Why Are Galaxies Accelerating Away?

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    Accelerating Galaxies
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Discussion Overview

The discussion centers around the phenomenon of galaxies accelerating away from each other, exploring the implications of gravity, the expansion of the universe, and the roles of dark energy and dark matter. Participants engage with theoretical concepts, question existing models, and share varying perspectives on these complex topics.

Discussion Character

  • Debate/contested
  • Exploratory
  • Technical explanation

Main Points Raised

  • Some participants note that gravity pulls galaxies together into clusters, yet galaxies can still be observed moving away from each other due to the expansion of the universe.
  • One participant compares the expansion of the universe to raisins in a rising loaf of bread, suggesting that the space between galaxies is expanding rather than the galaxies themselves moving through space.
  • Others introduce the concept of dark energy, indicating it may play a significant role in the accelerating expansion of the universe, although its nature remains largely unknown.
  • A participant challenges the idea that expansion requires a force, arguing that the universe's expansion is a result of inertia from the Big Bang, and that gravity acts to slow this expansion.
  • There is mention of dark matter as a component of the universe, with some participants asserting that while evidence for dark matter is strong, dark energy remains less understood and more contentious.
  • One participant raises a question about the possibility of increasing velocity with decreasing acceleration, seeking clarification from others.

Areas of Agreement / Disagreement

Participants express differing views on the mechanisms behind the acceleration of galaxies and the role of forces in the expansion of the universe. There is no consensus on these topics, with multiple competing explanations and models presented.

Contextual Notes

Some discussions involve assumptions about gravitational forces, the nature of dark energy, and the interpretation of cosmological models. Participants also highlight the complexity of these concepts, indicating that further clarification and exploration are needed.

  • #31


what is a 'new' neutrino? I am phd student in theoretical particle physics and never heard that term before, maybe you are referring to neutralinos? Or just the good old Standard Model neutrinos with mass? Their mass is too small to account for the missing energy density. I can give you some good reading advices, try the textbook by Grupen "Astroparticle Physics".

I don't know why electromagnetic effects should be vital for making up gas clouds, never seen such fine tuning in the simulations I've seen...

Are you a student of physics or similar?

I asked for your agenda regarding this quest of keep saying that dark matter is unknown, does not explain anything and so on, but in the meantime saying that modified gravity theories are crap as well. What do you want?
 
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  • #32


malawi_glenn said:
what is a 'new' neutrino? I am phd student in theoretical particle physics and never heard that term before, maybe you are referring to neutralinos? Or just the good old Standard Model neutrinos with mass? Their mass is too small to account for the missing energy density. I can give you some good reading advices, try the textbook by Grupen "Astroparticle Physics".

I don't know why electromagnetic effects should be vital for making up gas clouds, never seen such fine tuning in the simulations I've seen...

Are you a student of physics or similar?

I asked for your agenda regarding this quest of keep saying that dark matter is unknown, does not explain anything and so on, but in the meantime saying that modified gravity theories are crap as well. What do you want?

I want to know more. The reason for questions -- my only reason.

I have a MSc in Engineering Physics -- obtained over 35 year ago. It did include several courses in astrophysics and cosmology of the time. I am now retired and wanting to learn all that I have missed while having to make a living.

In my life experience I have learned not to accept reports at face value -- always question. Just the process of questioning often brings forth new information. It nearly always helps put matters in better context. The article writers and people in the field use many assumptions that are not always obvious to ones outside the field. Its very hard to determine what they are from the outside.
 
  • #33


Well asking questions are ok, but you sometimes make very bold statements etc.

You then might want to pick up the book I referred to, it contains both modern particle physics and cosmology/astrophysics suitable for master students and contain many references.
 
  • #34


malawi_glenn said:
Well asking questions are ok, but you sometimes make very bold statements etc.

You then might want to pick up the book I referred to, it contains both modern particle physics and cosmology/astrophysics suitable for master students and contain many references.
Planning on it -- as soon as I can afford it. Thanks.
 
  • #35


...mispost
 
  • #36


If the rate of expansion of the universe is speeding up how could the expansion be caused by an explosion (Big Bang)? I know of no explanation for an explosion that gains energy over time.
 
  • #37


frumenti said:
how could the expansion be caused by an explosion (Big Bang)?
It wasn't. The Big Bang was not an explosion. It was a rapid inflation. "Big Bang" was actually a term coined by its critics as a way to ridicule it.
 
  • #38


New to the forum. Could the gravitational time dilation (as opposed to dark matter) explain why the outer stars of a galaxy are able to travel at the high speeds. Essentially, they travel slower but have more time to make up the distance.

On a side note, how much empirical evidence is there for dark energy? If dark matter was proved to be an incorrect hypothesis, would dark energy be necessary? Could local gravitational fields at the more distant clusters be causing the changes in velocity?
 
  • #39


Johny Fake said:
New to the forum. Could the gravitational time dilation (as opposed to dark matter) explain why the outer stars of a galaxy are able to travel at the high speeds. Essentially, they travel slower but have more time to make up the distance.
They have factored in relativistic effects, yes.
 

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