Gravity is not a force
The various equations surrounding force abound. To say that gravity is a force requires one to verify that gravity can be substituted for a force in all the equations. The problem is, you can't. It simply doesn't hold, despite Wikipedia's article on force which contends otherwise.
It boils down to this (ie, the following statements, as stated, are true):
1. All bodies in non-gravitational free-fall which experience a force experience a correlating acceleration which is equal to the ratio between the force and the mass.
That acceleration can be measured by an on-board accelerometer.
2. All bodies in free-fall experiencing a change in their velocity relative to a neighboring massive object (such as the Earth) appear to be accelerating in a direction parallel to the line between the body's center of mass and the object's center of mass.
That acceleration can NOT be measured by an on-board accelerometer.
The point is that regardless of the differences between gravity and traditional forces, there is a difference. It's that difference which sets gravity apart from a force.
Gravity is not a force. It's a warping of the space-time in which all affected matter and energy exist, as both matter and energy are affected by gravity.
Consider Newton's First Law: "A particle will stay at rest or continue at a constant velocity unless acted upon by an external unbalanced force." Thus, a planet will continue in a straight line unless acted upon by a force.
But is gravity really a force? No. Gravity simply warps space-time in the solar system such that a planet's orbit really is a straight line. All on-board accelerometers can measure any force enacted upon a free-falling body. No on-board accelerometer can measure the effect of gravity upon a free-falling body. Thus, gravity is not a force. —Preceding unsigned comment added by 220.127.116.11 (talk) 19:27, 27 July 2008 (UTC)
- This page is for discussing the quality of the article, and not the topics covered by the article itself. Please raise your issue on the talk page of the Force article. J.T Pearson (talk) 13:17, 28 July 2008 (UTC)
- I was mystified by the preceding sentence until I tried editing this section myself. My guess is that User talk:18.104.22.168 had no idea he (or she) was editing Talk:Force/GA1 when he clicked on the edit field of your transcluded section in Talk:Force to append his new section. It is a bug of transclusion that it does not at least warn the editor of a new section immediately following a transcluded section (better would be not to be taken to the transcluded version in the first place). I fell into the same trap, and only noticed it when previewing my edit. I'm sure he'd have no objection if you moved his section (along with my reply below but without this paragraph or yours immediately above) from Talk:Force/GA1 to Talk:Force.
- In response to User talk:22.214.171.124, gravity as ordinarily understood is manifested in curved space-time as acceleration (gravitational force is the time-derivative of momentum), as the article makes clear. The reason you don't fall through the floor is that the downward force of gravity, whether modeled classically in terms of gravitational potential or relativistically in terms of acceleration in curved space-time, is exactly balanced by the upward electromagnetic force holding apart your atoms and those of the floor, per Newton's Third Law of Motion. Gravity, EM, and the nuclear interactions are the fundamental forces of physics. Omitting gravity from this list is the kind of novelty outlawed by WP:OR. --Vaughan Pratt (talk) 20:40, 27 February 2009 (UTC)