# Gravity

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 386024.  Sun Jul 27, 2008 9:11 am Hello All Before we start, it is a complete and utter myth that Newton sat under a tree and an apple fell on his head, and discovered Gravity. This is one of the fundamental forces of nature. Planets and Stars such as the Earth and Sun alter the space/time around it, and things like us, the atmosphere we breathe and the moon are affected by it. Without it we would not exist. Must give respect to it here.

 386051.  Sun Jul 27, 2008 11:14 am The myth of the falling apple was, I believe, perpetrated by Isaac Newton himself; being somewhat of a theologian, he likened his apotheosis in discovering the law of gravity, to the apotheosis suffered by Adam after his fall, which was caused partly by an apple. He may also have had the enlightenment of the Buddha in mind, which took place under a tree. Complicated chap, Newton.

 386246.  Sun Jul 27, 2008 4:36 pm GR post Gravity and Weight thread. A bit about gravitons. Spinning earth. Gravity thread. Why gravity isn't a force in GR. Sorry to post to my threads throughout, I don't mean to be self important. I figured I'd been involved in most of the threads on this topic, so just searched for Gravity and Davini994.

 386460.  Mon Jul 28, 2008 5:37 am I still find it hard to get round the idea of 'zero gravity' in space actually a state of constant falling.

 390348.  Wed Aug 06, 2008 9:56 pm In fact, there are very few places where you would actually find "zero gravity" in space, since gravity pervades the whole universe. Importantly, in Earth orbit, you're not in *zero* gravity, you're in microgravity. In other words, you are always moving, although incredibly slightly, towards the nearest heavy object. Arguably, you can never be in zero gravity because you have your own gravity field which is always with you. The places with the most interesting gravity are the Lagrange points, where the forces of gravity between two objects kind of cancel out, so they sort of act like gravitational attractors, despite having no mass. (Although, since they do attract other objects, they tend to fill up with junk.) I should stop prattling on now, I think I've confused myself.

390707.  Thu Aug 07, 2008 3:22 pm

 Anome wrote: In fact, there are very few places where you would actually find "zero gravity" in space, since gravity pervades the whole universe. Importantly, in Earth orbit, you're not in *zero* gravity, you're in microgravity. In other words, you are always moving, although incredibly slightly, towards the nearest heavy object. Arguably, you can never be in zero gravity because you have your own gravity field which is always with you. The places with the most interesting gravity are the Lagrange points, where the forces of gravity between two objects kind of cancel out, so they sort of act like gravitational attractors, despite having no mass. (Although, since they do attract other objects, they tend to fill up with junk.) I should stop prattling on now, I think I've confused myself.

You're good.

 442531.  Thu Nov 20, 2008 8:58 am Newton discovered gravity? It's not like it wasn't apparent beforehand and didn't affect our daily lives. Newton identified a force and described it. He decided to call the effect "gravity". Something QI about gravity - I think it's one of the few forces that doesn't have a known negative counterpart.

442539.  Thu Nov 20, 2008 9:13 am

 Posital wrote: Newton identified a force and described it. He decided to call the effect "gravity".

Beep.

The use of the word "gravity" to describe, in a scientific manner, the force that give objects weight stems from 1641. Since Newton wasn't born until 1643 it seems unlikely that he was the one who chose that word.

442561.  Thu Nov 20, 2008 9:50 am

From before then, even. Francis Bacon (amongst others) used the word in the 1620s.

 F. Bacon in 1626 wrote: Similitude of Substance will cause Attraction, where the Body is wholly freed from the Motion of Grauity.

442572.  Thu Nov 20, 2008 10:24 am

costean wrote:
From before then, even. Francis Bacon (amongst others) used the word in the 1620s.

 F. Bacon in 1626 wrote: Similitude of Substance will cause Attraction, where the Body is wholly freed from the Motion of Grauity.

I'm not sure about that. Though I stand to be corrected I think that Bacon was referring to the weight of the body rather than the force that caused the weight, I.e. Bacon was referring to something inherent in the body which caused it to fall to Earth whilst later the term transferred to an outside force which caused the body to fall. Using the word "gravity" to refer to the weight of an object goes back to about 1500.

442598.  Thu Nov 20, 2008 11:28 am

No, I'm not entirely sure what he meant exactly, either. I'm quoting the OED here and they say:
 Quote: Gravity [Etym] ... The primary physical sense of the Lat. word came into Eng. first in the 17th c. In physical senses. The quality of having weight, ponderability; the tendency to downward motion, regarded in ancient physics as a property inherent in certain bodies (opposed to levity, or the upward tendency ascribed, e.g., to the element of fire). Obs.

Then there are a number of citations of which Bacon's was one.

In the modern sense which we would take to mean as 'gravity', it is later defined as:
 Quote: The attractive force by which all bodies tend to move towards the centre of the earth; the degree of intensity with which a body in any given position is affected by this force, measured by the amount of acceleration produced. Also often in wider sense, the degree of intensity with which one body is affected by the attraction of gravitation exercised by another body. absol. A force equal to the accelerating force of gravity; abbrev. g.

More citations from 1692 (although, obviously, Newton had defined his Law of Universal Gravitation before then).

So, a certain degree of mootishness all round.

 442624.  Thu Nov 20, 2008 12:24 pm One has to be very careful, when reading old texts, to understand that the meanings of a particular word which might be clear to the reader might have had quite a different meaning, or possibly (what is sometimes harder to understand) a subtly different meaning to the person who wrote the text.

 522903.  Mon Mar 16, 2009 2:41 pm

 522976.  Mon Mar 16, 2009 4:38 pm Would it be better to say that Newton discovered the LAWS of gravity ?

 522981.  Mon Mar 16, 2009 4:42 pm Buried under an apple tree?

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