10 Science Questions You Should Really Know How to Answer

"I see skies of blue and clouds of white," Louis Armstrong crooned in his 1968 song "What a Wonderful World." And he probably did, given that his song is an ode to optimism. European researchers have discovered that light from the blue part of the spectrum influences the emotions in a positive way, making us more responsive to emotional stimuli and more adaptable to emotional challenges [source: Opfocus].

But we digress. The reason the sky appears blue is because of an effect called scattering. Sunlight has to pass through Earth's atmosphere, which is filled with gases and particles that act like the bumpers on a pinball machine, bouncing sunlight all over the place. But if you've ever held a prism in your hands, you know that sunlight actually is made up of a bunch of different colors, all of which have different wavelengths. Blue light has a relatively short wavelength, so it gets through the filter more easily than colors with longer wavelengths, and as a result are scattered more widely as they pass through the atmosphere. That's why the sky looks blue during the parts of the day when the sun appears to be high in the sky (though it's actually the spot on the planet where you are standing that is moving, relative to the sun).

At sunrise and sunset, though, the sun's rays have to travel a longer distance to reach your position. That cancels out blue light's wavelength advantage and allows us to see the other colors better, which is why sunsets often appear red, orange or yellow [sources: NASA, ScienceDaily].

Earth's age is something that people have been arguing about, at times bitterly, for a long, long time. Back in 1654, a scholar named John Lightfoot, whose calculations were based upon the Bible's Book of Genesis, proclaimed that Earth had been created at precisely 9 a.m. Mesopotamian time, on Oct. 26, 4004 B.C.E. In the late 1700s, a scientist named the Comte de Buffon heated up a small replica of the planet that he had created and measured the rate at which it cooled, and based upon that data, estimated that Earth was about 75,000 years old. In the 19th century, the physicist Lord Kelvin used different equations to set Earth's age at 20 to 40 million years [source: Badash].

But all that was trumped in the late 1800s and early 1900s by the discovery of radioactivity, which was soon followed by calculation of the rates at which various radioactive substances decay [source: Badash]. Earth scientists have used that knowledge to determine the age of Earth's rocks, as well as samples from meteorites and rocks brought back from the moon by astronauts. For example, they've looked at the state of decay of lead isotopes from rocks, and then compared that to a scale based on calculations of how lead isotopes would change over time. From that, they've been able to determine that Earth formed approximately 4.54 billion years ago with an uncertainty of less than 1 percent [source: U.S. Geological Survey].

Like the age of Earth, the theory of evolution -- first developed by biologist Charles Darwin in the mid-1800s -- is another subject that people tend to get worked up about. If you've ever seen the classic movie "Inherit the Wind," you probably already know about the infamous Scopes Monkey Trial of 1925. Famous attorney Clarence Darrow argued unsuccessfully upon behalf of a high school biology teacher named John Scopes, who was accused of violating a Tennessee statute that banned anyone from teaching that humans were descended from "a lower order of animals," and decreed that the biblical story of creation was the only acceptable explanation [source: Linder]. In recent years, it's been anti-evolutionists who've fought in court and in legislatures to require that children learn "creation science" in school, in addition to evolutionary theory [source: Raffaele].

And if there's an idea that particularly bugs anti-evolutionists, it's Darwin's central concept, which is called natural selection. It's really not a difficult idea to understand. In nature, mutations -- that is, a permanent change in the genetic blueprint of organisms, which can cause them to develop different characteristics from their ancestors -- occur randomly. But evolution, the longer-term process by which animals and plants change over multiple generations, is not up to chance. Instead, changes in organisms tend to become more common over time if the change helps the organism to better survive and reproduce.

For example, imagine that some beetles are green, but then, a mutation causes some beetles to be brown, instead. The brown beetles blend into their surroundings better than the green beetles, so not as many of them are eaten by birds. Instead, more of them will survive and reproduce, and may pass along the genetic change that will make their offspring brown. Over time, the beetle population will gradually shift to being brown in color. That, of course, is the simple version. In practice, natural selection is based upon averages, not specific individuals, and it's not quite as smooth and orderly of a process [source: UC Berkeley].

This question reminds us of another pop song, Skeeter Davis's 1962 single "The End of the World," in which the singer wonders why the sun keeps on shining after her boyfriend apparently has dumped her. The conceit of the lyrics is that the reality around us -- whether it's the shining sun or the birds singing in the trees -- is more durable than our fragile little feelings. In truth, though, our lovelorn lass had the misfortune to be born too soon -- by about 5.5 billion years, give or take a few. That's the point at which the sun, which like any other star is a gigantic fusion reactor, will run out of the hydrogen in its core that it burns as fuel to create sunshine and will start burning the hydrogen in its surrounding layers.

That'll be the start of the sun's death spiral, in which its core will shrink and its outer layers will expand massively, turning it into a red giant. In a final burst, the sun will roast the solar system with a blast of heat that will temporarily turn even the usually frigid vicinity of Pluto and the Kuiper Belt (out past Neptune) into a celestial sauna. It's likely that the inner planets, including Earth, will be either sucked into the dying giant, or else turned into cinders [source: Overbye].

On the plus side, unless humans manage to colonize the solar systems of other stars, nobody is going to be around to experience this final inferno. The sun, which is about halfway through its expected lifespan, is already gradually heating up, and a billion years from now, it's expected to be about 10 percent brighter than it is now. That increase in solar radiation will be enough to boil away our planet's oceans, leaving us without the water that our species depends upon for survival [source: Overbye].

"[Bleeping] magnets: How do they work?" That's the question that rappers Insane Clown Posse posed in their single "Miracles" a few years back, which led those snarkmeisters at "Saturday Night Live" to ridicule them unmercifully. And that was unfortunate, because it's a perfectly reasonable thing to ponder. A magnet is any object or material that has a magnetic field -- that is, a bunch of electrons flowing all around it in the same direction. Now, electrons -- like rappers from Detroit who wear clown masks, curse a lot, and drink Faygo Cola -- like to hook up in pairs, and iron has a lot of unpaired electrons that are all eager to get in on the action. So, objects that are solid iron or have a lot of iron in them -- nails, for example -- are going to be pulled toward a sufficiently powerful magnet. The substances and objects attracted to magnets are called ferromagnetic substances [source: University of Illinois].

Humans have known about the phenomenon of magnetism for a long, long time. There are naturally occurring magnets, such as lodestone, but medieval travelers figured out how to rub steel compass needles against those stones so that they picked up electrons and became magnetized, which means that they developed their own magnetic fields. Those magnets weren't particularly durable, but in the 20th century, researchers developed new materials and charging devices that enabled them to make more powerful permanent magnets [source: Stupak]. You can actually create a type of magnet, called an electromagnet, from a piece of iron by wrapping an electrical wire around it and then connecting the ends to the poles of one of those big batteries with the clips on top [source: University of Illinois].

There's something about this atmospheric phenomenon that has inspired awe in people since ancient times. In the Book of Genesis, God put a rainbow in the sky after the Great Flood and told Noah it was a sign of "a token of the covenant between me and Earth" [source: Biblos]. The ancient Greeks went further, and decided that the rainbow actually was a goddess, whom they named Iris. But they made her an ominous figure -- the bearer of the Olympian gods' tidings about war and retribution [source: Lee and Fraser, pg viii]. And over the centuries, great minds ranging from Aristotle to Rene Descartes sought to figure out what process created rainbows' striking array of colors [source: Broughton and Carriero].

Since then, though, scientists have nailed it pretty well. Basically, rainbows are caused by the droplets of water that remain suspended in the atmosphere after a rainstorm. The droplets have a different density than the surrounding air, so as sunlight hits them, the droplets act as tiny prisms, bending the light to break it up into its component wavelengths, and then reflecting them back at us. That in turns creates the arc with bands of colors of the visible spectrum that we see. Because the droplets have to reflect the light at us, in order to see a rainbow, we have to be standing with our backs to the sun. We also need to be looking up from the ground at an angle of approximately 40 degrees, which is the rainbow's angle of deviation -- i.e., the angle at which it bends sunlight. Interestingly, if you're in an airplane and you see a rainbow from above, it actually may look like a disk, rather than an arc [source: Physics Classroom].

When someone refers to the "theory of relativity," what they really mean are two theories, special relativity and general relativity, which were devised by theoretical physicist Albert Einstein in the early 1900s [source: nobelprize.org]. But no matter what you call Einstein's body of work, it's undoubtedly baffling to most nonscientists. Einstein thought of a clever way to explain it: "When a man sits with a pretty girl for an hour, it seems like a minute. But let him sit on a hot stove for a minute and it's longer than any hour. That's relativity." [source: Mirsky].

And that actually sums it up pretty well, though the details are a bit more complex. Before Einstein, everybody pretty much believed that space and time were fixed qualities, which didn't ever change, because that's the way they look to us from our vantage point on Earth. But Einstein used mathematics to show that absolute view of things was an illusion. Instead, he explained, space and time both can undergo alterations -- space can contract, expand or curve, and the rate at which time passes can shift, as well, if an object is subjected to a strong gravitational field or is moving very quickly.

Moreover, how space and time appear can depend upon the vantage point of a person observing them. Imagine, for example, that you are looking at an old-fashioned ticking alarm clock with hands to tell the time. Now, imagine putting that clock in orbit around Earth, so that it is moving really fast, compared to your position on the surface. If you could still see the clock hands, they would look smaller to you than they would on Earth, and the ticks of the clock would be slower [source: Cornell University].

The clock moves more slowly because of a phenomenon called "time dilation." Space and time are actually a single thing, called space-time, which can be distorted by gravity and acceleration. So if an object is moving very fast, or has really powerful gravity acting upon it, time for that object will slow down, compared to an object that is not being subjected to the same forces. It's possible, by using mathematical calculations, to predict just how much time will slow down for a fast-moving object.

That probably sounds pretty weird. But we know that it actually is true. GPS, the satellites of which depend upon precise measurement of time to provide map positions on Earth, is proof. The satellites are whizzing around the planet at about 8,700 miles (14,000 kilometers) per hour, and if engineers didn't adjust their clocks to compensate for relativity, within a day, Google maps on our smartphones would be giving us positions that were 6 miles (9.86 kilometers) off [source: OSU Astronomy].

Well, actually, bubbles are not always perfectly round all the time, as you probably have noticed if you've ever used one of those toy thingies to blow soap bubbles. But bubbles want to be spherical, and if you blow one that's more cigar-shaped initially, it struggles to reshape itself. That's because bubbles basically are thin layers of liquid whose molecules stick together because they are attracted to one another, a phenomenon called cohesion [source: USGS]. This creates what we think of as surface tension -- that is, a barrier that resists objects trying to move through it [source: USGS]. Inside the layer, air molecules that are trapped can't get out, even though they're pushing against the water. But that's not the only force acting on that layer. On the outside, more air is pushing inward at them. The most efficient way for the liquid layer to resist those forces is to assume the most compact shape, which happens to be a sphere, in terms of ratio of volume to surface area [source: Popular Science].

Interestingly, scientists have figured out ways to make bubbles that aren't round, so they can study the geometry of the surfaces. They're able to create bubbles that are cubical and even rectangular, by suspending a thin layer of liquid on a wire frame that that is molded into the desired shape [source: NEWTON].

Hopefully, this won't disappoint Joni Mitchell fans too much, but clouds are not actually bows of angel hair and ice cream castles in the air. A cloud is a visible mass of water droplets, or ice crystals, or a mixture of both that is suspended above Earth's surface. Clouds are formed when moist, warm air rises. As it ascends higher and reaches a space that's cooler, the moist warm air cools down, too, and the water vapor condenses back into tiny water droplets and/or ice crystals, depending upon how cold they get. Those droplets and crystals stay massed together because of the principle of cohesion, which we've previously discussed. The result is a cloud [source: Britannica ]. Some clouds are thicker than others because they happen to have a higher density of water droplets.

Clouds are a key part of our planet's hydrologic cycle, in which water continually moves between the surface and the atmosphere, and changes in state from liquid to vapor to liquid, and sometimes to solid as well. If it weren't for that cycle, there probably wouldn't be any life on our planet [source: NASA].

In 1803, a meteorologist named Luke Howard came up with four main cloud classifications, whose names were based on Latin words. Cumulus, which is the Latin word for "pile," describes those heaped, lumpy clouds that we often see in the sky. Cirrus, which means "hair," is the term for high-level clouds that look wispy, like locks of hair. Flat-looking, featureless clouds that form sheets are called stratus, which is the Latin word for "layer." Finally, there are nimbus clouds (the name actually is Latin for "precipitating cloud") are low, gray rain clouds [source: NASA]. And sometimes they combine – like the very tall grey lumpy clouds you see before thunderstorms – called a cumulonimbus!

We humans like to think of reality as a nice, stable place, where various stuff stays in the same place unless we want it to go somewhere else. But dream on. In reality, if you look at water at the molecular level, it acts like a bunch of puppies crowding into a dog bed, with molecules bumping each other and jostling for position. When a lot of water vapor is in the air, molecules will get bumped up against a surface and stick to it, which is why condensation forms on the outside of a cold drink on a humid day.

Conversely, when the air is drier, water molecules in your cup of water can get bumped up into the air and stick to other molecules that are floating around. That process is called evaporation. If the air is dry enough, more molecules will jump from your cup into the air than will stick from the air into the water. Over time, the water will continue to lose molecules to the air, and eventually you'll end up with an empty cup [source: NEWTON].

The ability of molecules from a liquid to get pushed into the air and stick to it is called vapor pressure, because the jumping molecules exert a force, just as a gas or a solid that's pressing against something would. Different liquids have different vapor pressures. A liquid such as acetone -- nail polish remover -- has a very high vapor pressure, which means that it easily evaporates and goes into the air. Olive oil, in contrast, has a very low vapor pressure, so it's not likely to evaporate much at room temperature [source: NEWTON].