41–50 of 52 posts
Earlier quoted context omitted.
The big bang, unlike theology, tells us why distant objects are more red than close objects, why we can't see anything further than ~13bil light years away, why there is microwave noise everywhere, etc. The mathematics that describe all those things imply certain things about earlier cosmological history.
But still doesn't prove anything about where the universe "came from".
Source : http://en.m.wikipedia.org/wiki/Cosmological_natural_selectio...
Cosmological natural selection Smolin's hypothesis of cosmological natural selection, also called the fecund universes theory, suggests that a process analogous to biological natural selection applies at the grandest of scales. Smolin published the idea in 1992 and summarized it in a book aimed at a lay audience called The Life of the Cosmos.
The theory surmises that a collapsing[clarification needed] black hole causes the emergence of a new universe on the "other side", whose fundamental constant parameters (masses of elementary particles, Planck constant, elementary charge, and so forth) may differ slightly from those of the universe where the black hole collapsed. Each universe thus gives rise to as many new universes as it has black holes. The theory contains the evolutionary ideas of "reproduction" and "mutation" of universes, and so is formally analogous to models of population biology.
The resulting population of universes can be represented as a distribution of a landscape of parameters where the height of the landscape is proportional to the numbers of black holes that a universe with those parameters will have. Applying reasoning borrowed from the study of fitness landscapes in population biology, one can conclude that the population is dominated by universes whose parameters drive the production of black holes to a local peak in the landscape. This was the first use of the notion of a landscape of parameters in physics.
Leonard Susskind, who later promoted a similar string theory landscape, stated:
"I'm not sure why Smolin's idea didn't attract much attention. I actually think it deserved far more than it got."
Earlier quoted context omitted.
From the fine paper[1]: Finally, let us comment on potential testability of this model. As we pointed out, the simple model of cosmological perturbations, developed in Sec. 4 is already ruled out by cosmo- logical observations at > 5σ level, as it does not predict any deviations from scale-invariance. However, it is easy to imagine small corrections that could lead to a ∼ 4% deviation from scale-invariance, especiall…
I'm not sure of what a graviton is, but wikipedia tells me that it is not detectable by any current mean. I'd be tempted to say in light of this that their theory is not testable either. http://en.wikipedia.org/wiki/Graviton
Saying a scientific hypothesis is untestable "in principle" is a deathknell while untestable "in practice" is not.
First of all, it has been well understood for multiple decades that the General Relativity(GR) breaks down, and is no longer true, at mass/energy scales that are present inside of a black hole. This is known because physical quantities must be finite, but GR predicts the strength of a gravitational field inside of a black hole is infinite. If string theory is true (and I don't believe it is), then this would be a valid situation to apply it to, since we know that there is unknown physics at play inside of a black hole.
Furthermore, the standard big bang cosmology is based on the idea that the beginning of time is a "black hole in time", in the sense that as t->0, the strength of the gravitational field diverges to infinity. Thus, it has been well known for decades that GR is not a valid physical theory at very short time scales after the beginning of time (this would be the epoch of inflation[3]).
It is perhaps not apparent to the casual observer that this paper is based on a very bizarre sect within string theory, known as the "Holographic Universe", which according to Wikipedia "suggests that the entire universe can be seen as a two-dimensional information structure "painted" on the cosmological horizon". This is just a bunch of fancy words designed to blow smoke in your eyes, and the entire theory is sort of a joke as far as most physicists I know are concerned.
There are actually a number of strange cults within string theory, another one that is good for a laugh is the Anthropic Princple[4]. This theory claims that even though the 11 dimensional D-Brane that is folded into a Calubi-Yau manifold upon which string theory is based predicts trillions of possible universes, the universe we live in exists because it is the only possible one we could live in:
"the conditions happen to be just right for the existence of (intelligent) life on the earth at the present time. For if they were not just right, then we should not have found ourselves to be here now, but somewhere else, at some other appropriate time."
This kind of nonsense is why I left research in theoretical physics to purse computer science and programming, which truly is the cutting edge of science. There is a lot of valuable physics research going on in material science departments(for example), but the string theory department needs to constantly justify their funding by making extremely bold claims such as "what we perceive as the Big Bang could be the three-dimensional “mirage” of a collapsing star in a universe profoundly different than our own".
[1] http://en.wikipedia.org/wiki/Holographic_principle
[2] http://en.wikipedia.org/wiki/D-brane
I think this idea is almost certainly false, and it has it's genesis from a mostly discredited psuedo-physics theory called the holographic universe[1]. But at least there is a testable prediction! In my opinion, the fact that they offer a testable prediction merits a more thorough consideration of the claims. First of all, it has been well understood for multiple decades that the General Relativity(GR) breaks down,…
The Anthropic Principle is a common sense explanation to why our universe has a paradoxically perfect ("fine-tuned" by 120 orders of magnitude off what we would expect) cosmological constant that is just right for life and the universe to exist. It's somewhat horrifying, but I haven't seen a better explanation for fine-tuning. [1]
The holographic principle does not seem to be supported by a "very bizarre sect". In fact, it seems to be one of the better explanations for the black hole information paradox. [2]
Nima Arkani-Hamed dedicated a significant portion of his Messenger Lectures [3] (same lectures where Feynman delivered his famous series) to the principles that you dismiss out of hand as laughable above.
I'm a little depressed that the top comment is computer science > theoretical physics. Theoretical physics predicts quantum scale behavior to 11-digit accuracy. It's no joke.
[1] http://en.wikipedia.org/wiki/Cosmological_constant#Quantum_f... [2] http://en.wikipedia.org/wiki/Black_hole_information_paradox [3] http://www.cornell.edu/video/nima-arkani-hamed-quantum-mecha...
Earlier quoted context omitted.
The big bang, unlike theology, tells us why distant objects are more red than close objects, why we can't see anything further than ~13bil light years away, why there is microwave noise everywhere, etc. The mathematics that describe all those things imply certain things about earlier cosmological history.
But still doesn't prove anything about where the universe "came from".
As I understand the process, theoreticians will invent mathematical constructs that explain everything we have measured already, plus make predictions about something else we can test. If all of the testable predictions are verified, then we are somewhat safer in accepting any untestable predictions of the same model. Then, an expanded mathematical theory will be devised with new physical tests, etc. ad infinitum.
Earlier quoted context omitted.
..and theology does?
What I said: It doesn't provide any more believable answers than religion for me.
The fact that there is an ongoing process of scientific discovery that has continued unabated, while theological knowledge remains stagnant or even decays, is alone enough reason to give credence to even the most far-fetched theory that might one day have a hope of being tested.
To summarize, hard science like theoretical physics is not about beliefs or answers or end goals, it's about a continual process of expanding knowledge, guided outward by the imaginations of theoreticians.
This tends to confirm Lee Smolin's embryo-theory of cosmological natural selection. Source : http://en.m.wikipedia.org/wiki/Cosmological_natural_selectio... Cosmological natural selection Smolin's hypothesis of cosmological natural selection, also called the fecund universes theory, suggests that a process analogous to biological natural selection applies at the grandest of scales. Smolin published the idea in 1992 a…
Earlier quoted context omitted.
Ignorant question here, but is it not the case that the normal laws of physics don't apply at big bang time? Do we expect the laws of mathematics to still apply? Does anyone really have any clue about this stuff?
Yes, we expect the laws of mathematics to still apply. The laws of physics also apply, but we don't know all of them. For example Newtonian physical vs. relativity. Both are correct, but one only comes into play at high velocity or energy. Same with the big bang, there may be a more complete description of what happens that only comes into play at high energy. This doesn't mean the current laws don't apply, but rathe…
Classic. Making it up as you go along.....