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Why Do Cans of Diet Coke Float While Regular Coke Sinks?

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In high school, my physics teacher took two cans of soda from a vending machine, plopped them in an aquarium filled with tap water, and blew our minds. The Diet Coke can floated to the top, while the regular Coke sat on the bottom. Why?

If you like thinking things through, perhaps pause here and noodle on this one.

The answer is a real forehead-smacker: sugar. While both beverages contain mostly water, the regular Coke has a lot of sugar (or dense corn syrup) dissolved in it—roughly 39 grams per can. This makes the density of the Coke liquid greater than that of pure water, so the regular Coke sinks. The can of Diet Coke contains less than one gram of sweetener, resulting in a density nearly equivalent to that of water (indeed, slightly less), so it floats.

If you prefer video explanations, check out this Today I Found Out video, which includes a healthy dose of bonus facts (including plenty on Archimedes and his "eureka" moment!):

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environment
Your Bacon, Egg, and Cheese Sandwiches Have a Hefty Carbon Footprint
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iStock

Most people know that eating meat, especially red meat—say, hamburgers—is bad for the environment. Raising enough methane-farting, resource-intensive cows to satisfy our cravings for burgers and steaks produces an outsized carbon footprint that plays a significant role in climate change. But what about your breakfast egg-and-cheese? A new study says you should feel guilty about that, too.

Recent findings reported in the journal Sustainable Production and Consumption examine the carbon footprint of 40 different kinds of sandwiches—from the simple ham and cheese to tuna, BLTs, and breakfast sandwiches—both homemade and pre-packaged. Researchers from the University of Manchester calculated the carbon necessary to produce standard recipes, including the agriculture required for the ingredients, the manufacturing of the packaging materials, the refrigeration required to keep the sandwiches cold, and the waste generated. They sourced their estimates from previous studies on the carbon footprint of producing and transporting ingredients like bread, ham, bacon, lettuce, tomato, and canned tuna as well as the energy cost of manufacturing packaging, transporting materials, and taking waste to the landfill.

They found that of all the sandwiches, those that combined pork (or prawns, because prawn and mayonnaise sandwiches are apparently a popular thing) and cheese are the most carbon-intensive. A bacon, egg, and cheese breakfast sandwich clocked in as the most environmentally taxing sandwich of them all, with a carbon footprint of 1441 grams CO2 equivalent—a measurement of the global warming potential—per sandwich. (The diet of the average meat-eater in the UK produces about 7200 grams CO2 equivalent daily. For comparison, if you drive your car four miles, it emits about 1650 grams CO2, roughly.)

Chicken and tuna sandwiches were slightly less carbon-intensive, but vegetarian sandwiches didn't fare as well as you might think—depending on how much and what type of cheese was involved, they could have carbon footprints as high as some of the meat sandwiches.

The researchers suggest that some improvements to the way sandwiches are produced and sold might decrease their carbon footprint by as much as 50 percent. Reducing the amount of meat, eggs, and cheese used, excluding tomato, lettuce, or mayo, reducing packaging, and other changes could all contribute to shrinking a sandwich's carbon footprint. Unfortunately, here's a limit to how much a sandwich's environmental impact can be reduced. You can't really have a BLT without the B, L, or T.

But if you're making it instead of buying it, you're saving a lot of emissions. As you might expect given the environmental cost of packaging, ready-made commercial sandwiches had a much bigger carbon footprint than their homemade counterparts containing the same ingredients—2.2 times larger, in fact.

Just another reason to feel guilty about not bringing your own lunch from home.

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Space
What Will We Eat on the Way to Mars? Poop, Of Course
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NASA/Getty Images

There are plenty of tough problems NASA has to work out before it can send astronauts on long-term manned missions to planets like Mars, but one of the biggest questions is sustenance. When we have sent robots to Mars, the trip has taken around eight months, but it required no food. If we were to send humans out into space for months at a time, they would need to either pack or grow enough food to keep them from starving for the entire duration of their mission. One answer may lie in our toilets, as The Independent reports.

In a study in the journal Life Sciences in Space Research, Penn State University astrobiologists report that with a little microbial magic, they can potentially turn wastewater into food. Using the methane produced during an anaerobic waste treatment process (a oxygen-free technique already used to treat Earthly sewage), they were able to culture three bacterial species, two of which—Methylococcus capsulatus and Thermus aquaticus—yield "protein- and lipid-rich biomass that can be directly consumed," according to the study. Yum.

In The Independent, Penn State professor Christopher House describes the resulting "microbial goo" as being kind of like Vegemite or Marmite. In theory, you could either eat it by itself—poop toast, anyone?—or use it as a high-protein supplement to feed fish, insects, or other live food sources.

Plenty of testing remains to be done before this type of microbial mixture could be made into human food at all, much less deployed on a spacecraft, where everything has to be perfectly engineered to balance astronauts' needs with space and weight considerations to stay fuel-efficient. But in Europe, the microbe is already approved to feed fish, pigs, and other farmed animals, so it wouldn’t be a stretch to think it could feed animals on a space ship. Whether astronauts will be eating it for months on end will have to be seen.

[h/t The Independent]

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