Do Stars Really Twinkle? And Other Common Scientific Misconceptions
Scientific misconceptions are everywhere, so let’s debunk three of the basics. 1.) What causes the seasons? 2.) Is there gravity in space? 3.) Why do stars twinkle?
Sabrina Stierwalt, PhD
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Do Stars Really Twinkle? And Other Common Scientific Misconceptions
Many misconceptions arise because they provide a solution that appears to be more simple than the truth. For example, some people think that the sky is blue because the color reflects off of the blue ocean. Seems pretty straightforward, doesn’t it?
But let’s think about this explanation for a moment. What about areas of sky that don’t cover an ocean, say in the middle of Wyoming? Shouldn’t the sky there be less blue? Well, I’ve driven across the entire state of Wyoming, and I can assure you the sky there is no less blue.
The real reason has to do with preferential scattering of blue light by the Earth’s atmosphere. Although it’s a bit more complicated than a reflected ocean, it’s still a pretty straightforward concept. Let’s look at three more basic scientific misconceptions we are taught early on that don’t stand up to even a little scrutiny.
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The Earth is not closer to the Sun during the summer
A shocking number of people don’t actually know what causes the seasons, a phenomenon that constantly influences our daily decisions, because they are given the wrong explanation early on. We know that the Sun is hot, and we know that the Earth’s orbit around the Sun is not a perfect circle, so we must be closer to the Sun in our orbit during the summer and further away during the winter.
Anyone who has traveled more than 20 degrees or so both north and south of the equator knows this explanation cannot be true. At a baseball game in the U.S. in July, fans will be drinking icy beverages and eating ice cream out of miniature helmets to stay cool. On the same day, at a football game in Santiago, Chile, fans will be bundled up to stave off the cold. That’s because while the northern hemisphere experiences summer, it is winter in the southern hemisphere. Of course, the opposite is also true.
The distance from the Sun to the Earth in its orbit cannot be causing the seasons since different parts of the Earth experience different seasons at the same time.
Some people are aware that the Earth’s tilt, not its orbit, is to blame for the seasons. However, the misconception persists. The real reason is that during the summer, the portion of the Earth tilted toward the Sun has longer days and more direct sunlight, providing more opportunity for the Earth to absorb the Sun’s rays.
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There is gravity in space
Watching videos of astronauts floating around inside the space shuttle or the International Space Station, it’s easy to see how this misconception arises. However, if there really were no gravity in space, how would the planets stay in orbit around the Sun? The Moon around the Earth? Satellites around the Earth?
The truth is that gravity is everywhere in space, though it varies in strength. The reason astronauts float in space is because they are falling around the Earth at the same speed as their spacecraft. This state, called free fall, means gravity is the only force acting on them, creating an experience of relative weightlessness.
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Stars don’t really twinkle
A popular nursery rhyme tells us that stars twinkle, but this is actually due to atmospheric conditions on Earth. Stars themselves emit a constant light. The “twinkling” effect is caused by light passing through various layers of Earth’s atmosphere, which distorts the star’s light as it reaches our eyes, giving the impression of twinkling.
The reality is that they only appear to twinkle as their light travels through our atmosphere and gets refracted. The motion in the air in our atmosphere is constantly changing, even on the order of milliseconds. As a star’s light passes through that turbulent atmosphere, molecules in the atmosphere refract the star’s light in different ways from moment to moment. The “twinkling” (called scintillation) that you see arises from the slight changes in the directions from which the star’s light arrives at your eyes.
If you want to arm your kids early against this misconception, check out the astronomically correct version of Twinkle Twinkle, Litte Star from the people who bring you the Saturday Morning Breakfast Cereal comics.
Until next time, this is Sabrina Stierwalt with Ask Science’s Quick and Dirty Tips for helping you make sense of science. You can become a fan of Ask Science on Facebook or follow me on Twitter, where I’m @QDTeinstein. If you have a question that you’d like to see on a future episode, send me an email at everydayeinstein@quickanddirtytips.comcreate new email.
Images courtesy of Shutterstock.
