a spherical "pig" being used to clean out the inside of a pipe system; I recall this was suggested as a prosaic explanation for the nature of the large steel sphere.

What would happen if you could create a perfect two-way mirror into a sphere?

Lownotes — Tue, 30 Oct 2007 06:37:01 -0800

What would happen if you could create a perfect two-way mirror into a sphere? Imagine a hypothetical perfect two-way mirror. All light passes through one side, no light can penetrate the other.

Now, make it into a sphere with the mirrored surface on the inside.

What will happen as it collects light? Will it collect light forever? Will it fill up and burst like a supernova? How would it look to an outside observer?

Bubbles

Blazecock Pileon — Tue, 07 Aug 2007 06:55:29 -0800

Maximal volume of an ellipsoid... The volume of an ellipsoid is: 4πabc/3

An ellipsoid is defined with the function: x^2/ a^2 + y^2/ b^2 + z^2/ c^2 = 1

In the case where the sum a + b + c is a fixed value, how might I derive that the ellipsoid of maximal volume is a sphere?

I'd expect to show that a = b = c but am not certain where to start.

Note: This is a "homework" question, in that I am working on some math by myself to get back up to speed on some stuff I did many years ago. I'd appreciate hints rather than a full solution. Feel free not to answer if this bothers you.

Finding old, out of print comic books online?

aladfar — Tue, 23 Nov 2004 18:07:44 -0800

Digital Comics: I'm looking to download .cbr and .cbx archives of comic books. Not so I can steal the latest X-Men book (though I know piracy is rampant in this sphere), but so I can read interesting and long out of print books on my computer. The Metal Men, for example, fascinate me.

The trouble is, I can't seem to find any repositories of old comics via Google, BitTorrent, etc. I know they're out there - any help?

Replacement desktop systems on XP?

twine42 — Fri, 16 Apr 2004 08:46:06 -0800

The current MeFi thread on Sphere reminded me... Does anyone use a replacement desktop system on XP? Which one and why did you choose to use it? This thread, btw. Why didn't AxMe allow urls in the question?