Why does the sun appear to move eastwards from Earth?

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Discussion Overview

The discussion revolves around the apparent motion of the sun from the perspective of Earth, focusing on concepts of relative motion, the Earth's rotation and revolution, and how these motions affect the perceived movement of celestial bodies. Participants explore the implications of these motions on observational astronomy and seasonal changes.

Discussion Character

  • Exploratory
  • Debate/contested
  • Conceptual clarification

Main Points Raised

  • One participant notes that the Earth spins anticlockwise, leading to the sun appearing to move westward, and questions the meaning of the sun's eastward movement against the background stars.
  • Another participant challenges the assertion that the Earth's spin direction is universally anticlockwise, stating it depends on the observer's location, particularly whether one is above the North or South Pole.
  • There is a discussion about how to detect the sun's eastward movement by observing its position relative to the stars, with one participant explaining that the sun appears further east in the constellations each day.
  • Concerns are raised about the implications of the sun moving westward and whether this would affect the order of the seasons, with one participant asserting that the seasonal order would remain unchanged regardless of the direction of Earth's orbit.
  • Some participants express disagreement over the convention of describing Earth's spin and revolution from the North Pole perspective, with one suggesting that this convention may not be universally applicable.

Areas of Agreement / Disagreement

Participants express differing views on the direction of Earth's spin and its implications for the perceived motion of the sun. There is no consensus on whether the convention of describing Earth's motion from the North Pole is appropriate or universally applicable.

Contextual Notes

Participants highlight the dependence of motion descriptions on perspective, and there are unresolved questions regarding the implications of these motions on observational astronomy and seasonal changes.

amenhotep
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Hello,
I've been reading astronomy books for some time now but after leaving things for a while I seem to forget rotation directions.
For example, I know that the Earth spins in the anticlockwise direction. That is easy to see why. They say that motion of the Earth is eastwards. Because of the eastward motion of earth, the sun appears to move westwards from Earth. This means that we can verify this motion by noting that the sun first appears in the east, rises and dips in the west.
Also, the Earth revolves around the sun in an anticlockwise manner. The sun is said to move eastwards with respect to the background constellations when viewed from Earth. So, here are my questions:
1. What does "the sun appears to be moving eastwards" mean? By that, I mean, how can I detect this eastward movement by observing the sky? Is the eastward movement of the sun analogous to the sun's changing altitude in the sky at a given time of the day?
2. Because the Earth spins anticlockwise, the sun appears to move westward. Similarly, the Earth revolves anticlockwise around the sun. By the same token, why doesn't the sun appear to move westward ? If the sun was actually moving westward, what difference would that make ? Is it just reversal of seasons. Like, instead of Spring, Summer, Autumn and Winter, it will be Spring, Winter and Autumn and Summer.

I am learning astronomy purely from textbooks and as you can see I do not have a grasp of the concept of relative motion. I think I might be confusing clockwise motion with westward motion and anticlockwise motion with eastward motion.

Please feel free in being verbose in your answers. There might be many things that I don't fully grasp.

Thanks
 
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amenhotep said:
... I know that the Earth spins in the anticlockwise direction.

A remarkable thing to know, since it isn't true. The spin direction of the Earth is purely dependent on where you are. If you are above the North pole, then it is counterclockwise and if you are above the South Pole, it's clockwise.

EDIT: And in response to your recent post which you apparently deleted, if you are at the sun, you get to choose which way you care to state it since it is neither.
 
Last edited:
amenhotep said:
2. Because the Earth spins anticlockwise, the sun appears to move westward. Similarly, the Earth revolves anticlockwise around the sun. By the same token, why doesn't the sun appear to move westward ?
again not factual ... it depends on your perspective ( see Phinds's response)
 
amenhotep said:
1. What does "the sun appears to be moving eastwards" mean? By that, I mean, how can I detect this eastward movement by observing the sky? Is the eastward movement of the sun analogous to the sun's changing altitude in the sky at a given time of the day?

No, it is the movement of the Sun against the background stars. You can see this by watching the stars in the East every morning just before the Sun rises. Each day the Sun is a little further easterly in the constellations.

amenhotep said:
2. Because the Earth spins anticlockwise, the sun appears to move westward. Similarly, the Earth revolves anticlockwise around the sun. By the same token, why doesn't the sun appear to move westward ? If the sun was actually moving westward, what difference would that make ? Is it just reversal of seasons. Like, instead of Spring, Summer, Autumn and Winter, it will be Spring, Winter and Autumn and Summer.

The seasons would still be in the same order. The coldest part of the year occurs when the north hemisphere is tilted away from the Sun, Spring is next, then Summer then Fall. It makes no difference whether we are orbiting the Sun clockwise or anti-clockwise.
 
phinds said:
A remarkable thing to know, since it isn't true. The spin direction of the Earth is purely dependent on where you are. If you are above the North pole, then it is counterclockwise and if you are above the South Pole, it's clockwise.

Not true? I believe the standard convention is to describe the spin of the Earth and its revolution around the Sun as viewed from the North Pole.
 
Drakkith said:
Not true? I believe the standard convention is to describe the spin of the Earth and its revolution around the Sun as viewed from the North Pole.
Is it? I was not aware of that, but if it is then his statement was reasonable. I see that davenn agreed w/ me. I still think that as a bald, stand-alone statement, it's a bad idea, and if it's a convention, it's a bad one.
 

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