How Science Builds Knowledge

Films often show one lonely genius shouting "I've got it!" in a lab. Real science is almost never like that. The NSW syllabus puts it plainly: scientific research is usually collaborative and builds on the work of others. Collaborative means people work together. Building on the work of others means every new discovery stands on top of discoveries made by scientists before.

Here is what that looks like in real life.

• Scientists read what others have already found out, so they do not have to start from zero each time.
• They work in teams, often with people who have different skills, in different countries.
• They share their results so others can use them, check them and build on them.

A great Australian example is the CSIRO, our national science agency. CSIRO teams of many scientists worked together for years to develop fast wireless internet, which is now used all over the world. No single person could have done it alone. Big modern achievements, such as vaccines that protect millions of people, are built by huge international teams sharing their work step by step.

Knowledge in science grows like a tower of building blocks. Each scientist adds a block on top of the blocks placed by earlier scientists. You do not knock the tower down and start again every time; you build higher.

Think about the radio telescope at Parkes in New South Wales, nicknamed Murriyang. It can listen to faint signals from deep space. The scientists who built it used ideas about radio waves and electricity worked out by many earlier scientists. Today, astronomers from all over the world book time on it and share what they find, so the next team can go further again.

This is why scientists publish their work. When a team writes up its results, other scientists can:

• Learn from it, so they do not repeat work that is already done.
• Check it, by repeating the experiment to see if they get the same result.
• Extend it, by asking a new question that the first work made possible.

So a discovery is rarely the end of a story. It is usually a new block that helps the next group of scientists build something even taller.

People often mix up three important science words. They are different kinds of scientific idea, not stages on a ladder of evidence.

• Hypothesis: a testable proposed explanation or prediction that can be investigated, such as "warmer water makes coral go pale". A hypothesis proposes an explanation or prediction that scientists can test; it does not automatically turn into a theory or a law.
• Scientific theory: a well tested explanation for how something works, backed by lots of evidence from many experiments and observations. A theory is not a wild guess. In everyday speech "theory" can mean a hunch, but in science a theory is one of the strongest things we have, because it has survived years of testing.
• Scientific law: a statement, often short, that describes a pattern that has been observed to happen again and again. For example, things always fall down towards the Earth when dropped. A law describes what happens; a theory explains why it happens.

Scientific theories and laws are both supported by evidence, but they serve different purposes: a theory explains phenomena, while a law describes a regular pattern. Neither is a more advanced stage of the other, and one does not turn into the other.

How do repeated tests build evidence for scientific explanations and laws? Scientists test ideas, share methods and results, and check whether findings can be replicated by others. Two important steps make this happen.

• Peer review: before a result is shared widely, other expert scientists, called peers, read it carefully and check it for mistakes. A peer is a fellow expert, like a teammate who checks your work before you hand it in. If the work is not good enough, they say so, and it has to be fixed.
• Replication: other scientists repeat the experiment themselves to see if they get the same result. If many separate teams keep getting the same result, the idea becomes much more trustworthy. If they cannot repeat it, scientists become doubtful.

Think back to Barry Marshall and Robin Warren in Perth. When they first said a bacterium caused stomach ulcers, most doctors did not believe them. Their proposed explanation gained strong support after laboratories around the world repeated the work and kept getting the same result. The evidence helped establish their explanation as trusted medical knowledge, and in 2005 the two scientists won the Nobel Prize.

Because science is built up over time, our knowledge can keep getting better. If new evidence appears that does not fit, scientists update the idea, or sometimes replace it with a better one. This is a strength of science, not a weakness.

• A theory that has passed thousands of tests is very trustworthy, but it is still open to checking.
• If careful new evidence ever disagrees, scientists take that seriously and look again.
• Each improvement still builds on the work that came before. We rarely throw everything away.

For example, telescopes like Murriyang at Parkes and newer space telescopes keep giving us fresh observations of the Universe. Each new set of data lets scientists improve their explanations of how stars and galaxies work. The knowledge grows because thousands of scientists, over many years, keep observing, testing and building on each other's work. That is exactly how science builds reliable knowledge.