Is there such a thing as true darkness?

[DaveC426913]

substance [ˈsʌbstəns]
n
1. the tangible matter of which a thing consists
2. a specific type of matter, esp a homogeneous material with a definite composition
3. the essence, meaning, etc., of a written or spoken thought
4. solid or meaningful quality
5. (Physics / General Physics) material density a vacuum has no substance
6. material possessions or wealth a man of substance
7. (Philosophy) Philosophy
a. the supposed immaterial substratum that can receive modifications and in which attributes and accidents inhere
b. a thing considered as a continuing whole that survives the changeability of its properties
8. (Christian Churches, other) Christian Science that which is eternal
9. a euphemistic term for any illegal drug
in substance with regard to the salient points

Here is what i found to be a collection of modern definitions of the word substance, I made bold the definitions which i thought to be pertinent. The first and fifth the the ones which i seem to be having trouble with. It is this definition which I seem to want to change in a way which includes energy as well. If this were the case then the fifth definition would be nullified. I believe this is a proposition worth looking into and capable of supporting. The forth definition suggests that things with meaningful qualities posses substance, and I believe photons to fall within this category.

Why? Since it doesn't fit the other definitions - eg. energy is not tangible and is not matter - why redefine a word that means one thing to mean something else? Why not redefine matter to include energy? Or solid to include vacuum? Or 'one' to include all numbers up to ten?

 

[phaeton]

To say that the universe has electromagnetic radiation throughout and conclude that it is both full of and made from some unspecified substance... That is not a coherent argument. And the conclusion is not testable.

Substance is unspecified by nature. I am proposing that substance include energy as well as mass, in which case my original question would appear to have a positive answer as opposed to negative. Attempts at the specification of energy's signatures across the universe would be the result of entirely different types of questions and research, not to mention nearly impossible.

 

[sophiecentaur]

The fact that there are so many versions of the definition of 'substance' implies that it the meaning is not universally accepted. That makes it a poor quantity to use, without explicitly defining it first (each time).

But I don't see where the terms has to be used, in any case, when the existing terms seem to serve very well.

 

[DaveC426913]

The fact that there are so many versions of the definition of 'substance' implies that it the meaning is not universally accepted. That makes it a poor quantity to use, without explicitly defining it first (each time).

Not to mention the fact that it has yet to be quantified if it is going to be used in physics.

We can't use kg, as that is a matter unit. We can't use Joules as that is an energy unit. I propose we use the unit gubbin.

"This volume of space contains several planets - at least a Gigagubbin. But it is also strongly irradiated by its sun, comprising another 2 Gigagubbins of substance."

 

[Dale]

Even if you shut yourself in a perfectly opaque box in deep space, the box will come in thermal equilibrium with the cosmic microwave background, rise to 3 kelvin, and reradiate that heat continously according to a (mostly) blackbody curve. Even at just 3K, there is some amount of radiant intensity at visible wavelengths.

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]

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.

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]

Why? Since it doesn't fit the other definitions - eg. energy is not tangible and is not matter - why redefine a word that means one thing to mean something else? Why not redefine matter to include energy? Or solid to include vacuum? Or 'one' to include all numbers up to ten?

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]

Not to mention the fact that it has yet to be quantified if it is going to be used in physics.

We can't use kg, as that is a matter unit. We can't use Joules as that is an energy unit. I propose we use the unit gubbin.

"This volume of space contains several planets - at least a Gigagubbin. But it is also strongly irradiated by its sun, comprising another 2 Gigagubbins of substance."

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"?

 

[Dale]

Where would you draw the line?

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.

 

[Dale]

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

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

 

[lightarrow]

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.

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).

 

[Romulo Binuya]

Considering that what most people think of as light is just the visible spectrum of electromagnetism, while much more exists on either end, are the frequencies beyond either end of the visible spectrum still light? If so, since electromagnetic fluctuations permeate the known universe, is there any such thing as true darkness?

Not true darkness but close to the darkness that you are inquiring about. There is a cold spot in the CMB map that ESA's Planck satellite had plotted, I assume there is very few em waves there. WMAP satellite detected it too, and VLA radio telescope looked at it too and saw fewer galaxies. Boomerang nebula is the coldest in the observable universe but I saw a lot of em waves there hence it's unlike the CMB cold spot.

Btw, the CMB cold spot is located in the constellation Eridanus, a string of stars which start at the vicinity of the Orion's Rigel. And the Orion is rising after midnight this time of the year, interested to see darkness through a telescope? Maybe not :D

 

[A.T.]

Considering that what most people think of as light is just the visible spectrum of electromagnetism, while much more exists on either end, are the frequencies beyond either end of the visible spectrum still light? If so, since electromagnetic fluctuations permeate the known universe, is there any such thing as true darkness?

A black hole is rather dark. But the collapsing matter around it might obscure the view on its absolute darkness.

 

[voko]

A black hole is rather dark. But the collapsing matter around it might obscure the view on its absolute darkness.

No, that is not true at all. Matter spiraling into a black hole radiates. The black hole itself emits Hawking's radiation.

 

[Chronos]

Photons have only been free to roam the universe since the time of recombination. Prior to that they were trapped in a dense plasma that permeated the entire universe.

 

[Jay Nazareth]

Using what everyone has posted it could be that photons are a substance, since everything is composed of energy. But seeing that most people would try to argue that "specific type" of energy is what matters. I leave it as a case solved for now till we have more information regarding "energy".

 

[Drakkith]

Using what everyone has posted it could be that photons are a substance, since everything is composed of energy.

In the end this boils down to semantics, not physics. We know what light is. We know what energy is. Those are not mysterious in any way. The physics is not in question here, merely the meaning of words, which is a near-pointless argument. If you want to call photons a substance, then go right ahead. Just be aware that most people do not and you're going to have a difficult time communicating effectively if you choose to use words in a non-standard way.