Gravity & Universe: Is Everything Falling?

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    Falling Universe
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Discussion Overview

The discussion revolves around the nature of gravity in the universe and whether all celestial bodies are falling at the same rate. Participants explore concepts related to free fall, the expansion of the universe, and the implications of gravity on the motion of celestial bodies.

Discussion Character

  • Exploratory
  • Debate/contested
  • Conceptual clarification

Main Points Raised

  • One participant questions if there is a uniform gravitational force throughout the universe causing all celestial bodies to fall at the same rate.
  • Another participant asserts that the universe is expanding and that this expansion is accelerating, which contradicts the idea of uniform gravitational effects.
  • A different viewpoint suggests that not everything in the universe is in free fall, indicating a lack of consensus on this concept.
  • One participant proposes a model where celestial bodies are in free fall relative to their locations, suggesting that larger objects influence the motion of smaller ones without a defined center to the universe.
  • Another participant clarifies that the concept of gravity is tied to interactions within the universe and that a constant gravitational field would have negligible effects.
  • It is noted that in relativity, there is no absolute velocity, and thus if all objects were moving at the same relative velocity, it would be considered 'zero velocity'.
  • One participant agrees that all bodies in orbit are in free fall, emphasizing the role of gravity in maintaining orbits while also noting the importance of relative motion.

Areas of Agreement / Disagreement

Participants express differing views on the nature of gravity and free fall in the universe, with no clear consensus reached on whether all celestial bodies are falling at the same rate or the implications of gravitational forces.

Contextual Notes

Some claims depend on interpretations of gravitational effects and the nature of motion in relativity, which remain unresolved in the discussion.

cottonkat5
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I'm sure this will sound like quite a childish question, but Is it possible that there are high amounts of gravity throughout the whole universe (probably not the right wording), and that all celestial bodies are falling in "nothing" at the same rate of speed.
 
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The universe is expanding and the expansion is accelerating, opposite of the effect that you are asking about.
 
There is no reason to believe that everything in the universe is in free fall.
 
After reading Koestler's The Sleepwalkers, and not being a mathematician, the construct that seemed to best fill the requirements of orbiting bodies and gravity was a universe in which everything was in free fall relative to its location. That is to say that our star, the Sun, is in free fall as part of the larger galaxy, taking along with it Earth and the other planets. As there is no center to the universe, it would seem silly to say falling "down," rather everything is in free fall regardless of direction. As larger objects fall, they draw in smaller objects. I won't go on--although I could.
 
cottonkat5 said:
I'm sure this will sound like quite a childish question, but Is it possible that there are high amounts of gravity throughout the whole universe (probably not the right wording), and that all celestial bodies are falling in "nothing" at the same rate of speed.

There seem to be two aspects of your question:
1) 'free fall' / 'gravity' --- this doesn't make sense. The universe is effectively defined as the region of spacetime that is interacting... thus anything causing gravity is necessarily 'in' the universe. Additionally, what's almost always important is the difference in gravity between regions---thus if there were a 'constant' gravitational field the entire universe 'felt' --- it wouldn't have any effect (for the most part).

2) It sounds like you're asking if ever object in the universe is moving in some direction, at the same speed. In relativity there is no concept of absolute velocity (speed). Therefore if everything were moving at the same relative velocity, we would just call that 'zero velocity'.
 
Agreed. All bodies in orbit are in free fall. The Earth falls around the sun, but, is moving too fast to fall into it [which is good]. A satellite launched into orbit free falls around the earth, but, is going too fast to crash into it. All courtesy of gravity. The only direction gravity knows is towards the largest nearby center of mass.
 

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