4.2 · Why the Sun Seems to Move

From Ohio 5th Grade Science Power Workbook · Chapter 4 · Lesson 4.2.

Big idea: The sun, moon and stars appear to move from east to west because Earth is turning underneath them.

Learning goals: Explain the apparent motion of the sun, moon and stars

Explain why the sun is not really crossing the sky

You are the one moving

The sun appears to rise in the east, cross the sky and set in the west. The moon and the stars appear to do the same thing at night.

Their daily trip from east to west is not their own motion. Earth is turning, and you are turning with it.

The same cause for all of them

It would be strange if the sun, the moon and every star all happened to travel the same way across the sky.

They do not. One thing is turning — the ground you are standing on — and that single cause explains all of it.

Worked examples

Question: A student watches the sun rise, cross the sky and set, and concludes the sun travels around Earth once a day. What reasoning would help correct this?

Steps: Notice what else does the same thing. The moon and every star appear to move the same way.

Ask what is simpler: that every object in the sky circles us, or that one thing — Earth — is turning.

One turning Earth explains every one of those apparent motions at once.

Answer: The moon and all the stars appear to move the same way. One turning Earth explains all of it, and that is what is really happening.

Common mistakes

The sky is not going around you

Your senses say the sun crosses the sky, so it feels obvious that it is moving and you are still.

You are moving. Earth turns toward the east, which makes everything in the sky appear to slide toward the west.

Check your thinking: Ask what would have to be true for the sky to really move: the sun, the moon and every single star would all have to circle us together. One turning Earth is what actually happens.

The sun does not go around Earth

Because the sun appears to circle us once a day, it is tempting to say the sun orbits Earth.

It does not. The daily trip across the sky is Earth turning. The real orbit runs the other way: Earth orbits the sun, and one trip around takes about a year, not a day.

Check your thinking: If an answer has the sun traveling around Earth, stop. Swap the roles: Earth turns each day, and Earth travels around the sun each year.

Remember

Think of a merry-go-round

Spin slowly on a playground merry-go-round and the trees appear to sweep past you. The trees are not moving. Earth is your merry-go-round.

Practice tip

Remember: Apparent means 'how it looks'.

Tip: When Ohio says the sun appears to move, it is telling you the motion is not real. The question is asking what is really moving — and the answer is Earth.

Written practice

Explain why the sun appears to move across the sky even though the sun is not traveling around Earth.

Sample response: Earth is rotating, and anyone standing on it is being carried around with it. As you turn, the sun comes into view, appears to cross the sky, and then goes out of view. The sun is not the thing that moved.

Scoring guide: 1 point: states that Earth rotates.

1 point: explains that a person standing on Earth is carried around, which makes the sun appear to move.

Ohio lists using a model or graphic to explain why the sun, stars or moon appear to move as a response attribute.