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Answering your hypothetical questions with physics, every Tuesday.

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Hot Banana

I heard that bananas are radioactive. If they are radioactive, then they radiate energy. How many bananas would you need to power a house? Kang JI Bananas are radioactive. But don't worry, it's fine. Bananas are radioactive because they contain potassium, some of which is the radioactive isotope potassium-40. The factoid about banana radioactivity...

Earth-Moon Fire Pole

Earth-Moon Fire Pole My son (5y) asked me today: If there were a kind of a fireman's pole from the Moon down to the Earth, how long would it take to slide all the way from the Moon to the Earth? Ramon Schönborn, Germany First, let's get a few things out of the way: In real life, we can't put a metal pole between the Earth and the Moon.[1]For one,...

Electrofishing for Whales

Electrofishing for Whales I used to work on a fisheries crew where we would use an electro-fisher backpack to momentarily stun small fish (30 - 100 mm length) so we could scoop them up with nets to identify and measure them. The larger fish tended to be stunned for slightly longer because of their larger surface area but I don't imagine this relationship...

Toaster vs. Freezer

Toaster vs. Freezer Would a toaster still work in a freezer? —My Brother, My Brother and Me, Episode 343, discussing a Yahoo Answers question On a recent episode of Justin, Travis, and Griffin McElroy's terrific advice podcast, My Brother, My Brother and Me, the brothers pondered a Yahoo Answers question about what would happen if you put a toaster...

Coast-to-Coast Coasting

Coast-to-Coast Coasting What if the entire continental US was on a decreasing slope from West to East. How steep would the slope have to be to sustain the momentum needed to ride a bicycle the entire distance without pedaling? —Brandon Rooks Too steep to actually build, sadly. But for the next best thing, I suggest a vacation to the Hawaiian island...

Hide the Atmosphere

Hide the Atmosphere Earth’s atmosphere is really thin compared to the radius of the Earth. How big a hole do I need to dig before people suffocate? —Sam Burke The idea here is straightforward: When you dig a hole in the ground, the hole fills up with air.[1]The dirt you pile up outside the hole displaces air, so at first you won't have much effect...

Flood Death Valley

Flood Death Valley Since Death Valley is below sea level could we dig a hole to the ocean and fill it up with water? —Nick Traeden Yes! We can do anything we want. We shouldn't do this, though, because it would be gross. Death Valley is an endorheic basin[1]"Big hole" in California. The floor of the valley is about 80 meters below sea level. It...

Sun Bug

Sun Bug How many fireflies would it take to match the brightness of the Sun? Luke Doty Not that many! I mean, it's definitely one of those gigantic numbers with lots of zeroes, but in the grand scheme of things, there aren't as many zeroes as you might expect. Our first question: Where does firefly light even come from? Fireflies may look like...

Tatooine Rainbow

Since rainbows are caused by the refraction of the sunlight by tiny droplets of rainwater, what would rainbow look like on Earth if we had two suns like Tatooine? —Raga A planet with double suns would have double rainbows. Or rather, quadruple rainbows. Our rainbows here on Earth are already double rainbows—there's a second, fainter bow above the main...

Eat the Sun

Eat the Sun What percentage of the Sun's heat (per day) does the population of Earth eat in calories per year? What changes could be made to our diets for the amount of calories to equal the energy of the Sun? —James Mitchell 0.000000000065%. A McDonald's Big Mac contains 540 (dietary) calories of energy, or about 2,250,000 joules. The Sun's output...

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