# Relative effects of forces

Excuse me for my ignorance but I really couldn't find a solution. According to Einstein, every happening is possible to describe by both of interacted objects.

1. Is there any other way to describe the Big bang than the one that describes the rapid expansion of the universe?
2. I just read that Kepler's laws were proof that geocentrism is not true. But according to Einstein, gravity is reciprocal effect of two curvature of space. It is therefore relative, if we live in a heliocentric or geocentric system?

Thank you.

• Can you expand on according to Einstein, gravity is reciprocal effect of two curvature of space as I cannot see what you mean by this. – John Rennie Apr 22 '14 at 11:39
• "It is therefore relative, if we live in a heliocentric or geocentric system?" No. Neither the Earth nor the Sun represent an inertial frame for describing the orbits. That said the barycenter frame (which is inertial in the two body problem) very nearly coincides with the Sun's frame. And while you can work in non-inertial frames, they are not frame in which the law of nature has simple form. – dmckee Apr 22 '14 at 13:11
• 1. The back temperature of the Universe. – Poomrokc The 3years Apr 22 '14 at 13:41
• @John Rennie I mean this: goo.gl/FjMqC3 We can't describe gravity as Newton because if you observe two apples on the opposite side of the Earth you can't just spread Earth and say that is relative, if apples fall on Earth or Earth fall on apples - so we need curved universe to say that every happening is possible to describe by both of interacted objects. But in Einstein's universe gravity IS reciprocal - you can say: "Apples are falling to Earth" and also "The Earth is falling to apples" - because gravity isn't just straightforward force. Thank you very much. – foggy Apr 23 '14 at 17:54