Curiosity on the relationship between matter and energy

[Silverstreak]

I know that there is Einstein's equation that relates energy and matter. However, I was curious about what would occur if there was a universe where light didn't exist. Assuming that's even possible, would there be any relationship between matter and energy or would they be completely separated? Would they fail to exist in such a place? Thank you for indulging my curiosity.

[exchemist]

17 minutes ago, Silverstreak said:

I know that there is Einstein's equation that relates energy and matter. However, I was curious about what would occur if there was a universe where light didn't exist. Assuming that's even possible, would there be any relationship between matter and energy or would they be completely separated? Would they fail to exist in such a place? Thank you for indulging my curiosity.

The relationship would still exist, I think, since both energy and mass are properties of matter that do not depend on light. By the way the equation does not relate energy with matter: it relates energy with mass. That distinction is important.

[Sensei]

24 minutes ago, Silverstreak said:

I know that there is Einstein's equation that relates energy and matter. However, I was curious about what would occur if there was a universe where light didn't exist. Assuming that's even possible, would there be any relationship between matter and energy or would they be completely separated? Would they fail to exist in such a place? Thank you for indulging my curiosity.

The whole subject is so deep, I don't even know where to start..

 

How about pair production?

https://en.wikipedia.org/wiki/Pair_production

[swansont]

5 hours ago, Silverstreak said:

I know that there is Einstein's equation that relates energy and matter. However, I was curious about what would occur if there was a universe where light didn't exist. Assuming that's even possible, would there be any relationship between matter and energy or would they be completely separated? Would they fail to exist in such a place? Thank you for indulging my curiosity.

E=mc^2 is not directly predicated on the existence of the electromagnetic interaction; c is the speed of any massless particle.

However, physics is inter-related. You can’t just arbitrarily change part of it and think that change would be isolated.

[Genady]

Moreover, it is not necessary for c to be a speed of anything. It is a coefficient in the spacetime metric.

[MigL]

7 hours ago, Silverstreak said:

I know that there is Einstein's equation that relates energy and matter.

There is no such thing.
The relationship is between energy and mass.
They are different facets of the same thing; one being the ability or potential to do something, the other being the resistance to doing something.

7 hours ago, Silverstreak said:

what would occur if there was a universe where light didn't exist

Are you maybe under the impression that light is energy?
That is another common misconception because we get energy from the Sun as light.
Light is siply the vehicle that transfers energy from the Sun to the Earth.
Both renergy, and mass, are properties of systems ( and/or matter ), and so light has the property of energy, but it has no mass.
However, in special circumstances, its property of energy can be converted, so that energetic ( but massless ) light gives rise to two particles with mass ( but much less energy ).
The process can also be reversed so that two massive particles can annihilate to become a photon of light.

These processes involve many other properties of systems ( and matter ) such as momentum and charge, which dictate if and how the processes evolve.
As Sensei mentioned, the subject gets complicated very quickly; I hope I helped with some of the basics.

Edited February 18 by MigL

[Killtech]

8 hours ago, Silverstreak said:

I know that there is Einstein's equation that relates energy and matter. However, I was curious about what would occur if there was a universe where light didn't exist. Assuming that's even possible, would there be any relationship between matter and energy or would they be completely separated? Would they fail to exist in such a place? Thank you for indulging my curiosity.

Mass is a thing of reality, while energy is an abstract concept of our description of nature, that reality does not need to care about.

the concept of energy arises conservation laws which are a consequence of symmetries, which again are arise from how we define time and space relative to natures laws. different definitions of the latter lead to different deductions of the former. Einsteins relativistic notion of space time (specifically his clocks) leads to the relation you mentioned, but if you were to use an absolute space time defined by a coordinate time and space and took the symmetries it is subject to, you get a coordinate energy unit with different relations.

energy is an extremely useful tool for the calculus, but it is not real in the same sense as mass, space, time or change, which all come with their own unique units expanding the degrees of freedom of the universe, while the deducted quantities like energy, (angular) momentum all have units assembled from those fundamental ones and describe the constrains of the world. 

Edited February 18 by Killtech

[md65536]

5 hours ago, swansont said:

E=mc^2 is not directly predicated on the existence of the electromagnetic interaction; c is the speed of any massless particle.

However, physics is inter-related. You can’t just arbitrarily change part of it and think that change would be isolated.

You should still be able to model a universe with an absence of light without removing the rules for it, such as a universe made up only of dark matter, or maybe including uncharged black holes. You'd have to make assumptions, but in accepted models, energy/mass equivalence holds for dark matter on its own.

[swansont]

36 minutes ago, md65536 said:

You should still be able to model a universe with an absence of light without removing the rules for it, such as a universe made up only of dark matter, or maybe including uncharged black holes. You'd have to make assumptions, but in accepted models, energy/mass equivalence holds for dark matter on its own.

We don’t think we know how the early universe would give us only dark matter, but if you skip over that, then yes, I agree with that. Not sure about black holes; I think Hawking radiation would lead to photons.

[MigL]

8 hours ago, Killtech said:

energy is an extremely useful tool for the calculus, but it is not real in the same sense as mass, 

The Sun converts 620 million tons of Hydrogen into 606 million tons of Helium each second ( from Wikipedia ).
The energy of the bound state of the Helium nucleus is manifested as a mass deficit or binding energy, totaling 14 million tons every second.
This 14 million ton mass deficit/binding energy eventually makes its way to the surface, where most of it is radiated into space as energetic radiation, and makes life possible on our planet.

Pretty darn amazing for something that is not real and only useful for calculations.
Actually the mass of the three quarks that make up nucleons ( protons and neutrons ) is only about 2% of the nucleon's mass. The rest is binding energy of the color interaction.
By your logic 98% of the 'mass' of a nucleon is not 'real'.

IOW energy is just as 'real' as mass.
We don't actually measure mass; we measure weight.
Mass is determined from energetic interactions, such as reaction to a field ( Earth's gravity being most obvious ), momentum conservation in collisions, etc.
This 14

Edited February 19 by MigL

[swansont]

Given that E=mc^2, I think that energy and mass are on equal footing. Both are abstractions; neither is real in the sense that they are properties rather than substances. The effects tied to them are quite real.

But it’s important to specify what one means by real. Real (actually there/happening) vs illusion, or real (physically exists) vs. abstraction? Energy and mass aren’t illusions.

[Eise]

19 hours ago, Genady said:

Moreover, it is not necessary for c to be a speed of anything. It is a coefficient in the spacetime metric

I would say even stronger: it is the factor needed to put space and time on the same footing. So to speak, the 'exchange rate between space and time'. This 'exchange rate' determines the causal structure of spacetime. It leads necessarily to the fact that there must be a maximum speed with which events can be causally related. Particles with mass can never reach this speed, as it would need an infinite source of energy. On the other side, massless particles can only travel at this speed. Thus the speed of light is not 'the speed of light': it is the speed of all massless particles. 

On 2/18/2024 at 7:59 AM, Silverstreak said:

However, I was curious about what would occur if there was a universe where light didn't exist. Assuming that's even possible, would there be any relationship between matter and energy or would they be completely separated?

So the answer is: if the causal structure of your alternative universe is the same as ours, then the same relationship holds.

Edited February 19 by Eise