What do scientists do? (And why do they do
it?)
Science is a structured trial and error program.
At its core is the scientific method, the
process by which new theories are constructed
and tested.
The scientific method starts with a question
which arises from our current scientific knowledge
and observations,
such as: "why is the sky blue?",
"what is the universe made of?",
or "why do we dream?".
Let's take a look at one such question in
particle physics, and see where the scientific
method takes us.
There are four fundamental forces in nature.
These are the electromagnetic force (responsible
for electricity and magnetism),
the strong nuclear force (which binds atomic
nuclei together),
the weak nuclear force (which causes radioactive
decay) and gravity.
Each force has its own special carrier particles:
photons for electromagnetism,
gluons for the strong force, gravitons for
gravity and W and Z bosons for the weak force.
The more massive the carrier particle is,
the shorter the distances over which the corresponding
force acts.
However, there was a problem.
The weak force acts over short distances,
indicating that the W and Z bosons should
have mass.
But where did this mass come from?
No-one could write down a theory that included
it.
The case of the missing mass was a big problem
for particle physics in the early 1960's.
So, having asked our question, we need to
form a hypothesis.
This is a suggested answer to the question
posed in step one.
To construct a hypothesis, a scientist uses
a wide range of resources
such as previous work by other scientists,
ideas from other fields and their own creativity.
The resulting hypothesis is often a mathematical
model or equation.
For example, Higgs, Englert and others considered
why the W and Z have mass
and hypothesised that their mass could be
explained by introducing an extra field.
This was named the Higgs field, and it forms
part of the Standard Model of particle physics.
Now, this is all great, but in order to test
our hypothesis, we need to make some predictions.
In the case of the Higgs field,
the prediction was that by putting enough
energy into the Higgs field,
we could create the Higgs boson, which could
be detected by a large enough particle accelerator.
For our hypothesis to be scientific, its predictions
must be falsifiable.
This means that we can prove it wrong, rather
than proving it right!
As the philosopher Karl Popper famously wrote,
"no matter how many instances of white swans
we may have observed,
this does not justify the conclusion that
all swans are white".
So we can spot a thousand white swans,
and this will never prove our hypothesis that
all swans are white.
However, sighting a single black swan is enough
to disprove it.
It's for this reason that well-substantiated
hypotheses that have been rigorously tested
are called scientific theories.
They represent our best knowledge of the Universe
at this time,
but there's always the possibility of spotting
that one black swan.
The next step on the road is experimentation.
We need to test our hypothesis. And test it
again. And again.
If our hypothesis doesn't agree with experimental
evidence then it must be discarded
- it's back to the drawing board.
In the case of the Higgs boson, it took almost
fifty years from 1964, when the particle was
first proposed,
until CERN's announcement in July 2012 that
the particle had been detected.
Now we've got our experimental results, we
need to analyse them - and draw a conclusion!
This analysis typically involves a lot of data
handling and statistical analysis.
At CERN, computer programs pick out collisions
that may show traces of the Higgs boson and
analyse them.
When so much evidence had accumulated that
the chances of the Higgs not existing
and the data being a coincidence were one
in 3.5 million, CERN chose to announce their
scientific discovery.
That's not the end of the story though.
For scientific discoveries to be taken seriously,
they must be replicated
by a different team than the one that did
the original experimentation.
It is hoped that in the future, other accelerators
will be constructed that can find the Higgs
boson independently.
Scientific discoveries usually throw up a
lot more questions.
Is there just the one type of Higgs boson,
or do several varieties exist?
What are the properties of the Higgs boson?
These questions are the starting points of
further investigations, and the cycle begins
again.
We are trying to edge closer to the truth,
little by little.
All scientific knowledge is provisional, good
enough until something better comes along.
You can never prove something right in science;
you can only be proved wrong.
That's what makes it so exciting.
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