Science myths
Science is a special magnet for confident misconceptions—half-remembered from school, half-invented by intuition. A friendly correction service:
Body & biology
Myth
The claim: Deoxygenated blood is blue.
Actually: Human blood is always red — bright when oxygenated, dark red when not. Veins look bluish through skin due to how light penetrates tissue, not blue blood.
Myth
The claim: Humans have just five senses.
Actually: We have many more — balance, temperature, pain, body position (proprioception), and others. 'Five senses' is a useful oversimplification, not the full count.
Myth
The claim: Humans evolved from chimpanzees.
Actually: We didn't. Humans and chimps share a common ancestor and evolved along separate branches — chimps are cousins, not grandparents.
Myth
The claim: You must wait 30 minutes after eating before swimming or you'll cramp and drown.
Actually: There's no good evidence for a mandatory waiting period. Minor cramping is possible on a full stomach, as with any exercise, but it isn't a serious drowning risk — a myth safety organisations have walked back for decades.
Physics & space
Myth
The claim: Seasons are caused by Earth's distance from the Sun.
Actually: They're caused by Earth's axial tilt. (When the Northern Hemisphere has summer, Earth is actually slightly farther from the Sun.)
Myth
The claim: There's no gravity in space.
Actually: Gravity is everywhere — astronauts on the ISS are in constant free-fall around Earth, which feels weightless. It's not the absence of gravity.
Myth
The claim: A penny dropped from a skyscraper could kill someone.
Actually: A penny's shape and low terminal velocity mean it would sting at most — it can't reach lethal speed falling through air.
Everyday science
Myth
The claim: Water drains the opposite way in different hemispheres (Coriolis).
Actually: The Coriolis effect is far too weak to determine which way your sink or toilet drains — basin shape and water jets decide that.
Myth
The claim: Glass is a slow-moving liquid (that's why old windows are thicker at the bottom).
Actually: Glass is an amorphous solid, not a slow liquid. Old windows vary in thickness because of how they were historically made.
Earth, time & life
Myth
The claim: Diamonds form from compressed coal.
Actually: Most natural diamonds form from carbon deep in the mantle, under conditions far older and deeper than coal (which forms from plant matter) ever reaches. The two barely overlap in geologic origin.
Myth
The claim: A compass needle points to the true (geographic) North Pole.
Actually: It points toward magnetic north, which drifts over time and sits a meaningful distance from the geographic pole — the gap is called magnetic declination, and it varies by location.
Myth
The claim: Humans and dinosaurs lived at the same time.
Actually: Non-avian dinosaurs went extinct around 66 million years ago; the earliest members of the human lineage appeared only a few million years ago. The two never overlapped — though birds, dinosaurs' living descendants, coexist with us right now.
Myth
The claim: Sound travels through the vacuum of space, just fainter.
Actually: Sound needs a physical medium — air, water, solid matter — to travel as pressure waves. In the near-total vacuum of space there's essentially nothing to carry it, so, contrary to every movie explosion, space is silent. See space myths for more.
More history-flavored wrongness next door: history myths. And more space myths of the astronomical kind: space myths.