To my knowledge, no modern scientific theory has claimed a universe from "nothing" in the sense implied by Creationists. There is always an initial energy and/or space/time and/or the quantum foam, etc., which is certainly not "nothing."

"Space" in modern terms would never be truly empty -  it would always contain 'fields' of some kind, especially gravitational, but also electromagnetic. Without such fields, one could not even define the extent of a volume of space especially in the context of general relativity..

The presence of matter particles does not eliminate the 'empty' space between the particles.

'Dark matter' and 'dark energy' definitely exist as evidenced by many measurements. IOW, something exists in addition to 'normal' matter and energy that can be measured by many of the same means as used to detect/measure ordinary matter and energy in the cosmic environment.

Dark matter usually refers to additional matter that would need to exist to explain the observed trajectories of interacting galactic objects.

Similarly, 'dark energy' is the additional energy which must be present for various obsevations to comply with the fundamental laws of physics.  What is still problematic about both concepts is their ultimate nature, what particle/fields they are composed of, due to the fact that they do not seem to interact with electromagnetic fields, hence they do not generate or absorb light or other electromagnetic radiation, hence 'dark'.

I am more confident in msking these comments since getting into Laurence Kraus' book 'A Universe from Nothing' in which he states that dark matter "has been independently corroborated in a host of different astrophysical, contexts, from galaxies to clusters of galaxies".

Hope this helps to clarifify the current state of understanding about this topic.

Anyone have any thoughts on the Steinhardt-Turok ekpyrotic model? Is that hypothesis still alive and well or has someone eviscerated it by now? I don't really pay that close attention to astrophysics. 

There is empty space between particles on and in the Earth. By your reasoning, we must live in a vacuum. Just where did you get your so-called scientific knowledge anyway? A layman is kicking your ass.

False.

Uh uh. A simple error in the understanding of gravity and spacetime could be responsible. Dark matter may not exist, and I can point to hundreds of PHD's who agree. You're speaking as if your understanding was known and demonstrated fact, and it isn't.

There are alternative explanations for so-called dark energy too.

And according to many scientists working in the field, they might not exist at all. You're depending on pop-culture scientific hypothesis which may very well be proven wrong. Until someone identifies dark energy and/or dark matter, speaking of them as if they were known to exist is roughly equivalent to belief in a god.

I think you need to do more reading.

No. If using a single word, the term explosion is superior to expansion. That's all I'm saying.

And the scientific community doesn't give a rats ass about you or me or Bob or anyone else here. I guarantee a good number of them would agree with me. That a good number would agree with you is of no consequence. You're all wrong.

"Living in a vacuum" would require that the average density of gas around us was very low, which is obviously not what I am claiming and NOT even implied by what I have stated. Where the hell do you get your information? Kicking my ass? LOL.

I get my information on the current state of Science from podcasts by Scientific American, Nature, The Royal Society, AAAS, various BBC broadcasts, and so on. as well as NewScientist magazine, which I have subscribed to for at least twenty years ( now I get the electronic version ).

It is a standard idea in science that even 'solid' objects are in fact mostly empty space. Atoms themselves are 'mostly empty space'. Are you saying that 'mostly empty space' defines a 'vacuum'?

What I am saying is that those measurements that point to significant discrepancies in current cosmology DO exist, and the hypothesis that has most readily occurred to cosmologists is that there exists some 'extra' matter or energy that would produce the observed effects but is not easily detected otherwise. Laurence Kraus thinks the evidence for dark matter is now very strong, so I think more than a simple denial is required. Seriously.

I think it would need to more than a 'simple error' and made by quite a number of theorists. A better way to put it in this context would be point to alternative hypotheses that explain current observations at least as well as dark matter/energy and has fewer complications.

I concede that there may still be more dispute about this than implied by what Kraus has been saying

So Laurence Kraus is just a 'pop-culture' scientist?

Most scientific theories 'may very well be proven wrong', but if you don't want to go with any theory until it has been has an iron-clad proof, that is very restrictive. I think there is way more scientific support for dark matter than God, so stop with such absurd comparisons, please.

Sorry, you made enough ill-informed or poorly thought through 'arguments' there for me to not take your comments too seriously overall. Although I will concede that you did provoke me to do more research which did make me aware of some aspects of the current controversy over this topic that I had missed. IOW, some of your points did strike home. Thank you for that.

You are referring to the 'ether' - once described as the "luminiferous aether" ie the medium through which it was imagined light was propagated as waves, as sound is propagated through air, which was assumed to be necessary to support the propagation of light as waves. The alternative theory was that light was transmitted as particles.

There was a long series of arguments about the nature of light (particles or waves) and the ether, in which all theories seemed to have problems, ultimately more-or-less resolved by James Clerk Maxwell's theory of electromagnetism in which light is seen as waves in electromagetic fields. A big problem with the ether theory was that it implied that the apparent speed of light should be affected by the movement of the Earth through the ether, which would be expected to vary depending on the position of Earth in its orbit, which many successively more careful experiments failed to detect. I think Einstein's Relativity theories made it even harder to maintain ideas of an 'ether', so it ultimately died by Occam's Razor.

So I really doubt it can be revived in any form,

I'm glad you laughed, I was attempting to lighten the mood some.

I'm not trying or going to try to convince you to see things my way. It just doesn't matter enough. But I'm not changing my view.

Yes I'm kicking your ass. I'm doing it so well that you're now changing the subject to specific density when we were talking about it generally. Ironically I already accounted for this shift in a previous post.

Are you saying it doesn't?

vac·u·um/ˈvakˌyo͞o(ə)m/
noun
a space entirely devoid of matter.
a vacuum cleaner.

Much better.

I'm glad we provoked each other to learn new things. Makes the friction worthwhile. My thanks to you as well, as I had to reacquaint myself with some fascinating materials to have this conversation.

You are technically correct, AFAIK,  that gravitational forces would exist between sub-atomic particles, but within the scale of atoms they would be totally swamped by the electromagetic and shorter range forces, called the 'strong force' and the 'weak force'. So gravity would just not be considered when examining things at the atomic scale, even less so at the subatomic scale

The strong force acts only on 'quarks', particles which are the sub-particles of protons and neutrons, while the 'weak' force is involved in radioactive decay, such as when a neutron spontaneously transmutes into a proton, an electron and an antineutrino. The force holding atoms and groups of atoms together is the electromagetic force, so it is what gives matter its form.

What we mean by 'empty space' really depends on the context. In ordinary day-to-day conversation it implies a near zero gas pressure, ie, very few to zero gas molecules in any given volume, what we ordinarily refer to as a 'vacuum'. We would only normally consider fields such as gravity and electromagnetic fields in a very 'scientific' context. In a strict context, we might also chose to consider only matter particles, not the force fields, in which case an atom, and hence solid matter, is 'mostly empty space', since the distances between the electrons and the nucleus are vast relative to the sizes of the electrons and the nucleus.

Probably, but that scenario is somewhat larger than the atomic scale, I think...  So gravity would indeed be the most appropriate force to consider in such a context.

with "expansion". On the first count "explosion" is the most popular, but that doesn't make it correct. We all become victims of populaity. I say explosion was used unindendedly. It'sthe same as when I use the term "God", what I mean is "force", because that's what it gets right down to--a discription of an application of force. Okay everyone--let's not get off on the God thing and go off topic. I only mean that--the use of the wrong word or explanation is oft time inadvertent or forced for an understanding. Sometimes one has no choice. 

I often imagine the "big bang" being a balloon type of event. While inside the membrane there is no movement. The balloon membrane breaks allowing every thing to expand giving room to move about, which causes extreme temperatures, collisons, etc.

Coincedently thinking this yesterday. I was also thinking that what expanded may have partially became an explosion. During the initial "sudden" expansion if matter was created then there is fuel (so to speak) to explode. Of course that would have to have been after the fractional second of the expansion. I was thinking todayon dark matter--that what may account for the increasing velocity of the gallaxies away from a center may be caused by the gravitaional pull of another Big Bang at another point in space. Unless all of space was incorporated into the big bag and there can't be another cluster of gallaxies far off. I was looking at "our" section of space as a cluster  of galaxies. Is there a possiblity that another Big Bang could take place.?? maybe our's is younger and another is older. Can't say.

That still leaves the question---who created energy to cause the Big Bang. I bring this up beause I'm camped out at the Oaks Campgrounds in the San Gabrieal mountans north of Azusa CA. In a conversation with a highly religious person(s) I pointed out that there is now a different interpretation (I didn't claim to be one of the  founders/finders of the interpretation) but --they wanted to know where the material in the universe came from.

For perspective--This was a conversation that was taking place by a camper that was approached by the two (apparently husband and wife) who were at the site preaching "God", religion and etc. I went over to the amper that I know and being he is older I was conered for his well being as I haden't seen him up and about in the last two days. On the other side of his motor home ,out of my sight, he was conversing with the two religious types who often come up to the amop area to preach to the miners and prospectors. (so he was OK) He is not a believer in "God". This is an area along the East Fork of the San Gabriel river where the faithful come up from Los Angelles etc and build a small dam to do baptism dunking, of which I wittnessed for several years now.

OK-So--The camper got me involved after standin there for a while listening (and not careing to get involved) and asked me "what I think and believe". I agree'd with him and gave a few explainations of "the Smurfs" understanding of things---and  Holy Kow. After making a few statements on the BB and that there's no such thing (cordially of course) as an intelligence without a brain so there can be no Super natural being etc etc etc, and, the question was asked as she pointed at the river, cliffs and mountains--who made all this. I said--it's a natural construction of universal law, and for the explaination that I know about--the bible creation story isn't about material creation but rather spiritual, and after a while it sunk in what I was getting at--the embarrasment on their faces us acutely evident--and they started to get upset--so I ceased and desisted before I got my face punched.

OK--so how do you tell religious floks they got it wrong. The energy existing (if that's turns out to be the case)before the BB is no answer to these floks because as far as they are concerned they cannot be wrong---because the bible says so.

What I want to point out here is----you may get some idea of their embarassment that another interpretation exists---which indicated to them that at least they got it wrong--and they couldn't deny it. Once it sunk in silence occured. Bear in mind--that they think they cannot possibly have it wrong--and they do, they were stumped and getting irate---so off I went.

So, the BB isn't going to do for them is it?  They want to know who caused it.   One can understand the monumental task it's going to take to get things changed around.