[Pmb]

I'd like to point out that physicists don't make attempts to define things like "nothing." It serves no useful purpose.

[njskywalker]

Nothing is really super possibility of everything. Space is nothing yet infinitely dense with energy. All matter such as stars radiates into space/ nothing. thus making space a pure sea of energy . Nothing is really everything.

[Pmb]

Space is nothing yet infinitely dense with energy.

That's quite wrong. Where did you ever get that idea from?

I'll just never understand where some of you folks get these crazy ideas from!

[Thibeinn]

Nothing may just be something we are unable to perceive with our senses or detect with our instruments.
 
Here is a thought experiment for everyone...
 
Your dog can speak English (or whatever your native language is).  Dogs can hear sounds Humans cannot.  Your dog hears a sound which is beyond the range of Human hearing and asks, "Did you hear that?"  You reply, "I heard nothing."
 
The sound is real to your dog so it is something to him. The sound is not real to you so it is nothing to you.  Therefore, you will decide there was no sound when, in fact, there was a sound.
 
This is true with all the senses.
 
A long time ago, atoms were nothing (we didn't know they existed because we couldn't detect them) but now they are something (we know they exist because we can detect them).
 
The nothing which some state the Universe came from may just be something we cannot perceive or detect as yet. Therefore, we currently believe it is, and call it, nothingness.
 

[dlorde]

A long time ago, atoms were nothing (we didn't know they existed because we couldn't detect them) but now they are something (we know they exist because we can detect them).

The unknown isn't nothing. Atoms existed before we knew of them, they were unknown, not nothing.

[Bill S]

you could equally well say that there is nothing between every atom in that single, solid something; but does that really help?

It would certainly not help unless you defined nothing, which, it seems scientists do not do.

[Bill S]

I'd like to point out that physicists don't make attempts to define things like "nothing." It serves no useful purpose.

An interesting comment, Pete.
Apart, perhaps, from "infinity" what else is "like" nothing?
If defining nothing serves no useful purpose, why is it so commonly used, especially in popular science? 

[percepts]

Nothing is it's own definition. It means you are wasting your time looking for or trying to define nothing. By definition, nothing is exactly that, nothing.

The problem is you are asking the wrong question based on your probably correct assumption that there is something there but at the same time your incorrect assumption that it's called nothing when it should be called "something else unknown". Just calling the unknown and/or undefined "nothing" has confused you and apparently many others too.

[JP]

I'd like to point out that physicists don't make attempts to define things like "nothing." It serves no useful purpose.

An interesting comment, Pete.
Apart, perhaps, from "infinity" what else is "like" nothing?
If defining nothing serves no useful purpose, why is it so commonly used, especially in popular science? 

Scientists worry about defining terms when those terms, precisely defined, yield something useful in terms of physical models or theories.  The problem with the concept of "nothing" as an absolute is that it doesn't help with our theories in any way.  We can talk about the absence of things or the absence of certain properties in a precise way, and that can be useful: for example, a region of space without matter or energy is meaningful and useful, but that is hardly "absolute nothingness."

This is different from the concept of infnity.  Infinity, unlike "nothing" is a useful concept.  We can and do use infinity in our models.  We don't use "nothing" in our models.  (This is setting aside the question the physical meaning of infinity, which we've discussed at length elsewhere.)

[njskywalker]

Nothing is it's own definition. It means you are wasting your time looking for or trying to define nothing. By definition, nothing is exactly that, nothing.

The problem is you are asking the wrong question based on your probably correct assumption that there is something there but at the same time your incorrect assumption that it's called nothing when it should be called "something else unknown". Just calling the unknown and/or undefined "nothing" has confused you and apparently many others too.

Even nothing is something.