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Science, Philosophy or Science Fiction?
on 2 September 2012
At first, an editorial comment: At the beginning and the end of each chapter, the list of funding supporters is read out, eight times in total, and this costs one star, I'm afraid.
The 2 DVDs provide 4 chapters, being an extract of the book, which necessarily provides a larger span of physics than these DVDs can.
As previously, Brian Greene has a very alluring, thrilling way to present his thoughts to the public. Experiments, not all of them on the basis of physics, but using every trick in the book, too often distract from this physical basis. Fortunately, Greene often starts with the classical physics, which he also presented on his first DVD ("The Elegant Universe").
Let's look at some details:
1: What is Space?
The opening suggestion is a very important one: Let's remove all matter from space. After presenting the development of our insights to "space" or, later, to spacetime, the jittery realm of quantum mechanics and the properties of their interaction with matter, it then turns out that there is no such thing as "empty" space, as there is a Higgs ocean permeating space (a theory which is meanwhile confirmed). The effect of dark energy accelerating the observed expansion of space remains an unsolved puzzle. Physics is then left behind with the suggestion that information would be encoded on the surface of a black hole (the event horizon?) and, from this idea, the entire 4-dimensional spacetime might be described as a hologram from the 2-dimensional outside of the universe.
At the bottom line, esp. after the far-out idea of the hologram, the question on "space" remains open.
2: The Illusion of Time:
Here, after the issue of measurement and relativity of time, the first part is largely dedicated to the question of time symmetry of physical laws. It takes some of that time until the answer is provided, however not as a statement, but as a theory: It's the entropy, taking the boundaries of any given system into account. The 2nd Law of Thermodynamics is not even mentioned, according to which the entropy in a given system can only increase (or remain steady) with time, hence the very core of this law being time's arrow.
Time, according to Greene, might be just an illusion. Here, I quote one of my professors and suggest that if you believe that, just sit down in front of a group of rhinos going wild, then you can decide.
A really interesting analysis is missing: Considering the development of the Big Bang, looking backwards in time, and a black hole with a supermassive star collapsing, the processes are very similar; however, the Big Bang has the lowest possible entropy, a black hole the highest. These assessments belong to the most difficult ones there are, which might be the reason why they are not taken up here.
Of course, time travel is discussed. Whereas a time travel to the future might be possible when near-luminal speed became possible (the shown visit to a black hole is not the only option), the same does not apply to travelling backwards in time, despite the wormhole scenario might suggest it (in contrast to Greene's presentation in his previous work!).
At the bottom line, you are left with a maze, yet with a few hints to the correct properties of time.
3: Quantum Leap:
This chapter is the gold nugget of the 2 DVDs! It might be the greatest paradox that, although based on the uncertainty principle, all quantum mechanics' equations and predictions are confirmed with maximum certainty. The most recent research on quantum entanglement is shown with great detail, up to and including teleportation.
At this point, it is getting weird again: Greene is suggesting that teleportation by entanglement might become possible. He states (quite correctly!) that there are more particles in an average human than stars in the observable universe which quantum states need to be stored and then processed for entanglement. Despite the progress in computer technology, the tremendous amount of storage capacity is unrealistic to achieve in the foreseeable future, even considering the growth in capacity being extrapolated further.
The question why quantum states are not effective on larger scales has nothing to do with a multiverse, allowing all states to exist in parallel, but with superposition or, more precisely, the interactions of quanta with ever larger particles, atoms, molecules etc.
At the bottom line, apart from the very last suggestion, you get a pretty good impression on quantum mechanics.
4: Universe or Multiverse?
Since Alan Guth has proposed an inflation period within the first Planck times of the Big Bang, the essential part of the mechanism to start/ stop the process remains as unresolved as the high superluminal speed of this inflation. Brian Greene (and e.g. Michio Kaku) have proposed earlier that only empty space could expand faster than light, which takes us right back to the first chapter: Could there be such a thing like empty space?
Ignoring these subjects entirely, the next thing we learn is that the "fingerprint" of the inflation can also be seen in the Cosmic Microwave Background Radiation (CMBR). However, even the closer analysis of the WMAP data certainly have confirmed the temperature and fluctuations of the primordial plasma (from COBE data) and also revealed the distribution of curvature, dark and baryonic matter as well as dark energy, but the superluminal inflation remains a theory.
Another part of the theory, the "repulsive gravity", has been confirmed by the Ashtekar-Bojowald approach using Loop Quantum Gravity, the method having been mentioned, yet not described in further detail in the book.
Coming to the dark energy and comparing its value to the prediction (!) of theoretical physics (Quantum ElectroDynamics (QED)), the significant mismatch between the two leads to the assumption that this would point directly at the multiverse theory, where the values "must fit" in one of those multiverses. This, in turn, would leave us with a "try and error" approach to establish physical laws describing our universe.
Finally, the many dimensions of string theory and their almost infinite, not yet identified shapes are taken as another support for the multiverse theory. Again, as before, once the mathematics are not understood at a fundamental level, some physicists prefer to take a backdoor to evade the problem, leaving us with a theory that is, at best, a philosophy.
At the bottom line, this chapter is almost entirely fiction, as the physical realm is clearly left behind.
My impression is that there is a growing tendency that mathematics governs physicists, leading them to blind application of all possible variations of a formula, the stranger the better. It used to be the opposite: Observation and experiment governed the scene, using mathematics as tools to appropriately describe Nature. Some subjects (like time travel or a multiverse) appear to be sufficiently thrilling to be pursued even though they are not consistent with fundamental laws of physics; it could almost be called a mental scotoma.
I'm extremely reluctant to recommend the DVDs. Instead, the book provides more insight to some of the basic physics, giving you a better distinction from the realms of philsophy or science fiction than the DVDs.