Mind a few summer questions?
There are lots of interesting science facts associated with summer, and they might answer questions your kids have posed this season. Why isn't a vacation ever long enough? Scientists might never know. But in the meantime, USA TODAY's Michelle Lefort has scoured books and websites to answer other science questions you might have been asked, or pondered yourself, this summer.
- Why is it summer in the USA and winter in Argentina?
- Earth rotates on a tilted axis that goes through the North and South poles. As Earth revolves around the sun, the tilt causes the Northern Hemisphere to get more direct rays from April through August. The tilt allows the Southern Hemisphere to bask in those direct rays from September through March, when it's cool up North.
- Why do mosquitoes bite?
- Female mosquitoes are the biters, but they don't do it for food. They actually eat plant nectar. They need protein from blood to lay their eggs. Why do mosquito bites itch? When the female mosquito bites, its saliva contains proteins to keep the blood from clotting. Our immune system tries to break down those proteins, causing the itchy, swollen red bumps we associate with the summer pest.
- How does sunblock work?
- Most sunblocks contain compounds that absorb ultraviolet light from the sun, like para amino benzoic acid (PABA). That compound releases the absorbed UV energy as heat. Why do we tan? Cells called melanocytes produce melanin. More melanin means darker skin. UV light stimulates production of melanin to protect cells from UV damage. Although continuous in some races, melanin production for Caucasians is limited. If you are in the sun too long, insufficient melanin will cause you to burn. The redness is blood racing in to repair the damage.
- What makes grass green?
- Grass contains chlorophyll, a pigment that absorbs red and blue light for photosynthesis. The wavelength of light we see as green isn't absorbed, but gets reflected so that grass looks green. (Although that doesn't answer why grass is always greener on the other side.)
- Where was the first iced tea made?
- Iced tea was developed in southern U.S. states in the 1800s. India Tea Commissioner Richard Blechynden formally introduced it to the nation at the 1904 St. Louis World's Fair. When were sunglasses developed? Sunglasses were first sold in 1929 in Atlantic City, N.J. Polarized lenses and special tints were developed in the 1930s to help military pilots reduce high-altitude glare.
- Why is watermelon so sweet?
- Watermelons are 92% water and 8% sugar. The flavor you experience is the result of the interaction between the sugars, malic acid (an organic acid) and the volatile compounds that give watermelon its aroma.
- How do fireflies light up the night?
- Fireflies produce a chemical reaction — a process scientists call bioluminescence — in cells called photocytes. Mixing oxygen, ATP (a cell's energy bar) and luciferase (an enzyme) in the cell makes the molecule luciferin give off light.
- How does AC cool air?
- Air conditioners contain coils of refrigerants, chemicals that change from a liquid to a gas. Fans take in warm air from a room and pass it over coils that absorb heat. The cooler air is then blown back into the room. The heat is released when the refrigerant condenses from a gas to a liquid and moves through an outdoor coil. Back inside, the refrigerant evaporates and again absorbs heat.
© 2008 Gale.