Deterministic Universe?

Colleges and Universities A-Z Massachusetts Institute of Technology
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Part of my head says that as a scientist, I should believe that the Universe is deterministic, and there is no god, etc.

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<p>I don't have time to read the whole thread, so I don't know if this has been addressed already, but the deterministic view of the Universe was actually used during the Enlightenment in support of religion/God (I think certain religious doctrines such as predestination would require a deterministic Universe...i.e where if God knew all the compenents of every particle in the Universe, He could then predict the future perfectly.)</p>

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<p>My background.</p>

<p>Science. My life. I think that reason should be the guiding principle of all human endeavors. See Voltaire, eighteenth century French thinkers, et al. [also known as my heroes].</p>

<p>Religion. I'm Jewish. Some consider this to be the most "pure" monotheistic religion. Others consider it to be evil. Those people tend to be closed minded and misguided about many other things as well. I practice religion, and in the Christian way of speaking, am a "man of faith." </p>

<p>How do I compromise these two sometimes mutually-conflicting notions?</p>

<p>Let us consider an example. I personally am a Course 7 person, so let us take the model of a plant.</p>

<p>People always recognized that the plant grew with seemingly no food. This interested people. How does this happen.</p>

<p>Stage 1. The plant just grows. G-d tells the plant to grow.
In this model, the entire process of the plant growing is one giant black box. This model explains very little.</p>

<p>Stage 2. The plant grows because it intakes carbon dioxide. CO2 can be fixed to form higher energy carbon-containing compounds.<br>
In this model, we recognize that plants use the surrounding atmosphere in order to grow. But there is still a black box. We see that CO2 comes in and growth comes out. But what happens in the black box now?</p>

<p>Stage 3. Photosynthesis. In the Calvin-Benson cycle, NADPH and ATP, two products of the light reactions, provide the energy to drive the otherwise unfavorable process of fixing CO2 together.
We have more of a molecular understanding. Now the black box is how do NADPH and ATP come together to make glucose and other carbon containing compounds?</p>

<p>Stage 4. Biochemistry. If we are familiar with enzyme kinetics and molecules like Rubisco, Phosphoglyceraldehyde, etc -- we can make models of how molecules come together specifically.</p>

<p>What's the pattern? Science is reductive. With increasing knowledge of science, we have the power to take one black box and reduce it to smaller black boxes of more specific pathways.</p>

<p>But science can only take one big black box and turn it into thousands of tinier, more specific black boxes. There will always be more proximal causes behind a particular phenomenon. As science advances, these causes become more clear. But do you ever truly know the root of the cause? Can the black box ever entirely go away? Certainly not.</p>

<p>Most people here are probably larger fans of physics than biology. Alright. Example. Gravity. Everyone knows that F[g] = -Gmm/r^2. This is a mathematical model to justify experimental observations. Quantum theory expounds upon this relationship and explains [or tries to explain] how gravity "works." We reduce the black box. Then we say there is a graviton, the standard carrier particle for this force. In other words, you can do as much science as you want, but science is only capable of giving you models that explain observations. It is impossible to truly know what causes something to happen. More advanced science reduces the unknowns to more fundamental levels. But that still does not mean you understand the true cause.</p>

<p>Some people may deny this. But keep in consideration that society at phase 1, 2, and 3 of my example thought in THEIR time as well that THEY knew the most proximate cause as well. Science will always reduce. And God will always occupy that infinitessimaly small black box, when the cause again becomes unclear.</p>

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<p>i was thinking...quantum theory says one can only predict the probabilities of a particle's position/momentum, yes? If one was able to travel back in time somehow with knowledge of the particle's actions the first time around (i.e. before traveling back in time), would the particle act in the exact same manner, consistent with the immutability of the past/present's current characteristics (i.e. if you travel back in time, you always have and always will exist in that time period), or could it act differently, as consistent with quantum theory? Perhaps this seeming paradox rules out time travel, merely because it seems to violate quantum theory. (please tell me if ive screwed up some major theory of time travel or quantum mechanics, thus invalidating my entire argument)</p>

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<p>Well I won't pretend to know the answer to that, but one thing to keep in mind is that if you knew the particle's actions the first time around as you say, that means you had to observe the particle for all time in question. When you observe a particle, it's wavefunction "collapses", ie it becomes concentrated to the point in space you observed it. For example, if you put a detector on one of the two slits in a double slit experiment with electrons, there will be no interference pattern. Instead there will be only two bright lines corresponding to the slits. So perhaps if you've collapsed the wavenfunction and then someway traveled back in time you would witness the same motion again. But if this is the case it's because the wavefunction has been collapsed by the observer. So it doesn't imply that you could predict the future. On the other hand, doesn't having a "time machine" suggest that the universe is deterministic since you can travel into the future?</p>

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<p>Ok. A lot of people on here seem to be refering to the Heisenberg Principle(sp?), which I believe says that you can't simultaneously know a particles position and velocity. </p>

<p>On some other forums where they are discussing stuff like this, there is a big argument that the Heisenburg Principle doesn't happen because of interference when you measure it, but something else.</p>

<p>Could someone elaborate on this? I have trouble understanding very much about quantum mechanics. I read something about quarks, and got lost with all these n-dimensional crazy theories.</p>

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<p>"On some other forums where they are discussing stuff like this, there is a big argument that the Heisenburg Principle doesn't happen because of interference when you measure it, but something else."</p>

<p>That's right; the uncertainty is due to the wave nature of matter.</p>

<p>In classical mechanics we have particles, and we can use Newton's 2nd Law (or better yet the lagrangian) to find it's position as a function of time (as long as we know the forces for all time). In other words, we know m*(d^2/dt^2)x = 2x + 5x^2 or whatever, and we can solve for x(t). (Maybe not for this eq.) From this we can then tell the particles energy, position and momentum.</p>

<p>In quantum mechanics there is the Schrödinger equation. We can solve the Schrödinger equation for Ψ(x,t). This is the wavefunction, which has a value for every point at every time. The square at any point and time gives the probability that the particle will be located in that position. We can perform operations on the wavefunction to find the momentum and energy. All of this brings up some interesting results, like the fact that a particle can "tunnel" through a barrier of higher potential. </p>

<p>Now to finally get to the point. Imagine that the wavefunction was a sine wave, sin(k1<em>x). In this case, it isn't localized at all. In other words, the wavefunction extends to infinity in both directions. It is located everywhere, not at a point. However, we know its wavelength exactly: 2</em>pi/k1. We can localize the wave by adding many different sine waves. If we do this, we can make it's amplitude near zero everywhere outside of a small region. To do this though, we had to add waves with different wavelengths k. (Now remember that the wavelength (2pi/k) is related to the momentum (λ=h/p).) So the more sin(kn*x) we add, the more our uncertainty in k grows. To perfectly localized the wavefunction, to know the position exactly, our uncertainty in k would grow to infinity, just as when we knew k exactly our uncertainty in position was infinite.</p>

<p>Sorry for the sloppiness of this explanation. I think it does help to get a conceptual understanding of uncertainty though. Remember, the uncertainty has nothing to do with observation. (Curse Brian Greene! lol)</p>

<p>Discussions like this are why I wish I was headed to MIT next year :(</p>

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<p>samwise: "On the other hand, doesn't having a "time machine" suggest that the universe is deterministic since you can travel into the future?"</p>

<p>But wouldn't it be impossible to measure all aspects of the universe, and make the computations? Thus you can't travel in time. </p>

<p>Something that I like tinkering with is time traveling paradoxes. Suppose that your future self comes back in time to teach you. That way, in 20 years, you can come back. Now this has 2 implications:</p>

<p>1) There are infinite different universes, one for each time(your future self had his own universe).
2) Time has always existed. Otherwise, how did the first you come back in time? But if Time has been forever, than when did the universe begin? Also, I am pretty sure it means that all states of the universe simultaneously exist.</p>

<p>Thanks for the explanation though. I didn't know it was wave model. Is that how they teleport electrons, etc?</p>