# B Why the Earth orbits around the Sun

1. Apr 14, 2016

### kenny1999

As far as I know, the Earth orbits around the Sun because of the centripetal force
, and as far as I know, friction and gravitation from other planets should affect the circular motion of the earth and so the path of the earth should not be necessary that perfect.

In addition, there must be small particles or dust in the space so that there must
be friction which should also affect the circular motion of the Earth

Am I right or wrong??

2. Apr 14, 2016

### mathman

The earth's orbit is an ellipse. The orbit is perturbed by other planets gravity. Dust, etc. has a much smaller effect.

3. Apr 14, 2016

### kenny1999

But we have some planets e.g. Jupitar that are much bigger than our Earth and not really so far away. Why don't they affect our orbit???????

4. Apr 14, 2016

### Staff: Mentor

Jupiter is much farther away than the Sun, and just has 1/1000 the mass. It perturbs the orbit in a measurable way, but the effect is very small. More than 99.8% of the mass of the solar system is in the sun.

5. Apr 14, 2016

### phinds

Just to be sure you understand the full technical detail, it is not quite correct to say that the Earth orbits around the sun but rather that that both orbit around the center of mass of the two bodies (which is deep inside the sun). In day to day terms, we do say that the Earth orbits the sun.

6. Apr 15, 2016

### Jim60

Just out of interest, how far from the nucleus of the Sun is the Solar System Barycentre right now?

7. Apr 15, 2016

### Staff: Mentor

Close to the surface of sun, it will be outside the sun starting beginning of 2017. https://qph.is.quoracdn.net/main-qimg-118a1175c48f6ff2afd0183dd0040dd4?convert_to_webp=true [Broken] (2016 is at the right side of the sun, the radius of the sun is about 700,000 km).

The difference is mainly driven by the position of Jupiter and Saturn, Earth has a negligible effect (~500 km).

Last edited by a moderator: May 7, 2017
8. Apr 15, 2016

### newjerseyrunner

About 280 miles is the effect of Earth, like mfb said, the bigger planets have a much large effect: http://www.applet-magic.com/centermass.htm

9. Apr 15, 2016

### tony873004

Any answer assumes there are no other planets orbiting beyond Neptune. If Planet 9 and or other large objects exist beyond Neptune, this will shift the ss barycenter.

Assuming they don't exist, here's a simulation you can run to show you how the solar system barycenter changes with time. You can delete individual planets to see how much influence they had.
http://orbitsimulator.com/gravitySimulatorCloud/simulations/ssbarycenter.html

10. Apr 15, 2016

### Jim60

Could play with that simulator for hours, maybe I’ll have some time tomorrow.