My previous post describes the evidence for a rational agent based on an ordered universe created by the “Big Bang”. But if the laws of nature are so orderly, where does unpredictability come from? Where does uncertainty come from? We will need to know more about what we mean by “laws,” and why some of those laws might allow for some sort of non-deterministic behavior. Might some non-deterministic activity be evidence for an ongoing role for a rational power in the universe? But first, what are our most certain assumptions about nature? What is it that all of physics depends on? Leonard Susskind specifies three unconditional laws of nature (from The Black Hole War):
- The maximum velocity of any object in the universe is the speed of light, c. This speed limit is not just a law about light but a law about everything in nature.
- All objects in the universe attract each other with a force equal to the product of their masses and the Newton constant, G. All objects means all objects, with no exceptions.
- For any object in the universe, the product of the mass and the uncertainties of position and velocity is never smaller than Planck’s constant, h.
Susskind emphasizes, “There is no dispute . . . . They apply to any and all things – everything. These three laws of nature truly deserve to be called universal.” For the really picky reader, there are some additional qualifications that probably need to be added, but I’ll ignore those now to keep things as simple as possible.
To these three unarguably fundamental laws, Susskind would probably add the conservation of energy (energy is neither created nor destroyed; mass being a form of energy due to Einstein’s famous equation, E = MC2); the conservation of charge (charge is neither created nor destroyed; electrons and protons are examples of charged particles); and surprisingly, time reversibility or conservation of information. Susskind maintains that it is fundamental to the laws of physics that, in addition to predicting the future, the laws do not allow for an ambiguous past. In other words, information about the prior states of a system is never lost. He has successfully argued this point with Steven Hawking and apparently won. Roger Penrose appears to be a lone holdout in this debate about conservation of information. Time reversibility will prove to be a paradoxical factor in the laws of physics.
Speaking of Roger Penrose, he would probably add to this list as well. He rates our best scientific theories as ‘SUPERB’, ‘USEFUL’, or ‘TENTATIVE’. In the ‘SUPERB’ category, he places Einstein’s theory of relativity (both special and general relativity), quantum theory, Newton’s laws of motion and law of gravity, and Maxwell’s theory of electromagnetism. Into the ‘USEFUL’ category go the standard model of particle physics and the Big Bang theory.
Let’s look at some of the implications of these fundamental laws of physics for an orderly, rational world. The first fundamental law stating that the speed of light is the maximum speed for any observer is included in Einstein’s special theory of relativity. There are some remarkable features of the special theory of relatively. The constancy of the speed of light for all observers leads to conclusions that distances along the direction of motion must contract and time must slow down for any system that is moving with respect to another system.
This effect is symmetric with respect to two systems that are moving past each other at a uniform speed so that observers in each system will conclude that the other system is measuring shorter distances and slower times. However, if one system reverses direction, this implication of the special theory of relativity will have permanent consequences.
For example, if identical twins are born on earth and one of them is placed on a rocket to a nearby star and that rocket is moving at a speed close to the speed of light, then the space traveler twin will return to earth younger that his or her sibling. The effect of time slowing down is made permanent by the reversal of direction of the rocket. The space traveler twin will experience acceleration and deceleration that will break any motion symmetry between the two twins. This is called the twin paradox.
The surprise is that each observer in motion has his or her own time frame. With the twin paradox, it is possible for anyone who is willing to travel fast enough to move forward in time. The space traveler will return to earth at a time in the future compared to the traveler’s own clock or calendar. If one is willing to travel fast enough and far enough, one could actually return far into the future.
This effect has been measured in particle accelerators and in the effects of cosmic rays that strike earth’s upper atmosphere. The high energy cosmic rays that strike high altitude molecules will create exotic particles (muons) which normally decay so quickly that few would reach the earth. However, some of these particles are moving so fast that time is slowed down to the point where more of them can be detected at a lower altitude.
You might wonder if it’s possible to travel forward in time, is it also possible to travel back in time? The answer is no. Backward time travel world require traveling faster than the speed of light which is prohibited by the Einstein’s special theory of relativity, and Susskind’s first fundamental law above. That is a good thing because if one could travel back in time, causality could be violated: it would be possible to alter history (for example, think of the movie, “Back to the Future”). It is not even possible to send a specified signal at a speed faster than light. If one miraculously had such a device that could send a signal at greater than light-speed, and if that signal could be relayed back to its source, then a report of a future event could be received in the past thereby providing the option of avoiding the future event!
Even though special relativity makes time relative to each moving observer, it guarantees that time will always move forward, never backward. It thereby guarantees causality: causes will always precede effects. Causality is one of the fundamental guarantees of a rational universe.
From time to time, there are scientific theories or experiments that appear to show that the universe has the possibility of violating causality. One such possible implication arises in general relativity in the theory of black holes – stars so massive that not even light can escape. Another implication of a possible violation of causality arises in the quantum theory of entangled particles. Both of these situations imply that the universe has capabilities that are not made available through any normal activity. But even if the universe has the ability to violate causality, that ability is not available to its inhabitants and it is still not possible to send any message back into the past.
In fact, the mere possibility of a violation of causality in relation to black hole singularities led Roger Penrose to propose a cosmic censorship hypothesis which states that it is not possible to observe any physical process that will lead to a violation of causality. The sort of determinism in which time always flows forward is a key property of this universe. Yet this property is in direct conflict with Leonard Susskind’s assertion that the laws of physics must be able to be reversed. How will this tension be resolved?
Susskind’s law concerning the conservation of information is based on a fundamental assumption that the laws of physics are unambiguous with regard to the past. This is sometimes stated that the laws of physics are still true whether time runs forward or backward. This feature of scientific theory is necessary if we are to project events backwards to arrive at a beginning point. The obvious question then is why don’t we ever see time running backward?
In a previous post, I have framed my discussion of rational agency in terms of a contradiction between two concepts. One idea is that the universe is fundamentally governed by deterministic laws which include a provision for random action. I have called this concept materialism, but its main determining factor is a randomness which accounts for any observational results that are not strictly predictable. The other concept I have called a rational agent, but its main determining factor is directed, rational action that conforms to the deterministic laws. I have stressed that these are two extremes and that the truth might lie somewhere in between. So far in my discussion on science, I have described the Big Bang creation of the universe and special relativity. Both of these narratives intimately involve matter. Even if the rules governing matter are rational and rigorous, why does that imply a rational agent? And how do rational laws result in uncertainty?
All of the theories listed above – from relativity to quantum theory – are models of physical reality. That is, they describe physical reality using mathematical equations along with constraints or principles that are applied to the analysis of physical reality. The mathematics associated with each theory is an integral part of the narrative that explains why the theory is true. Without such a narrative, doubts would immediately set in if there were anomalous observations. For a well-tested and mathematically consistent theory, there are strong reasons to doubt the anomalous data.
For example, not too long ago some observations suggested that neutrinos could travel faster than light. There was an experiment associated with the Large Hadron Collider (LHC) near Geneva, Switzerland in which neutrinos were timed at about 60 nanoseconds faster than a light beam going a distance of 450 miles. If that observation had proved true, it would have been a significant violation of special relativity. The problem was eventually traced to a GPS synchronization issue between the two clocks used to time the trip, but resolution took several months. This episode illustrates both the confidence generated by a mathematically consistent, well tested theory and the provisional nature of any theory. The provisional nature of scientific evidence is one reason for looking at a gestalt of the evidence rather than relying too much on any one result.
As mentioned above, the special theory of relativity describes the way that different observers, moving at different speeds will view the same events. Mathematical equations define how clocks and rulers change when moving at high speed. These changes have been observed in particle accelerators: particles accelerated to high speed flatten out, like a pancake, and particle lifetimes increase in accord with special relativity.
The naïve question won’t go away: how is it that matter in the form of very small particles knows how to obey the laws of special relativity? Unless one thinks that the real world is a computer simulation (and some actually do think this), how do ‘inert’ particles know how to behave under the laws of physics? Either the particles are not so ‘inert’ or there is a rational power that enforces the laws of physics, or both. This is part of my evidence for panpsychism. Matter and consciousness are intimately bound together. Matter is knowledge made manifest. Our mathematical theories hint at the connection.
What our best theories don’t tell us is how physical reality really works, or as Stephen Hawking says (quoted by Jim Holt): “What is it that breathes fire into the equations and makes a universe for them to govern?” Or as someone once asked, “How does the electron know to follow the rules defined by the equations of magnetic force?” Holt adds, “How do they [the equations] reach out and make a world? How do they force events to obey them?” Our scientific theories are rational models of how the universe works. As such they are evidence for a rational process at work in the universe. But they are not the actual power that enforces the physical laws. That power lies outside our knowledge, but our best theories are pointers or signposts that indicate that the power is real.
My answer to these questions is that it is a rational agent that breathes the fire into the laws of physics and makes out of them a coherent world in which to live. In order to understand how that happens without recourse to any supernatural power, I will need to describe two kinds of uncertainty or unpredictability that are present in our empirical view of the universe.
The first kind is easily dispensed with. It is what Leonard Susskind calls experimental “sloppiness.” I think that is a bit unkind because what he means is the inability to keep track of all the minute details that are necessary for the prediction of a result. Think of a drop of ink placed into a glass of water and how it spreads out with apparent randomness. Theoretically, if we knew the positions and velocities of all the particles we could predict the spreading. Not only that, but we could reverse the spreading so that the dispersed ink coalesced into a drop and popped out of the water! This is what Susskind means by “time reversal” or conservation of information. But before information can be conserved, we have to know what that information is, and in complex systems, it is impossible to know all the variables that we would need to know.
What is important in the conservation of information is that it be theoretically possible to reconstruct the past, not that it ever be practical to do so. This type of unpredictability is caused by the observer’s lack of complete knowledge. But, as far as I can tell, there is no ordering power in lack of knowledge. So this type of uncertainty is not very interesting. (But I don’t mean to denigrate such useful scientific tools as stochastic modeling!)
Much more interesting from the perspective of conservation of information is the uncertainty that comes from quantum physics. This is a completely different kind of uncertainty. It is an unpredictability caused by the universe’s direct intervention in the outcome of any transfer of energy. If you’ve heard of Schrödinger’s cat or the “collapse of the wave function,” you already know what this is.
Schrodinger’s cat is the archetypal and somewhat hackneyed example. A live cat is placed in a box with a poison vial which can be broken by a single well-aimed photon that passes through a half-silvered mirror. A photon passing through a half-silvered mirror has a 50% chance of being reflected and a 50% chance of transmission. So there is a 50% chance that the vial will be broken and the cat poisoned and a 50% chance that cat will live. The example concludes by speculating that we won’t know if the cat is alive or dead until we look in the box. But, more dramatically, the story raises the question of whether the cat exists in a quantum superposed state of half-dead and half-alive! This is what distinguishes the quantum example from the first type of uncertainty which is due to lack of complete information: Schrodinger’s cat would be both dead and alive.
We never observe half-dead cats; so most physicists believe that quantum superposition never rises to the level of cats or anything else as big as a cat. That means that the photon wave function must collapse to a definite state before whole cats get involved. Most people believe that the cat is either dead or alive before the box is opened. (Lest anyone be troubled as to why the universe might get involved in choosing life or death for a cat, remember, it was the hypothetical scientist who set up the experiment!)
Oddly enough, science has not been able to resolve this deep puzzle about quantum physics. Lee Smolin, in The Trouble with Physics, calls it one of the “five great problems in theoretical physics.” Roger Penrose has written at least two books to put forward his theory that there must be some objective reduction in the wave function based on the laws of physics. The main reason that this problem has resisted solution is that attempts to test when the wave function collapses typically cause the wave function to collapse. There may be indirect evidence, however.
The indirect evidence to which I am referring is that the universe, by choosing an outcome in every transfer of energy, is actually adding knowledge to an observable process. We shall need to look for processes at the quantum level that concentrate energy or concentrate information that would not be expected from the law of increasing entropy. Some of this evidence will be found in my next post dealing with quantum coherence and quantum entanglement. The remaining evidence will be described under the topic of evolution when I look at biological processes that increase order and concentrate energy.
Supplementing and partially compensating for the lack of direct evidence is the philosophical perspective of objective realism. There are strong reasons to believe that the wave function does collapse even if there is no observer. This is the quantum physics version of the conundrum, if a tree falls in the forest and no one hears it, did it really fall? There are strong reasons to believe in the reality of quantum states and strong reasons to believe that the universe picks one of the possible quantum outcomes, but the evidence is circumstantial.
If one takes the point of view that the collapse of the wave function is a real event that is initiated by the universe (whether or not there are governing rules) then one has taken the position that the universe chooses one particular outcome among all the possible outcomes that are predicted by quantum theory. That means that anytime energy is transferred, at least one choice is involved and more often many choices are required. This is the basis for a fundamental ‘decisionality’ in the universe that underlies all activity. It is this fundamental decision process that prohibits any backwards movement in time. It is the reason that we only observe time moving forward. And ‘decisionality’ is evidence for rational agency.
Leonard Susskind confirms this position by insisting that, in order for time to be reversed, the quantum state must not be disturbed:
“Take the photon. When we run the photon in reverse, does it reappear at its original location, or does the randomness of Quantum Mechanics ruin the conservation of information? The answer is weird: it all depends on whether or not we look at the photon when we intervene. By “look at the photon” I mean check where it is located or in what direction it is moving. If we do look, the final result (after running backward) will be random, and the conservation of information will fail. But if we ignore the location of the photon—do absolutely nothing to determine its position or direction of motion—and just reverse the law, the photon will magically reappear at the original location after the prescribed period of time. In other words, Quantum Mechanics, despite its unpredictability, nevertheless respects the conservation of information.”
In Susskind’s narrative about information conservation, I sense an underlying agreement with Roger Penrose. It is the decision process associated with the collapse of the wave function that prevents time from running backwards and it is also part of the basic mystery of the law of increasing entropy. In order for the fundamental ‘decisionality’ of the universe to lead to rational agency, it must demonstrate the ability to perform activities that minimize entropy. We will see some of that evidence in my next post regarding lasers and superconductivity.
The inescapable conclusion is that the collapse of the wave function does indeed discard information: it concentrates information about the state of the universe; it eliminates possible energy states; it sets a limit on the increase of entropy. Quantum physics began by solving a profound puzzle about the energy spectrum. In the nineteenth century, the energy spectrum was considered continuous. If the energy spectrum was continuous, then there would be an infinite number of energy states and any heated object would radiate infinite energy. Everyone knew this wasn’t true, but it was Max Planck who postulated in 1900 that radiation energy was quantized in units that now bear his name. This one simple change limited the number of energy states and reduced the hypothetical infinite energy to a finite energy that was confirmed by experiment.
If we are to truly understand how the universe works in all of its magnificence, how it is able to produce both deterministic order and adaptable life, then we need to understand any process that limits entropy or has the potential of reducing entropy. That physical process is quantum physics.
These topics will be explored in my next post.