What are facts?: The difference between scientific hypotheses, theories, and laws

Photograph of the Pacific Ocean taken from the International Space Station, July 21, 2003.

Image credit: NASA/Public domain.

First published on 16th February 2017. Last updated on 5th August 2017 by Dr Helen Klus

1. Laws, theories, hypotheses, and beliefs

A theory will never become a law; theories and laws are two separate things. Both have been thoroughly tested, and so both are often referred to as facts[1].

  • A scientific hypothesis is an idea that has not yet been tested but can be scientifically tested, even if this is just in theory. If a hypothesis is proven correct, then it becomes a law or theory.

    For example:
    Geocentricism, the hypothesis that the Sun orbits the Earth, was proven wrong when it was tested. The hypothesis that the Earth orbits the Sun was proven correct, and so became a theory - the theory of heliocentrism.

Some confusion arises because some scientific hypotheses are popularly known as theories. This is because they are mathematical theories, and the mathematics will be true even if it's shown not to apply to our universe[2][3].

For example, geocentricism has been proven wrong, but is often called the theory of geocentricism because the mathematics it's built on is correct.

Both geocentricism and heliocentrism are developed from tracking the movements of the planets. Heliocentrism explains these tracks by showing that the Earth moves around the Sun. Geocentricism explains these tracks using 'epicycles'. The mathematics of both are correct but only one really happens in our universe, and this was shown to be heliocentrism.

Other scientific hypotheses include string theory and the many worlds interpretation of quantum mechanics.

  • In science, a belief is something that has either been scientifically disproven or cannot be scientifically tested.

    For example:
    "The Earth is flat" and "The Sun rotates around the Earth" have been scientifically disproven. "God exists" may never be scientifically proven or disproven by definition.

When a belief has been scientifically disproven, it's considered by science to be an incorrect belief. The Earth has been scientifically proven to be an oblate spheroid, and so “I believe the Earth is flat” is considered to be a scientifically incorrect belief[4a]. “I believe in God” cannot be proven or disproven, and so this belief is not considered to be scientifically correct or scientifically incorrect[5].

2. How is science tested?

For a hypothesis to become a scientific law or theory, it must be proven. This seems simple enough; a hypothesis makes a prediction that is either proven correct or incorrect. In reality, however, things can get more complicated than this.

Scientists generally accept that nothing other than mathematics can ever be proven to be absolutely certain. Even if a prediction is verified hundreds of times, this alone does not mean it will be verified again.

Someone in the Northern Hemisphere might predict that all swans are white, for example, because they have only ever seen or heard of white swans, but this alone doesn't mean that black swans don't exist in the Southern Hemisphere[6a].

Scientists can never prove anything absolutely, but they can try their best to prove a hypothesis wrong. They do this by testing scientific hypotheses using a range of techniques known as the scientific method.

2.1 The scientific method

The scientific method generally involves hypotheses that make novel predictions and that can be falsified[6b]. This means that they clearly state what would have to happen for them to be proven wrong before they are tested.

A novel prediction predicts something that we were not already aware of, like Einstein's prediction that stars close to the Sun would seem to have 'moved' during an eclipse. This is different to the prediction that most planets in the Solar System would follow Newton's laws of gravity, because scientists already knew that.

The novelty of the prediction makes it less likely that the prediction would be correct if it wasn't true.

The results of novel predictions, which are often found using experiments or simulations, are generally published in peer-reviewed scientific journals. This means the paper is sent to experts in the field who check it for mistakes before it's published.

A paper will generally say how many times the prediction has been tested previously. Over time, other scientists will do the same experiment or simulation, and other papers will be written with their results. A hypothesis generally becomes a scientific law or theory when it has been tested numerous times[7][8].

3. Science vs. pseudoscience

History has shown that scientific facts provide us with information that is most likely to be true, and that the scientific method is the best way to learn scientific facts[9].

Science affects everyone in almost every way. Scientific facts are used to make decisions regarding the water we drink, the food we eat, and the air we breathe. They are used to build the houses we live in, the buildings we work in, and the transport we use. They provide us with all of our health care, and are behind all of the technology we use, including the internet. They are also used to make decisions regarding national security[10][11].

For the safety of ourselves and others, everyone needs a government that makes decisions based on scientific facts.

3.1 Why should we trust science?

One of the things that make scientific facts more certain than beliefs is that anyone can test them. Anyone can drop an object and measure its acceleration, for example, and experiments like this are performed in schools around the world.

The problem is, one theory has built on another over thousands of years, and so no one can test every single thing for themselves. The most complex, modern theories are only tested by scientists, not by members of the public, and so people have to trust others when they tell them that something is a scientific fact.

People may not know which sources of information they can trust, and we tend to trust sources that confirm our existing beliefs. This means that some people try to trick others into believing they are talking about scientific facts when they are not. Non-science that is packaged as science is known as pseudoscience[12].

3.2 How do we know something is science?

In order to make sure people know what is and isn't a scientific fact, it's important that people learn to recognise pseudoscience.

As discussed before, the differences between science and pseudoscience can be summarised as follows:

SciencePseudoscience

Tentative

Absolute knowledge

Looks for disproof

Looks for proof

Observation determines proof

Truth determines observation

Belief structure modified by observation

Belief structure unchanging

Self-modifying – attempts to correct errors

No changes – repeats errors

Beliefs like "God exists" are not pseudoscience because this belief does not claim to be scientific.

The idea that the Earth is flat[4b], that evolution does not happen[13][14], that vaccines cause autism[15], or that some races, sexualities, or genders of humans are superior to others[16][17] are all examples of pseudoscience. This is because they have all been scientifically disproven yet they make claims that trick people into thinking they are scientific.

If you are unsure of a 'fact', the first thing to do is look at where the information has originally come from. The best source is a recent peer-reviewed scientific journal. To see what peer-reviewed journals say, try typing the subject into a search engine like Google Scholar, which often leads to a free copy of the paper. Check that the paper says what people claim it says.

Try to read a number of papers to get a better idea of the scientific consensus, and try to find the most intelligent arguments for or against the 'fact', each from their own source. It is easy to defeat any argument that has been misunderstood or misrepresented. This is known as a straw man fallacy[18].

Finally, remember, it can be very difficult to accept something that we want to believe is really pseudoscience, and all our instincts will tell us not to change our minds[19], but individuals and societies are almost always better off when people make decisions based on information that is true.

4. References

  1. University of California, Berkeley, 'Science at multiple levels', last accessed 01-06-17.

  2. Siegel, E., 2015, 'Why String Theory Is Not A Scientific Theory'.

  3. Ellis, G. and Silk, J., 2014, 'Scientific method: Defend the integrity of physics'.

  4. (a, b) NOAA Satellites, 'Himawari-8 Imagery', last accessed 01-06-17.

  5. Aczel, A., 2014, 'Why Science Does Not Disprove God', Harper Collins.

  6. (a, b) Popper, K., 2005 (1959), 'The Logic of Scientific Discovery', Routledge.

  7. University of Rochester, 'Introduction to the Scientific Method', last accessed 01-06-17.

  8. Thornton, S., 'Karl Popper', Stanford Encyclopedia of Philosophy, last accessed 01-06-17.

  9. Chakravartty, A., 'Scientific Realism', Stanford Encyclopedia of Philosophy, last accessed 01-06-17.

  10. Government of the United Kingdom, 'Government Office for Science', last accessed 01-06-17.

  11. Federal Government of the United States, 'Government Science Portal', last accessed 01-06-17.

  12. Hansson, S. O., 'Science and Pseudo-Science', Stanford Encyclopedia of Philosophy, last accessed 01-06-17.

  13. Ruse, M., 'Creationism', Stanford Encyclopedia of Philosophy, last accessed 01-06-17.

  14. Coyne, J. A., 2010, 'Why Evolution is True', OUP Oxford.

  15. Plotkin, S., Gerber, J. S., and Offit, P. A., 2009, 'Vaccines and autism: a tale of shifting hypotheses', Clinical Infectious Diseases, 48, pp.456-461.

  16. Rivard, L., 2014, 'America's Hidden History: The Eugenics Movement', Nature.

  17. Eugenics Archive, 'Criticism of Eugenics', last accessed 01-06-17.

  18. Hansen, H., 'Fallacies', Stanford Encyclopedia of Philosophy, last accessed 01-06-17.

  19. Ropeik, D., 2010, 'Why Changing Somebody's Mind, or Yours, Is Hard to Do', Psychology Today.

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