Photons

[sfs]

I don't mean this to sound insulting, but isn't there a bit of human arrogance involved here? Because you physicist guys can't predict something, you assume it's random?

No, QM isn't called random just because physicists can't predict the outcome. Plenty of physicists (Einstein, most notably) believed that the unpredictability of QM had to be a reflection of an underlying deterministic process, one that we just hadn't yet found (or maybe couldn't find). This approach to QM is called "hidden variables" -- the assumption that there is a hidden variable that explains why one nucleus decays and not another, for example.

It turns out, however, that all hidden variable theories predict different results than QM for certain experiments (see Bell's inequality), and that QM is right. So hidden variable theories are not possible as descriptions of nature. The loophole is that "nonlocal" hidden variable theories are still allowed; in these theories, information about the hidden variable(s) can be transmitted faster than the speed of light. That seems to violate another well-observed feature of the universe, so most physicists aren't too happy with that idea either.

 

[Elendur]

There's lots of concepts which may or may not be true.

Correct.

Describing and predicting are two different things.

Correct.

However, we're doing both. We've observed something. We try to describe what we've observed, we try to extrapolate the observation to predict something.
It goes hand in hand.

We describe with an approximation and we've got control over the error.

Yes. As a Christian, I get accused of approximation and filtration a lot. So we have something in common.

Not only that, I'd wager a whole lot more as well.


I just thought of an example.

Do you think there is an average human height?
I assume you'd answer yes.

Would you measure each and every one of the humans in order to get to the answer?
Or would you go another way about it?

(And yes, that does have to do with randomness)

 

[BaconWizard]

What, is there some kind of secret I'm not allowed in on?



Are you saying there is such a thing as randomness? And is the universe fundamentally lawless?

Things can be random AND lawful.
Check out fractals, which are plotted graphs of random behaviour and yet have a pattern. Not any old pattern either....

 

[florida2]

I don't mean this to sound insulting, but isn't there a bit of human arrogance involved here? Because you physicist guys can't predict something, you assume it's random?

And a joke: What did one casino owner say to the other? "What I love about this job is the exciting unpredictability. Some days you win, some days you win a whole lot."

There are certain things that we simply cannot know. Heisenberg uncertainty principle shows us that we cannot know both the position and velocity of a particle. The more accurately we measure one, the less accurate we can measure the second. It's not that physicists are not clever enough or their machines aren't good enough. It's a fundamental property of the universe.

Thanks to quantum mechanics we now know that the universe is not a deterministic place. Probability is a key part of how the quantum world works

 

[essentialsaltes]

I don't mean this to sound insulting, but isn't there a bit of human arrogance involved here? Because you physicist guys can't predict something, you assume it's random?

sfs gave a perfect answer.

 

[Chesterton]

sfs gave a perfect answer.

The perfect answer is a "Yes and No" answer?

"Hidden variables." As a theist I'm sometimes mocked for believing in hidden things.

 

[essentialsaltes]

The perfect answer is a "Yes and No" answer?

"Hidden variables." As a theist I'm sometimes mocked for believing in hidden things.

No, that's the point. If QM is not random, then hidden variables exist.

The existence of hidden variables implies things that have been contradicted by experiment, or violate otherwise established physics.

Therefore, mainstream physics does not believe in hidden variables. But as a consequence, quantum mechanics contains randomness.

 

[RealityCheck]

No, that's the point. If QM is not random, then hidden variables exist.

The existence of hidden variables implies things that have been contradicted by experiment, or violate otherwise established physics.

Therefore, mainstream physics does not believe in hidden variables. But as a consequence, quantum mechanics contains randomness.

And, "hidden" would mean, in this case, "undiscovered as of yet," not "undiscoverable no matter what."

 

[Chesterton]

No, that's the point. If QM is not random, then hidden variables exist.

The existence of hidden variables implies things that have been contradicted by experiment, or violate otherwise established physics.

Therefore, mainstream physics does not believe in hidden variables. But as a consequence, quantum mechanics contains randomness.

A simple "I have no idea" would have sufficed.

 

[essentialsaltes]

A simple "I have no idea" would have sufficed.

I'm not sure if you're just playing with me or what.

The conclusion that quantum mechanics includes randomness is not an assumption, based on a lack of understanding. Nor is it "I have no idea."

Randomness is a result that has been tested by experiment. Alternative explanations have been falsified.

 

[Chesterton]

I'm not sure if you're just playing with me or what.

No, I promise I'm not playing. But I asked if QM was random, a yes or no question, and you came back with "...if QM is random...", and "...QM contains randomness..." That's why my eyes got all Twilight Zoneish.

 

[Justatruthseeker]

From what I understand, the science isn't clear on whether photons are particles or waves, because they seem to have characteristics of both.

When light lands on a physical object, some of it's reflected and some of it's absorbed (and in the case of transparent material like glass or water, most of it just passes through).

My question is: what's happening on the level of the individual photon? Are some of them (if they are particles) bouncing off things, and some of them absorbed, or are a percentage of them (if they are waves) doing the same? Can we determine the percentage?

If I can see a rock in my backyard, it's because the photons are bouncing off of it and striking my eyeballs. But on a hot summer day, I can also touch the the rock and feel warmth because of those same photons.

Ahhh, but then you have to ask yourself if light is a particle, how a particle transfers the exact image of what it reflects off of to your eye, down to minute detail. Silly putty of the universe?

But seriously, that is a question that still remains unanswered if photons are particles, as these particles must transfer an exact copy, surface detail and color as they reflect off an object and then reach your eye.

Of course, I hate to say I told you so to the skeptics, but even how our vision is interpreted by the brain is an electrical process and light is an electromagnetic phenomenon.

HowStuffWorks "Perceiving Light"

 

[essentialsaltes]

No, I promise I'm not playing. But I asked if QM was random, a yes or no question, and you came back with "...if QM is random...", and "...QM contains randomness..." That's why my eyes got all Twilight Zoneish.

I'm sorry if wires were crossed, but here's how I recap the conversation:

You: Are you saying there is such a thing as randomness?

Me: The philosophers will argue about what quantum mechanics means, but to this humble physicist, it appears that yes, quantum events are inherently random.

You: isn't there a bit of human arrogance involved here? Because you physicist guys can't predict something, you assume it's random?

sfs & me (longwindedly & perhaps unclearly): No. The random nature of quantum mechanics is based on evidence.

 

[Chesterton]

I'm sorry if wires were crossed, but here's how I recap the conversation:

You: Are you saying there is such a thing as randomness?

Me: The philosophers will argue about what quantum mechanics means, but to this humble physicist, it appears that yes, quantum events are inherently random.

You: isn't there a bit of human arrogance involved here? Because you physicist guys can't predict something, you assume it's random?

sfs & me (longwindedly & perhaps unclearly): No. The random nature of quantum mechanics is based on evidence.

Sorry, essential, but I am trying to pin you down here because I'm curious. Either:

1) The universe is lawless; or

2) We scientists just haven't figured out the laws yet.

Which would you say?

 

[kevinmaynard]

Sorry, essential, but I am trying to pin you down here because I'm curious. Either:

1) The universe is lawless; or

2) We scientists just haven't figured out the laws yet.

Which would you say?

You present a false dilemma. The universe could be lawful and random.

 

[RealityCheck]

You present a false dilemma. The universe could be lawful and random.

"Random" is not the right word I think. "Unpredictable" is the better word, because you're essentially talking about random results that come about due to physical laws - in which, generally, there are a limited number of possible outcomes.

For example, when you roll a fair, unloaded die, you cannot predict what face will come up. It's outcome is "random" - or really, "unpredictable."

It's random from our point of view, but the reality is, it's just entirely unpredictable. You shake it in your hand, it is bouncing off your palm and fingers - interactions that may be too many and complex to model with simple mechanics, but they are interactions we understand. It falls according to gravitational laws. It bounces, it spins and rolls, all of which may be very difficult or even impossible to model mathematically to concretely predict the outcome. But it's still just gravity and collisions, friction and general large-scale mechanics that operate on the die.

With a die, there are a finite number of outcomes. You can't necessarily predict which of those outcomes will come up... but you know it will be one of those outcomes. When you roll a die, you don't roll it expecting a truly and entirely random result. The result will be 1, 2, 3, 4, 5, or 6. It will NEVER be 5.2, 9, -3, etc. And in general, quantum processes that we describe (perhaps inaccurately) as "random" are limited to a finite number of outcomes. We can't necessarily predict which of those outcomes will occur, but we do know it will NOT be some other outcome, just like with the die. If the die could be rolled and come up -3, then everything we understand about die rolling is WRONG. And if somehow a quantum process produced an outcome that was NOT one of a limited set of known possible solutions, then quantum theory would be entirely wrong.

 

[Chesterton]

You present a false dilemma.

No.

The universe could be lawful and random.

No.

 

[RealityCheck]

No.



No.

Just saying "no" fails to advance the discussion.

 

[sfs]

Sorry, essential, but I am trying to pin you down here because I'm curious. Either:

1) The universe is lawless; or

2) We scientists just haven't figured out the laws yet.

Which would you say?

Neither. The actual choices are:
1) The universe obeys laws that have a random component;
2) The laws of the universe are deterministic, but work in some way that is both unknown and involves faster than light (and probably instantaneous) communication.
3) The laws of the universe are deterministic, but the "universe" that obeys them is not the one that we perceive, but the totality of the wave function, which includes all possible quantum outcomes.

 

[kevinmaynard]

No.



No.

Yes and Yes.

The universe is unpredictable and follows laws. You present a false dilemma.