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New measurements of the sky's blackness

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11–20 of 67 posts

Re: New measurements of the sky's blackness

#11
post #2

There are far fewer *Visible stars and galaxies than we thought

This is more about the invisible stars and galaxies, the ones too far to actually count, but whose lights just gives a faint glow to the darkness.

This depends on your definition of visible. If you think of visible as some form of light reaching a man-made object, then GPs statement is still true.

Re: New measurements of the sky's blackness

#12
post #9

Noob physics question: I assume this talks about stars close enough that we can receive their light. Can we say anything about the number of stars & galaxies that are further away than that?

Good observation... just made another comment about that. You’re asking about the observable universe vs the universe, and it’s an open question.

Might be drastically more, or even less.

https://en.m.wikipedia.org/wiki/Observable_universe

Re: New measurements of the sky's blackness

#15
post #9

Noob physics question: I assume this talks about stars close enough that we can receive their light. Can we say anything about the number of stars & galaxies that are further away than that?

My understanding is that there isn’t much point theorizing about the “outside” universe beyond the horizon of our light cone, because there is no present or future interaction possible between it and us.

Re: New measurements of the sky's blackness

#16

Um. What? Is this the new "the earth is flat"? Space is infinite. I believe it goes on forever in every direction. Whether you can see whatever is out there from here in no way proves that it isn't...

That’s not known. This article refers to the observable universe which is bound by the speed of light.

Whether the universe is infinite or not is an open question. It might be finite but unbounded. Spacetime geometry is complicated.

Re: New measurements of the sky's blackness

#17

Um. What? Is this the new "the earth is flat"? Space is infinite. I believe it goes on forever in every direction. Whether you can see whatever is out there from here in no way proves that it isn't...

We have no proof Universe is infinite, but we can also argue that the building blocks of Universe - atoms? - cannot come in unlimited quantity. At least it sounds more reasonable that way. Unless of course we are all in a symultation and our whole Universe takes up half a sq. inch of a silicone chip.

Re: New measurements of the sky's blackness

#18
post #9

Noob physics question: I assume this talks about stars close enough that we can receive their light. Can we say anything about the number of stars & galaxies that are further away than that?

My main response to this article is essentially the same question. I think the article is presuming some things to come to this conclusion.

The main thing that is being presumed is the "big bang". If you proscribe to believing in the big bang, then the entirety of everything we see is an expansion from a single dense explosion of matter.

It is still a valid theory but I myself don't understand the physics of what is observed well enough to be convinced this is true. I believe that they are seeing something similar enough that it could be perhaps a "localized bang" or something like that.

The main evidence used as "proof" of the big bang is the observed data seeming to show that the everything in the universe is "dispersing" slowly. That is at least what I've heard claimed.

Re: New measurements of the sky's blackness

#19
post #9

Noob physics question: I assume this talks about stars close enough that we can receive their light. Can we say anything about the number of stars & galaxies that are further away than that?

My understanding is that there isn’t much point theorizing about the “outside” universe beyond the horizon of our light cone, because there is no present or future interaction possible between it and us.

There’s good reason to theorize about it. Theories might be able to point to or estimate the size even if we can’t directly measure it. For instance if we find evidence of inflation in more fundamental physical processes, we can assume there’s more universe out there than we can see.
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