Lava lamp
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A lava lamp is a kind of lamp typically used more for decoration than illumination, in which the gentle flow of randomly-shaped clumps of wax suggests the flowing of lava.
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How it works
The "lamp" consists of two parts: the actual illuminating lamp, and a container (typically a glass bottle) containing a transparent liquid, some translucent wax, and a metallic wire coil. The container sits on top of the actual lamp, which heats the container and its contents.
The wax and the liquid have similar densities. However, the wax has a slightly higher density than the liquid under cool conditions, and a slightly lower density than the liquid under marginally warmer conditions. This happens because the wax and the liquid—like most substances—expand when heated, but at different rates.
The lamp heats the container at the bottom, and due to heat exchange with the atmosphere, the container eventually dissipates the introduced heat.
Wax near the bottom heats up until the wax melts and, eventually upon further heating, the density of wax becomes less than the density of the liquid above it. At this time, some portion of the wax rises towards the top of the container. Near the top, away from its heat source, the wax cools down and its density drops again, so it begins to fall through the liquid towards the bottom of the container again.
Separate masses of wax may rise at the same time as others fall. The metal coil at the bottom tends to overcome the surface tension of the individual wax droplets, causing the descending droplets to agglomerate into a single large, molten wax mass at the bottom of the container. The cycle of rising and falling wax droplets continues so long as the bottom of the container remains warm and the top of the container remains cool. Beyond certain temperature limits, the "lava" ceases to circulate, either remaining quiescent at the bottom (too cold) or all rising to the top (too hot).
Chaotic behaviour makes the movement of the wax unpredictable—hence lava lamps can aid in the generation of one-time pads for cryptographic use.
History of the lava lamp
An Englishman (some sources say Belgian), Edward Craven Walker, invented the original and best-known lava lamp in the 1960s. He named it the "Astrolight" or "Astro Lamp" and presented it at a Hamburg trade show in 1965, where the entrepreneur Adolph Wertheimer noticed it. Wertheimer and his business partner Hy Spector bought the American rights to the product and began to produce it as the "Lava Lite"® via a corporation called Haggerty Enterprises and trading under the name Lava World International (http://www.lavaworld.com/)®. The lava lamp became an icon of the 1960s. In the 1990s Edward Craven Walker sold his rights to Cressida Granger whose company Mathmos continues to make and market lava lamps and other related products.
World's largest lava lamp
In 2002, the town of Soap Lake, Washington announced preliminary plans to construct the world's largest lava lamp (60 feet in height) as a tourist attraction. Some critics, however, regard a lava lamp this large as infeasible in terms of materials needed to make it and in terms of energy consumed.
Lava lamp death
The lamp will not work until the liquid (typically rather more than a litre) is sufficiently warmed by the lamp (typically only 40w). This can take half an hour or even longer, especially if it has solidified completely since the last use; in a sufficiently cold room the lava may never start to flow. Because of this, users have been tempted to warm the lamp by other means, but this is very dangerous. On November 30, 2004, 24-year-old Phillip Quinn died in a lava lamp accident. The glass lamp bottle exploded while Mr. Quinn was heating it on top of his home stove, killing him by sending a glass shard through his heart.
See also
- Plasma lamp
- Lavarand a patent for generation of random numbers using lava lamps
External links
- Lava Buzz, Lava Lamp and Pop Culture Forum (http://www.lavabuzz.com/)—Lava Lamp collector forum with features including chat and a user contributed Lava Lamp Gallery.
- Oozing Goo, The Lava Lamp Syndicate (http://www.oozinggoo.com/)—Extensive fansite with discussion forums, history, gallery, and a How To Make Your Own section.
- GiantLavaLamp.com (http://www.giantlavalamp.com/)—Web site promoting the Soap Lake idea
- Lava Lamps (http://www.lavalamps.org/) - Provides some basic information on Lava Lamps.
- How do lava lamps work? (http://www.straightdope.com/classics/a2_359.html) (from The Straight Dope)
- How Liquid Motion Lamps Work (http://home.howstuffworks.com/lava-lamp.htm) (from howstuffworks.com)
- CNN.com - Lava lamp left on hot stovetop explodes, killing man (http://www.cnn.com/2004/US/11/30/lava.lamp.death.ap/index.html)de:Lavalampe