The Mesopotamians were the first astronomers as early as 6000 years ago.
The time it takes for an object to orbit another object.
i.e.- Earth's revolution around the Sun is 365.24 days
The turning of an object around an imaginary axis running through it.
i.e.- Earth's rotation around it's axis is 24 hours
A group of stars that seem to form a distinctive pattern in the stars.
Appear close to eachother and the same distance from Earth because they are on the same line of sight.
i.e.- Cassiopeia, Orion, etc.
Figure below shows how constellations are seen as patterns
The DISTANCE that light travels in one year
9.5 trillion () km in one year
The brightness of a star from equal distances.
Measured on a stellar magnitude scale which opes from -26 (the Sun) to over 6 in Magnitude.
A smaller group of stars that forms patterns within a constellation
i.e.- Big Dipper, Summer Triangle
Figure below shows the smaller pattern (big dipper) inside a larger constellation (Ursa Major).
The big dipper's 2 end stars are called the pointer stars because they point toward polaris.
Figure below shows the pointer stars and polaris, which they appear to point towards
The rising and fallling of ocean water as a result of the Moon's gravity and Earth's gravity.
Figure below shows how the Moon influences the tides, along with the caption below.
Phases of the Moon
The monthly progression of changes in the appearance of the Moon that result from different portions of the Moon's sunlit side being visible from Earth.
The image below shows the phases of the Moon and how they are seen from Earth.
When the full Moon passes through the umbra position of Earth's shadow so the Earth is between the Sun and the Moon.
Figure below (A) shows the Moon passing through Earth's shadow. The red Moon (B) beside it is an example of what the Moon would look like during a Lunar Eclipse.
When the shadow of the Moon falls on Earth's surface.
The moon is between the Sun and Earth during a new Moon.
Happens twice a year and can usually only be seen from very specific, often remote places on Earth's surface.
This is NOT safe to look at with the bare eye.
Figure below (B) shows the Shadow of the Moon on Earth's surface. The Black Moon with the Sun behind it (A) is what a Solar eclipse would look like from Earth.
Why do we have seasons?
On Earth, we have seasons because the Earth is on an axis. In Summer in North America, the Northern hemisphere is facing the Sun so it's rays are concentrated on the surface. In winter, the Northern hemisphere is not facing the sun so the light is spread out on the surface. Concentration of Sun's rays results in warmer weather, and when the rays are spread, it results in colder weather.
Figures below show the Sun's rays on Earth in both a concentrated way and a 'spread' way.
Figure below shows how the Earth is on an axis so the Northern hemispher ha summer solstace on June 21st.
An object that orbits one of more stars in spherical, and does not share its orbit with another object.