What is a scientific 'theory'? Is it an idea that is unproved? If it's wrong, is it 'totally' wrong? In mathematics, a theory (or 'theorem') can be proven mathematically, in which case it is accepted as correct. An example is the Pythagorean Theorem, which can be proven to always be true. In the sciences, some theories can also be proven mathematically. But not always. Science works according to certain rules. One of them is that when a scientist has a new idea that he thinks is right, he publishes his results so scientists all around the world can check his results. If their experiments agree with his, his theory will be accepted as correct. But it doesn't stop there. Other scientists will take the theory and build on it, attempting to explain the way our world works. Eventually the theory will be the basis of many other theories, and all of them may accurately describe, predict, or explain the way things work. But, surprisingly, this does not necessarily mean that the original theory was 'correct'! It all depends what you mean by 'correct'. For example, a long time ago, most people believed the theory that the earth was flat. This is obviously an incorrect theory. Then a new theory came along. This new theory stated that the earth was a sphere. Most people believe this theory ... you probably do too. But it's not a correct theory either! In fact, the true shape of the earth is an 'oblate spheroid', which is a sphere that is thicker at the equator than at the poles. The difference in thickness is almost unnoticeable; if you drew a picture of the earth, the difference in thickness across, compared to top to bottom, would be less than the thickness of your pencil line. But the fact remains that the theory that the earth is a sphere is incorrect. However, you must agree that the sphere theory is almost correct. It's certainly a far more correct theory than the 'flat earth' one! Theories can be dead wrong. ('Flat earth') They can also be partly right. But most importantly, they can be mostly right! Here's an example of a mostly right theory. The 'Law of Gravity' is really only a theory, did you know that? (There's actually no such thing as a 'law' in science ... only a theory that most scientists accept as being mostly correct). What we mostly know about gravity was first described by Isaac Newton some 400 years ago, and his theory was so perfectly descriptive of what we experience in our ordinary world, that it was generally accepted to be true ... at least, until the 20th century, when Albert Einstein and Stephen Hawking showed that there is more to gravity than Newton realized. A new theory of gravity, one that will also explain what happens inside black holes, is now generally accepted to be 'mostly true'. Does this mean that Newton's theory of gravity is now wrong? Well, yes, ... but it was mostly correct. In fact, Newton's theory correctly describes how gravity will behave in our everyday world. It just wasn't a complete theory ... it didn't explain black holes. Another example of a theory that is not perfect, but is mostly correct, is the simple set of equations that detemine how fast something is moving. To find an object's speed, you divide the distance travelled by the time it took. For example, if it is 80 km to the nearest town, and it takes you 1 hour to get there, your average speed was 80 km/h. This is so obvious, that most people would consider it to be universally true. But of course it's not. It's only an incomplete description of how things move. It's almost totally correct. What it does not explain properly is motion that is very fast ... at speeds approaching the speed of light. A better theory by Albert Einstein, which accepted all of the old description as being true, but for low speeds , also explained speeds must faster than normal experience would make us familiar with. Do you see what we're getting at here? Just because a theory is not 100% correct, does not make it 100% wrong! In fact, most current theories in science that are decades or centuries old are probably mostly correct ... we just haven't finished them yet! The very process of scientific enquiry ensures that theories will always be reexamined and added to, as new facts emerge. But the old theories are not thrown out ... they continue to be accepted as useful, and mostly correct, with the new ideas included to make them stronger.
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