# How many photons/cm3?

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I don't explain the concept clealy i am afraid.

take a random point A in space.

From point A you can look at Alpha Centauri: it means that at least one photon from Alpha Centauri reached point A.

From the same point A you can look at Galaxy NGC1365: it means that at least one photon from NGC1365 reached point A.

and you can continue

From the same point A you can look at Galaxy NGC6872: it means that at least one photon from NGC6872 reached point A.

All those photon overlap each other.

And continue this way with all the galaxies of the observable universe. All these are sending at least one photon to point A.

That makes a lot of photons simultanately at point A.

Billions and billions.

Edited by michel123456

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Yes, and that light is quite dim. The total power of the light, i.e. the intensity, is proportional to the number of photons arriving each second, and the wavelength. Your explanation if the problem was adequate.

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There is one interesting idea that can be developed from this:

The universe must be finite in phsyical or temporal extent or there must be something very odd about our bit of it.

Since the universe is "only" about 14 billion years old, you only have to consider photons from stars within 14Bn light years.

Also, the inverse square law means that most of the more distant stars don't provide us with many photons.

So, there really are not many photons.

It is the equivalent of star light on a moonless night. That's pretty dark.

Edited by John Cuthber
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There is one interesting idea that can be developed from this:

The universe must be finite in phsyical or temporal extent or there must be something very odd about our bit of it.

That's very easy.

Light that travels through entire galaxy and entire Universe is colliding with other particles (absorbed photons), and other photons from time to time, photons with higher energy are produced.

At the end two gamma photons collide and regular matter in intersection of them appears.

I believe in so that in areas between galaxies there are born new clouds of hydrogen, which will with time build new stars and new galaxies. We don't see them yet, they didn't start emitting light.

Edited by Przemyslaw.Gruchala
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Moderator Note

Przemysla.Gruchala,

Please do not hijack threads with nonsense. Stick to the topic and please try and stay within the realms of accepted science.

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Electron-positron pair production is non-sense?!

since when?

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

If two gamma with enough energy collides and produces electron-positron,

it's possible the higher energetic two gamma photons can produce proton and antiproton the same way.

Swansont said that the biggest gamma photon detected has 3.5 TeV

http://www.eurekaler...u-pfe120905.php

this gamma photon has 6,849,341 more energy than gamma photon needed to produce electron-positron.

In future lab we need to produce such gamma photon and try to collide with other such gamma photon.

michel123456, do you think too that I am writing non-sense and hijacking your thread?

If so, I wont write anything else.

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Moderator Note

Przemyslaw.Gruchala,

'Heavier photons' constitute nonsense. And the second portion of your post is pure speculation - i.e. not something that belongs in a thread in the mainstream science forums. If you wish to discuss this, please report the mod note and staff will have a look at it.

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Photons scattering and creating matter/antimatter pairs doesn't address Olber's paradox. The antimatter eventually annihilates — it does not create clouds of invisible hydrogen.

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Mine point was such that because photons are absorbed in path between original source like f.e. star in galaxy billion light years far from here, we detect less photons from far star, than our own Sun.

The farther the more chance that it will be absorbed.

The antimatter eventually annihilates — it does not create clouds of invisible hydrogen.

And annihilation is production of photons, which eventually can again produce pair + - particles.

And again eventually annihilate (or fly in opposite directions), and do it infinitely.

In "infinite" time there is possible everything.

I was thinking more about higher energetic gamma photons.

Two colliding 3.5 TeV gamma photons should be able to produce 1836*2 protons and 1836*2 antiprotons.

Edited by Przemyslaw.Gruchala

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