What am I observing?

[Strange]

Between the lights (stars and galaxies) you see black because there is no visible source of light there. Because our visible universe is finite.

 

You are not observing other "observable universes" becaluse they are not observable!

[JohnLesser]

Between the lights (stars and galaxies) you see black because there is no visible source of light there. Because our visible universe is finite.

 

You are not observing other "observable universes" becaluse they are not observable!

Thank you Strange for your reply, but they are only not observable only because ''we'' are not there in a geometrical position to observe it. If we was in another observable Universe it would be observable, if we was within the finite light boundary of another observable Universe we would observe it?

Edited March 22, 2017 by JohnLesser

[StringJunky]

I understood the observable Universe is spherical because of the isotropic nature of ''light''. I think you may of misunderstood my question.

 

 

In thought to my original question, what am I observing between the stars at night? I am possibly observing other observable Universes (light spheres) but can not see them because the light from them is too red-shifted.

 

Is this what you are saying to me?

To expand what Strange said on the OU. You are at the centre of the sphere and it moves with you, so, if you went 100LYRS out from Earth, your OU would extend 100LYRS futher than us on Earth but you wouldn't see as far behind you as us because your sphere has moved.

Edited March 22, 2017 by StringJunky

[JohnLesser]

To expand what Strange said on the OU. You are at the centre of the sphere and it moves with you, so, if you went 100LYRS out from Earth, your OU would extend 100LYRS futher than us on Earth but you wouldn't see as far behind you as us because your sphere has moved.

Thank you I can relate this to been like bubbles, if one bubble was to merge with another bubble then two observable Universes would be observed?

[StringJunky]

Thank you I can relate this to been like bubbles, if one bubble was to merge with another bubble then two observable Universes would be observed?

You can only see as far as your own bubble allows.

[JohnLesser]

You can only see as far as your own bubble allows.

Yes because of the inverse square law of light and light red-shifting beyond visible range. Does the relative size of a body have any affect over distance?

 

In other words, when an object travels away from an observer it visually contracts to an eventual point of ''nothing?

[StringJunky]

Yes because of the inverse square law of light and light red-shifting beyond visible range. Does the relative size of a body have any affect over distance?

 

In other words, when an object travels away from an observer it visually contracts to an eventual point of ''nothing?

No, I don't think it makes any difference, in theory, when we assume nothing is in the way to absorb the photons. A bigger light source can chuck out more photons but the effect will be the same on each photon, whether from a large source or smaller source

[JohnLesser]

No, I don't think it makes any difference, in theory, when we assume nothing is in the way to absorb the photons. A bigger light source can chuck out more photons but the effect will be the same on each photon, whether from a large source or smaller source

I would think it did make some difference, when an object moves away from an observer it scales down in visual size making a lesser dimension of light to observe?

[pzkpfw]

...

In other words, when an object travels away from an observer it visually contracts to an eventual point of ''nothing?

Just compare the (apparent) size/light/warmth of our own Sun, with the stars you'd see at night.

Edited March 22, 2017 by pzkpfw

[JohnLesser]

Just compare the (apparent) size/light/warmth of our own Sun, with the stars you'd see at night.

I was doing, I was considering that if the distance stars were to move further away and scale down in visual size further more, the eventuality would be total loss of observation because they have visually contracted to a 0 dimension?

[StringJunky]

I was doing, I was considering that if the distance stars were to move further away and scale down in visual size further more, the eventuality would be total loss of observation because they have visually contracted to a 0 dimension?

No, there will still be a 'line' of photons reaching you which can excite a sensor cell. When you see stars in the sky, that is not their apparent size, it is the size of one of your rods on your retina, which has been excited by a photon

[JohnLesser]

No, there will still be a 'line' of photons reaching you which can excite a sensor cell. When you see stars in the sky, that is not their apparent size, it is the size of one of your rods on your retina, which has been excited by a photon

No would contradict earlier replies in this thread. Are you suggesting that an object moving +V relative to an observer does not observably ''vanish'' when it reaches a boundary limit and loses its visual dimensions?

[StringJunky]

No would contradict earlier replies in this thread. Are you suggesting that an object moving +V relative to an observer does not observably ''vanish'' when it reaches a boundary limit and loses its visual dimensions?

It would vanish to us because of the limits our eyes but not to more sensitive instruments; photons will travel indefinitely in a vacuum.

[JohnLesser]

It would vanish to us because of the limits our eyes but not to more sensitive instruments; photons will travel indefinitely in a vacuum.

Indeed we can use instruments to magnify ''things''. Photons may travel indefinitely in a vacuum.

 

I may need to transfer this question to the Physics section.

 

If sight is the information contained in a Photon and according to you Photons travel indefinitely in a vacuum, then why can I not see a fly on a tree branch at distance when the fly is reflecting Photons the same as the tree?

 

Most certainly the flies relative to observer size is 0 dimension and past the boundary limit, if not how do we look at this information?

 

Added - If I am staring directly at the fly but cannot see the fly, but there is a stream of photons travelling from the fly to my eye, then why does my brain not create the ''picture '' of the fly?

Edited March 22, 2017 by JohnLesser

[Strange]

I was doing, I was considering that if the distance stars were to move further away and scale down in visual size further more, the eventuality would be total loss of observation because they have visually contracted to a 0 dimension?

 

 

If it weren't for the expanding universe, then while each star or galaxy at greater distance would provide less light but, at the same time, there would be more of them. So we would expect to see a uniformly bright sky: https://en.wikipedia.org/wiki/Olbers%27s_paradox

 

This paradox was not properly resolved until the expanding universe was discovered.

If sight is the information contained in a Photon and according to you Photons travel indefinitely in a vacuum, then why can I not see a fly on a tree branch at distance when the fly is reflecting Photons the same as the tree?

 

 

You could, if you used a large enough telescope (for the necessary resolution) and a long enough exposure (to gather enough photons to form the image).

[JohnLesser]

 

 

 

 

You could, if you used a large enough telescope (for the necessary resolution) and a long enough exposure (to gather enough photons to form the image).

That does not really answer the question and is seemingly evasive of the question. A single Photon suppose to contain the information from what I understand, so why can ''we'' not observe the fly but observe the branch of the tree? Photons are entering our eyes reflecting from the branch and the fly, so why does the Photon packet of information our brains receive of the fly not ''see'' the fly?

 

 

I would think it was because relatively the fly has 0 dimensions relative to the observer?

[Strange]

That does not really answer the question and is seemingly evasive of the question. A single Photon suppose to contain the information from what I understand, so why can ''we'' not observe the fly but observe the branch of the tree? Photons are entering our eyes reflecting from the branch and the fly, so why does the Photon packet of information our brains receive of the fly not ''see'' the fly?

 

 

Because the eye is not sensitive to single photons. You need to receive multiple photons in a short time (I have no idea what the numbers are) in order to form an image.

 

Some of the images of deep space, for example, require very long exposure times in order to accumulate enough photons to create an image.

OK. Just found this:

 

The human eye is very sensitive but can we see a single photon? The answer is that the sensors in the retina can respond to a single photon. However, neural filters only allow a signal to pass to the brain to trigger a conscious response when at least about five to nine arrive within less than 100 ms.

http://math.ucr.edu/home/baez/physics/Quantum/see_a_photon.html

 

To which I can only say: "wow".

[JohnLesser]

 

 

Because the eye is not sensitive to single photons. You need to receive multiple photons in a short time (I have no idea what the numbers are) in order to form an image.

 

Some of the images of deep space, for example, require very long exposure times in order to accumulate enough photons to create an image.

OK. Just found this:

 

http://math.ucr.edu/home/baez/physics/Quantum/see_a_photon.html

 

To which I can only say: "wow".

Thank you for the link, very interesting. How is several photons reflected from the fly not entering your eyes when there is a linearity between eye and fly? Is this a result of scattering following the inverse square law?

[StringJunky]

Thank you for the link, very interesting. How is several photons reflected from the fly not entering your eyes when there is a linearity between eye and fly? Is this a result of scattering following the inverse square law?

That experiment was done in the dark. In your fly example there will be much more noise from other photons coming in from elsewhere.

[Strange]

Thank you for the link, very interesting. How is several photons reflected from the fly not entering your eyes when there is a linearity between eye and fly? Is this a result of scattering following the inverse square law?

 

 

The number of photons does fall off rapidly, following the inverse-square law. Note that this is not due to scattering, just due to the fact that they are spread out over an increasing volume. However, scattering and absorption by the atmosphere will also reduce the amount of light. Finally, as StringJunky says, this will also be drowned out by other light in the environment (similar to how you cannot see stars during the day - they are still there but the sky is brighter).

[mistermack]

We get the same effect when trying to see the planets orbiting other stars. Even though we know that they're there, by the wobble in the star's position, or the regular dimming if the planet actually crosses the face of the star, we can't see them by the reflected light of the star.

They would be shining locally very brightly, just like Venus or Jupiter here in the solar system. But we can't see them, even with the most powerful telescopes ever built.

The light from the stars just drowns out the light from the planets. They are too close together, and the reflected light is too dim to make it to Earth in usable amounts.

[JohnLesser]

We get the same effect when trying to see the planets orbiting other stars. Even though we know that they're there, by the wobble in the star's position, or the regular dimming if the planet actually crosses the face of the star, we can't see them by the reflected light of the star.

They would be shining locally very brightly, just like Venus or Jupiter here in the solar system. But we can't see them, even with the most powerful telescopes ever built.

The light from the stars just drowns out the light from the planets. They are too close together, and the reflected light is too dim to make it to Earth in usable amounts.

Would this be anything like a black hole? meaning that we can't see it but the affects of gravity are still there.

 

 

The number of photons does fall off rapidly, following the inverse-square law. Note that this is not due to scattering, just due to the fact that they are spread out over an increasing volume. However, scattering and absorption by the atmosphere will also reduce the amount of light. Finally, as StringJunky says, this will also be drowned out by other light in the environment (similar to how you cannot see stars during the day - they are still there but the sky is brighter).

How do they, can they, spread out? I do not see ''gaps'' of darkness . If something spreads out, there is generally space between what is spreading?

 

Would the correct term be - The light stretches out ?

 

C travelling Y stretches out X ?

Edited March 23, 2017 by JohnLesser

[StringJunky]

How do they, can they, spread out? I do not see ''gaps'' of darkness . If something spreads out, there is generally space between what is spreading?

 

No, the intensity diminishes i.e. there are less photons per unit area as the distance increases.

[pzkpfw]

How do they, can they, spread out? I do not see ''gaps'' of darkness . If something spreads out, there is generally space between what is spreading?

In a way, the darkness is what's already there. If we see light (a thing) somewhere, that's because photons are reaching us from that thing.

 

The further we are from that thing, the more the light from it has spread out, so the dimmer (and smaller) it will appear.

 

Many of those stars you see at night are actually much much larger than our own sun. But they are so far away they are both visually smaller, and little energy reaches you - you won't be sunbathing at night, even though many many stars shine on you.

 

 

Imagine drawing a circle on a sheet of rubber. Let the ink represent (in 2D) the photons given out by a Sun at the centre of the circle, over some small time period. An ant placed near the line might think it's thick dark ink. Now stretch out that rubber sheet. As the circle expands (representing the photons all getting further and further from the centre of the circle) the line will appear less and less dark. That finite amount of ink is spreading out over a larger circumference.

 

(Please don't be misled by the rubber sheet mechanism used above. This is not about "stretching" the light; it's just showing how the light (the ink) is spread over larger and larger areas as distance increases.)

 

A Sun is continually spitting out more and more photons, but assuming a constant rate, you'll naturally be receiving less of those photons the further you are from that Sun.

 

 

You don't see "gaps" because there are still lots and lots of photons, being sent out in all directions. Again, 2D, if a Star were sending light out only North, South, East and West, then you might be in one of your "gaps" if you were standing North-West of the Star. But in reality, a Star is sending out light in all directions. The "spreading" of that light at far distances is more about how many photons you'd receive at a certain position, not about getting gaps between the photons.

Edited March 23, 2017 by pzkpfw

[JohnLesser]

In a way, the darkness is what's already there. If we see light (a thing) somewhere, that's because photons are reaching us from that thing.

 

What do you mean by in a way the darkness is whats already there?