#BAFact: The volume of the Milky Way, our galaxy, is roughly 8 trillion cubic light years.

Our galaxy is pretty big. It's a flat disk about 100,000 light years across and a thousand light years thick. The volume of a disk is its area (pi x radius^2) times its thickness. So:

volume = pi x (50,000)^2 x 1000 = 8 trillion cubic light years

That's a whole lot of elbow room. A cubic light year is 10^39 = 1,000,000,000,000,000,000,000,000,000,000,000,000,00 cubic kilometers. Now multiply that by 8 trillion and now my head hurts. 

[Image credit: Spitzer Space Telescope: http://www.spitzer.caltech.edu/images/2351-sig05-010-Milky-Way-Bar-annotated-  Also, I made a couple of math errors due to my own haste and too much coffee this morning. My apologies to math nerds everywhere throughout the immense volume of space. ]
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33 comments
 
Yeah, but that's mostly a bunch of empty. If we did the Space Bag(tm) thing and packed the whole mess into a smaller space, it'd fit in a matchbox.
 
The Tentacles of Cthulu wrap through eternity. Or 100,000 lights years of it anyways.
 
isn't that 2.5t*pi cubic light years or ~7.85 trillion?
 
I wonder how much math goes into getting an estimated view perpendicular to the orbital plane as pictured above?
 
Last I checked, the best estimate of stellar density in the vicinity of our solar system was around 2.45x10^-3 stars per cubic light year.
 
I have affected everything in a 36 lightyear radius by merely existing.
Toby A
 
+Ronald Obermoser you affected me because I read your post, but I expect your affect on most of the things in that radius would be negligible at best. 
Toby A
 
+Ronald Obermoser I had a quick think: what about those matter-antimatter pairs that pop in and out of existence? I can't think of how your existence could possibly affect most of those. 
 
Well, gravity spreads at light speed doesn't it? So it would follow that my comparatively miniscule mass would tug on everything since the day I've existed. Now explain to me why I'm wrong, please. And yeah, I'm perfectly fine with the effect being negligible.
 
+Ronald Obermoser , your mass was not created.  It was just concentrated from the environment around you.  Unless you have moved your mass a significant distance from the Earth, the net center of gravity for the Earth is still the same.
 
100,000/1,000 = roughly the same ratio as a vinyl LP record.
Coincidence? Pink Floyd and Jimi Hendrix materialized at just the proper moment in time to make it something to ponder about.
 
But does the galaxy spiral counter-clockwise on the other side of the galactic equator?
 
+Ronald Obermoser In the most technical sense you could be considered correct.  Look at the explanation of the Total perspective Vortex from HitchHikers Guide.  However, Any effect you have at a distance of more than a few hundred meters (generously) is completely lost in the noise of everything else ALSO affecting the point you refer too as being affected so the net effect is zero or indistinguishable from other similar massed objects. 
 
It's the difference of affect and effect. Do I affect it? Technically yes. Do I have an effect on it / is that even measurable? Most definitely not. 
 
It's all in signal to noise ratio
Toby A
 
+Ronald Obermoser so, your mass has the affect of gravitational pull, but that's technically not you, it the atoms that make up your body. If you had never been born those atoms would still be in the vicinity of Earth having the same affect, and I suspect they've been doing it since long before you were born. So in regards to gravitational pull, your coming into existence had no affect.
Toby A
 
Prove me wrong. 
 
That's only tangentially related to what I said. 
Toby A
 
OK +Ronald Obermoser I concede your point. A lot of things have been experiencing the pull of gravity from a certain set of atoms for a long time, but only those things within 36 light years have experienced it while those atoms were grouped together as your body, so your original statement is correct, but only in the most stringently technical sense. 
 
To you this may be just a technicality, but to me it's also immensely beautiful. I have little chance to escape the boundaries of this planet during my lifetime. When I try to imagine that some elementary particle out there may feel an ever so slight tug that originated from that temporary group of particles that make up my body it makes me glad to be alive to be able to think these thoughts.
Toby A
 
OK, yes to me it is just a technicality. I do find the universe immensely beautiful, but not in the very small tug sense. BTW I just realised it's more complicated than I made it out to be. Because you're an organic creature (I presume) the atoms in your body are dynamic in the sense that which atoms are considered members of your body and which are not is always changing. Nevertheless, your original statement still holds true. 
 
I presume that ther's barely any of the particles left of the ones I started out with, if at all.
Toby A
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Yes, perhaps. That's a strange thought, isn't it?

Also, I don't want to dampen your sense of beauty, but I was just trying to think about the smallness of the gravitational force exerted by the mass of a human body over a distance of 36 light years and my brain nearly imploded! To say it's very small is the understatement of all understatements!
 
If you fire up Celestia, you an actually send yourself to intergalactic space and look back
 
+Toby A true. When you use a refrigerator magnet to pick up a paper clip, the magnet is exerting more force on the clip than the amount of gravitational force exerted by the entire Earth.

The gravitational force exerted by the mass of a human body is of course much smaller.
 
I showed this to the Invisible Pink Unicorn and she said, "My morning crap is bigger than that."  Affect, effect, forget that. You'll effect her if you put ham and pineapple on her pizza.
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