MadSci Network: Astronomy

Re: I was wondering what would happen if the sun stopped spinning?

Date: Sun Jun 4 00:01:26 2000
Posted By: Bryan Mendez, Grad student, Astronomy and Astrophysics, University of California at Berkeley
Area of science: Astronomy
ID: 959649777.As

Hi Tim,
I'm assuming that you are referring to the passage in the Christian Bible (The Book of Joshua, Chapter 10, Verses 12-14) where Joshua commands the Sun and Moon to stop their motions through the sky so that daylight might last longer and the Israelite army could defeat the Amorites at Gibeon.

In the passage it says that the Sun held its position (along with the Moon) and did not set for for a full day extra. Now, the passage reads as if the Sun were orbiting the Earth; "Sun, be motionless over Gibeon" commanded Joshua. However, the daily motion of the Sun actually is the result of the Earth rotating on its axis once per day, and the Earth orbits the Sun over the course of a year.

So the only way for the Sun to stop moving through the sky would be for Earth to stop spinning on its axis (there would still be a yearly motion of the Sun, but this would stop the daily motion). If this were to magically happen somehow several things would change. Firstly, the angular momentum that Earth had due to its spinning would have to go somewhere. It would likely be transfered to the Moon's orbit which would make the Moon move farther away from Earth. This would make the Moon appear smaller in the sky and cause tides on Earth to be less extreme (the Moon's gravity causes the tides, and gravity's strength gets weaker with increasing distance). The weather on Earth would change drastically as half the Earth would plunged into darkness for 6 months of the year and the other half would have never ending sunlight for 6 months. The part in darkness would grow very cold, and the part in light very hot. [Another important weather effect is that one has to stop both the Earth itself and its atmosphere. As the atmosphere is also rotating, if it isn't stopped, there would be super hurricane-force winds. Moderator]

Because the Earth still orbits the Sun in this scenario, the Sun would still appear to go around the sky once per year. It would rise and set only once every year. If you wanted to magically stop that motion as well, again you would need to transfer the angular momentum of Earth's orbit to somewhere else. Doing so would likely cause a shift in the orbits of the outer planets. Now, with Earth having no motion around the Sun, it would begin to fall straight toward the Sun. In a few months it would crash into the Sun: end of Earth. The Earth is always falling toward the Sun (its gravity pulls us toward it). But it also has motion around the Sun which balances the pull and keeps us going around in a roughly circular orbit.

Hope that answers your question.
-Bryan Mendez (

[There are a few other notable items regarding this passage. If you read the first chapter of Genesis, it is clear that the ancient Hebrews did not consider the Sun and the Moon to be separate bodies, as we know them today. Most often, the Sun and Moon are described simply as "lights in (or on) the sky." In fact, a really good translation of Genesis will note that the word for "sky" is firmament, literally a thin metal sheet which also holds back the "waters of the heavens." In other words, the Hebrews considered the Sun and Moon simply to be lights moving along the surface of the firmament. It's also worth pointing out that an extra day is not mentioned by any other civilization of the time, most notably the Chinese. The Chinese were excellent record keepers; among other things, their records are often used to try to figure out what the star of Bethlehem was. To the best of my knowledge, they make no mention of the Sun stopping in the sky.

The topic of the Earth's spin is a popular one on MadSci. You might also want to take a look at these questions:

Many more can probably be found through the Mad Scientist Search Network. Moderator]

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