'Empty' space

[FlFishOn]

If you were able to head out toward Andromeda, say you go 1,100,000 LY, half way more or less, What would you find? Let's sample a cubic region 100 LY on a side. Would you enclose any stars? My gut says no. Would you enclose anything bigger than a molecule?

Now do the same thing 2 LY toward Proxima Centauri. Smaller cube, say .01 LY on a side. A book I just read suggested that a density of one proton per CC could be expected. What else would you find? Would the density be 1000x that of the first sample? 10^9? Feel free to guess away. No need to show your work.

[chrisnice]

Are you trying to find somewhere with no black people?

[MelchyBeau]

there are things called rogue or hypervelocity stars. Basically these stars have escaped the galaxies gravitational pull and are either leaving, or have left the galaxy. These are fairly rare though.

Melch

[HLMencken]

[ QUOTE ]
Are you trying to find somewhere with no black people?

[/ QUOTE ]

/images/graemlins/grin.gif

[HLMencken]

http://news.bbc.co.uk/olmedia/215000/images/_218121_mars_bar300.jpg

[cambraceres]

Henning Geinz is a scholar who has written an articulate succession of articles on this concept. The book is called "Nothingness: the science of empty space". In the book, there is one particularly interesting passage for your specific question

[ QUOTE ]
"...every particle has its antiparticle of opposite charge and that particle plus antiparticle are nothing but an excitation of the vacuum, accessible from the Dirac sea once there is enough energy for the transition. Conversely, every real particle-antiparticle pair can annihilate into a pure energy excitation of the vacuum. These are the results that count; and the uncertainty relation tells us that pair creation and pair annihilation happen in the vacuum at all times, in all places." -- page 205

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Now this is an idea that comes from an older consept in QM, and as this cannot be validated I do not want you to just accept it, it probably isn't true as it is. But, this is an interesting viewpoint, especially if you are fluent enough in the requisite disciplines.

Cambraceres

[FlFishOn]

This vacuum energy stuff makes me a bit uneasy, having only the smallest understanding of QM.

[cambraceres]

Yeah in retrospect my post may have been off topic, since you were obviously speaking in classical terms, it was more to give you a better understanding of what lies beneath, and to let those who are fluent see the relationship between the problems.

Take care

Cam

[Metric]

[ QUOTE ]
This vacuum energy stuff makes me a bit uneasy, having only the smallest understanding of QM.

[/ QUOTE ]
That's quite all right. As a teacher of mine has said, depending on where you're coming from with regard to your perspective on physics, a case can be made for the vacuum energy being:

1)infinite
2)not infinite, but enormous by any reasonable standard
3)zero
4)not zero, but tiny by any familiar standard

[IronDragon1]

[ QUOTE ]
[ QUOTE ]
This vacuum energy stuff makes me a bit uneasy, having only the smallest understanding of QM.

[/ QUOTE ]
That's quite all right. As a teacher of mine has said, depending on where you're coming from with regard to your perspective on physics, a case can be made for the vacuum energy being:

1)infinite
2)not infinite, but enormous by any reasonable standard
3)zero
4)not zero, but tiny by any familiar standard

[/ QUOTE ]

Don't forget about vacuum decay (http://en.wikipedia.org/wiki/False_vacuum)

[Copernicus]

[ QUOTE ]
If you were able to head out toward Andromeda, say you go 1,100,000 LY, half way more or less, What would you find? Let's sample a cubic region 100 LY on a side. Would you enclose any stars? My gut says no. Would you enclose anything bigger than a molecule?

Now do the same thing 2 LY toward Proxima Centauri. Smaller cube, say .01 LY on a side. A book I just read suggested that a density of one proton per CC could be expected. What else would you find? Would the density be 1000x that of the first sample? 10^9? Feel free to guess away. No need to show your work.

[/ QUOTE ]

My guess would be the ratio of matter is 10^12 on average if you pick two random areas, one closer than the other. Even though the universe is thought to be expanding, the "outer regions" arent expanding faster than the nether regions, so the density should be pretty uniform.