I don't know pretty much about physics and I'm sorry if there is something I should know that simply makes it clear this couldn't happen.

But I asked this myself now already several times and decided to post it here:

If I'm remembering right from my high school times, light is moving with a constant speed but is affected by obstacles so I assume it could be possible that the light emitted by an object may be slowed on its way to my eye.

So given that to this object something happens that makes it looking quite different and the light before and after the change of appearance is now on the way to my eye and on the way any kind of event (like "a wild vacuum appears"...) occurs that makes the light waves which are behind speed up a bit so that they both arrive and get noticed (absorbed or what ever it would be called) by my eye at the same time, what would it look like?

Would I see the object as something like it never actually looked like and I would notice the mixture of the both objects colours?

What if it also changed its shape and form? Would I just see both objects together or would some blur-like effect appear?

  • 2
    $\begingroup$ Look at an object and its image in a mirror. That's what that looks like. $\endgroup$
    – CuriousOne
    Commented Sep 11, 2015 at 7:13
  • $\begingroup$ @CuriousOne: how can an object and an image of it be in the same place at the same time just by observing it through a mirror? (sorry If I missunderstood you) $\endgroup$
    – Zaibis
    Commented Sep 11, 2015 at 7:26
  • $\begingroup$ But light is not slowed. $\endgroup$
    – paparazzo
    Commented Sep 11, 2015 at 8:24
  • 1
    $\begingroup$ @Frisbee: What is then the sense of defining the constant speed of light by "at vacum" if it isn't slowed anyway? $\endgroup$
    – Zaibis
    Commented Sep 11, 2015 at 8:56
  • $\begingroup$ @Frisbee: If there is no way to manipulate the speed of light, I see why this question doesn't make sense. But by that definition I thought it may be possible. $\endgroup$
    – Zaibis
    Commented Sep 11, 2015 at 8:58

2 Answers 2


Since your brain does not know that the light it receives is from the same object at different times, it will assume that there are two different objects at the same place and will superimpose the images on each other.

Also, please note that light cannot be speeded up more than 299792458 m/s, but it can definitely be slowed down by passing through materials with refractive indices >1. So, this is definitely possible.

  • $\begingroup$ So my assumption about the speed of light was correct and the comments to my OP which I tryed now to integrate into my view of colours and light, were wrong so I should just try to discard them again? $\endgroup$
    – Zaibis
    Commented Sep 11, 2015 at 11:05
  • $\begingroup$ Yes. You can read elementary texts on refraction to see why light slows down when it passes through certain mediums. $\endgroup$
    – sarat.kant
    Commented Sep 11, 2015 at 11:09

If you wear a pair of goggles and the image stream reaching the left eye arrives slightly after the other you may get the effect you are looking for.

The difference of arrival times could be adjusted to be very small.

I do not know how you would perceive the object or whether there would be any value to the experiment.

  • $\begingroup$ Not it wouldn't since I'm not talking about the arrival on my eyes relative to each other, I'm talking about the light of the same object ariving my eyes in the same relation but that the light waves of the one event are a little bit slower than the others so that in the moment the first event should be captured by my eyes, the waves of both events get captured (just in the way they would do after each other regularly)so that they arrive at the same time while they should just do sequenced and not collected. And I have no clou how goggles or mirrors should help with that $\endgroup$
    – Zaibis
    Commented Sep 11, 2015 at 11:23
  • $\begingroup$ Well ,can you not just combine the streams so that the same (combined) stream reaches both eyes at the same time?I see little point in this as the brain would have even less ability to separate the two streams. $\endgroup$
    – geordief
    Commented Sep 11, 2015 at 11:25
  • $\begingroup$ Hm I don't know how I should do this. but as I said, my knowledge about physics is very limited. $\endgroup$
    – Zaibis
    Commented Sep 11, 2015 at 11:27
  • $\begingroup$ You could do a similar thing with sound.And when you listen to stereophonic music with headphones your brain combines the two streams into one experience. $\endgroup$
    – geordief
    Commented Sep 11, 2015 at 11:29
  • $\begingroup$ This confirms my assumption but my question is still how it would appear. $\endgroup$
    – Zaibis
    Commented Sep 11, 2015 at 11:33

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