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Physiology & Medicine / Re: Does my mother possibly have ALS?

« Last post by paul cotter on Today at 19:10:50 »

Glad to hear that, mnd in it's various forms is a dire diagnosis.

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Physiology & Medicine / Re: Does my mother possibly have ALS?

« Last post by Pseudoscience-is-malarkey on Today at 17:26:48 »

If I had known that electromyography results are instant, I would have not posted this question. Anywho, she is fine. ALS has been ruled out.

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Physics, Astronomy & Cosmology / Re: QM puzzle: Is a measurement being made in the 2 slit experiement all the time?

« Last post by Halc on Today at 16:16:38 »

So the integral we'd be interested in, representing the total probability of finding the electron at the screen from  'then'/ that time  to  infinity  is finite << 1.   Specifically we can assume the electron would never be found at the screen, write it off and just fire the next electron.

Sounds reasonable

Anyway, we were talking about a lack of detection at the screen as being a lack of measurement:

Depends on your definition of measurement. In real life, measurement is epistemological. If the electron hits the lab wall, you're unaware of it and your epistemic wave function isn't altered by the event. In the sim, the sim would know that the wall was hit and the actual wave function would be altered, and the real wave function would collapse. The screen then also measures the collapse because the screen measures the wall; it becomes entangled with the wall state.

Well, that is still some measurement by the screen as far as I can see.

Yes, you know it missed, so the epistemic wave function is altered by the knowledge, even if it isn't 100% certain.

It is NOT at the screen at any time, although there are lots of other places it can be

Unless you're assuming a counterfactual interpretation, I think it a mistake to talk about where it is in the absence of measurement. But a lot of simulations do exactly that, so I suppose it depends how your sim is implemented. You know it missed, so the new wave function can yield odds of where it likely hit, and that's assuming that the lab is reasonably closed and it doesn't shoot off into space never to interact with anything, as so many photons never do.

Is it possible for a thing to exist despite the fact that it hasn't and will not in the future interact with anything else?

A matter of definitions. What does it mean to exist? There's conservation laws, so of course it exists. It merely lacks a location/momentum.

  Anyway.... there's always gravity which we don't tend to include in any Quantum Mechanics,   the electron is still providing some energy density and thus curving space, i.e. it is interacting with something else in some way (you would think).

For example, the electrons can encounter other particles and potentials en route to the barrier and/or screen.

Always wondered about that. Do they regularly do the electron-gun thingy in a vacuum to avoid that sort of thing?

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Physiology & Medicine / Re: Does my mother possibly have ALS?

« Last post by paul cotter on Today at 15:59:39 »

While I sympathise with your difficult family situation nobody here can answer your question. As far as I know one of our contributors is a medic but diagnosis online is simply not possible. Wishing your mom all the best.

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Just Chat! / Re: Is there a universal moral standard?

« Last post by hamdani yusuf on Today at 15:42:03 »

The founders of democratic countries must have assumed that it was the best available option for them. Otherwise, they must have chosen the better option. They were confident that their citizens were mostly rational and well informed.

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Physiology & Medicine / Does my mother possibly have ALS?

« Last post by Pseudoscience-is-malarkey on Today at 15:27:56 »

Last February my 74-year-old mother got surgery for her severe spinal stenosis and her recovery has not been great. She still feels weak and stuff walking around, and uses the walker her mom (my grandmother) used during the last few years of her life. Today she is getting an electromyography to rule out ALS. I explained to her how rare motor neurone disease is and that worrying about it has no benefit whatsoever. My mother, as her mother before her, lived a very active life and looks much younger than she actually is. So, you can see how awful it is for someone like her to have mobility problems..
ALS used to be a relatively unheard of disease until a decade ago with the the wave of viral Ice Bucket Challenge videos on YouTube. Now (for better or worse) almost everyone knows about this incurable menace and worry about having it or not. This, and the fact that my mom's partner died of ALS 13 years ago, will naturally produce these fears in one's mind.

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Physics, Astronomy & Cosmology / Re: QM puzzle: Is a measurement being made in the 2 slit experiement all the time?

« Last post by Eternal Student on Today at 15:18:54 »

Thanks @Halc.

You seem to be asking if the electron misses the screen, is a measurement taken? Well, not by the screen (yet)

   We seem to agree that an electron (represented by a Gaussian wave packet initially) can "miss" the screen.    It wouldn't matter if the screen is made infintely long parallel to the y-axis (and we fire the electron toward it along the x-axis).    This is evidently quite different from a Newtonian view of particles and their movement, where the electron could not possibly be found beyond the screen without having impacted on the screen on the way.   Hmmm...  actually I might give the screen some potential above 0 in my computer model, for the sole purpose of reducing the number of electrons that will propagate through it.    One issue with the simulation is - how long do you wait for the electron to have been detected by the screen?   If the screen glows, great, you're done, you can fire the next electron.   If it doesn't, then the wave packet is still spreading out to fill all of space as time progresses,  so the probability of the electron being found at the screen never falls to 0.   Clearly, for the purposes of a simulation you cannot wait forever.   Once the group velocity of the wave packet has made it so that the wave packet is centred far beyond the screen, we must assume the electron has just "missed", the probability of it being found at the screen then starts to fall off exponentially with time as the distance from the screen increases.   So the integral we'd be interested in, representing the total probability of finding the electron at the screen from  'then'/ that time  to  infinity  is finite << 1.   Specifically we can assume the electron would never be found at the screen, write it off and just fire the next electron.
    Anyway, we were talking about a lack of detection at the screen as being a lack of measurement:   Well, that is still some measurement by the screen as far as I can see.   It is NOT at the screen at any time, although there are lots of other places it can be, so it is a little bit of information about its location.   I'm sure you were aware of that and the spirit of what you've said remains OK.

   

or it never interacts, and is effectively nonexistent (according to any local interpretation at least).

    This might be philosophy.   Is it possible for a thing to exist despite the fact that it hasn't and will not in the future interact with anything else?   Anyway.... there's always gravity which we don't tend to include in any Quantum Mechanics,   the electron is still providing some energy density and thus curving space, i.e. it is interacting with something else in some way (you would think).

- - - - - - - - -
   Overall,   I'm very grateful for your time and consideration.   It is re-assuring.   I haven't really pasued to consider how often we would need to update the wave function in any experiment (or simulation).   I'm thinking that the double slit experiment actually works and has results that are as clear as it does mainly because there are things going on that continuously make everything de-coherent (and also coherent) in the right ways.   For example, the electrons can encounter other particles and potentials en route to the barrier and/or screen.  We could imagine that these interactions change the wave function as much one way as the next interaction will change it the other way.  As such, modelling the electron as a simple localised wave packet, which stays reasonably localised throughout, while travelling (to the barrier and screen) becomes a reasonable approximation.      (  i.d.k. )

Best Wishes.

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Plant Sciences, Zoology & Evolution / Do Animals Have A Sense Of Humor?

« Last post by Jimbee on Today at 13:37:23 »

I grew up with animals. My parents and I were all animal lovers. And I swear, they are almost human-like sometimes. And I don't think I am just anthropomorphizing them.

I grew up around dogs and cats, mainly. And I can vouch for the fact they have all the emotions humans do. Love, hate, compassion. Possibly even a sense of humor, believe it or not. Our sheep dog would tease our Siamese cat. Or sometimes when I went to get my dogs a dog biscuit and I stumbled a little, they'd wag their tail. Why? Why would they like that? It's because they thought it was funny? No?

Also, on a possibly unrelated note, I have heard dogs give off a sarcastic sigh from time to time. My personal theory is they have all of our emotions. Just none of our intelligence.

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New Theories / Re: An essay in futility, too long to read :)

« Last post by yor_on on Today at 13:03:34 »

A species you want as your neighbor?

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New Theories / Re: An essay in futility, too long to read :)

« Last post by yor_on on Today at 13:02:31 »

And as for that 'list of shame'? It's not only Israel and Hamas that should be there, we started it after the second world war. And then we let it boil. And will probably do our best to avoid any responsibility for this too.