Could light explain dark energy?

In summary, the momentum of light would not explain the effect known as "dark energy". There are other factors involved that are not well-known or accounted for.
  • #1
FrodeM
1
0
Could the momentum of light explain the effect known as "dark energy"? I know the distances between galaxies are wast, but so are the surface areas of galaxies, as well as all the stars emitting the light. Would be interesting to see a calculation of the fate of the universe if this was true, perhaps gravity would pull everything together again after the stars burnt out, and we'd have a cycle of big bangs. Any thoughts?
 
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  • #2
Could the momentum of light explain the effect known as "dark energy"?
No. Energy and momentum of light in the universe are well-known (because we can see it) and they are a small positive (=attractive) contribution to the total energy-density.

Please note that we don't allow wild speculations beyond actual physics here.
 
  • #3
Most of the light energy in the universe is actually contained within the CMBR, and not from the light radiated by the stars! Even then, the CMBR accounts for only a tiny fraction of the total energy density of the universe today. Also, as mfb stated, this effect is well accounted for and would produce a deceleration in the expansion of the universe, not an acceleration.
 
  • #4
Matterwave said:
the CMBR accounts for only a tiny fraction of the total energy density of the universe today.
Do you have a number for this?
 
  • #5
[itex][/itex]the energy-density today can be calculated. Here is one method of estimating the energy-density today, though the paper calculates the energy density of photons as well as radiation

http://astro.dur.ac.uk/~csf/level1/Cosmich/lecture_7-8_notes.pdf

this paper has roughly the same energy-density for photons.

[tex]\Omega_\gamma\approx5*10^{-5}[/tex]
variations occur in rounding, method used etc.

http://iopscience.iop.org/1742-6596/354/1/012009/pdf/1742-6596_354_1_012009.pdf

I've read numerous textbooks, articles etc that all have variations in the energy-density, though they are all close the the value I posted
 
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  • #6
Bill_K said:
Do you have a number for this?

Mordred provided them. :)

His number is the one I'm familiar with. If you wanted actual numbers with actual units, using ##\rho_{crit}\approx\rho_0=9\times 10^{-10}J/m^3## we get ##\rho_\gamma\approx 5\times 10^{-14}J/m^3##
 
  • #7
From the cosmic energy inventory:
10-4.3 or 5*10-5 for CMB
10-5.8 or 1.5*10-6 for "optical" light, and just a bit more for non-CMB light in general
Those numbers are relative to the critical density, where dark matter has ~.23 and dark energy ~.72.
 

1. What is dark energy?

Dark energy is a theoretical form of energy that is thought to make up around 70% of the entire universe. It is believed to be responsible for the accelerated expansion of the universe.

2. How does light relate to dark energy?

Light and dark energy are not directly related. However, some theories suggest that dark energy may be caused by fluctuations in the energy of empty space, which could potentially manifest as light.

3. Can light explain dark energy?

While there are some theories that suggest a possible connection between light and dark energy, there is currently no conclusive evidence to support this idea. More research and evidence is needed to determine if light could fully explain dark energy.

4. How does dark energy affect the universe?

Dark energy is believed to be the driving force behind the expansion of the universe. It is thought to counteract the gravitational pull of matter, causing the expansion of the universe to accelerate.

5. What are some current studies or experiments about light and dark energy?

There are ongoing studies and experiments, such as the Dark Energy Survey and the Large Synoptic Survey Telescope, that are searching for more evidence and information about dark energy and its possible connection to light. These studies use observations of distant galaxies and other astronomical data to further our understanding of dark energy and its effects on the universe.

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