Register to reply

How much of the universe is in the form of electromagnetic radiation?

Share this thread:
BobiG
#1
Mar8-14, 11:49 AM
P: 8
Can you make an educated guess on the amount of energy in the universe in the form of electromagnetic radiation (photons), considering the vast amount of photons moving in every direction throughout the vast universe, there is literally no point in the universe that you can be in and not observe photons coming from every direction around you, meaning most of the vacuum of space has EMR moving through it. I'm guessing it should add up to a really significant portion of all the available energy in the universe? Also how much energy do you think a sun like ours looses in EMR throughout it's life time?
Phys.Org News Partner Physics news on Phys.org
Physicists unlock nature of high-temperature superconductivity
Serial time-encoded amplified microscopy for ultrafast imaging based on multi-wavelength laser
Measuring the smallest magnets: Physicists measured magnetic interactions between single electrons
UltrafastPED
#2
Mar8-14, 12:40 PM
Sci Advisor
Thanks
PF Gold
UltrafastPED's Avatar
P: 1,908
No, it is an insignificant amount in comparison to the energy content of the total mass content.

You can make a rough calculation from the peak energy of the cosmic background radiation (CMB), which represents the peak temperature (2.7 K) for a blackbody spectrum. For more on the CMB see:
http://abyss.uoregon.edu/~js/ast123/lectures/lec23.html

From the temperature you can calculate the energy of each photon, and then calculate the energy content per cubic meter of outer space from the density figures (~10^9 CMB photons per cubic meter).

Then compare it with the energy content of the particles in that same cubic meter - perhaps one hydrogen atom.

A good exercise in conversion of units of energy, and making physical estimates.
Vanadium 50
#3
Mar8-14, 04:15 PM
Mentor
Vanadium 50's Avatar
P: 16,169
It's been a very long time since the universe was radiation dominated - over 13 billion years.

dauto
#4
Mar8-14, 07:47 PM
Thanks
P: 1,948
How much of the universe is in the form of electromagnetic radiation?

Photons contain about 0.01% of the energy of the universe according to the most popular modern cosmological model - the Lambda-CDM. For comparison, regular matter (baryonic matter) contains about 5%, dark matter contains about 25%, and dark energy about 70%. Other models are possible but that one seems to be the front runner at least for now. At any rate, the fraction of the universe's energy in the photons is minimal.


Register to reply

Related Discussions
Heat is electromagnetic radiation OR heat is __spread by__ electromagnetic radiation? Classical Physics 2
Electromagnetic Induction vs. Electromagnetic Radiation Classical Physics 17
Electromagnetic radiation Classical Physics 3
Electromagnetic radiation Quantum Physics 14
Electromagnetic Radiation Physics Learning Materials 0