Showing posts with label theory. Show all posts
Showing posts with label theory. Show all posts

06 January 2013

How does science work?

The universe, Part 2
< Introducing the universeSeries index | In the beginning >

We need to understand the basis upon which science operates and justifies its findings. Without this basis we would be unable to understand and describe the universe in any meaningful way. We see that science has a rigorous method and underpins reliable technology.

The famous Miller-Urey experimentBefore we look at the story of the universe, there's some groundwork we need to put in place. In the previous part I explained why I wanted to embark on this project and why I thought I'm suited to it. But this time I want to address science itself.

How do we know science works? Why should we accept its claims, for the universe or for anything else?

There are two lines of argument that should encourage us to accept the ability of science to produce valid conclusions. One is theoretical and is based on how science works. The other is practical and looks for evidence that science has worked.

How does science work? - At its most basic, science is pretty straightforward. It's really just good observation, making a best guess as to what might account for the observation, devising an experiment to test the guess, and then either rejecting the guess because it failed or making a new guess and trying again.

When a guess (science calls it an hypothesis) has been tested for a prolonged period of time and has passed every single test thrown at it, we become convinced it really is correct and then science calls it a theory. And we're not talking about ten tests, or a hundred. It may take fifty years or more of serious effort before a theory is widely accepted.

The words 'observation', 'hypothesis', 'experiment' and 'theory' are scientific jargon and should not be taken to have their everyday meanings. In the area of science they have precise definitions that we must keep in mind if we want to understand scientific debate and writing. 'Theory' in particular is commonly misunderstood.

(That is a simplified description of science, for a more thorough version read the Wikipedia article on the scientific method.)

The image above is a diagram of the apparatus used in the famous Milley-Urey experiment. This experiment disproved the hypothesis that organic chemicals could not form naturally in early planetary atmospheres.

So what does science look like in practice? - An example will help.

Let's say we notice that grass doesn't grow well underneath mature trees. That's an observation.

We might guess that grass doesn't like to be covered in dead leaves. That's an hypothesis.

We decide to grow grass in pots and then cover some of the pots with dead leaves gathered from the woods. That's an experiment.

We let the experiment run for some time and then come to look at the results. All the grass is still growing happily. So it looks as if the hypothesis was wrong, there must be some other reason that grass doesn't grow under trees. The hypothesis can't become a theory because we've shown it was wrong.

Suppose instead that we had guessed that grass needs plenty of light to grow. This time we'd find we couldn't disprove the guess. We might do dozens of different experiments and find grass always dies if it doesn't get plenty of light. We could now make a theory - 'grass needs plenty of light to grow'.

We can now say that grass almost certainly needs plenty of light to grow, and dead leaves definitely don't prevent it from growing. That's an advance in scientific knowledge.

Because of the way science works there is little room for argument. A single negative result kills an hypothesis stone dead. Hypotheses become reliable theories when they have passed many unsuccessful challenges. For example general relativity, evolution, quantum mechanics and electro-magnetism are regarded as theories. They have very, very high likelihoods of being correct and long histories of passing experimental tests.

Technology stands on the shoulders of science - Technology also gives us great confidence in the results of science. Technology often depends on the results of scientific understanding in order to make something useful or to make it more efficiently. If the underlying science was wrong, the technology based on it would fail.

The fact that technology works as well as it does is strong, additional evidence that the scientific method produces reliable and correct results. We are surrounded by proof that science is trustworthy. Cars, ships, computers, TV sets, radio communications, plastics, medicines, heart pacemakers, electricity, fridges, washing machines, microwaves, air conditioning, central heating, felt pens, emulsion paint, rubber, plant and animal breeding - all these technologies and many, many more depend on the reliability of science.

There are also examples of technology that failed because it was not based on sound science. The best example is plant breeding in the Soviet Union during the cold war. It was based on Lysenkoism, a falsified theory of inheritance.

If we can be sure science is reliable and produces correct results, then we can also be confident about what it tells us about the universe.

Questions:
  • If science is purely well-tested observation, on what grounds can we question it?
  • The nature of the universe makes technology possible, what can we conclude from that?
  • Can you imagine a world in which there were no underlying rules?

See also:



< Introducing the universeSeries index | In the beginning >

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