I want to create a thread where we can discuss common misconceptions in any area of science. I think its a good thing to be aware for any teacher where they/ their students are fallable in areas of science. I have fallen foul to some myself, mainly through repeating what teachers had told me or ones that you hear in popular media. Some I can think of to start us off The sun is on 'fire' The Universe is expanding into something Deoxygenated blood is blue (Damn those diagrams) Electricity happens instantaneously Trees get most of their mass from products in the ground We can visually see protons, neutrons and electrons That electrons 'orbit' the nucleus of an atom. Scientific theory's are just guesses (Adults are particularly awful at this one, I get irritated) Sugar Makes Kids Hyperactive Being cold makes you sick (I think the jury is still out on this one so maybe needs to be omitted) Stain glass windows are thicker at the bottom because of the glasses viscosity (It was just easier to fit them with the thicker part at the bottom) When an object is moving at constant speed it needs a force on it to do so. Most kids will explain that it is being pushed. That there is such thing as a photographic memory. Not really a misconception as such but most students fail to understand quite how big the universe is or how small cells and even atoms are they have no idea.