Serious question about light (particle/wave)

Originally posted by alfa1

Originally posted by UnixFE
Blinking as there is a short timeframe without light/photon reaching the detector.

Yes, as I understand it, if a star is faint enough, you could measure the average photon rate at less than one per second (as an example).

That's the same as staring out into the night, focusing as deep as you can, to barely see that one spec of light that seems to elude you if you move your eyes just a hair. You see it there a second, then it's gone or faded out, then you see it again for another brief moment, as though you were straining to see the objects light.

I noticed this when I was looking Neptune one night, just to see if I could catch it with the naked eye. What I "thought" I saw was the tiniest pinpoint of faded, very faded blue light that seem to appear and dissapear in fractions of seconds, constantly. Im not sure if this is the same, but it "seems" to have the same properties as what you are asking, in relation to the "blinking".

Hmm makes one wonder, just how many particles are hitting your eye as you stare out into a pitch black sky and a beautiful full blanket of stars.

I know exactly what you are asking as I have thought this myself many times. It is just hard to formulate the question.

No matter how far away a star is (with reason, close enough to be seen with the naked eye) How does that star send out enough photons to be seen from every angle for billions of lights years?

And I think you already answered your question. The photons expand from the star as a waves and it is only once this wave is observed does it snap into its "particle" form. This would allow for us to see "particles" from every angle.
Otherwise a star would have to be emitting an infinite amount of particles from any particular spot to be see from any particular angle at any particular distance!

reply to post by UnixFE

If it expands like a sphere like for example the radio wave is it possible to drain this energy so some extraterestial a few planets behind me won't see any light just like it's possible with radio waves?

Yes. It is called shadows.

It looks like you see the stars as sending one photon at a time which will collapse somewhere. In fact stars send billions of photons at once. Some will collapse on my eye and some on yours.

I write so much, that I rarely post anything. Although I love ATS and feed its RSS to my own site, Einsteins and Idiots.
However, I was compelled to reply for this topic.

Particle or Wave. I am no physicist by any stretch of the imagination but I do love the topic.
Quantum Mechanics, String Theory etc. intrigue me.
I believe the current theory regarding this, which is almost the same, as one of the other posters above. It is in fact, I believe both.
I do not however agree that it is a group of particles acting as a wave. I believe it is a wave until observed and thereby causing the change to particle.

Quantum Theory states that nothing "is" until it is changed by the observer. The mere act of observing, is measuring.

Great Post and Great Topic

reply to post by UnixFE


Your looking at things in a different context, consider the uncertainty principle. The photon can both exist and not exist at the same time. Its up to the observer by just observing to determine which state the photon is in.

I think the answer u looking for is something like this. Photons are balls of pure energy travelling at the speed of light. Now a photon has no mass and therefore dosent slow down overtime allowing it to remain at the speeed of light. Now a photon exists till its gets aborbed by something and in space there is very little to get in the way of photons so they carry on travelling till they hit something. The further away the star is less light is seen because the light is spread over a larger distance.

The wave part is easy to see if you think of space as water and a photon as a ice cube. When the ice cube moves it leaves a wake which is waves rippling across the water. So when we see a wave in quantum it is showing its passage through the spacetime fabric.

Originally posted by TheMindWar
reply to post by UnixFE

 

Your looking at things in a different context, consider the uncertainty principle. The photon can both exist and not exist at the same time. Its up to the observer by just observing to determine which state the photon is in.

Yep... my understanding of it is similar.

Superposition - (Quantum Mechanics) Holds that a physical system (say, a photon) exists in all its particular, theoretically possible states (or, configuration of its properties) simultaneously; but, when measured, it gives a result corresponding to only one of the *possible* configurations. Source: Wikipedia

reply to post by Blarneystoner


Indeed, mind you, I like my explanation better

Originally posted by TheMindWar
reply to post by Blarneystoner

 

Indeed, mind you, I like my explanation better

I only take exception to the part about existing or not existing at the same time. Photons when un-observed act as a wavefrom but when observed act as a particle....

Thanks a lot for helping me understand this. As I have to go to work in 7h it's really time for me to get some sleep now. Quantum mechanics is really a great topic. As already written in the OP I've read a lot about it including several other topics like holographic universe. So the particle/wave dualism is nothing new to me.

reply to post by Blarneystoner


If you dont observe a particle then you will not see any results so you wont know if its in a wave or a particle state.

Photons observed through an interference experiment act as waves.

Originally posted by Arbitrageur

Originally posted by UnixFE
I just refered to my eyes as it was easier to describe than a detector in a lab. So this would mean stars do indeed blink if you just look close enough? Blinking as there is a short timeframe without light/photon reaching the detector.

I'm not sure how technical you want to get with the answer to your question.

When the star is very dim, there's another problem besides the number of photons being emitted, which is atmospheric distortion. This might actually cause the star to start blinking out visually even if a sufficient number of photons are headed in your direction. You can see this effect on brighter stars too, we call it "twinkling" which is a cute name but it's a big problem for astronomers viewing through the atmosphere, though they have fancy technology to compensate for it partially, it's something the Hubble doesn't have to deal with.

If you set twinkling aside though and just focus on the number of photons, this physicist has written more detail about the subject than you could ask for:

Ten photons per hour

the number of photons from the galaxy seen with the unaided eye is more like two hundred per hour, and in the telescope it is of about 350 per second

Now let's take the naked eye rate of two hundred photons per hour coming from the galaxy.

I am not sure how many stars are in that galaxy but we think ours has 400 billion or so, so let's say that's a smaller galaxy with 100 billion stars.

take 200 photons per hour, multiply that by 24 to get per day and by 365 to get per year = 1,752,000 photons per year.

divide that by 100 billion stars, and you get the photon rate coming from each star, which is 0.00000876 photons per year per star, or in other words, the typical time period between photons hitting your eye from each one of those stars is about 114,000 years.

Edit to add: I think that calculation, in addition to answering your question, also solves Olber's paradox, don't you? That doesn't seem like any paradox to me.

edit on 29-11-2011 by Arbitrageur because: clarification

The only problem with your summation is that you only calculated using the amount of photons hitting the eye at 200 per hour. That doesn't mean that the total amount of photons coming from the galaxy is only 200 per hour, that's the amount that your eye can take in. Notice that the rate per hour changes for telescopes.

So, after taking care of some other (more legitimate) approximations, if one computes things correctly, the number of photons from the galaxy seen with the unaided eye is more like two hundred per hour, and in the telescope it is of about 350 per second.

But that's a bit decieving. If you looked directly at the sun (don't do it) your eyes would be taking in about 100 trillion photons per hour....

and the surface of the eye is only about 20 square millimeters..

Originally posted by TheMindWar
reply to post by Blarneystoner

 

If you dont observe a particle then you will not see any results so you wont know if its in a wave or a particle state.

Photons observed through an interference experiment act as waves.

No... you get results regardless of whether the electrons are observed or not, but the results of an interference experiment change when the electrons are measured (observed).

Originally posted by Blarneystoner
The only problem with your summation is that you only calculated using the amount of photons hitting the eye at 200 per hour. That doesn't mean that the total amount of photons coming from the galaxy is only 200 per hour, that's the amount that your eye can take in. Notice that the rate per hour changes for telescopes.

That was intentional, why is that a problem?

The OP asked about what he could see with his eye so that's what I used.

If he had asked what he could see with a telescope I would have used that.

reply to post by Arbitrageur


I'm pretty sure that the guy that likes to do physics calculations in is head while walking to work has it wrong. I don't claim to know that stuff but common sense tells me that the amount of photons hitting my eye from a distant star is more like several hundred per second not 200 per hour. That's just silly.

Originally posted by UnixFE
I have a question about light and/or maybe quantum physics in general. I am no newbie in quantum physics and read many books about it (some from Richard Feynman) but while falling asleep I thought about light and can't solve the problem.

As far as we know a star (and our sun of cause) has some fusion going on releasing photons we see as light. Thats not hard to understand but what I thought about is: This photon has to fly in my direction (if it is a particle) and hit a cell in my eye so I can see the light from this star. If you take into account the distance of a star ( several light years) is it really possible that this star genertes photons that reach every part of the virtual sphere around it in my distance to it so that every millisecond there is a photon that can hit my eye? I haven't calculated this but a sphere with a radius of several lightyears should have a huge surface. Than dividing this surface into small pieces (to the size of my eye or better ever the cells in my eye). Of cause there would be billions of photons generated but really enough for each part and every millisecond in each area of this surface?

So as stars don't blink (they do but I asume this is just a visual effect through our atmosphere as I have learned) is this a prove for the wave nature of light. So each photon that is generted in that fusion expands into space like an expanding ball until it gets into contact something like my eye to be perceived like a photon/light?
And if this is the case just when do this wave deceide to collapse? I bet that my eye is not the first thing in range so if each of these photon waves expands into space why don't they all collapse in the same place while 'hitting' the first object with the outer surface? And if this wave just expands into a single direction we have the same problem as with a particle.

Is there a possibility that at a given time there is no photon send into my exact direction and the star is not visible for a moment. What if the star is millions of light years away? Would it be possible to see that such a star is blinking as there aren't enough photons for each part of the universe at such a distance?

I hope you understand what I mean as english is not my native langueage and there are probably many mistakes in the text.

edit on 29-11-2011 by UnixFE because: (no reason given)

edit on 29-11-2011 by UnixFE because: (no reason given)

The star doesn't really exist, all that exists is your perception of it.

By freeing your mind, you free your enslavement to arbitrary ideas of "esxistence" and "non-existence."

Originally posted by Blarneystoner

common sense tells me that the amount of photons hitting my eye from a distant star is more like several hundred per second not 200 per hour. That's just silly.

Your common sense would seem to be wrong, in this instance. Why would it be more reasonable that photons from a single distant star be that much more than 200 per hour? Have you ever seen a star from a distant galaxy with your naked eye?

ETA: the threshold of human eye sensitivity, ignoring the affects of scattering and background light, is about 7 photons in 100 ms:

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.

Source.

That's 70 photons per second, or 252000 per hour - quite a bit more than 200 per hour.

Originally posted by CLPrime

Originally posted by Blarneystoner

common sense tells me that the amount of photons hitting my eye from a distant star is more like several hundred per second not 200 per hour. That's just silly.

Your common sense would seem to be wrong, in this instance. Why would it be more reasonable that photons from a single distant star be that much more than 200 per hour? Have you ever seen a star from a distant galaxy with your naked eye?

ETA: the threshold of human eye sensitivity, ignoring the affects of scattering and background light, is about 7 photons in 100 ms:

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.

Source.

That's 70 photons per second, or 252000 per hour - quite a bit more than 200 per hour.

edit on 29-11-2011 by CLPrime because: (no reason given)

How am I wrong? I was disputing this statement:

So, after taking care of some other (more legitimate) approximations, if one computes things correctly, the number of photons from the galaxy seen with the unaided eye is more like two hundred per hour, and in the telescope it is of about 350 per second.

The number of photons from a single magnitude 6 star (still visible to unaided eye) entering a 7mm (approx size of pupil) aperture is probably more like several hundred photons per second. That's all I'm saying. The total number of photons hitting my eye from the galaxy has to be many times more.

The number of photons your neural network can process is a different subject.

Originally posted by Blarneystoner

a single magnitude 6 star (still visible to unaided eye)

That would be the difference. You're talking about a visible star, while the 200-photon-per-hour calculation is in reference to a star in a distant galaxy. The nearest galaxy to us is the Canis Major Dwarf Galaxy, which contains red giants having a typical magnitude of about 13. Even these are in no way visible to the naked eye.

reply to post by CLPrime

You're right again.

dorigo.wordpress.com...
The galaxy he referred to was "MGC 10-17-5, is actually a faint galaxy in the field of view of NGC3690. It has a visual magnitude of +15.7: this is a measure of its integrated luminosity as seen from the Earth". He said it was barely within the range of visibility with his 16" Dobsonian telescope.

He also admits he made some calculation errors in his head while walking to work, but the 200 photons per hour was the corrected number he came up with after sitting down and doing the calculations more accurately.

Also I was trying to respond to this post by the OP:

Originally posted by UnixFE
reply to post by tangonine

 

Thanks for the link to Olbs paradox. Can't remember that I read about this. It's not exactly what I mean but into the same direction. I would like to know kind of the opposite. Why is there light from distant stars at any given timeframe. Of cause a star produces billions photons a second but is thos really enough for any possible observer millions of lightyears away.

Where he asked for something like the opposite of Olber's paradox.

I thought stars so dim that photons from each star reached the eye only once every 100,000 years or so was a pretty good illustration of the opposite. It's only when you add up the light from billions of stars in the galaxy, that you get the 200 photons per hour.

And since he mentioned millions of light years away, you're pretty much talking about stars in other galaxies at that distance.