Reddit reviews Introduction to Cosmology

https://www.amazon.com/Introduction-Cosmology-Barbara-Ryden/dp/0805389121

Ryden's Introduction to Cosmology is extremely good and is used at a lot of universities.

Except if you read the literature evidence for the conventional notion of dark matter heavily outweighs evidence for "Modified Newtonian Gravity."

That being said, no is claiming we understand the true nature of gravity yet, as we haven't invented a Grand Unified Theory. Mind you, the conventional notion of dark matter entirely takes into account the effects of general relativity.

For an introduction to the subject, read this.

With out a doubt the best intro cosmology book is Barbara Ryden's intro to cosmology
http://www.amazon.com/Introduction-Cosmology-Barbara-Ryden/dp/0805389121/ref=sr_1_1?ie=UTF8&qid=1372720990&sr=8-1&keywords=barbara+ryden+cosmology

This was the one that we used for Cosmology. It starts pretty gentle but moves into the metric tensor fairly quickly. If you don't have the maths I don't know that it'll help you to understand them but it'll definitely have all the terms and equations. As with Dirac's Principles of Quantum Mechanics, the funny haired man himself actually had a pretty approachable work from what I remember when I tried reading it.

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This one has been sitting on my shelf waiting to be read. Given the authors reputation for popularizing astrophysics and the title I think it might be a good place to start before you hit the other ones.

>'You're saying there is some particular plane in space about which the entire universe is mirrored'.
Precisely!of all the replies we got, this.You identified the crux of Prof Okolo's argument -if not , why not ?If you are aware of any asymmetry which coud cause this, could you point it out to us ,(online resources and books or monoraph welcome too)

Not only that: why isn't the universe symmetrical with respect to every plane? Why is it not completely uniform and homogeneous throughout all space and indeed time, so that if you mirror across any plane (or for that matter uf you rotate about any axis, or choose a reference frame with any velocity, etc.) it still looks the same? Surely this would be the maximum possible symmetry.

The standard answer to both of our questions is that in the very early universe this was indeed true, but the symmetry was destroyed by the randomness of quantum mechanics. For instance a proton and antiproton might pop into existence in one place, but not in another place under identical conditions. Of course these random events would in general be independent; there need not be any correlation between events occurring on one side of some particular plane and events occurring on the other side.

The resulting deviations from perfect symmetry would be tiny at first but gradually became larger. If one area of space were very slightly denser than its surroundings, its gravity would pull in more matter, further increasing the density. The expansion of space itself would also magnify these tiny fluctuations to a much larger scale, forming galaxies and superclusters and all the other interesting structure we see in the universe.

The primary tool for studying this is what's known as the Cosmic Microwave Background. This is a pattern of radiation that was emitted in the very early universe, but is still "visible" today (in the same way that we still receive light from ancient stars that are now dead.) From this we see that the early universe does indeed appear to have been extremely homogeneous. But when examined very closely it exhibits the sort of very slight fluctuations and patterns you might expect from the earlier discussion, and these patterns are still studied closely for information about this era of the universe.

Here's a review article on the state of cosmology and CMB research up to 2001. Although the majority is quite technical, note the introduction, which outlines our current model of cosmology:

>that he universe is spatially flat, consists mainly of dark matter and dark energy, with the small amount of ordinary matter necessary to explain the light element abundances, and all the rich structure in it formed through gravitational instability from quantum mechanical fluctuations when the Universe was a fraction of a second old.

If one has some physics background at the undergraduate level, Ryden's Introduction to Cosmology is a good starting point.

Last, I should recognize that of course there is still some debate about whether quantum mechanics is truly random at all. If for instance you adhere to the "many-worlds" interpretation of QM, you would say that any apparent randomness is merely a result of our own limited perspective. In that case, it would probably follow that the "multiverse" in its entirety is completely symmetrical. But of course proponents of the quantum many-worlds interpretation already believe in multiple parallel Earths and so forth.

>Ouch!Ouch! That hurts,especially as Prof Okolo is a relation. However this is no reason to exclude him from harsh but valid criticism,: so, why do you think the paper is low-grade ,if so?(note,if you read the comment attached to our question, Prof Okolo mentions in a supplement he is aware of symmetry-breaking in certain physical interactions ,but this is no reason to suppose it wuld affect the paper)

Apologies for any personal insult. Of course to come to places like this looking for constructive criticism (or enlist friends and relations to do so) is probably not the behavior of a crackpot.

I also hate to come to a philosophical forum and lambast philosophers of physics for not being physicists; there's too much of that going around already! But that being said, if the thrust of Prof. Okolo's argument is to assert the existence (or lack) of any particular type of symmetry as a theoretical prediction, this seems very much a question for physicists, and it's unlikely one will be able to answer it without a strong familiarity with the current state and methods of cosmological research.

There's actually a large amount of different models you can come up with using the Friedmann equation by playing with the density of matter, radiation, and the cosmological constant. If you're interested in learning about cosmology, check out the book by Barbara Ryden. It's a very gentle introductory text that's accessible to anyone who knows a bit of calculus.

Ahh I see. Well since you've got a science degree already, you're better prepared to start learning than most people out there.

If it's any help, I strongly recommend Barbara Ryden's Introduction to Cosmology as a nice upper-level undergraduate intro to cosmology. As long as you have a decent grasp of calculus, and remember some fundamental electricity and magnetism, it should be readable.

Amazon Listing here

It's nice because it assumes no knowledge of GR (she presents some equations/results from GR, but you just basically have to treat them like law, basically the same way they introduce F=ma in physics 101). The book really tries to work off logical arguments and physical reasoning than it does lots and lots of math.