Dark Energy v. The Void: What if Copernicus was Wrong?

September 26, 2008

Dark energy is at the heart of one of the greatest mysteries of modern physics, but it may be nothing more than an illusion, according physicists at Oxford University. The problem facing astrophysicists is that they have to explain why the universe appears to be expanding at an ever increasing rate. The most popular explanation is that some sort of force is pushing the accelerating the universe's expansion. That force is generally attributed to a mysterious dark energy.

Although dark energy may seem a bit contrived to some, the Oxford theorists are proposing an even more outrageous alternative. They point out that it's possible that we simply live in a very special place in the universe - specifically, we're in a huge void where the density of matter is particularly low. The suggestion flies in the face of the Copernican Principle, which is one of the most useful and widely held tenants in physics.

Copernicus was among the first scientists to argue that we're not in a special place in the universe, and that any theory that suggests that we're special is most likely wrong. The principle led directly to the replacement of the Earth-centered concept of the solar system with the more elegant sun-centered model.

Dark energy may seem like a stretch, but it's consistent with the venerable Copernican Principle. The proposal that we live in a special place in the universe, on the other hand, is likely to shock many scientists. The maverick physicists at Oxford conclude their paper by pointing out that forthcoming tests of the Copernican principle should help us sort out the mystery in the next few years.

Citation: Timothy Clifton, Pedro G. Ferreira, and Kate Land, Physical Review Letters (Phys. Rev. Lett. 101, 131302 (2008))

Source: American Physical Society

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superhuman
4.2 / 5 (11) Sep 26, 2008
It wouldn't violate the Copernican Principle if there were other such "huge voids where the density of matter is particularly low" in other parts of the Universe which are not yet detected.

It is also not explained why it would solve the problem - light which climbs out of gravity well on its way is perceived by an observer outside of the well as red-shifted. Light which descends into gravity well is blue-shifted for observer in the well.
stuflecknoe
3.6 / 5 (10) Sep 26, 2008
Its not unimaginable that there are other entities far beyond the known universe providing balance in terms of mass and energy to the equation.
JerryPark
1.8 / 5 (24) Sep 26, 2008
The more we seek to find earth like worlds, the more it seems that sol type solar systems and earth type worlds are rare. It is not unreasonable to suppose that we reside in an atypical section of the universe.
Modernmystic
1.6 / 5 (19) Sep 26, 2008
Well Copernicus was a smart guy, but he is a far cry from an infallible God.

With recent observations of most solar systems being VERY different from our own this wouldn't surprise me. Moreover, it wouldn't surprise me if more and more we find that this principle isn't all it's cracked up to be.
Velanarris
2.4 / 5 (8) Sep 26, 2008
The new observations on the Universe are pretty interesting. For instance, the size of the super cluster (name escaping me at the moment) which was heralded as the largest visible galaxy cluster now appears to be possible 10-20x larger than we thought simply because we can't see far enough to view the entire object.

Imagine if that was more of a "center" if you will where matter exists and we've just been spun off of that, much like a celestial satelite reaching obital escape velocity and being spun off into space.
whatastupidarticle
4.8 / 5 (13) Sep 26, 2008
'tenet', not 'tenant'. the universe is not renting space to the Copernican principle.
kkendall
2.8 / 5 (5) Sep 26, 2008
I've speculated on something like that. Imagine the universe so vast that we when we would be in some sort of a wave, like a wave of water, or a splash. That the universe is constantly flowing and that we are in just one tiny part of that flow. Flow is chaotic on a small scale, so we could just be (with our visible universe) in a part of the vast universe....A part that is expanding with an increasing rate. But because of the flowing universe, this could change.
Just a speculating away :)

Also, we could be a computer simulation. Imagine computers can take on (now) unimaginable quantities of data in the future, or some sort of other entity, species, or whatever.
So much, that it can run the whole visible universe, including us and everything else in it, in one big simulation. Enter the parameters of an ever increasing expansion of the visible universe, et voilá, you get what you see now.
D666
3.7 / 5 (9) Sep 26, 2008
Also, we could be a computer simulation. Imagine computers can take on (now) unimaginable quantities of data in the future, or some sort of other entity, species, or whatever.

Or Philip Jose Farmer could be right and we are living in a cosmic "terrarium", constructed by a not-very-benevolent race for their own amusement. Everything beyond Pluto is just a hologram....
Minnaloushe
3.6 / 5 (13) Sep 26, 2008
D666 is an escapee from the Outer Realms and is not to be trusted. Move along. Nothing to see here.

Sincerely,
The Projectionist
Modernmystic
3.4 / 5 (10) Sep 26, 2008
Read a book once I think was called "Cradle" in which hyper advanced alien civilizations artificially lowered the speed of light around our solar system to keep us in our "cradle" until we were advanced enough to not be dangerous to the rest of the galactic community. They also filtered the incoming EM radiation to keep us "in the dark" about certain realities beyond our little rock.
h1ghj3sus
1.7 / 5 (13) Sep 26, 2008
People make up things like dark voids. Why would a void be dark (useless theories imo)? Every position in the universe is similar in most aspects (Natural Laws / Forces). However, there are unique sets of laws and forces existent at one location at a given time which have a unique effect within that setting. But unique is a man-made definition in relation to one's experience. Our experience may be unique, and simultaneously non-unique for one who is older and/or experienced more (places & times). Unique is different for a baby, teenager, adult, elder, old-tree, earth, solar system, galaxy, and universe. Odds are that there is nothing unique within the universe because of its age and size.

If we are surrounded by fields of magnetism and electricity, and these fields alter the speed of electromagnetic waves (light being one):

Then all of our assumptions as to the distances and speeds of objects existing in our line of sight are most likely inaccurate.

I suspect that objects in interstellar medium accelerate and decelerate throughout time; and these events are directly related to the object's position within the said field(s).

Anyway, I have discovered free energy. Give it two more years unless I decide to make a post on youtube, giving it away.
x646d63
5 / 5 (6) Sep 26, 2008
Anyway, I have discovered free energy. Give it two more years unless I decide to make a post on youtube, giving it away.


All energy is free, it only costs money to package it for use. I have never once been charged to burn calories.
thales
3 / 5 (2) Sep 26, 2008
This seems appropriate to the conversation:

How To Live In A Simulation
http://hanson.gmu...sim.html
holmstar
3 / 5 (2) Sep 26, 2008
The fact that quantum properties are not well defined until a particle is observed would fit in well with the universe being a simulation...

Simulating trillions upon trillions of particles would probably be too computationally intense, so they instead only simulate particles that are actually being obseved. Everything else can be fudged to an extent. However, the human population is increasing, and looking more deeply into the detail of the universe. This means that more of the universe is being observed, and the computers running the simulation becoming overloaded. Because of this, the scope of the simulation must be reduced by expanding the universe such that more and more of it becomes unobservable over time.
CWFlink
3 / 5 (2) Sep 26, 2008
How much acceleration does the force of starlight from billions of stars cause over the course of billions of years?

When they question why the universe is expanding, do cosmologists take this into account?
deatopmg
1.8 / 5 (4) Sep 26, 2008
a question never answered to my satisfaction is; how does one manage to get a doppler (red/blue) shift w/ light if the speed is constant (relative to our frame of ref.) everywhere? is it?
The red/blue shift may be due to other things,e,g see Halton Arp.
E_L_Earnhardt
1.7 / 5 (6) Sep 26, 2008
If I believed there was no inteligence managing all of this I would not bother trying to understand using logic.
thales
4.3 / 5 (6) Sep 26, 2008
If I believed there was no inteligence managing all of this I would not bother trying to understand using logic.


Then you are unique.
Minnaloushe
3.4 / 5 (5) Sep 26, 2008
How much acceleration does the force of starlight from billions of stars cause over the course of billions of years?

When they question why the universe is expanding, do cosmologists take this into account?


An interesting exercise, but certainly negligible since 1) one limitation is the good old inverse square law and 2) any such effect probably nets to a metastable zero since photons are coming in from all directions.

Then again, when I cut on my new halogen light fixture, the illumination threw me to the ground....
PaulLove
3.4 / 5 (9) Sep 26, 2008
It seems to me that there is certainly something we don't understand as quite obviously the Universe is not moving as we would predict. When I hear someone describing dark matter and dark energy to force an explanation for why the modles they have really are correct I laugh. Universe is not behaving according to thier models so they add a correction factor, might as well says its angels and devils pushing the lights through the sky. Go there find out whats not working and fix your model instead of insisting on the model and inventing a solution for it.

Copernicus may have championed the idea that we are not special but it would be an equal mistake to assume that everywhere is the same. Stand on the east side of your home and compare the conditions the west side of your home, sunlight, wind, moisture sounds may all be different even though neither is "special". However if the only place you have ever been is on the side of your home away from the prevailing wind or on the shady side of your home there are somethings you just simply won't understand.
TheWalrus
3.8 / 5 (4) Sep 26, 2008
@deatopmg:

The red/blue shift is caused by the frequency of light changing as you approach or recede from the source. It really is like the Doppler effect. The Doppler effect doesn't change the speed of sound, only its frequency. Same with the red/blue shift.
TheWalrus
4 / 5 (4) Sep 26, 2008
@ PaulLove:

I think you have it backwards. They have observed the accelerating expansion. Assuming the observations are correct, there must be some energy causing the acceleration. Dark energy is not an attempt to cling to a flawed model--it's a new model. As for dark matter, what more evidence do you need? It causes gravitational lensing, fer Pete's sake.

Now for my crackpot theory: Imagine a planet covered with water. A large meteorite hits the north pole and sends a circular wave racing to the south, expanding as it goes. As the wave crosses the equator, its diameter decreases. Unless, that is, you measure the diameter across the north pole. In that case, the diameter starts to increase more rapidly than when it was north of the equator. In this analogy, the universe is everything inside the wave, and the planet is curved spacetime. Just don't think about what happens when the wave reaches the south pole...
OregonWind
2 / 5 (3) Sep 26, 2008
The problem would move from having to explain the very strange Dark Energy to having to explain why we live in a special place where the density of matter is lower that the rest of the Universe. I think that, possibly, those scientists just ran out of patience and now they want to change the face of the mystery.
neurogalactus
4.2 / 5 (6) Sep 26, 2008
The more we seek to find earth like worlds, the more it seems that sol type solar systems and earth type worlds are rare. It is not unreasonable to suppose that we reside in an atypical section of the universe.


Man, where did you learn this? During Sunday mass in church? Could you back your opinions with quotes?
For one, Sol-type suns (G) are quite common: the closest neighbor to our sun, Alpha Centauri, is a binary system, both components Sun-like (one G-type, the other K-type). Also Epsilon Eridani, Tau Ceti and 82 Eridani are sun-like. In our very Galaxy there are a few billion such stars. Therefore they are quite COMMON.

Secondly, NO-ONE (except you, probably) knows at the moment whether Earth-like planets are rare or commonplace. That's just because we don't have a sufficiently advanced observation technology yet to even detect those comparatively tiny worlds. Fortunately, required tech level should be attained within next 5-10 years (TPF, Darwin, optic comb & other projects).

I suggest that all pessimists first do some simple research before posting. FYI: Actually, astronomers were quite surprised to find so many planets thus far, some in environments never suspected to be capable of harboring them.
ArtyNouveau
1 / 5 (7) Sep 26, 2008
Everything in nature has a resonant frequency. The Universe is ringing like a bell. We are observing it at just beyond 270 degrees of cycle where it is expanding exponentially. In time, the expansion will appear linear and after that, It will appear to contract exponentially until it reaches zero degrees of cycle. Then it will start all over again but with less amplitude than before. Think about it!
paulthebassguy
1 / 5 (4) Sep 27, 2008
It is always interesting to hear theories like this. Personally though, until we have enough information to actually prove anything, I think that the dark matter theory is still the best one.
TheWalrus
not rated yet Sep 27, 2008
paulthebassguy--

I think you mean dark energy. And, yeah, I don't know nearly enough to scoff at the astrophysicists. It's fun to come up with new theories, but if soemone ain't got the math and the credentials, I ain't takin' 'em seriously.
superhuman
2 / 5 (3) Sep 27, 2008
@deatopmg:

The red/blue shift is caused by the frequency of light changing as you approach or recede from the source. It really is like the Doppler effect. The Doppler effect doesn't change the speed of sound, only its frequency. Same with the red/blue shift.


It can also be caused by gravity:
http://en.wikiped...redshift
frajo
1.7 / 5 (3) Sep 27, 2008
@ PaulLove:

They have observed the accelerating expansion.

Really? They have observed some special behavior of the SN type Ia data. SN type Ia data serve as distance indicators.
Nothing more. No questions whether SN Ia are fully understood. They admit not knowing too much about black holes, but they are so sure about SNs that they postulate (dark matter) particles that even the particle physicists don't know of.

I'd prefer to stick to occam's razor.

As for dark matter, what more evidence do you need? It causes gravitational lensing

Matter causes gravitational lensing. If there is not enough visible matter out there to explain galactic rotation patterns or gravitational lensing - well, there are more riddles to solve concerning gravity. Let's admit we don't understand gravity on long distance scales. It's a hierarchy problem, not a particle problem.
superhuman
2.3 / 5 (3) Sep 27, 2008
How much acceleration does the force of starlight from billions of stars cause over the course of billions of years?

When they question why the universe is expanding, do cosmologists take this into account?


Yeah I've been thinking about it also, it is most likely take it into account.

Interesting thing is that starlight produces both "dark matter like" effects and "dark energy like" effects - photons carry momentum and they also posses energy which is a source of gravity, so if you have countless photons crossing the galaxy they produce significant gravitational attraction and they also exert force on objects which absorb them by transferring momentum to them.

However both effects are probably small on cosmic scales.

For example such "dark matter effect" of starlight produced by one star during its lifetime can be thought of as spreading of the gravity associated with the mass-energy of all the radiation produced by the star. The source of that radiation is the star mass which is converted to energy during nuclear fusion reactions. So due to conservation of energy all the gravity produced by starlight of one star during its lifetime would have to be at most equal to the gravity of the mass which was converted to radiation energy - and that mass is equal to mass loss of the star during its lifetime (ignoring wind).

I was looking for the exact amount of mass that a typical star loses during its lifetime but so far without results. Certainly though it is a small fraction of star's mass as most of the mass-energy and therefore gravity stays in the original star until its end.
If I will have more time someday I might try to calculate it as I find it quite interesting.

Any "dark energy" effects of starlight would also need to subtract mass-energy from stars which produce the starlight.

So while both effects certainly exist they are way to small when we consider that according to current models dark energy constitutes a whooping 74% of mass-energy of known Universe and dark matter 22% with only 4% left for visible matter!
It means that even if ALL visible matter was converted into radiation it would be nowhere near enough to exert such dark matter and dark energy effects.
deatopmg
1 / 5 (3) Sep 27, 2008
@The Walrus
@deatopmg:

The red/blue shift is caused by the frequency of light changing as you approach or recede from the source. It really is like the Doppler effect. The Doppler effect doesn't change the speed of sound, only its frequency. Same with the red/blue shift.


I get that w/ sound where we are intercepting more or less waves in a given time. BUT if the speed of light is constant and I'm on an object traveling away from a monchromatic light beam, say blue, at a large fraction of C, the blue light beam still passes me at C, independent of my speed, so the frequency cannot down shift to red because the wavelets pass me unchanged at the same speed C. If it does (and we "know" it red shifts) then SR and GR must be out the window.
Soylent
5 / 5 (2) Sep 28, 2008
" BUT if the speed of light is constant and I'm on an object traveling away from a monchromatic light beam, say blue, at a large fraction of C, the blue light beam still passes me at C, independent of my speed, so the frequency cannot down shift to red because the wavelets pass me unchanged at the same speed C. If it does (and we "know" it red shifts) then SR and GR must be out the window."

Hogwash.

We know that light travels at a constant speed c in vacuum and we know that there is doppler-shift.

The fact that doppler shift is observed is strong evidence for the validity of SR; we would be at a loss to explain relativistic doppler-shift if there was no time-dilation between the frame of the source and the frame of the observer.
superhuman
5 / 5 (1) Sep 28, 2008
I get that w/ sound where we are intercepting more or less waves in a given time. BUT if the speed of light is constant and I'm on an object traveling away from a monchromatic light beam, say blue, at a large fraction of C, the blue light beam still passes me at C, independent of my speed, so the frequency cannot down shift to red because the wavelets pass me unchanged at the same speed C. If it does (and we "know" it red shifts) then SR and GR must be out the window.

The effect for light is present in both nonrelativistic and relativistic case.

In nonrelativistic case the time the light takes to pass the distance the source moved away from you during one cycle has to be added to the period.
In relativistic case in addition to the above time dilation also has to be taken into account.

In both cases the fact that speed of light is constant does not prevent the effect from happening, although it does influence the magnitude in relativistic case.

More info on relativistic case:
http://en.wikiped...r_effect
smiffy
3 / 5 (2) Sep 28, 2008
Unfortunately we do not know that light travels at a constant speed in a vacuum.

There has never been and probably won't ever be any empirical proof of this because a perfect vacuum only exists in the minds of theoretical physicists. Or at least in nature there's no such thing as a perfect vacuum on a scale that would make experiments with the speed of light viable.
DoktorSerendipitous
not rated yet Sep 28, 2008
The best theory to account for all this is to conceive of our universe as just a bubble amongst myriad bubbles in a glass of cosmic champagne that God is about to drain, which of course will only take a few seconds in God's time frame, and a few tens of billions of years in ours.
Bazz
5 / 5 (1) Sep 28, 2008
God is not drowning in bubbles, hes merely has a bad case of the flu and bubbles are created from the mucus in His nose.
Modernmystic
1.5 / 5 (4) Sep 28, 2008
@neuro...

Man, where did you learn this? During Sunday mass in church? Could you back your opinions with quotes?


Actually if you did YOUR homework you'd find several stories on this very web site stating EXACTLY what he said. Perhaps you might try a little less egomaniacal condescension and a tad more SCIENTIFIC research in your comments.

For one, Sol-type suns (G) are quite common: the closest neighbor to our sun, Alpha Centauri, is a binary system, both components Sun-like (one G-type, the other K-type). Also Epsilon Eridani, Tau Ceti and 82 Eridani are sun-like. In our very Galaxy there are a few billion such stars. Therefore they are quite COMMON.


Which of course, if your were acquainted at all with the concept we like to call logic you'd know that statement is totally irrelevant to his comment. Also G type stars aren't common, unless you consider 7.6% COMMON...

Moreover it is totally erroneous as Alpha Centauri is a binary system and hence NOT like sol, Epsilon Eridani is lower in metals than the sun and it's stellar wind is some 30 times greater than the sun (bringing it's bow shock out to a whopping 1600 AU), Tau Ceti has a metallicity 1/3 that of the sun meaning that terrestrial planets like the Earth are far less likely to form around it, and lastly 82 Eridani is also metal deficient. Are you REALLY ignorant enough to think that spectral class is the only factor in habitability of a star? Were did you learn that...junior high science class?

Secondly, NO-ONE (except you, probably) knows at the moment whether Earth-like planets are rare or commonplace. That's just because we don't have a sufficiently advanced observation technology yet to even detect those comparatively tiny worlds. Fortunately, required tech level should be attained within next 5-10 years (TPF, Darwin, optic comb & other projects).


Actually our detection methods aren't as bad as you make them out to be and mostly what we find is hot Jupiters (which of course we don't have in this system) and highly elliptical orbits of basically EVERY planet we've detected which we ALSO don't see in this system and has an effect on habitability.

I suggest that all pessimists first do some simple research before posting.


Pot...kettle...black...

FYI: Actually, astronomers were quite surprised to find so many planets thus far, some in environments never suspected to be capable of harboring them.


FYI: ACTUALLY astronomers never expected to see hot Jupiters AT ALL much less in the quantities they have, they also never expected to see planets in the highly elliptical orbits they're in either.
zanzzz
not rated yet Sep 28, 2008
What does this theory do to recent "dark flow" observations? Can it explain away the dark flow?
jeffsaunders
4.8 / 5 (4) Sep 28, 2008
Copernicus postulated that we are not anything special and therefore why should the earth be the center of the universe.

Good point. but that is not to be taken so far that we must never suggest that the universe is not homogeneous.

Given that it is possible that the universe is not homogeneous and that some parts of the universe may be thicker or thinner than other parts and given that the some parts of the universe are expanding and some contracting and given that we have to exist somewhere in the universe.

Given all that it is not so bad to suggest that the bit of the universe we are in may be doing something different than other bits of the universe.

Given that we are making observations of the universe in our general vicinity and that we are observing strange behaviour - it is reasonable to postulate that the strange behaviour we have witnessed may be a local problem.
Graeme
not rated yet Sep 28, 2008
Light energy pressure is 6.305*10-17T^4 J/(m^3K^4), or for the CMB is 3.34 * 10^-15 pascals - it is not high. boiling water has a radiation pressure of 22 microPascals, still not super high, but I don't know what the actual figures are for the dark energy negative pressure.
Modernmystic
1 / 5 (3) Sep 28, 2008
Isn't the pressure related to the cosmological constant in some way?
manojendu
not rated yet Sep 29, 2008
Its not unimaginable that there are other entities far beyond the known universe providing balance in terms of mass and energy to the equation.


Like Dark Energy?
manojendu
5 / 5 (1) Sep 29, 2008
@The Walrus
@deatopmg:

The red/blue shift is caused by the frequency of light changing as you approach or recede from the source. It really is like the Doppler effect. The Doppler effect doesn't change the speed of sound, only its frequency. Same with the red/blue shift.


I get that w/ sound where we are intercepting more or less waves in a given time. BUT if the speed of light is constant and I'm on an object traveling away from a monchromatic light beam, say blue, at a large fraction of C, the blue light beam still passes me at C, independent of my speed, so the frequency cannot down shift to red because the wavelets pass me unchanged at the same speed C. If it does (and we "know" it red shifts) then SR and GR must be out the window.


Please read about phase velocity, group velocity, time dilation, etc. before making any comments!

But first read about wavelength and how that changes the frequency (i.e. colour) of a wave, even though the speed (c) remains constant.
bredmond
not rated yet Oct 02, 2008
I didnt read all the posts, so i dont know if it has been said, and this may be trite, but maybe the *visable universe* is expanding to fill some other void left elsewhere by some other part of the *universe beyond*. all the fundamental rules apply everywhere, it is just they appear differently in this region where the space has expanded.
superhuman
1 / 5 (1) Oct 04, 2008
I didnt read all the posts, so i dont know if it has been said, and this may be trite, but maybe the *visable universe* is expanding to fill some other void left elsewhere by some other part of the *universe beyond*. all the fundamental rules apply everywhere, it is just they appear differently in this region where the space has expanded.


The void would have to surround the universe from all directions but even then the expansion rate would not be homogeneous as the part on the edge of the void should expand faster then parts farther from it and that is not the case as far as we can tell (unless we assume Earth is in the center of the Universe and void is equidistant in all directions).
deatopmg
1 / 5 (2) Oct 04, 2008
manojendu
thanks
daetopmg

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