illusory motion

[Kaushik Sridharan]

> My stove (aka range or cooker) is a gas stove; it burns natural gas.  It
> lights the natural gas with electrical sparks; there's a small electrode
> in a little cubbyhole inside one side of the burner.  When it's making
> sparks, the sparks visually appear to begin from the electrode and grow
> outward toward the inside of this cubbyhole.
>
> I don't think that's what's actually happening, though.  I think the
> spark forms much too fast for me to notice it.  But I notice that the
> part of the spark adjacent to the electrode is noticeably brighter than
> the rest of the spark.  I hypothesize that it registers more quickly in
> my eye because it is brighter, and that the rest of the spark gradually
> registers after that.

Another example: during thunder storms, lightening bolts work their way up
from the ground, although it looks as if it's the other way round.

Kaushik