Does the uncertainty principle apply to "nothing"?

[FireGarden]

I tried to use the UP in an argument on the origins of the universe -- the whole something from nothing question.

The UP states that it's impossible to know everything about a system. For instance you cannot know the exact energy of a system at an exact moment. Which leads to virtual particles in a vacuum, Hawking radiation, Casimir effect etc.

But the vacuum isn't nothing. It is spacetime -- a construction of the Big bang.

Does "nothing" count as a system as far as the UP is concerned?

 

[drkitten]

I tried to use the UP in an argument on the origins of the universe -- the whole something from nothing question.

The UP states that it's impossible to know everything about a system. For instance you cannot know the exact energy of a system at an exact moment. Which leads to virtual particles in a vacuum, Hawking radiation, Casimir effect etc.

But the vacuum isn't nothing. It is spacetime -- a construction of the Big bang.

Does "nothing" count as a system as far as the UP is concerned?

If you don't count a vacuum as "nothing," then what is nothing? You may have defined any physical system out of existence -- in which case the uncertainty principle, being a part of physics, wouldn't apply.

 

[Ziggurat]

I tried to use the UP in an argument on the origins of the universe -- the whole something from nothing question.

The UP states that it's impossible to know everything about a system. For instance you cannot know the exact energy of a system at an exact moment. Which leads to virtual particles in a vacuum, Hawking radiation, Casimir effect etc.

Well, that's not actually a good way of phrasing it (though the name encourages the problem). In quantum mechanics, the wave function IS everything there is to know about a system, and if you know the wave function, you know the system perfectly. The uncertainty principle is, more properly, not a limit on our knowledge of the wave function (which, in principle, can be perfect) but a limit on properties of the wave function itself.

But the vacuum isn't nothing. It is spacetime -- a construction of the Big bang.

Does "nothing" count as a system as far as the UP is concerned?

When you're talking about the big bang, you're talking general relativity. We don't really know how to reconcile GR with quantum mechanics. So we really don't have a good idea at this point as to what the uncertainty principle might even mean in such a context.

 

[FireGarden]

Dr K,
Defining "nothing" is exactly the problem.
The best argument I can come up with is, "if nothing has no physical properties, then how do you know that something cannot come from nothing?"

Vacuum is spacetime. It has properties. It can be curved by matter. It is a physical entity. So I agree it has to be counted as "something".

But, I then said that vacuum was the closest thing in our experience to "nothing". That still doesn't mean we can extend the UP to apply to "nothing".

 

[Cuddles]

The uncertainty principle in general applies to conjugate pairs of coordinates, the most commonly used example being position/momentum and energy/time, although there are others. If you have "nothing", however you define it, it cannot be described by any coordinates since there is nothing there to possess either position, momentum or anything else. Therefore no uncertainty priciple can apply to nothing (unless of course you are uncertain whether it's really nothing ).

 

[drkitten]

Dr K,
Defining "nothing" is exactly the problem.
The best argument I can come up with is, "if nothing has no physical properties, then how do you know that something cannot come from nothing?"

"Because we've never seen it happen," of course. The same way we know that fire-breathing dragons don't exist.

Usually when people are talking about "something coming from nothing," they're not talking about this kind of absolute "nothing" that I usually associate with the inside of certain posters' heads. They're talking about "thin air," or "a vacuum," or whatever. The idea that "something can't come from nothing" doesn't depend on the absolute absence of "physical properties" or even of the absence of matter.

Basically, I think you're taking (implicitly) far too stringent a definition of "nothing" by demanding that any concept with physical properties must not be "nothing."

But, I then said that vacuum was the closest thing in our experience to "nothing". That still doesn't mean we can extend the UP to apply to "nothing".

I think you've defined "nothing," literally, out of existence. So there's no more point to applying the UP to "nothing" than there is to applying it to dragons.

 

[andyandy]

When you're talking about the big bang, you're talking general relativity. We don't really know how to reconcile GR with quantum mechanics. So we really don't have a good idea at this point as to what the uncertainty principle might even mean in such a context.

true - most of the time, one can either use QM or GR depending on whether you're looking at large and massive objects or small and light ones - and you can just ignore the incompatability between the two theories. However some cases - extreme physical situations that are both massive and tiny - exist in the demilitarised zone between - requiring both QM and GR to describe them - and therefore the theories are incapable of doing so

Black holes and the big bang are therefore two examples of massive singularities which can't be described through QM or GR......

of course, maybe superstrings may provide a unified theory.... who knows?



*i can recommend Brian Greene The fabric of the Cosmos "The new Hawking only better" according to the Times....

 

[Bronze Dog]

[Derail]

Okay, we've got large and massive objects (stars, galaxies, etcetera), small and light objects (all the various stuff made in atom smashers and individual particles), small and massive objects (black holes, early, early universe)...

But what about large and light objects? Are there any?

[/Derail]

 

[GreedyAlgorithm]

[Derail]

Okay, we've got large and massive objects (stars, galaxies, etcetera), small and light objects (all the various stuff made in atom smashers and individual particles), small and massive objects (black holes, early, early universe)...

But what about large and light objects? Are there any?

[/Derail]

Hm, I think nothing is large and light.

 

[ponderingturtle]

[Derail]

Okay, we've got large and massive objects (stars, galaxies, etcetera), small and light objects (all the various stuff made in atom smashers and individual particles), small and massive objects (black holes, early, early universe)...

But what about large and light objects? Are there any?

[/Derail]

No if you really wanted a good derail, bring up magnetic monopoles, and how convient it would be if they actualy existed.(two line proof that charge is quantized)

 

[Bronze Dog]

No if you really wanted a good derail, bring up magnetic monopoles, and how convient it would be if they actualy existed.(two line proof that charge is quantized)

[Continued Derail]

Thought they had a cool use for a magnetic monopole in Outlaw Star: Gene got himself sent to a prison planet so that he could spring out a prisoner who knew the way to the Galactic Leyline. He brought along a magnetic monopole compass (Two monopole halves) that got put in a locker. He grabs the compass during a riot and sent to the high gravity portion of the prison at the North Pole.

The prison planet is a large planet with a high rotation speed: At the equator, it's only 3 G's. At the poles, it's 10. It also has a strong magnetic field to generate Star Trek-style interference, making it harder to get outside help in escaping.

Anyway, Gene gets to the North Pole and breaks the monopole compass in half. One half sinks into the ground. The other half starts lifting him up and he struggles to attach it to his belt while his new friend gets a grip on him. They float up into the upper atmosphere, undisturbed by guards (since they figured no one would try to take off from the high-gravity poles) where the Outlaw Star and crew snatch them up.

Then, a few years later, I realized that it wouldn't be a comfortable trip up for Gene, since he weighed 10 times as much, and was carrying 10 times the weight of his friend and my brain exploded.

[Continuing Derail]

 

[FireGarden]

The uncertainty principle in general applies to conjugate pairs of coordinates, the most commonly used example being position/momentum and energy/time, although there are others. If you have "nothing", however you define it, it cannot be described by any coordinates since there is nothing there to possess either position, momentum or anything else. Therefore no uncertainty priciple can apply to nothing (unless of course you are uncertain whether it's really nothing ).

Brilliant answer! But unfortunately it puts me back at square one.

Usually when people are talking about "something coming from nothing," they're not talking about this kind of absolute "nothing" that I usually associate with the inside of certain posters' heads.

I know. But this a particular argument. I've already suggested virtual particles in a vacuum. But it wasn't good enough!

 

[Dancing David]

We can't know what there was or wasn't prior to the big band starting to play, nor can we see outside the concert hall.

But the nothing of 'ordinary vacum' definitly is subject to quantum fluctuations and generates virtual particles, there is the 'zero field energy' or something like that. So the nothing that we call vacum, the space time thingee is certainly capable of 'producing' stuff from 'nothing'. But then it isn't nothing.

What is nothing is our knowledge of the universe before the big band struck up it's tune.

So while you can't directly use HIP (Indetermancy principle) to say that this is how the universe started, there are plenty of wierd things it might have been analogous to.

Like virtual particles, although Guth and the 'budding universe' seems to be popular, it is recursive and doesnt say much about ultimate origins.

 

[69dodge]

from Through the Looking Glass by Lewis Carroll:

'I see nobody on the road,' said Alice.

'I only wish I had such eyes,' the King remarked in a fretful tone. 'To be able to see Nobody! And at that distance, too! Why, it's as much as I can do to see real people, by this light!'

 

[FireGarden]

Great quote, Dodge!

We can't know what there was or wasn't prior to the big band starting to play, nor can we see outside the concert hall.

In the case of the universe, prior means outside. Because time is as much a part of the universe as any other dimension. That's a point I always bring up whenever people talk about a cause of the big bang. Without time to order events, how do you know which is the cause and which is the effect?

What is nothing is our knowledge of the universe before the big band struck up it's tune.

To get around your use of "before" and maintain the analogy...

We are all players in the Big Band (Ellington, of course), we have no knowledge of anything which is outside the Big Band. (Think of America and its knowledge of the outside world! --- Joke!)

 

[daenku32]

Since UP is driven from existing in space-time, without it, who's to say UP still applies (at least in the way it's defined). When you don't have the limitations of space-time all kinds of possibilities pop-up.

 

[Soapy Sam]

Hm, I think nothing is large and light.

Which brings us back to spacetime rather neatly.(Or at least to the vacuum which fills it).

And cautions us against using language to describe concepts it does not well encompass.

 

[Dark Jaguar]

Since UP is driven from existing in space-time, without it, who's to say UP still applies (at least in the way it's defined). When you don't have the limitations of space-time all kinds of possibilities pop-up.

Well then you've taken it out of scope. That's a variable outside the class and so... sorry the metaphors I'm thinking of right now are incredibly boring... not nearly as lovely as the orchastra hall.

Anyway my point is that if you take it outside what it was intended to describe of course it just isn't valid any more. Newtonian physics is out of scope if you take a ride on a beam of light. Relativity is out of scope the moment you get down to too small a level (like if a sufficiently massive star collapses in on itself). Quantum physics then would be out of scope in the chickeniverse, where the elementary particle of the universe is an entire chicken in ours. It's important to understand that a theory of everything really means a theory of every aspect we've observed. If at some point some totally unexpected new phenomenon is detected, the theory of everything won't be any more and a new one will come up. If nothing new shows up ever, then it doesn't matter if there's more to the universe than what we can observe because it has no effect on us, so theory of everything it remains.

 

[FireGarden]

"Nothing" does have an effect on the physical universe.
The argument being somewhat semantic...

If A causes B, then when A is present B becomes present.

So what causes objects to fall? You can't just say gravity, because gravity is present near objects which don't fall.

Similarly,
What causes an isolated unstable atom to decay? Well, the existence of an isolated unstable atom is a part of the cause, but it can't be the whole story. So what else is part of the cause? Answer -- "nothing!" (To the best of our knowledge, since radioactive decay is understood as a random event).

I reckoned it was worth a try, but it's more philosophy than science!

 

[Cuddles]

"Nothing" does have an effect on the physical universe.
The argument being somewhat semantic...

If A causes B, then when A is present B becomes present.

So what causes objects to fall? You can't just say gravity, because gravity is present near objects which don't fall.

Of course we can just say gravity. Gravity causes any object it acts on to fall, unless there is something stopping it. In my case, the EM forces between me and my chair are much stronger than the gravitational force between me and anything else, so I don't fall to the centre of the Earth. For the Moon, it is falling, but because it is also moving sideways it keeps missing. If you can find any case where gravity is present without an object falling then you have found a case where there is no object.