Dangerous concave mirror starts fire

[Flyfisher]

:lol:

 

[Schoolmarm]

:lol: :lol:

 

[Feltwell]

Unpredictable implies unknowable, which is not the same as unknown.

Exactly. As Donald Rumsfeld famously said:-

"Reports that say that something hasn't happened are always interesting to me, because as we know, there are known knowns; there are things we know we know. We also know there are known unknowns; that is to say we know there are some things we do not know. But there are also unknown unknowns - the ones we don't know we don't know."

 

[Gervase]

If only Rumsfeld always spoke as much sense. I can't see why he was pilloried for making, to me, one of the most sensible encapsulations of intelligence I've come across.

 

[biffvernon]

Spot on Gervase. That was probably the only sensible thing Rumsfeld ever did say.

 

[Gervase]

However the slippery neo-con stoat may only have been plagiarising Thoreau's "to know that we know what we know, and that we do not know what we do not know, that is true knowledge".

 

[skier-hughes]

but surely as the sun rose it's angle to the mirror would change and therefore the actual fire starting in earnest is quite improbable?

 

[biffvernon]

Like wot I said.

 

[Cloudscape]

It happened because somewhere, thousands of miles away, a butterfly flapped its wings.

 

[Gervase]

Archimedes was supposed to have saved Syracuse using 'burning mirrors' (καυστικά κάτοπτρα) to set fire to the Roman galleys of Marcellus. I seem to remember that an experiment to try to recreate the effect was a dismal failure.

 

[michael]

One of those large ugly steel and glass buildings has just been built next to the railway station in our town. The elevation of the building that looks over the station forecourt is concave and faces south west. At about 2.pm on a sunny day back in February, I noticed that a concentrated beam of sunlight reflected of this glass concave elevation right across the station entrance. You could physically feel the heat on your neck as you walked through the beam. Hopefully the higher angle of the sun as summer approaches will eliminate this problem if not I think it will eliminate people, vaporising them as they walk out of the station entrance. “Welcome to our town”