OneGuyFromBarlick

Is it part of an air-con unit?

Sorry Cathy but no.....

Looks like an entry/exit point for kitchen cooker hood ducting.

Sorry Graham but no....

I know what it must be but I'll keep stum for now. Clue...Terry Pratchett would have loved this - in his Discworld books there were always things that were `darker than the blackest black'.

Something to do with nanoparticles? Or black holes? Or Buckeyballs?

Is it black paint?

Reminds me of the time we used to (try) to do calcs using the Stefan–Boltzmann law. Starting with a black that absorbed all radiation then compared the heat absorbed from other less black thingies. Read not long ago that the labs had achieved another level of blackness that could be used on camera lenses or something like that. Space exploration come to mind.

You're all getting there. Basically you are all right but not precise but I am giving it to all of you.
It's Vantablack a pigment coating developed in 2014 by Surrey NanoSystems. The name is an acronym for Vertically Aligned Nano Tube Array Black. The company says Vantablack absorbs 99.965 percent of light, which made it the blackest of all blacks at the time. (January 2021) (I think Peter knew it as well.)
Next one please?

Black is always difficult to reproduce in any form as it doesn't actually exist! Black is merely the absence of all light so cannot be reproduced by artificial means. Blacks are usually extremely dark blue or leaning to the purple end of the spectrum. It's all an optical illusion. As demonstrated above some are better attempts than others.

That was an interesting one Stanley.

PanBiker wrote: ↑22 Sep 2021, 07:44 Black is always difficult to reproduce in any form as it doesn't actually exist! Black is merely the absence of all light so cannot be reproduced by artificial means.

On a more technical level what we perceive as black is something that absorbs all our visible light radiation and doesn't reflect any particular wavelength (colour). Our eye balls are not very good at this quantitative analysis so we rely on instruments for a better judgement.
Can't understand how Black Holes can still radiate but I suppose not many people can.

plaques wrote: ↑22 Sep 2021, 08:37 Can't understand how Black Holes can still radiate but I suppose not many people can.

It's that nasty quantum stuff again!
`Why Black Holes Emit Light: A Simplified Explanation of the Physics Underlying the Hawking Radiation'
LINK

What exactly is it.

A cannon ball or a musket ball depending on its size?

A wholemeal loaf?

A lump of iron?

Kev and China are right, it's a lump of iron, but very special iron. Go a bit further. (Clue, it isn't strictly iron....)

Is it a steel ball bearing that is well past its sell-by date?

No, far older than that.

Wootz?

A nickel-iron meteorite?
Or a marcasite (iron sulphide) nodule?

Kev has it, It's a cake of Wootz, the steel that was produced in small quantities by skilled smiths in the Far East long before we made it common in the Industrial Revolution.
Next one?

Wotz Wootz?