Blog post
Sci-fi vs. Sci Fact: Busting Everyday and Pop Culture Science Myths
8 Jul 2025
By Joseph Berman, Editorial Director for Science, KnowledgeWorks Global Ltd.
What You Think You Know Might Just Be a Movie Plot
In the second installment of our KGL Summer School series, we’re turning our attention to science myths that come from outside the classroom—from space battles to desert survival tips to that old “we only use 10% of our brains” trope. These misconceptions often feel true because we’ve heard them so many times. But science tells a different story.
Let’s separate cinematic fiction from scientific fact.
1. Earth’s interior is filled with magma.
You can count on an Earth science textbook to include a photo of red-hot lava flowing out the mouth of a volcano, often as a full-page opener to a chapter about volcanos. Many topics in Earth science can be illustrated only with diagrams, so dramatic photos are always welcome. [1]
Lava is molten rock, and it is called magma when it is below the surface. Because volcanos eject the magma below them, students may leap to the conclusion that Earth’s interior is filled with magma or something like it. That conclusion is wrong.
As your textbook should explain, magma only forms relatively close to the surface and under certain conditions. Earth’s mantle, which is the layer beneath the crust, is made of solid rock that acts like deformable plastic. The mantle is extremely hot, but the intense pressure keeps its rocks from melting.
2. The asteroid belt is a densely-packed debris field.
Blame science-fiction movies for this one. A densely-paced field of asteroids makes for an appealing change of scenery from the stately planets and stars. The hotshot spaceship pilot can lead the bad guys on a high-speed chase among the ever-shifting rocks, risking certain death at every turn. [2]
In fact, a spaceship could sleepwalk through the real asteroid belt and suffer no damage. On average, any two neighboring asteroids are separated by at least a few million kilometers. That’s greater than the distance between Earth and the Moon.
One fact that movies tend to get right is that asteroids come in a variety of shapes and sizes. One of the largest asteroids is the dwarf planet Ceres. Other asteroids are irregularly shaped, and most are much smaller.
3. We only use 10% of our brains.
This misconception may be the science equivalent of an urban legend. No one is sure where the idea came from, no one can cite any evidence to support it, and a lot of people seem to believe it. The myth has also been cited in many popular fictions. The movie Lucy depicts a woman who is altered to use all of her brainpower, with impressive results. [3]
Scientists have mapped every region of the brain to specific functions, involving both conscious and non-conscious action. Brain scans consistently show activity throughout the brain, even during rest and sleep. All of the evidence suggests that we use the entire brain, not some small section of it, diffuse or otherwise.
4. Light travels at a constant speed.
This statement becomes true, and an essential principle of physics, when you add the clause “through a vacuum.” Light slows down when it enters air, and it slows down even more through water or glass. The changing speed of light between media helps explain the bending of light, or refraction. Refraction allows lenses to improve eyesight and suspended raindrops to form rainbows. [4]
Another common misconception is that speed varies across the electromagnetic spectrum, of which visible light is a small part. In fact, all radiation, from radio waves to gamma rays, travels at the same constant speed through space. The radiation differs in its energy, frequency, wavelength, but not its speed.
5. You can tap water from a cactus.
We could fill a whole book with misconceptions about specific plants and animals. I’m choosing the cactus with the hope of preventing vandalism. Hacking at a saguaro will not produce a desert bubbler, but it will inflict damage on a protected species. [5]
Like all plants, cactuses do hold water in their cells and tissues. Squeeze some cactus flesh, and you might produce a drop or two of an unpleasant liquid. Generally, the liquid will contain all sorts of chemicals that make it less than palatable, and sometimes toxic, for human consumption. If you’re visiting the desert, bring water with you.
That’s my personal list of favorite science misconceptions, but many other worthy candidates are out there. Some are trivial; a few have real consequences. What do you think? Feel free to offer nominations, comments, and other feedback.
From Myths to Mastery
Whether your audience is in the classroom or at home, helping them develop critical thinking starts with content they can trust. At KnowledgeWorks Global Ltd., we specialize in building K–12 science programs that dispel myths, deepen understanding, and keep curiosity alive. Our custom content solutions meet rigorous educational standards—and spark wonder along the way.
Ready to elevate your next curriculum project? Contact us to learn more about our full-service K–12 capabilities
Joseph has over 25 years of K–12 science and math product development experience. He edited high school science textbooks at Prentice Hall and served as Science Editor and later Editorial Director of Technology at Macmillan/McGraw Hill. At Scholastic, he developed math programs such as MATH 180. Joe oversees science development for KGL and can be reached at info@kwglobal.com.
References
[1] https://education.nationalgeographic.org/resource/magma-role-rock-cycle/
[2] https://www.scientificamerican.com/article/in-science-fiction-movies/
[3] https://www.psychologicalscience.org/uncategorized/myth-we-only-use-10-of-our-brains.html
[4] https://www.space.com/how-does-light-slow-down
[5] https://www.britannica.com/story/can-you-drink-water-from-a-cactus
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