Ten Popular Myths About Astronomy

Photo of the Great Wall from orbit taken with a 180mm telephoto lens. Red arrows point to visible sections of the Wall. Credit: NASA

Myth #1: You can see the Great Wall of China from the moon and /or Earth orbit. To discern a particular feature on the Earth while standing on the moon using only your naked eye, it has to be around 70 miles across. According to Apollo 12 astronaut Alan Bean, who’s actually been there, “The only thing you can see from the Moon is a beautiful sphere, mostly white, some blue and patches of yellow, and every once in a while some green vegetation. No man-made object is visible at this scale.” The Wall may be 5,500 miles long but it only spans 30 feet. Even from the International Space Station, which orbits about 220 miles above the Earth, there have been no sightings of the Wall. Under the best lighting conditions, it might be visible with the unaided eye., but astronauts have taken pictures of part of using telephoto lenses, as in the image above.

Full moon - innocent party or culprit?

Myth #2: Birth and crime rates increase at full moon. Studies have shown no correlation, yet this myth is embedded in our culture. This one’s interesting because it’s been my experience that most people aren’t generally aware of the moon’s phase except for full moon, and once in a while, the evening crescent. The phrase “must be a full moon” was probably coined long ago, when a crime was committed or something unusual happened during the time of full moon – which to the casual observer spans some three days. The full moon is exceptionally bright and compelling, making people more likely to notice and associate it with crimes, births and bizarre behavior. These things happen just as often during a waning crescent moon, but who notices that? Even if the origin of the “must be a full moon” comment goes back to a true incident, once the expression got out there, it was repeated and handed down until today it’s what you say when no other explanation immediately presents itself.

The farside of the moon is saturated with craters compared to the nearside. Credit: NASA

Myth #3: The moon has a dark side where the sun never shines. Nope, it gets lit by the sun just like the side that always faces us. Only at full moon, when the near side of the moon is fully sunlit, is the entire back side of the moon truly dark. That’s because it faces away from the sun at that time. Just like the Earth, half the moon’s always in sunlight and half’s in shadow. When you see a first quarter moon, the right side or right half of the moon is in sunlight. That half includes the portion of the hemisphere we see from Earth plus a portion of the lunar farside we can’t see, because we can’t stretch our necks out 240,000 miles and peer around it. An astronaut orbiting the moon at that time would have no problem seeing the remainder of the farside sunlit hemisphere. When the moon is full, the nearside is the sunlit half, the farside the shadowed half. And when the moon’s an evening crescent, most of the hemisphere facing us is in the dark (except the crescent of course) while 3/4 of the farside basks in sunlight.

Myth #4: The seasons are caused by Earth’s changing distance from the sun. The seasons are caused by the 23.5 degree tilt of the Earth’s axis with respect to the plane of its orbit. That means that in summer, the Earth’s north polar axis is tipped toward the sun, causing it to swing high in the sky, giving northern hemisphere residents longer days and more direct solar rays. During winter, the pole is tipped away from the sun, causing the sun to swing low, days to shorten and solar energy to be less intense. While our planet is about 3 % closer to the sun in January than in July, that’s not enough to make a dent in winter’s cold or summer’s heat.

The colors of the Orion Nebula as they appear in a large amateur telescope

Myth #5: Objects in a telescope resemble their photographs. Pictures of galaxies and nebulas you see online, in magazines, and dare I say, in this blog, might lead you to believe that’s how they look in a telescope … or at least a really big telescope, right? The truth is that most deep sky objects are simply too faint and tenuous to excite our eyes color receptors. Most astronomical objects – outside of colorful planets like Mars, Jupiter and Saturn – appear gray. There are a few exceptions:  the Orion Nebula is pale green in a small telescope and a mix of subtle pinks and greens in larger amateur scopes. Planetary nebulas have pretty blue and green tints, too. And we can’t forget the stars, the colors of which are more vivid then when seen with the naked eye. But these hues are subtle, never garish as the photos might have us believe. The same holds true when seeing details of galaxies and nebulas through a telescope. Most are faint, feathery and misty compared to the crisp edges and sharp outlines seen in photography.

Our eyes see everything in real time while cameras allow light to accumulate. What might be faint at a glance becomes bold and obvious during a time exposure. Subtle colors deepen and brighten. By the way, getting closer to a nebula won’t make it appear any more colorful, just larger. Those technicolor scenes from sci-fi movies and depicted in artist’s views of deep sky objects stoke our imaginations but exaggerate colors just like the photographs.

Magnification's not all it's cracked up to be. Credit: UNAWE

Myth #6: Magnification is an important factor to consider when buying a telescope. You can magnify anything up to a 1000 power or higher no matter the telescope. All you need the right eyepiece, which is the lens you look through after you sighted the object of interest in your scope.”High power”has its problems. First, your field of view is constricted to something like looking through a soda straw. High magnification also spreads the light out from a planet or galaxy, making the object appear dimmer. It’s hard to see much detail in dim objects. Finally, atmospheric turbulence on most nights of the year limits the usable magnification to around 150x. Even at that, stars often look swollen and planets begin to soften up. Much more important when buying a telescope is the diameter of its main mirror or lens. That’s what gathers the light, and since many objects in the sky are quite faint, a bigger mirror means brighter, more detailed views.

Weightless astronaut aboard one of the space shuttles

Myth #7: There’s no gravity in outer space. Boy, there sure better be otherwise every manmade satellite orbiting the Earth would suddenly fly off into space. The moon would make a beeline out of here and the Earth would sever it bound with the sun and fly off to parts unknown. This myth arose because we see astronauts floating weightless inside and outside the space station and assume it’s because they don’t feel the gravity that holds the rest of us down. The reason they float is because they’re in a constant state of free fall as they orbit the Earth. While they may be traveling forward at 17,500 mph, the astronauts and their vessel are also falling to Earth. They remain in orbit and never risk hitting the ground, because they’re moving fast enough to swing around the curve of the Earth as they fall. Imagine you’re in an elevator. If it fell fast enough, you’d soon float up from the floor. You’d eventually hit bottom with disastrous consequences, but the astronauts don’t because their forward speed carries them around the Earth.

The Apollo 11 landing site photographed by the LRO. It shows the descent stage, TV camera and science experiments used or left by the astronauts. Credit: NASA

Myth #8: The Apollo moon landings were faked. Oh, pul-eez! Do we have to go there? The recent photos taken by the Lunar Reconnaissance Orbiter of the landing platforms, astronauts’ tracks and science experiments left on the moon’s surface by the Apollo crews will hopefully be the final blow to this goofball idea. Consider also the 842 lbs. of rocks returned from the missions and shared with researchers around the planet. Or how about the thousands of people involved in the program who’d all have to be “in on the deal” and keep mum all these years. Then there’s the Russians who tracked every one of the Apollo missions. If you’re still in doubt, please check out THIS SITE. Wikipedia also has a nice page on third-party evidence of the moon landings.

An illustration of a supernova or exploding star. A big if silent bang. Credit: NASA

Myth #9: You can hear sounds in space. We’re familiar with sounds of passing space ships, weapons’ blasts and things blowing up from the movies, but because space is virtually empty of particles, there’s no medium in which it can travel. All those explosions happen in silence. And don’t expect to hear the rumble of that anti-matter drive as the Enterprise glides past. It’s possible that in a nebula, which is composed of a thin mix of gas and dust, sounds might be heard. Just be careful you don’t inadvertently take off your helmet for a listen.

Hurricane Isabel photographed from the International Space Station. Credit: NASA

Myth #10: Water swirling down a drain spins clockwise in the northern hemisphere and counterclockwise in the southern. The truth is, it’s random. The confusion lies with the Coriolis Effect, an apparent deflection of moving bodies on a rotating body like Earth. It affects large objects like weather systems. For example, in a low pressure system, air flows towards the center of the disturbance. As it does, it’s deflected to the right in the northern hemisphere and to the left in the southern hemisphere. This effect only operates on large scales – your toilet bowl is simply too small to be affected. Click HERE for an excellent tutorial on the topic.

Of course, there are more myths than 10. Things like meteorites that start fires or spacecraft battling thickets of asteroids in the asteroid belt. Have you heard of any good ones? If so, send them my way, and I’ll gather them together for a future blog on the topic.

7 Responses

  1. A trick to remember which way wind flows around a high or low pressure is the right hand rule.

    Hold your right hand with your thumb pointing up. Your finger tips point to the direction the wind curls around a low pressure zone.

    Hold your right hand with your thumb pointing down. Your finger tips point to the direction the wind curls around a high pressure zone.

    Works with screws too (or just go right tighty, lefty loosey.)

    1. astrobob

      Apparently so. It’s random – it might go counterclockwise one time and clockwise another. It’s not related to which hemisphere you’re in.

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