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How science builds knowledge and why scientific 'theories' are more than just guesses.
If someone tells you 'All swans are white,' how many white swans do you need to see to prove them right? Surprisingly, the answer is 'infinity'—but you only need to find one black swan to prove them wrong.
1. Observation: I dropped my phone and it hit the floor. 2. Law: The Law of Gravity describes how it falls (it calculates the force based on mass and distance). 3. Theory: General Relativity explains why it falls (mass curves the fabric of space-time).
Quick Check
Which is more comprehensive: a scientific law or a scientific theory?
Answer
A scientific theory, because it explains the 'why' behind a whole range of observations and laws.
Philosopher Karl Popper argued that for a claim to be scientific, it must be falsifiable. This means there must be a way to prove it wrong through an experiment or observation. If a claim is so vague that no evidence could ever disprove it, it isn't science—it’s 'pseudoscience.' For example, saying 'An invisible ghost pushed the ball' is not falsifiable because you can't test for an invisible ghost. Science grows by trying to disprove its own best ideas. If a theory survives every attempt to break it, we can be much more confident that it is true.
Consider the statement: 'All objects fall at the same rate in a vacuum.' 1. This is falsifiable because we can drop a feather and a hammer in a vacuum chamber. 2. If they land at different times, the statement is proven wrong. 3. In 1971, Apollo 15 astronauts did this on the Moon, and they landed at the exact same time, supporting the theory.
Quick Check
Why is 'The universe was created by a magical cat that disappeared forever' not a scientific claim?
Answer
It is not falsifiable; there is no possible experiment or evidence that could prove the 'disappeared' cat didn't exist.
Scientific knowledge is tentative, meaning it is open to change. When new tools allow us to see things we couldn't see before (like powerful telescopes or particle accelerators), we might find evidence that contradicts an old theory. This doesn't mean the old theory was 'stupid'; it means it was an incomplete map. Science is a process of building better and better maps of reality. When a theory is replaced, the new one must explain all the old evidence plus the new evidence that the old theory couldn't handle.
1. Dalton (1803): Thought atoms were solid billiard balls. 2. Thomson (1904): Discovered electrons; proposed the 'plum pudding' model. 3. Rutherford (1911): Discovered the nucleus; proved atoms are mostly empty space. 4. Bohr (1913): Showed electrons move in specific energy levels. Each step didn't just guess; it used new evidence to refine the 'map' of the atom.
What is the primary difference between a law and a theory?
If a theory is 'falsifiable,' it means:
When scientists change a theory because of new evidence, it means the scientific method has failed.
Review Tomorrow
In 24 hours, try to explain to a friend why 'it's just a theory' is a scientifically inaccurate statement.
Practice Activity
Look up a 'scientific myth' that was once believed (like the idea that the Sun goes around the Earth) and identify what new evidence caused scientists to change their minds.