Can particles appear from "actual" nothing including no space?

[gary0033]

TL;DR Summary

In discussion with a chemist friend who says that the universe could have begun from a particle released via the Heisenberg Uncertainty Principle. Even if there was no space in the beginning.

Hi and thank you for answering questions on complex subjects like this. I’m a non-scientist who is jealous of your brain capacity!

Recently, in a discussion with a chemist, he said the particles appearing from nothing might have been the initial cause of the universe. I’m familiar with the Heisenberg Uncertainty Principle (sort of!) and that it has been proven that particles can indeed appear seemingly from nothing.

From my limited understanding, “nothing” in this context means existing space containing with quantum fields.

I pointed out that his theory might not work for the creation of the universe because in standard Big Bang cosmology, there was no space, time, matter or energy “before” the Big Bang. Therefore, it seems to me that a particle/anti-particle pair cannot appear from actual nothing (meaning no space, time, matter or energy).

He responded by saying that the background doesn’t matter:

“Several of the main theories of quantum gravity (especially loop quantum gravity), which are still under development, are “background independent,” meaning that within Einstein’s relativistic understanding of the universe, entities are located with respect to one another only, not with respect to the spacetime manifold. The equations of loop quantum gravity are not embedded in or even dependent on space and time. Instead, they give rise to space and time as emergent properties. This background independence is not a unique feature of these theories of quantum gravity; they are a direct result of Einstein’s theory of general relativity, and have been explored by physicists for over a century.”

It's fine if this is correct but I don’t have the knowledge to know. Is there any evidence that particles can appear from actual nothing?

 

[Drakkith]

Is there any evidence that particles can appear from actual nothing?

No. There is no evidence for this. The current universe is, apparently, composed of 'something', so that is what we observe.

 

[PeterDonis]

From my limited understanding, “nothing” in this context means existing space containing with quantum fields.

That's the usual meaning when such a claim is made, yes. (Note that it should be "existing spacetime", not "existing space".)

I pointed out that his theory might not work for the creation of the universe because in standard Big Bang cosmology, there was no space, time, matter or energy “before” the Big Bang.

That depends on the model. This property is true for the simplest FRW models (which were the first ones considered by cosmologists, way back in the 1920s), but it is not true for all models. In particular, it is not (necessarily) true for inflation models; in "eternal inflation" models, spacetime extends infinitely back in time, even though the universe we know does not (it was created at the end of inflation).

He responded by saying that the background doesn’t matter

That's not the same as saying there is no spacetime (or something from which spacetime emerges) at all. Loop quantum gravity, for example, does not say spacetime just pops into existence from "nothing". It says that spacetime emerges from underlying loop stuff, as do all other quantum fields. The underlying loop stuff is not "nothing".

 

[A. Neumaier]

Summary:: In discussion with a chemist friend who says that the universe could have begun from a particle released via the Heisenberg Uncertainty Principle. Even if there was no space in the beginning.

“nothing” in this context means existing space containing with quantum fields.

Whenever the state is not the vacuum state, it is not nothing. The particles will be created from the fields.

On the other hand, the vacuum state is time invariant, hence persists forever as vacuum state.

 

[gary0033]

I had someone tell me this is a cosmology question, not a physics question. Actually, it's not a cosmology question. It's a question about particle physics. The cosmology element was only included to provide the context of the question.

 

[weirdoguy]

cosmology question, not a physics question

Cosmology is part of physics.

 

[PeterDonis]

I had someone tell me this is a cosmology question, not a physics question.

Who? I don't see anyone telling you that in this thread.

That said, when your thread summary uses the phrase "the universe could have begun", it is not unreasonable to include cosmology in the discussion.

Also, note that this thread is in the Quantum Physics forum, which keeps it pretty general.

 

[EPR]

Well, quantum theory has little to say. It's just that very often you learn less about things if you take them apart than if you studied them collectively.

It depends on what you want to know. Few things seem fundamental - e.g. charge, spin, mass... while anger, solitude, dreams, depression and weather are higher order emergent phenomena. They are not properties of electrons or quarks or atoms.

At the bottom - it's just fields. Or perhaps strings/or loops.

And not surprizingly, we get nonsense when we probe the first moments. We get singularities which means we don't have a proper theory that can say anything meaningful about your questions.

 

[oknow]

The key phrase is "actual nothing." There is no true vacuum in a quantum system. What may seem to be empty space one moment can have virtual particles popping into it the next via random fluctuations. This is something known as zero-point energy. It arises from the uncertainty associated with every quantum system. The possibility exists that one such random fluctuation was substantial enough to create the entire observable universe.

 

[weirdoguy]

What may seem to be empty space one moment can have virtual particles popping into it the next via random fluctuations. This is something known as zero-point energy. It arises from the uncertainty associated with every quantum system.

That's not true, even though you can read a lot of such claims in pop-sci sources. What is true can be found summarised in these insights articles:
https://www.physicsforums.com/insights/misconceptions-virtual-particles/
https://www.physicsforums.com/insights/what-are-virtual-particles-intro/
https://www.physicsforums.com/insights/physics-virtual-particles/

 

[bobob]

The key phrase is "actual nothing." There is no true vacuum in a quantum system. What may seem to be empty space one moment can have virtual particles popping into it the next via random fluctuations. This is something known as zero-point energy. It arises from the uncertainty associated with every quantum system. The possibility exists that one such random fluctuation was substantial enough to create the entire observable universe.

Asfar as the original big bang goes, what exactly happened is an open question. Physics can only provide models going back to, maybe ##10^{-12}## seconds afterward. As far as "zero-point" energy goes, there is nothing that can be used to create something from nothing. What you see regarding Feynman diagrams showing such things are representations of a perturbation series and the ones which have particles popping into and out of existence due to "vacuum fluctuations," are always disconnected from any physical process. i.e., for any physical process, those diagrams can be removed and have no influence on a physical process.

 

[bhobba]

What Peter wrote is usually what is meant by the universe being created from nothing. For want of a better word, there is some underlying 'stuff' from which space-time emerges. The model that intrigues me most is eternal inflation:
https://en.wikipedia.org/wiki/Eternal_inflation

Thanks
Bill

 

[gary0033]

Cosmology is part of physics.

Correct. And, if you look at the actual question, this is not a question about cosmology - it's a question about particle physics.

 

[gary0033]

Who? I don't see anyone telling you that in this thread.

That said, when your thread summary uses the phrase "the universe could have begun", it is not unreasonable to include cosmology in the discussion.

Also, note that this thread is in the Quantum Physics forum, which keeps it pretty general.

A physics writer on another website (not this one), said he answers physics questions, not cosmology. That's who said it.

 

[jabberwok]

The first answer was the best one. We live in a universe that is composed of "something". We have no idea what the first nano seconds of the big bang were like or what actually existed or didn't exist before that. We have no reference to make judgements about "nothing" as it doesn't exist. Uncertainty does make virtual particles in our space time that part is correct. I highly doubt that uncertainty in nothingness created the big bang.

 

[gary0033]

That's the usual meaning when such a claim is made, yes. (Note that it should be "existing spacetime", not "existing space".)That depends on the model. This property is true for the simplest FRW models (which were the first ones considered by cosmologists, way back in the 1920s), but it is not true for all models. In particular, it is not (necessarily) true for inflation models; in "eternal inflation" models, spacetime extends infinitely back in time, even though the universe we know does not (it was created at the end of inflation).That's not the same as saying there is no spacetime (or something from which spacetime emerges) at all. Loop quantum gravity, for example, does not say spacetime just pops into existence from "nothing". It says that spacetime emerges from underlying loop stuff, as do all other quantum fields. The underlying loop stuff is not "nothing".

Loop quantum gravity is way above my pay grade. Does loop quantum gravity say that in addition to spacetime being a physical entity, that "loop stuff" is also some sort of physical entity? If so, what do we know about it?

 

[weirdoguy]

Uncertainty does make virtual particles in our space time that part is correct

No, it is not! "Virtual particles" is just a name for internal lines in Feynman diagrams, which are nothing more than just a calculation tool.

 

[gary0033]

Here's National Geographic scientists grappling with actual nothing:

 

[PeterDonis]

A physics writer on another website (not this one), said he answers physics questions, not cosmology.

Then it has nothing to do with the discussion here.

 

[bhobba]

Here's National Geographic scientists grappling with actual nothing:

These are popularisations of complex ideas. They are useful for the lay public to get a 'feel' for what is happening. But in making it accessible, exactitude is lost. Several modern theories have a phase called inflation. Some think inflation started from an actual something called the false vacuum decaying to the true vacuum:
https://en.wikipedia.org/wiki/False_vacuum_decay

Science advisors, mentors and other senior people here like to help people progress further than popularisations. Google is your friend, and if you google false vacuum and inflation, people can glean a better understanding. Studying the real thing is best, of course, but that will not happen overnight. Baby steps, perseverance and patience, are required. If you would like to make that journey do a post in the academic advising section, and people, including me, will be only too happy to advise you on how to go about it, depending on your background.

Thanks
Bill

 

[PeterDonis]

Some think inflation started from an actual something called the false vacuum decaying to the true vacuum:

That's not the start of inflation, that's the end of inflation. Inflation is what happens while the false vacuum is present, before it decays.

 

[bhobba]

That's not the start of inflation, that's the end of inflation. Inflation is what happens while the false vacuum is present, before it decays.

Egg on face . Of course. I could change my post and word it better but will leave it to show people we all make mistakes.

For the gory detail of Peter's correction:
https://ned.ipac.caltech.edu/level5/Guth/Guth3.html

Thanks
Bill

 

[*now*]

Whenever the state is not the vacuum state, it is not nothing. The particles will be created from the fields.

On the other hand, the vacuum state is time invariant, hence persists forever as vacuum state.

In being invariant, does this suggest forever in more than one direction?

 

[*now*]

A recent paper might help the thread in general,
https://www.frontiersin.org/articles/10.3389/fspas.2020.629466/full
Primordial Fluctuations From Quantum Gravity
Francesco Gozzini and Francesca Vidotto
Published May 4, 2021

• We study the fluctuations and the correlations between spatial regions generated in the primordial quantum gravitational era of the universe. We point out that these can be computed using the Lorentzian dynamics defined by the Loop Quantum Gravity amplitudes. We evaluate these amplitudes numerically in the deep quantum regime. Surprisingly, we find large fluctuations and strong correlations, although not maximal. This suggests the possibility that early quantum gravity effects might be sufficient to account for structure formation and solve the cosmological horizon problem.

—

I think from explanations that here, some points include that although there is spatial measurability, continuous Riemannian space is not in the picture, and there is no preferred time variable, but is compatible with time.

 

[Quarker]

If the universe arose from a true “nothingness,” it would be hard to explain why quantum fields can only have the values they do. Physics can’t say why there are only certain types of particles that exist, instead of just a random quantum field static that one would expect. Or why these fields exist in a spacetime that enforces causality. Physics can only describe the universe, it can’t explain it.

 

[bhobba]

Physics can only describe the universe, it can’t explain it.

I think that depends on what is meant by explaining. However, any explanation requires some assumptions that are not explained by the explanation.

Thanks
Bill

 

[bhobba]

Read up on The Casimir Effect.

It is a widespread misconception the origin of the Casimir Effect is the result of vacuum particles popping in and out of existence. That is wrong. It is a manifestation of Van der Waals forces you likely learned about in Chemistry class:
https://www.sciencedirect.com/science/article/pii/S0370269316304567?via=ihub

Thanks
Bill

 

[weirdoguy]

The Casimir force arises because vacuum fluctuation modes are suppressed.

Again, you are repeating some pop-sci misunderstandings and proving my point. This issue has been discussed here multiple times. This Insight artciles are a good start:

https://www.physicsforums.com/insights/vacuum-fluctuation-myth/
https://www.physicsforums.com/insights/misconceptions-virtual-particles/
https://www.physicsforums.com/insights/what-are-virtual-particles-intro/
https://www.physicsforums.com/insights/physics-virtual-particles/

To answer this question directly, yes they can.

No, they can't. I think it would be a good idea to read the whole thread before answering, so that you won't repeat things that has been debunked.

 

[PeterDonis]

The OP question has been answered. Thread closed.