Expansion or Acceleration

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Expansion or Acceleration

Postby buckles29 » Sun Feb 17, 2019 9:18 am

From the last Sky at Night programme....

I am not a scientist but thought this should be considered - this is not a debate for me, just some ideas ' out of the box'.

1. Should we be treating the Hubble constant as a constant at all? By assuming the universe were to be accelerating in its rate of expansion would explain potentially the difference in the measured results using the different methods. In other words, taking an average rate of expansion from time point 0 (the earliest observable CMB) would yield an incorrect, and lower, value if the constant is not a constant. Perhaps we should be measuring not in ms but ms per s.

2. Expansion should also consider (and I am going way out there now) that other universes have an increasing gravitational affect on ours as we expand. Maybe the matter needed to explain the expansion of our universe is not in our universe at all?????

Just some thoughts

Neil Buckley
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Re: Expansion or Acceleration

Postby Graeme1858 » Sun Feb 17, 2019 11:45 am

Hello and welcome to the forum Neil.

Most of us are more in the enthusiast category rather than the scientist category so cosmology (also known as speculation!) is hugely complicated but it is a very intriguing aspect of astronomy because of that. The Hubble constant was calculated as a measure of red shift as a function of distance (km/sec/Mpc) and has been refined over the years using the CMB and supernovae etc. It will continue to be modified based on some things we know to be true and things we are just theorising about. Theories change (is a Type Ia constant?) and new information is revealed by mother nature (Gaia mission, Hubble, JWST etc). So, we don't really yet know if we should treat the Hubble constant as a constant! And whilst we say the expansion of the universe is caused by Dark Energy, that's just a name we give to something we don't have a clue about! It's just the name we give the phenomenon. The observed values of expansion based on vacuum energy differ from the calculated values of quantum field theory by 120 magnitudes. (1 with 120 zeros!)

Your point 2 is intriguing. Expansion caused by something outside of the observable universe or an interaction between multiverses. Got to love cosmology!

It was an excellent Sky at Night episode!

Regards

Graeme
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Re: Expansion or Acceleration

Postby Gfamily2 » Sun Feb 17, 2019 12:02 pm

buckles29 wrote:From the last Sky at Night programme....

I am not a scientist but thought this should be considered - this is not a debate for me, just some ideas ' out of the box'.

1. Should we be treating the Hubble constant as a constant at all? By assuming the universe were to be accelerating in its rate of expansion would explain potentially the difference in the measured results using the different methods. In other words, taking an average rate of expansion from time point 0 (the earliest observable CMB) would yield an incorrect, and lower, value if the constant is not a constant. Perhaps we should be measuring not in ms but ms per s.

2. Expansion should also consider (and I am going way out there now) that other universes have an increasing gravitational affect on ours as we expand. Maybe the matter needed to explain the expansion of our universe is not in our universe at all?????

Just some thoughts

Neil Buckley

My understanding is that the CMB measurements don't give us a direct measurement of Hubble's 'Constant', and it's recognised that it's not actually a constant.
Measurement of Cepheid variables gives us a value that's true for `local` domain and `current` era.
However, what the CMB does tell us is what the current and local value should be. And that's where the discrepancy lies.

With regard to your second point, some sort of leakage of gravity has been postulated as a solution, but in general has been discounted.
The are all sorts of problems with the proposition; but then again, there are all sorts of problems with our understanding the universe as it is - so it may have legs, but a lot needs sorting out.
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