ISF Logo   IS Forum
Forum Index Register Members List Events Mark Forums Read Help

Go Back   International Skeptics Forum » General Topics » Science, Mathematics, Medicine, and Technology
 


Welcome to the International Skeptics Forum, where we discuss skepticism, critical thinking, the paranormal and science in a friendly but lively way. You are currently viewing the forum as a guest, which means you are missing out on discussing matters that are of interest to you. Please consider registering so you can gain full use of the forum features and interact with other Members. Registration is simple, fast and free! Click here to register today.
Tags cosmology , dark energy , dark matter , quantum mechanics , spacetime

Reply
Old 7th July 2009, 10:56 AM   #1
Cogwheel
Student
 
Join Date: Dec 2008
Posts: 32
Dark Matter/Energy, Resolution of Spacetime, etc.

Warning: This is wild speculation from someone who probably doesn't know what he's talking about. Please link me to any resources that would set me straight.

Cliffs Notes: Could the possibility of a fundamental resolution to the universe explain dark matter/energy?

Something about the search for the nature of dark matter/energy has always bugged me. Every time I've seen the topic explored (and I admit I haven't done any really advanced reading on it), they've taken for granted that the dark matter is a real substance that we can potentially interact with, and that the dark energy is an actual force being exerted on normal matter. In some ways it reminds me of the search for the luminiferous aether. Has anyone seriously explored the possibility that it's an effect of some (simpler) underlying cause?

In my time playing around with computer graphics, I became quite familiar with various aliasing effects. These range from "jaggies" and Moiré patterns in the spatial realm, to strobe effects like reversed wheel rotation in the temporal realm. These artifacts are distracting to viewers, so we use antialiasing techniques to alleviate the problem. Jagged edges are smoothed by what essentially amounts to blurring. Moiré patterns succumb to anisotropic filtering. Temporal antialiasing, aka motion blur, is more explicit about its goal. There is a fundamental limit to the amount of information an image can store at a particular resolution. Antialiasing removes a bit of certainty about the original source in exchange for a boost in perceived resolution.

What if there's a similar story going on "under the hood" of the cosmos? The first time I considered this was when I learned about Planck <measurement>. To my compsci-biased mind, this struck me as a fundamental resolution and bit-width/dynamic range for the universe. The first thing I noticed was that the blurring effect of antialiasing is roughly analogous to the uncertainty principle, which deals with effects on the Planck scale.

Obviously this is a retcon for me. I was simply trying to put the realities of QM into terms I could easily understand. But to my surprise, there are a few ideas being seriously advanced that are along the same lines:

http://www.newscientist.com/article/...html?full=true

http://shell.cas.usf.edu/~eclark/ANK...in_thesis.html

http://www.newscientist.com/article/...html?full=true

The holographic and cellular automata explanations would certainly vindicate my resolution idea, and the fractal universe is at least compatible. When I heard about the holographic universe on The Skeptic's Guide to the Universe (#183), it made me think a bit (har) more about the bit-width or dynamic range analogy. They discussed how gravity wave detectors weren't seeing gravity waves but were getting a fairly consistent noise they weren't expecting (reminded me--and the cast--of the CMBR's discovery). This could easily be explained as a bottoming out of the dynamic range of the gravity field. Since gravity gets weaker as you get further from the source, the ideas above suggest that it would effectively disappear at some point.

Now dark energy attempts to explain why the universe's expansion is accelerating in defiance of gravity. What if there is basically no gravity at the massive distances between galaxies? That would at least explain gravity's impotence. Perhaps the extra oomph comes from quantum fluctuations (rounding error?) in this gravitational dead zone.

Dark matter tries to explain the opposite effect. Galaxies should be flying apart given the amount of matter we can detect inside them. What's holding them together? I haven't explored this idea in as much depth, but it seems like the resolution/dynamic range ideas could help explain this extra cohesiveness. Perhaps some of the resolution errors at the small scale create significant effects at the large scale. Maybe the dark energy effect is also "pushing" inwards over a large scale that isn't noticeable in the small scale.

Again, this is all wild speculation on my part. It's a fun exercise for my gray matter, but if it's all in vain, I'd rather turn my attention elsewhere. Let me know what you think.
Cogwheel is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 7th July 2009, 11:25 AM   #2
Dancing David
Penultimate Amazing
 
Dancing David's Avatar
 
Join Date: Mar 2003
Location: central Illinois
Posts: 39,699
UM, there appears to be a gravitational effect beyond that from the observed matter in galaxies.

So that stars orbit faster than they ought to, the velocity of an orbiting object is related to the masses involved, and stars move faster than they ought.
Especially in the outer areas of galaxies.

Now the matter we estimate to be there is 20% of what the velocity would be related to.

So there are possibilities, one that the estimates of the matter are way off. And this is being investigated. However so far, they extra matter has not been found. As far as MACHOs go.

So the other possibility is that there are WIMPs , weakly interacting massive particles. They would not interact with most matter through the EM force, but through the weak force and gravity.

Now neutrinos are already in this category, but current observation do not support the idea that the missing mass could be neutrinos.
But particles that are similar and have higher masses would fit the bill.

So dark matter halos (so called dark because they do not interact with the EM forces) are hypothesized to be around galaxies, providing the extra mass and in the areas to account for the rotation curves of galaxies.

And there are some good reasons to feel there is data that suggests there is dark matter.

However people get all bent out of shape over it, even though neutrinos sure appear to exist.

So how would the holographic model account for the observations of gravitational forces beyond that from the estimates of mass?
__________________
I suspect you are a sandwich, metaphorically speaking. -Donn
And a shot rang out. Now Space is doing time... -Ben Burch
You built the toilet - don't complain when people crap in it. _Kid Eager
Never underestimate the power of the Random Number God. More of evolutionary history is His doing than people think. - Dinwar
Dancing David is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 7th July 2009, 03:06 PM   #3
sol invictus
Philosopher
 
sol invictus's Avatar
 
Join Date: Oct 2007
Posts: 8,613
Originally Posted by Cogwheel View Post
Let me know what you think.
Many people have played with the idea that space, or space and time, might be discrete in that way. There is a major hurdle, though. Einstein's theories of relativity are based on the existence of a symmetry - Lorentz invariance - which prohibits a lattice of the kind you have in mind. Of course it might just be that the lattice is very very small, so it's hard to notice and we haven't seen it yet. But we have extremely strong tests of Lorentz invariance from particle physics, and so far there is no sign of such a thing. Moreover at a black hole horizon a lattice like that gets very, very stretched and deformed, and any simple or naive version of it goes haywire completely at the horizon (in a certain sense space bend around and turns into time at the horizon, which is perfectly OK if spacetime is smooth, but very difficult to arrange if there's a lattice).

As for the connection to dark energy, you're correct that a lattice of that type contributes to the energy density of the universe. If the lattice can somehow expand without changing its physical density - a very strange feature since it means new grid points must keep appearing, but one that's required for consistency with cosmology and for reasons related to the black hole horizon problem I already mentioned - it will contribute a cosmological constant-type energy density. But again, there is a major problem - the magnitude of the energy you expect from such a lattice is of order the inverse lattice spacing (that's something that follows immediately from quantum mechanics, from the Heisenberg uncertainty principle), and considering how small the lattice must be that energy density turns out to be bigger than the measured value of the cosmological constant by a factor of around 10^120 (1 with 120 zeros).

That's a version of what's called the cosmological constant problem, and as you can see, it's a big problem.

So your ideas are interesting and a good place to start, but you have a few kinks to work out .

Last edited by sol invictus; 7th July 2009 at 03:09 PM.
sol invictus is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 8th July 2009, 07:35 AM   #4
Cuddles
Penultimate Amazing
 
Join Date: Jul 2006
Posts: 18,590
Originally Posted by Cogwheel View Post
Something about the search for the nature of dark matter/energy has always bugged me. Every time I've seen the topic explored (and I admit I haven't done any really advanced reading on it), they've taken for granted that the dark matter is a real substance that we can potentially interact with, and that the dark energy is an actual force being exerted on normal matter.
This it the problem with speculating on advanced physics with only a layman's knowledge. Dark matter is not taken for granted at all, it being a real substance is a conclusion reached from many different observations. Motion within galaxies and gravitational lensing are two things that independently say there must be some mass present that we can't see using light (of any frequency). We call that mass dark matter. We don't know exactly what it is, but we're pretty certain that it's the best explanation we have for the observations.

Dark energy is a bit less certain, but is arrived at via similar reasoning - we make various observations and dark energy has turned out to be the explanation that fits best. An important point to bear in mind is that it is not an actual force being exerted on normal matter, it is something that affects space itself, specifically the expansion of space. It is not a force at all in the ordinary sense of the word, hence being called "dark energy" rather than "dark force".

All that aside, quantisation of time and space is certainly not a new idea. The problem is simply that, as Sol says, we haven't found a theory including it that is consistent with observations. In the end, speculation about this sort of idea faces the same problem that all speculation by non-experts does - no matter how sensible your speculations seem, they will never really mean anything without a coherent theory that matches observations. And the only way to come up with one of those is to understand the maths surrounding the problem and to understand (and, importantly, have access to) the observations.
Cuddles is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 8th July 2009, 08:13 AM   #5
Cogwheel
Student
 
Join Date: Dec 2008
Posts: 32
Thanks guys. Appreciate the insight.
Cogwheel is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 8th July 2009, 08:15 AM   #6
edd
Master Poster
 
edd's Avatar
 
Join Date: Nov 2007
Posts: 2,120
Originally Posted by Cuddles View Post
Dark energy is a bit less certain, but is arrived at via similar reasoning - we make various observations and dark energy has turned out to be the explanation that fits best. An important point to bear in mind is that it is not an actual force being exerted on normal matter, it is something that affects space itself, specifically the expansion of space. It is not a force at all in the ordinary sense of the word, hence being called "dark energy" rather than "dark force".
Well, I think you can go a bit further than that. Dark energy is simply a source of gravity like matter is a source of gravity. It just does it differently to matter. I would be very hesitant of saying it doesn't apply a force to matter - it makes it seem more removed from the mechanics by which matter itself affects the expansion of the universe, when the mechanics for the two are fundamentally the same.

I'm not saying anything you've said is incorrect, but I worry it paints a misleading picture where dark energy is acting through something other than gravity.
__________________
When I look up at the night sky and think about the billions of stars out there, I think to myself: I'm amazing. - Peter Serafinowicz
edd is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 8th July 2009, 08:41 AM   #7
Myriad
Hyperthetical
 
Myriad's Avatar
 
Join Date: Nov 2006
Location: Betwixt
Posts: 15,934
Hi Cogwheel,

Stephen Wolfram's book A New Kind of Science has a lengthy chapter on physics and cosmology (chapter 9) derived from cellular automaton-like rules. He posits not a rigid lattice with evolving contents (though he explores that possibility first) but an expanding network with evolving connections. It's very speculative stuff; a very interesting read but testable predictions and confirming evidence remain to be seen. The entire book, text and images, is available free online at http://www.wolframscience.com/nksonline/toc.html.

ETA: It's free but you do have to register at the site.

Respectfully,
Myriad
__________________
A zømbie once bit my sister...

Last edited by Myriad; 8th July 2009 at 08:42 AM.
Myriad is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 8th July 2009, 08:49 AM   #8
Cogwheel
Student
 
Join Date: Dec 2008
Posts: 32
Originally Posted by Myriad View Post
Hi Cogwheel,

Stephen Wolfram's book A New Kind of Science has a lengthy chapter on physics and cosmology (chapter 9) derived from cellular automaton-like rules. He posits not a rigid lattice with evolving contents (though he explores that possibility first) but an expanding network with evolving connections. It's very speculative stuff; a very interesting read but testable predictions and confirming evidence remain to be seen. The entire book, text and images, is available free online at http://www.wolframscience.com/nksonline/toc.html.

ETA: It's free but you do have to register at the site.

Respectfully,
Myriad
I read through much of that book a few years ago when I was obsessing over cellular automata. I'll have to check it out again.
Cogwheel is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Reply

International Skeptics Forum » General Topics » Science, Mathematics, Medicine, and Technology

Bookmarks

Thread Tools

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump


All times are GMT -7. The time now is 10:05 AM.
Powered by vBulletin. Copyright ©2000 - 2020, Jelsoft Enterprises Ltd.

This forum began as part of the James Randi Education Foundation (JREF). However, the forum now exists as
an independent entity with no affiliation with or endorsement by the JREF, including the section in reference to "JREF" topics.

Disclaimer: Messages posted in the Forum are solely the opinion of their authors.