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cbfull

Tue Aug 07 2007, 08:05PM

Registered Member #187 Joined: Thu Feb 16 2006, 02:54PM
Location: Central Ohio
Posts: 140

I'm not sure if my post was easy to follow, perhaps I threw it out there hastily. Your points don't seem to address what I wrote.

For example, I was addressing the accelerated expansion of the universe, not the expansion, so I'm sorry I thought that was clear.

I haven't been doing my "cosmological observations" homework so I can't comment on any lack or abundance of observations that are agreeing on the accelerated expansion.

BjÃ¸rn BÃ¦verfjord wrote ...
So far everyone that has had other ideas have been left looking silly.

- if someone looks silly for having a theory that doesn't survive, that would likely only require that the observer be arrogant. "Looking" silly doesn't really say anything about the one being looked at.

BjÃ¸rn BÃ¦verfjord wrote ...
A hypothesis that the universe does not expand is not going anywhere...

Did you mean for that statement to funny? It's actually pretty good if you end it at that point. Aside from the comical interpretation, I know what you meant, and I refer you to my first comment since I already pointed out that it is the acceleration I am concerned with.

BjÃ¸rn BÃ¦verfjord wrote ...
...you would need a complete theory that can explain everything we observe. In addition you need a testable prediction that the current theory will fail.

- I'm really only interested in participating in the discussion.

BjÃ¸rn BÃ¦verfjord wrote ...
If not the new theory is worse than the old one and there is no reason to consider a switch.

- Switch? I have no desire to proselytise any scientists, I don't want to seem that serious!

BjÃ¸rn BÃ¦verfjord wrote ...
Step 1 would be to prove that there is red shift over distance or time independently of velocity.

- I enjoy the simplicity of a different way of interpreting observations, not trying to change it from theory to fact. Besides, I thought step 1 was to believe in a theory?

I think that sharing my thoughts about this matter is sufficient. I am not really interested in any competetive scenario. That approach is a bit too aggressive for a forum discussion.

Please forgive me if I have misinterpreted the intention of your comments, but they seem a bit dismissive. I was hoping for something a bit more constructive and engaging.

Bjørn

Wed Aug 08 2007, 12:53AM

Registered Member #27 Joined: Fri Feb 03 2006, 02:20AM
Location: Hyperborea
Posts: 2058

You post was not very clear and my post was not supposed to be funny.

First we have to differ between dark matter and dark energy. Dark matter is something that makes up most of the mass of galaxies. It is clearly observable in the way it affects the motion of galaxies and how it affects light by gravitation. It is not observable in other direct ways so it is called dark matter.

Dark energy is something that is thought to be responsible for the accelerating expansion of the universe. It is not lumped up in galaxies and appears completely diffused through the universe.

There are several different types of evidence for accelerated expansion, like supernovae, cosmic background radiation and a couple of others. There is no fixed theory, there are several that contains many assumptions about the structure of the universe.

Dark energy is a reasonable assumption since it is suggested by observation.

That light are affected by time, distance travelled or something else is probably harder to believe than that the universe contains some sort of energy wrapped up in the structure. A lot of very accurate measurements have been made and no sign of unexpected effects on light has been found so if it exist it must be very exotic since it is uniform in all directions and at all distances.

I don't say that it does not exist or that it should not be discussed, but it does seem like a poor fit with observations. It would also be like replacing one strange force with something that seems more familiar but may turn out to be even stranger.

I am also quite sceptical to how some of modern science is conducted and I would not be completely shocked if accelerated expansion should turn out to be a fad and in reality be something else.

Carbon_Rod

Wed Aug 08 2007, 06:52AM

Registered Member #65 Joined: Thu Feb 09 2006, 06:43AM
Location:
Posts: 1155

The people who study String and Membrane theory touch on this subject often.

Dark matter is still a mystery, but the giant accelerator will be complete in the next few years and may answer some questions.

Personally, I find only ambiguity and suppositional arguments arise from discussions related to the super gravity ideas. You are not dumbing it down, as many theories are complete BS in the first place.

What camp are you in: 11 or 10 dimensions?
(Keep in mind I think mostly in Z2, therefore can't understand answers beyond 0 or 1.)

Cheers, =)

Marko

Wed Aug 08 2007, 02:38PM

Registered Member #89 Joined: Thu Feb 09 2006, 02:40PM
Location: Zadar, Croatia
Posts: 3145

Hi guys..

I'm not surprised bjorn reacted at cbfull's first post, since it is easily understood as some kind of
speculative static-universe idea.

Acceleration is much harder to measure but there are increasing evidence for it. All of this is somewhat straying from the topic.

Dark energy is a reasonable assumption since it is suggested by observation.

How exactly is it suggested by observation? Only thing that appears to be observed is acceleration itself.

Dark energy which interacts only by gravity does not fulfill this. I would expect it to behave just as any normal energy unless it interacts by a currently unknown force.

There are lots of sites studying this matter, and still all of these spin in circles.
They usually end comparing the 'negative pressure' to negative pressure in fluids or solids which is due to electrostatic 'adhesion' and I think such a comparison is nonsensical in this case.

- especially see ''negative pressure'' equations - it looks just like fudge factor steve described.

From all this I came to conclusion that dark energy thing is a BS. I hoped to be proven wrong by someone.

Bjørn

Wed Aug 08 2007, 08:15PM

Registered Member #27 Joined: Fri Feb 03 2006, 02:20AM
Location: Hyperborea
Posts: 2058

How exactly is it suggested by observation? Only thing that appears to be observed is acceleration itself.

You need something causing the acceleration that is not directly observable and that is not affected by gravity like matter. To avoid breaking current observations it suggests invisible energy of some form, so we call it dark energy. Since the form is completely unknown there is not much you can say about it except trying to put observational constraints on the form and see what it ends up like. As long as the observations are very difficult to make there will be a lot of speculations and weird ideas floating around.

We should also note that this is nothing new, Einstein introduced the term Lamda or "cosmological constant" to his equations to make them fit his view of a static universe. When it was discovered that the universe was expanding he removed this term since it did not seem to fit observations anymore. Now that more accurate observations points to accelerating expansion it has been reintroduced. The name has changed but the equations are the same as 90 years ago.

They usually end comparing the 'negative pressure' to negative pressure in fluids or solids which is due to electrostatic 'adhesion' and I think such a comparison is nonsensical in this case.

That is an increasingly popular way of thinking because tinkering with equations have not made much progress. Gasses and fluids seems to have a remarkable way of predicting effects related to the speed of light and the structure of the universe by speed of sound effects combined with other properties. How far this analogy can be stretched is unknown.

Coyote Wilde

Sun Aug 12 2007, 08:24PM

Registered Member #175 Joined: Tue Feb 14 2006, 09:32PM
Location: Sudbury, ON
Posts: 111

Dark energy is a pretty dumb name, since it causes people to automatically associate the cosmological constant with dark matter...
Which, I can, at least, propose (well, point out someone's proposal) for an alternate theory to do away with: Modified Newtonian Dynamics. Though I know there's been some recent work which dark matter supporters are claiming "proves" that dark matter has to be the controlling factor of the motion of galaxies (the bullet cluster in particular being cited) -- I haven't seen how MOND tackles it, but MOND and neutrino mass seem to account for most other 'dark matter' phenomenon, without having to invent exotic new particles. Instead, just rewrite the entire framework of the laws of physics. The main critique of it is that it is an observation-derived theory, rather than an a priori basis on some wonderfully abstract mathematical concept , like, say string theory. To that I can only say that at least MOND makes verifiable predictions

Oh, and that a man named Planck started the same way when dealing with blackbody radiation...

As for dark energy, MOND isn't currently any help, but there's some evidence (well, hope, really) that a relativistic version of the theory incorporating the strange new force relation could solve that issue as well.
I know the bullet cluster data suggests otherwise, but I can't help hoping MOND pulls out over DM; you have to admit, it's a helluva more elegant.

cbfull

Tue Aug 14 2007, 02:20PM

Registered Member #187 Joined: Thu Feb 16 2006, 02:54PM
Location: Central Ohio
Posts: 140

I'm not trying to ruffle feathers here, so take it easy on me if I seem naive. I think it will be easier to read my message now that I have used quotations properly (sorry bout that Bjorn! I think I should fix that).

Marko wrote ...
I'm not surprised bjorn reacted at cbfull's first post...

Me either, I don't think he likes me. :)

Marko wrote ...
Acceleration is much harder to measure but there are increasing evidence for it. All of this is somewhat straying from the topic.

How does this stray from the topic of Universal acceleration? Are you referring to the existance of dark matter/energy?

Marko wrote ...
Only thing that appears to be observed is acceleration itself.

I am not sure I agree with you here, we are so dependent on the information given to us by our eyes (observation) when it comes to cosmic phenomena, as responsible scientists, we must acknowledge that we are very limited in our ability to "observe"

If I can restate, the only thing that is observed is light itself, and nothing else. The rest is done with our brain.

Chris

Wed Aug 15 2007, 03:47AM

Registered Member #8 Joined: Thu Feb 02 2006, 04:34AM
Location: Harlowton, MT, United States
Posts: 214

I hope none of you, especially Bjoern, have forgotten how often the "scientific" consensus so long held as fact has been proven so false as to be laughable to subsequent generations. Majority is not always right, and the ones that have made the greatest steps have always looked silly before their ideas were proven.

Now I'm no expert on the subject, so I can't make a very good scientific argument about this, but as far as I know we don't have any observations that can't be explained by this photon drag theory just as well as the accelerating expansion theory. Objects farther away appear to have more redshift, that is all. I suspect both theories are false, actually, because we have such a limited understanding of what is going on at great distance. These are just two relatively feeble theories that we have no way of proving or disproving. Someone hundreds of years ago would have suspected from observations that the stars are rotating rather rapidly around the earth because transverse movement was the only observable measure of motion. Likewise we are probably relying too heavily (and falsely) on dopplar shift. We need better tools before we can make more sound theories about the distant universe.

I have no reason to disagree with the theory that the universe is expanding, but the idea that it is accelerating apart is sketchy at best. I would not be susprised if they all turned out to be false really. I would not be surpsised in the least if dark matter turned out not to exist in any form at all, as well as dark energy, or if the estimated age of the universe was off by 100 orders of magnitude. Perhaps the apparent mass of distant galaxies which cannot be accounted for is due to errors in our own observations, things we have missed, or something we haven't thought of, rather than due to some unseen form of matter that is now so widely held to exist factually. What if this "dark" matter is simply, literally that? Matter that is cold, like a rock floating in space. A long cooled dead star, or a black hole; we can't see these sorts of things from very far away and cannot know how prevalent they are. Maybe 74% of the universe is made up of them. Maybe we are all totally wrong about 90% of the things we have observed out there and think is true, since we have no way to actually go and study them.

Of course I don't expect any of you to really pay attention to what I am saying or looking into the points I am trying to make before discounting it, because people are too stubborn and usually just skim things that they don't agree with after diving in with preconceived notions of falseness.

Carbon_Rod

Wed Aug 15 2007, 09:15AM

Registered Member #65 Joined: Thu Feb 09 2006, 06:43AM
Location:
Posts: 1155

Physics has always had an unofficial hierarchy where research grants are evaluated on popularity.

Personally I found sponge theory a rather interesting notion, yet it was considered a joke and the initial lecturer was laughed off stage. I doubt anyone will stake their reputation on the subject anytime soon.

Steve Conner

Wed Aug 15 2007, 09:49AM

Registered Member #30 Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706

I agree with Chris. I couldn't care less if the Universe was restrained from expanding by colossal webs of duct tape, hot glue, and No More Nails(tm). I prefer to stick to research that has a measurable outcome, such as a paycheck.

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