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Chapter 30 Learning Goals Relate keeping track of time to astronomical cycles. Predict how the moon will appear based on its orbital position. Describe what causes the seasons. Describe what causes eclipses. Convert large numbers to scientific notation. Name the differences between stars, planets, galaxies, and the
universe. Convert between kilometers and light years. Explain how refracting and reflecting telescopes work. Name some telescopes that examine other types of electromagnetic
waves. Describe how satellites, space probes, and piloted spacecraft are
used in astronomy.
Chapter 30 Vocabulary Terms axis
calendar galaxy
light year
lunar eclipse
planet
reflecting telescope
refracting telescope
revolution
rotation
satellite
scientific notation
solar eclipse
star
telescope
universe
30.1 Cycles on Earth
Key Question:
How do we keep track of time?
*Read text section 30.1 AFTER Investigation 30.1
30.1 Cycles on EarthA calendar is a means of
keeping track of all the days in a year.
The development of a calendar came from a need to be able to predict the seasons, annual floods, and other cyclical occurrences in communities’ lives.
30.1 Phases of the MoonThe moon moves around Earth in a path called
an orbit.
How the moon appears to Earth dwellers at different positions in its orbit is shown below:
30.1 Cycles on Earth
Earth’s axis is the imaginary line that passes through its center and connects the North and South poles.
Earth’s spinning on its axis is called rotation and it brings about day and night.
30.1 Cycles on Earth The movement of one
object around another in space is called revolution.
Earth’s path as it revolves around the sun is called its orbit.
One year (365.25 days) is the amount of time it takes Earth to complete one revolution around the sun.
30.2 Tools of Astronomy
The closest star to our sun, Alpha Centauri, is 41,000,000,000,000 kilometers away.
Trying to write out astronomical distances requires a lot of zeros.
Scientific notation is a mathematical abbreviation for writing very large (or very small) numbers.
30.2 Tools of Astronomy The universe is defined as everything that exists,
including all matter and energy.
A star is a sphere of gas that undergoes a process called fusion. This process releases so much energy, the star gives off very bright light.
A planet is a large, spherical piece of matter that revolves around a star.
30.2 Tools of AstronomyA light year is the distance light travels in one
year through space (9.46 × 1012 kilometers).
ex. How many light years away is Alpha Centauri, the closest star to our sun?— Remember this star is 4.1 trillion km away...
4.1 x 1013 km ? light years=
30.2 Tools of Astronomy
4.1 x 1013 km ? light years=
xlight year1
9.46 x 1012 km4.1 x 1013 km
= 4.3 s
30.2 Tools of AstronomyA satellite is an object that
travels in orbit around another object.
The Hubble Space Telescope (or HST) is a satellite that orbits Earth. This powerful telescope sends images from deep space to computers back on Earth.
30.2 Tools of AstronomySpace probes are unmanned spacecraft that
carry scientific instruments on board.
30.2 Tools of AstronomersSpace shuttles are piloted
spacecraft that launch from rocket “boosters” and can land back on Earth like an airplane.
A space shuttle consists of three big components: two solid rocket boosters (SRBs), an external fuel tank, and an orbiter.