Big Bang cosmology

Discussions ranging from space technology, near-earth and solar system missions, to efforts to understand the large-scale structure of the cosmos.

Re: Big Bang cosmology

Postby bangstrom on April 24th, 2020, 2:26 am 

hyksos » April 21st, 2020, 3:54 am wrote:
I am not ignoring what you say. I just don’t find it convincing.

You are ignoring what I say. I am repeating myself. Anyone reading this thread can see this happening.

Yes, you do repeat yourself a lot but all I see is a lot of unsupported personal opinions again and again as if repetition should make them credible.

hyksos » April 21st, 2020, 3:54 am wrote:
An accelerated expansion of the universe violates laws of physics and all previous predictions of either non-expansion or a slowing expansion. Even worse, is the ad hoc assumption of dark energy and the implication that 96 percent of the universe consists of something unknown and unexplainable. This is a bridge too far.

This looks like an admission that the acceleration is real. You seem wholly convinced that accelerated expansion has been definitively observed.

I have no idea where you get the idea that I claim the acceleration is real. Astronomers found an anomalous change in the apparent rate of change with distance in redshifts among extremely distant supernova. That is what they observed.

Their claim that this amounts to a real acceleration is dubious from my point of view because it runs counter to the known laws of physics and GR. Expansion should be slowed by gravity- not accelerated. I said more than once that cosmic redshifts may not be true indicators of recessional velocities. There may be other factors at work or redshifts may have nothing to do with recessional velocities. There are multiple possible causes that can explain cosmic redshifts.

hyksos » April 21st, 2020, 3:54 am wrote:
That would entail that you believe metric expansion is happening. Metric expansion of spacetime is one of the hallmark predictions of General Relativity. But wait , that would mean that GR is a correct description of the universe, right? What am I missing?


Metric expansion is consistent with GR but it is not the only possible explanation for cosmic redshifts. Accelerated expansion is not consistent with GR. If you toss a ball in the air, it slows as it climbs. It doesn't go faster.

hyksos » April 21st, 2020, 3:54 am wrote:
This isn’t clear. What law of gravity is being violated? Is it some classical law, GR, MOND? And of the 26 galaxies without dark matter, are you saying they are anomalies or the same condition we should expect of other galaxies?

It's perfectly clear. Lets not dance around this bonfire.


If you can’t even name which law is being violated or what the rotational anomalies you mentioned are telling us about the galaxies, it makes me wonder if you have any idea what you are talking about.

hyksos » April 21st, 2020, 3:54 am wrote:
Do you deny the existence of dark matter? Yes or no?

Not entirely. I accept that dark matter is a dark mystery. Some claim that stars and galaxies consist mainly of plasma and plasma rotates more like a wheel than like the planets around the our sun so electrical forces may be competing with gravity leading to the false conclusion that dark matter exists. I see this as a more plausible explanationl.
bangstrom
Member
 
Posts: 793
Joined: 18 Sep 2014


Re: Big Bang cosmology

Postby hyksos on April 30th, 2020, 5:05 am 

Yes, you do repeat yourself a lot but all I see is a lot of unsupported personal opinions again and again as if repetition should make them credible.


I supply multiply-corroborated telescope data, then I gave him a full bibliography of the publications of that data. bangstrom turns around and tells me that my posts are "unsupported personal opinions".

Their claim that this amounts to a real acceleration is dubious from my point of view because it runs counter to the known laws of physics and GR. Expansion should be slowed by gravity- not accelerated. I said more than once that cosmic redshifts may not be true indicators of recessional velocities. There may be other factors at work or redshifts may have nothing to do with recessional velocities. There are multiple possible causes that can explain cosmic redshifts.

onfusions that I neither have the patience nor the time in my real life to untangle and parse it.
I cannot make out a coherent position. I can't tell if he is asserting that GR does or does not describe the universe. I can't tell if he is supporting GR, but rejecting recent measurements of accelerated expansion. I can't tell whether he believes GR is inconsistent with accelerated expansion (it's not) Worse I can't even tell from his posts whether he believes that any kind of expansion is happening at all. Nor can I tell whether he thinks that the entire basis of expansion is an ad-hoc interpretation of redshift.

If you can’t even name which law is being violated or what the rotational anomalies you mentioned are telling us about the galaxies, it makes me wonder if you have any idea what you are talking about.
Not entirely. I accept that dark matter is a dark mystery. Some claim that stars and galaxies consist mainly of plasma and plasma rotates more like a wheel than like the planets around the our sun so electrical forces may be competing with gravity leading to the false conclusion that dark matter exists. I see this as a more plausible explanationl.


Denial of Dark Matter is public, appreciated, and shouted from rooftops. Nobody is censoring anybody else. Respected scientists investigated and published on theories that Dark Matter is not a real substance, and that galaxy rotation curves are due to unknown aspects of gravitation.

So stated. So appreciated. So recognized. Check and check. The theory was called MOND. Modified Newtonian Dynamics. It is the crowning achievement of the "Dark matter does not exist" line-of-theorizing. Everybody and their brother knows about it.

In the last two years, galaxies have been found that have regular old rotation curves, where their luminous matter content perfectly accounts for the rotational velocities of outer stars. There is no mystery in these galaxies. They found about 26 of them now.

If Dark Matter were not a real substance, then these galaxies should not exist, since rotation curve anomalies are (allegedly) due to fundamental aspects of gravitation, not from the presence of Dark Matter. But they do exist.

What is the picture now? The picture is 99.9% of galaxies have anomalous rotation curves, and 0.01% of them do not. It rotational curve anomalies are due to fundamental physics (MOND), then how can there exist a galaxy that violates fundamental physics? Good question.

marginal side bar : https://www.iep.utm.edu/reductio/

The rational explanation is breathing down our neck. What we are observing is that most galaxies contain dark matter, and a tiny minority of them do not. The hypothesis that Dark Matter is not a substance is looking terrible right now. (Without any philosophical or metaphysical prejudice) MOND is rejected on the sole basis that it is no longer matching observation. Period.

https://xkcd.com/1758/
User avatar
hyksos
Active Member
 
Posts: 1787
Joined: 28 Nov 2014


Re: Big Bang cosmology

Postby bangstrom on April 30th, 2020, 7:24 pm 

hyksos » April 30th, 2020, 4:05 am wrote:
I supply multiply-corroborated telescope data, then I gave him a full bibliography of the publications of that data. bangstrom turns around and tells me that my posts are "unsupported personal opinions".


My claim is that “a lot” of what I see is unsupported personal opinions but I admit, not all is unsupported. I asked where you got the chart and you never replied. The bibliography you gave me came with the chart but where did you get the chart?

hyksos » April 30th, 2020, 4:05 am wrote:[
I cannot make out a coherent position. I can't tell if he is asserting that GR does or does not describe the universe. I can't tell if he is supporting GR, but rejecting recent measurements of accelerated expansion. I can't tell whether he believes GR is inconsistent with accelerated expansion (it's not) Worse I can't even tell from his posts whether he believes that any kind of expansion is happening at all. Nor can I tell whether he thinks that the entire basis of expansion is an ad-hoc interpretation of redshift.

I am largely supportive of GR and the measurements but I am highly dubious about the interpretation that the measurements indicate accelerated expansion and I explained why. For one reason, accelerated expansion is not consistent with GR. No expansion at all, or a slowed expansion would be consistent with GR but accelerated expansion is not.

I said GR and accelerated expansion are inconsistent. You said (it’s not0. This is another example of what I say is an unsupported personal opinion because you state an opinion and then say no more about it. How do you find GR and accelerated expansion to be consistent?

hyksos » April 30th, 2020, 4:05 am wrote:[
The rational explanation is breathing down our neck. What we are observing is that most galaxies contain dark matter, and a tiny minority of them do not. The hypothesis that Dark Matter is not a substance is looking terrible right now. (Without any philosophical or metaphysical prejudice) MOND is rejected on the sole basis that it is no longer matching observation. Period.

If I understand correctly, the data in the chart you gave was based on MOND calculations so what do your statements say about the data in the chart?
bangstrom
Member
 
Posts: 793
Joined: 18 Sep 2014


Re: Big Bang cosmology

Postby hyksos on April 30th, 2020, 10:36 pm 

>> If I understand correctly, the data in the chart you gave was based on MOND calculations so what do your statements say about the data in the chart?


Sorry about the confusion. The chart has nothing to do with MOND. You have decided to attack dark matter, and so that's why the MOND sidebar was followed, conversationally.


>> I asked where you got the chart and you never replied. The bibliography you gave me came with the chart but where did you get the chart?

I don't remember. It was likely on a professor's personal website related to how to read scatterplots of globular clusters.

My best guess is that it might be on this website somewhere. http://web.physics.ucsb.edu/~jatila/Lam ... bular.html I'm too busy to nose around there.


The heavy lifting here is trying to pin down the bibliography, which is really not easy to do. In some cases, you have to drill down into the citations of unrelated papers to find out the real name of the publication.
User avatar
hyksos
Active Member
 
Posts: 1787
Joined: 28 Nov 2014


Re: Big Bang cosmology

Postby bangstrom on May 1st, 2020, 12:55 am 

hyksos » April 30th, 2020, 9:36 pm wrote:>>
The chart has nothing to do with MOND. You have decided to attack dark matter, and so that's why the MOND sidebar was followed, conversationally.

My apologies, the confusion was mine. I had the lambda CDM calculations in mind when I asked about MOND so forget I asked.

hyksos » April 30th, 2020, 9:36 pm wrote:
I don't remember. It was likely on a professor's personal website related to how to read scatterplots of globular clusters.

I have the same problem quite often. I’m beginning to think the Mandela effect is real where the past keeps changing and the things we remember well vanish from history.
bangstrom
Member
 
Posts: 793
Joined: 18 Sep 2014


Previous

Return to Astronomy & Cosmology

Who is online

Users browsing this forum: No registered users and 7 guests

cron