A majority of Americans don’t fully accept evolution, with over a third outright rejecting it. I’m sure you’ve encountered the classic argument from some of those people that “evolution is just a theory“.
First things first…
The word “theory” is used differently in science to how it’s used in everyday speech. When most people say “theory” they mean an educated guess based on observation, but in science that would be called a hypothesis.
A theory is a collection of hypotheses which have been supported by evidence and seeks to explain why or how something happens. A law is a concise generalisation of observations that predicts what will happen under certain circumstances, but not why.
Notice that there is no progression from theory to law – they’re different things that do different jobs. It’s not true to claim that laws are proven and theories are not, or that laws are somehow better than theories.
Theories can be wrong, but being wrong in one aspect doesn’t mean the theory has to be rejected outright. Sometimes an adjustment to fit new observations is all that’s needed.
So, now you know what we mean by a scientific theory, here are three other established theories that most people don’t reject.
1. Germ theory
The germ theory of disease, to give it its full title, is the idea most of us take for granted that infectious disease is caused by pathogens like bacteria, viruses or fungi.
Our understanding of germ theory has led to advances in disease control and prevention, including vaccinations and modern sanitation. A few people deny germ theory, but they are generally not taken too seriously.
2. General relativity
General relativity is our current best theory of gravity. Newton’s original law of universal gravitation works well for most purposes, but has a few issues which are explained by general relativity.
Notice that Newton’s law is actually less accurate than Einstein’s theory, nicely illustrating the point that laws aren’t inherently better than theories.
3. Cell theory
Cell theory describes the basic building block of life – the cell. Everything we currently consider to be alive is made up of one or more cells.
There is some discussion around cell theory because it’s possible that some giant viruses are viable non-cellular lifeforms, but we don’t generally see people denying that cells make up everything from amoeba to humans on that basis.
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This article was written as part of my November writing challenge, a NaNoWriMo-inspired attempt to write one short, snappy article a day in November. Please excuse brevity, but let me know if I’ve missed anything important!