het607-m11a01: the scientiﬁc method: the science of...

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ofTechnology,2009HET607-M11A01: The Scientific Method: The Science ofScience

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HET607-M11A01: The Scientific Method: The Science of Science

http://astronomy.swin.edu.au/cms/sao/HET607-M11A01


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Summary

This Activity will give you an insight into the scientific process by introducing the study of Philosophyof Science, or if you like, the Science of Science.

You will examine:

• what makes a theory “scientific”;

• the Principle of Induction;

• Karl Popper and falsification; and

• Thomas Kuhn and scientific paradigms.



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While reading about astronomy or studying the Universe with SAO, have you ever thought thefollowing...



http://astronomy.swin.edu.au/cosmos/A/Astronomy

http://astronomy.swin.edu.au/cosmos/U/Universe

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But sometimes it is quite hard to quantify exactly what the scientific method is!Before we explore this more thoroughly, let’s start thinking about the processof scientific discovery with a little experiment...

In general, scientists are not wild speculators. Their theories and speculationsare guided by previous discoveries, the current understanding of particularphenomena and new experiments or observations.

You could say they follow a scientific method .

But sometimes it is quite hard to quantify exactly what the scientific method is!Before we explore this more thoroughly, let’s start thinking about the processof scientific discovery with a little experiment...



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Making sense of science

Try this simple experiment:

1. Find yourself a copy of any book covering some part of the history of astronomy. (For thepurpose of this experiment it does not matter if it is a general history or a book that covers amore specific topic).

2. Open the book to a random page.

3. On that page you will hopefully find a description of a discovery made or a theory developed byan astronomer, mathematician, physicist or some combination of the above.

4. Read this description.



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Here’s an example:“The Cambridge Concise History of Astronomy”, (1999), ed. M.Hoskin. Opened randomly at page171. Don’t worry if you are not familiar with all of the astronomical concepts we are going to coverhere - it’s just an example to help you think about the process!

Scientific DiscoveryIn 1667, the French priest-astronomer Ismael Boulliau publishes the result that the star Mira (in theconstellation Cetus) has a brightness that varies in a predictable manner, and gives an explanationbased on stellar rotation and “star spots”.

The variable star Mira in the constellation Cetus: the Whale.




http://astronomy.swin.edu.au/cosmos/S/Star

http://astronomy.swin.edu.au/cosmos/C/Constellation


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Now, ask yourself the following questions (you might not be able to answer all of them):

• How was the discovery made?

• What background information did the astronomer need?

• What information do we now know that they didn’t?

• Is their discovery still considered to be correct?

• Did it promote more discoveries or future research?



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How was the discovery made?

• To realise that Mira was a variable star, repeated observation of the star was required overseveral years to see how its brightness changed.

What background information did the astronomer need?

• Observations by David Fabricius (in 1596) and Johannes Holwarda (in 1638) that a new starappeared in Cetus that was not in the old catalogues, followed by more detailed observations byJohannes Hevelius (in 1662) that incorporated available historical data.

• Knowledge of sunspots (seen by Galileo around 1610) and solar rotation (proposed by JohannFabricius, son of David, in 1611).

• Acceptance of the idea that stars could change in brightness (ancient astronomers, up to theMiddle Ages, held that stars were unchanging).



http://astronomy.swin.edu.au/cosmos/S/Sun



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What information do we now know that they didn’t?

• Although other stars are likely to have stellar spots similar to those of the Sun, there are otherways for a star to change brightness. These include:

• eclipsing binaries, where a companion star blocks out varying amounts of light during its orbit;

• pulsating stars (e.g. Cepheid variables), where the balance between the gravitational contractionand expansion due to gas pressure is not perfect; and

• microlensing (e.g. by galactic MACHOs), where a star can have its brightness amplifiedgravitationally by an unseen object.



http://astronomy.swin.edu.au/cosmos/S/Sun

http://astronomy.swin.edu.au/cosmos/B/Binary+Star

http://astronomy.swin.edu.au/cosmos/O/Orbit

http://astronomy.swin.edu.au/cosmos/C/Cepheid+Variable+Stars

http://astronomy.swin.edu.au/cosmos/P/Pressure

http://astronomy.swin.edu.au/cosmos/G/Galaxy

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Is their discovery still considered to be correct?

• Variable stars definitely exist, but variations due to really big stellar spots are pretty unlikely.

Did it promote more discoveries or future research?

• After Boulliau’s publication, the race was on to discover more variable stars. This led to improvedmethods of measuring the brightness of stars (but not until the 18th century) and the realisationthat there were various classes of variable stars.

• Variable stars are still objects of interest to professional astronomers, and there are even activeamateur variable star networks, such as the American Association of Variable Star Observers(http://www.aavso.org).



http://astronomy.swin.edu.au/cosmos/V/Variable+Stars

http://www.aavso.org

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Science under the microscope

How did your own “random” discovery fare?

In our example, we saw how an observation (of a previously uncatalogued star) and a theory (thatits variable brightness was due to stellar spots) worked together.

Although the observation has stood the test of time, the theory has not (but it certainly spawnedfuture investigations and improved understanding of how variable stars work).

Is it possible to quantify the way the events occurred in this period of astronomical history?

Did it follow the same process as your random piece of astronomical history?

Is the progress of science and the method of scientific discovery always the same, and is it evensensible to ask whether the scientific process can be studied?



http://astronomy.swin.edu.au/cosmos/P/Period

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How does science work?

You bet! Philosophy of Science is the study of how science works.

It poses, and attempts to provide answers to, questions such as:

• What makes a theory “scientific”?

• How are new discoveries made and what happens to old theories?

• What do scientists really do with their time?

As our understanding of science has developed, so too has our understanding of the scientificprocess.

In the rest of this Activity, we will look at some of the “competing” philosophies of science.

It is worth noting that the Philosophy of Science is largely a 20th century invention. By lookingat historical cases, philosophers of science attempt to draw conclusions that can be applied tomodern-day science.



http://astronomy.swin.edu.au/cosmos/D/Day

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The ancient philosophers

Earlier in this Unit, we studied the Greek philosophers(ca.600-100 BC). These first scientists made observations ofthe world and attempted to form theories about how thingsworked.

Although they were good observers, they were not always goodexperimenters.

For example, Aristotle’s (384-322 BC) assertion that heavierobjects should fall faster than lighter objects (because of theirnatural tendency to move towards the centre of the Earth) wasaccepted without testing for nearly 2000 years! It was GalileoGalilei (1564-1642 AD) who finally demonstrated that objectsfall at the same rate, regardless of their mass.



http://astronomy.swin.edu.au/cosmos/M/Mass

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Modern science

As we have seen, the development of (Western) scientific ideas slowed down significantly betweenthe golden age of the Greek philosophers and the era of Copernicus, Galileo and Kepler (16th-17thcentury).

Instead of performing new observations, much of science was devoted to interpretation orcommentaries on the works of the ancients such as Aristotle and Ptolemy.

The origin of the modern “scientific method” is usually attributed to Francis Bacon (1561-1626 AD).

He encouraged the use of evidence and experimentation , rather than trusting to authorities (suchas Aristotle) in order to develop theories and gain an understanding of Nature.

Let’s pause for a moment and think about experiments.



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Observation versus experimentation

What do we really mean by observation and experimentation?

Observation

• I hold a tennis ball 1 metre above the ground and drop it. It happens to be a very a windy day.

• I observe that while the the ball falls towards the ground, it also seems to move sideways anddoes not hit the ground directly below where I dropped it.

In this case, something of interest happens that I make a note of.

Although I am probably able to theorise that the wind has blown the ball away from a vertical path, Ican not satisfactorily demonstrate that it is the cause, and not something else.

Perhaps tennis balls dropped from a height of 1 metre have a natural tendency to move sidewaysregardless of the weather conditions!



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Let’s try experimenting rather than observing:

Experimentation

• To determine whether the wind is responsible for moving the ball sideways, I find an enclosedspace where the wind cannot get in.

• I hold a tennis ball 1 metre above the ground and drop it, recording the location where it hits theground.

• I repeat this process numerous times.

• I then bring a small fan into the room and turn it on...

Now we are approaching something that we are probably happier to describe as “scientific”.

In order to see if the wind has an effect, I need to try dropping tennis balls when there is no wind.

I am simplifying the situation that I originally observed, in order to understand the motion of tennisballs more fully.

By repeating the experiment, I’m actually using a simple Philosophy of Science: The Principle ofInduction.



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Suppose over a period of several years we observe that the Moon goes through a sequences ofphases:

This sequence reoccurs about every 28 days.

We can then suppose that this same sequence will occur the next time the Moon is Full.

Based on our past experience , we are making a prediction about future behaviour. For the case ofthe Moon, we would be pretty surprised if something different happened, so the Principle of Inductionseems like a useful tool.



http://astronomy.swin.edu.au/cosmos/M/Moon

http://astronomy.swin.edu.au/cosmos/P/Phases

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The principle of induction

The Principle of Induction is a very powerful tool, because it allows us to make statements aboutevents that we might not have observed based on our understanding of cases we have witnessed.

Here’s an example:

1) The planet Mercury moves around the Sun in an elliptical orbit2) Halley’s Comet moves around the Sun in an elliptical orbit. . .N) The asteroid Ceres moves around the Sun in an elliptical orbit

Theory: All Solar System objects move around the Sun in elliptical orbits.

Based on our observations of elliptical motion of known cases, we extrapolate to all cases. Thismethod of extrapolation is usually referred to as induction.



http://astronomy.swin.edu.au/cosmos/P/Planet

http://astronomy.swin.edu.au/cosmos/M/Mercury

http://astronomy.swin.edu.au/cosmos/E/Ellipse

http://astronomy.swin.edu.au/cosmos/C/Comet

http://astronomy.swin.edu.au/cosmos/A/Asteroid

http://astronomy.swin.edu.au/cosmos/C/Ceres

http://astronomy.swin.edu.au/cosmos/O/Orbit

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Deduction and induction

There is a related logical tool called deduction, which works as follows:1) All Main Sequence stars are powered by nuclear burning.2) The Sun is a Main Sequence star.3) The Sun is powered by nuclear burning.

Provided statements 1 and 2 are correct, then we are able to deduce that statement 3 is also true.

For our Solar System example, we might apply our elliptical orbit theory to a new class of objects:1) All Solar System objects move around the Sun in elliptical orbits.2) SAO Students are Solar System objects.3) SAO Students move around the Sun in elliptical orbits.

But what if statement 1 or 2 was false?



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Consider the following statements.1’) All Main Sequence stars are powered by magical elves.2’) The Sun is a Main Sequence star.3’) The Sun is powered by magical elves.

Statement 3’ is perfectly valid logically, but may not be an accurate representation of the world.

Logic on its own is not enough to help us understand the way the Universe works - we need to bevery careful how we apply it!

In fact, from our Solar System example, statement 1 is not strictly true. While most Solar Systemorbits are elliptical, some long-period comets have hyperbolic orbits...



http://astronomy.swin.edu.au/cosmos/L/Long-period+Comets

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The value of induction

For induction to be useful, we need to think about:

• How many samples we used in order to generalise?

– 9 solar system objects might not be enough to make a judgement. 25 are better, but what ifwe could study 100s?

• How repeatable were the observations/experiments?

– If the observation was only ever made by one person, and nobody else can repeat it no matterhow hard they tried, should we have confidence in the result?

• Do any observations conflict with the resulting law?

– If we find even one Solar System object that does not move in an elliptical orbit, our theoryabout elliptical orbits fails. Should the theory be discarded, or is it good enough as adescription of most cases? (More on that later.)



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If we appeal to induction as sufficient evidence for the “truth” of a scientific theory, we are actuallymaking an implicit assumption about induction. . .

1) Induction worked pretty well when examining planetary orbits.2) Induction worked pretty well when examining satellite orbits.3) Induction worked pretty well when examining asteroid orbits....N) Induction worked pretty well when examining < insert observation > .

Theory: Induction always works.

This seems a little bit unsatisfactory. What if we found a single case where induction did not work?




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Looking for a better philosophy

The Principle of Induction can certainly get us started on new scientific theories, but does not seemto be sufficient to account for all cases.

In particular, what do we with our theory if the result of our induction is wrong?

In order to develop our next Philosophy of Science, we need to think a bit more about what makesa theory “scientific”. As a starting point, we would generally require that a theory be testable and/orpredictive.

Except it doesn’t always seem to be that easy. . .

How can we make objective judgements about the scientific merit of two theories?



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Falsification

Which of these two theories do you think is more “scientific”?

Theory A

If I hold a tennis ball 1 metre above the ground, and let it go, I will have a nice day.

Theory B

If I hold a tennis ball 1 metre above the ground, and let it go, I might have a nice day.

Neither of these theories is particularly “useful”: it seems pretty unlikely that there is connectionbetween dropping tennis balls and the quality of my day! But at least Theory A can be tested andfalsified .

If I drop a ball from a height of 1 metre, and do not have a nice day, then I have falsified the theory.Although I might chose to test it a few times, I will quickly discard it as a useful description of theUniverse.

If I don’t have a nice day, I am no closer to falsifying Theory B. It is a theory that does not make anydefinite predictions.



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Karl Popper

Karl Popper (1902-1994) was a philosopher from Austria whothought a great deal about the scientific process.

According to Popper, the role of a scientist was to develop atheory and then attempt to falsify it.

Theories that could not be tested in this way were not scientific.

One of Popper’s more important works was “The Logic ofScientific Discovery” (1934).



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Psuedoscience

LEO (July 23-August

22):

You may soon receive

some unexpected

money.

Popper worried about whether sociological theories (such as Marxism andFreudian psychology) were scientific.

He suggested that they were not, as they could never be falsified!

No matter what the result, the evidence could always be shown to supportthese theories.

Does this sound similar to another “theory” you may have heard referred to asa pseudoscience . . . astrology?



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Problems with astrology

Astrology makes predictions about things that will happen in your life. Often these predictions(particularly in newspaper horoscopes) are so vague that they could apply to anyone.

Experiment: Pick a newspaper horoscope at random that does not necessarily agree with your “starsign”. How accurately does it describe you?

Consider the following sample astrological predictions:

• “you may come into money”;

• “it is possible that you may have conflict in your professional life”; or

• “this week may bring an unexpected trip”.

Predictions of this type cannot be falsified. Therefore, according to Popper, astrology does notmake the grade as a science.



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Not all astrological predictions are as generalas those we have just looked at. But eventhe existence of “precise” predictions presentsa serious problem for astrology as a “science”:

Many of these precise predictions have beenproved wrong, yet astrology continues as strongas ever!

There are very few scientists who wouldcontinue to rely on a theory that had provedwrong so often...

In our journey through the History of Astronomywe have seen how astrology and astronomywere intertwined - a partnership that remainedstrong until the 17th century. Although modernscientists are very critical of astrology, it is

important to remember that without it, we might not have some of the precise star maps andplanetary observations that were critical ingredient in the Copernican Revolution.



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The role of scientists

According to Popper’s philosophy of science, the process of scientific discovery occurs as follows:

• An observation is made.

• A conjecture (that is, a theory) is developed. In order to make it open to falsification, the theoryshould be bold and clearly stated.

• Further observations/experiments are made in an effort to falsify this theory.

• If the theory is falsified, it is discarded and replaced by a new (also falsifiable) theory.

• If the theory is not falsified, that does not mean it is true - it just has not been completely testedand may be falsified in the future.

This process of theorising and falsifying is intended to bring scientists closer to a description ofreality.

What do we mean by a bold theory?

Consider the following example: “All stars are powered by nuclear reactions” is a bolder conjecturethan “The Sun is powered by nuclear reactions”. Attempts to falsify the former case will tell us moreabout the nature of stars than the later case can.



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Falsification and false theories

But hang on. If we require scientific theories must be falsifiable, doesn’t that suggest that a goodscientific theory is one that is clearly false?

Consider these two theories:

Theory A

If I hold a tennis ball 1 metre above the ground, and let it go, I will have a nice day.

Theory B

If I hold a tennis ball 1 metre above the ground, and let it go, the gravitational attraction of the Earthwill cause it to fall with an acceleration of about 10 m/s/s.

Both theories are testable (and the tests are very easy). Both theories make predictions. Yet,something tells you that Theory B is “scientific” while Theory A is largely irrelevant, and that is wherethe key lies.



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Although we can allow our falsifiable scientific theories to be bold (a condition that seems necessaryfor scientific progress) they must also be relevant .

This is why we stated early on that scientists are not wild speculators, but we can still allow them tobe speculators.



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Failing falsification

Karl Popper’s description of the scientific method as the application of theories and falsificationsseems to be a more powerful Philosophy of Science than the Principle of Induction.

You might like to go back to your random scientific discovery and think about which of thesedescriptions fits it better.

However, sometimes falsification doesn’t work!

This might be because the experimental apparatus is not accurate enough to detect a small effect,or the scientist makes a mistake. Let’s look at an example.



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The strange case of stellar parallax

Tycho Brahe (1546-1601), was one of the most accurate observers of the pre-telescopic era. But hedid not support the Copernican theory of solar system orbits, that the Sun was at the centre of theSolar System. We will be looking at Brahe’s life and work in more detail in the next Activity GatheringData....

Brahe’s reasoning was that the motion of the Earth should result in a shift of the position of the stars.

So he tried to look for this shift...

Credit: c© MacTutor

History of Mathematics

archive



http://astronomy.swin.edu.au/cosmos/T/Trigonometric+Parallax

http://www-history.mcs.st-andrews.ac.uk/Biographies/Brahe.html

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Consider the motion of the Earth about the Sun. Suppose that we are looking at a (red) star whichis slightly closer than the more distant “fixed” stars.

First, make an observation of the red star’s position when the Earth is at A.Six months later, make an observation of the red star’s position when the Earth is at B.

Compared to the “fixed stars”, the red star has moved! This effect is called parallax.



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Using the best possible equipment available at the time, Tycho Brahe looked for this shift in starpositions and did not find it.

His reasoning was this:

• If the Solar System follows Copernicus’ model;

• Then the position of stars should move due to the parallax effect as the Earth orbits the Sun;

• So if the parallax was not seen, then Copernicus is wrong.

Tycho had “falsified” the Copernican model!

There’s a problem with this: Tycho’s equipment was not quite good enough to measure the parallax.

Of course, this situation has now changed, and the parallax of hundreds of thousands of stars hasbeen measured by the Hipparcos Space Astrometry mission.

Even though it looked like falsification was the way forward for science, in this case, it led to anincorrect conclusion.



http://www.rssd.esa.int/index.php?project=HIPPARCOS

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Thomas Kuhn

Thomas Kuhn (1922-1996) started his academic career as aphysicist before switching to the history of science in the 1950s.

Kuhn disagreed with Popper’s philosophy of science, arguingthat the majority of scientists never try and falsify theories!

His ideas were described in detail in his landmark book “TheStructure of Scientific Revolutions” (first published in 1962).Kuhn proposed a sequence of events in the development ofscience, which we will now briefly explore.



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The Kuhnian scientific process

Step 1: Pre-Science

Before science can really get moving there is a stage of pre-science where there are lots of differentthoughts but no clear direction.

Step 2: Paradigm

At some point, the scientific community agrees on a particular approach. This becomes theparadigm - a set of theories and experimental results that are taken as the best available descriptionof reality.

At this point, the majority of scientists begin to conduct “normal science”.



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Two examples of paradigms in astronomy are:

• The Copernican Model: that the planets orbit the Sun (heliocentric) and not the Earth(geocentric). Note that the Copernican Model in its original form was not an adequatedescription of our Solar System. It has been modified into a paradigm that includes ellipticalorbits (thanks to Johannes Kepler).

• The standard Big Bang Model for the formation of the Universe. The majority of astronomersbase their investigations of the microwave background, evolution of the Universe, formation ofgalaxies, etc. on the assumption that the Big Bang is a good model. With a few exceptions, theydo not spend time trying to falsify it!




http://astronomy.swin.edu.au/cosmos/B/Big+Bang

http://astronomy.swin.edu.au/cosmos/G/Galaxy

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Normal scientists

If you think about the history of astronomy, there are perhaps a hundred or so people who regularlyget mentioned in astronomy books:

• Aristotle, Ptolemy, Copernicus, Galileo, Brahe, Kepler, Newton, Herschel, Hubble, etc.

Their fame was a result of their great discoveries, observations and theories that radically changedthe way the Universe was studied and understood. What are/were the countless thousands of otherastronomers up to?

According to Kuhn, they were doing exactly what they were meant to: conducting normal sciencewithin a particular paradigm.

The reality is that not every astronomer will develop a ground-breaking theory or discover anunknown object (although we would all like to!). But that does not mean that their work is wasted.

Each astronomer attempts to increase our understanding of a particular paradigm. This can involvefinding new objects or observations that it can be applied to, or identifying cases that don’t work aswell - that’s when things start to get interesting...



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Step 3: Identify Anomalies

Occasionally, an experiment or observation will turn up something that seems a bit out of the ordinary- an anomaly.

Popper might suggest that these anomalies are falsifications and so the corresponding theory shouldbe discarded.

Kuhn proposes that the best thing to do with an anomaly is to ignore it and carry on as normal. . . fora while anyway.

If the number of anomalies grows too large, then it is time to start thinking about making somechanges. It’s time for...



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Step 4: Scientific Revolution

In a Scientific Revolution, the previously dominant paradigm is thrown out and is replaced by a newone.

Revolutions may not happen instantaneously. It can take months or years for the revolution to cometo an end, in time for the final step.



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Step 5: A New Paradigm

With a new paradigm firmly in place “normal” scientists can get back to their work. . . until the nexttime anomalies arise.

Another thing happens at the introduction of a new paradigm - the textbooks get rewritten!

It no longer makes sense to describe how things work based on a paradigm that is now “out of date”.

This poses some interesting questions about our reliance on textbooks and other written resourcesthat you may like to think about, but we will not pursue them here.



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Summary

In this Activity, we have only had time to look at three main Philosophies of Science:

• Principle of Induction

• Popper and Falsification

• Kuhn and Paradigms

Each of these theories contains elements that describe the scientific process, and yet none of themseems to be a perfect description that encompasses all of science.

And that’s fine! There does not need to be a definitive answer, as every scientist is likely to tell yousomething different about the way the scientific process works.

As you progress through the remaining Activities in this Unit, The History of Astronomy, perhaps youwill develop your own interpretation of the nature of Science.

At the very least, you should have some confidence that we aren’t just making things up!

But never forget that some of the theories you learn about now may be falsified, and the nextparadigm shift could be right around the corner...



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Further reading

If you are interested in learning more about the Philosophy of Science, two useful introductory booksare:

• Alan Chalmers – What is this thing called Science?, 3rd Edition, 1999, University of QueenslandPress.

• Mel Thompson – Teach Yourself Philosophy of Science, 2001, Teach Yourself Books, Hodder &Stoughton.



het607-m11a01: the scientiﬁc method: the science of...

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