# Empty Space

1. Nov 29, 2008

### Ranger Mike

Does Empty Space have Mass?
Does Empty Space have Energy?

from a previous post i learned that energy is everywhere. Even Empty Space. zero point energy. correct?

never mind , i found the answers

Last edited: Nov 30, 2008
2. Dec 2, 2008

### remix220

Could you tell me! I would love to know!
I love physics, but I have soooooo much too learn.
I don't know if I'm right, but being that energy is a "thing" that would make it a "stuff". Even particles so small have mass, no?

3. Dec 2, 2008

### atyy

"In such cases, we seem to be driven to deduce that if this mass-energy is to be located at all, it must be in this flat empty space ..." Penrose, The Emperor's New Mind, http://books.google.com/books?id=oI0grArWHUMC&printsec=frontcover#PPA285,M1

4. Dec 2, 2008

### Ranger Mike

remix220
I found a lot of my answers on this website in various forums.thesearch engine is great..i copied a lot of info for my own reference..not having to do home work is a blessing.

I copied this off a sight..but forgot where..

Actually you can. A given volume of space is a quantum system with excitations (particles/fields). You can directly talk about its entropy, energy and temperature.
If the volume is assumed to be truly empty you are asserting entropy=0 and energy =0 thus temperature = 0. (This is however impossible to actualize.)
__________________
Regards,
James Baugh

Dh of this forum was referenced..

DH is right. Deep intergalactic space is absolutely swarming with CMB photons. I forget how many per cubic meter but it is a huge number. That defines the temperature quite precisely. Mentallic please listen to what DH says. He is giving you the absolute straight dope.

n otherwise empty vacuum created on earth would be full of photons radiated off the walls of the box containing the vacuum. The temperature of a vacuum is the temperature of thermal radiation in the vacuum. It could be whatever, depending on the temp of the walls. If you use refrigeration to make the walls of the box 5 kelvin, then the temp inside will be 5 kelvin. If you make the walls 1 kelvin, the temp of the photons inside will be 1 kelvin.

It just happens that the temp of otherwise empty space (far enough out not to be affected by stars and stuff) is 2.728 kelvin. That's the temp of the swarm of CMB photons out there (which have a welldefined thermal energy bar-chart.)
So if you put a piece of metal out in deep space it will radiate off photons and absorb CMB photons until it settles into equilibrium 2.7 with the CMB photons and with the rest of space.

If you put a metal box around the piece of metal, to try to shield it from the CMB then the box itself will settle into equilibrium 2.7 and then it will be filled with its own 2.7 kelvin radiation. and then the original piece of metal will settle to the same 2.7 temp.

You can't shield against the 2.7 CMB temp unless you use some kind of refrigeration to cool the box.

This is somewhat of a misnomer. Space is not a pure vacuum. The space between stars and even galaxies has some stuff in it, called the interstellar and intergalactic medium. The interstellar and intergalactic medium intergalactic medium have all of the characteristics of an ionized gas, albeit a very, very tenuous one. Like any other gas, these media have a temperature, and this temperature can be extremely high, up to 108 Kelvins or more! So in one sense space is anything but "cold".

As a fellow newbie to this sight, Welcome..nice to know there are other carbon forms interested in questioning the current thinking...gotta go..I am late for a Flat Earth meeting..

5. Dec 2, 2008

### ZapperZ

Staff Emeritus
You still have to be careful with what you read, because I have a feeling that deep down, you still do not understand the fundamentals of such ideas.

There is a difference between classical empty space versus quantum "empty space". If you do simple quantum mechanics, these two are the same. However, if you start doing quantum field theory, then things can get rather exotic.

Notice that I said "CAN GET". It means that in most cases, these exotica are not significant. It would be misleading to think that these zero-point phenomena are that obvious and a factor all the time. They aren't. Even when they rear their heads, these are extremely small effects - look at the magnitude of the Lamb shift.

Furthermore, when you have "intergalactic medium", this is not a definition of "empty space". So you have now switched context by asking about a different "space", not the concept of "empty space" as defined, in principle, in physics.

Again, it is the context that is important, and one needs a bit of an understanding of the physics to be able to realize that.

We highly recommend that you do not quote sources from other forums on here. Per our Guidelines, only valid, reputable, and peer-reviewed sources are allowed.

Zz.

6. Dec 2, 2008

### Ranger Mike

ok sorry , i was in error, was only trying to help REMIX220

7. Dec 2, 2008

### remix220

Thank you both very much!

If we are talking about a "pure and empty vaccume", what exits in it? Just energy?

8. Dec 2, 2008

### atyy

There are different ideas from different theories.

In general relativity, a classical theory of gravity, electromagnetism, fluids, gases, etc, "vacuum" is a part of spacetime that is "flat". If spacetime is globally flat, then there must be matter somewhere in the "universe". If spacetime is not globally flat, but only locally, then some "energy" appears to be assigned to the flat portions.

In quantum field theory, which may be able to describe all forces except gravity, there is no such thing as "empty space". There are quantum fields everywhere, and "particles" are excitations of these fields. Then "vacuum" is considered to be the unexcited or ground state of these quantum fields.

There is no known way of putting general relativity and quantum field theory into a single framework.

9. Dec 2, 2008

### remix220

<then there must be matter somewhere in the "universe">
Yes, this where Dark Matter & Dark Energy would fall in., correct?

<There is no known way of putting general relativity and quantum field theory into a single framework>
I know a lot of the basics. So basicly, I know that GR states there is a mathematical equation for everything, while SR states that QM "Strings" is unpredictable and everything is based on probability, so when put together the equations start to fall apart and infinite answers come out. Poor Einstein...