Why do we see light from stars that are millions of light years away?

Originally posted by Astyanax
reply to post by AllIsOne

 

Great. Then here's another question. With so many stars in the universe, how come we see any dark patches at all? After all, the universe is thick with stars in every possible direction. We should be in the middle of a frying white-out, not darkness sprinkled with a few puny little lights. How come?

It's an old question, but it has an interesting answer.

Olbers' paradox. Proof that the Universe is not infinite in space and time. Forget fractal and red shift and tired light, the fact there is darkness at night is what led to the Big Bang theory as we know it today. 13.47 billion years ago there wasn't light, that is the gap between receding space that is not lit.

reply to post by Illustronic


Light is invisible until it hits something to illuminate or react with. You only see the starlight that hits your retinal sensory.

The rest of space is black because it doesn't interact with light. The reason our skies are blue during the day is because of our atmosphere reacting with the sun, and us seeing that.

If all starlight from billions of miles away would still have the intensity of the sun, we would be seeing clear blue skies all day long, and not a whiteout.

We see planets because of light reflection, theyre not luminous themselves.

reply to post by Romekje


If the universe is infinite with infinite stars then why doesn't it fill our entire field of view? What you said has nothing to do with light reflection or detection, what I said has everything to do with proving a finite universe, or does light just decides to quit traveling after 13.4 billion years and rest or detour?

reply to post by Illustronic


That wasnt the question,

The question was about light, not the infinity of the universe though i agree our universe is most likely finite.

Or not old enough for all light to have arrived yet

Or the older stars died already with others replacing them.

Look at the milky way horizontal plane from earth and you will see that a cluster of stars will indeed "white out" the sky, though still not enough to be more luminous then our sun.

reply to post by Romekje


It may appear to be full for a given spot but it isn't, there are gaps and that is why its not as bright as the sun. One can mathematically prove there are gaps. Take the relative distance, the relative arc microseconds a star at that distance would fill in the sky, and calculate out how many it would take to fill the arc second space of the sun and I'm sure there isn't enough stars to add up, then consider that calculation would be best case scenario with zero overlap and then you'll find an astronomical number. Its an illusion that view is full.

reply to post by Illustronic


i used the mily way as an example because it's the closest we can get into having an idea how the sky would look if we would see all stars in all directions.

Anyone who ever looked at the milky way can still distinguish seperate stars... just alot in 1 spot

Do i really need to become to the letter in every single post?

reply to post by Romekje


I was trying to analyze the original question/problem posed by Astyanax. I considered the question a challenge and mental exercise.

Of course you bring up valid and interesting points to the debate, but thinking infinite, one would have to wonder why the entire sky isn’t filled, regardless of how long the known universe has existed or beyond.

I was trying to imagine why nothing can be seen before our Big Bang, and conclude nothing was there to see. Maybe that kind of thinking is flawed, maybe Astyanax will return with his answer. From what I have observed, I suspect an answer is coming, which also could be an opinion.

Lets see.

I'm not a theoretical Astrophysicist.

At night I fight crime

I have my own theories about our "big bang" though im not sure this is the thread for it.

yet it seems this thread is more an "allround" discussion thing by now so ill just toss it out there.

We all know the phrase "as above, so below"

I think our universe is simply "offspring" of another universe. Not really having a big bang so to speak, but more a "permanent divide" from its mother universe.

If you look at cells dividing, there is always a critical point when the cells actually divides. Our universe itself is still expanding.

I think the multiverse grows as a human body... cell (universe) by cell.

hence we can't see past 20m LY, maybe thats the outer limit before division.

ETA: im no scientist either, i just like to think, and thinking instead of regurgitating pushes us all forward! So for all i care you keep pounding me with mind twisting questions

reply to post by Illustronic


The pixels on your monitor have gaps between them too, just not observablle by the human eye because they're too small.

What we see is nothing more but a pixelised version of reality (and tbh, our eyes resolution aint the best if you think of it, 640x480 seems seemless already)

reply to post by AllIsOne


It's an Illusion!

Just like the rest of this Matrix.

reply to post by Romekje


1080p doesn't fill my monitor. Doesn't even reach the width let alone the height.

The sun not only has spherical overlap, it is also very close to us comparatively. A 'white out' of distant stars simply could not be as 'bright' as the sun. So enough of that.

Peace brother.

reply to post by Illustronic

How many megapixels equivalent does the eye have? The eye is not a single frame snapshot camera. It is more like a video stream. The eye moves rapidly in small angular amounts and continually updates the image in one's brain to "paint" the detail. We also have two eyes, and our brains combine the signals to increase the resolution further. We also typically move our eyes around the scene to gather more information. Because of these factors, the eye plus brain assembles a higher resolution image than possible with the number of photoreceptors in the retina. So the megapixel equivalent numbers below refer to the spatial detail in an image that would be required to show what the human eye could see when you view a scene. Based on the above data for the resolution of the human eye, let's try a "small" example first. Consider a view in front of you that is 90 degrees by 90 degrees, like looking through an open window at a scene. The number of pixels would be 90 degrees * 60 arc-minutes/degree * 1/0.3 * 90 * 60 * 1/0.3 = 324,000,000 pixels (324 megapixels). At any one moment, you actually do not perceive that many pixels, but your eye moves around the scene to see all the detail you want. But the human eye really sees a larger field of view, close to 180 degrees. Let's be conservative and use 120 degrees for the field of view. Then we would see 120 * 120 * 60 * 60 / (0.3 * 0.3) = 576 megapixels. The full angle of human vision would require even more megapixels. This kind of image detail requires A large format camera to record.

clarkvision.com...

Lets get technical then

We see pixels, even our eyes.

reply to post by Romekje


We see analog, (like film), that effctive resolution is referred to as film grain (purity of film manufacturing technology and the size of the silver particles) finitely smaller than megapixels (in digital CCDs). A simple 35 mm film negative has the effective 'digital pixel resolution' of something like 2,400, but the negatives are small. They took to the moon medium format Hasselblad 70mm film. I get art photographed for reproduction with large format Hasselblad 8 X10 inch film of originals that are too large to fit on a digital scanner. The pixelation degrades every regeneration from original/film/photo/scan/print, analog=sight, the pixels they speak of are spaces, not pixels.

Early 1900's 8X10 inch glass plates with silver was used for clarity of imaging still rivaling the best in Photography today digital or analog. They were very fragile, and required great care to process a print, dependent on the print paper grain, usually not as smooth as glass.

One is on a slippery slope when one tries to compare digital to analog, in either sight or sound. I think it is syntax simplification for comprehension that pixel is even used in that description of imaging of our visual preceptors, and not actual. Think about birds seeing mice from 2,000 feet.

Originally posted by stealthmonkey
its because your sight is faster than light i thought everyone knew that if you covered the sun up and instantly uncovered it it wouldnt take 7 minutes to see it how ever it may take 7 minutes to feel it

That makes no sense at all...

If you could, somehow, drop a huge blanket over the sun then remove it a second later, the no one would know anything about it on Earth until just over 8 minutes later, when it would go dark and a bit chilly for a second.

Visible light and what we perceive as heat are one and the same, just different wavelengths. I have no idea why you think the two are different or why you would see the sun blink out instantly but not "feel" it until some time later.

Originally posted by Glassbender777
Whats is truly amazing is that when we look at distant stars, we are looking back in time. At Light that was emmited from a star, millions of years ago, of course this depends on what star you are looking at, it could be less or more. For all we know, most of the distant stars could all be very different now, some gone in a Super Nova, some turned into Red Giants, and new ones being born changing the sky we adour forever.

Ahh....one of my pleasure to ponder as I star gaze....that we are truly looking back in time


I often wonder if Beetleguese has gone super nova yet

reply to post by Illustronic

Yes, the question is known as Olbers' Paradox. However, your answer is wrong, Illustronic, as is Romekje's counter-argument.

Anyone else care to have a go?

reply to post by Astyanax


Since you are making a statement, could you provide us with proof, proving us both wrong?

Seems ur "in the know"...?

Enlighten us pls.

reply to post by Romekje

That would spoil the fun. If you aren't up to it, let someone else have a go.

By the way, Illustronic,

I was trying to imagine why nothing can be seen before our Big Bang, and conclude nothing was there to see. Maybe that kind of thinking is flawed, maybe Astyanax will return with his answer. From what I have observed, I suspect an answer is coming, which also could be an opinion.

All of the above is correct. The reason why the finiteness of the universe is not a factor is because we do not actually see the whole universe. We only see a part of it, so it is not really of importance whether or not it is finite.

Originally posted by Astyanax
reply to post by Illustronic

 

Yes, the question is known as Olbers' Paradox. However, your answer is wrong, Illustronic, as is Romekje's counter-argument.

Anyone else care to have a go?

I'll have a go. Olber's Paradox basically states that if the universe was infinite (in age and extent), the sky should be bathed in starlight. Since it is not, then the universe must be finite. The Big Bang theory describes a universe that is finite in age, which would seem to solve Olber's Paradox. The problem there is that the very early universe as described by the Big Bang theory was extremely luminous (since all the matter in the universe was condensed into a very hot, bright space). And since looking deeper into space is like looking back in time, it would seem that even with the Big Bang, the sky should be bathed in the early light of the universe.

The solution to that problem is the expansion of space. The light from the very early universe has been stretched out over time, like a focused spotlight being turned into a wide floodlight, decreasing in intensity. What we're left with is the cosmic background radiation, a very faint glow in the microwave part of the spectrum.

So in a sense, the sky is bathed in the light of the early universe. It's just been stretched out and "diluted" as the universe has expanded for the last 14 billion years.

Originally posted by Astyanax
reply to post by Romekje

 

The reason why the finiteness of the universe is not a factor is because we do not actually see the whole universe. We only see a part of it, so it is not really of importance whether or not it is finite.

If the Universe is infinite then what is the reason light cannot reach us beyond ~14 billion light years, it would have the time originating from before then. Which is why I reject dispersion also.

I rejected fractal distribution creating gaps (the Mandelbrot set cannot reach zero), red shift to obscurity, and tired light.

I suggest that a finite Universe, answers the inadequacy of enough sources to obliterate dark.

So bare with me while I type as I run through my logic progression.



OK, lets dissect the ways observation a light source can vanish, there are many so I’ll focus on the obvious.

The stream of photons emitted from a source has ceased to exist, ended, concluded transmission.

The stream of photons emitted from a source has moved.

The stream of photons emitted from a source has not reached us yet, (why would that be if time is infinite?).

Dispersion rejected above.

The source of emitted photon stream and the detection source (us) are receding from each other at a speed greater than c combined, at that point photons emitted never reach us, OR, the space between the source and detection combined with the relative proximity of source-detection exceeds c.

The stream of photons emitted from a source has been absorbed by the amount of ‘stuff’ between the source and detection points, or deflected away, from reaching us, (I reject).

The stream of photons emitted from a source reaches a point that the amount that gets through deflection/absorption of 'stuff' between is too sparse to be differentiated from the CMB, thus invisible to our detection. (Hmm)

Would that mean; red shift ultimate regression is black, and blue shift ultimate progression is black? (I initially rejected).

If we assume the distance a photon can traverse is independent of energy loss then a photon has no limit to how far it can traverse through space/time. If we assume that energy is lost by gravitational forces, radiation energy transfer, or transfer to particle, we now have a finite distance a photon can traverse. If so, we can define a universal average attenuation length.

Leaving that discussion to mathematicians, layman logic can suggest the paradox is, for enough sources of emitted photons to traverse through and fill all the gaps ultimately accumulates to a level of energy approaching singularity, where light cannot escape. A ridiculous notion in expanding space, but infinity suggests there would be enough sources to obliterate the very conditions that light can exist in, an self inflicted progression to the ultimate black body.

Singularity is the fictitious state our language cannot describe, where our science breaks down. We can only describe approaching a singularity, and before singularity can be achieved the compression does not allow light to escape.

So the short answer is space expansion acceleration exceeds c, so in time less sources are able to catch up to us that once could.