Universe only appears to be expanding.

In summary: Scientists are still trying to piece together the idea of a 'void' and how it might exist. The theory is that the universe started out as a single point, then expanded. But this idea is still unproven.
  • #1
Grajek
7
0
Has anyone ever given serious thought that the universe only appears to be expanding because most, if not all, galaxies have a black hole in the center sucking the galaxy into it? If you have X amount of galaxies basically being sucked into the black hole at their centers would it not look like each galaxy is moving away from each other thus appearing to have the cumulative affect of an expanding universe?. Given the limited detail provided with telescopes at a galaxy 10 billion light years away could we even determine that the red or blue shift of a galaxy is due to the galaxy shrinking or moving away from ours? Not to mention what we see is only a 10 billion year old snap shot.

Just wondering(out loud).
 
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  • #2
Grajek said:
Has anyone ever given serious thought that the universe only appears to be expanding because most, if not all, galaxies have a black hole in the center sucking the galaxy into it? If you have X amount of galaxies basically being sucked into the black hole at their centers would it not look like each galaxy is moving away from each other thus appearing to have the cumulative affect of an expanding universe?.
Yes it's been proposed. And immediately rejected. The simple geometry just does not result in that observed effect.
 
  • #3
The problem with this idea is that the black holes at the center of galaxies are not pulling everything in the galaxy in it at once, but keeps the stars in the galaxy in orbit together. So then the black hole acts like our sun in the solar system and then these galaxies are moveing away from each other, if that gives you a better picture of the universe.
 
  • #4
That does give me a better visual, thanks.

How long can the stars maintain an orbit around the black hole, ball park, before they fall out of orbit and into the black hole.

Thanks again for the explanation.

-Grajek

John232 said:
The problem with this idea is that the black holes at the center of galaxies are not pulling everything in the galaxy in it at once, but keeps the stars in the galaxy in orbit together. So then the black hole acts like our sun in the solar system and then these galaxies are moveing away from each other, if that gives you a better picture of the universe.
 
  • #5
If your idea were correct, the far side of a galaxy would be blue shifted and the red and blue shift would vary with the distance from the center. In short, it would look nothing like what we observe.
Grajek said:
How long can the stars maintain an orbit around the black hole, ball park, before they fall out of orbit and into the black hole.
More or less forever.
 
  • #6
Grajek said:
How long can the stars maintain an orbit around the black hole, ball park, before they fall out of orbit and into the black hole.

How long will the Earth orbit around the sun before it falls out of orbit and into the sun?
 
  • #7
Plebeian said:
How long will the Earth orbit around the sun before it falls out of orbit and into the sun?

Russ put it eloquently: More or less forever.

Bodies don't "fall out of orbit" without good reason.

Then again, a good reason is going to visit us in about 5 billion years. The sun will go all Red Giant on our a$$, expanding in radius until it engulfs Earth in its orbit, and possibly Mars too.

That'll render the idea of "Earth orbiting the sun" kind of ... quaint.
 
  • #8
The universe only appears to be expanding?

I’ve wondered about that one. If we live in a closed manifold, then some of the images from galaxies are not new galaxies. They would be light reflections of galaxies as they existed billions of years ago.
 
  • #9
DaveC426913 said:
Then again, a good reason is going to visit us in about 5 billion years. The sun will go all Red Giant on our a$$, expanding in radius until it engulfs Earth in its orbit, and possibly Mars too.
:biggrin:I read quite some time ago that scientists were seriously considering a way, as the sun expands, to move Earth into Jupiter's orbit to avoid the 'heat death' of Earth. True or False?:bugeye:
 
  • #10
PhanthomJay said:
:biggrin:I read quite some time ago that scientists were seriously considering a way, as the sun expands, to move Earth into Jupiter's orbit to avoid the 'heat death' of Earth. True or False?:bugeye:

I think the word 'seriously' must be examined carefully.
 
  • #11
What of the idea that we happen to be in a universal 'void', and the only reason that it appears the universe is expanding is that our observable universe is surrounded by a denser pocket of space?

The only problem is it is essentially unfalsifiable at this point, as we cannot even see the universe outside of our own little pocket.
 
  • #12
Er, fantasy.
 

Related to Universe only appears to be expanding.

What is the evidence that the universe only appears to be expanding?

The main evidence supporting the idea that the universe only appears to be expanding is the observation of a phenomenon known as "redshift". This is when the light from distant objects in the universe appears to be shifted towards longer (redder) wavelengths. This can be explained by the Doppler effect, where the motion of an object causes a shift in the wavelength of light. In this case, the redshift is interpreted as the result of the expansion of the universe. However, there are other possible explanations for redshift, such as the tired light theory, which suggests that the light itself is losing energy as it travels through space.

What is the tired light theory and how does it relate to the expansion of the universe?

The tired light theory proposes that the redshift observed in distant objects is not caused by the expansion of the universe, but rather by the loss of energy as light travels through space. This theory challenges the idea of an expanding universe and suggests that the redshift is simply an artifact of the distance the light has traveled. However, this theory is not widely accepted by the scientific community and does not have as much evidence to support it as the theory of cosmic expansion.

Why do some scientists believe the universe is not expanding?

Some scientists believe that the universe is not truly expanding because of the lack of evidence to support the theory. While the redshift observed in distant objects is often interpreted as evidence of expansion, it can also be explained by other phenomena, such as the tired light theory. Additionally, there are some observations that do not fit with the idea of an expanding universe, such as the constant temperature of the cosmic microwave background radiation. These inconsistencies have led some scientists to question the validity of the expanding universe theory.

What are some alternative theories to explain the observed expansion of the universe?

Aside from the tired light theory, there are a few other alternative theories that have been proposed to explain the apparent expansion of the universe. One theory is the "variable speed of light" theory, which suggests that the speed of light may have changed over time, leading to the observed redshift. Another theory is the "Steady State" theory, which proposes that new matter is constantly being created in the universe, keeping it in a constant state of expansion without the need for a Big Bang event. However, these alternative theories are not widely accepted and have not been supported by as much evidence as the theory of cosmic expansion.

How does the concept of dark energy relate to the idea of an expanding universe?

Dark energy is a theoretical form of energy that is thought to make up a large portion of the universe and is believed to be responsible for the observed acceleration of the expansion of the universe. This concept was introduced to explain the unexpected observation that the expansion of the universe is not slowing down, as would be expected due to the gravitational pull of matter in the universe. Instead, it is accelerating, suggesting the presence of a mysterious force, or dark energy, driving this expansion. This discovery has provided further evidence for the idea of an expanding universe.

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