After watching iron man I really wanted a hologram and my best idea would be to fill a room with a non toxic gas and use multiple microwave beams that intersect to create the exact frequency which causes the gas to glow at one point in 3D space. I don't know much about chemicals to know which gas would work if any.

Anyone know of a gas that would do this?

IIRC it's been done with air, but it's really freaking loud (basically causing a gazillion little explosions).

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Original post by Hodgman IIRC it's been done with air, but it's really freaking loud (basically causing a gazillion little explosions).

Any links?

I guess the RF power levels required to ionise the gas would be quite high, possibly high enough to be a serious health hazard. Maybe low pressure gas would be easier to ionise, but still, I wouldn't want to stand near the thing.

I don't want to stand in the microwaves.

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Original post by szecs I don't want to stand in the microwaves.

Yeah, that's why I was thinking of using a 3D camera like Xbox Kinect to sense where the user is in the room and dynamically turn off the RF beams. I think it would be possible to avoid most if not all exposure to RF radiation and if the thing brakes and a couple beams do hit you I don't imagine it will do you much harm.

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Original post by SteveDeFacto Quote: Original post by szecs I don't want to stand in the microwaves. Yeah, that's why I was thinking of using a 3D camera like Xbox Kinect to sense where the user is in the room and dynamically turn off the RF beams. I think it would be possible to avoid most if not all exposure to RF radiation and if the thing brakes and a couple beams do hit you I don't imagine it will do you much harm.

Hope your insurance is up to date.

I've seen a YouTube video of some Japanese research doing that but using lasers. Let me see if I can find the link :

Here it is :


http://www.aist.go.jp/aist_e/latest_research/2006/20060210/20060210.html

Uses intersecting laser breams to create small mico burst of plasma. It has an annoying buzzing sound when operating.

-ddn

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Original post by ddn3 I've seen a YouTube video of some Japanese research doing that but using lasers. Let me see if I can find the link : Here it is : http://www.aist.go.jp/aist_e/latest_research/2006/20060210/20060210.html Uses intersecting laser breams to create small mico burst of plasma. It has an annoying buzzing sound when operating. -ddn

Does anyone else think of a lightsaber when they watch that?
Also I think by simply using a higher frequency laser they can make the sound too high pitch for human ears to hear.

Laser beams already emit waves at frequencies beyond the range of human hearing. The upper range of human hearing is ~22kHz (10^3 Hz == kHz). Visible light is in the hundreds of terahertz range (10^12 Hz == THz).

I doubt the frequency of laser beams would alter the frequency of the sound you hear coming from the plasma bursts. A higher frequency means more energy means more bursts, but it's very likely that there are already more bursts occurring than the ones you hear, so increasing the number of bursts won't likely change the frequency, just the amplitude (in other words, same pitch only louder).

I want to say its like the sound coming from a hive of bees. Add more bees and the frequency of the sound doesn't change (just it's amplitude). To change the frequency would mean getting every last bee to beat it's wings faster. The bee comparison only goes so far.

As for which gas to use, my initial thought was one of the noble gases (ie. helium, neon, argon, krypton, xenon). But the links ddn3 provided show that the technique works in air, so nitrogen and oxygen!