Density of Inter Galactic Space

[Bisonhead]

After playing with the scale of the universe tool and watching an hour and a half of fascinating (but very American) space exploration narrated by Alec Baldwin I have started thinking about the gaps between galaxies.

I am aware that there are trace elements occupying the space between galaxies and that 'dark matter' (which we cant detect, quantify or even be sure exists) accounts for around 80-90%of all matter.

What I would like to know is how much of this stuff occupies say, 1m3. Also, if anyone has a rough guess as to how many cubic meters there are in the known inter galactic space that'd be much appreciated. When my mind has put itself back together I will thank you!

[LordGrover]

Bisonhead said:

... if anyone has a rough guess as to how many cubic meters there are in the known inter galactic space ...

If even possible, I suspect such a ridiculously large number it's pretty much meaningless.

[NNH]

LordGrover said:

Bisonhead said:

... if anyone has a rough guess as to how many cubic meters there are in the known inter galactic space ...

If even possible, I suspect such a ridiculously large number it's pretty much meaningless.

1.2 * 10^70 cubic metres.

The universe is 15 billion years old, so the knowable universe is within a 15 billion light-year radius. A light-year is 9.46 * 10^12 metres (speed of light is 300,000 m/s), so the volume in a 15 billion light-year radius sphere is 1.2 * 10^70 cubic metres. To a reasonable approximation, all space is intergalactic (certainly well over 99%).

[scorp]

According to this ( http://hypertextbook.com/facts/2000/ChristinaCheng...) the average density of the entire universe is ~5x10^-30 g/cm3, a couple of hydrogen atoms per cubic metre. Intergalactic space (ignoring virtually ALL of the dense stuff) would be a lot (trillions of times?) lower.

[stew-S160]

NNH said:

LordGrover said:

Bisonhead said:

... if anyone has a rough guess as to how many cubic meters there are in the known inter galactic space ...

If even possible, I suspect such a ridiculously large number it's pretty much meaningless.

1.2 * 10^70 cubic metres.

The universe is 15 billion years old, so the knowable universe is within a 15 billion light-year radius. A light-year is 9.46 * 10^12 metres (speed of light is 300,000 m/s), so the volume in a 15 billion light-year radius sphere is 1.2 * 10^70 cubic metres. To a reasonable approximation, all space is intergalactic (certainly well over 99%).

Close...universe is 13.82 billion years old. Obvservable universe is 13.82 radius. Actual universe is MUCH larger due to expansion.

[Bisonhead]

scorp said:

According to this ( http://hypertextbook.com/facts/2000/ChristinaCheng...) the average density of the entire universe is ~5x10^-30 g/cm3, a couple of hydrogen atoms per cubic metre. Intergalactic space (ignoring virtually ALL of the dense stuff) would be a lot (trillions of times?) lower.

Awesome, that is the kind of thing I was looking for.

We can all conceptualise 1m3 and the relative size of an atom. We can pretty much comprehend the scale of the objects in the universe as well. It is amazing to think that objects like our planet, our sun, our galaxy despite their scale, are pretty much meaningless in terms of the volume or space they occupy in the universe.

As for the space between galaxies...pretty lonely place!

[MOTORVATOR]

Are you sure you can conceptualise that cubic metre?

Is a cubic metre the same locally as it is 13b light years away?

Or would metric expansion render your measurement and concept invalid?

[Bisonhead]

MOTORVATOR said:

Are you sure you can conceptualise that cubic metre?

Is a cubic metre the same locally as it is 13b light years away?

Or would metric expansion render your measurement and concept invalid?

When I get there I'll have a look at let you know...if you are still around

[MOTORVATOR]

Bisonhead said:

MOTORVATOR said:

Are you sure you can conceptualise that cubic metre?

Is a cubic metre the same locally as it is 13b light years away?

Or would metric expansion render your measurement and concept invalid?

When I get there I'll have a look at let you know...if you are still around

Don't forget you'll need a really really big ruler to do it. I think!

[Bisonhead]

MOTORVATOR said:

Bisonhead said:

MOTORVATOR said:

Are you sure you can conceptualise that cubic metre?

Is a cubic metre the same locally as it is 13b light years away?

Or would metric expansion render your measurement and concept invalid?

When I get there I'll have a look at let you know...if you are still around

Don't forget you'll need a really really big ruler to do it. I think!

Surely if I take a ruler with me it'll expand too??

[MOTORVATOR]

Bisonhead said:

MOTORVATOR said:

Bisonhead said:

MOTORVATOR said:

Are you sure you can conceptualise that cubic metre?

Is a cubic metre the same locally as it is 13b light years away?

Or would metric expansion render your measurement and concept invalid?

When I get there I'll have a look at let you know...if you are still around

Don't forget you'll need a really really big ruler to do it. I think!

Surely if I take a ruler with me it'll expand too??

Hmm a quandary indeed. Two rulers?

[Simpo Two]

If a metre ruler is subject to metric expansion, is a yard ruler subject to imperial expansion...?


Perhaps you could mount two rulers in such a way as to counteract the expansion, as they did with pendulum clocks.

[MOTORVATOR]

Not quite Simpo, imperial expansion occurs through the addition of droids.

[andy_s]

Bisonhead said:

It is amazing to think that objects like our planet, our sun, our galaxy despite their scale, are pretty much meaningless in terms of the volume or space they occupy in the universe.

...and when you take into account how much 'space' there is in the atoms themselves then things look even spacier. Enough room to swing Schrodinger's cat. If it is alive, (don't look!).