The Solar System, Explained
A friendly tour of the planets, moons and the star at the middle of it all.
Which planet is closest to the Sun?
The word "theory" causes more confusion than any other term in science. Start there.
Science is often taught as a body of facts and is better understood as a set of procedures for being wrong less often. Controls exist because the human tendency to see a pattern is extremely strong. Blinding exists because expectation changes what people report. Peer review exists because the author is the person least able to spot the flaw. These questions cover those procedures and the vocabulary attached to them, including several words that mean something quite different inside science from their ordinary use.
Every question in this quiz is listed below with its correct answer and the reasoning behind it. Play first if you would rather not see the answers — or read through as a study sheet.
Play it insteadAnswer: D. A well-supported explanation tested repeatedly
Why: It is close to the opposite of the everyday meaning, which is why "just a theory" is a misunderstanding rather than an argument.
Answer: C. Provide a comparison so the effect can be attributed to the treatment
Why: Without one, any improvement could be the illness resolving on its own, the placebo effect, or chance.
Answer: B. Neither participants nor those assessing them know who got the treatment
Why: Expectation influences both what participants report and how assessors interpret it, so concealing allocation from both is necessary.
Answer: A. Assessment by other researchers before publication
Why: It filters obvious problems and checks methods, but reviewers rarely see raw data and cannot detect determined fraud.
Answer: D. Could in principle be shown false by evidence
Why: Popper argued this is what separates a scientific claim from one that explains any possible outcome and therefore predicts nothing.
Answer: C. A result is unlikely to have arisen by chance alone
Why: It says nothing about the size or usefulness of an effect, which is why significant findings can be practically meaningless.
Answer: B. A single result can arise from chance, bias or error
Why: Systematic replication attempts across several fields have found a substantial share of published findings do not reproduce.
Answer: A. It is a specific testable prediction rather than a broad explanation
Why: A theory typically accounts for many observations and generates many hypotheses, each of which can be tested individually.
Answer: D. Combines results from many studies statistically
Why: It can reveal effects too small for individual studies to detect, but it inherits any bias present in the studies it pools.
Answer: C. Another factor may cause both, or the direction may be reversed
Why: The most common trap is a shared cause. Establishing direction usually requires an experiment rather than more observation.
How Science Actually Works has 10 questions and takes about 7 minutes to finish. It is rated Medium and sits in our Science & Nature category.
Each of the 10 correct answers adds 10 XP, up to 100 XP for a clean run. Wrong answers cost you nothing, and your full question-by-question review is shown at the end.
Yes. All 10 questions carry a written explanation of why the correct answer is right, so the quiz works as a study sheet as well as a test.
Yes, as often as you like. The questions and the answer options are reshuffled on each run, and you can use Practice Mistakes afterwards to retry only the ones you missed. No account is needed to play.
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A friendly tour of the planets, moons and the star at the middle of it all.
Which planet is closest to the Sun?
The remarkable machine you live in, from your bones to your immune system.
What is the largest organ of the human body?
The building blocks of everything, and the table that organises them.
What is the chemical symbol for gold?
Record-breakers, oddities and the rules that sort the living world.
What is the largest animal ever known to have lived?
Three pounds of tissue, eighty-six billion neurons, and the most complex object we know of.
Which is the largest part of the brain, responsible for thought and voluntary movement?
Clouds, fronts, storms and the difference between a rainy day and a warming world.
In which layer of the atmosphere does nearly all weather occur?