[iacopo.russo (OP)]

Ron wrote to us to ask:

"Can space ever be described as empty when the electrostatic field of oscillations is always active allowing us to perceive the history of our universe?"

What do you think?

[Origin]

No.

[Colin2B]

"Can space ever be described as empty when the electrostatic field of oscillations is always active allowing us to perceive the history of our universe?"

Well Ron, you are right that the electromagnetic field is continually active in the form of light, radio waves including microwaves etc and these fill space.
I think what people mean by empty is no solid stuff, but even then there is hydrogen, charged particles, neutrinos, dust and other stuff.
So not empty at all

Edit: Whoops, overlap with Origin. He’s not as wordy as me 

[alancalverd]

It's defined as empty.

If you scatter stuff into an infinite space, you have created a universe of stuff separated by space.

[geordief]

It's defined as empty.

If you scatter stuff into an infinite space, you have created a universe of stuff separated by space.

So empty space is a model that works?

Does the model break down at all in extreme circumstances?

[Colin2B]

So empty space is a model that works?

Does the model break down at all in extreme circumstances?

Yes, when all the space is full 

[chiralSPO]

Space is "practically empty" for anybody used to how crowded it is on earth (ie the density of matter in our atmosphere is a couple million times greater than in "empty space.") But Earth's atmosphere is "practically empty space" compared to anything that lives in the sea or in the atmosphere of Jupiter. Even our rocky planet is "practically empty space" compared to the inside of a neutron star!

We can choose to describe the universe as an empty space that is populated with things, but there is no part of the actual universe that is completely devoid of things, leaving only space there... so that's a meaningless extension of the model.

We can also choose to describe the universe as a collection of fields, in which the field "is everywhere" and all "things" are only the distortions of one or more fields. In this sense, empty space is just boring fields (it cannot be empty of fields, but at the same time, fields are not things).

[geordief]

this sense, empty space is just boring fields (it cannot be empty of fields, but at the same time, fields are not things

Are fields objects? Are they objects with the potentiality to become "things"?

Or do they just exist as the potentiality to become measurements?

[geordief]

So empty space is a model that works?

Does the model break down at all in extreme circumstances?

Yes, when all the space is full 

Would that impossibility prevent the singularity in a BH from happening?

[evan_au]

Can we ever truly describe space as empty?

According to a current popular theory, "Cold and Empty" is the long-term fate of the universe (even though the official name of this event is "the heat death of the universe", it is not hot or dense).

As space expands, the temperature of the Cosmic Microwave Background Radiation (CMBR) declines.
- When the CMBR drops below a few nanoKelvins, the Hawking Radiation of black holes will be higher than the incoming CMBR, and black holes will start to evaporate.
- The average temperature of the universe asymptotically approaches absolute zero
- The average density of the universe asymptotically approaches zero

https://en.wikipedia.org/wiki/Heat_death_of_the_universe

[TommyJ]

For about 2500 years since Democritus till 2012, when the Higgs boson, discovered at the CERN, there might have been a question about emptiness between particles.
Today - definitely 'no'. The field is there.
If all the objects around us are constructed with particles and fields, the field might be called an object.

Object (noun)
1. A material thing that can be seen and touched.
2. A person or thing to which a specified action or feeling is directed.

A physical object or physical body (or simply an object or body) is a collection of matter within a defined contiguous boundary in three-dimensional space.

[geordief]

Is there any possibility that the Universe ,in its present configuration could actually leak  into (into what?) in the kind of way BHs leak into the Universe (Hawking radiation)?

If virtual particles   can appear and disappear can there be ,so to speak movement in the "opposite" direction?

[Origin]

Is there any possibility that the Universe ,in its present configuration could actually leak  into (into what?) in the kind of way BHs leak into the Universe (Hawking radiation)?

The universe cannot leak into anything since the is nothing outside of the universe to leak into.  Blackholes cannot leak into the universe, since they are already in the universe.

If virtual particles   can appear and disappear can there be ,so to speak movement in the "opposite" direction?

I don't know what you mean by that.

[geordief]

I don't know what you mean by that

Well apparently particles (via the virtual particle process) can appear out of nowhere**

Can they similarly disappear into nowhere (causing the universe itself to leak in a similar way to black holes)?

**I don't personally understand  how virtual particles work,except for learning that some physicists wish they had never been so named...

[geordief]

The universe cannot leak into anything since the is nothing outside of the universe to leak into. 

If there is anything to multiverse theory might that imply  the possibility of a space separate from "the Universe"  that things could "leak into"?

[Origin]

If there is anything to multiverse theory might that imply  the possibility of a space separate from "the Universe"  that things could "leak into"?

I am not a fan of the multiverse hypothesis, so I can't help you there....

[Halc]

I'm sort of answering a bunch of questions. This is not a long answer to one question.

Is there any possibility that the Universe ,in its present configuration could actually leak  into (into what?) in the kind of way BHs leak into the Universe (Hawking radiation)?

This depends heavily on one's definition of 'universe', but there is such an equivalence:

A black hole event horizon is divider between spacetime events which are in the causal past of other specific events (in this case future-null-infinity), and those that are not.
Similarly, due to the acceleration of expansion, an event horizon forms relative to any location in space dividing spacetime events into those that lie in the causal past of the location in space and those that do not. This is sort of similar to a Rindler horizon in a properly accelerating reference frame. In all those cases, there is radiation similar to Hawking radiation, leaking energy from outside the event horizon to inside it. For a Rindler horizon the radiation is called Unruh radiation, and I don't know the name of the equivalent radiation for the horizon that forms due to dark energy.

- - - -
Concerning how the definition of 'universe' might effect things being able to enter or exit it:

If the universe is defined as all points in space currently on our side of this event horizon, then material (galaxies, etc) regularly exit this universe since the horizon is currently about 16 billion LY in radius and growing only slightly, so galaxies out there are increasing their proper distance from us at over light speed and are thus exiting this universe. No, you don't see them disappear as they fall through the event horizon any more than you see a rock blink out when you drop it into a black hole.

If the universe is defined as the visible universe, it is currently about 48 BLY in radius and growing at a rate of over 4c. New material moves into that from outside over time, which is sort of the opposite of the above.

If the 'universe' is defined to be all of spacetime, then it is a closed system by most models and there is nowhere and no time for things to exit or enter.

- - - -
Concerning the 'multiverse' bit, there are at least five different kinds of multiverse (and thus no single 'the multiverse hypothesis'), some of which are accepted by pretty much all cosmologists, and some by hardly any of them.

If by multiverse, you mean many-worlds, that interpretation of quantum mechanics does not actually posit that the universe undergoes some sort of magical split into two separate places, let along two places where it is meaningful for things to move between.

[geordief]

I'm sort of answering a bunch of questions. This is not a long answer to one question.

Thanks. That was interesting and appreciated (no ,I don't  know enough about the different multiverse theories  to expand on what  I may have had in mind)

[Black hole]

Ron wrote to us to ask:

"Can space ever be described as empty when the electrostatic field of oscillations is always active allowing us to perceive the history of our universe?"

What do you think?

Inner space is full of visual matter and matter that is beyond human vision . Outer space , an exterior may be empty of all matter . Maybe in the future we can provide a more accurate answer when we have developed the ability to travel or observe beyond our present means .

[ukmicky]

Is there any possibility that the Universe ,in its present configuration could actually leak  into (into what?) in the kind of way BHs leak into the Universe (Hawking radiation)?

The universe cannot leak into anything since the is nothing outside of the universe to leak into.  Blackholes cannot leak into the universe, since they are already in the universe.

If virtual particles   can appear and disappear can there be ,so to speak movement in the "opposite" direction?

I don't know what you mean by that.

You say the universe cannot leak into anything since there  is nothing outside of the universe to leak into. However do we know that for sure. I would say our currently understanding of the universe is not good enough to disregard many possibilities , We simply don’t know enough.

It’s possible that what we consider to be the  universe is not the full story . There is also the multiverse theories and also a theory that dark energy could be caused by those multiverses somehow interacting with our universe.

It could be all tosh and like most people know very little on the subject but it’s people asking those questions that leads to new discoveries .