15 Out-of-This-World Facts About the International Space Station


Today marks the 16th anniversary of the first space shuttle flight to assemble the International Space Station. Let’s celebrate 16 years of the ISS with 15 things you may not have known about the world’s shared space station. 

1. Sixteen nations were involved in the construction of the ISS: The United States, Russia, Canada, Japan, Belgium, Brazil, Denmark, France, Germany, Italy, the Netherlands, Norway, Spain, Sweden, Switzerland, and the United Kingdom.  

2. Sixty-five miles per hour may be a pretty standard speed limit on highways here on Earth, but up in orbit, the ISS travels a whopping 5 miles-per-second. That means the station circles the entire planet once every 90 minutes.  

3. You may think your house or apartment is spacious, but it’s got nothing on the ISS. At about 357.6 feet (or 109 meters) long, the International Space Station gives astronauts plenty of room to stretch out.  

4. Made up of hundreds of major and minor components, the ISS is the largest manned object ever put into space. The ISS has a pressurized volume of 32,333 cubic feet, the same as a Boeing 747. It's four times larger than the Russian space station MIR and five times larger than the U.S. station Skylab. 

5. The ISS is the single most expensive object ever built. The cost of the ISS has been estimated at over $120 billion.

6.  There are only two bathrooms on the entire station. The urine of both the crewmembers and laboratory animals is filtered back into the station’s drinking water supply, so at least the astronauts will never get thirsty. 

7. Just because you’re in space doesn’t mean you can’t get a virus on your computer. The 52 computers onboard the ISS have been infected by viruses more than once. The first was a worm known as the W32.Gammima.AG, which started spreading by stealing passwords to online video games on Earth. It wasn’t a big deal, though—NASA responded by calling the virus a “nuisance.” 

8. The ISS is a veritable hub of space traffic. In June of 2014, four separate international spacecraft were docked there, including the Progress M-21M cargo spacecraft, which departed the station on June 9 after a six-month mission to drop off food, fuel, and supplies. In September, a resupply mission from SpaceX visited the station, and an entire new crew arrived that month as well. The station’s full flight schedule has docking events planned through the summer of 2016.

9. The ISS is probably one of the only places you can actually smell space. A former ISS astronaut has described how a “metallic-ionization-type smell” occurs in the area where the pressure between the station and other docking crafts is equalized.   

10. Currently, the ISS is the third brightest object in the night sky after the moon and Venus. Eagle-eyed stargazers can even spot it if they look closely enough—it looks like a fast-moving airplane. If you can’t find it, NASA has a service called Spot the Station that texts you when and where it will pass over your location. If you want the opposite view (though we’re pretty sure you won’t be able to spot yourself), there is a live video feed pointing towards Earth that runs when the crew is off-duty.

11. Though the plan is to de-orbit the ISS in 2024, the oldest module of the station—the Russian-built and American-financed component called “Zarya,” first launched in 1998—can function until 2028 (as will The Unity, the first entirely American ISS component, which was also launched that year). Once the ISS kicks the bucket, the Russians plan to add their leftover modules to their new station, OPSEK (or Orbital Piloted Assembly and Experiment Complex). 

12. Because the human body tends to lose muscle and bone mass in zero gravity environments, all astronauts aboard the ISS must work out at least two hours a day to maintain normal Earth-based bodily health.  

13. The electrical systems on the ISS include 8 miles of wire. That’s longer than the entire perimeter of New York City's Central Park.

14. Astronauts eat three square meals a day on the ISS, but when they sit down for a meal, they don’t sit down at all. There are no chairs around the main eating area. Instead, the astronauts simply stabilize themselves and float. Diners have to be very slow and careful when bringing food to their mouths so it doesn't accidentally float across the station. Also, they can’t just stroll over to the refrigerator and grab a snack—all the food is canned, dehydrated, or packaged so it doesn’t require refrigeration.  

15.  Oxygen in the ISS comes from a process called “electrolysis,” which involves using an electrical current generated from the station’s solar panels to split water molecules into hydrogen and oxygen gas. 

Dean Mouhtaropoulos/Getty Images
Essential Science
What Is a Scientific Theory?
Dean Mouhtaropoulos/Getty Images
Dean Mouhtaropoulos/Getty Images

In casual conversation, people often use the word theory to mean "hunch" or "guess": If you see the same man riding the northbound bus every morning, you might theorize that he has a job in the north end of the city; if you forget to put the bread in the breadbox and discover chunks have been taken out of it the next morning, you might theorize that you have mice in your kitchen.

In science, a theory is a stronger assertion. Typically, it's a claim about the relationship between various facts; a way of providing a concise explanation for what's been observed. The American Museum of Natural History puts it this way: "A theory is a well-substantiated explanation of an aspect of the natural world that can incorporate laws, hypotheses and facts."

For example, Newton's theory of gravity—also known as his law of universal gravitation—says that every object, anywhere in the universe, responds to the force of gravity in the same way. Observational data from the Moon's motion around the Earth, the motion of Jupiter's moons around Jupiter, and the downward fall of a dropped hammer are all consistent with Newton's theory. So Newton's theory provides a concise way of summarizing what we know about the motion of these objects—indeed, of any object responding to the force of gravity.

A scientific theory "organizes experience," James Robert Brown, a philosopher of science at the University of Toronto, tells Mental Floss. "It puts it into some kind of systematic form."


A theory's ability to account for already known facts lays a solid foundation for its acceptance. Let's take a closer look at Newton's theory of gravity as an example.

In the late 17th century, the planets were known to move in elliptical orbits around the Sun, but no one had a clear idea of why the orbits had to be shaped like ellipses. Similarly, the movement of falling objects had been well understood since the work of Galileo a half-century earlier; the Italian scientist had worked out a mathematical formula that describes how the speed of a falling object increases over time. Newton's great breakthrough was to tie all of this together. According to legend, his moment of insight came as he gazed upon a falling apple in his native Lincolnshire.

In Newton's theory, every object is attracted to every other object with a force that’s proportional to the masses of the objects, but inversely proportional to the square of the distance between them. This is known as an “inverse square” law. For example, if the distance between the Sun and the Earth were doubled, the gravitational attraction between the Earth and the Sun would be cut to one-quarter of its current strength. Newton, using his theories and a bit of calculus, was able to show that the gravitational force between the Sun and the planets as they move through space meant that orbits had to be elliptical.

Newton's theory is powerful because it explains so much: the falling apple, the motion of the Moon around the Earth, and the motion of all of the planets—and even comets—around the Sun. All of it now made sense.


A theory gains even more support if it predicts new, observable phenomena. The English astronomer Edmond Halley used Newton's theory of gravity to calculate the orbit of the comet that now bears his name. Taking into account the gravitational pull of the Sun, Jupiter, and Saturn, in 1705, he predicted that the comet, which had last been seen in 1682, would return in 1758. Sure enough, it did, reappearing in December of that year. (Unfortunately, Halley didn't live to see it; he died in 1742.) The predicted return of Halley's Comet, Brown says, was "a spectacular triumph" of Newton's theory.

In the early 20th century, Newton's theory of gravity would itself be superseded—as physicists put it—by Einstein's, known as general relativity. (Where Newton envisioned gravity as a force acting between objects, Einstein described gravity as the result of a curving or warping of space itself.) General relativity was able to explain certain phenomena that Newton's theory couldn't account for, such as an anomaly in the orbit of Mercury, which slowly rotates—the technical term for this is "precession"—so that while each loop the planet takes around the Sun is an ellipse, over the years Mercury traces out a spiral path similar to one you may have made as a kid on a Spirograph.

Significantly, Einstein’s theory also made predictions that differed from Newton's. One was the idea that gravity can bend starlight, which was spectacularly confirmed during a solar eclipse in 1919 (and made Einstein an overnight celebrity). Nearly 100 years later, in 2016, the discovery of gravitational waves confirmed yet another prediction. In the century between, at least eight predictions of Einstein's theory have been confirmed.


And yet physicists believe that Einstein's theory will one day give way to a new, more complete theory. It already seems to conflict with quantum mechanics, the theory that provides our best description of the subatomic world. The way the two theories describe the world is very different. General relativity describes the universe as containing particles with definite positions and speeds, moving about in response to gravitational fields that permeate all of space. Quantum mechanics, in contrast, yields only the probability that each particle will be found in some particular location at some particular time.

What would a "unified theory of physics"—one that combines quantum mechanics and Einstein's theory of gravity—look like? Presumably it would combine the explanatory power of both theories, allowing scientists to make sense of both the very large and the very small in the universe.


Let's shift from physics to biology for a moment. It is precisely because of its vast explanatory power that biologists hold Darwin's theory of evolution—which allows scientists to make sense of data from genetics, physiology, biochemistry, paleontology, biogeography, and many other fields—in such high esteem. As the biologist Theodosius Dobzhansky put it in an influential essay in 1973, "Nothing in biology makes sense except in the light of evolution."

Interestingly, the word evolution can be used to refer to both a theory and a fact—something Darwin himself realized. "Darwin, when he was talking about evolution, distinguished between the fact of evolution and the theory of evolution," Brown says. "The fact of evolution was that species had, in fact, evolved [i.e. changed over time]—and he had all sorts of evidence for this. The theory of evolution is an attempt to explain this evolutionary process." The explanation that Darwin eventually came up with was the idea of natural selection—roughly, the idea that an organism's offspring will vary, and that those offspring with more favorable traits will be more likely to survive, thus passing those traits on to the next generation.


Many theories are rock-solid: Scientists have just as much confidence in the theories of relativity, quantum mechanics, evolution, plate tectonics, and thermodynamics as they do in the statement that the Earth revolves around the Sun.

Other theories, closer to the cutting-edge of current research, are more tentative, like string theory (the idea that everything in the universe is made up of tiny, vibrating strings or loops of pure energy) or the various multiverse theories (the idea that our entire universe is just one of many). String theory and multiverse theories remain controversial because of the lack of direct experimental evidence for them, and some critics claim that multiverse theories aren't even testable in principle. They argue that there's no conceivable experiment that one could perform that would reveal the existence of these other universes.

Sometimes more than one theory is put forward to explain observations of natural phenomena; these theories might be said to "compete," with scientists judging which one provides the best explanation for the observations.

"That's how it should ideally work," Brown says. "You put forward your theory, I put forward my theory; we accumulate a lot of evidence. Eventually, one of our theories might prove to obviously be better than the other, over some period of time. At that point, the losing theory sort of falls away. And the winning theory will probably fight battles in the future."

This Just In
Yes, Parents Do Play Favorites—And Often Love Their Youngest Kid Best

If you have brothers or sisters, there was probably a point in your youth when you spent significant time bickering over—or at least privately obsessing over—whom Mom and Dad loved best. Was it the oldest sibling? The baby of the family? The seemingly forgotten middle kid?

As much as we'd like to believe that parents love all of their children equally, some parents do, apparently, love their youngest best, according to The Independent. A recent survey from the parenting website Mumsnet and its sister site, the grandparent-focused Gransnet, found that favoritism affects both parents and grandparents.

Out of 1185 parents and 1111 grandparents, 23 percent of parents and 42 percent of grandparents admitted to have a favorite out of their children or grandchildren. For parents, that tended to be the youngest—56 percent of those parents with a favorite said they preferred the baby of the family. Almost 40 percent of the grandparents with a favorite, meanwhile, preferred the oldest. Despite these numbers, half of the respondents thought having a favorite among their children and grandchildren is "awful," and the majority think it's damaging for that child's siblings.

Now, this isn't to say that youngest children experience blatant favoritism across all families. This wasn't a scientific study, and with only a few thousand users, the number of people with favorites is actually not as high as it might seem—23 percent is only around 272 parents, for instance. But other studies with a bit more scientific rigor have indicated that parents do usually have favorites among their children. In one study, 70 percent of fathers and 74 percent of mothers admitted to showing favoritism in their parenting. "Parents need to know that favoritism is normal," psychologist Ellen Weber Libby, who specializes in family dynamics, told The Wall Street Journal in 2017.

But youngest kids don't always feel the most loved. A 2005 study found that oldest children tended to feel like the preferred ones, and youngest children felt like their parents were biased toward their older siblings. Another study released in 2017 found that when youngest kids did feel like there was preferential treatment in their family, their relationships with their parents were more greatly affected than their older siblings, either for better (if they sensed they were the favorite) or for worse (if they sensed their siblings were). Feeling like the favorite or the lesser sibling didn't tend to affect older siblings' relationships with their parents.

However, the author of that study, Brigham Young University professor Alex Jensen, noted in a press release at the time that whether or not favoritism affects children tends to depend on how that favoritism is shown. "When parents are more loving and they're more supportive and consistent with all of the kids, the favoritism tends to not matter as much," he said, advising that “you need to treat them fairly, but not equally.” Sadly for those who don't feel like the golden child, a different study in 2016 suggests that there's not much you can do about it—mothers, at least, rarely change which child they favor most, even over the course of a lifetime.

[h/t The Independent]


More from mental floss studios