New Big Bang Cosmology

Actually, Eta_Carinae is probably the best informed person here on these matters. He knows exactly what he is talking about, and is certainly better positioned with respect to background than Dr Humphreys.Eta has chosen to be anonymous on the net, but has given some limited details of his background, including that his work as an astrophysicist over the last twenty plus years has encompassed aspects of stellar evolution, cosmology, and quantum gravity.All I can confirm, as a fairly well informed layman, is that he has demonstrated a depth of understanding of the material and the relevant theory consistent with his claimed background.Eta tends not to suffer fools gladly, and does not work well at explaining in detail for people who have no background, but are inclined to dismiss the entire field of modern astronomy without having made a passable attempt to learn a bit about it for themselves.For example, in Message 152 he says He has a reasonable point.Humphreys is a crank when it comes to cosmology; and his Starlight and Time is arrant nonsense. Your own invocation of the Sloan survey in Message 6 is bizarre. In fact, these deep space surveys are completely inconsistent with Humphreys' nonsense. The earlier 2dF survey pretty much demolished the notion of quantized redshift — which was the closest thing Humphreys had to any empirical basis for his ideas. The Sloan survey will be examined for the same effect I am sure; I have not seen a publication out as yet.The 2dF results have been discussed here, by JonF in Message 33. I've discussed it in other forums; I can't find having said much about it here; but my post Message 67 has some useful material.Cheers -- Sylas(Edit to fixed link to one of my posts)This message has been edited by Sylas, 05-14-2004 12:14 AM

Let me jump in here. No offense intended to anyone, but I don't think Gup20 knows enough about Humphreys' model or relativity to answer this question.Humphreys (I think) proposes a severely distorted curved spacetime which would result in Earth's clocks running very slowly in relation to the rest of the universe. The only thing we know that makes such a distortion is mass; but who knows... perhaps there is something else. There is precedent in physics for adding parameters (cf Einstein's cosmological constant) which have various effects. I think Humphreys simply proposes a spacetime structure which is roughly analogous to the constants added by other physicists in other cases.The major (MAJOR) difference is that real scientists attempt to make their models fit observations. Humphreys is just thinking of some way to reconcile his belief in a young earth with the plain evidence of a very ancient universe. Humphreys makes no serious attempt to test the implications of his model.It is worth noting that Humphreys indicates that this distortion in spacetime is something that existed in the past; not now. He has no basis for how it arose or how is dissipated. The actual relativistic equations used were fundamently wrong anyway; though I understand he has made some attempt to correct those errors without acknowledging that he was esposed as a klutz who doesn't understand relativity.The funny thing is; his ideas gain enormous support, as he is the only young earth creationist I know making any credible attempt to deal with the observational evidence of an old universe, since the demise of the absurd changing speed of light ideas of Stterfield. The problem has been recognized by others (Danny Faulkner, for example) but noone can think of any better way to deal with the evidence.Cheers -- SylasPS. Disclaimer: I'm a rank amateur in relativity; and I have not read the book Starlight and Time; though I've read some of the criticisms and defences.

Since you ask... it's gibberish. The tough problem is how to say that without causing offense.The description is reusing words and phrases from real cosmology and using them in new ways that just don't make sense. For example, 13.7 billion years is the age of the universe. How can it be the thickness of a membrane? The concept of "membrane" (or "brane") is also one that appears in cosmology, but it does not fit the kind of usage shown above. It is not something that exists simply in three dimensions.You can imagine, if you like, a piece of paper. It is like a "brane" which has two dimensions, but exists in a kind of three dimensional space. It has negligible thickness. If our universe was a "brane", then it has three dimensions, but the "thickness" would be in other dimensions that you cannot identify by moving around in space, but by looking in a new dimension entirely, which is not really accessible to our normal observation. The universe might be infinitesimally "thick" as a brane; and billions of light years in extent in the three dimensions we perceive.As for being pointed in the right direction; in my own personal view the best internet resource on cosmology is the cosmology tutorial and associated pages by Ned Wright at UCLA. Check it out. Parts of it are quite technical, so it will make depands of the reader; but it is still accessible for a layman.Cheers -- Sylas

I agree with your comment about the difficulty of being scared to say what we think. There is sometimes a fine line between being blunt about a proposed idea and being needlessly insulting to a person who is floating their own ideas with the aim of getting feedback. I'll do my best to be constructive and will be happy to answer questions to the best of my limited abilities. Fire away.Cheers -- Sylas

According to conventional Big Bang cosmology, there is no such thing as an "initial point" in space; and no such thing as a "leading edge" of expansion. These concepts usually arise when people think of the Big Bang as an explosion, which is a misleading analogy.The Big Bang is an expansion of space itself; not an explosion of something within space.Caveat: there are models which speak of leading edges in expansion of space, but it is much better to get to grips with the simplest models first. The leading edge in such models is still nothing like the expanding shell of matter from a conventional explosion.A conventional explosion has a central point, and a rapidly expanding shell of material which pushes out into a surrounding space. The Big Bang, by contrast, says that all of space used to be filled with matter at extreme density. As space expands, the density drops.This is covered in the website I cited for you previously. See in particular Ned Wright's FAQ answer to How can the Universe be infinite if it was all concentrated into a point at the Big Bang?, and Where was the center of the Big Bang?.One of the hardest things in getting started with understanding modern cosmology is the number of common preconceptions than need to be unlearned. I can't really follow what you are asking here. The speed of light is a limit on the motion of things through space, but it turns out not to be a limit on motions of space itself. Motions of space are something way outside our conventional assumptions about reality, but they are a consequence of general relativity. The distance between two points in a rapidly expanding space can increase many times faster than the speed of light. Of course, two such objects are invisible to each other.The expansion rate of the universe is not measured as a simple velocity, but with units of km/sec/Mparsec. The current expansion rate is about 71 km/s/MParsec. What that means is that points in space which are 1 MParsec apart will have the distance between them increasing at a rate of 71 km/sec. The speed of light is about 3*10⁵ km/sec, and so objects at a distance of about 4230 MegaParsecs will be separating from us at a rate corresponding to the speed of light. This is often described as moving away from us at that speed, but in general relativity this is not really a good way of putting it. The very concept of distance and speed tends to break on cosmological scales; they are localized approximations that work well on a "flat" space.One MegaParsec is 3260000 light years, and so 4230 MegaParsecs is about 13.7 billion light years. Sound familiar? This is the limit of the "visible" universe; the edge of what we could ever possibly see; and 13.7 billion years is the age of the universe; the time that it has been expanding. Sorry; I can't parse that into a meaningful question. A black hole involves a severe distortion of space, in such a way that notions of distance and speed get a bit tricky.Cheers -- SylasThis message has been edited by Sylas, 05-18-2004 07:59 PM

Tachyons. However, this is not an "appearance", but a speculative notion lacking any empirical support. That is, tachyons might exist; and theoretical predictions can be made. Attempts to test the predictions, however, have turned up a universal negative. There is nothing that "appears" to be tachyons, so far; and no particular reason to think they actually exist.The rest of your comments on their theoretical properties are fair enough.Cheers -- Sylas

Yes... all light paths inside the Schwarzschild radius (the event horizon) are directed inwards, and light or anything else can only move closer to the central singularity. Anything at all will reach that central singularity within a small finite time, no matter what it does with engines or propulsion devices.I believe that another way of expressing this is to regard space itself as flowing into a black hole, in some metrics; but I'd have to defer to Eta Carinae on such details. I guess so. The escape velocity at the event horizon is equal to the speed of light. One way to think of this is that an outwards directed photon at that exact distance is moving outwards at the same speed as space is flowing inwards, and so it does not actually move. A better way to think of it is to imagine a light source falling into the hole. The closer it gets to the horizon, the longer it takes photons to get back out to an external observer. The photons also get redshifted to invisibility. An external observer thus "sees" an increasingly redshifted object, but never sees it cross the horizon. We had a discussion on this recently, in which someone thought this meant that the object does not ever cross the event horizon. But it does, and quickly. You just can't observe the crossing from outside.Inside the event horizon, there is no escape velocity. It does not depend on your weight or size. The Schwarzschild radius is a point of no return for anything, regardless of composition. If you are a given distance from a black hole (say, one million kilometres) then the force depends on the mass of the hole. In fact, the force depends only on the mass involved; regardless of whether it is compressed into a hole or not. What makes a hole special is that you can get very close to it without hitting any surface. For example, a black hole with the mass of the Earth would have a Schwarzschild radius of just under a centimetre. But you can't get that close to the Earth, because ground level gets in the way. A hole the mass of the Sun has a Schwarzschild radius of about 3 kilometres.Cheers -- Sylas

No. Not really. The big bang is a very general concept; and refers to the idea that space expands, and that this expansion has spread out the entire visible universe (everything we can see) from what was once a very tiny region of space filled with unbelievably hot and dense matter and energy.The simplest mathematical models capture the entire universe within one expanding space. There are a number of ways that the simple model can be made more complicated. There are a range of ideas relating to how expansion got started, and to the possibility of other independently expanding spaces (multiverse), and to discontinuities (or edges) in space. There are variations in the topology and the geometry of the visible universe as well. Models without edges, and models which have discontinuities or edges, and many other variations even more strange, are all still big bang models. They all still involve the expansion of everything we now see from a very small region within an extremely hot and dense state of the universe.Many of the different speculative cosmological models are about different ideas relating to how the expansion got started, and to what might be going on beyond the limits of the visible universe. That is an excellent question, and grasping the answer to this was for me the key that suddenly let me grasp what the big bang is all about. I can still recall the sudden flash of recognition when it finally hit me just how background radiation relates to the big bang.The answer is that is that such photons as you describe do exist. They are everywhere. All of space, as far as we can see, is filled with such photons, and they are moving in all directions. They are called the cosmic microwave background radiation.13.7 billion years ago, a tiny fraction of second after the initial singularity, you can imagine that the universe was filled with hot dense energy. One way to think of this is to imagine that everything we can see now, out to the furthest reaches of our most powerful telescopes, is filled with matter looking a bit like the centre of the Sun.Even that is not really correct, in several respects. In fact, the universe was far denser and hotter than the Sun in the earliest moments. Second, the Sun is a particle, with a surface and edge. The state I am describing has no edge; all of space is like the centre of the Sun. The universe might be infinite, in which case this mass extends forever without bound. Or it might be finite, in which case you should think not of a edge to matter, but of space turning back in on itself like a four dimensional balloon, so that if you go off in one direction you find yourself back where you started, without having turned around. This is a bit like sailing around the world; travel in one direction and you get back where you started. Except, of course, that an ocean surface is two dimensional but the universe is three dimensional. You might call it a hypersphere.The difficulty is that space is also expanding, so if you set out on a trip around the universe, the expansion might prevent you from ever completing the journey.Anyhow, when the universe was this hot and dense, it was also opaque. Light could not travel freely though space, because it keeps hitting things. In fact, it took about 300,000 years before space had thinned out enough to be transparent to light. When that occurred, all of space was filled with very hot energetic photons, which were suddenly free to travel through space without impediment.Those photons continued to travel through space in straight lines, and they are still travelling today, 13.7 billion years later. Of course, all this time space has been expanding, and this has the effect of "stretching" photons; so now they have a much longer wavelength. They are very cool; no longer hot and energetic. We see them now as microwave radiation, coming to the Earth from every corner of the sky.Cheers -- Sylas

An object never hits light speed as it falls into a hole; not at the event horizon, and not at any point inside the horizon either. The horizon is a point where events go off our radar, in the sense that signals cannot get back to the outside world from inside the horizon.An object continues accelerating for a short finite time until it reaches the centeral singularity, at which time we can't say what happens. But it never reaches light speed.The lifetime of any object inside the horizon is very short; but time does have meaning because we can speak of how long it lasts before reaching the singularity.At the singularity, the object no longer exists as an object.Notions of time and distance still have meaning inside the event horizon; but at the point like central singularity descriptions break down.You can't say that the central singulaity exists in another dimension; that is not a valid inference of what we know, and it is not correct use of the term dimension.Cheers -- Sylas

Ned was wise enough to put the question marks there. There are speculative ideas about blackholes incorporating "wormholes" to another region in space, being a "whitehole"; but they are games with strange solutions to the relativistic equations, and not predictions of what happens in black holes in real life. It is not correct to say that the central singularity is in another dimension.There is a really excellent web site you should check out; Falling Into a Black Hole by Andrew Hamilton. It shows simulated movies of what you see as you approach a black hole; orbit a black hole, drop probes into a black hole, and finally fall into to a black hole yourself, all the way through the event horizon and right down to the central singularity, along with theoretical discussions explaining details we are discussing here. That is not a meaningful premise.We could speculate that the universe is like the skin of a hyperspherical bubble of some kind, but there is no such thing as "inner" or "outer" surfaces. You rather have a geometry in which our three dimensional space is treated as a hypersurface embedded in a higher dimensional space. However, this is not really a good idea; the geometry works without needing to require embedding into a higher dimensional space at all. It can be a useful aid to start thinking about what it means for a space to expand; by analogy with a balloon or something like that; but as soon as you start making concrete suggestions based on conventional intuitions uninformed by a thorough comprehension of Riemannian geometry and general releativity and other horrible things like that, you end up with nonsense.Cheers -- Sylas