The elegant universe

w1z4rd said:
omg :( thread pollution.
Click to expand...
For those actually interested discussing the article (and no it does not need a new thread, that would be pollution)... It is quite interesting:
The barrage of new work on testing the Copernican principle has certainly stimulated interest, with a flurry of papers in the past year proposing refinements or completely different tests. So what would it actually mean if, against the expectation of Caldwell and the majority of cosmologists, the outcome were that the Copernican principle is wrong?

It would certainly require a seismic reassessment of what we know about the universe. Our big bang model is particularly simple, characterised by universal quantities such as matter and energy densities and the rates of expansion and acceleration, whether negative or positive. If the Copernican principle fails, all that goes out of the window too. In that case, quantities we measure in our own rather special corner of the universe will turn out to have only parochial significance, with no deeper universal meaning. We would no longer be sure what, if anything, we can conclude about the wider universe, its origin, evolution and fate. Cosmology would be back at the drawing board.

If we are in a void, answering how we came to be in such a privileged spot in the universe would be even trickier. But regardless of how uncomfortable the philosophical implications might be, for Ellis it is a matter of scientific principle to test cherished but untested assumptions. "Whatever our theoretical predilections, they will in the end have to give way to the observational evidence," he says.

The Copernican principle might survive the tests, leaving us with the known unknown of dark energy. Or it might fall, leaving us with the unknown unknown of an entirely new cosmological model. Either way, cosmologists will still have plenty of explaining to do.
Click to expand...
 
Geocentrism again?

'Big Wave' Theory Offers Alternative to Dark Energy

Mathematicians have proposed an alternative explanation for the accelerating expansion of the universe that does not rely on the mystifying idea of dark energy.

According to the new proposition, the universe is not accelerating, as observations suggest. Instead, an expanding wave flowing through space-time has caused distant galaxies to appear to be accelerating away from us. This big wave, initiated after the Big Bang that is thought to have sparked the universe, could explain why objects today appear to be farther away from us than they should be according to the Standard Model of cosmology.

"We're saying that maybe the resulting expanding wave is actually causing the anomalous acceleration," said Blake Temple of the University of California, Davis. "We're saying that dark energy may not really be the correct explanation."

The researchers derived a set of equations describing expanding waves that fit Einstein's theory of general relativity, and which could also account for the apparent acceleration. Temple outlines the new idea with Joel Smoller of the University of Michigan in the Aug. 17 issue of the journal Proceedings of the National Academy of Sciences.

While more research will be needed to see if the idea holds up, "the research could change the way astronomers view the composition of our universe," according to a summary from the journal.

To convince other cosmologists, the new model will have to pass muster with further inquiry.

"There are many observational tests of the standard cosmological model that the proposed model must pass, aside from the late phase of accelerated expansion," said Avi Loeb, director of the Institute for Theory and Computation at the Harvard-Smithsonian Center for Astrophysics. "These include big bang nucleosynthesis, the quantitative details of the microwave background anisotropies, the Lyman-alpha forest, and galaxy surveys. The authors do not discuss how their model compares to these tests, and whether the number of free parameters they require in order to fit these observational constraints is smaller than in the standard model. Until they do so, it is not clear why this alternative model should be regarded as advantageous."

Johns Hopkins University astrophysicist Mario Livio agreed that to be seriously considered, the model must be able to predict properties of the universe that astronomers can measure.

He said the real test "is in whether they are able to reproduce all the observed cosmological parameters (as determined, e.g. by a combination of the Hubble Constant and the parameters determined by the CMB observations). To only produce an apparent acceleration is in itself interesting, but not particularly meaningful."

Inconvenient truths

Dark energy is itself a hasty fix to an inconvenient truth discovered by astronomers in the late 1990s: that the universe is expanding, and the rate of this expansion seems to be constantly picking up speed.

To explain this startling finding, cosmologists invoked dark energy, a hypothetical form of energy that is pulling the universe apart in all directions (note that dark energy is wholly separate from the equally mysterious concept of dark matter - a hypothetical form of matter that populates the universe, interacting gravitationally with normal matter, but which cannot be seen with light). In this interpretation, the whole universe is blowing up like a balloon, and from any given point within it, all distant objects appear to be speeding away from you.

But not everyone is happy with the dark energy explanation.

"It just seems like an unnatural correction to the equations - it's like a fudge factor," Temple told SPACE.com. "The equations don't make quite as much physical sense when you put it in. You just put it in to fit the data."

Temple and Smoller think the idea of an expanding wave makes more sense.

"At this stage we think this a very plausible theory," Temple said. "We're saying there isn't any acceleration. The galaxies are displaced from where they're supposed to be because we're in the aftermath of a wave that put those galaxies in a slightly different position."

Ripples in a pond

Temple compared the wave to what happens when you throw a rock into a pond. In this case, the rock would be the Big Bang, and the concentric ripples that result are like a series of waves throughout the universe. Later on, when the first galaxies start to form, they are forming inside space-time that has already been displaced from where it would have been without the wave. So when we observe these galaxies with telescopes, they don't appear to be where we would expect if there had never been a big wave.

One potential issue with this idea is that it might require a big coincidence.

For the universe to appear to be accelerating at the same rate in all directions, we in the Milky Way would have to be near a local center, at the spot where an expansion wave was initiated early in the Big Bang when the universe was filled with radiation.

Temple concedes that this is a coincidence, but said it's possible that we are merely in the center of a smaller wave that affects the galaxies we can see from our vantage point - we need not be in the center of the entire universe for the idea to work.
Click to expand...
 
Phronesis said:
The anthropic principle just won't go away:
The universe seems to be built for us?
Click to expand...

It's kind of like hearing a puddle saying, "Wow, I fit into this gap in the pavement so well, it seems to have been made just for me!"

(With apologies to Douglas Adams.)
 
Lucky puddle that... On top of that table and in a bowl with ice cubes in it on a hot day covered with just enough shade for it to last more than a few days...

Lucky puddle indeed.
 
Phronesis said:
Lucky puddle that... On top of that table and in a bowl with ice cubes in it on a hot day covered with just enough shade for it to last more than a few days...

Lucky puddle indeed.
Click to expand...

No, that's an *intelligent* puddle that's learned how to take care of itself.

However, most sentient puddles just sit in their gap thinking what an amazing gap it is, until they dry up and get reincarnated as rain.
 
No, that puddle just happened to be there. Not as a result of its own will. Lucky one hey?
 
Phronesis said:
No, that puddle just happened to be there. Not as a result of its own will. Lucky one hey?
Click to expand...

Which puddle are you talking about? The intelligent puddle who got off its watery ass and invented icecubes? Or the stupid puddle which just sits there praising the Most Awesome Maker of the Gap?
 
The puddle that just happened to find itself in a bowl of ice cubes... in the shade.
 
BCO said:
I don't think that 300 planets orbiting other stars is a very representative sample, considering there are hundreds of billions of solar systems out there.
Click to expand...

+1

Furthermore, the sample is obviously biased, If it is based on only on exoplanets:

The manner in which we discover these planets are by the gravitational effects they have on their sun/star. Hence, larger planets => larger effects on their sun which our instruments can pick up on. I could go on and explain those "large planets" star systems would be much more chaotic than say a "small planets" star system but you get the idea.

We not that special, deal with it
 
battletoad said:
+1

Furthermore, the sample is obviously biased, If it is based on only on exoplanets:

The manner in which we discover these planets are by the gravitational effects they have on their sun/star. Hence, larger planets => larger effects on their sun which our instruments can pick up on. I could go on and explain those "large planets" star systems would be much more chaotic than say a "small planets" star system but you get the idea.

We not that special, deal with it
Click to expand...

+1
 
They used the data from the 300 planets and known physical laws to create simulations, and came to the conclusion from those simulations. Of course the simulations will be refined as more and more data from other planetary systems come in.
What the data suggests so far.... well you know the story.
 
Fine, but not once did i read something saying that the data is only considering large planets(only planets we found, some 100x's bigger than Jupiter) and the implications it has on the results of the experiment.
Looks to me as if the bosses came around asking why they should spend money on this research and the scientists gave them them something they wanted to continue research.
 
Still a pretty interesting finding whichever way you look at it. "Bosses" can research whatever they want if they get funding for it and researchers that are able to do the job based on current understanding and evidence.

grayston said:
And even if we *are* special, it proves absolutely nothing one way or the other!
Click to expand...
Of course not, which way can be proven? Whatever way you are alluding to here? But... it would support the notions of many idealistic views of the universe.
 
Phronesis said:
Our universe also seem to be special... fine tuned.

The anthropic principle just won't go away:
The universe seems to be built for us?
Click to expand...

Put it to you this way, we don't find birds underwater. Why? it just doesn't work for them. Any animal that woke up one day and thought to itself "Hey, I'll start walking backwards" walked right into a lion's mouth(or any other of it's predators). You don't see the universe going around trying to make things easier for them to survive.

The universe was here first, so if we want to occupy it, we have to abide by it's rules. We are built to survive in the universe

In a nutshell, evolution.
 
You must log in or register to reply here.
Back
Top
Sign up to the MyBroadband newsletter
X