bobbo, I think I'm correct says:

Bubba, the question asked is “What does dark mean.”

Arc, arc, arc. (Hands Clapping In front.)

pecker says:

# 21 bobbo,
By “dark” I think they mean an area of the sky where no light is observable above the noise on previously taken images.
It’s not possible to take measurements (of light or anything else) without there being some noise or inaccuracy, so I can’t see that you would ever know if something is completely dark or not. The best you would be able to say is “this is dark within my ability to measure darkness”.

I’m pretty sure there is real darkness out there though – even though quatum theory says we can’t measure it absolutely.
I read somewhere that the Universe has a finite number of stars. If there was an infinite number of stars you would ultimately end at the surface of a star in every direction you pointed in the sky – the night sky would appear completely white! The real night sky appears mostly black, so there must be a finite number of stars and gaps between them.

ECA says:

Interesting..
and the idea of DARK matter being everywhere??

Has anyone taken a pic in a Scattered fog?
The farther you VIEW, the more fog you get..
After a point you cant get past all the fog to view PAST..
So, what happened to all the Dark matter?
To see a pic This bright had to be augmented.
What are the odds that they used IR, and saw specks of light and inserted the galaxies THEY THINK were there??

Hugh Ripper says:

But…but…but… all this stuff is only 4 thousand years old. Would Jesus lie to you?

joaoPT says:

As we found a lot of (100s of billions..) of light matter on a place we considered devoid of matter… and that’s what probably happens all around us, and we can’t see it because there’s a brighter object nearer…Do we still need the existence of dark matter??? The Higgs Boson?
And, by the way:
#9
“@Mark Derail

I don’t think there is nearly enough density in those bodies for that to work. You need something seriously massive (like a black hole) to do gravitational lensing.
”

That’s what the collider is for… and they’re turning it ON again… run for your lives…

bobbo, not a mathmetician or theorists says:

#24–rethinking myself/pecker===”I do like the notion of every direction ending on a star. I don’t think that would define an infinite number. /// If every direction is every “point” and there are an infinite number of points along any line/surface, then YES, there would be an infinite number of planets==rethinking X2==but each star consumes many trillions or even an infinite number of points itself–”so” the notion of star and point is inconsistent.

I think that is correct, but who can understand infinity anyway?

pecker says:

# 24 bobbo “interesting definition of dark. Are you sure you are not anthropomorphizing the universe just a little bit?”

I’m not sure where I might be accused of anthropomorphizing. The only thing I can imagine is where I said ‘there is real darkness out there’. I wasn’t consciously hinting at any human darkness – just trying to say something like ‘there are patches of sky from which absolutely no light is coming’.

““Dark” as defined by what humans can see or including what moths can “see” in the infra red?”

If a photon or a radio wave is just the transfer of energy between two particles, the same definition of ‘dark’ could apply to infrared light or any other wavelength that we can’t see directly with our eyes.
A patch of sky that looks dark to us would also appear dark to a moth because there are no particles there.

“I do like the notion of every direction ending on a star.”

If that was the case, every bit of the night sky would appear bright white as you would be looking directly at the surface of a star.

“I don’t think that would define an infinite number.”

I was just trying to make the case for there being darkness and that there must be a finite number of stars. But you are right, if you wanted a white-hot night sky you could have either:
- a finite number of stars packed tightly into a finite universe,
- a finite lump of stars floating in an infinite universe, or
- an infinite number of stars in either a finite or infinite universe.

“But, if the universe isn’t infinite, whats on the other side?”

Personally I favor the idea that the universe is finite and, on large scales, space is looped around – if you travel in one direction for long enough you end up back where you started. Similar to not falling off the edge of what looks like a flat world because it is actually spherical, when seen at larger scales.
From that perspective there is no way of getting to an edge; no edge or ‘other side’ exists.

bb says:

#31
Consider the infinity of all positive integers compared to the infinity of both positive and negative integers. Then, compare that with the infinity of all rational numbers between 0 and 1 … or the even ‘bigger’ infinity of all irrational numbers between 0 and 1.

Mathematically, all these infinities are the *same*! There is no such thing as a bigger infinity compared to another infinity.

But I have a terrible time trying to wrap my mind around that – the same thing happens when I study quantum physics. God *does* play dice with the universe!

pecker says:

# 35 bobbo,
“Ok, so when the universe is said to “be expanding” what is it expanding into?”

Hmm, that’s a tough one. I haven’t thought about that for some time. If I was to put money on it, I’d say the universe was expanding into something unknowable.

It is possible that there are limits to what is discoverable about the universe. In fact, the universe may even be setup so it’s impossible for us to even prove that there are limits on what we can know about it’s underlying workings. If that is the case, from our perspective within it, there would be no physical way of finding out what is ‘outside’ of the universe.

Our brains, the dimesions we see and even physical relationships like ‘inside’ and ‘outside’ are properties of the universe we are within. Even if there weren’t limits on what we could find out about this universe, how could we infer anything about another ‘adjacent’ universe if our concepts like ‘adjacent’ and ‘next-to’ can only be applied to this universe.

I guess you could say this is defeatist, but I tell myself it’s practical and simplifies things – allows me to sleep easy beleiving it’s not my fault I don’t know what’s going on.

As for the infinite number of stars thing. I read the argument in a book discussing big-bang vs steady-state theories years ago. I will see if I can find exactly how it went…

pecker says:

bobbo, I found it, it’s called Olbers Paradox