Physics of light anyone?

Postby stargeezer » Sat Nov 03, 2007 10:12 am

To achieve the goals of the original requester, it has become obvious to many that an object must be suspended to either prevent the light from continuing skyward, or project the light downward. This requirement was very specific and leads to approaches that are definately not optimal depending on the weather conditions. It is a shame that one must be so negative rather than offering some constructive or alternative ideas. My only conclusion is this individual must have a very dark view of life.
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Postby oneeyeddick » Sat Nov 03, 2007 12:17 pm

Some people must smash thier thumbs in order to fugure out that they shouldn't be using a hammer. Some people would rather smash thier thumbs than listen to someone else tell them that they must use a pilot hole and a screw.

And BTW,SG , this smile never leaves my face.
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Postby stargeezer » Sat Nov 03, 2007 3:41 pm

oneeyeddick wrote:Too much wind. Air is too thin and warm for helium to have its properties exploited properly.
Nope... That'll never work....nope,nope,nope !!


Since helium will not work in BRC, and the wind is too serious to consider suspending anything, would you please explain the following picture.

Image

Aliens, it must be aliens.

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Postby Finnegan » Sat Nov 03, 2007 7:09 pm

Is it possible to pipe nice hot air up to whatever you want to have hanging over the city? If it's tethered, then the only weight to support is whatever light source you want shining back down.
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Postby GREENPENIS » Sat Nov 03, 2007 7:12 pm

I didn't know you knew Scotty !!


Please denote that in the pic you found that the final 100 or so
feet of Guy/electrical wire requires additional helium balloons
to support its weight. The main balloon itself can only handle
about 70' or so. And congradulations !!! I think you found a pic
of BIG PUFFY YELLOW ( and if it's not, it is still the same physics at work )

Image


Personally, I would think that to get and upside-down triangle effect with
minumim weight , a 12 volt spotlight attached to the reversed "disco ball"
mirror that can be found inside a $20 strobelight. That way a thinner wire
could be used, thus reducing the weight of the support wire and costing
far less than lasers. Maybe just a headlight pointing downward ?
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Postby mdmf007 » Sat Nov 03, 2007 8:10 pm

Finnegan wrote:Is it possible to pipe nice hot air up to whatever you want to have hanging over the city? If it's tethered, then the only weight to support is whatever light source you want shining back down.


doesnt sound practical - hot air balloons can boil water on top of the envelope.

helium is cheap, balloons are readily available, and lights can be small if you want them aloft.

I was just sketching some plans in my head and think that if you can focus your beam of light to a focal point 2/3or 3/4ths the way to the apex of your pyramid woudl work well.

as each beam of light would be diverging already at the 2/3-3/4 point -before it reached the apex the beams would cross and continue diverging your pyramid would be defined, and beyond that it would be scattered light. as most dust is under the 200 foot level I am thinking it would be a great effect as dust shows beams well, and the diverging light would show as a glow without any real definition above that.

This would require some focused lenses like fixed spotlights, or the good spotlights we use on the tugboats that are focusable or rental quality spotlights if you want to go big.

good luck - sounds like fun.
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Postby Dork » Sat Nov 03, 2007 8:57 pm

Another alternative is building a 200' tower or pyramid with the light in the top. It will require some serious engineering and will be more visible than guy wires leading to a balloon, but will allow you more precise aiming.
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Postby stargeezer » Sat Nov 03, 2007 9:27 pm

With a tower, I think guy wires would be required for any tower due to limitations of foundation construction on the playa. If a solid structure is to be considered, a telescoping amateur radio antenna tower may fit the need. I am not sure if 200' would be possible with a tower, this would require some investigation.

I would still prefer a balloon approach to a tower due to safety concerns. If a big wind were to cause problems, the balloon and light would not cause that much damage on impact. That tall of a tower would contain a lot of mass, and thus really make me nervous.
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Postby stargeezer » Sat Nov 03, 2007 9:56 pm

GREENPENIS wrote:I didn't know you knew Scotty !!


Please denote that in the pic you found that the final 100 or so
feet of Guy/electrical wire requires additional helium balloons
to support its weight. The main balloon itself can only handle
about 70' or so. And congradulations !!! I think you found a pic
of BIG PUFFY YELLOW ( and if it's not, it is still the same physics at work )

Image


Personally, I would think that to get and upside-down triangle effect with
minumim weight , a 12 volt spotlight attached to the reversed "disco ball"
mirror that can be found inside a $20 strobelight. That way a thinner wire
could be used, thus reducing the weight of the support wire and costing
far less than lasers. Maybe just a headlight pointing downward ?


Since you already created a nice suspension system, I was wondering if you could provide a little information about it. What was the size of the balloon, and how much weight were you lifting? I am just curious, in my calculations, I think I was very conservative, but would like some good numbers to verify this. I am guessing from your picture that the balloon was about 6 feet in diameter, but I can't tell if it was fully inflated, and have no idea what the payload was. The lift of a balloon goes up by the cube of the diameter, so doubling the diameter of the balloon provides eight times the lift. Any information you can provide would be greatly appreciated.
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Postby GREENPENIS » Sun Nov 04, 2007 8:44 am

I didn't create this, but Big Puffy Yellow was straight across the street from me in 2001. I believe the guy wire they used was actually the air hose connected to the balloon.
Oneeyeddick may seem negative in his approach, but he inadvertantly has brought up some issues about working with helium. I had a 7' penis balloon that floated fine here(SEATTLE), but upon filling it at BRC, it wouldn't do its thing. Altitude and temperature greatly the properties of helium, not to mention the kenetic energy of wind .

Here is a link explaining the math of it.
http://science.howstuffworks.com/helium2.htm

Also, I personally know oneeyeddick, and he is just being a smartass.
Don't let him get under your skin too deep. :wink:
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Postby Dustdevil » Sun Nov 04, 2007 10:04 am

The balloons with the strings of lights hanging from them were done by Buckethead Alien. He hasn't posted here for a few months. He didn't bring them in 07' Not certain why. He used weather balloons and could achieve 300'. As I remember some of his balloons had airfoils. The more wind, the greater the lift. I supplied the helium for him on the Playa. It would take one tank ( or close to it) per balloon. We have used hydrogen on the Playa for our balloons and it worked very well. The danger is in the fact that there is very little humidity. This only presents a problem when filling. We used the balloon for another purpose and it worked very well.
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Postby stargeezer » Sun Nov 04, 2007 11:16 am

GREENPENIS wrote: I had a 7' penis balloon that floated fine here(SEATTLE), but upon filling it at BRC, it wouldn't do its thing. Altitude and temperature greatly the properties of helium, not to mention the kenetic energy of wind .

Also, I personally know oneeyeddick, and he is just being a smartass.
Don't let him get under your skin too deep.


The properties of helium do not change, it is the environment that changes and must be accounted for. The air density is the key, as it decreases with altitude. This can be countered by using a larger balloon, and/or letting the air temperature cool which increases its density.

One other issue is that you must allow room in your balloon for the helium to expand. As the balloon rises, it encounters lower air density. If the balloon is such that the helum can expand, it will continue to provide lift. If instead, the balloon loses helium as it rises, it will soon be returning to the ground.

What you are encountering is the same difference that is seen between fresh water and salt water. Consider high altitude to act like fresh water and sea level to act as salt water. Objects are more bouyant in salt water than fresh water, but that does not mean that an ocean going vessel will sink as soon as it enters fresh water.

I just hope that the negative comments do not discourage the original poster from creating his project. Other than that, the negative comments have no impact on me personally.

On a more humorous note:

I would encourage you to make a slightly larger balloon. While it will require more helium, it would work fantastic in Seattle, and would fly in BRC. Since you would be building and testing it near sea level, make sure it will fly when only half filled for the test, this will insure that when completely filled at BRC it would have plenty of lift, and it goes without saying that a balloon of this shape should have plenty of lift!!! I am just thinking that it would look really neat and would attract a lot of attention if it was tethered 50' to 100' above the B(o)(o)by Bar!! :lol:
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Postby mdmf007 » Sun Nov 04, 2007 2:34 pm

http://images.burningman.com/index.cgi?image=22279
This is the 108' ladder at BM a few years back. it went up pretty quick.
and was rated for a human to climb as well.

A rig to hold 20 pounds of lights would be easy to design and erect. The guy lines would have to be well marked. Rule of thumb in radio tower construction 1:1 for guy wire slope. 200 foot tower - guys are 200 feet from base.

Thats a lot of guy wire to mark.
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Postby BitterDan » Sun Nov 04, 2007 3:17 pm

Huh huh, you said Guy Wire and Erect in the same post.
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Postby Ugly Dougly » Mon Nov 05, 2007 11:13 am

GREENPENIS wrote:Personally, I would think that to get and upside-down triangle effect with
minumim weight , a 12 volt spotlight attached to the reversed "disco ball"
mirror that can be found inside a $20 strobelight.

A giant disco ball? you are a sick man, Greenpenis.
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Postby hippie_nz » Wed Nov 07, 2007 1:43 am

As much as I'd loved to play with hellium I think I'll stick with playing with mirrors and do the best I can, even if the beam of light doesn't appaer the way I wish it to it will look pretty much the same anyway.

If I was going to use hellium I think all the information I needed is in here!
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Postby Gravity Mike » Thu Nov 08, 2007 11:03 am

The Fresnel lens is a great idea. And it doesn't have to be expensive - those plastic lenses glued in the back window of RVs to increase the field of view are Fresnel lenses! Just aim your light through in the opposite direction (from outside the RV to inside - to convert divergent light to near parallel). Also, places light Edmond Scientific sells them for classroom experiments.

You can also use a bunch of white light LEDs - and if you want it bright, it'll really be a BUNCH! You can get them with a variety of divergences. Most people want ones that shine out radially in all directions to mimic a regular light bulb, but for this project you'd want the collimnar ones without the fancy lens. The 'default' for LEDs is to have a narrow window of light, and they have to add lenses to disperse the light in other directions.

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Postby Ugly Dougly » Thu Nov 08, 2007 11:51 am

Laser Light does not normally form a visible "beam" unless there is some particulate matter in the air before it, such as mist or smoke. That's not naturally abundant in the air above the playe; you'd have to furnish that.

http://www.laserdreams.com/

You could form a cone with a single laser mounted vertically.

It would shine into a mirror M1 which would be mounted on a gimbal to rotate very quickly, the axis of which would be identical to that of the laser beam and vertical.

This would pivot inside the center of a disk about 3 feet dia. About the periphery of the disk, you'd have a series of mirrors M^n which would be tilted so they reflect the light to a single point several feet above the disk.

As M1 spins on its gimbal, the laser light is distributed to the M^n.

You must make a beam block all around the periphery of the disk to keep stray scatter from blinding your friends.

The disk could be made to spin as well, though not as fast as M1. In fact, by varying the speed and direction of spin, you could put on a little show.

First get a big generator.
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Postby Rat Bastard » Mon Dec 17, 2007 8:26 am

No matter what you do light isn't visible unless it hits something. If there's nothing in it's way, you won't see it. "Stuff" in the air will light up (dust, humidity, smog etc.) but also difuse the light softening the beam as it's distance grows. With this in mind, if a beam is shot from the ground, it will always look like it's coming from the ground because the intensity will be higher at ground level. If it's shot from the air it will gradually lose intensity as it get's closer to the ground.

So, what to do? How about playing off of people's imaginations. Use lighting in a way that you can't see the lights but your project gets lit like it would look if lit from above. Hiding lights behind things or even using translucent materials to give it that glow. Make your shadows with paint. But short of spending the kind of money it would take for a super lightweight, high output light to shine as high as you want, think of a more creative way to make it appear like you wish. 100watts of lightbulb will get dim after the first 1/2 hour on a deep cycle marine battery. After that it will continue to get dimmer and dimmer.

Whatever you work out, PLEASE make sure it's well marked at night even if the lights go out. I drive an MV out there and I don't want to run your art over. Unless you want me to. We could make it an event.
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Postby Lifeisshort » Tue Dec 25, 2007 3:22 pm

oneeyeddick, why don't you offer this guy some constructive advice. You seem to be fairly quick to tell us what won't work. Stop with the negative my friend and help us solve this guy problem.
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Postby oneeyeddick » Tue Dec 25, 2007 6:12 pm

This threads done, go home and enjoy Christmas.

And besides. It'll never work. Nope,nope,nope...never. :cry:
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Postby theCryptofishist » Tue Dec 25, 2007 7:13 pm

No, I am going to stay here and be happy. Because everything happens for the best in this best of all possible worlds.
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Postby oneeyeddick » Tue Dec 25, 2007 10:03 pm

OK, fine.
If you want the light to stay on target and have maximum output
with minumum weight and power usage, attach a Quantam Flangdoodle
approximately 4 feet from the power source
I hope this helps.
Good luck.
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Postby unjonharley » Wed Dec 26, 2007 1:56 pm

search, MegaBlimp.. Heartland America a radio controled air ship $49.95.. 4 1/2 feet X 36in. dia
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Postby oneeyeddick » Wed Dec 26, 2007 2:13 pm

hippie_nz wrote:As much as I'd loved to play with hellium I think I'll stick with playing with mirrors and do the best I can, even if the beam of light doesn't appaer the way I wish it to it will look pretty much the same anyway.

If I was going to use hellium I think all the information I needed is in here!
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Postby Psyteknology » Wed Jan 23, 2008 9:56 am

What about trying this on a smaller scale, and then scaling it up for the playa ? With a project like this it seems alil more feasable to scale down the project.


[quote="hippie_nz"]The base of the cone of light will only be about 1-2 ft with the tip being as far as 300-500 ft up, I'm basically trying to create the effect of light shining down from the "heavens above" so that it appears somewhat that the light is being shined from the sky downwards rather then the ground upwards. With the spot lights I've tried so far the light always opens outwards rather then pointing inwards to a point.

I don't have bugger all money for lasers and I want the light to be white anyway, so I was thinking bright lights shined into a concave mirror (most likely very bright LED lights as I will be running it off a battery), but I don't know what curvature I would need it to be and how big it would need to be to create the desired effect.

Hiring a spot light isn't really an option because the light is going to be built into an art project.[/quote]
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Postby phoenix from the playa » Thu Jan 24, 2008 6:16 pm

Teo del Fuego wrote:
theCryptofishist wrote:schrodinger's cat as well.


"Whenever I think of Shroedinger's Cat, I reach for my revolver."--Stephen Hawkin


Whenever I think of Stephen Hawkin I reach for Shroedinger's Cat.

And what the fuck is Stephen Hawkin doing anyplace close to a friggin revolver, not to mention, *trying* to "reach" it. I'd love to see that on YouTube.

And, would Hawkins, presuming he could hold the cat and the gun in the same position for a second, kill Shroedinger's Cat? Isn't it already dead? What are the physics of being dead twice? Are you therefore alive twice? Typical Hawkin. Brilliant! He may be back on the playa this year ya know! Hopefully, without his revolver and with those gorgeous attendants.
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Postby oneeyeddick » Thu Jan 24, 2008 6:26 pm

Hold on a second.....let me check my equations......double checking the measurements......ahh, I've come to a conclusion.

Nope... that'll never work.... nope, nope, nope.
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Postby Ugly Dougly » Fri Jan 25, 2008 11:47 am

Rat Bastard wrote:No matter what you do light isn't visible unless it hits something. If there's nothing in it's way, you won't see it.


Nothing wrong with it being invisible most of the time. Just point a searchlight straight up and when some burn upwind congeals the air, the beam will be visible... then fade into the night. Maybe it wil encourage others to participate by putting "stuff" into the beam. Imagination does not feed on limitations.

what do you call those inflatable tube people that you see occasionally on the playa? They are some sort of fabric tubes with a blower at the bottom. Sometimes they have arms that flap in the breeze.
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Postby bigbluedoggy » Fri Jan 25, 2008 1:50 pm

Actually the whole enigma of Schroedinger's Cat is that you don't know if it is dead or not because it is in the box and cannot be seen or detected. In reality, one might expect some clawing and yowling, thereby making the use of the revolver far more tempting.....
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