Expanding Universe (an interestin mind experiment)

AI Thread Summary
The discussion explores the concept of measuring the universe's expansion based on relativity, suggesting that an observer's location can influence their perception of galaxies either expanding or contracting. Using a metaphor of a yellow ball of play dough with colored balls representing galaxies, it illustrates how compression could lead to different observations depending on proximity to a central point. However, participants note that observations indicate a homogeneous and isotropic universe, making the idea of a squeezing mechanism unlikely. They also compare the scenario to a raisin muffin, emphasizing that all observers would perceive cosmological expansion due to the finite speed of light. Ultimately, the conversation highlights the complexities of understanding universal expansion and the challenges in explaining certain astronomical phenomena.
pfontec
Messages
3
Reaction score
0
Try thinking about measuring the expansion of the universe based on relativity. That is to say that depending on where you are located in the universe you might measure expansion or you might measure contraction!
Think about this.
The observer is placed anywhere inside of a giant ball of yellow "play dough". throughout the inside of the yellow ball are many little balls of different colored "play dough" representing galaxies.
Now something starts to squeeze the yellow ball.
Now depending on where the observer is located. He will percieve the colored "play dough" (the galaxies) expanding or he we percieve the galaxies contracting.
Can it be that our universe is being sqeezed by other dimensions (other universes?

I would appreciate any comments
Thank You
Pat Fontecchio
 
Space news on Phys.org
pfontec said:
Try thinking about measuring the expansion of the universe based on relativity. That is to say that depending on where you are located in the universe you might measure expansion or you might measure contraction!
Think about this.
The observer is placed anywhere inside of a giant ball of yellow "play dough". throughout the inside of the yellow ball are many little balls of different colored "play dough" representing galaxies.
Now something starts to squeeze the yellow ball.
Now depending on where the observer is located. He will percieve the colored "play dough" (the galaxies) expanding or he we percieve the galaxies contracting.
Can it be that our universe is being sqeezed by other dimensions (other universes?

I would appreciate any comments
Thank You
Pat Fontecchio
If the universe is being squeezed, then it would have to be squeezed by gravity. But observation indicate a homogenous, isotropic universe at large scales. So there does not seem to be any mechanism for squeezing.
 
Let us assume that the yellow ball is being sqeezed equally from all directions.
And let us assume that the yellow ball is compressing.
There is at the exact center of our ball a infinitesimally small point at which there can be no compression, just like the epicenter of an Earth quake.
from the exact moment that compression starts ,there is, at that exact moment, expansion away from the epicenter equal in all directions.
So if the observer were closer to the epicenter what would he observe?
 
Don´t think of it as play dough, think of it as a raisin muffin in an oven. As the muffin itself expands, the raisins expand with the muffin giving all the raisins a expansion movement from what ever raisin you are standing on.
 
But in a universe with a finite speed of light [wrt local reference frames], cosmological expansion will be apparent to all observers. It is difficult to explain redshifts > 1.66 without cosmological expansion.
 
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##.
The formal paper is here. The Rutgers University news has published a story about an image being closely examined at their New Brunswick campus. Here is an excerpt: Computer modeling of the gravitational lens by Keeton and Eid showed that the four visible foreground galaxies causing the gravitational bending couldn’t explain the details of the five-image pattern. Only with the addition of a large, invisible mass, in this case, a dark matter halo, could the model match the observations...
Hi, I’m pretty new to cosmology and I’m trying to get my head around the Big Bang and the potential infinite extent of the universe as a whole. There’s lots of misleading info out there but this forum and a few others have helped me and I just wanted to check I have the right idea. The Big Bang was the creation of space and time. At this instant t=0 space was infinite in size but the scale factor was zero. I’m picturing it (hopefully correctly) like an excel spreadsheet with infinite...
Back
Top