Every 27 days, the Sun spins on its axis. Because the Sun is a gas and plasma ball, it does not have to revolve as tightly as solid planets and moons. In reality, the equatorial areas of the Sun spin quicker (in around 24 days) than the polar regions (which rotate once every more than 30 days). But this difference is so small that it is impossible to detect with current technology.
The rotation of the Sun was one of the major controversies in solar physics for many years. Early measurements by Humboldt and others showed that the rotation period of the Sun's equator was about 25 days, much shorter than the nearly 30 days that had been assumed by astronomers. But these observations were difficult to confirm or refute because they could not be repeated at other locations on Earth. The first space-based measurement of the Sun's rotation was made by NASA's Solar Maximum Mission (SMM), which discovered that the true equatorial rotation rate of the Sun is in fact 27 days.
Since then, other satellites have measured the Sun's rotation from space, and all results show that the Sun rotates at approximately the same rate at both its poles and its equator. This means that there is no significant difference between the speed of light electrons moving toward the north pole and those moving toward the south pole; they are all orbiting the Sun at exactly the same rate.
The mobility of sunspots was used to detect this rotation. Because the Sun's rotation axis is 7.25 degrees skewed from the axis of the Earth's orbit, we see more of the Sun's north pole in September and more of its south pole in March. This is why our seasons are not exactly equal distance around the planet: It takes the Earth a little over 24 hours to complete one rotation, but because it takes the Sun a bit less than 25 days to go through all four seasons, the two orbits don't align perfectly.
How do you prove that the Sun rotates? If you look at solar eclipses, you can see that the Moon stops out from under the Sun as seen from everywhere on Earth. Because the Moon doesn't move, this means that part of the Sun must be moving toward us and part of it moving away from us. Using telescopes, astronomers were able to see evidence of dark spots that appeared and disappeared on the Sun's surface during a total eclipse. They knew then that the Sun was spinning fast enough to have these features come and go quickly enough to explain how a shadow could be cast so accurately across such a large area of Earth.
What happens if the Sun does not spin? In general, anything that spins will have some kind of axis about which it rotates. Without something to rotate around, there would be no way for objects to change position relative to each other or remain in place.
The Earth circles (or rotates) around the sun. The sun rotates, but not at the same pace throughout its whole surface. Sunspot motions show that the sun revolves once every 27 days near its equator but only once every 31 days at its poles. These two different periods result in four seasons: winter at the poles and summer at the equators.
As the sun travels across the sky each day, it emits light from all parts of itself. This light travels to all parts of the earth, giving us a daily sunrise and sunset. The earth also rotates once on its axis during each day, producing the planet's curve shape. It is this rotating motion that gives us weather - clouds form where it is cold out and snow falls where there is precipitation. Rotation is responsible for the rise and fall of tides and the movement of wind waves.
These two processes together produce some amazing effects upon our world. For example: sunlight is what makes plants grow, so without it there would be no life on earth. The sun goes through cycles of activity and rest just like humans do, so there are times when it is more or less visible from earth. During a total solar eclipse people can see the moon block out the sun, although actually only part of the sun is blocked out. A coronal mass ejection is a huge explosion of particles ejected from the sun that can affect satellites and electronics on earth.
When most people look at the sun in the morning, they have no notion that it is revolving as the Earth and other planets orbit around it. People observe the shift between night and day when the Earth revolves. That means the Earth takes 24 hours to spin on its own axis. But because the Sun takes about 25,920 years to complete one revolution around the center of our galaxy, the position of the Sun changes relative to the stars throughout a person's lifetime.
The average distance from the Earth to the Sun is approximately 150 million kilometers (93 million miles). So if the Sun was a ball bearing spinning at 1,000 revolutions per minute, it would be traveling around the Earth in less than a second. But because of its mass, the Sun actually rotates more slowly than this - it takes about 250 days for the Sun to rotate once around its axis.
As a result, during a single day on Earth, the direction that it is light out varies since the Sun appears to move across the sky. If you were to watch the Sun every day throughout the year, you would see that it rises some mornings east and others west, never remaining still.
This is why plants need sunlight to live; they use the Sun's energy to make sugar which feeds all the animals on Earth. Without this work done by the plants, none of us would be alive today!