Age of Universe: T=1/H, Flat Geometry?

[randa177]

We ususally find the age of the universe : T=1/H , is this true for all geometries of the universe,,, say for example flat universe with (lamda) = 0

 

[Wallace]

No, the relationship between the age of the Universe and the Hubble constant as measured today depends on the detail of the cosmology, i.e. how much matter is in the Universe, how much dark energy, what is the equation of state of the dark energy, the curvature of the Universe etc. In some unrealistic but easy to calculate cases we have simple relationships between age and H but in realistic models (that match the observations) the relationship depends on more complex formulas.

Note that the age of the Universe doesn't really matter in some sense. It's calculated more as an afterthought for particular models. There are few things that actually depend on the age of the Universe, most measurable quantities depend on other factors, not the age. Some people misunderstand the significance of the age of the Universe. In particular it does in fact turn out that the age of the Universe in the current best fit model is very close to 1/H (though this only applies at this point in time), and therefore it is claimed that this is perhaps evidence for simple models, such as constant expansion (no accel or deceleration) which also predicts that the age is 1/H. The problem is that the observations that constrain the model that predicts the age and completely inconsistent with linear expansion!

The age of the Universe is an interesting thing to know, and something that cosmologist tend to put on press releases, but most physical quantities, such as the amount of structure growth in the Universe, do not 'age' with watch time, but with other factors.

 

[Garth]

In particular it does in fact turn out that the age of the Universe in the current best fit model is very close to 1/H (though this only applies at this point in time), and therefore it is claimed that this is perhaps evidence for simple models, such as constant expansion (no accel or deceleration) which also predicts that the age is 1/H. The problem is that the observations that constrain the model that predicts the age and completely inconsistent with linear expansion!

Some would argue that some observations are also inconsistent with the Mainstream model, Extragalactic Radio Sources and the WMAP Cold Spot:

To create the magnitude and angular size of the WMAP cold spot requires a ~140 Mpc radius completely empty void at z<=1 along this line of sight. This is far outside the current expectations of the concordance cosmology, and adds to the anomalies seen in the CMB.

Garth

 

[Wallace]

Wow! I thought you'd be above this kind of trolling Garth.

My comment and this thread has nothing to do with observational confirmation of the standard or any other model. I can't fathom what lead you to make the above post?

The only point about observations was that you can't use the age predicted by one model to confirm a different model with the same age if they predict different observables. That is a truism of methodology, not a statement about models.

What were you trying to achieve?

In any case, since your trolling has worked and elicited a response, you are citing very selectively on the issue you raised. The measurements of the void are quite uncertain and the modeling of what kind of void would produce what signal is also unclear. They is no clear definition of what precisely constitutes a void, which causes a fair bit of confusion and miscommunication. The moral of the story though is that the consensus view of the void and cold spot issue is that it is not a clear issue for the standard model, but is an area of research that needs more work to be more certain of whether is truly does or does not pose any issue.

Making grandiose statements about tentative results in threads unrelated to the issue is conducting unbecoming someone of your stature around here Garth.

 

[Garth]

The observation exists, and as you say it needs more work, but it would give a false impression if we said that there were no problems with the present understanding of the expansion history of the universe and the Age derived from the Mainstream model.

No tolling intended, just a open questioning mind.

Garth

 

[Wallace]

The observation exists, and as you say it needs more work, but it would give a false impression if we said that there were no problems with the present understanding of the expansion history of the universe and the Age derived from the Mainstream model.

I've got no arguments with the above, however nobody in this thread had made any claims about the standard model and its perfectness, my question was why you felt you needed to jump in with such a tangential post and make such a strawman argument?

My second issue is that you displayed none of the caution you request others to show about the standard model in your post that asserted the absolute incompatibility of the standard model with a piece of evidence that you brought up without stating any caveats about!

 

[Garth]

Wallace, randa177 asked the question "T=1/H , is this true for all geometries of the universe?" and you rightly pointed out that this would be true (in the standard theory) only "at this point in time". You then brought up the alternative linearly expanding model and added "the observations that constrain the model that predicts the age and completely inconsistent with linear expansion".

I have no quarrel with that except, for completeness and fairness, it ought to be mentioned that there are observations that appear to be inconsistent with the standard model as well.

Above I used the observation of the large void, I could also have mentioned large 3XSolar iron over-abundance of several distant quasars or massive high z galaxies, which have been discussed on the Is there an Age Problem in the Mainstream Model? thread.

My gripe is, given that the 'Inflaton', DM particle(s) and DE have not yet been discovered in laboratory physics, there is an overconfidence IMHO that is often placed in the standard model.

Garth

 

[SpaceTiger]

Wallace is correct, this is not the place for discussing alternatives to mainstream cosmology. A large fraction of questions asked on the cosmology forum are answered in the context of the mainstream model of cosmology and it is not necessary (in fact, not acceptable) to be citing potentially challenging observations in every such thread.

 

[yogi]

Hitler used to burn books and condemn those who raised challenges to the establisment - the idea that we have to cram down the majority view to every newcomer who poses a query is a disgrace to science. I have noticed time and again where those new to this forum have posed questions with the hope of evoking a discussion, only to be put down, and leave. There are many who feel there is something fundamentally wrong with the standard model(s). What is wrong with introducing the traditional view with a caveat - I think that is what Garth was trying to get across.

If history teaches us anything, it is that the majority is seldom right

 

[Wallace]

There is a great difference between a model that has incredibly good agreement with almost all available data, and certainly complete agreement to 'first order' data, and a model that is in stark disagreement with even the most simple robust data.

The mainstream isn't wrong simply because it is the mainstream and it's intellectually lazy to take that view. The current model is almost certainly wrong, based on past experience of history, and the 'mainstream' researchers are all perfectly well aware of this. The point is the research is most efficient when you focus on those things which are working well, and see how to reconcile the problem were it is not so good, rather than models that don't work at all.

You are fighting a not existent enemy when you complain about researchers not considering 'not mainstream' models. If someone doesn't like the mainstream model and in their explanation of why they do not they demonstrate that they do not understand some aspect of it, it is incumbent on those who have the knowledge to explain the nature of that misunderstanding. There are good reasons that we have arrived at the standard model of cosmology, and they do not involve conspiracies or suppression of alternative views.

And by the way,"[URL lose[/URL]

 

[SpaceTiger]

Hitler used to burn books and condemn those who raised challenges to the establisment

Seldom have I seen such an early need to invoke Godwin's Law.

the idea that we have to cram down the majority view to every newcomer who poses a query is a disgrace to science.

Hello, welcome to PF. If you feel that we should overwhelm newcomers with every possible alternative to mainstream cosmology, I'll have to disagree. If you would like to discuss crank science, you'll need to go elsewhere. As for legitimate challenges to the mainstream model, there are many and they are being discussed in other threads.

If you have a problem with PF policy, there is a separate forum for that (Feedback and Announcements). Continued attempts to pick fights in unrelated threads will be considered trolling and will result in warnings/bans. Since this person's question has been answered, the thread will now be locked.

 

[SpaceTiger]

And by the way,"[URL lose[/URL]

Heh, beat me to it. Agreed on the other points as well.

Anyway, I'm going to lock this. If the OP doesn't feel their question was fully answered, I will re-open it at their request, but will restrict discussion to that topic. Further debate about PF policy can be carried out in Feedback and Announcements, if anyone feels it's necessary.