# Earth in motion

**URL:** <https://boards.straightdope.com/t/earth-in-motion/52982>\
**Category:** Factual Questions\
**Created:** [February 3, 2001, 5:49am UTC](https://boards.straightdope.com/t/earth-in-motion/52982 "2001-02-03T05:49:26Z")\
**Posts on this page:** 6\
**Page:** 1

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**Author:** ![phreesh](https://avatars.discourse-cdn.com/v4/letter/p/9fc29f/32.png) [@phreesh](https://boards.straightdope.com/u/phreesh)\
**Post date:** [February 3, 2001, 5:49am UTC](https://boards.straightdope.com/t/earth-in-motion/52982/1 "2001-02-03T05:49:26Z")

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How can you prove to someone that the Earth revolves around the sun? Is there more than one way?

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**Author:** ![Mikahw](https://avatars.discourse-cdn.com/v4/letter/m/e9bcb4/32.png) [@Mikahw](https://boards.straightdope.com/u/Mikahw)\
**Post date:** [February 3, 2001, 5:52am UTC](https://boards.straightdope.com/t/earth-in-motion/52982/2 "2001-02-03T05:52:58Z")

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Sure. How about it has to orbit, or else it’d crash into the sun.

If you’re looking for a slightly… different approach, just look at the stars.

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**Author:** ![phreesh](https://avatars.discourse-cdn.com/v4/letter/p/9fc29f/32.png) [@phreesh](https://boards.straightdope.com/u/phreesh)\
**Post date:** [February 3, 2001, 5:58am UTC](https://boards.straightdope.com/t/earth-in-motion/52982/3 "2001-02-03T05:58:43Z")

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I’m not looking for an answer that has to explain about gravity and inertia and orbits. I want to be able to show them. Eclipses, other planets, etc.

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**Author:** ![friedo](https://avatars.discourse-cdn.com/v4/letter/f/8edcca/32.png) [@friedo](https://boards.straightdope.com/u/friedo)\
**Post date:** [February 3, 2001, 6:51am UTC](https://boards.straightdope.com/t/earth-in-motion/52982/4 "2001-02-03T06:51:10Z")

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Well, one way is to look at seasons. The days get shorter in the winter because that hemisphere is angled away from the sun. The seasons are reversed in opposite hemisphered because of this. Without observation and math, you have to accept on faith that the earth does not wobble back and forth on its axis every year. But common sense suggests that things do not spin like this. (It so happens that the earth does wobble a little bit, but over thousands of years, and not enough to reverse the seasons.)

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**Author:** ![Robot\_Arm](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/robot_arm/32/18280_2.png) [@Robot\_Arm](https://boards.straightdope.com/u/Robot_Arm)\
**Post date:** [February 3, 2001, 7:09am UTC](https://boards.straightdope.com/t/earth-in-motion/52982/5 "2001-02-03T07:09:01Z")

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Chart the postition of Mars in the night sky from night to night. Sometimes it will appear to move backwards against the background of stars. The Earth-centered theory of the solar system tried to explain this with an intricate mechanism of wheels and gears, but it’s much simpler to assume it’s just that we’re overtaking Mars because of our smaller, faster orbit around the Sun.

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**Author:** ![RM\_Mentock](https://avatars.discourse-cdn.com/v4/letter/r/e274bd/32.png) [@RM\_Mentock](https://boards.straightdope.com/u/RM_Mentock)\
**Post date:** [February 3, 2001, 8:02am UTC](https://boards.straightdope.com/t/earth-in-motion/52982/6 "2001-02-03T08:02:41Z")

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If you are talking to a geocentrist, especially a fundamentalist, there is no way. For many reasons.

One interesting one is, you’d essentially have to prove Einstein wrong in order to do it. The general theory of relativity says that any reference frame is valid, which would include an earth-centered earth-fixed one. The laws of physics (GR) still work, and everything comes out the same. That is an extreme view though.