8
3.
SCIENTIFIC WORK
Scientific work consists of designing and carrying out experiments that recreate
phenomena we want to study in order to confirm or reject a hypothesis. In
experiments, the variables
2
that can influence the result are controlled.
In the previous example, in order to prove that spontaneous generation was
impossible, Redi maintained three constant factors: he used the same jars, with
raw meat for the same amount of time and he left them in the same place.
The only difference was the opening of the containers. That way, if the results were
not the same it could only be that something got into the open jar.
It is important that experiments can be repeated in order to validate the results.
When an experiment is repeated, the same results should be obtained. To do this
it is important to:
❚
Prepare detailed
guidelines
of the work we are going to do, how we are going
to do it and why this is the best way to do it.
❚
Have a
logbook
to explain the experiments and record the results.
3
trajectory
:
the path followed by
an object moving through the air
Logbook
2
variable
:
a factor that can change
and influence the result of an
experiment
Key structure
preposition at the end of a
sentence:
The angle the objects are
dropped from.
3.1.
Fieldwork
Sometimes scientists carry out experiments in the natural environment. This is
called
fieldwork
. Fieldwork allows scientists to observe and measure events in
their natural state.
For example, we can observe leaves falling from trees in the autumn, or drops of
water when it rains.
In fieldwork, it is very important to observe and record in the logbook all
the measurable variables observed in order to analyse them and try to draw
conclusions.
For example, if we see a leaf fall from a tree, we check which way the wind blows
to know how this variable influences the trajectory of the leaf.
As well as a logbook, scientists use different equipment in fieldwork such as a
compass, a camera, binoculars, jars and boxes to keep samples in, or tweezers.
Materials
❚
Three glass jars of the same size
❚
A cover for one of the jars
❚
A piece of material and an elastic
❚
Three pieces of the same kind of raw meat
Procedure
1.
Put a piece of meat in each jar.
2.
Close jar 1 with a top, cover jar 2 with material and the elastic,
and leave jar 3 open.
3.
Place the three jars in the same place.
4.
Observe the contents of the jars every day and keep a record of
any changes.
Results
After a few days, the meat in jars 1 and 2 decompose, but no living
things appear. In jar 3 maggots (mosquito and fly larvae) appear, the
meat decomposes faster and it smells bad.
Conclusions
❚
The maggots do not come from the meat itself, because if that
were the case they would be in all three jars. They do not come
from air either, because in that case they would appear in jar 2.
❚
The most probable explanation is that the maggots come from
the fly or mosquito eggs left in the meat, and that is why they
only appear in jar 3, where they had access to the meat.
