10 Misconceptions About Space

People have a lot of weird misconceptions about space (thanks, Hollywood). Here are a few myths about the universe and their real explanations—and we hope you like NASA, because they're going to come up a lot.

1. The Sun is on fire.

Artist's rendering of the sun
iStock/mrtom-uk

When some people picture the Sun, they imagine something like a campfire or an object on fire. But the Sun is actually a ball of gas. It burns thanks to nuclear fusion, which happens in its core. Every second, 700 million tons of hydrogen gets converted into 695 million tons of helium. When this happens, energy is released as gamma rays, which get converted to light. So, the Sun emits light and heat, but it's not on fire, because there's no oxygen involved.

2. The Sun is the only star that has planets.

Jupiter and Mars in the solar system
iStock/themotioncloud

Experts now believe that most of the stars in our Milky Way have planets surrounding them. Any planet that's found outside of our solar system is known as an exoplanet, and we can be pretty sure that they exist because they affect the way a star appears. One of the most common ways to detect exoplanets is to look for a decrease in light from certain stars at various times, which would indicate that a planet is passing in front of the star, affecting how the light appears to us.

3. Mercury is the closest planet to the Sun, so it's the hottest.

Colorized image of Venus's clouds
NASA/JPL // Public Domain

Distance from the Sun actually has little to do with the average temperature on a planet. Venus (the second planet from the Sun) is the hottest planet in the solar system, but that's because of its atmosphere, which contains mostly carbon dioxide and some nitrogen, making it very thick. Throughout the year the surface of Venus remains at a temperature of about 462°C. The surface of Mercury, on the other hand, has a lot of temperature variations. It can be as cold as -173°C at night, and during the day it might reach 427°C. Mercury has a very thin atmosphere, which is why there's so much variation in temperature.

4. People explode in space.

NASA astronaut performing a spacewalk
NASA/JSC // Public Domain

Space is a near-vacuum, which means that people can't survive out there for more than a few minutes—but exploding isn't a concern. A body exposed in space will expand and bloat, especially the air in the lungs and the water in body tissue, but human skin is actually tight enough to prevent exploding. A person exposed to space would eventually die when circulation stops, after dissolved gases in the blood form bubbles and block flow. Basically, it's like an extreme version of "the bends" that divers can get.

5. In the 1960s, NASA spent millions developing a pen that would write in space.

NASA astronaut writing with a space pen
NASA/JSC // Public Domain

This is a popular myth on the internet—and even in one episode of The West Wing. People tend to use this as a comparison between NASA and Soviet astronauts, who were smart enough to just bring pencils. But NASA used pencils as well, and they have the receipts to prove it. In 1965, NASA placed an order for 34 mechanical pencils from Houston's Tycam Engineering Manufacturing Incorporated. There was an independent company, the Fisher Pen Company, that developed a space pen for around $1 million. And later, both NASA and the Soviets started using Fisher's anti-gravity space pen (it was a great pen).

6. In space, you experience zero gravity.

NASA astronauts experiencing decreased gravity
NASA/JSC // Public Domain">NASA/JSC // Public Domain

Gravity is considered the most important force in the universe, and it doesn't just go away when we leave Earth. Gravity is necessary for everything from the Moon's ability to orbit the Earth to the Sun staying put in the Milky Way. What astronauts actually experience in space is what NASA calls micro-gravity. It has nothing to do with the actual strength of gravity, which is only very slightly less on the International Space Station. It's because astronauts are constantly falling, so they seem weightless.

7. Black holes are like vacuums.

As we learn more and more about black holes, experts are more likely to compare them to Venus flytraps than vacuums. Black holes don't suck up everything nearby; instead, they sit pretty dormant, then if a star approaches it and gets too close, the black hole becomes active. And still, only some of the objects nearby get ripped apart by the black hole.

8. The Moon orbits Earth once a day.

Earth's moon
NASA/JPL/USGS // Public Domain

It takes about 27.3 days for the Moon to orbit Earth. This is known as a sidereal month. It's worth noting that the Moon's orbit isn't considered regular—it has variations, and there are upwards of five different months that astronomers recognize.

9. There's a dark side of the Moon.

Earth's Moon from the International Space Station
NASA/JSC // Public Domain

As the Moon is orbiting Earth, it's also rotating on its axis, so we're always seeing the same side of the Moon. But the opposite side isn't dark: it gets the same amount of sunlight as the other side.

10. A light-year measures time.

It actually measures distance. NASA defines a light-year as "the total distance that a beam of light, moving in a straight line, travels in one year." Light travels at around 300,000 kilometers per second, so a light-year is around 10 trillion (10,000,000,000,000) kilometers.

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This story was republished in 2019.

The Leonid Meteor Shower Peaks This Weekend—Here's the Best Way to Watch It

mdesigner125/iStock via Getty Images
mdesigner125/iStock via Getty Images

We're nearing the end of 2019, but there are still a few astronomical events to catch before the year is s out. This Sunday—November 17—the Leonid meteor shower is expected to peak. Here's everything you need to know before viewing the spectacle.

What is the Leonid meteor shower?

Like all meteor showers, the Leonids are caused by meteoroids from outer space burning up on their descent toward Earth. These particular shooting stars come from the rocky tail of Comet 55P/Tempel-Tuttle. Each November, debris from the comet pummels the Earth's atmosphere, causing meteors to light up the sky at rates that can exceed 1000 per hour.

The Leonids won't reach that frequency this year. According to EarthSky, the meteors would peak at a rate of around 10 to 15 per hour in a dark, moonless sky. But because the moon will be bright this weekend, sky-gazers will likely see less of them, with only the brightest shooting stars shining through.

How to See the Leonids

For your best chance of spotting the Leonids, look up the night of Sunday, November 17 and early in the morning of Monday, November 18. The shower reaches its peak after midnight. The moon will be in its waning gibbous phase at that time, so even with clear skies, viewing conditions won't be ideal. But there are ways to increase your chances of seeing as many meteors as possible. Try finding a large object to stand under—such as a tree or building—that will block your view of the moon. If you don't see anything right away, be patient: The more time you give your eyes to adjust to the darkness, the more likely you are to spot a shooting star.

What is Mercury in Retrograde, and Why Do We Blame Things On It?

NASA
NASA

Crashed computers, missed flights, tensions in your workplace—a person who subscribes to astrology would tell you to expect all this chaos and more when Mercury starts retrograding. For the remainder of 2019, that means October 31-November 20. But according to an astronomer, this common celestial phenomenon is no reason to stay cooped up at home for weeks at a time.

"We don't know of any physical mechanism that would cause things like power outages or personality changes in people," Dr. Mark Hammergren, an astronomer at Chicago's Adler Planetarium, tells Mental Floss. So if Mercury doesn’t throw business dealings and relationships out of whack when it appears to change direction in the sky, why are so many people convinced that it does?

The History of "Mercury in Retrograde"

Mercury retrograde—as it's technically called—was being written about in astrology circles as far back as the mid-18th century. The event was noted in British agricultural almanacs of the time, which farmers would read to sync their planting schedules to the patterns of the stars. During the spiritualism craze of the Victorian era, interest in astrology boomed, with many believing that the stars affected the Earth in a variety of (often inconvenient) ways. Late 19th-century publications like The Astrologer’s Magazine and The Science of the Stars connected Mercury retrograde with heavy rainfall. Characterizations of the happening as an "ill omen" also appeared in a handful of articles during that period, but its association with outright disaster wasn’t as prevalent then as it is today.

While other spiritualist hobbies like séances and crystal gazing gradually faded, astrology grew even more popular. By the 1970s, horoscopes were a newspaper mainstay and Mercury retrograde was a recurring player. Because the Roman god Mercury was said to govern travel, commerce, financial wealth, and communication, in astrological circles, Mercury the planet became linked to those matters as well.

"Don’t start anything when Mercury is retrograde," an April 1979 issue of The Baltimore Sun instructed its readers. "A large communications organization notes that magnetic storms, disrupting messages, are prolonged when Mercury appears to be going backwards. Mercury, of course, is the planet associated with communication." The power attributed to the event has become so overblown that today it's blamed for everything from digestive problems to broken washing machines.

What is Mercury in Retrograde?

Though hysteria around Mercury retrograde is stronger than ever, there's still zero evidence that it's something we should worry about. Even the flimsiest explanations, like the idea that the gravitational pull from Mercury influences the water in our bodies in the same way that the moon controls the tides, are easily deflated by science. "A car 20 feet away from you will exert a stronger pull of gravity than the planet Mercury does," Dr. Hammergren says.

To understand how little Mercury retrograde impacts life on Earth, it helps to learn the physical process behind the phenomenon. When the planet nearest to the sun is retrograde, it appears to move "backwards" (east to west rather than west to east) across the sky. This apparent reversal in Mercury's orbit is actually just an illusion to the people viewing it from Earth. Picture Mercury and Earth circling the sun like cars on a racetrack. A year on Mercury is shorter than a year on Earth (88 Earth days compared to 365), which means Mercury experiences four years in the time it takes us to finish one solar loop.

When the planets are next to one another on the same side of the sun, Mercury looks like it's moving east to those of us on Earth. But when Mercury overtakes Earth and continues its orbit, its straight trajectory seems to change course. According to Dr. Hammergren, it's just a trick of perspective. "Same thing if you were passing a car on a highway, maybe going a little bit faster than they are," he says. "They're not really going backwards, they just appear to be going backwards relative to your motion."

Embedded from GIFY

Earth's orbit isn't identical to that of any other planet in the solar system, which means that all the planets appear to move backwards at varying points in time. Planets farther from the sun than Earth have even more noticeable retrograde patterns because they're visible at night. But thanks to astrology, it's Mercury's retrograde motion that incites dread every few months.

Dr. Hammergren blames the superstition attached to Mercury, and astrology as a whole, on confirmation bias: "[Believers] will say, 'Aha! See, there's a shake-up in my workplace because Mercury's retrograde.'" He urges people to review the past year and see if the periods of their lives when Mercury was retrograde were especially catastrophic. They'll likely find that misinterpreted messages and technical problems are fairly common throughout the year. But as Dr. Hammergren says, when things go wrong and Mercury isn't retrograde, "we don't get that hashtag. It's called Monday."

This piece originally ran in 2018.

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