Re: Olber's paradox: a poll


"funkenstein" <luke.saul@xxxxxxxxx> wrote in message
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On Aug 10, 1:59 am, "Androcles" <Headmas...@xxxxxxxxxxxxxxxxxx> wrote:
"funkenstein" <luke.s...@xxxxxxxxx> wrote in message

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On Aug 9, 1:47 pm, "Androcles" <Headmas...@xxxxxxxxxxxxxxxxxx> wrote:



"funkenstein" <luke.s...@xxxxxxxxx> wrote in message

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Just curious, what do you think is the real solution to Olber's
paradox?

a) finite "universe".. night sky is dark because if you were to go in
any direction eventually you'd pass all the light sources

b) fractal geometry of scale.. uneven distribution of light sources
means there will always be a void larger than the last

c) occultation.. dust and/or other types of light extinction.

d) other

Other. Light is a stream of photons like water coming from a shower
spray.
The further away the shower head, the less water will hit you. So even
though there is a shower head in every direction, you are lucky to get
even
one droplet of water from the furthest and even when you do you won't
notice it makes you wet.

The photons from a stellar shower head hit you with a flux inversely
proportional to the square of the distance from you to the shower
head.
=============================================
If you put a shower at the top of the Empire State Building and sprayed
5th
Avenue with it you'd get a flux (flow) inversely proportional to the
square
of the distance from you to the shower head. Pedestrians on 5th Avenue
or W 34th St. would hardly notice. Picture it in your mind.

Street level view: http://tinyurl.com/kua6z9
There is an ordinary bathroom shower head up there, spraying the street.
How wet will you get?
=============================================

However, the amount of shower heads in a given solid angle at
some distance from use increases proportionally to that distance
squared.
============================================
This is where you go wrong. All the buildings along 5th Avenue
and W 34th St. have differing heights, and you only get one shower
head per building. Stars are very distance from each other (light years)
and galaxies are millions of light years apart.
If New York is thought of as a galaxy and London is a galaxy,
there are no stars in mid-Atlantic, but we assume you can see London
from New York for this analogy.
The "solid angle" is 4pi steradians so you can include spray from the
top of Nelson's column in London (a different galaxy), but it won't
make New York very wet, even though 1 or 2 drops of water do
reach all the way across the Atlantic once in a while.
===============================================


OK, I'll put you down for choice B then, or 1/2 your vote to choice
B. That's my favorite as well, though I don't deny there may be a bit
of C and D taking place as well.



So, when you add up all the contributions from shower heads
at different distances from you, there is a constant contribution at
each distance, and an infinitude of distances, so we should be
soaked.
===============================================
We ARE soaked, by the CMBR.

Being slightly damp corresponds to the CMBR,
which Olbers didnt detect.

Good point.. the CMBR could be involved in another choice, possibly
in combination with extinction or attenuation.
=================================================
Olbers asked "Why is the night sky dark?"
That's an assumption, not a fact. The night sky is filled with light
in the form of the CMBR. If the mean distance between stars (call it
density) were less (density greater) then the CMBR would be brighter.
What you cannot do is extinguish or attenuate energy. If you are in
the shadow of an object that can absorb energy from a distant star
(say the Moon, for example) then the object will get hotter and radiate
its excess heat as it cools. That radiation IS the CMBR. So the Moon
reflects both heat and light from the Sun, and any energy it absorbs
when full is radiated away (at a lower frequency) when it is new.
Same is true for the Earth, all the energy we get during the day is
lost at night or the planet would heat up. If you pour energy into
a light bulb filament it gets white hot and radiates, lighting up
your living room or the road ahead. Stop putting the energy in and
it cools. Do the same with a thicker iron bar and you'll see it
glow red and then dull red as it cools. It will cool to its ambient
temperature. The ambient temperature of space is above absolute
zero, the temperature of the CMBR.
http://en.wikipedia.org/wiki/Color_temperature
Olbers made the mistake of assuming what he couldn't see with his
eyes didn't exist, and he could not see the CMBR.


OK lets see if I am understanding you right. The Lyman-Alpha emitted
photons don't make it to us because they are absorbed by dust (or
large bits of dust like the moon), and are re-emitted as infra-red and
microwave that we see as the CMBR. So one half of your vote goes
towards choice C?
==============================================
The Lyman series (along with the Balmer, Pfund, Paschen and Bracket
series) is only for hydrogen, the easiest to study. Every molecule, atom
or ion for every element will have a similar series, and all will be Doppler
shifted to some extent. As a consequence we obtain a continuous
spectrum. Any line-of-sight radiation makes it to us, including Lyman
alpha, the CMBR is BACKGROUND radiation.
You'll see it omnidirectionally; which was Olbers' complaint, he had
no way to detect it.
When radiation hits, it either reflects or it is absorbed and re-radiated
in a different direction. The secondary radiation can be the same Lyman
Alpha or it can be split into two or three less energetic photons emitted
at different times. The analogy for that is money. A quarter strikes,
a dime, two nickels and five cents are given off. Or it could be a quarter.
There isn't much dust to hit, though; if there were we'd be seeing a fog.
We already do with the day sky, dust motes in atmosphere reflect sunlight
and prevent us from seeing stars at noon. We can still see them in IR.

Olbers asked why the sky isn't bright. But it is. If we doubled the number
of stars in any given volume it would be twice as bright. As to voting,
Nature is not a democracy, she's a dictator and won't give a hoot for
your opinion or mine.


.

Relevant Pages

  • Re: Olbers paradox: a poll
    ... The further away the shower head, the less water will hit you. ... of the distance from you to the shower head. ... We ARE soaked, by the CMBR. ... What you cannot do is extinguish or attenuate energy. ...
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