@CiaraMK sent me this amazing illusion.  Click on the image to open it as large as possible and wait for it to get running.  Then, when you cover up the centre of the image with your hand the dots will appear to speed up.  Cover up the edges and they slow down.

Does it work for you?


  1. Yes, it works for me. Just guessing here, but does this illusion work because the dots are expanding outwards from the centre?

  2. Good one. I guess its because our eyes cant judge speed very well when we have an object heading straight at us.

  3. Objects closer to us appear to move faster. So far away objects (in the centre) are moving slower. As objects get close and go “past” us they move to the edge, and faster past us.

    You’re effectively asking us to cover the slow moving dots in the middle, and then the fast moving dots at the end.

  4. I was about to comment, when I saw that Paul had said what I was going to say. The dots on the edge are moving faster in order to give the illusion that they are moving towards us. If they were not moving faster, it would like rings expanding in water.

  5. It works great!

    The dots on the edges are faster than those in the middle. When you see all, it averages the speed visually.

  6. As M says above;

    This is not an illusion. The dots on the outside really are moving quicker.

    If anything, the illusion is that it appears all dots are moving at the same speed when viewing the image as a whole as, due to the speed differences, you brain interprets it as if you are moving through through the dots (as if they were stars in space).

  7. Of course the dots at the outside are moving quicker! I took Richard to mean they will speed up / slow down “relative to what they were before” when you cover these areas, which in my case, they do. Fantastic illusion.

    1. “Geoff Says: I took Richard to mean they will speed up / slow down “relative to what they were before” when you cover these areas, which in my case, they do.”

      I agree! That’s exactly what’s happening. So quit the moaning, it’s a very good illusion! 🙂

  8. I tend to concur with Aisling and Geoff above – they speed up and slow down relative to what they were, not to each other. Fascinating illusion, +1.

    1. More specifically, motion parallax.

      Interpreting the dots as a scifi-style “star field” I didn’t find anything noticeably illusory on covering parts of the image.

  9. Also not quite an illusion as dots get bigger towards edge from original size in middle, just like watching snow fall from above! Still good fun!

  10. The dots at the edges are going faster than the ones in the middle, but they definitely appear to speed up significantly compared to what they were when I cover the centre – that’s one of the best illusions I’ve seen, I must admit.

  11. Nope, just looks like that stars screensaver from win 98 only in negative.

    Hardly justifies the “best ever” title?!?

  12. So things that are actually moved at a higher speed than things which are actually moved at a lower speed also appear to be moved at a higher speed than things which are moved at a lower speed.

    Good “illusion”.

  13. The dots in the center don’t move as far as the ones towards the edge. They appear for the same amount of time and therefore are literally moving slower.

    A bit like the outside edge of a record moves faster than the inside

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