5 Common Science Misconceptions

Scientific Facts Many People Get Wrong

Even intelligent, educated people often get these science facts wrong. Here is a look at some of the most widely held scientific beliefs that simply aren't true. Don't feel bad if you believe one of these misconceptions—you're in good company.

The far side of the full moon is dark.
The far side of the full moon is dark. Richard Newstead, Getty Images

Misconception: The far side of the moon is the dark side of the moon.

Science Fact: The moon rotates as it orbits the Sun, much like the Earth. While the same side of the moon always faces the Earth, the far side could be either dark or light. When you see a full moon, the far side is dark. When you see (or rather, don't see) a new moon, the far side of the moon is bathed in sunlight.

Blood is red.
Blood is red. Science Photo Library - SCIEPRO, Getty Images

Misconception: Arterial (oxygenated) blood is red, while venous (deoxygenated) blood is blue.

Science Fact: While some animals have blue blood, humans are not among them. The red color of blood comes from hemoglobin in red blood cells. Although blood is a brighter red when it is oxygenated, it is still red when it is deoxygenated. Veins sometimes look blue or green because you view them through a layer of skin, but the blood inside is red, no matter where it is in your body.

The brightest star in the night sky is Sirius.
The brightest star in the night sky is Sirius. Max Dannenbaum, Getty Images

Misconception: The North Star (Polaris) is the brightest star in the sky.

Science Fact: Certainly the North Star (Polaris) is not the brightest star in the Southern Hemisphere, since it may not even be visible there. But even in the Northern Hemisphere, the North Star is not exceptionally bright. The Sun is by far the brightest star in the sky, and te brightest star in the night sky is Sirius.

The misconception likely arises from the North Star's use as a handy outdoor compass. The star is easily located and indicates the northern direction. 

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Lightning Never Strikes the Same Place Twice

Lightning plays over the summits of the Teton Range in Wyoming's Grand Teton National Park. Photograph copyright Robert Glusic/Getty Images

Misconception: Lightning never strikes the same place twice.

Science Fact: If you have watched a thunderstorm any length of time, you know this is not true. Lightning can strike one place multiple times. The Empire State Building gets struck around 25 times each year. Actually, any tall object is at increased risk of a lightning strike. Some people have been struck by lightning more than once.

So, if it's not true that lightning never strikes the same place twice, why do people say it? It's an idiom intended to reassure people that unfortunate events rarely befall the same person the same way more than once.

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Microwaves Make Food Radioactive

Microwave Oven
Hulton Archive/Getty Images

Misconception: Microwaves make food radioactive.

Science Fact: Microwaves do not affect the radioactivity of food.

Technically, the microwaves emitted by your microwave oven are radiation, in the same way visible light is radiation. The key is that microwaves are not ionizing radiation. A microwave oven heats food by causing the molecules to vibrate, but it does not ionize the food and it certainly does not affect the atomic nucleus, which would make food truly radioactive. If you shine a bright flashlight on your skin, it won't become radioactive. If you microwave your food, you may call it 'nuking' it, but really it's slightly more energetic light.

On a related note, microwaves do not cook food "from the inside out".