Time, causality, and prime movers

What's beyond the sky used to be a reasonable question.Sometimes we ask the wrong questions, and answer them with bad answers. One particularly bad question is: “what was there before the Big-Bang?” There are many others, but this one requires a little mental gymnastics in order to get used to modern ideas of time and understand what the consequences are.

“What was there before the Big-Bang” may have looked like a good question before Einstein (if anyone then had a clear idea of a universe expanding from a very dense original state, which they didn’t), but the revolution of Relativity in our concepts of time and space made it scientifically absurd. The word you have to remove from the question is “before”. Substitute “beyond”, and we have something to talk about, but “before” is just absurd in this context. Let me explain.

In a Newtonian, 19th century scientific framework, time and space are fundamental: physical phenomena, and the universe in general, happen in time and space, but time and space aren’t physical phenomena themselves. Einstein showed that time and space are not only relative, but are physical expressions of geometry. They are even in a way consequences of matter and energy. In other words, time and space are properties of the universe. They are of the universe, and don’t make sense outside of it (whatever “outside” could mean when talking about the universe).

As a consequence, time and space as we perceive them are not necessarily useful concepts “everywhere” (and I use that word with scare quotes to express an idea of a place that is more general than what we mean in everyday speech).

The Big-Bang is such a “place”: what scientists mean by Big-Bang is that early region in the universe where everything was so densely packed that our current knowledge of physics breaks down. It is where our ignorance begins, where taking our usual concepts of time and space seriously would lead to absurdities and infinities. The only certainty about what’s beyond the Big-Bang is that we need new science to understand and describe it.

Now if you care about metaphysical questions of origins, that leads to a serious problem: if there is no useful concept of time beyond the Big-Bang, do we still have a useful concept of causation?

Hume’s concept of causation cannot be kept in this context because it is based on time: the cause must be prior to the effect. If “prior” is meaningless, we are reduced to correlation, which can easily be reversed without contradictions.

The only causation that can be used here is the logical concept of necessary causes: if x must exist for y to exist, and y exists, then x exists. The first premise however is a tricky one…

Let’s take a favorite argument from theists, the Kalam cosmological argument. It starts with “everything that begins to exist has a cause”. There are too many problems in this statement to count, but the word we need to focus on is “begins”… The argument continues with “the universe began to exist”. We can stop right there: no, as far as we know, the universe didn’t “begin” to exist because that implies a meaningful notion of time, that we don’t have near the supposed origin of the universe. This argument simply doesn’t work.

I’ll leave you with a final puzzling thought about time and causality. Quantum physics introduced a funny notion that is that the results of some experiments cannot be predicted, and that we can only predict the probabilities of the possible outcomes. Without going into too much details, this doesn’t necessarily eliminate determinism at a fundamental level, but it does confirm that with our limited perception of time, the future is not fixed. One interpretation in particular, the Many Worlds Interpretation, sees us navigating in an infinitely branching network of possibilities. When an experiment is performed, other outcomes than the one measured may seem like they didn’t actualize, but according to Many Worlds, they did, it’s just that this is not where we are. Now here comes the crazy bit: in this interpretation, everything is still fundamentally reversible in time, and the branching that happens about the future also happens for the past. The consequence is that the past may be just as undetermined as the future is.

Have a nice day.

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More fundie fun

snakeThere is an article on stupid Conservapædia (that I won't grace with a link) that rants about the theory of Relativity because apparently it contradicts the Bible. Well, what doesn't? Even the Bible contradicts the Bible...
Anyways, here is how that fantastic piece of entertainment begins:

"The theory of relativity is a mathematical system that allows no exceptions."


Well, wrong. This just shows how much these clowns understand about science: nothing at all.
The theories of Relativity are *using* mathematical tools, but they are not about the tools, they are about the physics of high energy phenomena and strong gravitational fields. So they got the most basic definitions wrong. But of course they did it on purpose you see, because mathematical theorems suffer no exceptions (which is precisely why math is not science) whereas physics is perfectly fine with limiting its own theories to a specific experimental range.
It's worth repeating: if science knew everything, it would be over and nobody would do it. Only engineering would remain. Contrast that with religion, which was done once and for all thousands of years ago and that people are still doing today.
This being said, I think the authors of the silly piece in question should stop using their GPS right now, cause you know, of being an insult to God and all.

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Wild non-scientific musings: extra dimensions and parallel universes

fig. 8Amy was asking me some questions on "alternate dimensions" and "parallel universes". Here's my answer, which is entirely non-scientific although it is based on a few things I know (or think I know) about physics. I'm suspecting for example that the string theory stuff is a little shaky as I never really studied the math in there.

Alternate dimension doesn’t mean much in itself: alternate to what, and how? A dimension is a direction in space-time. We experience the four known ones every day: width, height, length and time. But there are many physical theories such as string theories that postulate additional dimensions. Why we don’t experience them has different explanations. One is that some of those dimensions may be closed on themselves (think circle vs. open line) with a very small radius. Such an additional dimension would be hard but not impossible to detect. We may actually know in the next few years as there are experiments being built right now to test that hypothesis (negative results wouldn’t entirely rule out the possibility but would put a limit to the radius of space along those dimensions). By the way, there is an interesting theory from the 20th century that was able to unify gravitation and electromagnetism through an additional closed dimension. It suffered from a number of problems and was more or less proven wrong but it was an interesting idea that all forces would somehow come from the geometry of a larger space-time.

Now a parallel universe is a completely different idea. It’s the idea that what we perceive as our universe is only a fraction of physical reality, and that other similar or entirely different universes may exist somewhere else. You then have the idea of a metaverse that contains all of those, which should be what we really call Universe if we used words appropriately.

As to where those universes might be, there are several possibilities, not necessarily exclusive of one another. First, according to string theories, we live on a kind of multi-dimensional “brane” which is like a slice of a bigger space-time (read with more dimensions) to which the particles we’re made of cling. There would be more open dimensions in this view that we don’t see because the particles we’re made of are inherently bound to a particular brane: they only exist as part of it, they are a property of that particular brane if you want. In that view, there are other branes with other universes that may be as big as ours. Sometimes, actually, these branes can get close to one another or even collide, which gives us a possibility of confirming their existence by observing the effects of cross-brane interaction (for example, matter from one brane might gravitationally affect matter on another, and the closer branes are, the bigger the effect, which is interesting as branes are not flat and distance between them is not fixed).

Another idea that is also realized in string theory is that there is a multi-dimensional landscape of universes, and that one universe can experience a local instability that turns into a completely new baby universe that expands on its own, with physical laws that are a variation of the ones in the parent universe. It’s an interesting concept because it gives rise to the idea that a large number of universes might evolve from a larger cosmos. Here the word “evolution” is not used lightly: it would really be the case that there would be a form of survival of the fittest where the most common universes would survive and give birth to more and more stable baby universes. In both versions of parallel universes, the smaller universes are still connected within a larger Universe

But there is yet another possibility which I think is quite interesting, although completely untestable.

The idea would be that parallel universes don’t have to be connected to one another at all: why should there be one single connected universe, all in one piece? You could actually postulate that any universe that is self-consistent would just exist by virtue of being possible. For example, the group Z2, which is a mathematical structure described by: 1 x 1 = 1, 1 x -1 = -1, -1 x 1 = -1 and -1 x -1 = 1 just exists, and it exists outside of any universe we may be in. It’s just universal, it doesn’t need a creator god or to be observed to exist. It just is. How about our universe just is one of those mathematical structures, only much more complex, that just exists by virtue of being consistent? Am I confusing the map for the territory? Am I? I mean, if we discover one day that the world’s natural laws can be reduced to a relatively simple mathematical structure (and we have lots of indication that it could from looking at elementary particles), how much of a stretch would it be to say that the universe actually *is* that mathematical structure? I mean, if it’s indistinguishable from it, isn’t it just the same?

We could then talk about how consciousness fits into all this but that’s a whole ‘nother discussion.

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Black hole evaporation paradox?

I just sent this letter to Scientific American. I'd be interested to have any informed opinion on the matter.

I’ve read the article about black hole computers with great interest, but there are still a few questions that I think remain unanswered.

The article makes it quite clear how black holes could be memory devices with unique properties, but I didn’t quite understand what kind of logical operations they could perform on the data.

But another, more fundamental question is bugging me ever since I read the article. From what I remember learning about black holes, if you are an observer outside the black hole, you will see objects falling into the black hole in asymptotically slow motion. The light coming from them will have to overcome a greater and greater gravitational potential as the object approaches the horizon, losing energy along the way and shifting to the red end of the spectrum. From our vantage point, it seems like the object does not reach the horizon in a finite time.

From a frame that moves with the object, though, it takes finite time to cross the horizon.

This is all very well and consistent so far. Enter black hole evaporation.

From our external vantage point, a sufficiently small black hole would evaporate over a finite period of time. So how do we reconcile this with the perception that objects never actually enter the horizon?

It seems like what would really happen is that as the horizon would actually become smaller over time, the incoming particles would actually never enter it.

If this is true, and no matter ever enters it, would the black hole and the horizon exist at all?

From the point of view of an incoming object, wouldn’t the horizon seem to recess exponentially fast and disappear before it is reached?

If nothing ever enters the horizon, is it really a surprise that black hole evaporation conserves the amount of information?

Does the rate of incoming matter modify the destiny of the black hole? If it grows faster than it evaporates, I suppose the scenario is modified, but how so?

I know it is quite naïve to think in these terms and that a real response could only come from actual calculations, but still, I hope that you can give me an answer to what looks like a paradox to me. I don’t see how you can reconcile the perceptions of an external and a free-falling frame of reference if the black hole evaporates except if nothing ever enters the horizon.

UPDATE: a recent paper presents a similar theory to solve the information paradox:

http://arxiv.org/abs/gr-qc/0609024v3
http://arstechnica.com/news.ars/post/20070622-apotential-solution-to-the-black-hole-information-loss-paradox.html

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