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Observation
Observation
• One of the best-known objects on the sky
is the Big Dipper, part of the constellation
Ursa Major (the Great Bear).
• It can be seen around the North Star on a
nightly stroll.
Observation
Observation
• The form of the asterism remains the
same throughout the day and the year.
Observation
Exploration
• Why does the position of the stars remain
the same, although the position of the
Earth in relation to them changes
throughout the year? The positions of
trees in a forest change, too, when they
are observed from different angles – in
proportion to the vicinity of the trees to
each other and to the extent the angle is
changed.
Exploration
Exploration
• The answer is hard to find in results
obtained by simple tools of observation.
That is why objects on the sky have
historically been divided into four
categories: the Sun, the Moon, the
planets, all of which move in relation to
other objects, and the fixed stars, which
stay still in relation to each other.
Concept introduction
• There are at least two logical explanations
for fixed stars.
1.The position of the stars does not change
in relation to each other. This conception
was the prevalent one for a very long time.
It was usually thought that the stars were
fixed in the celestial sphere.
Concept introduction
Concept introduction
2. The stars are so far away that the change of
their positions in relation to the Earth is very
hard to notice in the extremes of the Earth’s
orbit. What is more, for a long time it was
thought that the Earth is the center of the
universe, so this way of checking the
intervariance of the stars’ position wasn’t
even thought of before the structure of the
Solar System and Earth’s position in it was
found out in the 16th century.
Concept introduction
• This phenomenon, known as parallax, is
so imperceptible even for the nearest fixed
stars that it wasn’t until 1836 that it was
observed with precise optical instruments.
The annual parallax of the star closest to
the Earth is equivalent to the aberration of
5 mm in a journey of 1 km. The
measurements revealing this phenomenon
were first made by Friedrich Bessel.
Concept introduction
Generalization of the concept
• There is a model in the Science Centrum
Heureka with the positions of the stars of
the Big Dipper shown in the scale of 1:60
000 000 000 000 000.
• 1 centimetre in Heureka is equivalent to
600 000 millions kilometres.
• Thus we can observe what the asterism
would look like from some other angle
than the Earth.
Generalization of the concept
Generalization of the concept
• By moving around in Heureka we can
observe the Big Dipper from different
directions, and notice that it doesn’t
always retain its familiar form.
• Here is a video about watching the Big
Dipper in Heureka