Category Archives: Science

The Uncertainty Principle and Us

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It’s difficult to discuss physics if you aren’t a physicist or don’t understand the math involved. Nevertheless, what physicists tell us about the world is so strange that it’s hard not to discuss it sometimes, whether we understand it or not. (The brilliant physicist and all-around cool guy Richard Feynman once said that nobody understands quantum mechanics, but some understand it better than others.)

There are philosophers who specialize in the philosophy of physics and aren’t shy about discussing physics at all, among themselves and with physicists. One of these philosophers, Craig Callender, has recently written two interesting articles for the New York Times. In these articles, Callender argues that Werner Heisenberg’s uncertainty principle, probably the best-known part of quantum mechanics, shouldn’t be as famous as it is. 

Heisenberg was one of the founders of quantum mechanics. He published the uncertainty principle in 1927. If you look up “uncertainty principle” now, you’ll find statements like this: “The position and momentum of a particle cannot be simultaneously measured with arbitrarily high precision” and “The uncertainty principle is at the foundation of quantum mechanics: you can measure a particle’s position or its velocity, but not both.”

Well, here is Callender on quantum mechanics:

[Quantum mechanics is] a complex theory, but its basic structure is simple. It represents physical systems – particles, cats, planets – with abstract quantum states. These quantum states provide the chances for various things happening. Think of quantum mechanics as an oddsmaker. You consult the theory, and it provides the odds of something definite happening….

The quantum oddsmaker can answer … questions for every conceivable property of the system. Sometimes it really narrows down what might happen: for instance, “There is a 100 percent chance the particle is located here, and zero percent chance elsewhere.” Other times it spreads out its chances to varying degrees: “There is a 1 percent chance the particle is located here, a 2 percent change it is located there, a 1 percent chance over there and so on.”

According to Callender:

The uncertainty principle simply says that for some pairs of questions to the oddsmaker, the answers may be interrelated. Famously, the answer to the question of a particle’s position is constrained by the answer to the question of its velocity, and vice versa. In particular, if we have a huge ensemble of systems each prepared in the same quantum state, the more the position is narrowed down, the less the velocity is, and vice versa. In other words, the oddsmaker is stingy: it won’t give us good odds on both position and velocity at once.

Callender then points out that he hasn’t said anything about measurement or observation:

The principle is about quantum states and what odds follow from these states. To add the notion of measurement is to import extra content. And as the great physicist John S. Bell has said, formulations of quantum mechanics invoking measurement as basic are “unprofessionally vague and ambiguous.” After all, why is a concept as fuzzy as measurement part of a fundamental theory?

Callender later shares another quote from J. S. Bell (considered by some to be the greatest physicist of the second half of the 20th century):

What exactly qualifies some physical systems to play the role of “measurer”? Was the wavefunction [the quantum state] of the world waiting to jump for thousands of millions of years until a single-celled living creature appeared? Or did it have to wait a little longer, for some better qualified system … with a Ph.D.? If the theory is to apply to anything but highly idealized laboratory operations, are we not obliged to admit that more or less “measurement-like” processes are going on more or less all the time, more or less everywhere?

When physicists use their instruments to measure a subatomic particle’s position or momentum, the instruments affect the particle. It’s the interaction at the subatomic level between the instrument and the particle that’s important, not the fact that the interaction has something to do with measurement, observation, mental energy or human consciousness. We aren’t that important in the vast scheme of things.

Viewing the theory of quantum mechanics as a cosmic oddsmaker may seem unhelpful. We want to know what’s going on at the subatomic level that results in the theory calculating certain odds. Heisenberg thought physicists shouldn’t even think about an underlying reality — they should simply focus on the results of their observations. But some (many?) physicists working today believe that quantum mechanics is an incomplete theory that will eventually be replaced by a more fundamental theory, possibly one that explains away the apparent randomness that exists at the subatomic level (that’s what Einstein thought too). Their hope is that uncertainty will one day be replaced by certainty, or something closer to it.

If you do a Google search for “uncertainty principle consciousness”, you’ll probably get more than 8 million results. If you search for “uncertainty principle measurement”, you can get more than 32 million. Professor Callender thinks those numbers should be much, much smaller.

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This is Callender’s first article in the Times:

http://opinionator.blogs.nytimes.com/2013/07/21/nothing-to-see-here-demoting-the-uncertainty-principle/

Here he responds to questions and criticisms from readers:

http://opinionator.blogs.nytimes.com/2013/07/25/return-of-the-stingy-oddsmaker-a-response/

Time Reborn: From the Crisis in Physics to the Future of the Universe by Lee Smolin

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The theoretical physicist Lee Smolin has written 4 books. I’ve read 3 1/2 of them.

His first book, The Life of the Cosmos, applied the theory of evolution to cosmology. Smolin suggested that our universe might be a good home for life because universes breed new universes, which differ somewhat from their parents. Over time, a universe with lots of black holes will generate a number of new universes with lots of black holes, and universes with lots of black holes tend to be hospitable for life, since their fundamental constants (like the strength of their subatomic forces) have values that permit life to evolve.

His next book, Three Roads to Quantum Gravity, was too technical for me, but I did finish his 3rd book, The Trouble With Physics. In that one, he argued that string theory is much too popular among physicists, since it isn’t a proper scientific theory. It’s too speculative and might never generate testable predictions.

Now there is Time Reborn. This is a kind of sequel to Smolin’s earlier books. He still subscribes to the evolutionary views presented in The Life of the Cosmos, but his principal thesis now is that time is real. In fact, time is more real than space. This contradicts the common view among physicists and philosophers that space and time are the four dimensions that make up “spacetime”. The standard view among physicists is that all events, whether past, present or future, are equally real. There is nothing special about the present moment. In fact, our perception that time passes is an illusion.

Smolin argues that this consensus view of the universe as a “block universe”, in which all moments are the same, is a mistake. He agrees that the laws of physics and the equations that express them can run forwards or backwards, but only on scales smaller than the universe as a whole. The planets could revolve the other way around the sun, just like clocks can run in reverse. But the universe as a whole has a history that is real and a future that isn’t determined. Smolin thinks that treating time as real might help resolve certain issues in physics, such as the “arrow of time”, i.e., the fact that certain processes always go in one direction (entropy tends to increase in isolated systems).

Professor Smolin tries to explain how his view of time fits with Einstein’s special theory of relativity (in which temporal properties are relative to an observer) and how something can act like a particle and a wave at the same time (as shown by the famous “double-slit” experiment). I don’t know if those explanations or some of his other technical explanations make sense. But it was reassuring to read a book by a reputable physicist who believes that time is real, physicists have overemphasized the importance of mathematics in understanding the universe, and there is a reality beyond what we can observe. Smolin also believes that there are probably more fundamental, deterministic laws that underlie quantum mechanics. I believe that’s what Einstein thought too.

Time Reborn veers into philosophy at times. There is much discussion of the Principles of Sufficient Reason and the Identity of Indiscernibles. The book concludes with some comments on subjects that aren’t physics, like the nature of consciousness. Smolin’s philosophical remarks are relatively unsophisticated. I assume his physics is better.

Even if he’s wrong about the reality of time, however, I enjoyed the book. For one thing, I can now see how two particles at opposite ends of the universe could be “entangled”, such that a change to one would automatically result in an immediate change to the other. Space might have more dimensions than we recognize. In another spatial dimension, the two entangled particles might be very close neighbors, making what Einstein called “spooky action at a distance” (“spukhafte Fernwirkung“) less mysterious. That makes me feel a lot better.

Would You Forget About It, If You Could? (Part 2)

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Last week, I wrote about some scientists who have erased memories by injecting a drug into the brains of rats (our memory appears to work the same way as rat memory, but nobody is currently injecting propranolol into human test subjects). 

Now some other scientists have reported the ability to create memories in rats by injecting a certain kind of virus into their brains. The virus affects the creation of a protein that underlies the storage of memories. In this case, the rats were made to remember a certain environment as being painful, even though they had never experienced pain in that environment. 

Erasing real memories. Creating false ones. We’re a long way from our memories being manipulated like a character in a Philip K. Dick story (“We Can Remember It For You Wholesale”). But what’s a nice rat to think about its memories these days? Did I have that excellent cheese yesterday or not?

http://www.abc.net.au/science/articles/2013/07/26/3811591.htm

The Future Gets a Little Closer

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The British government has announced it will invest 60 million pounds to support the development of a “spaceplane”. This will be a spacecraft that can take off and land at an airport, just like a jet plane. But it will have the ability to escape the earth’s atmosphere, delivering passengers and 16 tons of cargo to space stations orbiting earth.

As planned, the spaceplane won’t need to carry lots of heavy fuel when it takes off, like today’s rockets have to do. It will use an extremely efficient engine that allows it to reach Mach-5 (five times the speed of sound) using oxygen from the earth’s atmosphere, and then use a small amount of on-board oxygen to reach Mach-22 in space. The technology has been proven in the lab. Now an actual spaceplane needs to be built and tested.

The article below suggests that the spaceplane technology might eventually be used to make regular air travel faster, allowing tourists, for example, to fly from England to Australia at an average speed of 2,500 miles per hour (i.e. fly 10,000 miles in just 4 hours). That would be 300 miles per hour faster than the fastest military aircraft, the SR-71 Blackbird, has ever flown (according to public records).

A futuristic passenger plane would have to accelerate and decelerate rather slowly, however. Otherwise your Aunt Sally and Uncle Bob would experience a g-force like an astronaut does.

It doesn’t exist yet (and isn’t expected to start flying until 2019), but it still looks really cool:

SkylonTakeOff

http://www.guardian.co.uk/science/across-the-universe/2013/jul/17/sabre-rocket-engine-reaction-skylon

Would You Forget About It, If You Could?

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Everyone has some bad memories. Would you erase a bad memory if you could?

That’s the premise of Eternal Sunshine of the Spotless Mind, a wonderful movie from 2004 in which Jim Carrey (playing a serious role) and Kate Winslet use a new technology to erase their memories of each other. As you might expect, things don’t go as planned.

The idea that we might get rid of painful memories raises some interesting questions. Is it right to erase what is part of ourselves, something that contributes to making us who we are? Don’t bad memories help us avoid making the same old mistakes again? Does having painful memories help us appreciate our happy memories and the good things that happen to us?

We might have to consider such questions in the relatively near future. Scientists aren’t yet ready to erase our memories, but some of them are working on a way to make bad memories less painful. It isn’t clear from the article below whether the details of a memory can be changed, or whether it’s the emotion associated with a memory that can be changed. What is clear is that ingesting a certain drug (propranolol) within a window of time after a memory is formed or after it’s recalled can change the memory’s emotional impact. In theory, a traumatic memory can become relatively benign. 

The premise of the article is that this method will work because it takes a certain amount of time for a memory to be “consolidated” (added to our long-term memory), and each time we recall a memory, it is “reconstituted” (reconstructed from some underlying arrangement of the stuff in our brains). If the drug is administered at the right time, the process of consolidation or reconstitution can be modified.

Perhaps it’s a sign of having a “half-empty” personality, but I’d be more than willing to remove a few bad memories or make some of them less powerful. There doesn’t seem to be much difference between getting rid of a bad memory and avoiding a bad situation that you will later remember.

In fact, one of the benefits of being dead (there aren’t a lot, but there are at least a couple) is that you don’t have to remember how you screwed up that time or what that so and so did to you. Even if there’s an afterlife (don’t count on it), you won’t have to remember all the bad stuff unless you’re in hell — or heaven isn’t what it’s cracked up to be.

http://www.technologyreview.com/featuredstory/515981/repairing-bad-memories/