Understanding Dark Energy and Its Impact on the Expansion of the Universe

[nekdolan]

The question is: Why does the fact that Galaxies moving away (and accelerating) from the Milky Way, means that the Universe is expanding?
If there was a *gigantic* black hole somewhere far away it would naturally cause this effect.
As objects get closer to the black hole they accelerate, and since we are also falling in we would too. Things that are closer accelerate faster, than things that are further away. So everything would look like it accelerates, looking at it from the Milky Way (since the rate of acceleration increases).
It is true that, if everything was falling into a black hole, that would cause the galaxies not just to accelerate, but to come closer, however that effect is not something we could measure, because of the acceleration.
Except, if the measured objects were at the same distance from the Black Hole. Like the Stars in a Galaxy...maybe that's why galaxies don't fly apart, and not because of dark matter?

I probably made some kind of mistake, so could you please enlighten me what it was!?

 

[Nabeshin]

There are two problems with what you mention.

1) If a large gravitational well were attracting things, we would see things moving primarily in its direction. We do not. We observe all galaxies to be rushing away from us.

2) If a large gravitational well were attracting things, we would not expect a linear relationship between recessional velocity and distance. But this linear relationship, Hubble's Law, is precisely what is observed.

 

[stevebone]

@Nabeshin

There are also problems in what you're saying

How can you tell IF a galaxy IS NOT orbiting something, taking in account that its orbit would be astronomically big, perhaps billions of light years. From our Milky Way's point of view galaxies would indeed move in all directions also if they were orbiting something, a black hole or not.

Now on the topic. I am a bit, actually very, skeptical when it comes to the expanding universe theory. I kind of have my own theory.

If the Big Bang was an implosion > explosion then some matter should be left over at the point of the explosion itself. Now considering the amount of matter visible in the universe then we can safely say that at it's core the leftovers are still in a huge quantity, or maybe a humongous super-massive super-sized black hole.

Now that would solve many questions and eliminate most of the theories that do not have been efficiently proven.
The Universe would then be just like a solar system with a central force at it's center (a black home or a super-massive cluster of galaxies).

In orbit there would be all the structures that we see in the visible universe like galaxies, clusters of galaxies or super clusters. that would very much solve the problem of the expansion of the universe. we see red and blue shifted galaxies in the sky.

As Nekdolan said in his post, objects closer to the center would go faster than objects in a farther orbit and thus the difference in speeds observed. Orbits would be greatly big, perhaps billions of lightyears long. with our current technology we cannot determine with precision how galaxies are actually moving, one would need thousands or perhaps millions of years to determine something like that.

And there you are with no need for expanding theory or dark energy

There is the Big Bang...that looks like a accretion disk (an object in the middle and lots of gas around it) shortly after that Super-massive stars form that will die very soon leaving behind a massive black hole that will grow in time and build a galaxy around it. And the rest we all know and see today

But that is only my theory and at the moment nobody can say for sure that it is like this or not. We just don't know

 

[Nabeshin]

How can you tell IF a galaxy IS NOT orbiting something, taking in account that its orbit would be astronomically big, perhaps billions of light years. From our Milky Way's point of view galaxies would indeed move in all directions also if they were orbiting something, a black hole or not.

No, this makes no sense. If all the galaxies were orbiting a single object, there is simply no reasonable way to reproduce the effect of all of them receding from us. Think about it for a few minutes and you will realize that it is impossible. Not to mention you have not at all addressed problem #2. While it is true that a ellipse can look locally like a straight line, that does not at all solve the expanding universe problem!

If the Big Bang was an implosion > explosion then some matter should be left over at the point of the explosion itself. Now considering the amount of matter visible in the universe then we can safely say that at it's core the leftovers are still in a huge quantity, or maybe a humongous super-massive super-sized black hole.

Already you have a very very fundamental misconception of the big bang. It was NOT an explosion of any kind, and did not originate anywhere within a fixed background of space. The big bang describes the dynamics of spacetime itself.

Also, personal theories are not allowed in PF, especially when they are as misinformed as this.

 

[nekdolan]

There are two problems with what you mention.

1) If a large gravitational well were attracting things, we would see things moving primarily in its direction. We do not. We observe all galaxies to be rushing away from us.

2) If a large gravitational well were attracting things, we would not expect a linear relationship between recessional velocity and distance. But this linear relationship, Hubble's Law, is precisely what is observed.

Thanks for the explanation. I will look up Hubble's law.