[DoctorBeaver (OP)]

Here is a link to a page on which is a clip of the recent Iranian missile test. It seems that something shoots across the sky and causes a rip in the cloud.

http://www.thesun.co.uk/sol/homepage/news/article2670396.ece

I've seen it suggested that it's the shadow of the rocket, but I don't see how that can be the case. It certainly looks like a shadow but the cloud is above the rocket so any light source causing such a shadow would need to be on or near the ground.

I'd be interested to hear other's views on this.

[JP]

I'm going with shadow of the rocket.  The light on the rocket's trail seems to be from the right-hand-side of that screenshot.  This would cast a shadow somewhere to the left, and that's where the "UFO trail" is situated.

I've seen really weird effects like this myself, where airplane contrails cast shadows on some distant cloud in a way that seems impossible.  I think its just that objects in the sky are so far apart that it's nearly impossible to correctly judge distances and orientations from our vantage point in the ground.

[neilep]

it's aliens I tell ewe ..ALIENS !!..they are amongst us now......one has been posing as my wife since this morning !..the give away ?...she actually made some edible toast !!........they are here !!

[JP]

Hmm...

[Karen W.]

LOL...LOL....LOL...Poor Sheepy... Gone with the Big green beam of light!  ZWOOOP.......

[RD]

BBC has video of the cloud slice occurring...

 [ Invalid Attachment ]

http://news.bbc.co.uk/1/hi/8277040.stm

There is an explosion near the tip of the rocket at 1:00, some of the bigger ejected bits are visible ...

 [ Invalid Attachment ]

A smaller fragment from this explosion would be invisible and could be travelling at a much greater speed
than the bigger visible bits, so could be the cause of the cloud split.

[RD]

I've converted to the shadow camp.

The slice (shadow) moving right to left would be possible if the cloud was backlit,
 and the cloud was closer to the viewpoint than part of the missile trail casting the shadow.

[The cloud where the "slice" appears looks like a old trail from a previous launch].