Lightspeed query

Just a wonder.

Let's say that we could travel at light speed.

If we were 1000 light years away from a sun, and that sun turned super nova 500 years ago, is it right to assume that it would take 500 years for the light to vanish from our sky?

Also, if we were to travel towards a sun that had gone super nova, would we see it go super nova in fast motion?

If we were to travel at 0.9 light speed AWAY from it... a fraction of a second before the 1000 years had passed, would we see it turn in slow motion?

Finally, if we were to travel exactly 1 light speed away, exactly as it turned... would we see it in a frozen position?

The way I'm seeing it now is basically how old day cameras compare to nowadays. It used to take so long to actually capture the photo that anyone moving was either a blur, or completely invisible from the frame. The guy/girl having their photo taken would need to sit still for around 10 minutes, I seem to recall. Where nowadays we can take photos of fast moving objects, and freeze them perfectly in mid motion without blur.

All this time and space stuff is confusing me. If someone could help explain a few of these situations to me, that would be great.

[edit on 14-12-2008 by 4demon]

One thing im sure of is the speed of light is not constant.
All the rest is a little beyond me right now.

Look, it is a complex thing, and it is based on relativity, and everthing you see in the universe is relativistic to your viewpoint alone, if you manage to escape the time cone/tyndall cone of the supernova, you escape the supernova explosion and for that you would have travel faster than the speed of light, but in the case of you matching with the cone, then for you it will seem that time has stopped, but it is relativistic to you alone and not the entire universe, and if you go slower than that of the tyndall cone, you enter the future cone and see the supernova explosion.

And regarding the photography, it is based on tehcnology, in those days, the light has to fall on photographic plate to produce for a specific time to produce sufficient intensity for the photo to be developed on the film, and now technology has devleoped that, you dont need films and all is digital, and the detectors used are so advanced that, all that is needed is a millisecond or so to record the light, and even the slow motion cameras work on the same principle, taking nearly hundered photos a second to provide the slow motion effect.

The speed of light is a constant, it travels the same speed no matter what your viewpoint is, or how fast you are traveling in relation to anything (assuming you are in a vacuum such as space). It therefore plays a very important part in modern physics.

This 'might' help a little:




Oh and more reading here:
math.ucr.edu...

[edit on 14-12-2008 by Toasty]

well the old photographic plates and early films had ridiculously low sensitivity to light ("asa" or "iso" in europe) a photographic a film frame is like an empty bucket . A certain quantity of light fills the bucket to the proper level provide a proper exposure.for a full tonal range; from darkest dark to brightest bright.you can open up the aperature and allow more light in and shorten the time it has to expose the film by adjusting the shutter speed. the two ajdjustments(aperture and shutterspeed) are reciprocal. So 1/60 ofa second at f16 provides the exact same exposure(same amount of light) as can 1/125 off a second at f11. or 1/30 of a second at f 22 (full stop adjustments) old filmsand plate had exposure in the minutes, course youcan expose modern film for minutes with a small enough aperature or low enough light level and get some cool stuff.you can't see with the naked eye.

High school physics: light speed IS constant, space distorts, if you ride on top of a train and turn a flash light on pointed forward the photons don't travel at light speed + the train speed. Sorry Einstien was one smart dude...I don't really get it all either..and can't answer your situation questions.

paths!!

on what path does loght follow?

there is a thing faster than light becouse of its pretex

light>path < understanding

Light is just one of many paths

Originally posted by Toasty
The speed of light is a constant, it travels the same speed no matter what your viewpoint is, or how fast you are traveling in relation to anything (assuming you are in a vacuum such as space). It therefore plays a very important part in modern physics.

This 'might' help a little:

Oh and more reading here:
math.ucr.edu...

[edit on 14-12-2008 by Toasty]

I will say your are wrong in this... light is only a object... yes and object

you see for it to go the speed it does it has to be on a track to do wha its doing

I can and do violate it every time i dream.

Nothing can travel faster than light>

really? thing of a highway and car.. the highway is what light travels ON or in..

for light to go were its going it needs a road a guid a highway!! there is not speed there is only the road

now you undertand why aliens get here.. they undertand or did BUILD the highway on what light travels on

lol my brain hurts

Well, It seems that the jury is still out on this question.
Last year I would have said that the speed of light (and information, according to Einstein) Was the
cosmological speed limit. And I would have answered the OP with yes on all his questions.
Not only do we have the duality of light conundrum (wave/particle) but now we must contend with this very very strange added problem.

If you thought the speed/nature of light problem was confusing before, it just got way worse!

This is really mind blowing stuff.

Here is some light reading on the matter:

See the backward light animation
View mpeg click here

From The University of Rochester Laboratory for Laser Energetics:
Source

Light's Most Exotic Trick Yet: So Fast it Goes . Backwards?
In the past few years, scientists have found ways to make light go both faster and slower than its usual speed limit, but now researchers at the University of Rochester have published a paper today in Science on how they've gone one step further: pushing light into reverse. As if to defy common sense, the backward-moving pulse of light travels faster than light.
Confused? You're not alone.
"I've had some of the world's experts scratching their heads over this one," says Robert Boyd, the M. Parker Givens Professor of Optics at the University of Rochester. "Theory predicted that we could send light backwards, but nobody knew if the theory would hold up or even if it could be observed in laboratory conditions."
Boyd recently showed how he can slow down a pulse of light to slower than an airplane, or speed it up faster than its breakneck pace, using exotic techniques and materials. But he's now taken what was once just a mathematical odditynegative speedand shown it working in the real world.
"It's weird stuff," says Boyd. "We sent a pulse through an optical fiber, and before its peak even entered the fiber, it was exiting the other end. Through experiments we were able to see that the pulse inside the fiber was actually moving backward, linking the input and output pulses."
So, wouldn't Einstein shake a finger at all these strange goings-on? After all, this seems to violate Einstein's sacred tenet that nothing can travel faster than the speed of light.
"Einstein said information can't travel faster than light, and in this case, as with all fast-light experiments, no information is truly moving faster than light," says Boyd. "The pulse of light is shaped like a hump with a peak and long leading and trailing edges. The leading edge carries with it all the information about the pulse and enters the fiber first. By the time the peak enters the fiber, the leading edge is already well ahead, exiting. From the information in that leading edge, the fiber essentially 'reconstructs' the pulse at the far end, sending one version out the fiber, and another backward toward the beginning of the fiber."
Boyd is already working on ways to see what will happen if he can design a pulse without a leading edge. Einstein says the entire faster-than-light and reverse-light phenomena will disappear. Boyd is eager to put Einstein to the test.
So How Does Light Go Backwards?
Boyd, along with Rochester graduate students George M. Gehring and Aaron Schweinsberg, and undergraduates Christopher Barsi of Manhattan College and Natalie Kostinski of the University of Michigan, sent a burst of laser light through an optical fiber that had been laced with the element erbium. As the pulse exited the laser, it was split into two. One pulse went into the erbium fiber and the second traveled along undisturbed as a reference. The peak of the pulse emerged from the other end of the fiber before the peak entered the front of the fiber, and well ahead of the peak of the reference pulse.
But to find out if the pulse was truly traveling backward within the fiber, Boyd and his students had to cut back the fiber every few inches and re-measure the pulse peaks when they exited each pared-back section of the fiber. By arranging that data and playing it back in a time sequence, Boyd was able to depict, for the first time, that the pulse of light was moving backward within the fiber.
To understand how light's speed can be manipulated, think of a funhouse mirror that makes you look fatter. As you first walk by the mirror, you look normal, but as you pass the curved portion in the center, your reflection stretches, with the far edge seeming to leap ahead of you (the reference walker) for a moment. In the same way, a pulse of light fired through special materials moves at normal speed until it hits the substance, where it is stretched out to reach and exit the material's other side [See "fast light" animation].
Conversely, if the funhouse mirror were the kind that made you look skinny, your reflection would appear to suddenly squish together, with the leading edge of your reflection slowing as you passed the curved section. Similarly, a light pulse can be made to contract and slow inside a material, exiting the other side much later than it naturally would [See "slow light" animation].
To visualize Boyd's reverse-traveling light pulse, replace the mirror with a big-screen TV and video camera. As you may have noticed when passing such a display in an electronics store window, as you walk past the camera, your on-screen image appears on the far side of the TV. It walks toward you, passes you in the middle, and continues moving in the opposite direction until it exits the other side of the screen.
A negative-speed pulse of light acts much the same way. As the pulse enters the material, a second pulse appears on the far end of the fiber and flows backward. The reversed pulse not only propagates backward, but it releases a forward pulse out the far end of the fiber. In this way, the pulse that enters the front of the fiber appears out the end almost instantly, apparently traveling faster than the regular speed of light. To use the TV analogy againit's as if you walked by the shop window, saw your image stepping toward you from the opposite edge of the TV screen, and that TV image of you created a clone at that far edge, walking in the same direction as you, several paces ahead [See "backward light" animation].
"I know this all sounds weird, but this is the way the world works," says Boyd.

Weird stuff indeed! I think that even Einstein would be scratchin' his head about this high strangeness. But in reality, this does not violate his theories, but it sure is "warping" them a bit.

Peace

reply to post by Toasty


Toasty, while your examples are a great demonstration.

They are 10 years old.

I would just like to point out to you that there are new possibilities in
measurement of c. Quantum tunneling seems to be a possibility for FTL.
These still cannot be ruled out, paticularly in view of this strange measured observation.

See my above post and info about May of 2006 info about laboratory demonstrations of the possibility of FTL.

I believe that Einstein was aware of the mathematical possibility.
Could this be an effect of what he called "spooky effects at a distance"?

Peace

reply to post by Zeptepi


That really is some crazy stuff, thanks for the post Zeptepi. I remember reading an article not long ago about them doing experiments where the light detectors would go off BEFORE the light was sent, in essences, traveling in reverse.

Light seriously is weird stuff and I don't think we know half of what it is and how it works. I remember reading in the free book 'God's Debris' by Scott Adams about his 'fictional' explanation of light. He describes light as a probability, not so much as a thing. The more light, the higher probably of ... i don't know what. Very weird but interesting read also.

I'd just like to add also, quantum entanglement still maintains Einstein's theories as from what I understand, no information can be transferred? Particle spin is undeterminable, so essentially eliminating any forms of communication.


[edit on 15-12-2008 by Toasty]

Originally posted by 4demon
If we were 1000 light years away from a sun, and that sun turned super nova 500 years ago, is it right to assume that it would take 500 years for the light to vanish from our sky?

Actually, it would take that long for the light to appear in our sky. And - since supernovas don't last long - to vanish, too.

Also, if we were to travel towards a sun that had gone super nova, would we see it go super nova in fast motion?

No. This would only happen if the velocity of the supernova light relative to us was greater than c. That (pace Zeptepi) is not possible, wo we would see the star explode in real time. However, the Doppler effect would mean that the light from it would be blue-shifted, so you would see it in different colours (and with lots more action in the UV and X-ray bands).

If we were to travel at 0.9 light speed AWAY from it... a fraction of a second before the 1000 years had passed, would we see it turn in slow motion?

No, for the same reason as above. This time, the light would be red-shifted.

Finally, if we were to travel exactly 1 light speed away, exactly as it turned... would we see it in a frozen position?

We cannot travel at the speed of light, so the question doesn't arise.

Edited to correct a small error in the answer to the first question.

[edit on 15-12-2008 by Astyanax]

reply to post by Toasty

Light seriously is weird stuff and I don't think we know half of what it is and how it works.

On your above statement, I could not agree more.
I tend to try not to hold onto theories in physics too strongly, or as some dogma that must be defended. I am hopeful that a day will come when the paradigm will again be elevated, like the the one Einstein offered over Newton.(If Mankind can make it that far)

quantum entanglement still maintains Einstein's theories as from what I understand, no information can be transferred? Particle spin is undeterminable, so essentially eliminating any forms of communication.

Yes, That is indeed my understanding as well...dangit...I really want to get a ticket for breaking the laws of nature...ha ha (my sig. line)
And If Prof. Boyd is able to create a square pulse, (no small feat in itself) I really do think the effect he measured will indeed disappear.Reducing his results to just a kind of parlor trick, of sorts.If not, I really will be totally baffled. Won't we all be?

Thanks for the link to the free book! I am off to read it now.

Peace

reply to post by Astyanax


Very interesting. Thank you, but I did mean to suggest that if it were possible to travel (IF) what would we see?

I remember seeing an advert a while ago where a bullet is shot as a man drives his car. He is travelling so fast that to him, the bullet appears as though it is stationary. He winds down his window and lets the bullet pass right in front of him.

This is how I imagined it to work, but I hadn't even considered the doppler effect, so that makes things very interesting indeed.

I'm trying to imagine light as physical particles, it seems. Is it really that different? Take the bullet idea. If a bullet were to be fired in a zero gravity environment, and a camera was to be travelling at the same speed (how fast does an average bullet travel from an average gun?), would the doppler effect change the way it looked? Travelling at the same speed, looks nornal, slower, looks stretched, faster, looks squashed?

By the way, I have no idea about physics, etc... which probably shows but this is just the way my simple brain is comprehending this scenario. To me, this is what makes sense, and seems most likely. But what's best, I feel, is when things don't make sense, or work the way you expect. Makes you think that we could be wrong about a lot of things... that anything is possible.