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One-sided debate

One-sided debate

Posted Jun 28, 2007 11:27 UTC (Thu) by forthy (guest, #1525)
In reply to: One-sided debate by man_ls
Parent article: More quotes of the week - scenes from a flame war

How can the arrow travel a distance which can be infinitely subdivided?

The funny thing here is that current physics says basically that you can't infinitely subdivide neither the distance, nor the time - it's all quantized. If you could subdivide both distance and time infinitely, it works out ok again, as well (just that this type of mathematics was developed 2000 years later). But if you feel uncomfortable with infinity, take the current view of the universe, which is finite and quantized in time and space.

Why is there anything instead of nothing?

Now this is a real hard problem, but even in math you have to accept some assumptions before you can even ask a single question.

One-sided debate

Posted Jun 28, 2007 23:40 UTC (Thu) by man_ls (guest, #15091) [Link]

you can't infinitely subdivide neither the distance, nor the time - it's all quantized.
I'm not sure what you mean by this -- certainly, time and space could be subdivided infinitely when I studied QED. At the same time, too; the equations used to work just fine. It just doesn't make too much sense under a threshold.

If I remember correctly, one way to derive the equations of quantum mechanics was to suppose that particles could only be in the vertices of a lattice, and then make the separation between lattice nodes go to zero.

By the way, "quantized" doesn't mean that a magnitude cannot be infinitely subdivided; it means that it can only take certain values. Those values need not be equally spaced, and they can be determined to arbitrary precision too, like the energies for a particle. Particles will usually be in a superposition of states so their energy cannot be ascertained. The same happens for time and space; but those two magnitudes are not quantized and so the particle has a wave function which spreads over space.

Perhaps I misunderstood you? Are you talking about a different theory?

But if you feel uncomfortable with infinity, [...]
Maybe I gave the impression that I have a phobia to infinity or something. I don't, I'm probably like every other guy, I'm fascinated and scared by it. I was just suggesting that, now as 2500 years ago, infinities start at the point where we stop understanding things; a subtlety which was not very well expressed, it seems.
[...] take the current view of the universe, which is finite and quantized in time and space.
The Universe is only finite because we would like it to be. Cosmologists are still searching for "dark matter", a substance about which we have no proof, just so that the equations yield a finite Universe. This "dark matter" is more faith than substance, if you ask me.