Could Dark Matter be mass in EM fields?

In summary, the conversation discusses the concept of mass and energy being interchangeable quantities according to Einstein's theory of relativity. It also questions whether electromagnetic waves, which transport energy, also transport mass and whether this could explain dark matter. However, it is clarified that while radiation does cause curvature of space-time, it is already accounted for in calculations and cannot fully explain dark matter. The conversation also touches on the energy density of electromagnetic fields and their significance in the overall energy budget of the galaxy.
  • #1
warwickphys
3
0
Didn't Einstein say that mass and energy were interchangeable quantities?

Electromagnetic waves transport energy - Does this therefore mean they also transport mass?

Could, therefore, all the radiation coming out of every decaying atom in the universe, every star and every accelerating charge (gaining kinetic energy) not cause some large scale gravitational effects that could explain dark matter?

I also thought that this could mean in places where different EM waves from different star systems happened to superimpose there could be greater mass. The amount of dark matter in a galaxy would be proportional to the number of stars in it then I suppose, and things like E=hf mean x-rays would be "heavier" etc...
 
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  • #2
12 views? someone say something! even if its just to point out why you think this is a stupid question.
 
  • #3
warwickphys said:
Didn't Einstein say that mass and energy were interchangeable quantities?

Relativity provides a unified theory for mass and energy as viewed by different observers, but that doesn't mean that E=Mc^2 is a blank cheque on interchanging mass and energy in any arbitrary way.

warwickphys said:
Electromagnetic waves transport energy - Does this therefore mean they also transport mass?
No.

warwickphys said:
Could, therefore, all the radiation coming out of every decaying atom in the universe, every star and every accelerating charge (gaining kinetic energy) not cause some large scale gravitational effects that could explain dark matter?

Radiation does gravitate in the sense that radiation causes curvature of space-time just like any other energy (where energy here includes all types of energy, including mass). However this effect is already included in calculations (and it almost always too small to be significant), so radiation cannot be dark matter.
 
  • #4
alright...i stand corrected...
 
  • #5
Electromagnetic energy is included in the considerations that imply dark matter.
 
  • #6
Yes, that is correct, EM fields are considered when addding up the energy budget. The energy density of EM fields is proportional to the square of the fields themselves, for a magnetic field, [tex]U=\frac{B^2}{2\mu}[/tex] and for an electric field the energy density is [tex]U=\frac{\epsilon E^2}{2}[/tex]. In the interstallar medium of the Milky Way and most other "normal" galaxies, the magnetic field strength is around [tex]1\mu G[/tex] i.e. really small, so it really is pretty insignificant. On large scales the galaxy is very neutral, so no electric fields are present.
 
  • #7
Impressive post AstroRoyale. You appear to be well informed.
 
  • #8
Well thank you!
 

What is dark matter?

Dark matter is a type of matter that cannot be directly observed because it does not emit or interact with electromagnetic radiation. Its existence is inferred from its gravitational effects on visible matter.

What are EM fields?

EM fields, or electromagnetic fields, are regions of space where electrically charged particles are affected by electric and magnetic forces. These fields are created by the movement of charged particles and can be found in a variety of forms, such as light, radio waves, and microwaves.

Could dark matter be mass in EM fields?

There are currently several theories that propose dark matter could be made up of particles that interact with EM fields. However, this is still a topic of ongoing research and has not been confirmed.

How is dark matter different from regular matter?

Dark matter and regular matter are fundamentally different in that dark matter does not interact with electromagnetic radiation, while regular matter does. This means that dark matter cannot be seen or detected using traditional methods of observation, unlike regular matter which can be seen with telescopes and other instruments.

Why is understanding dark matter important?

Understanding dark matter is important because it makes up about 85% of the total mass of the universe and plays a crucial role in the formation and structure of galaxies. By studying dark matter, scientists hope to gain a better understanding of the universe and its evolution.

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