Are there theories in physics that suggest matter is an illusion?

[bostonnew]

Hi all,

I was wondering if anyone is aware of any theories in physics that don't rest on the assumption that matter exists.

I've heard a few theorists (both particle physicists, string theorists, and mathematicians) describe how it becomes very hard (if not impossible) to describe what an object or a particle really is once you zoom in enough. In other words, the question of whether fundamental particles really exists can become somewhat meaningless as math becomes the only language that correctly describes reality at that level.

Could it be that the universe only consists of energy? And that matter is thus an illusion?

I'm sure someone must have theorized about this. Any thoughts?

Thanks!

 

[gneill]

Could it be that the universe only consists of energy? And that matter is thus an illusion?

If it's an illusion it's a very good one, and I for one believe that I've gotten my money's worth

 

[Drakkith]

Why would matter not exist? We've measured something with an electric charge of -1 with a specific mass that we can interact with, it's labeled as an electron. Does it matter if what it "really" is is different from what we think it is? That wouldn't change any of the properties of it or change the way it interacts. It would still be an electron! I'd say it's a matter of definition rather than what "really" exists or not.

 

[bostonnew]

If it's an illusion it's a very good one, and I for one believe that I've gotten my money's worth

I agree, I'm not complaining at all. I cherish it just as much as my free will:-)

 

[bostonnew]

Why would matter not exist? We've measured something with an electric charge of -1 with a specific mass that we can interact with, it's labeled as an electron. Does it matter if what it "really" is is different from what we think it is? That wouldn't change any of the properties of it or change the way it interacts. It would still be an electron! I'd say it's a matter of definition rather than what "really" exists or not.

I agree it's a matter of definition. Certainly the electron doesn't exist in the same way as laypeople would say that a rock exists. With quantum theory it just becomes very unclear what we mean by existence.

But my point is more practical than anything. To my understanding, all theoretical developments in physics attempt to remain consistent with the theory of relativity; which explicitly builds on the assumption that matter exists. I'm just wondering if we got rid of that assumption perhaps someone could develop a simpler way to unify the forces we know of.

 

[Drakkith]

I agree it's a matter of definition. Certainly the electron doesn't exist in the same way as laypeople would say that a rock exists. With quantum theory it just becomes very unclear what we mean by existence.

But my point is more practical than anything. To my understanding, all theoretical developments in physics attempt to remain consistent with the theory of relativity; which explicitly builds on the assumption that matter exists. I'm just wondering if we got rid of that assumption perhaps someone could develop a simpler way to unify the forces we know of.

Why would an electron not exist just like a rock does? Quantum Mechanics is very clear about what exists and what doesn't. Also, different theories describe matter differently but still have to obey current known laws. Changing the definition of matter doesn't change any of that.

 

[Pengwuino]

Why would an electron not exist just like a rock does? Quantum Mechanics is very clear about what exists and what doesn't. Also, different theories describe matter differently but still have to obey current known laws. Changing the definition of matter doesn't change any of that.

Not at all. When you start getting into QFT, saying something is a particle equivalent in existence to how a rock exists gets sketchy. Throw in GR to the mix and you get all sorts of non-sense that people typically will hand-wave away the explanations for.

 

[bostonnew]

Why would an electron not exist just like a rock does?

Because of the uncertainty principle.

 

[khemist]

I would argue if you are here to ask this question, matter certainly exists in a particular limit.

 

[DaveC426913]

Whatever it is we experience when we probe for matter - be that hard little spheres or diaphanous energy fields that merely act like hard little spheres - that is what we call matter.

It exists because we detect it existing.

The question I think you are asking is: when we detect matter, are we detecting something physical?

To which the answer is a question of definitions: what do you mean by "physical"?

 

[Drakkith]

I agree with Dave.

 

[en bloc]

The illusion of matter( in my understanding ) is similar to the one of a spinning helicopter rudder( looking solid ). But in matter it's the electron, and it "feels solid".

 

[Jamma]

What do you mean by exist?

And I've never seen a theory of a physicist which rests on the assumption that matter doesn't exist, but I've not seen one resting on the assumption that it does exist. How exactly would this come into effect in a theory?

 

[1mmorta1]

Einstein theorized it. His answer? OF COURSE the universe consists of only energy, and lots of it: Matter is energy, at the rediculous exchange rate of Energy = Matter x C^2

So the theory your looking for is general relativity. Probably not the answer your looking for, but maybe thinking of it so simply will help you refine your question, or think of great new questions altogether.

 

[Thetes]

A good question! And one that has been around since ancient times. An Ionian Greek thinker Zeno proposed a number of paradoxes that while taken into consideration may well have predicted our uncertainties of motion and position: http://www.mathpages.com/rr/s3-07/3-07.htm

The argument goes back to cosmologies. Can we find mathematical rules that decide the universe. Or are they simply descriptions of what we observe.

 

[1mmorta1]

A good question! And one that has been around since ancient times. An Ionian Greek thinker Zeno proposed a number of paradoxes that while taken into consideration may well have predicted our uncertainties of motion and position: http://www.mathpages.com/rr/s3-07/3-07.htm

The argument goes back to cosmologies. Can we find mathematical rules that decide the universe. Or are they simply descriptions of what we observe.

I hate to break it to you, but, while Zeno was a great philosopher, most of his great teachings are contradicted by calculus. They didn't know about limits back in the day...

 

[Dale]

I have a basic aversion to discussing whether or not "X really exists". IMO it is a completely empty question, scientifically speaking. There is no really-exist-ometer that can test whether or not X "really exists" and the people asking the question never even bother to clarify what they mean by "really exist". At best it is philosophy, and usually it doesn't even rise to that level.

Theories which admit matter do very well at predicting the results of experiments performed to date. So any theory which doesn't admit matter would have to reduce to the matter theories for all known experimental conditions.

 

[Jamma]

I have a basic aversion to discussing whether or not "X really exists". IMO it is a completely empty question, scientifically speaking. There is no really-exist-ometer that can test whether or not X "really exists" and the people asking the question never even bother to clarify what they mean by "really exist". At best it is philosophy, and usually it doesn't even rise to that level.

Theories which admit matter do very well at predicting the results of experiments performed to date. So any theory which doesn't admit matter would have to reduce to the matter theories for all known experimental conditions.

Exactly.

I think the only way we could attempt to quantifying what "to exist" means without being self-contradictory or being a vacuous statement is for the definition to be "something that we can interact with" or "detect the effects of" and so on (and there are still some problems to be ironed out here). So in that light, of course matter exists.

Does energy exist? I'd say yes, that we don't consider it as a "physical" thing, to me, is irrelevant, especially since we can't meaningfully say what is "physical" and what isn't.

I think a really thought provoking question is "does the past exist?". Is it meaningful to say that one past exists any more than a different past which would lead to the same present? It seems not. You are then lead on to thinking, is it meaningful to say that any particular present is more "real" than another one for which we can't detect the difference? (this question can't really be separated from the above since we now know there is not actually any meaning to "the present" or "the past"). The "does a tree fall in the woods make a sound if no one hears it?" question sounds less silly than at first.


...
And look what's happened. I've lead myself down a horrid trail of useless philosophy. That's why you can't implement these sorts of things into a useful scientific theory!

 

[Thetes]

I hate to break it to you, but, while Zeno was a great philosopher, most of his great teachings are contradicted by calculus. They didn't know about limits back in the day...

Thanks for the opportunity to clarify, calculus has nothing to do with the validity of the paradoxes. Using limits means we are assuming continuity and thus infinite divisibility, exactly what Zeno paradoxes are about. So, it tells us to look at his continuous motion paradoxes [the dichotomy, achilies and the tortoise] rather than the discrete paradoxes [the stade, the arrow].

 

[Jamma]

Thanks for the opportunity to clarify, calculus has nothing to do with the validity of the paradoxes. Using limits means we are assuming continuity and thus infinite divisibility, exactly what Zeno paradoxes are about. So, it tells us to look at his continuous motion paradoxes [the dichotomy, achilies and the tortoise] rather than the discrete paradoxes [the stade, the arrow].

But Zeno implicitly uses continuity for his paradoxes by insisting that we can always look at half the distance between things.

To be honest, you don't really need limits to see the paradox in Zeno's paradoxes- his paradoxes work by insisting something which isn't true, namely that an infinite sum must be infinite (although there are other ways of looking at it).

 

[jeebs]

well it's not really a hard, solid, concentrated collection of "stuff", is it?

This response might sound naive because I'm only just getting introduced to quantum field theory, but can't we thinking of particles not as isolated clumps of stuff, but rather that each species of particle is really a localized disturbance in an all-pervading field?

What I mean is, the brief outline I have in my head of what QFT involves is that we have things like lepton fields and quark fields extending throughout spacetime, and what we consider particles are localized places where these fields have non-zero values.

Then we could start thinking of stuff we imagine as solid, tangible "matter" (eg. electrons) as something conceptually no different from light - which is a traveling disturbance of the electric/magnetic fields. We have no problem thinking that light isn't solid "stuff", so surely this extends to all other stuff that we traditionally consider matter if we consider all stuff as fields?

but then what does it really mean to say a "field" has a certain value at a certain position, what the hell is a field really? I'd like it if someone here who really knows their QFT could either elaborate or rubbish what I've just said.

*actually something just occurred to me about a difference between light and the matter fields - light can only travel at c, as noted from Maxwell's wave equation, but particles with "mass" can have a range of velocities, so there has to be something different there. Maybe I'm spouting a load of nonsense here...

 

[DaveC426913]

...[Zeno's] paradoxes work by insisting something which isn't true, namely that an infinite sum must be infinite...

This is an elegant, concise and compact explanation of why Zeno's paradoxes are false.

I had not thought of it this way before. A two line program in my brain has now been replaced by a single line. I have one more memory register in which to store a thought (or more likely a TV jingle).

 

[Jamma]

Haha, use that extra space wisely!

 

[Aaron William]

Matter (physics) - that which occupies space and has a rest mass

No arguments with that. I think OP's initial inquiry was about whether or not the smallest particles actually occupies a volume of space or if it, as Dave put it, is a "diaphanous" shell of energy. Diaphanous - my new word of the day.

This leads to more nebulous questions about "what is space" and the rabbit hole gets deeper...

Still it is worth doing the thought experiments. That is what Einstein did.

 

[Jamma]

Personally, I've never believed space "exists" in the sense of matter existing in that you can explain it with the mere existence of particles. I think that space really is just the relationship between particles- for example, would space exist (need it exist?) if there are no/only one particle in the universe?

Then again, there could be a simple reason for why this description totally fails. And I don't claim there is any benefit/pragmatic difference from thinking about space in this way as opposed to some fabric in which particles live.

 

[Oudeis Eimi]

well it's not really a hard, solid, concentrated collection of "stuff", is it?

This response might sound naive because I'm only just getting introduced to quantum field theory, but can't we thinking of particles not as isolated clumps of stuff, but rather that each species of particle is really a localized disturbance in an all-pervading field?

What I mean is, the brief outline I have in my head of what QFT involves is that we have things like lepton fields and quark fields extending throughout spacetime, and what we consider particles are localized places where these fields have non-zero values.

Then we could start thinking of stuff we imagine as solid, tangible "matter" (eg. electrons) as something conceptually no different from light - which is a traveling disturbance of the electric/magnetic fields. We have no problem thinking that light isn't solid "stuff", so surely this extends to all other stuff that we traditionally consider matter if we consider all stuff as fields?

but then what does it really mean to say a "field" has a certain value at a certain position, what the hell is a field really? I'd like it if someone here who really knows their QFT could either elaborate or rubbish what I've just said.

I'm nowhere near an expert in QFT, but AFAIK this is a correct description, with some
caveats.

The first is that the excitations need not be localised at all - they can occupy arbitrary
volumes of space. A second one is the concept of the value of the field. For a classical
field, a single (scalar or not) value is all you need, but a quantum field, like all quantum
quantities, behaves a lot like a stochastic variable, and thus needs (ideally) a full set
of moments <phi^n>, n from 1 to infinity, for a complete characterisation (though in
practice it often suffices with only the two first ones, <phi> and <phi^2>).

For an example of how this works, imagine the simplest scenario possible, that of an
ideal, non-interacting scalar field, and a single-quantum excitation given by the following
pure state: |Psi> = integral f(k) a*(k) |G>, with |G> the ground state of the field, and
f(k) a square normalisable function in momentum space with the correct weight. If you
try to compute the _value_ of the field, you'll get zero everywhere (despite not being
in the vacuum state). However, if you compute the momentum or the energy, which
depend on the squared field and its spatial and temporal derivatives, you'll get an
energy or momentum density that takes values in a support that's basically the Fourier
transform of f(k), and zero everywhere else. Thus, an ideal single-quantum excitation
can be considered as a 'bump' of energy and momentum of the field.

Of course, the above is not physical, as real fields are interacting, and the whole
scenario gets a lot more complicated, but it serves as both an illustration and as
a way to connect with the concepts already learned from non-relativistic QM.

*actually something just occurred to me about a difference between light and the matter fields - light can only travel at c, as noted from Maxwell's wave equation, but particles with "mass" can have a range of velocities, so there has to be something different there. Maybe I'm spouting a load of nonsense here...

Fields can be massless OR massive ;-)

 

[1mmorta1]

When I say Zeno's paradoxes are contradicted by calculus, I mean they are solved by calculus. Zeno wants to take their motion on to "infinity," which in todays world means taking the limit. Zeno's paradox was a big deal, but it is no longer puzzling.

 

[jeebs]

) an
ideal, non-interacting scalar field, and a single-quantum excitation given by the following
pure state: |Psi> = integral f(k) a*(k) |G>, with |G> the ground state of the field, and
f(k) a square normalisable function in momentum space with the correct weight. If you
try to compute the _value_ of the field, you'll get zero everywhere (despite not being
in the vacuum state). However, if you compute the momentum or the energy, which
depend on the squared field and its spatial and temporal derivatives, you'll get an
energy or momentum density that takes values in a support that's basically the Fourier
transform of f(k), and zero everywhere else. Thus, an ideal single-quantum excitation
can be considered as a 'bump' of energy and momentum of the field.

That's quite interesting. So now does the question "what is matter" become "what is energy" or "what is momentum"? And since these are both defined further in terms of quantities like time and distance, does that mean we get stuck and can't go any further with this?

eg. energy has dimensions of [mass][length]^2[time]^-2

I mean, can we really define what time or space or mass or charge etc. actually are, or do we just wind up going in circles defining each quantity in terms of the others?

 

[Thetes]

But Zeno implicitly uses continuity for his paradoxes by insisting that we can always look at half the distance between things.

It's not an implicit assumption. It's the stated premise.

To be honest, you don't really need limits to see the paradox in Zeno's paradoxes- his paradoxes work by insisting something which isn't true, namely that an infinite sum must be infinite (although there are other ways of looking at it).

Perhaps we just have different interpretations of the original question. And I by no means claim to have an authority on what they originally were. If we are talking about the dichotomy, then the premise is continuous space and continuous time. So if the original question is what point in space or time is the first motion then we have a problem, because motion doesn't begin at any particular point. It happens within the neighborhood of whatever delta epsilon combination we take for our limit. So there are an infinite number of 0 distance/time first steps before we start to get anywhere.

 

[Oudeis Eimi]

That's quite interesting. So now does the question "what is matter" become "what is energy" or "what is momentum"?

Or rather, 'what are the fields'?

And since these are both defined further in terms of quantities like time and distance, does that mean we get stuck and can't go any further with this?

eg. energy has dimensions of [mass][length]^2[time]^-2

I mean, can we really define what time or space or mass or charge etc. actually are, or do we just wind up going in circles defining each quantity in terms of the others?

I guess every theory needs a set of primitive objects, there's no way around that.