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Author Topic:   Big Bang Found
Son Goku
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Posts: 1208
From: Ireland
Joined: 07-16-2005


(4)
Message 121 of 301 (723248)
03-28-2014 6:06 AM
Reply to: Message 113 by Jon
03-27-2014 8:36 PM


What makes this such a great discovery?

Surely there are more important things that have been discovered.


Well it and the Higgs are probably the two most important discoveries in physics in the last forty years. The two most important discoveries in physics nearly a half century would rank pretty high on the list of scientific importance.

The discovery of the Higgs essentially shows us that what we thought about particles is correct. This shows us which of the ideas for the evolution of the early universe is correct.

We now have direct experimental evidence of how the universe behaved up to 10^(-35) seconds after it was born.

Surely there are more important things that have been discovered.

Yes, certainly. However I think, as a scientific achievement, knowing essentially the whole history of the early universe is fairly significant.

In fact, I could care less, and cannot imagine this discovery having any impact on me, or anyone really, whatsoever.

Probably not, but so what? Does that affect its scientific importance?

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Son Goku
Member
Posts: 1208
From: Ireland
Joined: 07-16-2005


(3)
Message 195 of 301 (723503)
04-03-2014 5:06 AM
Reply to: Message 194 by kbertsche
04-03-2014 1:01 AM


Re: Double talk..
I think some folks like to raise the example of radioactive decay because quantum mechanical systems seem complicated and sophisticated, and it is easier to use double-talk to fool people into thinking that quantum mechanical events have no "cause"

If I take two identical radioactive nuclei, literally identical in every respect and isolate them in a box where absolutely nothing affects them. One could decay in a millisecond and the other one million years later. Why? What caused that difference in the decay time?

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Son Goku
Member
Posts: 1208
From: Ireland
Joined: 07-16-2005


Message 231 of 301 (723663)
04-05-2014 12:25 PM
Reply to: Message 228 by cavediver
04-05-2014 7:36 AM


Re: Double talk..
I would think NoNukes' point still stands though, in that I could take a hydrogen atom in an excited state, which at some point transitions to the ground state. In standard Quantum Mechanics this transition is uncaused. Similarly with the tunneling of an alpha particle out of a nucleus, reagrdless of how complicated the interactions are, they are still only a complicated development of a wavefunction which only gives a probability. There is no cause of the actual emission.

Of course one could say that the standard picture of quantum mechanics is wrong and that there is an underlying theory where these things are caused, but I think results like Gleeson's theorem, the Kochen-Specker theorem, the infinite baggage theorem, e.t.c. show that such an underlying theory will have some pretty bizarre properties that seem just as hard to swallow as quantum mechanics indeterminate nature.

In the current scientific theory of the strong interactions (QCD), I think Nonukes' statement is correct. Alpha emission is uncaused.


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 Message 228 by cavediver, posted 04-05-2014 7:36 AM cavediver has replied

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Son Goku
Member
Posts: 1208
From: Ireland
Joined: 07-16-2005


Message 247 of 301 (723711)
04-06-2014 5:47 PM
Reply to: Message 234 by cavediver
04-05-2014 1:17 PM


Re: Double talk..
Okay I see your point now. I still think it can be useful to point out. A lot of these ideas about the universe's origins in theistic accounts are defended by standard ideas about cause and effect. Quantum Mechanics shows that those intuitive ideas, upon which a lot of Western philosophical thought on the issue is based, are not fundamentally correct. Even if the quantum mechanical ideas aren't directly related to "creation" itself.

One thing:

As far as I am aware we only have an excessively idealised and over-simplified QCD description of alpha emission, so this is not exactly surprising.

Even in the Quantum Chromodynamical picture the actual emission itself would be uncaused though, right? Even if we didn't simplify the QCD description of the complex internal state of the nucleus, the alpha particle and the surrounding field states, (which we simplify to two quantum balls with a potential between them), we wouldn't find the emission itself being caused. I don't think a full QCD calculation would reveal it to be caused and the lack of causation being simply an unsurprising feature of a simplified model.

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Son Goku
Member
Posts: 1208
From: Ireland
Joined: 07-16-2005


(1)
Message 250 of 301 (723749)
04-07-2014 12:36 PM
Reply to: Message 249 by kbertsche
04-07-2014 10:32 AM


Re: Double talk..
Well, let's make it simpler. The timing of nuclear decay is uncaused.

Although in truth I would still say the decay itself is uncaused, quantum mechanics simply states that the alpha particle's wavefunction spreads out of the atomic nucleus. However it still has a probability for being located inside the nucleus and a probability for being located outside the nucleus. However that is all. Either one of the probabilities can occur, being outside (decay) or inside (not decaying). Which one occurs is uncaused.

What is "caused" is the shape of the wavefunction itself, the distribution of the probabilities. However that isn't a cause of the decay, just a "cause" of its likelihood.


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Son Goku
Member
Posts: 1208
From: Ireland
Joined: 07-16-2005


Message 258 of 301 (723771)
04-08-2014 7:44 AM
Reply to: Message 254 by kbertsche
04-07-2014 10:21 PM


Re: Double talk..
Better, but to avoid confusion I recommend completely eliminating the word "uncaused". How about, "The time of decay of any particular nucleus is stochastic"?

Well the timing is not stochastic. That's the important thing. The probabilities in quantum mechanics obey relations (e.g. Bell's inequalities, Kochen-Specker, e.t.c.) that mean they are fundamentally different from normal probabilities.

Essentially the probabilities you meet in standard probability theory (stochastic processes, probabilities use in betting, e.t.c.) have mathematical properties that imply they result from your lack of knowledge about the system. The probabilities in quantum mechanics break these relations and imply the probabilities are fundamental, that there is no "deeper truth".

All that is caused are the probabilities.

Here are some questions for those of you who still want to maintain that nuclear decay is "uncaused". How can a large collection of these "uncaused" events have extremely predictable, deterministic behavior? What causes this predictable and deterministic behavior, if the system is nothing more than a collection of "uncaused" events?!?

The law of large numbers. If I have a 40% chance of decay and a 60% chance of the atom not decaying, well then if I look at billions of atoms, there is a large chance (you can estimate this chance using the central limit theorem) that about 40% will be decayed and 60% will be undecayed.

If you give me 10^12 radioactive atoms (there are about this many atoms of C-14 in 20 g of modern carbon), I can predict extremely accurately how many will remain in one half-life (about 5730 years)--exactly half of the original amount, with an accuracy of about 1 ppm. If each decay is truly "uncaused", what causes a macroscopic collection to have such predictable, deterministic behavior?

No, you can predict the chance that half will be decayed after one half-life. It's very likely for large samples that 50% will be decayed, however because it is random you could find only 40% had decayed after one half-life. It's not likely, but it can happen.

PaulK has already stated this. Any random process, repeated trillions of times, will begin to display seemingly deterministic behaviour. This has nothing to do with physics. Flip a coin four times, and maybe 75% are heads and 25% are tails. Flip a coin a quadrillion times and ratio of head to tails has an almost 100% probability of being 1:1.
So it begins to be almost "determined" that you will have a 1:1 ratio.

Now the difference between the coin toss and quantum mechanics is that, given enough knowledge, the outcome of each coin toss could be known. So the exact ratio of heads to tails after a trillion flips could be worked out in advance by a super-being. In quantum mechanics, each decay is fundamentally random, so all you have is a high chance of these ratios developing.


This message is a reply to:
 Message 254 by kbertsche, posted 04-07-2014 10:21 PM kbertsche has replied

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 Message 262 by kbertsche, posted 04-09-2014 8:37 PM Son Goku has replied

  
Son Goku
Member
Posts: 1208
From: Ireland
Joined: 07-16-2005


Message 269 of 301 (724067)
04-12-2014 6:19 AM
Reply to: Message 262 by kbertsche
04-09-2014 8:37 PM


Re: Double talk..
But the probabilities for radioactive decay are not unique or mysterious at all; they just follow a simple Poisson distribution, like many classical probabilistic processes. Classical problems, such as the frequency of calls into a call center, have probabilities which follow the same relations and are just as fundamental, with no "deeper truth".

This is not remotely correct. There is a "deeper truth" concerning the call center. Everybody phones the call center for some reason, the reason being some sequence of events that occured prior to their call.

However as PaulK said, usually all these details are superflous and we model calls as a Poisson process.

In most areas of science, when we introduce stochastic models and probabilities we are ignoring some deeper level of what is going on, usually because that deeper level is too complex to model or is irrelevant.

I'll take PaulK's roulette model. I mean the casino could obtain the atomic states of all molecules in the air, the shape of the dealer's hand and determine exactly what result will occur. This is of course impossible so it is model as if it were random.

However all of these models have properties (constraints obeyed by certain expectation values) that imply the come from some underlying deterministic sequence of events.

In contrast, quantum mechanical processes break these inequalities, meaning there is nothing occuring underneath.

You have taken a very simple quantum processes. An atom decaying or not decaying. However introduce an atom with four decay states, let's say it an electron in its shell could drop to one of four orbitals. You will immediately see behaviour that is impossible to explain in terms of some underlying cause.

Even for a single atom, you will begin to see this behaviour if you place two such atoms near each other.

I can prove this for you if you want, since EVC has Latex it would be easy to do.

The radioactivity, the radioactive decay, has a cause. Hence, it is very misleading (if not outright wrong) to say that radioactive decay is uncaused.

The capacity to decay is caused, not the actual event of decay.

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