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| A question about time and light |
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| inite |
 Posted: Thu Feb 18, 2010 3:29 pm Post subject: A question about time and light |
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Im not quite sure if this question belongs in this section, but will place it here for lack of a better place.
In photography, light is focused through a lens, slows down, bends, and is recorded on film to create an image of the past.
Is this process possible because the light that was captured is gone, and since the moment that it was recorded we have traveled from that point in space? So, if we were to completely stop our movement in space, (our galaxy and the universe as well) would light continue to record time, and our eyes, like film, see the future?
Of course this is not possible, I am just trying to understand our preception of time and its relation to light. We are able to revel in the past through manipulations of light like radio, TV, and such but is time set or fine tuned to the speed of light? Also, interesting is the function of Melatonin, our internal time keeper governed by light, responsible for a variety of functions in many different organisms, which also gives us a since of jet-lag when we travel in time.
This is a very incomplete thought and highly irrational I know, but I am just curious. Hope you have the time to answer this question or could shed some light on the subject. Thanks. |
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| inow |
| Posted: Thu Feb 18, 2010 8:15 pm Post subject: Re: A question about time and light |
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| inite wrote: |
| In photography, light is focused through a lens, slows down, bends, and is recorded on film |
Light never slows down. Light never speeds up. Light travels at one speed. It travels at c.
Now, there are times when the apparent speed of light slows down, but the photons themselves travel at a constant c. What you are referring to (I think) is when light gets absorbed and re-emitted by some substance or material... it appears to us perceptually to have slowed down... However, most assuredly, it has remained at a constant speed.
| inite wrote: |
| Is this process possible because the light that was captured is gone, and since the moment that it was recorded we have traveled from that point in space? |
I'm not sure about the second half, but the light is not "gone." It has simply changed forms. It has transferred its energy on to a photoreceptor or a chemical film and led to a cascade of other effects, but it is not gone. It has changed forms.
| inite wrote: |
| So, if we were to completely stop our movement in space, (our galaxy and the universe as well) would light continue to record time, |
If all movement stopped, then there would be no such thing as time. The stopping of all movement in the entire universe is equivalent to frozen time, so there is nothing to record. Now, there are other issues here such as the fact that there is no such thing as absolute time or absolute space, so the concept of stopping it all is somewhat flawed. You have to realize that when you attempt to describe systems which are not possible then it is also not possible to use existing physics to describe those systems. Physics only applies to things which might actually exist or be possible in nature.
| inite wrote: |
| and our eyes, like film, see the future? |
Like I said, the only way to freeze everything is to stop time, so the concept of "future" becomes meaningless.
| inite wrote: |
| Of course this is not possible, I am just trying to understand our preception of time and its relation to light. |
I don't understand.
| inite wrote: |
| We are able to revel in the past through manipulations of light like radio, TV, and such but is time set or fine tuned to the speed of light? |
I don't understand. We don't see the past. We see light reaching us that took time to travel, so we are experiencing seeing that object as it appeared in the past.
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iNow
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~~ Pale Blue Dot ~~
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"[Time] is one of those concepts that is profoundly resistant to a simple definition."
~C. Sagan |
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| icewendigo |
| Posted: Fri Feb 19, 2010 1:14 pm Post subject: |
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| about speeed of light being constant, what happens to light inside a black hole? Does it head to the center? once in the center does it still move at the same speed? |
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| inow |
| Posted: Fri Feb 19, 2010 1:31 pm Post subject: |
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| icewendigo wrote: |
| about speeed of light being constant, what happens to light inside a black hole? Does it head to the center? once in the center does it still move at the same speed? |
Unknown. Our current models result in singularities when we reach the center of a BH, so we cannot say with any confidence what happens after a given point. We need some new equations and math that is able to incorporate both relativity and QM (akin to quantum gravity) to better address your question.
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iNow
~~~~~~~~~~~~~~
~~ Pale Blue Dot ~~
~~~~~~~~~~~~~~
"[Time] is one of those concepts that is profoundly resistant to a simple definition."
~C. Sagan |
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| Dishmaster |
| Posted: Sat Feb 20, 2010 12:28 am Post subject: |
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| It is possible that light will be absorbed by the most certainly ionised matter. |
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| LeavingQuietly |
| Posted: Tue Feb 23, 2010 12:26 pm Post subject: |
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| icewendigo wrote: |
| about speeed of light being constant, what happens to light inside a black hole? Does it head to the center? once in the center does it still move at the same speed? |
Time stands still in the black hole, hence it has evaporated before anything moved in it, seen from the inside. Questions? Answers?
_________________
Here I will explain the flaw in SR.
Einstein say x1 = +x, x2 = +y, x3 = +z, x4 = ict
I say 2 dimensions can't have the same sign.
And that time has one direction is positive
x,y & z has imaginary sign compared to eachother else they wouldn't been arbitrary +/- directional.
ctt + ivtx + √(-i)vty + √-(√(-i))vtz = distance |
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| 6nqpnw |
| Posted: Tue Mar 02, 2010 9:45 am Post subject: |
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Does anyone else agree that the relationship between time and light is often confused? Isn't light used simply as a reference point for time (being that light is constant and not dynamic / variable / changing)?
Without know better how to articulate time and light, but if you travel faster than light, you're just moving faster than an image (light reflected off of matter), having NO effect on the matter itself.
- mudbug
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"To know nothing is to know everything." - Confucius
"Imagination is E..." - Einstein
Last edited by 6nqpnw on Wed Mar 03, 2010 10:23 am; edited 1 time in total |
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| Dishmaster |
| Posted: Tue Mar 02, 2010 12:40 pm Post subject: |
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| 6nqpnw wrote: |
Does anyone else agree that the relationship between time and light is often confused? Isn't light used simply as a reference point for time (being that light is constant and not dynamic / variable / changing)?
Without know better how to articulate time and light, but if you travel faster than light, you're just moving faster than an image (light reflected off of matter), having NO effect on the matter itself.
- mudbud |
You are correct in the sense that the speed of light is independent of any reference frame. This is the constant in the relations between space and time. Remember, you cannot separate space and time, because besides time dilation there is also length contraction. And these entities do depend on reference frames - the speed of light does not. |
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| 6nqpnw |
| Posted: Wed Mar 03, 2010 7:57 pm Post subject: |
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approaching near speed of light = decreased matter decay (time dilation) + decreased length (length contraction) + increased mass (mass increase  )
This is all too much for me in one day. Gonna sleep on it.
- mudbug
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"To know nothing is to know everything." - Confucius
"Imagination is E..." - Einstein |
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| ISandalphon |
| Posted: Thu Mar 04, 2010 3:36 am Post subject: Re: A question about time and light |
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| inow wrote: |
| inite wrote: |
| In photography, light is focused through a lens, slows down, bends, and is recorded on film |
Light never slows down. Light never speeds up. Light travels at one speed. It travels at c.
>>Brevity Snip<<< However, most assuredly, it has remained at a constant speed.
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I am puzzled about several of your answers. The notation (c) is the speed of light in a vacuum, the c denoting constant, because lights velocity is constant in a vacuum. Light is slowed when it encounters an transparent medium, water, plastics, atmospheres like earths, glass etc. The ratio of the change in velocity is called the refractive index of the medium. BTW its always greater than one, except in special circumstances which we need not go into here for brevity's sake. I'm not a scientist but that was my teaching.
We can theorize what happens to light in general terms after it crosses the event horizon of a black hole. At least we think it will not emerge again because the escape velocity of a black hole would exceed the speed of light. However you are correct in that we can not know for sure what happens, because our physics do not apply past the event horizon of the BH. There are several more statements you made I would like clarification on but will wait until you expand on the light speed issue.
IS
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Jesus Christ is my hero..
There are other worlds and rational beings of a different and higher kind. Kurt Godel |
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| ISandalphon |
| Posted: Thu Mar 04, 2010 4:40 am Post subject: |
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| 6nqpnw wrote: |
Does anyone else agree that the relationship between time and light is often confused? Isn't light used simply as a reference point for time (being that light is constant and not dynamic / variable / changing)?
Without know better how to articulate time and light, but if you travel faster than light, you're just moving faster than an image (light reflected off of matter), having NO effect on the matter itself.
- mudbug |
Probably the reason that the speed of light is associated with time is because of the relativistic effects of velocity as experienced by at least two observers. It makes time travel, ie time dilation obvious and profound. Mass can be exchanged for velocity because the gravity created by mass bends space time, the larger the mass (or the higher the velocity) the greater and more profound the effect on time.
Now, time and space are intimately linked, but not time and light. It's the spacetime we all know and love. Most look at space-time like a rubber sheet with the massive bodies like planets and stars deforming the sheet (spacetime) proportional to their mass. If you were an stationary astronaut watching your fellow piloting his craft into a (non rotating) black hole by allowing the gravity to pull him, he would appear to speed up but then slow as he approached the event horizon. Eventually his spaceship would appear to stop before entering the black hole and remain there for your life time and even our suns life time! This is because his craft would be approaching the speed of light (relative to you) as it was pulled into the black hole!
However time according to your buddies watch would pass normally! But if your bud the astronaut could be watching you in his super telescope as he drew closer and closer to the black hole it would seem as if everything was speeding up crazily, into a blur. He would see you grow old in a second, as his craft neared light speed as it drew closer to the black hole, then he would see you and die and even see our sun turn into a white dwarf, and die...
Weird huh?
IS |
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| inow |
| Posted: Thu Mar 04, 2010 6:17 am Post subject: Re: A question about time and light |
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| ISandalphon wrote: |
| I am puzzled about several of your answers. The notation (c) is the speed of light in a vacuum, the c denoting constant, because lights velocity is constant in a vacuum. Light is slowed when it encounters an transparent medium, water, plastics, atmospheres like earths, glass etc. |
No, actually. As I described above, it's not. The speed of light remains the same. The only thing which changes is its apparent speed. Each photon will still move at c, but it is being absorbed and re-emitted as it interacts with the aforementioned medium (water, plastic, glass, etc), and this makes it appear to have slowed down.
I can assure you, though, the photon is still traveling at c, and c only between each absorption and re-emission.
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iNow
~~~~~~~~~~~~~~
~~ Pale Blue Dot ~~
~~~~~~~~~~~~~~
"[Time] is one of those concepts that is profoundly resistant to a simple definition."
~C. Sagan |
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| ISandalphon |
| Posted: Thu Mar 04, 2010 7:45 am Post subject: |
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I don't like to disagree, but feel I must. First, we should agree that c indicates the speed of light in a vacuum. Specifically in a vacuum. If you were to say that the speed of light through say water was c, or that the speed of light through glass was c you would be mistaken. Additionally light can be either a photon (a massless, ie zero rest mass, zero charge elementary particle) or a wave. Here is a more detailed explanation with a link to the site ;
"Essentially the speed of radio and other electromagnetic waves too, the speed of light depends on transmission medium. The maximum speed, labelled c and often referred to as the speed of light without qualification, occurs in a vacuum, it equals 299?792?458 m·s-1 (1.079?252?85~ × 109 km/h, 670.616?629~ × 106 m.p.h.), the first figure being precise since the 1983 re-definition of the metre."
http://www.answers.com/topic/speed-of-light
I provided the link and highlighted the relevant parts for your all's convenience and to validate my statements, I realize you don't know me so I hope the link (one of thousands) will lend credence to the stranger, ie me. Thanks for your reply and I hope we can come to a meeting of minds 
IS
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Jesus Christ is my hero..
There are other worlds and rational beings of a different and higher kind. Kurt Godel |
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| 6nqpnw |
| Posted: Thu Mar 04, 2010 11:54 am Post subject: |
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PRO-CONSTANT ::: http://en.wikipedia.org/wiki/Light :::
Light always travels at a constant speed, even between particles of a substance through which it is shining. Photons excite the adjoining particles that in turn transfer the energy to the neighbor. This may appear to slow the beam down through its trajectory in realtime. The time lost between entry and exit accounts to the displacement of energy through the substance between each particle that is excited.
PRO-SLOW::: http://curious.astro.cornell.edu/question.php?number=630 :::
However, the speed of light is not constant as it moves from medium to medium.
PRO-CONSTANT::: [url]http://www.newton.dep.anl.gov/askasci/phy00/phy00111.htm [/url]:::
The light does not actually travel more slowly when in material. The light
travels from atom to atom. An atom absorbs the light for a short time and
then releases it. These short delays are what cause the apparent slowing.
PRO-SLOW::: [url]http://www.pbs.org/wgbh/nova/einstein/hotsciencelight/index.html [/url]:::
The speed of light is constant only in a vacuum, a place where there's no matter, like the vast emptiness of space. Here on Earth, the speed of light can slow down.
Some clarification is in order...DISHMEISTER...please enlighten me <<< [me so punny  ]
- mudbug
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"Imagination is E..." - Einstein |
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| Dishmaster |
| Posted: Thu Mar 04, 2010 3:56 pm Post subject: |
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Both alternatives do not contradict each other. The first link provides the explanation, i.e. the speed of light seems to alter its speed, but light is constantly absorbed and re-emitted. Each of those processes takes some time leading to the delay. An extreme example is described here:
Photon travel time inside the sun
or here:
Ancient sunlight |
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