Everyone knows light exposes film, but other forms of radiation do as well-a fact you can use to take pictures in some pretty unusual ways.

It's also how radioactivity was first discovered. In 1896, French physicist Henri Becquerel stored some x-ray film in a drawer along with a uranium rock. He suspected that uranium might emit strange rays when exposed to sunlight, but this sample had been kept entirely in the dark, so he was surprised to find, on developing it, that the mineral had exposed the film. The discovery of natural radioactivity won him a Nobel Prize.

It's not hard to repeat Becquerel's experience at home with standard film. I took apart a 10-pack of Fujifilm ISO 3000 instant film and wrapped each piece in tinfoil. This must be done in absolute darkness because 3,000-speed film is extremely sensitive. (I sacrificed the first pack practicing in the light.)

Next I set a big, flat butterfly-shaped earring directly on top of the wrapped film. I suspended the most radioactive thing I have, a small radium puck from an old classroom set, several inches above the earring. This allowed the radiation to shine through it and onto the film, exposing it right through the foil wrapper. Then I developed the film by pulling it through the rollers of an old Polaroid camera (once again, in complete darkness).

This exposure took about 36 hours, determined by trial and lots of error. If you're willing to wait longer, less-radioactive sources work too, even common salt substitute. Yes, sodium-free salt (potassium chloride) is sufficiently radioactive (from the isotope potassium-40) that after several months, a saltshaker-ful will form an image on film. Provided you don't forget and eat the radioactive source on your breakfast.

Achtung! Stronger radiation sources such as radium watch hands, and any source that's flaking off fine particles, should be handled with care to minimize exposure and avoid contamination.

Photo credit: Mike Walker

Popular Science is your wormhole to the future. Reporting on what's new and what's next in science and technology, we deliver the future now.

Using leverage, this simple device will radically increase your throwing power. Finally, you can deliver messages to your neighbors via notes stuck into their doors with a spear thrown from across the street. That way they'll know you aren't fucking around. [Make via Lifehacker]

The picture above is a crashed UFO prop, complete with chasing LED lights.

Or there are the "ghost sliders," where you attach a set of casters to kneepads in order to drift across pavement like a ghost. This is dangerous. Don't blame me when you end up eating asphalt instead of candy and get your jaw wired shut.

There are hundreds of projects at the link. Check it out if you need something to keep you occupied this weekend. [Make]

Verna Rockets has a full debrief on its own builds, complete with links to several sites with parts and instructions. You'll find everything you need to build a flying model rocket that looks like a Recon Viper, the U.S.S. Enterprise, even The Black Hole Space Probe from "The Black Hole"

Confession: I always get psyched by rocket kits. Have any pics of your own launches that you'd like to share? [Verna Rockets via Hobby Media]

Over at Instructables, there's a step by step on boring a cigar, treating its surface, and then loading it with a fiery LED along with a USB stick. The result is a classy cigar USB dongle that can possibly lead to computer mouth/throat cancer. But don't feel bad for your laptop, it'll turn obsolete well before its needlessly induced nicotine addiction claims its life. So you'll thoughtlessly drop your computer in a retirement home (a landfill disguised as a recycling center) from where it will spend the rest of its days doing its damnedest to poison you back. [Instructables via Geeky Gadgets]

Here's stuff from the NYT article that we already knew:

Secrecy at Apple is not just the prevailing communications strategy; it is baked into the corporate culture. Employees working on top-secret projects must pass through a maze of security doors, swiping their badges again and again and finally entering a numeric code to reach their offices, according to one former employee who worked in such areas. Work spaces are typically monitored by security cameras, this employee said.

This stuff is common in normal companies even, and a good majority of tech employees have badges as a permanent fashion staple. But this, this is interesting:

Some Apple workers in the most critical product-testing rooms must cover up devices with black cloaks when they are working on them, and turn on a red warning light when devices are unmasked so that everyone knows to be extra-careful, he said.

That seems a bit over the top to me, but hey, you know what? It seems to be working for them. Waitaminute.[NY Times]

This doesn't look like the easiest project we've seen; it calls for laser cutting and a significant amount of audio tech know-how. But the results are pretty much exactly what you'd want, and it's definitely a sweet-looking end result. This thing even features audio-in so you can plug in instruments, pre-recorded sounds, or anything else you want, and the pitch-shifting and vibrato buttons let you adjust the robot sounds on the fly. Check out the instructions for more info on how to sound like a robot. [Instructables via MAKE]

Car modder Perry Watkins took the frame of the "Postman Pat" children's ride and mounted it on a quad mini-bike, using its 150cc engine. The car features a windshield wiper, lights and signals, mirrors, and even a Pimp My Ride-worthy paint job and fake racing exhaust pipes. The car, christened "The Wind-Up," can hit 40 miles per hour in what we're sure is an incredibly uncomfortable and scary ride. We question the wisdom of granting this thing a street-legal license, but for a nation of people that exclusively drives on the wrong side of the road, we guess anything goes. [The Sun via DVICE, image via The Sun]

A DIY project consisting of an MP3 decoder, lithium ion battery, accelerometer (for complete gyration response) and some other various circuits and switches, the only components it might be missing are speakers and a decent gold plated mini horseshoe (a series of mistakes you can unmake during your own construction process). Now just to find a decent pair of blinky LED boots to ensure complete cowboy ostracism. [sparkfun via technabob]

Once again, the week before Labor day brings offbeat art lovers from around the world to Black Rock City, Nevada, for a seven-day event that immerses the senses in radical artistic self-expression. Actually, its pretty hard to describe Burning Man unless you have actually been to one, but it is certainly a far cry from the stuffy art museum atmosphere most of us are familiar with. Plus, there are enough flaming gadgets to keep any nerd entertained. Hit the jump to see some of the unique projects on display this year.

Other projects to look out for:

• I Heart Lamp by Blue Lake Iron Works by Joel 'Fatboy' Brown, Mark 'F St' Whitman, Spike Foster, Tisha 'Mortisha' Sloan: "I Heart Lamp is a super-size sculpture of grandma's living room floor lamp. More than 30 feet tall, the lamp sits on the playa as a reminder of the cushy living rooms that are the American Dream for the mainstream, but with a twist to fit other dreams. Made from a scavenged Douglas Fir pole and recycled box pipe and lumber, this lamp, besides being surrealistically large, does not contain an electric light bulb. This lamp is lit by a propane fire cannon that turns on the same way the light would… when someone pulls the chain hanging from under the lampshade almost 20 feet in the air." (It may also be an homage to the movie Anchorman. I hated the movie, but anything Steve Carell says is OK in my book.)

• PlaySoundGround by Sasha Leitman and Michael St. Clair: "PlaySoundGround is an adult-sized playground that is also a musical instrument. It consists of three large pieces: a merry-go-round, a slide, and a teeter-totter. These pieces are equipped with sensors that convert the motion of play into music. The installation provides an arena for chaotic improvisations, synesthetic experiences and pointless fun."

• SOL by Alex Nolan and Justin Grant: "SOL is a groundbreaking piece of kinetic art, pushing the limits of sound, vision and motion in art. The sculpture is a nearly 25' tall robot, sensing the location and motion of nearby observers to track them with a highly directional sound system. The work is powered by an array of solar panels, drawing energy the sun to fuel its sensory output."

• Tetrion by Jim Abrams: "The Tetrion is a tremendous representation of the pieces from the original Tetris game."

[Burning Man Image of 2008 Burning Man designed by Rod Garrett and Larry Harvey]

There's an LED sign that displays a message in 20 languages: That message is simply "Dance to Start the Party". And the more intense the party gets, the greater the effects, eventually culminating in a light show with disco ball, lasers, siren, ground effects and fog, creating an infinite loop of more fog, more techno, more siren, and therefore more dancing, and then the radar picks it up and then you've got more disco, and then more fog, and then more techno, and then more dance I'm so tired I can't stop partying my legs won't stop feeling the beat. After everyone collapses, the box returns to its docile flight case status.

International Dance Party! The full length video of this crazy and funny party machine! from Niklas Roy on Vimeo.

[IDP via Make, I love Jonah for sending this to me.]

Panel .95" DMD 1 panel
Resolution 1920x1080
Light source 300W LAMP
LAMP Lifetime 2000 Hours
Brightness 1000 ANSI Im
Contrast Ratio 10,000:1
Color wheel6 Segment
Zoom/Focus Manual/manual
Input Terminal 2 x HDMI, Analog PC, 2 x Component, S-Video, Video, RS-232C
Lens shift O
Audible noise 25 dB
Power consumption 380W
Dimensions (HxWxD) 432x212x479 mm
Special features Dynamic Black 1080@24p Support
Chipset Scaler: STP10, DMD Controller: DDP3021

See it in glorious video after the jump.

Project Page [design on Deadline via Makezine]

Instructables' guide to building your own Tetris shelves costs you only about $85 in wood ($200+ if you buy good wood), plus some more in parts. You'll need equipment like table saws and wood glue, so if you don't have that you might have to find a buddy who does. Just be careful not to line them up horizontally or else you're going to have to start all over. – Jason Chen

Project Page [Instructables]