liarliarpof

What is dark matter doing here? The Backstroke???

No.

Turn towards the budding discipline of 'Molecular Phylogeny'. It is, at last, the first 'Falsifiable' Theory regarding such matters.

Dimensions. A point is 'dimensionless', or Zero. The line is constructed by aligning infinite #s of Zero-dimensional points. So how does the line acquire a 'dimensionality' of One? And so on toward the 'plane' & upwards.

Just a few things which may help: 1)There is the 'natural' system of units in which c=1, and is dimensionless. A device to simplify calculations in which c crops up like measles! The trade-off, however, is that there is no 'table' to easily return to mks, etc. It's a bit sticky. 2)The question of its absolute value is certainly valid, but far more intriguing is how does it come to be that two observers, one at rest and the other spinning, zooming, and twirling in any which way, measure the speed and always get the same, exact result? 3)Finally, an anectdote(true story). A prominent physicist once toured the 'Clock' of all clocks deep within a mountain in Colorado. He remarked, "So this is where the 'gold standard' of time is set, eh?". His guide matter-of-factly replied, "No. This is where we measure a thing which you, in turn, call 'Time'. "What's in a number? That which we call Time, by any other value would 'smell as sweet'. Exactly!"

I've found that one way to better comprehend the 2nd Law is to 'blend' (Macroscopic)Thermodynamics with (Microscopic)Statistical Mechanics. Thermo. states that, for a closed system, the entropy can either remain constant or increase. Shift to SM for the definition of entropy, S=k(logW), and the 2nd Law can be expressed as: dS/dt>0, or dS/dt=0. The tricky and rather tedious part is that 'W' is the total # of ALL POSSIBLE (quantum) states of the system.

ajb: The spin-2 attribute of the graviton arises from the quadrupole character of gravitational waves, as I understand it.

Oi Gevalt!!

Genuine 'Science' is not mean - 'Scientists', on the other hand....

Polchinski's response is not unexpected. In his Intro, Smolin quotes him (after having been asked to give a talk on "Alternatives to String Theory") that his first reaction, he(Pol) said, "was that this was silly, there are no alternatives...All good ideas are part of string theory". Smolin even states that, " ...just by raising these issues, I will anger some of my friends and colleagues...I can only insist that I am writing this book not to attack string theory or those who believe in it, but out of admiration for them and, above all, as an expression of faith in the physics scientific community." We should hope such 'faith' is not misplaced, lest the ship drifts dangerously close toward dogmatic waters.

For a very readable, thought-provoking book, try 'The Trouble With Physics', by Lee Smolin.

This 'Show Me The Money!!' ploy by Intelligent Design promoters is already tiresome and haggard. If you are genuinely interested in the science of it, check out 'Molecular Phylogeny'- The long sought TESTABLE Theory of Evolution, now at hand.

Back to the original subject- The Moon. Why send humans back? Been there, done that. Do we want to double check that Junior and Moon Maid were not hiding from us the last time? Just ask Diet Smith. A far too costly & dangerous gambit for a meager payout. Hell, we remain blissfully ignorant of what lies beneath > 90% of the oceans! Who fabricated and fitted those blinders upon our heads? It's time to snap out of it, folks! Perhaps fund a modest institute for OCLD (Obsessive-Compulsive Lunar Disorder) research?

A suggestion: Take another hard look at Newton's Third law, this time within the framework of General Relativity.

Think of it in terms of a sweeping generalization of Newton's Third law: The effect of the Sun's gravitational field upon a photon is indeed 'demonstrable'. Therefore, there must be an equal but opposite 'reactive force' exerted by the photon upon the Sun. But, as ajb states, it will be small to the extreme! I realize such 'semi-classical' reasoning is quite vulnerable, but if one deeply ponders the Third law, it's as if Newton, in the most vaguish of ways, foresaw extensions of his 'laws', such as GR.

Check out the Wiki piece on, 'Molecular Phylogeny'. Though more 'top-down', you may find it enlightening.

Gravitational waves are solutions of GR equations typical of a field theory. The concept of the graviton is a reasonable proposition in the attempt to quantize the field, given successes in other field theories. Thus far, the graviton remains an unobserved strategem, so as ajb points out, they may not be needed for a QGR theory.

Is 'transition' the word you seek? {E.g., Transition selection rules & probabilities, 'allowed' transitions, 'forbidden' transitions, etc.}. In dipole radiation, for instance, the theoretical differentiation between emission and absorption is simply a matter of +/- matrix elements.

Huzzah! (Reminiscent of a recurring skit on early SNL- 'Bad Theatre', hosted by Dan Ackroyd.). To paraphrase Einstein, 'When I set out to solve a problem, the first 99 attempts are usually wrong. If I am lucky, the hundredth one may be correct'.

Thank you, swansont, for clarifying the 'E=mc(2)' issue (The equation is correct if 'm' represents the relativistic mass, not the rest mass). And Kudos to michel123456 for reminding us of The Scientific Method, the 'litmus test' by which ideas and concepts are elevated to 'Theory' status, which seems to be conveniently ignored in certain cases these days. I suspect GR will continue to hold up to future tests (within its limitations, of which Einstein was keenly aware). Consider this: QM comes in various 'Interpretations', whereas GR is BRAND NAME ONLY!

A bit of pretzel logic: Consider the so-called 'God Particle'. This re-dubbing of the Higgs is usually attributed to Leon Lederman. The fact is, by the words of Peter Higgs himself, Lederman actually referred to Higgs' elusive construct as, "That Goddamned Particle!". If the Higgs is damned, at least Lederman believes that God did it and, by implication, must therefore exist.

The statement, "Humans know nothing", is a logical antinomy. The simple use of the word 'know' self-negates the proposition ab initio.

If you like Sir Roger's work, perhaps consider simply moving on to his 2004 book, 'The Road To Reality'. Godel receives rather short schrift, but there is much rich fodder in this 1,000p. tome. For a well done, and quite accessible introduction to Godel & his work, try Rebecca Goldstein's outstanding book, 'INCOMPLETENESS The Proof and Paradox of Kurt Godel'.

"Introduction to the Quantum Theory", David Park

This is reminiscent of Galileo's 'result', after his attempts to measure the speed of light using men with lanterns on distant mountaintops: "Extraordinarily fast, if not instantaneous."