Is the Sun in our solar system moving or stationary?
When I was small, I read that Sun is fixed at the center of the solar system and that all the other planets rotate around it.
But later I heard that even the Sun is not fixed; it moves. Is this true?
Why had people previously thought that the Sun is fixed?
Is this correct planets in helix path or spring like path?
Fixed relative to what? Moving relative to what? It all depends on your frame of reference, and thus it is not meaningful to ask if the Sun is moving or not. Relative to the galactic centre, the Sun moves, but we most often use a heliocentric frame of reference in the solar system, and then the Sun is not moving.
Favorite APOD-Speeding Through the Universe: http://apod.nasa.gov/apod/ap960205.html "relative to the microwave background ... the Local Group moves at about 600 kilometers per second".
@Hohmannfan - no need to be complicated. It's perfectly clear the OP is simply asking, regarding internally to our solar system: "Does the Earth rotate around the sun, with the sun perfectly still in the middle?"
Hey Amruth. A good place to start is simply the **Earth and Moon**. You might think the moon goes "around the Earth": not true. They both circle around a common point in the middle (it's about one quarter of the way along from Earth) - imagine a person with a string one foot long for the Earth and three foot long for the Moon, spinning around. Similarly the sun wobbles a bit as the various large planets go around it. In grade school when they say "in the center" they just mean "roughly" in the center. It's not EXACTLY in the center; and it "wobbles". Simple!
Instead of editing to add a second question. If you have a new question, you should ask it as a separate question. "Does the sun move" and "is the solar system a helix" are different questions. You should also do some research before posting!
The Sun moves, even in the context of the solar system. Gravity of the planets (mostly Jupiter) pulls the Sun out of position with respect to the centre of gravity of the solar system. This wikipedia entry explains it in a lot more detail, and also explains that their common centre of gravity lies outside of the sun.
This wobbling of a star due to planets orbiting them is also one method of how we detect planets around other stars.
Assuming that the Sun is fixed within the context of the solar system is a fairly good approximation. You need accurate and long term observations to detect the wobble.