[HPforGrownups] A functional cloak of invisibility ? what?

[Bart Lidofsky]

No: HPFGUIDX 192359

On 4/22/2013 10:06 AM, MadameSSnape at aol.com wrote:
> Only problem with invisibility is, as was pointed out decades ago in a MAN
> FROM UNCLE novel about an invisible dirigible, if you're invisible you're
> also  blind, because light rays passing through your body also pass through
> your  eyeballs.  If your eyeballs don't catch light, you can't see.  And you
> tend to bump into things, which rather defeats the purpose of being
> invisible in  the first place, n'est ce pas?

Bart:
Functional invisibility can be done in numerous ways. There is, for 
example, a chameleon effect, where the front of the invisibility 
"shield" projects what would be seen if there was nothing there; it can 
still let light through. And of course, since we are talking magic, 
there is also a "glamour"; the object being hidden is perceived as 
something that belongs there, and is therefore ignored.

There is an old joke which illustrates this:

At a construction site, there was a security guard. Every day, at 
quitting time, a worker came out with a wheelbarrow filled with dirt. 
The guard was certain that the worker was concealing something that he 
stole in the dirt, so every day, the guard would examine the dirt, and 
would find nothing else. Several years after the job had been completed, 
the guard came across the worker in a bar. He approached the worker.

"I know you were stealing something in that job!" said the guard. "The 
statute of limitations is up, so you can't be arrested. So can you 
please tell me what it was you were stealing?"

The worker smiled, and replied, "Wheelbarrows."

     Bart