Astronomy/the Sun


QUESTION: Hi, I have been learning about the Earth's orbit at school, and would like to know why the Sun never goes down and then up in the sky? It always looks like it goes up then down instead. Thanks for your help!


When you're learning about the earth's orbit, I hope you're also learning about the earth's rotation about its axis. The earth rotates from west to east, so everything in the sky seems to move from east to west. Just like when you spin around in a circle, the rest of the world seems to move in the opposite direction.

So in the morning, the sun appears to come up (or rises) in the east, it seems to travel across the sky, and then in the evening it goes down (or sets) in the west. But you said the sun never goes down and then up. That's wrong! Start watching the sun in the evening. It goes down. Then, wait until dawn. The sun will go up. So it actually goes down and then up! Of course, it never changes direction because the earth's rotation always is in the same direction - from west to east. So the movement of the sun is always in the same direction.

Hope that helps.

Prof. James Gort

---------- FOLLOW-UP ----------

QUESTION: Hi, thanks for your answer, it helped me a lot. I also wanted to ask if it is possible for the Sun to go down then up during the day?

Hi Liz,

No, it's not possible for the sun to go down and then up during the day. For the sun to go down, it must have gotten up first. Something can't go down without being up! So the sun must have gone up first - it simply can't go down first.

It's exactly the same as throwing a ball up in the air. To start, the ball is down (in your hand). Then the ball goes up, turns around, and comes down. The ball cannot come down without being thrown up first!

Prof. James Gort  


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James Gort


Questions on observational astronomy, optics, and astrophysics. Specializing in the evolution of stars, variable stars, supernovae, neuton stars/pulsars, black holes, quasars, and cosmology.


I was a professional astronomer (University of Texas, McDonald Observatory), lecturer at the Adler Planetarium, professor of astrophysics, and amateur astronomer for 42 years. I have made numerous telescopes, and I am currently building one of the largest private observatories in Canada.

StarDate, University of Texas, numerous Journal Publications

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