# What are the forces behind the orbit of the Earth around the Sun?

Does the gravity of the sun alone affect the orbit of the earth around the sun?

Look at the image below,(Image is not to scale),

Is it that when earth is going from position 1 to position 2, it speeds up due to the pull of the sun, goes around the sun and when going from points 2 to 1 again slows down due to the gravity of the sun? Does the velocity of the earth around the sun vary depending upon whether it is going away or nearing the sun?

• "Does the gravity of the sun alone affect the orbit of the earth around the sun?" As a practical matter, yes. But, in principle, everything in the universe affects it, albeit only to an imperceptible degree. Other sources are negligible relative to the Sun because the Sun accounts for 99.85% of the mass in the solar system. The eight non-dwarf planets account for about 0.135% of the mass in the solar system (more than two-thirds of which is in the planet Jupiter which is also more distant from Earth than the Sun by a factor of two to four). The mass of the Sun is about 333,000 times Earth's. – ohwilleke May 15 '19 at 6:26
• That picture is kind of wonky, by the way. If it's meant to illustrate a highly elliptical orbit (viewed from straight above the orbital plane), then the Sun is way too far from the point labelled 2 (which should be the closest point of the orbit to the Sun). If it's instead meant to be a semi-realistic depiction of the Earth's (almost circular) orbit, but viewed at an angle, then the Sun is way too close to point 2 instead. – Ilmari Karonen May 15 '19 at 11:24
• "Does the velocity of the earth around the sun vary depending upon whether it is going away or nearing the sun?" The speed just depends on the distance between them. See Kepler's 3rd law. en.wikipedia.org/wiki/Kepler%27s_laws_of_planetary_motion – PM 2Ring May 15 '19 at 11:45
• Universe, Space, Solar system and everything are total lie. Four questions to everyone who beLIEve: 1. If the sun can pull neptune, then why it can't pull our moon which is much closer when it's between earth and the sun? 2. If earth & atmosphere spin 1000mph eastwardly then flights cannot reach westward destination, but it can, WHY? 3. If earth goes around the sun then for 6 months we should see completely other stars on other side but 12 months same stars, WHY? 4. If the sun is behind earth at night then WHY mercury and venus show up in night sky? – Ĭsααc tիε βöss May 15 '19 at 12:29
• @Ĭsααctիεβöss What are you hoping to accomplish here? There are tons of great resources (many freely available) on basic physics and orbital mechanics, but since you're ignoring them, I don't think you've come here to be informed, just to argue. – Josh Eller May 15 '19 at 13:20

Yes, it does. Your description is correct. Other bodies than the Sun also pull in Earth with their respective gravities, though, but they are effectively negligible.

The elliptic effect is not as pronounced as you illustrate here, though. Earth's orbit is close to circular.

• When closest, the Sun-Earth distance is around 147 million km.
• When farthest, around 152 million km.

(This image is still not circular enough; see comments. The actual drawn orbit would most likely be impossible to distinguish from a perfectly circular orbit.)

That corresponds to orbital speeds of

• ~$$30 \;\mathrm{km/s}$$ when fastest and
• ~$$29.3 \;\mathrm{km/s}$$ when slowest

(according to Ask an Astronomer; I didn't plug in the numbers myself, but that shouldn't be a big deal to do to verify this).

• Actually, even your picture, although coming from Encyclopedia Britannica, is too much elliptic. A real drawing of the orbit of the Earth is hardly distinguishable from a an exact circle. – GiorgioP May 15 '19 at 6:59
• The position of farthest distance is about 3.25% farther away than the closest. – infinitezero May 15 '19 at 8:08
• Also, the Sun and the Earth are both way too large in that picture. – probably_someone May 15 '19 at 9:01
• Also, there are no arrows and dotted lines in space. Also the Sun isn't really labeled and there are way too many Earths in the picture. Let's just accept that it's a not-to-scale illustration instead of a photograph. – Moyli May 15 '19 at 9:05
• Thanks, all, for the corrective comments; I have added an edit to clarify the inaccuracy of the image. And thanks @Moyli for having my back 💪 – Steeven May 15 '19 at 9:17

Just speaking generically, if you have a mass orbiting a star, then yes, the velocity of the object increases when it is closer to the host star than when the radius of its orbit is farther away. I imagine the picture is just a generic example and exaggerating an ellipse. It has to do with conservation of angular momentum.

It works the same for all masses in a system. So, comets, moons, planets, whatever... they all do it. 😉