10 preguntas científicas que realmente deberías saber cómo responder

El gobierno de EE. UU. gasta alrededor de $ 60 mil millones al año subsidiando la investigación científica, y los programas de posgrado en ciencias e ingeniería en las universidades de EE. UU. son tan buenos que atraen a muchos de los mejores y más brillantes estudiantes del resto del mundo [fuente: National Science Foundation ]. Rodeado de maravillas tecnológicas, desde cajeros automáticos parlantes y satélites de telecomunicaciones hasta tomates de supermercado modificados genéticamente para conservar su sabor, los estadounidenses deben ser bastante inteligentes cuando se trata de ciencia, ¿no?

Bueno, adivina de nuevo. La inquietante verdad es que los adultos estadounidenses tienden a ser vergonzosamente ignorantes cuando se trata de conocimientos científicos básicos. Una encuesta de Harris Interactive de 2009 encontró que solo el 53 por ciento sabía que la Tierra tardó un año en girar alrededor del sol, y solo el 59 por ciento sabía que los primeros humanos y los dinosaurios no existieron al mismo tiempo, como lo hicieron en "The Picapiedra". Y solo el 47 por ciento afirmó correctamente, dentro de un rango de error del 10 por ciento, que alrededor del 70 por ciento de la superficie de la Tierra está cubierta por agua. Solo uno de cada cinco adultos estadounidenses podría responder correctamente las tres preguntas [fuente: ScienceDaily]. Un estudio de 2011 de la Universidad de Michigan encontró que solo el 28 por ciento de los adultos estadounidenses tenían suficiente conocimiento científico para poder leer la sección de ciencia de los martes del New York Times y comprenderla. Es cierto que eso es una mejora con respecto a un estudio de 1988, cuando solo el 10 por ciento de los adultos podía entender los artículos científicos del Times [fuente: ScienceDaily ].

Entonces, obviamente, tenemos un largo camino por recorrer para lograr algo parecido a la alfabetización científica universal. Pero para aquellos de ustedes que sienten la necesidad desesperada de cambiar de tema cuando alguien menciona el bosón de Higgs , la supercomputación paralela masiva o el creciente debate sobre si los dinosaurios tenían plumas, no teman. Vamos a comenzar de manera fácil, con las respuestas a 10 preguntas científicas realmente básicas que todos deberían saber cómo responder.

1. ¿Porque el cielo es azul?
2. ¿Qué edad tiene la Tierra?
3. ¿Cómo funciona la selección natural?
4. ¿El sol dejará de brillar alguna vez?
5. ¿Cómo funcionan los imanes?
6. ¿Qué causa un arcoíris?
7. ¿Qué es la teoría de la relatividad?
8. ¿Por qué las burbujas son redondas?
9. ¿De qué están hechas las nubes?
10. ¿Por qué el agua se evapora a temperatura ambiente?

"Veo cielos azules y nubes blancas", cantó Louis Armstrong en su canción de 1968 "What a Wonderful World". Y probablemente lo hizo, dado que su canción es una oda al optimismo. Investigadores europeos han descubierto que la luz de la parte azul del espectro influye en las emociones de manera positiva, haciéndonos más receptivos a los estímulos emocionales y más adaptables a los desafíos emocionales [fuente: Opfocus ].

Pero nos desviamos. La razón por la que el cielo parece azul es por un efecto llamado dispersión . La luz del sol tiene que atravesar la atmósfera de la Tierra, que está llena de gases y partículas que actúan como los parachoques de una máquina de pinball, haciendo rebotar la luz del sol por todas partes. Pero si alguna vez has tenido un prisma en tus manos, sabes que la luz del sol en realidad está compuesta de un montón de colores diferentes, todos los cuales tienen diferentes longitudes de onda. La luz azul tiene una longitud de onda relativamente corta, por lo que atraviesa el filtro más fácilmente que los colores con longitudes de onda más largas y, como resultado, se dispersan más ampliamente a medida que atraviesan la atmósfera. Es por eso que el cielo se ve azul durante las partes del día cuando el solparece estar alto en el cielo (aunque en realidad es el lugar del planeta donde se encuentra el que se está moviendo, en relación con el sol).

Sin embargo, al amanecer y al atardecer, los rayos del sol tienen que viajar una distancia más larga para llegar a su posición. Eso cancela la ventaja de la longitud de onda de la luz azul y nos permite ver mejor los otros colores, razón por la cual las puestas de sol a menudo aparecen rojas, naranjas o amarillas [fuentes: NASA , ScienceDaily ].

La edad de la Tierra es algo sobre lo que la gente ha estado discutiendo, a veces amargamente, durante mucho, mucho tiempo. En 1654, un erudito llamado John Lightfoot, cuyos cálculos se basaron en el Libro del Génesis de la Biblia, proclamó que la Tierra se había creado exactamente a las 9 a. m., hora de Mesopotamia, el 26 de octubre de 4004 a. El conde de Buffon calentó una pequeña réplica del planeta que había creado y midió la velocidad a la que se enfriaba y, basándose en esos datos, estimó que la Tierra tenía unos 75.000 años. En el siglo XIX, el físico Lord Kelvin usó diferentes ecuaciones para establecer la edad de la Tierra entre 20 y 40 millones de años [fuente: Badash ].

Pero todo eso fue superado a finales de 1800 y principios de 1900 por el descubrimiento de la radiactividad , que pronto fue seguido por el cálculo de las tasas a las que se descomponen varias sustancias radiactivas [fuente: Badash ]. Los científicos de la Tierra han utilizado ese conocimiento para determinar la edad de las rocas de la Tierra, así como muestras de meteoritos y rocas traídas de la Luna por los astronautas . Por ejemplo, observaron el estado de descomposición de los isótopos de plomo de las rocas y luego lo compararon con una escala basada en cálculos de cómo cambiarían los isótopos de plomo con el tiempo. A partir de eso, han podido determinar que la Tierra se formó hace aproximadamente 4.540 millones de años con una incertidumbre de menos del 1 por ciento [fuente:Servicio Geológico de Estados Unidos ].

Al igual que la edad de la Tierra, la teoría de la evolución , desarrollada por primera vez por el biólogo Charles Darwin a mediados del siglo XIX, es otro tema que tiende a preocupar a la gente. Si alguna vez vio la película clásica "Inherit the Wind", probablemente ya conozca el infame juicio del mono Scopes de 1925. El famoso abogado Clarence Darrow argumentó sin éxito en nombre de un profesor de biología de secundaria llamado John Scopes, quien fue acusado de violando un estatuto de Tennessee que prohibía a cualquiera enseñar que los humanos descendían de "un orden inferior de animales" y decretaba que la historia bíblica de la creación era la única explicación aceptable [fuente: Linder]. En los últimos años, han sido los antievolucionistas los que han luchado en los tribunales y en las legislaturas para exigir que los niños aprendan la "ciencia de la creación" en la escuela, además de la teoría de la evolución [fuente: Raffaele ].

Y si hay una idea que molesta particularmente a los antievolucionistas, es el concepto central de Darwin, que se llama selección natural . Realmente no es una idea difícil de entender. En la naturaleza, las mutaciones, es decir, un cambio permanente en el modelo genético de los organismos, que puede hacer que desarrollen características diferentes a las de sus antepasados, ocurren al azar. Pero la evolución, el proceso a más largo plazo por el cual los animales y las plantas cambian a lo largo de múltiples generaciones, no depende del azar. En cambio, los cambios en los organismos tienden a volverse más comunes con el tiempo si el cambio ayuda al organismo a sobrevivir y reproducirse mejor.

Por ejemplo, imagine que algunos escarabajos son verdes, pero luego, una mutación hace que algunos escarabajos sean marrones. Los escarabajos marrones se mezclan mejor con su entorno que los escarabajos verdes, por lo que las aves no comen muchos de ellos. En cambio, más de ellos sobrevivirán y se reproducirán, y pueden transmitir el cambio genético que hará que su descendencia sea marrón. Con el tiempo, la población de escarabajos cambiará gradualmente a un color marrón. Eso, por supuesto, es la versión simple. En la práctica, la selección natural se basa en promedios, no en individuos específicos, y no es un proceso tan fluido y ordenado [fuente: 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].

Author's Note: 10 Science Questions You Should Really Know How to Answer

He estado fascinado con la ciencia y la tecnología desde que tenía 8 años, cuando leí con entusiasmo una serie llamada How and Why Wonder Books, que trataba temas que iban desde la física nuclear hasta los dinosaurios. Incluso traté de replicar los experimentos descritos en los libros y molesté a mis padres para que me proporcionaran baterías, alambre, papel de aluminio y otras cosas que necesitaba. Incluso podría haber seguido una carrera en algún campo científico, excepto que en la escuela secundaria me di cuenta de que no me gustaban las matemáticas y que era mejor explicando experimentos y estudios a otras personas que haciendo el trabajo yo mismo. Hoy, además de escribir para , también soy blogger para el sitio web Science Channel.

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