Is there such a thing as true darkness?

DaleSpam

My two cents: the amount of radiant intensity at visible wavelengths from a 3 K black body is so low that the resulting photons would be discrete events. So there would be periods between them where the interior of the box is perfectly dark.

sophiecentaur

Or Dollop!

sophiecentaur

Where would you draw the line? All photons are 'discrete events'
It's a bit like sound radio in which all hell breaks loose at the transmitter if there's more than about one second's worth of silence 'cos they think they've lost their programme feed.

phaeton

Is energy truly not tangible? We perceive tangibly the effects of energy all around us. Light is both wave and particle, so what if substance actually is somehow both matter and energy in a similar way?

Consider this picture for a moment:


This is how I imagine light to be both wave and particle. If you look in the center you see a vase with only background on either side, but if you refocus your eyes on the background the two faces become the focus and what's in between, what was a vase, is now just background instead. Both vase and faces define each other, without one or the other the forms become meaningless. In the same way I believe waves and particles to be defining each other and making up the whole that is light. This discussion has lead me to believe there may even be a similar connection between matter and energy. This would mean that both are intrinsic in each others very being, lending credence to the possibility that both posses substance.

sophiecentaur

This wave - particle duality thing has really been done to death. Photons are Photons and Protons are Protons. Why should they have to fall into one category or another? People just have to get over it, I'm afraid. Just listen to what Feynman had to say about it. I think, in his grumpy way, he got it just right.

phaeton

lol, we'll need to petition for this indeed :D hehe
You do make a very good point though...

Drakkith

I don't see the issue here. Light has energy. Energy gravitates and contributes to the mass of a system. What possible reason would we have for trying to come up with something new and calling it "substance"?

DaleSpam

It is easy to detect a single photon with a photomultiplier tube. I would draw the line there. If a PMT cannot detect light then I would say it is perfectly dark at that time.

sophiecentaur

Now you see it - now you don't?
A bit like the direction indicators on my car. Half the time they're not working!

Why are we trying to define what we mean by 'zero' in any case? It's a bummer. You can never prove that something doesn't exist. You can only say that you didn't spot it when and where you were looking.

DaleSpam

Or half the time when they are working they are dark.

lightarrow

The connection between mass (in case you intended this with "matter") and energy is very simple: a system's mass is its energy (divided c²) in a frame of reference where the system is stationary. A photon has no mass, but a photon in a stationary box gives mass to it. The same for the photons in the universe: they give mass to it. Someone made the computation of the total mass given to the universe by CMBR's photons, but it doesn't approach dark matter's mass (for example).