Olbers' Paradox

**Martin_G** · Nov6-09, 11:27 AM

I understand Olbers' Paradox and its resolution, however such phrases as this - "If the universe extends infinitely, then eventually if we look out into the night sky, we should be able to see a star in any direction, even if the star is really far away" - which can be found here and also in at least one textbook, strike me as plain wrong. Even if there are infinitely many stars, there is no reason to expect that any infinite line from a point would hit at least one of them. This seems intuitively obvious. Am I missing something, or is that quote just a bad way of formulating the paradox?

**Chronos** · Nov7-09, 03:27 AM

Your interpretation is correct. In an infinitely old universe with an infinite number of stars, the night sky should be about as bright as the sun. That was Olber's point.

**russ_watters** · Nov7-09, 09:16 AM

Actually, chronos, the OP said just the opposite....

Martin_G, you can construct a function that calculates the probability of a line of sight landing on a star based on the density of stars in the universe and length of the sight line (age of the universe). As the length of the sight line (age of the universe) grows, the probability rises toward the limit of 1.

**unerkennbar** · Nov7-09, 03:13 PM

Olber's Paradox was conceived by Heinrich Wilhelm Matthäus Olbers
a german astronomer from the 18th century, who unfortunately lived
in an age of very limited scientific data, low technology and newtonian idealism.

the concept of the photon was not developed until more than a century later by Albert Einstein.
and even to this day no physicist can accurately explain exactly what a photon is or how it functions.
The charge limit of photons has only recently been calculated at 10^-33 e
which suggests that photons can have a very small negative or positive charge,
and opens the possibility of anti-photons and mutual annihilation due to photon/anti-photon collisions.

Olber was unaware of the existance of gravitational drag, Compton scattering,
the absorption and emission of photons by electrons,
the recently discovered Heliospheric shield which acts as a barrier to high energy stellar radiation, and so on..

The result of all this cosmic impedence is that light may very well have a finite range limit of propagation.
if photons have a mean maximum range of 13 x 10^9 LY for example, then all galaxies further than 13 x 10^9 LY would be invisible to earth astronomy, no matter how powerful our telescopes.

also, even in an infinite unbounded universe, stars are not eternal, they each have a limited lifespan,
and each will only emit light during that lifespan, and then their light stops.

the last photon emitted from a dying star 2 x 10^10 LY distant would never reach the earth
it would travel until it collides with a charged particle and is absorbed
or possibly annihilated by an anti-photon.

the sky is very likely dark for this reason.

**ideasrule** · Nov7-09, 07:40 PM

To unerkennbar: I'm sorry, but most of that is gibberish. The charge LIMIT on a photon has been measured. Note: the charge LIMIT. There is no reason whatsoever, empirical or theoretical, to suspect that a photon has non-zero charge. Even if it does, and if anti-photons exist, a collision between photons and anti-photons must necessarily produce two photons of the exact same frequency. If it doesn't, either energy or momentum won't be conserved.

The real reason that photons have a finite range is that the speed of light is finite, and photons from far-away galaxies haven't had a time to reach us yet since the universe came into existence.

Gravitational drag, Compton scattering, photon absorption/emission, and
the heliospheric shield are all irrelevant to Olber's paradox.

The only part of that post I agree with is this:

also, even in an infinite unbounded universe, stars are not eternal, they each have a limited lifespan,
and each will only emit light during that lifespan, and then their light stops.

which, BTW, is also irrelevant to Olber's paradox. I don't think people believed that stars were eternal in Olber's time, but it doesn't matter: a static, infinite, and eternal universe will be infinitely bright in all directions due to the light of the active stars.

**Phrak** · Nov7-09, 10:02 PM

Originally Posted by Martin_G

Even if there are infinitely many stars, there is no reason to expect that any infinite line from a point would hit at least one of them. This seems intuitively obvious. Am I missing something, or is that quote just a bad way of formulating the paradox?

You may think of it this way.

Assume stars are randomly distributed.

For any given point of observation, construct spherical shells out to infinity. Each spherical shell will block some small ratio of dark area, d along the radial direction to the point of the observer. d parts dark vs. (1-d) parts light.

You have to think in reverse, here, where we are blocking darkness instead of light. Each shell lets through (1-d) parts of the remaining darkness.

N shells let though (1-d)^N parts darkness.

How much darkness gets though as N goes to infinity?

Because the stars are randomly distributed, d is not constant. We may ignore those shells for which d is less than some given value, D. There are M shells for which d is over our critical value, D. But M also goes to infinity. So we get the same answer.

(1-d')^M → 0

d' is a finite random variable less than one and greater than D.

The upper bound of (1-d')^M is (1-D)^M. (1-D)^M = 0.

**unerkennbar** · Nov8-09, 02:30 PM

To unerkennbar: I'm sorry, but most of that is gibberish.

Hi,

I expect nothing less than skepticism regarding any suggestion of charged photons,
or anti-photons.. however I am not arguing the existance of such things,
whether or not photons have charge or not is irrelevant to the debate.

The point I am making here is that photon propagation may very likely have an absolute limit
due to known, or unkown processes.

A photon travelling thousands of millions of LY would be very fortunate indeed to make the journey to earth
unimpeded by countless objects of mass, from subatomic particles to planets.

Gravity does in fact deviate and modulate light,
electrons do absorb photons on contact, and re-emit them at another energy level
and with all original information lost.
these are well confirmed facts and not gibberish.

The discovery of an Heliospheric boundry shield against high energy radiation
suggests that only a percentage of all photons penetrate this shield.

It is much less difficult to accept that light has an absolute range limit,
than to accept that a photon is eternal and can travel an infinite distance at a constant energy level.

The standard model is based on the assumption that stellar redshift is due the doppler effect.
Hubble himself never conceived of the possibility of an alternate explaination for redshift.

Supporters of the standard model will invariably come to the rescue whenever alternate
theories of redshift are proposed, using equations as offensive weapons.

However mathematical models, no matter how cleverly calculated, are not a substitute for direct physical experimental evidence,
and to date there is no direct physical experimental evidence that space time is expanding, that a big bang creation event ever occured,
nor that dark matter exists.

These are all hypothetical constructs invented to support a "Creation Event Hypothesis".

I personally find the concept of a creation event quite absurd, suspiciously theological,
and absolutely un-neccessary when so many alternate explainations are possible.

Occam's razor states that the most simple explaination is the most likely.

in this case, the simplest explaination is that light has an absolute range limit,
and that redshift increases with distance due to gravity induced modulation
produced by all the objects of mass that photons encounter over vast distances.

**qraal** · Nov12-09, 09:55 PM

Originally Posted by unerkennbar

Hi,
The point I am making here is that photon propagation may very likely have an absolute limit
due to known, or unkown processes.

Well there's an unfounded, unexperimental and unobserved theoretical supposition being deployed to prop-up an unfounded, unobservable and purely metaphysical belief in an Infinitely old Universe.

Take your pick of "theologies" and worship at your preferred Temple of Being Right.

But to claim that the "Big Bang" is unphysical and based merely on maths is to stick one's head in the sand and ignore truckloads of data which point to a Universe that really is expanding from a common origin. Wishing for imaginary physics to make a "creation event" go away is a bigger act of faith than reasonably extending known, proven physical laws back a few billion years. Believing, for no physical reason at all, in an infinite Time and Space is much akin to devout Hindus who imagine modifications to radioactive decay laws so the Earth can be trillions of years old, as affirmed in their Scriptures.

Who is making the bigger leap? Those who think the Universe is finite in space and time, or those who want to believe neither? In an Infinite Universe anything is possible, including an unimaginably complex uncreated Creator who happens to be embarassing to one's theology or lack thereof.

NB I hope I haven't broken the no religious discussion rule too much. But he started it!

**unerkennbar** · Nov17-09, 08:30 PM

Well there's an unfounded, unexperimental and unobserved theoretical supposition
being deployed to prop-up an unfounded, unobservable and purely metaphysical belief
in an Infinitely old Universe.

Take your pick of "theologies" and worship at your preferred Temple of Being Right.

Dark Matter is a perfect example of an unfounded, unexperimental and unobserved theoretical supposition
being deployed to prop-up an unfounded, unobservable theory of a creation event.

Theology is the perfect term for the Creationist "Big Bang" Theory.
a theory conceived by a catholic priest no less.

mathematical modelling is not a substitute for direct experiment and common sense.

observing light from extremely distant stars from a planet based telescope
that is simultaneously rotating on it's axis, orbiting a sun,
which in turn is orbiting the galactic centre of the milky way,

is exactly like attempting to take a sharp image of a needle,
whilst riding a spinning horse on a rotating carousel with a long exposure camera.

you will get nothing but motion blur and image distortion.
and yet this awkward fact is never even mentioned in astronomy.

it's nice to fantasize about imaginary theories,
however science is not about clever mathematics, it's about seeking truth
through direct observation and experiment, guided by logic and common sense.

Theology has no place in science.

the best logical explanation for stellar redshift which increases with distance,
is that light encounters ever increasing amounts of matter (mass) and therefore
ever increasing amounts of gravity the further it travels.

furthermore, space is not a vacuum, there is in fact "no such thing"
as a perfect vacuum in nature. space is 99% plasma,
and photons are everywhere effected by this plasma.

**DaveC426913** · Nov17-09, 08:38 PM

Originally Posted by unerkennbar

Dark Matter is a perfect example of an unfounded, unexperimental and unobserved theoretical supposition
being deployed to prop-up an unfounded, unobservable theory of a creation event.

It has been observed.

Originally Posted by unerkennbar

Theology is the perfect term for the Creationist "Big Bang" Theory.
a theory conceived by a catholic priest no less.

Ad hominem attack.

Originally Posted by unerkennbar

mathematical modelling is not a substitute for direct experiment and common sense.

Common sense. Right. So you have experienced Big Bangs and infinite universes before, and are drawing on that previous experience then.

Originally Posted by unerkennbar

observing light from extremely distant stars from a planet based telescope
that is simultaneously rotating on it's axis, orbiting a sun,
which in turn is orbiting the galactic centre of the milky way,

is exactly like attempting to take a sharp image of a needle,
whilst riding a spinning hourse on a rotating carousel with a long exposure camera.

you will get nothing but motion blur and image distortion.
and yet this awkward fact is never even mentioned in astronomy.

OK, I got nothin' for this one. It's just ignorant. That what your "common sense" gets you.

It is clear that you have never studied the first thing about astronomy or you would have answers to the things you suppose.

Originally Posted by unerkennbar

it's nice to fantasize about imaginary theories,
however science is not about clever mathematics, it's about seeking truth
through direct observation and experiment, guided by logic and common sense.

How many dark matter clusters have you experienced such that your common sense tells you how they work?

unerkennbar, it may not be obvious to you, but your ignorance of the subjects you try to discuss is completely transparent to the rest of us.

Also, attention to grammar and punctuation is a required practice on PF. Please give it some attention. This is not a chatroom.

**unerkennbar** · Nov17-09, 09:01 PM

"Facts and truth really don't have much to do with each other. " - William Faulkner

It has been observed.

It has not been observed directly, only effects have been observed,
this is not proof that the effects are caused by dark matter, since dark matter has never been physically detected.

Ad hominem attack.

refering to Monsignor Georges Henri Joseph Édouard Lemaître as a catholic priest
is not an Ad Hominem attack, he was, in fact, a Belgien catholic priest,
and stating a man's profession should not be perceived as a personal attack.

it is only in responce to the ironic Theology reference in the previous reply.

Common sense. Right. So you have experienced Big Bangs and infinite universes before, and are drawing on that previous experience then.

you have experienced Big Bangs?

no one has experienced a cosmic Big Bang,
however we experience an infinite universe constantly.

OK, I got nothin' for this one. It's just ignorant. That what your "common sense" gets you.

common sense is the most valuable sense human beings possess.
a sense that is blatently missing from mainstream thinking.

How many dark matter clusters have you experienced such that your common sense tells you how they work?

Dark Matter has never been observed in nature, it exists only in theory.

unerkennbar, it may not be obvious to you, but your ignorance of the subjects you try to discuss is completely transparent to the rest of us.

yet another personal attack,
a common symptom of emotional stress, due to one's idiology being threatened.

such name calling, personal attacks and rudeness are unacceptable,
especially from a scientist.

this is a strategy used by conservative politicians to discredit political opponents,
and typically an act of desperation which is ultimately self-discrediting.

if you have no idea to whome you are speaking,
nor what knowledge and experience a person has on a subject,
it is unwise to accuse them of being ignorant.

Also, attention to grammar and punctuation is a required practice on PF. Please give it some attention. This is not a chatroom.

Entschuldigung, aber Englisch ist nicht meine Muttersprache.

Politeness and objectivity would be better PF requirements.

it's incredible how quick mainstream science supporters are
to point out spelling, grammar and punctuation errors, rather than argue facts
when anyone dares to challenge their beloved standard model.

In any case, I have made my point here, good science must examine every possibility
and make every effort to limit conclusions and theories to the most simple explanations.

**ideasrule** · Nov18-09, 01:23 AM

Originally Posted by unerkennbar

No, it hasn't

I suppose you've never heard about galaxy rotation curves (which lead to the idea of dark matter in the first place), critical density calculations that show matter is "missing", gravitational lensing by unseen matter in the Bullet Cluster, the CMB power spectrum, etc?

you have experienced Big Bangs?

no one has experienced a cosmic Big Bang,
however we experience an infinite universe constantly.

Nobody has experienced these things, which is why mathematical modelling is necessary. It's certainly better than using gut instincts or plain guessing.

In any case, I have made my point here, good science must examine every possibility
and make every effort to limit conclusions and theories to the most simple explanations.

And that has happened. You know how many competing theories there were for the formation of the universe? There was static steady-state, steady-state but expanding, the de Sitter universe, Dirac's model of weakening gravity...eventually, the discovery of the CMB and mathematical inconsistencies in some of the models made the Big Bang the only credible theory.

Same with dark matter. A lot of possibilities were considered: inaccuracies in our theory of gravity was one of them. Even for scientists who assumed dark matter existed, there was a variety to choose from: cold dark matter, hot (relativistic) dark matter, MACHOs, etc. There were observation campaigns and simulations that eventually ruled out MACHOs as being insufficiently massive and hot dark matter as being too energetic, but a lot of alternatives were certainly considered. The cold dark matter model is the result of limiting conclusions and theories to the simplest explanations.

**DaveC426913** · Nov18-09, 10:15 AM

Originally Posted by unerkennbar

any and all replies containing emotional outbursts, rudeness, insulting remarks
or any form of personal attacks will be ignored, as if they were never posted.

Your behaviour has improved. That's a good sign. If you keep it untrollish, this thread may not get locked.

**unerkennbar** · Nov18-09, 11:01 AM

as long as this thread remains polite, objective and focused
on the scientific argument of Olber's paradox, there should be no problems.

**qraal** · Nov18-09, 06:37 PM

Originally Posted by unerkennbar

Observing light from extremely distant stars from a planet based telescope
that is simultaneously rotating on it's axis, orbiting a sun,
which in turn is orbiting the galactic centre of the milky way,

is exactly like attempting to take a sharp image of a needle,
whilst riding a spinning horse on a rotating carousel with a long exposure camera.

you will get nothing but motion blur and image distortion.
and yet this awkward fact is never even mentioned in astronomy.

the best logical explanation for stellar redshift which increases with distance,
is that light encounters ever increasing amounts of matter (mass) and therefore
ever increasing amounts of gravity the further it travels.

furthermore, space is not a vacuum, there is in fact "no such thing"
as a perfect vacuum in nature. space is 99% plasma,
and photons are everywhere effected by this plasma.

You're only parading your ignorance of the science involved. Please do some real (scholastic) research on the topic and educate yourself out of the rhetoric. It's obvious you've read a very restricted range of books on the topics, books written from a tendentious perspective on a topic currently banned here on the board. Educate yourself and abandon the hollow posturing that such diatribes inflate one's mind with.

**DaveC426913** · Nov18-09, 07:24 PM

Originally Posted by unerkennbar

as long as this thread remains polite, objective and focused
on the scientific argument of Olber's paradox, there should be no problems.

It will also have to remain knowledgeable.

The difficulty you're encountering is that your attitude does not mirror your knowledge. grall said it best:

Educate yourself and abandon the hollow posturing that such diatribes inflate one's mind with.

We're happy to discuss. But there is no discussion as long as you think you have all the answers. You don't.