[FRIAM] Illusion

[Stephen Guerin]

As a closed system (not isolated), I was curious why the plastic wrap
wouln't return to flat after is convex expansion as it returned to initial
room temperature.

Is it related to the hysteresis in the asymetry of the boiling curve vs
condensation?





____________________________________________
CEO Founder, Simtable.com
stephen.guerin at simtable.com

Harvard Visualization Research and Teaching Lab
stephenguerin at fas.harvard.edu

mobile: (505)577-5828

On Tue, Oct 22, 2024, 8:21 AM Nicholas Thompson <thompnickson2 at gmail.com>
wrote:

> To produce the illusion:
>
> Take an ordinary water glass, put a little water in it, stretch some
> plastic wrap tightly over the glass and put  it in the microwave for a few
> seconds.
>
> Leave it in the microwave for a minute to cool down .(Please don't do
> anything stupid and scald yourself.)
>
> Remove the glass (see above, "....stupid") from the microwave. The
> plastic should have formed a concave beaded surface on the top of the=
> glass.
>
> Wonder, "What is the mathematical form of that  surface?"
>
> Examine the surface under a vertical  lamp (like a  desk lamp or a ceiling
> bulb)
>
> An image of  the  lamp willl appear floating inches above the surface of
> the plastic.
>
> Tilt the glass just right, and you will see a *convex* surface enclosing
> the top of the glass.
>
> Wonder:  "Have I made a parabolic surface?"
>
> Write email to Friam.
>
> Receive dope slaps from colleagues for not looking it up on the internet
> first.
>
>
>
>
>
> --
> Nicholas S. Thompson
> Emeritus Professor of Psychology and Ethology
> Clark University
> nthompson at clarku.edu
> https://wordpress.clarku.edu/nthompson
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