5 Simple Science Questions We Bet You’ll Get Wrong

What is a day? What is the Earth made of? You don’t really know

Between time travel, fusion reactors and the brain transplants we hear are happening any day now, science can sound like an intimidating set of disciplines. Today, however, let’s set aside the most complicated theories and applications. Let’s try sticking to some very basic science, the sort of things everyone knows.

Because you do know quite a bit, right? Or maybe you don’t? For example, are you able to tell us...

5 How Many Minutes Does Earth Take to Rotate Once?

Every so often, we warn you when we’re about to break out the high school math. Let’s go one step further and break out the math you learned in second grade. How many minutes does it take the Earth to rotate once around its axis? Let’s see. A day is 24 hours, right? And an hour is 60 minutes. So, we multiply 24 by 60. Carry the 2, and that gives us... 1,440 minutes, a nice round figure. That’s the answer, yeah?

No, it’s not. The Earth takes 1,436 minutes for each rotation. Or, it takes 23 hours, 56 minutes and 4 seconds.

“Okay, whatever,” you might think to yourself. “So, we round that to 24 hours.” But that’s far too big a difference to round off and ignore. A difference of four minutes each day adds up to a couple hours each month. Each year, that adds up to discrepancy of 24 hours, which we’re not going to call a day because at this point, we’re questioning what a day even is anymore. What’s going on here?

The issue is: A day, as you know it, is not really the length of time the planet takes to complete one rotation. A day (24 hours) is the time the planet takes to rotate until it faces the Sun the same way as it was facing before. These two lengths of time would be the same if the Earth and Sun were stuck in place, but the Earth also revolves around the Sun.

A day (a “solar day”) varies a bit in length over the course of the year, but it averages to 24 hours all right, with no rounding required — it’s 24.00000 hours, precisely. When the Earth completes one of these solar days, it rotates more than 360 degrees, turning almost exactly 361 degrees.

A single rotation of the Earth (360 degrees) is known as a sidereal day or a stellar day, in contrast with a solar day. One way of describing the difference is a solar day is one Earth rotation with respect to the Sun while a sidereal or stellar day is one Earth rotation with respect to distant stars. We usually like describing all these movements with respect to something or another because without a frame of reference, we’ll be all lost.

4 Would It Be Sexy to Have X-Ray Vision?

We’re not asking here whether it’s physically possible to have the sci-fi power known as X-ray vision. We’re also not asking whether shooting radiation out of your eyes would be good for your long-term health (it would not). We’re simply asking, if you had the power to take X-rays of anyone you see — through magic, technology, whatever — would you enjoy this, given that you are a pervert?

If you’re a dumb kid from a couple generations ago, you would reply with a hearty “yes.” Such kids would mail away checks to buy X-ray Spex, a product that promised to look through people’s clothes. The product did not look through clothes and did not produce X-rays but would use diffraction to give you double vision. Smarter people would answer the question “no.” X-rays reveal bones. They see through clothes, but they also see through flesh, and the human skeleton is not especially erotic.

To the second group above, quick follow-up question: What about chest X-rays? You’ve surely heard of chest X-rays. They let your doctor examine your heart and lungs, which are assuredly not bones. So, X-rays do reveal stuff other than bones, stuff normally hidden from view by clothes (and possibly other layers).

This brings us to the real question we’ve been dancing around here. When you X-ray someone’s hips through their clothes, do you see any sign of their genitals? The answer to that question is a resounding yes. Behold the X-ray of a man, showing pelvis, femur, spine and at least one organ not part of the skeletal system:

In fact, doctors have a joke term for this shadowy X-ray penis. They call it the John Thomas sign (“John Thomas,” like most words, means “penis” in British slang). It’s even believed — though not substantiated by data — that the direction of a man’s John Thomas sign indicates which side of the pelvis contains a fracture.

Naturally, women aren’t likely to leave quite so prominent a display as a John Thomas sign. An X-ray may still produce a more revealing look at external features than you’d expect. Also, when X-rays zip through a vagina, the resulting scan might show a tampon or a menstrual cup, and new doctors have to be advised that this foreign object is not some worrying tumor.

As for whether you should feel aroused on seeing these clinical genital shadows, we suppose that’s something you must answer for yourself. But you might well feel a little stirred up just on learning that, until today, people have been censoring X-rays before publishing and letting you see them, believing the unedited images too naughty to share.

3 What Color Is the Sun?

The Sun is yellow, say most people with eyes. A fair number of people without any eyes would agree with this assessment, having heard the Sun described this way by those who’ve seen it. People who know more about space might offer a different answer. The Sun is actually white, they’d say. It appears yellow to us because the atmosphere has scattered away some of the less yellow components of that light, and it looks yellow in NASA photos because NASA just paints those photos whatever color they thinks looks coolest.

While “white” may be a fine answer, it leaves out some additional info about the Sun’s color that you’ll find interesting. When we describe what color an object is, we’re describing what wavelength of light it gives off. We also may be describing what wavelength light it gives off most — if an object emits small amounts of all light but a massive amount of 700-nanometer light, it will look red, and we will say it’s red.

The Sun emits light from across the entire visual spectrum, as well as electromagnetic rays too long or too short for us to see. However, it does not radiate its energy equally across all these wavelengths. It gives off most of its energy in the form of waves around 500 nanometers long. That corresponds with the color blue-green. That means the Sun’s... green?

See, if you go to space and look at the Sun, it will never look green to you. Still, that says more about you than it does about the Sun. The Sun emits green light more intensely than it does any other light, but our eyes cannot handle light data of that amplitude. We see the red light the Sun emits, and the red-sensing cells in our eyes tell us, “That is the maximum intensity of light possible.” We simultaneously see the green light the Sun emits, which is much more intense than the red light it emits, and the green-sensing cells in our eyes tell us, “That is also the maximum intensity of light possible. We can’t distinguish between those two levels; we’re only human.” We perceive the entire visual spectrum coming equally from the Sun, even though the green light’s strongest.

From one point-of-view, that means the Sun’s white. But as our friend without eyes knows, when it’s time to describe something’s color, you can’t always rely on your own limited perception.

2 What Is the World’s Most Common Substance?

While we’re in space and looking around, gaze down at Earth. In terms of surface area, it’s mostly water. However, even the very deepest oceans are a mere scratch into the Earth’s surface, so all the water in the world doesn’t add up to much. It’s just a tenth of a percent of the planet, by volume.

The Earth is mostly made of what’s inside the planet, not what stretches across the surface. What is this stuff inside the planet exactly? What is the most abundant material on Earth — or rather, what is the most abundant material on or in Earth?

Is it iron because of the iron core? Nope, that’s not it. Is it rock? Sure, but you’re going to have to be more specific than that. Anything can be considered rock. The most common substance in the world is in fact... bridgmanite. We’ll forgive you for never having heard that word before since scientists only got around to naming it within the last decade. In fact, scientists only got around to spotting a sample of this stuff within the last decade. And this sample didn’t even come from Earth.

It came from a chunk of a meteorite that fell to Australia in 1879. Well over a century after we collected this meteorite, scientists said to themselves, “Considering all the heat and pressure this meteorite experienced, we bet this has the same mineral that makes up most of the Earth’s mantle!” It then took them several years of analysis to detect this mineral in the meteorite, because electron scans are hard.

They were right. The mineral is bridgmanite, (Mg,Fe)SiO₃. We named it after Percy Bridgman, who won a Nobel prize in 1946 and was a pioneer in exerting huge pressures on materials to see what happens. We’ve never actually seen any bridgmanite that originated on Earth because it’s locked deep in the mantle, where we’ve never reached and likely never will reach. We know what sort of materials are down there, though, thanks to seismic analysis (we kind of slap the ground and then listen to what sort of waves fly back at us).

Bridgmanite makes up 38 percent of the Earth by volume. The collected works of humans and indeed the total bulk of all life of the planet is completely insignificant next to bridgmanite. But then, maybe pure cubic footage isn’t really the best way to determine what’s most important.

1 Should You Shoot C-4 Explosives, for Fun?

If you feel like answering “no” to the above question out of safety concerns, set those thoughts aside. Shooting C-4 will not endanger anyone though an explosion. Granted, there’s always the risk of accidentally shooting yourself or others, but the impact of the bullet with the C-4 itself presents no risk to anyone. On the other hand, if you answered “yes” because explosions are cool, we have bad news. The C-4 will not explode, so shooting it might be quite boring.

C-4 is extremely stable. Nitroglycerin has a nasty habit of exploding when you sneeze on it the wrong way, and dynamite has a nasty habit of sweating nitroglycerin, but C-4 resists detonating. Shoot C-4 with a gun, and it won’t explode. Touch C-4 with a flame, and it won’t explode. For C-4 to explode, it needs a shockwave, which moves faster than any bullet. Barring some rather unusual circumstances, this shockwave will only come from a dedicated detonator.

With C-4 not presenting any unintended danger, soldiers grew very comfortable around it. For example, soldiers in Vietnam would take to eating the stuff. This began with people feeling a little woozy after working with C-4, and then soldiers (as soldiers will) wondered if this might be a new way to get high. Word spread that eating little bits of plastic explosive would hit you much like a drink of alcohol would.

We don’t have a lot of documentation of how successful the C-4 was at getting people high. We instead have documentation on all the people who tried eating C-4 and ended up with headaches, seizures, spasms, kidney damage, blood in the urine and comas. Still, you gotta try it to see what will happen. That’s what science is all about.

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