Richard Feynman said this:
excerpts from The Distinction of Past and Future
from The Character of Physical Law, 1965
It is obvious to everybody that the phenomena of the world are evidently irreversible...The past and the future look completely different psychologically, with concepts like memory and apparent freedom of will, in the sense that we feel that we can do something to affect the future, but none of us, or very few of us, believe that there is anything we can do to affect the past. Remorse and regret and hope and so forth are all words which distinguish perfectly obviously the past and the future. ...
[HOWEVER] In all the laws of physics that we have found so far there does not seem to be any distinction between the past and the future. ...
If I have a sun and a planet, and I start the planet off in some direction, going around the sun, and then I take a moving picture, and run it backwards and look at it, what happens? The planet goes around the sun, the opposite way of course, keeps on going around in an ellipse. The speed of the planet is such that the area swept out by the radius is always the same in equal times. In fact it just goes exactly the way it ought to go. It cannot be distinguished from going the other way. So the law of gravitation is of such a kind that the direction does not make any difference; if you show any phenomenon involving only gravitation running backwards on a film, it will look perfectly satisfactory. ... If you have a lot of particles doing something, and then you suddenly reverse the speed, they will completely undo what they did before. ...
[Experiments a few months ago indicated that] there is something the matter, some unknown about the laws, [suggesting] the possibility that in fact beta-decay may not also be time reversible, and we shall have to wait for more experiments to see. But at least the following is true. Beta-decay (which may or may not be time reversible) is a very unimportant phenomenon for most ordinary circumstances. The possibility of my talking to you does not depend on beta-decay, although it does depend on chemical interactions, it depends on electrical forces, not much on nuclear forces at the moment, but it depends also on gravitation. But I am one-sided - I speak, and a voice goes out into the air, and it does not come sucking back into my mouth when I open it - and this irreversibility cannot be hung on the phenomenon of beta-decay. In other words, we believe that most of the ordinary phenomena in the world, which are produced by atomic motions, are according to laws which can be completely reversed. So we will have to look some more to find the explanation of the irreversibility.
from Ursula K. Le Guin's intro to "The Left Hand of Darkness" ( 1969):
on reading science fiction as a thought experiment where "the purpose of a thought-experiment, as the term was used by Schrodinger and other physicists, is not to predict the future---indeed Schrodinger's most famous thought-experiment goes to show that the 'future," on the quantum level, cannot be predicted---but to describe reality, the present world."
What's beta decay? I know I knew, but the latest survivor plot used up the part of my brain that remembered.
(They all had a person come to suprise them, but only 1 person got to spend 24hrs with thier special person (the winner of a "challenge"). This one dude and his freind had arranged it so that they would pretend that his grandmother had died. The other survivors were so sympathetic that they threw the competition. It was pretty sneeky).
Here is my attempt to describe Beta Decay: it is a nuclear process that happens in the sun and other radioactive places. Radioactive atoms are unstable. So a neutron or proton will break down into smaller components, thereby stabilising the number of neutrons and protons. some parts fly off during the process, including neutrinos.
heres a better description.
I like Rebecca's quote a lot, and also the Feynman quotes, because they are grounding, and remind me that quantum physics is located in the world. The spooky thing about Shroedinger's cat is that it is mathematically both alive and dead at the same time. Good to be reminded that this is a model, and as such much less strange than A: time travel and/or B: predicting the future. The Feynman quote reminds me that eventhough there may be an apparent lack of symmetry in some aspect of Beta-decay, and eventhough this might mean that time really does have a one-way trajectory after all, beta-decay itself (and therefore this whole discussion) belongs to a different category of inquiry than, say: predicting what I will make for dinner tonight (raw celery and saltines again?!).
I like to think of epochs of the laws of physics in terms of easily identifiable activities. Galilean physics will get you to the grocery store, if you're willing to walk. If you're driving, you need to have a talk with Mr. Newton. If your grocery store is located on the moon, you're going to have to do some relativistic course corrections, and you need to check in with Dr. Einstein. If you're buying quarks at the lunar grocery store ... okay, every analogy has it's limits.
What if you're a cat, trapped in a box?
quantum tunneling ... walls are primarily nothing
|
Richard Feynman said this: