Astronomy as a Science

Science is and interpretation of the world around us.

A topic can’t really be science unless there is some type of observable data to back up conjectures.

Scientific theories can never be proven to be right, but they must always be falsifiable.

Science facts are the end product of science. Science is the investigation of the natural world

Discussion Question

What is the cause of seasons on the Earth? (in other words, why is it hot in the summer and cold in the winter?)

Please make your selection...

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1. Closeness due to elliptical orbit

2. Closeness due to tilt of the Earth

3. Energy per unit area due to tilt of Earth

4. Combination of all three

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Let’s consider a little data and think of how this could impact your previous response

The seasons are flipped between the North and South Hemispheres of the Earth. (there is winter in north while summer in south)

The Earth is closest to the Sun in January The Earth is over one million mile closer to the

Sun in January than in July. The Sun’s elevation changes throughout the

year, with the highest elevation on June 21 for Northern Hemisphere.

Clifton Suspension Bridge in Bristol, UK, between 19 December 2007 and 21 June 2008

Analemma throughout the year.

This is an image of the Sun taken at noon time throughout

the year. Notice that the Sun is sometimes very low in the sky and sometimes much higher at

noon.

Analemma – later in the afternoon

Solar energy is spread out to a much greater extent during winter months compared to summer.

What causes the Seasons?

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1. Closeness due to elliptical orbit

2. Closeness due to tilt of the Earth

3. Energy per unit area due to tilt of Earth

4. Combination of all three

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The Moon

Why does the Moon have phases? Sometimes it’s a crescent some times its full.

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1. When the Moon is a crescent you are seeing the shadow of the Earth blocking the Sun light from reaching the Moon

2. When the Moon is crescent you are seeing more of the dark side of the Moon and less of the half lit side.

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Earth-Moon from Voyageur

Earth-Moon System. Where is the Sun located in this picture?

Please make your selection...

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1. The Sun is at the top 2. The Sun is at the right3. The Sun is at the bottom4. The Sun is at the left

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Earth-Moon System. In what direction is the shadow that the Earth casts?

Please make your selection...

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1. Shadow extends to the left

2. Shadow extends upward

3. Shadow points right at the moon

4. Shadow extends to the right

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Earth-Moon System. How much of the Earth and Moon are lit by the Sun? Not what you can see,

but physically, how much is lit?

Please make your selection...

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1. The entire Earth and Moon are lit.

2. Around half of the Earth and half of the moon are lit.

3. Exactly half the Earth and half the Moon is lit.

4. Around one quarter of the Earth and moon are lit.

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Full Moon

First Quarter Moon

Waxing Crescent Moon -- The Sun is currently just below the horizon in this picture

Earth-Moon System. When the moon is at this location in its orbit, how much of the lit side of the

moon do we see from the Earth?

sunlight

Why does the Moon have phases? Sometimes it’s a crescent some times its full.

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1. When the Moon is a crescent you are seeing the shadow of the Earth blocking the Sun light from reaching the Moon

2. When the Moon is crescent you are seeing more of the dark side of the Moon and less of the half lit side.

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Solar Eclipse

Lunar Eclipse