Well I'll be. I thought the we were talking about rocks. And God forbid a meteor shower muck up the equation. :P
This post was edited by Benedict Arnold at December 8, 2018 7:16 AM MST
Mercury, Venus, Earth and Mars are called "rocky" or "terrestrial" planets. They are similar to Earth in composition. Heat from the Sun evaporated lightweight elements like hydrogen and helium into interplanetary space. Mostly rock and metal was left in this zone and clumped together to form the inner rocky planets.
I am still trying to compose a serious answer. The trouble is that your question does not suggest any particular answer, serious or otherwise. Asking "Why" presumes that there is a reason, and that presumes that the situation is inflicted upon us, and that implies that some intelligent being has an objective to be accomplished. "That's the way the mop flops" is not an adequate response.
Bottom line: change your question to something else, and then we can tell you "That's the way the mop flops." Or if you specify a non-serious answer then we can tell you "That's the way the Mercedes bends."
Good point! The question as written is ambiguous: it is not clear if it is querying the Earth's position in the Solar System, or the etymology of the phrase.
The first is a matter of astro-physics. The second is a matter of poetic word-play!