Movement of the Sun
what shape does the Earth have;
that the Sun has a decisive influence on the weather;
that the sun regularly rises and sets.
find the places of the Sun and it’s zenith on the celestial sphere;
discuss the relationship between the movement of the Earth and the apparent movement of the Sun in the sky;
construct a sundial;
explain the principles of a sundial.
Surely you have ridden on a carousel. When we start spinning, we notice that everything around – people, trees, buildings – alternately appear and disappear from our field of view, although they are definitely still in the same place and are not moving. And did you know that the Earth you live on is similar to a carousel that also rotates?
What is the blue vault?
When we look at the sky, it seems as if the sun, moon and stars are on the surface of the hemispherical dome. Such an apparent, non‑existent hemisphere, in the middle of which an observer is located, we call blue sphere or the celestial spherecelestial sphere. Today, of course, we know that there is no ceiling, but it is a convenient concept, facilitating for example a description of the apparent movement of the Sun in the sky or the position of the stars.
We already know that the line of apparent intersection of the earth's surface and the celestial sphere is the horizon. However, the point of intersection of the vertical line from the observer to the celestial sphere is the zenithzenith. In other words – it is a point on the celestial sphere, right above our head.
Movement of the Sun in the sky
The apparent movement of the Sun on the celestial sphere observed in Poland looks as follows:
rises every day, emerging from behind the horizon;
by noon it moves along the celestial sphere while rising;
at noon it reaches the highest position above the horizon, this moment is sun‑raisingsun‑raising;
for the remaining half‑day the sun is still moving on the celestial sphere, at the same time decreasing;
eventually the sun sets behind the horizon line.
During this journey, the altitude of the Sun changes over the horizon. We can find out about it with a simple device – sun dial.
Before you watch the movie „Movement of the Sun in the sky”, Write down the research question and the hypothesis. Make notes while watching the movie, and finally add conclusions.
Film dostępny na portalu epodreczniki.pl
Nagranie filmowe dotyczące wędrówki Słońca po niebie.
Demonstration of the relationship between the apparent movement of the Sun and the length and movement of a shadow.
an object casting a clear, narrow and long shadow, e.g. a simple stick,
observation only possible in sunny weather.
Drive the object vertically to the ground. In this way a sundial is created. Make sure it stays upright and does not tilt.
During the next breaks, mark precisely where the end of the shadow of the sundial is.
Determine if the shadow direction and its length have changed.
In the time between the first and the second observation, the shadow changed the direction in which it falls. The length of the shadow has also changed. A change in the direction of the shadow occurred as a result of the movement of the Sun in the sky, and a change in its length – due to the change in the height of the Sun above the horizon line.
You must never look at the Sun with your bare, unprotected eyes. Looking at the sun, any longer than a fraction of a second, can cause serious eye damage or even blindness.
Sundial
The shadow cast by the objects shows us the solar timesolar time. This enabled the construction of the sundialsundial. If in solar time it is noon, it is enough to indicate the direction of the shadow that is being cast then (this is the shortest shadow during the whole day with a northerly direction) and then sign it as 12.00. Then, every hour, until the evening, just mark and sign the next hours. The next day, it is worth calculating the time 6 - 7 hours earlier than the time of midday sun, then at appropriate moments mark where the shadow is falling, signing the hour. Sundials were made thousands of years ago. They are not very accurate, but they allow you to roughly determine the time.
Choose the names of a non-existent but perceived surface on which we observe the movement of the Sun.
- geoid
- geosphere
- celestial sphere
- blue sphere
- blue horizon
- zenith
Indicate the name of the apparent point lying on the blue ceiling vertically above the observer's head.
- top
- vertical
- peak of peaks
- zenith
Evaluate the truthfulness of the statements
| True | False | |
| The length of the shadow of the sundial determines the height of the Sun. | □ | □ |
| Solar time is the same everywhere in the world. | □ | □ |
| The sundial determines the time in hours based on the position of the Sun. | □ | □ |
Summary
While on Earth, we observe the apparent movement of the Sun in the sky.
The duration of the day is determined by the apparent movement of the Sun in the sky.
During the year they are changing places east, Transit and sunset.
Keywords
solar time, celestial sphere, zenith
Glossary
czas słoneczny – czas wynikający z pozycji Słońca na niebie
górowanie Słońca – moment, w którym Słońce znajduje się danego dnia najwyżej nad linią widnokręgu
sfera niebieska – inaczej sklepienie niebieskie, nieistniejąca w rzeczywistości, ale postrzegana przez nas półkula, na której powierzchni pozornie znajdują się Słońce, Księżyc i gwiazdy
zegar słoneczny – zegar odmierzający czas poprzez wskazania cienia rzucanego przez wskazówkę oświetlaną promieniami Słońca podczas jego ruchu po sklepieniu niebieskim
zenit – punkt leżący dokładnie nad obserwatorem