In פרשת בשלח 16:14, it says --

The layer of dew went up, and behold, on the surface of the desert, a fine, bare [substance] as fine as frost on the ground.

On that verse, Rashi says (translated from here)

When the sun would shine, the dew upon the manna would rise toward the sun, as it is natural for dew to rise toward the sun. [This is similar to] even if you fill an egg shell with dew, close up its opening, and place it in the sun, it [the egg shell] will rise by itself in the air

Is this actually true scientifically? Has anyone ever tried or seen this?

  • 2
    @DoubleAA Sounds like a fun question....but probably a better fit on Physics, no?
    – MTL
    Jul 4, 2014 at 3:56
  • 2
    Also, @DoubleAA, does that Rashi have to mean the eggshell, and not the dew itself in the form of steam?
    – MTL
    Jul 4, 2014 at 4:01
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    @Shokhet He says היא whereas טל is masculine, I think.
    – Double AA
    Jul 4, 2014 at 4:14
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    @Shokhet כַּאֲשֶׁר יִפֹּל הַטַּל עַל-הָאֲדָמָה (Sh'mu'el II 17:12). However, Rashi may have been referring to שכבת הטל, even though he omitted the word שכבת. That's feminine.
    – Fred
    Jul 4, 2014 at 5:06
  • 4
    Someone on the internet claims to have conducted this experiment multiple times, and says that one time the egg rose a few centimeters.
    – Fred
    Jul 4, 2014 at 5:12

1 Answer 1


First off, I would assume that the concept here would be kinda like a hot air balloon. However, I do know someone who tried, but it didn't work. (that doesn't really mean much, because there are so many things Rashi didn't describe exactly how to do, it should be very easy to go wrong.)

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