Neon and fluorescent lights differ in several ways, including bulb shape, color of light emitted and substances used to produce that light. Find out how neon and fluorescent lights work in this podcast from HowStuffWorks.com.

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A dollar bill changer doesn't just have to sense a bill's denomination -- it also needs to be able to tell whether bills are fake. Join Marshall Brain as he breaks down the science behind bill changers in this podcast from HowStuffWorks.com.

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Carrageenan is a gum derived from seaweed that helps processed food withstand the rigors of transportation and long waits in warehouses. Learn more about the role that carrageenan plays in food by checking out this podcast from HowStuffWorks.com.

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In a group of 20, there's a 50/50 chance that two people will have the same birthday; this is called the birthday paradox. Find out how it works in this podcast from HowStuffWorks.com.

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Sharks are ancient, fierce creatures, but they're also in danger of extinction on many fronts. Discover all the factors that make sharks vulnerable -- and what you can do to help -- in this podcast from HowStuffWorks.com.

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A family of four can consume more than 300 gallons of water per day. Old toilets use 5 gallons per flush, and this water use quickly adds up. Check out this HowStuffWorks podcast and learn why cities across the US are replacing their old commodes.

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When it comes to energy usage, heating and cooling appliances contribute the most to your power bill. Tune in to find out which appliances are the most power-hungry -- and why -- in this podcast from HowStuffWorks.com.

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Human muscles are essentially biological engines. In terms of efficiency, biological engines are amazing. Listen in as Marshall Brain calculates human efficiency in this episode.

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What exactly is high-level nuclear waste, and how are we dealing with it today? In this episode, Marshall breaks down the techniques used to store high-level nuclear waste.

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Fusion reactors like the sun produce huge amounts of energy, so why aren't there fusion power plants everywhere? In this episode, Marshall explains the chemistry of fusion reactions and discusses how close fusion is to becoming a viable energy source.

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