Layman's question on Cosmic Microwave Background

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Discussion Overview

This discussion centers around the Cosmic Microwave Background (CMB), exploring its properties, interaction with matter, and its presence in everyday life. Participants inquire about the implications of the CMB being present in the universe and how it interacts with the human body and the Earth's atmosphere.

Discussion Character

  • Exploratory
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant notes that the CMB surrounds the body and penetrates slightly, suggesting it is harmless.
  • Another participant mentions the peak wavelength of the CMB is 1.1 millimeters and speculates that its shorter wavelength may mean it is less penetrating, implying that most solid or liquid materials would block it.
  • It is stated that the Earth's atmosphere does not effectively shield the CMB, as it was originally detected by ground-based antennas.
  • A participant highlights the CMB's temperature of approximately 2.7K, arguing that it would have no impact on the human body and that most of it is blocked by the atmosphere.
  • One participant estimates that there are about 400 million photons of CMB per cubic meter, suggesting that this is the number present in the human body at any moment.
  • Another participant questions how the number of CMB photons compares to sunlight photons per cubic meter.
  • It is mentioned that about 1% of RF static can be attributed to the CMB, with a comparison made to the number of photons emitted by a 100-watt light source, which is significantly higher than the number of CMB photons.
  • One participant adds that the CMB contains approximately 98% of all the light ever emitted in the universe, but notes that this light is spread over vast distances in space.

Areas of Agreement / Disagreement

Participants express differing views on the extent to which the CMB interacts with matter and the effectiveness of the atmosphere in blocking it. There is no consensus on the implications of the CMB's presence in relation to human health or its comparison to sunlight.

Contextual Notes

Some claims depend on assumptions about the interaction of radiation with matter and the definitions of terms like "blocking." The discussion includes unresolved comparisons between the CMB and other sources of photons.

FalkonJenova
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Hi everyone, I'm a lowly computer programmer who has been interested in the CMB lately and recently became curious about one thing...

As I understand it, the CMB is the left-over radiation from the Big Bang spread uniformly throughout the universe.

Does this mean that this radiation is also touching my body and everything I see right now?
Does the Earth's atmosphere somehow prevent it from reaching the surface?

If it is touching me, then does that also mean that the CMB is also occupying the empty space in my atoms?
Or does my body keep it out?

Thanks to anyone who sacrifices their time!
 
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FalkonJenova said:
Hi everyone, I'm a lowly computer programmer who has been interested in the CMB lately and recently became curious about one thing...

As I understand it, the CMB is the left-over radiation from the Big Bang spread uniformly throughout the universe.

Does this mean that this radiation is also touching my body and everything I see right now?
Does the Earth's atmosphere somehow prevent it from reaching the surface?

If it is touching me, then does that also mean that the CMB is also occupying the empty space in my atoms?
Or does my body keep it out?

Thanks to anyone who sacrifices their time!

Yes it surrounds your body and must go a little ways in. But it's harmless

The peak wavelength is 1.1 millimeter
http://en.wikipedia.org/wiki/Cosmic_microwave_background_radiation

Out of curiosity I looked at http://en.wikipedia.org/wiki/Microwave_oven and learned that CMB is 100 times higher frequency than microwave oven radiation. The shorter wavelength probably means it is less penetrating so I would imagine that most common liquid or solid material would block it. Your skin probably stops all but a tiny fraction of it.

But atmosphere is not a good shield. The CMB was originally detected by an antenna on the ground.
 
Last edited:
FalkonJenova said:
Hi everyone, I'm a lowly computer programmer who has been interested in the CMB lately and recently became curious about one thing...

As I understand it, the CMB is the left-over radiation from the Big Bang spread uniformly throughout the universe.

Does this mean that this radiation is also touching my body and everything I see right now?
Does the Earth's atmosphere somehow prevent it from reaching the surface?

If it is touching me, then does that also mean that the CMB is also occupying the empty space in my atoms?
Or does my body keep it out?

Thanks to anyone who sacrifices their time!
Just to reiterate Marcus' point, the temperature of the CMB is just 2.7K, or 2.7C above above absolute zero. So it basically would have no impact on your body. Also, the vast majority of it is blocked by our atmosphere anyway (this is why we have satellites to observe the CMB).
 
I believe I've seen a figure of 400 million photons of the CBMR per cubic meter.

So at a guess, you've got about that many in you at any moment.
 
alexg said:
I believe I've seen a figure of 400 million photons of the CBMR per cubic meter.

So at a guess, you've got about that many in you at any moment.

How does this compare to the number of photons of sunlight per cubic meter?
 
alexg said:
I believe I've seen a figure of 400 million photons of the CBMR per cubic meter.

So at a guess, you've got about that many in you at any moment.
Not quite, because as I mentioned above, most of those are blocked by the atmosphere!

But yes, in the older-style analog TV sets, some fraction of the static in the TV is due to CMB.
 
About 1% of RF static can be attributed to the CMB. It is stll pretty pathetic. To put this into perspective, a 100 watt light light source emits about 2.5E+20 photons per second - which is a lot more than 400 million [4E+08] photons.
 
Chronos said:
About 1% of RF static can be attributed to the CMB. It is stll pretty pathetic. To put this into perspective, a 100 watt light light source emits about 2.5E+20 photons per second - which is a lot more than 400 million [4E+08] photons.
Although to be fair to the CMB, it contains something like 98% of all the light ever emitted in the history of the universe. It's just that the universe is quite big now and that light is spread over the vast emptiness of space.
 

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