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This idea keeps on appearing in my mind, once in a million years the Sun's gravity will pull Earth near and eliminate every living in the earth due to the increased heat, and in another million years it pushes Earth far away and creates a frozen age due to lack of heat?

My Theory 1 I know that earth orbit around the sun is because of sun gravity, but gravity is randomly based on unknow mechanic, it might strong today, and might be weak after few years.

If I say that Ice age form is because the earth slowly move away from the sun million years ago(unexplainable weak sun gravity), lack of sunlight to the earth make earth cold, And now the ice at north pole is melting, it means that we might actually getting closer to the sun. And the event will keep on repeat each hundred million years, so we in the middle of extinction process, but that will take hundred million years to reach a level where the sun ray can destroy everything I know is kinda bluff without any proof, but this might be one of the possibility

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    $\begingroup$ A major problem with this premise: you say gravity is randomly based on an unknown premise. It is actually known to an amazing degree of accuracy. $\endgroup$ – Rory Alsop May 6 '14 at 6:58
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    $\begingroup$ gravity is randomly based on unknow mechanic is among the worse things ever you can say about science... $\endgroup$ – Py-ser May 7 '14 at 5:03
  • $\begingroup$ I have migrated this question from our Astronomy site. There has been some discussion in the Earth Science chat as to the difficulty of this question, but I have decided to go ahead and migrate it and let the Earth Science community round it out (or even eventually close it if need be), so that the community gets the opportunity to handle this type of question and decide what to do with it. $\endgroup$ – called2voyage May 8 '14 at 12:20
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    $\begingroup$ It sounds to me like the scenario being proposed is a bit like Jupiter's Grand Tack during the early-ish solar system. If considered helpful I can write up an answer about why that scenario isn't really relevant to recent Earth? $\endgroup$ – kaberett May 8 '14 at 12:52
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Look at Earth's orbit around the Sun. The orbit is an ellipse, but Earth never gets close enough for the Sun to cause any mass extinction. The Earth orbits the Sun every year, and because the orbit is stable, on average we are about 8 light minutes from the Sun.

One way the Earth's orbit might change is if the Sun has a sister companion, that is, a binary star; thus far no evidence suggests the existence of another star in our solar system, but a binary star could alter the orbit of a planet. You could become an Astronomer and try to prove your hypothesis and it would not be a wasted journey.

I see you edited your question. Now you have included some aspects about gravity which contradict current knowledge of gravity. I highly recommend reading about gravity. To start you off I will share with you a known fact about gravity. The Earth exerts the same gravitational force on the Sun that the Sun exerts on the Earth. $$F_1=F_2 = G *m_1*m_2/r^2$$

That is, both these objects attract each other with the same amount of force. Moreover, gravity is related to an objects mass, so unless the Sun or the Earth lost mass there would be no change.

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    $\begingroup$ Nothing more than a footnote: "...unless the Sun or the Earth lost mass there would be no change [in the gravitational force between Earth and Sun]" — well, you could vary G or r. G is probably constant, but r does vary, e.g. in Milankovitch cycles, which certainly affect life on earth, and the orbital expansion @Keith_Thompson mentions. $\endgroup$ – kwinkunks May 8 '14 at 12:29
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There have been numerous mass extinctions in Earth's history. The most famous one took place about 66 million years ago; see the linked article for others. Different events likely had different causes.

You suggest that the Sun's gravity periodically pulls the Earth closer, and then pushes it away. As far as I know, there is no evidence that this could have happened. The Sun's mass slowly diminishes over billions of years, due to direct loss of mass via solar wind and conversion of mass to energy; this should cause the Earth's orbit to expand very slowly. There is no known mechanism by which a change in the Sun's mass could draw the Earth closer and then "push" it away -- nor is there any need to postulate such a mechanism, since there are no observed phenomena that need it as an explanation.

Do you have some specific reason to think your idea is plausible?

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