Gravity & Universe: Is Everything Falling?

  • Thread starter Thread starter cottonkat5
  • Start date Start date
  • Tags Tags
    Falling Universe
AI Thread Summary
The discussion explores the concept of gravity and whether all celestial bodies in the universe are falling at the same rate. It clarifies that the universe is expanding and that gravity operates differently across regions, making the idea of a constant gravitational field ineffective. The notion of "free fall" is emphasized, with all orbiting bodies, including Earth, in a state of free fall relative to larger masses like the Sun. The conversation also touches on the relativity of motion, stating that if all objects moved at the same speed, it would be perceived as zero velocity. Overall, the complexities of gravity and motion in the universe are highlighted, debunking the idea of uniform falling.
cottonkat5
Messages
2
Reaction score
0
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.
 
Space news on Phys.org
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.
 
https://en.wikipedia.org/wiki/Recombination_(cosmology) Was a matter density right after the decoupling low enough to consider the vacuum as the actual vacuum, and not the medium through which the light propagates with the speed lower than ##({\epsilon_0\mu_0})^{-1/2}##? I'm asking this in context of the calculation of the observable universe radius, where the time integral of the inverse of the scale factor is multiplied by the constant speed of light ##c##.
Why was the Hubble constant assumed to be decreasing and slowing down (decelerating) the expansion rate of the Universe, while at the same time Dark Energy is presumably accelerating the expansion? And to thicken the plot. recent news from NASA indicates that the Hubble constant is now increasing. Can you clarify this enigma? Also., if the Hubble constant eventually decreases, why is there a lower limit to its value?

Similar threads

Back
Top