Meaning of gravity in an intuitive sense?

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Discussion Overview

The discussion revolves around the intuitive understanding of gravity, exploring its meaning and implications in both everyday scenarios and theoretical contexts. Participants engage with the concept of gravitational attraction between objects, including small everyday items like a pen and a pencil, and delve into both classical and modern interpretations of gravity.

Discussion Character

  • Exploratory
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant asks for an intuitive explanation of gravity, indicating a desire for a more accessible understanding of the concept.
  • Another participant defines gravity as the attractive force between two bodies with mass, noting its proportionality to mass and inverse relationship to distance.
  • A participant questions the existence of gravitational attraction between small objects like a pen and a pencil, seeking clarification on how such a force can be present.
  • One response acknowledges the gravitational attraction between small objects but suggests that it is too weak to be detected by common devices, emphasizing the need for two bodies to measure the interaction.
  • A participant introduces the idea of gravity causing a 'dent' in spacetime, using a rubber sheet analogy to illustrate how objects influence the motion of others in their vicinity.
  • Another participant references the Cavendish Experiment as a method to measure gravitational attraction between small objects, indicating that such experiments support the existence of gravity even at small scales.
  • One participant recalls an experiment demonstrating gravitational effects, but notes that electrostatic forces overshadowed the gravitational effects, highlighting the complexities in observing gravity in practical scenarios.

Areas of Agreement / Disagreement

Participants express varying degrees of understanding and interpretation of gravity, with some agreeing on its existence and measurement methods while others remain uncertain about its implications in everyday contexts. The discussion does not reach a consensus on the intuitive understanding of gravity.

Contextual Notes

The discussion reflects limitations in the participants' understanding of gravitational effects at small scales and the challenges in isolating gravitational forces from other influences, such as electrostatic forces.

jrm2002
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meaning of "gravity" in an intuitive sense?

A very very general question:
Can anyone explain the meaning of "gravity" in an intuitive sense?
 
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Hi jrm. Could you elaborate upon your question, please? Essentially, gravity is the attractive force between any two bodies with mass. It is proportional to the amount of mass, and inversely proportional to the square of the distance between the centres of the objects.
 
Thanks Danger:
You said " gravity is the attractive force between any two bodies with mass."
Let us say the bodies are say a pen and a pencil lying on the table.How will there be a force of attraction between them?
Plz help!
 
I don't believe that there are any devices on the planet sensitive enough to detect the gravitational attraction between a pen and a pencil, but it's there.
Only one body is required to produce a gravity field, but examples are always given with at least 2 because the interaction between them is the only way to directly measure it. Also, the bodies are usually assumed to be spherical for simplicity. A lot of math would be involved in trying to figure out the shape of a field around something pen-shaped.
The simplest way to think of it, although it's not quite accurate, is that the object causes a 'dent' in spacetime. Something that comes along, including a light beam, alters it's motion to continue in what it thinks is a straight line. Think of placing a ball bearing on a rubber sheet, then rolling a marble toward it. The marble has its own little 'dent' that travels along with it, but it's insignificant compared to the one made by the bearing. If both masses are the same, the two dents interact in a different manner than just one falling into the other.
I'm afraid that I'm pretty much at the limit of how much I can explain it. Feel free to ask if you have more specific questions. I might not be able to answer them, but others on site can.
 
jrm2002 said:
Thanks Danger:
You said " gravity is the attractive force between any two bodies with mass."
Let us say the bodies are say a pen and a pencil lying on the table.How will there be a force of attraction between them?
Plz help!

Using a torsion balance, we can directly measure the attractive force (tiny as it is) between lead balls.

Google for "The Cavendish Experiment", one good link is at

http://physics.usask.ca/~kolb/p404/cavendish/

As to the mechanism of "how", one can take several views of various degrees of sophistication, but I don't want to get into a long explanation of GR if you are (for example) looking for a classical Newtonian explanation of gravity.

I will say that experiments such as the Cavendish experiment confirm that gravity exists in the laboratory even between small objects. The measured values of gravity from such terrestrial experiments are also a good fit with astronomical observations.
 
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I remember seeing an utterly absurdly simple display of two objects gravitational effects. It was two balls maybe a foot apart on what i assume is a very very low friction rotating pipe system. The problem was that it had just rained so the electrostatic effects were far too great and overshadowed the gravitational effects. Does anyone know what I'm talking about? It looked like someone had just made it with some pvc piping.
 

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