Answers Archive
| I don't particularly like broccoli but my parents make me eat it. What good is broccoli anyway? Broccoli is just about the most nutritious food we can eat. It has calcium for bones, iron to help carry oxygen to our cells and have healthy muscles, vitamin A for vision, vitamins C and folate, and just about all our other vitamins and minerals, too. Plus broccoli contains fiber for health and substances that may help us lower our risk of some cancers. And you can eat lots of it without worrying about getting too much fat or sugar! |
| Why does the wind blow? Winds blow because the Earth's atmosphere is trying to even out temperature differences from place to place. The Sun heats some parts of the Earth (such as the tropics) more strongly than other parts (such as the polar regions). Since warm air rises and cool air sinks, we therefore see rising motions in some areas and sinking motions in other areas. Rising motion results in low atmospheric pressure at the Earth's surface, while sinking motion results in high pressure. Air then flows from high pressure toward low pressure like water coming out of a hose, and we call that wind! Answer provided by: |
| Why do earthworms leave the ground after a rain? Are they drying out on the pavement and sidewalks? Seems like a good way to get squashed.: Earthworms are surface feeders that generally emerge at night to feed on leaves and other plant material. While they need to stay moist, a good rain probably fills their tunnels which is at the very least inconvenient for them. It is unlikely that they are looking for food on the pavement since they feed by ingesting soil. In fact, tons of soil passes through earthworm bodies each year, cultivating the soil while their burrowing aerates the ground. Meeting a mate on the concrete also seems unlikely. In any case, walk with care after a good northwest rain and help save a valuable organism. |
| When I pop popcorn, not all of the corn pops. Why? Popcorn pops because of the small amount of water inside the kernel. When the corn is heated water pressure builds up and eventually pops open the kernel. The kernels that don't pop are probably too dry inside or have small cracks in the kernel so that the pressure doesn't build up when heated. Popcorn is a good snack as long as you don't overdue the butter and salt. |
| When will the world come to an end?
Due to natural causes, the surface of the Earth will be devastated due to a major impact with an asteroid or comet. Such a "major impact" happens about every 100,000 years. no one knows if it will be today, or many years from now. The Earth as a planet will either end in 4.5 billion years when it will be swallowed up by an expanding Sun, or it will survive that expansion, and last forever -- the surface reaching towards absolute zero -- orbiting in eternal darkness around the dead sun. Answer provided by: |
| How do we know how many stars are in the sky? Does someone count them and how can they keep track?
People have counted the naked-eye visible stars. There are about 10,000 on any clear night. The total number of stars in the universe is estmated based on 1) the average brightness of stars, 2) the density of stars in our part of the Milky Way, 3) the overall brightness of other galaxies, and 4) the average number of galaxies that show up in sample photographs at various places in the sky. When this is all multiplied out, astronomers estimate there are 10 billion trillion stars in the observable universe. Answer provided by: |
