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Third attempt at posting a topic - this has happened to me before.

I have been thinking lately about uncaused effects in QT. Particularly I have been thinking about ways of avoiding infinite regress or closed causal loops.

As I understand it, the Casimer Effect is uncaused, as is Hawking Radiation.

1. Is this so or could these have causes we cannot detect or simply not understand?

I would appreciate someone setting me straight.

On a seperate note:

2. Are there an infinite number of points on a one inch line?

And..

3. If it is possible for time to extend infinitely into the past, how can an infinite number of seconds have passed for us to be experiencing this present second? Please someone tell me what I am missing - it's driving me mad.

Blacknad.

Hi Blacknad,

Three whacks? I've had this kind of problem before. Usually only take two. Lets see how this one goes.

I am not exactly sure what you mean by "uncaused effects." As a result of this lack of understanding I don't see where infinite regress or closed causal loops come into the picture.

The Casimir Effect is caused by a resonance pervasive energy fields between separated but nearby objects. The effect was predicted bt Hendrik B. G. Casimir (1909-2000) in 1946. This effect was detected two years later in Amsterdam. In a geometric analogy think of space as being a flat plane at a large scale view. At a close scale view it is frothing and foamy because of the vacuum energy. This quantum foam is what causes the effect.

Hawking radiation was proposed bt Stephan Hawking in 1974. Here, again, this is like the Casimir effect in that the blackhole does not do the radiating. The vacuum foam that is usually in a constant state of rapid flux is stressed by the enormous gravity of the hole. This 'boosts' the virtual particles of the foam so that they become real particles. This effect has not been observed. If it, in fact does exist, it would be caused by the gravitational field associated black hole.

Cause and effect are difficult physical and philosophical problems. David Hume (1711-1776), the Scottish philosopher, discussed this in 1739 he wrote a work entitled "A tretise of Human Nature", where he goes on about cause and effect. He holds that our beliefs concerning cause and effect, to a great extent, depend on social custom, sentiment, habit and so on. In other words, most of what we think of as cause and effect are pure nonsense.

On the more physical side there is Einstein's take on cause and effect. In the first place a cause must normally precede an effect. Two events that are simultaneous cannot have a cause and effect relation. Simultaneity is one of the major issues in special relativity.

There is a tricky part in SR having to do directly with causality and the speed of light. Suppose that you have a cause that produces and effect by sending, say, a signal. Suppose further that the signal travels faster than light. Some simple calculations will show that there are intertial observers who will see the effect before a cause. This observer would not be moving faster than light. Not only is the speed of light the limiting velocity, but it is also required to have normal causality.

Your second and third questions are largely mathematical. The short answer to two is yes. The short answer to three is huh?

OK, in math a set is infinite if it can be placed into one-to-one onto correspondence with a proper subset of itself. You just can't do this with a finite set. The usual example is a mapping from the natural number {1, 2, 3, ...} onto the even natural numbers {2, 4, 6, ...}. The mapping is specified by the n-th natural number goes to the n-th even number. This mapping is one-to-one and onto and the even numbers are a proper subset of the natural numbers, hence the natural numbers form an infinite set.

It gets more confusing. There are orders of infinity. The natural numbers, in a sense, form the 'smallest' infinite set. The real numbers form a much larger set. The continuum hypothesis states that there are no intermediate infinities. There are larger ones.

The whole theory of transfinite numbers is an interesting topic in mathematics that I could go on at length about, but I get the feeling that this is not what you are asking.

Try this notion on for size: consider an infinity that is a-temporal and a-spatial. An a-temporal infinity is one where infinite duration is not an issue. The same for a-spatial, it is infinite, but not in the sense of infinite space. What we noramlly think of as time and space may not actually be infinite, but rather embedded within an atemporal, aspatial infinite context. This is the sort of thing that Suskind, Steinhardt, Linde and many others interested in cosmology are attempting to get at. The vote is definitly not in!!

Dr. R.

Dr. R. goes one way ... I'll go another.

We are fine on Q1 but with respect to Q2, if string theory is correct, or space is quantized, then there are no points in the universe and a line might be described as consisting of a finite number of space quanta, perhaps a Planck's width each.

With Q3 my answer would be that we haven't a clue what time is ... and ... that time does not exist. What Einstein describes is a single entity named space-time. Time has no meaning without space any more than length has any meaning without time.

If we posit that space came into existence at the big-bang then we must posit that time did too. That does not mean there were not other space-times before the current one. But it does mean that our current understanding of math and physics won't get us there.

Thank you both for responding. Very helpful.

Dr. R. - What I am trying to understand with uncaused causes is simply that if they exist within the universe then there is no reason to believe the universe needed a cause. I suppose that even if everything in our experience does have a cause, we still may not be able to extend that principle to the creation of the universe. If the universe was uncaused then we can safely do away with an infinite regression of causes that leads some people to posit the 'first cause'. Does the universe need a cause - or is this a nonsense question? Does the 'No Boundary Condition' state that the laws of physics extend back beyond the start of the universe? What is the consensus on the boundary condition?

Please excuse my ignorance, especially with the next question...

Does infinity exist in the real world or only as an abstract concept?

Dan - if space is quantized then it gets rid of a few philosophical paradoxes, like the impossibility of traversing a distance made up of infinite points.

Does that mean that all movement is teleportation from one space quanta to another, or am I just being silly now?

Blacknad.

I think we can pretty definitely say, at least within the constraints of our understanding of physics, that there are indeed uncaused events.

That this might be the case was one of the biggest problems Einstein faced and led to his famous "god doesn't play dice" statement. And yet everything we have found in the lab since seems to indicate that there is an element of chance.

Consider what is meant by "spontaneous symmetry breaking."

You are not being silly. There are lots of places where our understanding of things runs into a brick wall seemingly limited by brains created to keep us from becoming leopard food.

What we do know, I hope you are sitting down, is that electrons do not orbit the protons and neutrons in an atoms nucleus. That pretty picture you were shown in school is not reality. Electrons go from place to place, apparently instantly, without ever traversing the space between. The "orbit" is really just a graph of the probability of finding the electron at any particular location. Breathe!

Does infinite exist? As a mathematical construct yes. As a physical reality I am not sure the word has any meaning.

DA wrote:

"That pretty picture you were shown in school is not reality. Electrons go from place to place, apparently instantly, without ever traversing the space between."

I'd heard that before but do you think they travel at the speed of light?

Thanks Dan.

No shock with that one. I understand (as much as any fool can) how this works. It surprises me how many people still think that electrons are little planets orbiting the sun.

An apt example:

http://education.jlab.org/atomtour/listofparticles.html

I suppose it is much more intuitive and easier for our 'IS/OR' minds to comprehend. We don't do 'IS/AND' very well. It's a peculiar result of Western philosophy - Eastern mysticism has always found it easier to deal with 'IS/AND' which allows the (fallacious in my opinion) Tao of Physics. It is funny though that the Eastern mind was closer to the actual science than the Monotheisticly & Greek Philosophy driven Western mind. The East had no problem believing that something could exist in two apparently contradictory states. But kudos to Democritus in 450BC for coining the term atomos (uncuttable).

"He held that all things were made of atoms, that all atoms were exactly alike, and things which appeared to differ in quality, differed only in quantity and arrangement of atoms. All things were caused by the whirling motions of these atoms through the void. He denied the existence of the gods and other forms of mysticism becuase, he reasoned, if everything is made of atoms then this should include gods. They would then be nothing any more supernatural than anything else. There was also no reason why the "mind" could not be explained in physical terms according to his philosophy."

Talk about a man before his time. His thinking was totally different to anything else during his time. Incredible. I think it's particularly his idea that the mind could be described in physical terms that amazes me - it was such a counter-intuitive jump.

Thanks for taking time to answer my questions.

Oh and can anyone give any examples of spontaneous events other than spontaneous symmetry breaking?

Blacknad.

Post deleted by dr_rocket

Hi Blacknad,

A spontaneous event is something that happens all by itself. If you have an isolated system the only processes that can take place are those for which entropy increases. There are countless examples. My favorite is the Joule (Gay-Lussac) expansion of a gas.

Last night I was at a cosmology lecture and the speaker was less than wonderful. So rather than be rude and walk out, I did some creative wool gathering. I was thumbing through my notebook and I ran accross an old entry. This, in turn, called to mind part of your original post about "uncaused effects in QT". It occurred to me that I may not have seen what you were on about. I forget where this quote came from, perhaps M. Born (I take lousy notes these days.)

On the Complementarity Principle: "In atomic phenomenon it is not possible to acheive simultaneously a rigorous localization in space and time and a rigorous causal description. Space-time localization and causal description are complementary. They represent different aspects of reality which cannot both be rigorously and simultaneously defined. It is not impossible that atomic processes should be connected by strict relations of cause and effect. It is, however, impossible to define accurately in space-time a series of events that are causually related. Complementarity does not outright reject causality, but is a compromise between rigorous causality and free-will."

Complementarity, or duality, is one of the three legs of the base of QT. The other two are, of course, quantization and indeterminacy. This is the tripos that the quantum theory sits on.

Well then, was that closer to what you had in mind?

Dr. R.

P.S. That only took two tries, but at least I got two posts out of it!

TNZ asks:
"do you think they travel at the speed of light?"

Personally no. I think it is absolutely instantaneous or the way I would prefer to phrase it as "not happening in our space-time."

This is pure speculation on my part but I believe that our initial anthropomorphic approach to all problems gets in the way. Just because the habitat in which we exist have three spatial and one time dimension says nothing about the habitat of the electron. To assume they are the same may be a rational starting point. But there is no evidence to support it.

And Morgan's Law is: "That which renders us less important is more likely to be true."

Edited out duplicate.

Blacknad.

Yes, definitely, thanks.

My immediate question is (and please bear with my clumsy thinking), although it may be impossible to link effect to cause in practice - as it is impossible to define both position and momentum of a photon - is there any other way to get at the truth? Just as we know theoretically that it is impossible for a photon to have position but no momentum (I think) - can we not come to a theoretical knowledge that it is impossible for an effect to be uncaused?

I am very conscious that I am trying to grasp at concepts that are beyond me, but I have to try.

And just to check, we are talking about the creation of something out of nothing, 'creatio ex nihilo' i.e. falsifying the philosophical statement, 'ex nihilo nihil fit'.

And I would have thought that it takes some degree of talent to be able to make a cosmology lecture boring

Blacknad.

- This is my second attempt to post this. I don't like the new forum software - it is incredibly buggy.

How frustrating - that first post wasn't there a minute ago. There was no second page to this thread.

Blacknad.

Dan,

Doesn't your law run into problems with Quantum Observation?

Or is 'collapsing wave functions through observation' an exception that proves the law?

Blacknad.

Blacknad wrote:
"I am very conscious that I am trying to grasp at concepts that are beyond me, but I have to try."

Actually you are trying to grasp concepts that are beyond everybody. That is why the effort to understand belongs to the most brilliant of those among us. A category to which I do not, alas, belong. But why not aspire to be the best you can be?

We can link cause and affect at a macro, non-quantum, level. But it seems that there is a point at which, as things get smaller and faster, quantum effects become more important until at the level of the photon they are about all there is.

I'm not sure that I could define a law of quantum anything and collapsing wave functions is more a point of view than a serious theory in 2007.

Hi Blacknad,

" ... is there any other way to get at the truth?" I believe so and in several ways. One of these is through simple experience. Let me explain. At one time no human could fly. At the time it could well have been said that humans did not have what it takes to "Really Know" anything about flying. These days we fly all the time. The only way that one can not "Really Know" is if one doesn't care about it. when aviation became practical in the 20th century many, those who cared, came to "Really Know" about flying.

I think that something like this is happening right now in terms of atomic systems and the other things that concern quantum theory. Bohr, Sommerfeld and all the early pioneers of QT felt that we would never "Really Know" what is going on at the small scale. Well I loog around me and see electrical engineers working small with small numbers of atoms to make integrated circuits and such. I have scientific colleagues that work with single atoms, molecules, minute scrapes of energy and time. When we "shoot the breeze" about all this, we are discussing common experience. While I am hard pressed to explain anything about without a pile of math, I, nevertheless, feel comfortable working with it. The point is that as we work with something, i.e., gain experience, we begin to "Really Know" it.

Another method is familiar from differential equations: take a "wild a$$ guess" and then check it. Many of the early workers in QT, after Bohr but before Schrodinger/Heisenberg, used this method. This is especially true in spectroscopy where many formulae were simply guessed. Goudsmit was really good at this.(see:

http://www.lorentz.leidenuniv.nl/history/spin/goudsmit.html )

There is also the old standby, i.e., the unexpected breakthrough. Such events can make a big change in the picture.


"... the creation of something out of nothing ..." begs the question. Sounds like magic and for all I know that might be the ultimate answer. As a scientist though I seek rational explanations of everything. I don't have all the explanations I would like, but I do have a firm and perhaps irrational belief that they are to be had. I'll be damned if I'm the first to give up the side.


BTW a photon has energy equal to Planck's constant time the frequency (E = h nu) and its momentum is just the energy divided by the speed of light (p = E/c.)

Also I was not actually bored at the lecture I mentioned. Andrei Linde was speaking on the begining and fate of the cosmos. The guy is a brilliant cosmologist, good teacher and a decent human being etc. However, he is Russian and when he gets wound up it sounds like he has golf balls stuffed in his cheeks. Anyway it was all old news and the real deal was about the 1st International GLAST Symposium. GLAST is a big gamma ray space telescope that is set to launch Nov. 15, 2007. Now that prelaunch prep and testing is underway it is time to think about science again. (The best part was the meet and greet before and a couple of free beers after helped a lot! This is also why I'm sitting around doing long posts instead of doing something constructive!!!)

The astronomers and especially the cosmologist are champing at the bit. GLAST is also a big whoop in the high energy physics game as well. You see, particle accelerators are nearly as big as they can get in practical terms. If you want the really big energies you need to look up.

Dr. R.

DA, thanks for that explanation.

Dr. R.

Thanks for taking time to explain things. It does raise more questions than it answers - but if it didn't it wouldn't be QT.

Blacknad.

What about the Quantum Zeno Effect?

"The very nature of quantum physics is counterintuitive to conventional thinking. Among the many bizarre characteristics is the quantum Zeno paradox, an odd mathematical result that is being debated to this day. Assuming an unstable quantum state, intuition would dictate that eventually, the system will irreversibly decay in certain amount of time, defined as the Zeno time. However if the system is measured in a period shorter than the Zeno time, then the wave function of the system will repeatedly collapse before decay. In effect, constant measurements of the system will actually prevent its collapse! Even more mysterious, if the time interval between measurements is longer than the Zeno time, the decay rate of the system will increase, leading to what is termed the anti-Zeno effect."

Blacknad.

I think we really don't understand, beyond the superficial, what it means to measure.

And I'm not all that sure we understand the real meaning of the word "information" either.