1 of 6
1
Dark Energy, Dark Matter - Enigmas for Physicists and Cosmologists
Posted: 18 November 2007 07:39 AM   [ Ignore ]
Sr. Member
RankRankRankRankRankRankRankRankRankRank
Total Posts:  1823
Joined  2007-10-28

The existence of dark energy was “discovered” in 1998 and is now computed to be about 74% of the universe with 22% dark matter and the remaining 4% ordinary matter.

What is the nature of dark energy and why it is so elusive that only recently have cosmologists found it. Physicists and cosmologists are baffled and clueless. This could be the “ultraviolet catastrophe” of the 21st Century. No known theory in physics can account for it.

Read The New Scientist article on dark energy HERE

The problem giving cosmologists their big headache goes under the name of “dark energy”. This enigmatic entity - which could be some kind of a substance, or a field, or maybe something else entirely - forced itself into cosmologists’ consciousness in 1998, when astronomers discovered that something is speeding up the expansion of the universe. Almost a decade later, it is beginning to sink in that there is no easy way to understand what dark energy might be. The problem has become so intractable that many now see it as the greatest challenge facing physics.

There is no way to detect dark energy directly, so we have to measure its effects. The most obvious of these is the one that gave it away in the first place: the way it forces the expansion of the universe to accelerate.

Although there are plenty of tentative explanations, each one seems to suffer from some fatal flaw. The simplest of the solutions on offer is the so-called cosmological constant. This is an energy associated with space-time that was originally invoked by Einstein in his equations of general relativity. It represents a cosmic repulsion that Einstein fine-tuned to prevent the universe - which he did not at the time realise was expanding - from collapsing in on itself as a result of all the gravity generated by the various celestial objects.

One of those wild ideas is quintessence, which postulates the existence of a hitherto unsuspected quantum field permeating the universe (see “2: a new force of nature”). Because this implies that there would also be a new fundamental force of nature, the idea set some physicists thinking: instead of adding a new force, why not modify an old one? Perhaps there are unexpected properties of gravity that appear over gargantuan distances that Einstein’s general relativity does not predict

Einstein himself flirted with a weird form of energy that might just fit the bill. He called it the cosmological constant. These days physicists prefer the name vacuum energy, and like to think of it as the “cost” of free space. By that they mean that every cubic metre of space, no matter how cold or empty, contains a certain amount of energy. According to the equations of general relativity, this energy drives the expansion of the universe.

“Had everyone been happy with the cosmological constant there would be no need to continue,” says cosmologist Rocky Kolb of Fermilab in Illinois. The trouble is, no one really is happy with it. One reason for this is that quantum theory predicts a vacuum energy that is 120 orders of magnitude larger than what is needed to cause the observed acceleration in the universe’s expansion. This colossal discrepancy is one reason why physicists formulated supersymmetry theory, which cancels out vacuum energy completely.

The trouble is, the universe has other ideas: if the dark energy pushing it apart really is vacuum energy, the small amount that exists is infuriatingly difficult to explain. It certainly defeats any existing model.

“Dark energy could be the ether of the 21st century,” says Carroll. Even if we explain it away, we will learn something profound about the universe.

It is a viewpoint shared by cosmologists everywhere. “We are definitely seeing something extra in the universe, we just do not know how to interpret it yet,” says Lahav. And that has given cosmologists a new sense of purpose. A seismic shift in our understanding of the universe is coming. How soon it will arrive and from what direction it will come - that’s still anyone’s guess.

And dark matter. What is it? It was inferred from cosmological evidence in 1933 and is just as mysterious as dark energy. Here is the wiki on dark matter:

http://en.wikipedia.org/wiki/Dark_matter

In astrophysics and cosmology, dark matter is matter of unknown composition that does not emit or reflect enough electromagnetic radiation to be observed directly, but whose presence can be inferred from gravitational effects on visible matter. According to present observations of structures larger than galaxies, as well as Big Bang cosmology, dark matter accounts for the vast majority of mass in the observable universe.

The embarrassing thing is contemporary physics can only understand 4% of the universe!

[ Edited: 18 November 2007 06:00 PM by mckenzievmd ]
 Signature 

I am, therefore I think.

Profile
 
 
Posted: 18 November 2007 05:28 PM   [ Ignore ]   [ # 1 ]
Jr. Member
Avatar
RankRankRankRank
Total Posts:  81
Joined  2006-04-08

It’s not embarrassing at all, and I’m puzzled why you would make that statement.  Science is a progression from the unknown to the known, and this is just one more thing that we don’t know yet.  I’m sure in due time dark energy and dark matter will be explained and integrated into our scientific data base.  Of course, then we will have discovered new unexplained phenomena, and when that happens, you can come back and tell us how embarrassed we should be.

Profile
 
 
Posted: 18 November 2007 07:00 PM   [ Ignore ]   [ # 2 ]
Sr. Member
RankRankRankRankRankRankRankRankRankRank
Total Posts:  1823
Joined  2007-10-28
Jayhox - 18 November 2007 05:28 PM

It’s not embarrassing at all, and I’m puzzled why you would make that statement.  Science is a progression from the unknown to the known, and this is just one more thing that we don’t know yet.  I’m sure in due time dark energy and dark matter will be explained and integrated into our scientific data base.  Of course, then we will have discovered new unexplained phenomena, and when that happens, you can come back and tell us how embarrassed we should be.

And it is a BIG thing…96%. Are you so sure science is up to it, or is it human hubris? Remember the story of Icarus. Don’t misunderstand me. I am not anti-science. However, one should in mind that science is a human endeavour to explain the universe and like all human has limits. This might be an unknowable phenomena which science can name, but cannot explain.

Consider the search for TOE, the Theory of Everything:

http://en.wikipedia.org/wiki/Theory_of_everything#Modern_Physics

A small number of scientists claim that Gödel’s incompleteness theorem proves that any attempt to construct a TOE is bound to fail. Gödel’s theorem states that any non-trivial mathematical theory is either inconsistent or incomplete. Stanley Jaki pointed out in his 1966 book The Relevance of Physics, that since any ‘theory of everything’ will certainly be a consistent non-trivial mathematical theory, it must be incomplete. He claims that this dooms searches for a deterministic theory of everything.[6].

Stephen Hawking was originally a believer in the Theory of Everything but, after considering Gödel’s Theorem, concluded that one was not obtainable.

“Some people will be very disappointed if there is not an ultimate theory, that can be formulated as a finite number of principles. I used to belong to that camp, but I have changed my mind.”

[ Edited: 18 November 2007 07:02 PM by kkwan ]
 Signature 

I am, therefore I think.

Profile
 
 
Posted: 18 November 2007 07:24 PM   [ Ignore ]   [ # 3 ]
Administrator
Avatar
RankRankRankRankRankRankRankRankRankRank
Total Posts:  15305
Joined  2006-02-14
kkwan - 18 November 2007 07:00 PM

And it is a BIG thing…96%. Are you so sure science is up to it, or is it human hubris?

Er, I’m a bit confused. It was, after all, science that told us about the 4%/96%, no?

 Signature 

Doug

-:- -:—:- -:—:- -:—:- -:—:- -:—:-

El sueño de la razón produce monstruos

Profile
 
 
Posted: 19 November 2007 08:27 AM   [ Ignore ]   [ # 4 ]
Member
Avatar
RankRankRankRankRank
Total Posts:  102
Joined  2007-09-14

Gödel’s theorem states that any non-trivial mathematical theory is either inconsistent or incomplete.

Gödel’s poor, abused theory…  It doesn’t say that non-trivial theory is inconsistent or incomplete.  It says there exist true statements in a purely formal system which cannot be rigorously proved with said system.  As one consequence, it stipulates that there must always be axioms which are taken as true a priori without being proved by the system. 

This is contrary to what Hilbert and other proponents of formalism thought.  They believed mathematics was a kind of uroboros, lifting itself up by its own bootstraps (or swallowing it’s own tail, as it may be).

Rebecca Goldstein presents a nice and accessible treatment in her book Incompleteness… .

There are certainly lots of mathematical proofs (and physical theories) which are non-trivial.

As for dark-energy and dark-matter… They are delightful conundrums!  Until recently I liked the idea of MOND , which says maybe it’s our theory/equations of gravity that are wrong, and we don’t need a brand-new force or substance at all.  Then they went and found very persuasive evidence of dark matter via gravitational lensing.

Physicists are indeed puzzled, but I’m sure they’ll sort it all out in 100 years or so. smile

Profile
 
 
Posted: 19 November 2007 08:54 AM   [ Ignore ]   [ # 5 ]
Sr. Member
RankRankRankRankRankRankRankRankRankRank
Total Posts:  1823
Joined  2007-10-28

Doug,

The 96/4% was computed from recent cosmological evidence, but science cannot yet understand what is the nature of the 96% of dark energy and matter and why they exist.

[ Edited: 19 November 2007 08:57 AM by kkwan ]
 Signature 

I am, therefore I think.

Profile
 
 
Posted: 19 November 2007 09:46 AM   [ Ignore ]   [ # 6 ]
Sr. Member
RankRankRankRankRankRankRankRankRankRank
Total Posts:  1823
Joined  2007-10-28

tscott,

This is the wiki on Godel’s Incompleteness Theorems:

http://en.wikipedia.org/wiki/Gödel’s_incompleteness_theorem

The incompleteness results affect the philosophy of mathematics, particularly viewpoints like formalism, which uses formal logic to define its principles. One can paraphrase the first theorem as saying, “we can never find an all-encompassing axiomatic system which is able to prove all mathematical truths, but no falsehoods.”

On the other hand, from a strict formalist perspective this paraphrase would be considered meaningless because it presupposes that mathematical “truth” and “falsehood” are well-defined in an absolute sense, rather than relative to each formal system.

The following rephrasing of the second theorem is even more unsettling to the foundations of mathematics:

  If an axiomatic system can be proven to be consistent and complete from within itself, then it is inconsistent.

Hilary Putnam (1960) suggested that while Gödel’s theorems cannot be applied to humans, since they make mistakes and are therefore inconsistent, it may be applied to the human faculty of science or mathematics in general. If we are to believe that it is consistent, then either we cannot prove its consistency, or it cannot be represented by a Turing machine.

Theories of everything and physics

Stanley Jaki followed much later by Stephen Hawking and others argue that (an analogous argument to) Gödel’s theorem implies that even the most sophisticated formulation of physics will be incomplete, and that therefore there can never be an ultimate theory that can be formulated as a finite number of principles, known for certain as “final”.

Wittgenstein proclaimed mathematics is tautological.

Dark energy and dark matter has created a crisis in physics and cosmology which could trigger a major paradigm shift to account for them. We live in interesting times indeed.

 Signature 

I am, therefore I think.

Profile
 
 
Posted: 19 November 2007 11:56 AM   [ Ignore ]   [ # 7 ]
Jr. Member
Avatar
RankRankRankRank
Total Posts:  81
Joined  2006-04-08
kkwan - 19 November 2007 08:54 AM

Doug,

The 96/4% was computed from recent cosmological evidence, but science cannot yet understand what is the nature of the 96% of dark energy and matter and why they exist.

kkwan,

Look around you at all the scientific and technological developments you use everyday.  Pick up any science textbook.  In all of these cases, everything that we now “know” was once 96% unknown.

I don’t understand how a new scientific frontier is an issue for you.

Profile
 
 
Posted: 20 November 2007 02:44 AM   [ Ignore ]   [ # 8 ]
Sr. Member
Avatar
RankRankRankRankRankRankRankRankRankRank
Total Posts:  4375
Joined  2007-08-31
kkwan - 19 November 2007 09:46 AM

Dark energy and dark matter has created a crisis in physics and cosmology which could trigger a major paradigm shift to account for them. We live in interesting times indeed.

Hi Kkwan,

Can you tell me what you mean by ‘crisis’? What kind of paradigm shift do you expect?

GdB

 Signature 

GdB

“The light is on, but there is nobody at home”

Profile
 
 
Posted: 20 November 2007 08:27 AM   [ Ignore ]   [ # 9 ]
Sr. Member
RankRankRankRankRankRankRankRankRankRank
Total Posts:  1823
Joined  2007-10-28
Jayhox - 19 November 2007 11:56 AM
kkwan - 19 November 2007 08:54 AM

Doug,

The 96/4% was computed from recent cosmological evidence, but science cannot yet understand what is the nature of the 96% of dark energy and matter and why they exist.

kkwan,

Look around you at all the scientific and technological developments you use everyday.  Pick up any science textbook.  In all of these cases, everything that we now “know” was once 96% unknown.

I don’t understand how a new scientific frontier is an issue for you.

It is a truism that everything we now know was once unknown. It is not the same as saying that we do not know what 96% of the universe is.

It is not an issue for me at all. Indeed, it is very exhilarating to find out there is so much more out there to discover and understand.

[ Edited: 20 November 2007 08:30 AM by kkwan ]
 Signature 

I am, therefore I think.

Profile
 
 
Posted: 20 November 2007 08:38 AM   [ Ignore ]   [ # 10 ]
Jr. Member
Avatar
RankRankRankRank
Total Posts:  81
Joined  2006-04-08
kkwan - 20 November 2007 08:27 AM
Jayhox - 19 November 2007 11:56 AM
kkwan - 19 November 2007 08:54 AM

Doug,

The 96/4% was computed from recent cosmological evidence, but science cannot yet understand what is the nature of the 96% of dark energy and matter and why they exist.

kkwan,

Look around you at all the scientific and technological developments you use everyday.  Pick up any science textbook.  In all of these cases, everything that we now “know” was once 96% unknown.

I don’t understand how a new scientific frontier is an issue for you.

It is a truism that everything we now know was once unknown. It is not the same as saying that we do not know what 96% of the universe is.

It is not an issue for me at all. Indeed, it is very exhilarating to find out there is so much more out there to discover and understand.

If it isn’t an issue for you then why did you choose to use terms like “crisis” and “embarrassment” when this is just another day at the office for scientists?

And I agree with you that this is exhilarating.

Profile
 
 
Posted: 20 November 2007 09:25 AM   [ Ignore ]   [ # 11 ]
Sr. Member
RankRankRankRankRankRankRankRankRankRank
Total Posts:  1214
Joined  2007-09-21
kkwan - 19 November 2007 08:54 AM

The 96/4% was computed from recent cosmological evidence, but science cannot yet understand what is the nature of the 96% of dark energy and matter and why they exist.

I’m fine with the point that we don’t know much.  After all, we’re only human.  I wouldn’t doubt that we are capable of understanding even less of the universe than 4%.  It just seems to me that reason and science are the only ways that we have to know anything at all.  Can you think of an alternative way of knowing anything that does not involve reason or science.

To me, it seems not embarrassing, but ennobling that we understand anything at all.

Profile
 
 
Posted: 20 November 2007 09:52 AM   [ Ignore ]   [ # 12 ]
Sr. Member
RankRankRankRankRankRankRankRankRankRank
Total Posts:  1823
Joined  2007-10-28
GdB - 20 November 2007 02:44 AM
kkwan - 19 November 2007 09:46 AM

Dark energy and dark matter has created a crisis in physics and cosmology which could trigger a major paradigm shift to account for them. We live in interesting times indeed.

Hi Kkwan,

Can you tell me what you mean by ‘crisis’? What kind of paradigm shift do you expect?

GdB

The crisis is the inability of physicists and cosmologists to determine the nature of dark energy and dark matter which makes up 96% of the universe with present scientific and cosmological theories. Quantum field theory, Einstein’s cosmological constant and an exotic “fifth element”, quintessence have been proposed, but none of them are completely consistent with the cosmological evidence. I have written more about this in another thread, “God of the Gaps” in the philosophy section and you are welcome to refer to it.

That’s a difficult question. I expect our present notions of what is space, time, energy, matter, gravity and what is the universe itself (Is it holographic?) will have to be fundamentally changed in order to make sense of this strange enigmatic reality that dark energy and dark matter presents to us.

We shall not cease from exploration, and the end of all our exploring will be to arrive where we started and know the place for the first time.

T. S. Eliot

 Signature 

I am, therefore I think.

Profile
 
 
Posted: 20 November 2007 10:22 AM   [ Ignore ]   [ # 13 ]
Sr. Member
RankRankRankRankRankRankRankRankRankRank
Total Posts:  1823
Joined  2007-10-28
erasmusinfinity - 20 November 2007 09:25 AM
kkwan - 19 November 2007 08:54 AM

The 96/4% was computed from recent cosmological evidence, but science cannot yet understand what is the nature of the 96% of dark energy and matter and why they exist.

I’m fine with the point that we don’t know much.  After all, we’re only human.  I wouldn’t doubt that we are capable of understanding even less of the universe than 4%.  It just seems to me that reason and science are the only ways that we have to know anything at all.  Can you think of an alternative way of knowing anything that does not involve reason or science.

To me, it seems not embarrassing, but ennobling that we understand anything at all.

How about Theravada Buddhist meditation?

http://en.wikipedia.org/wiki/Ajahn_Brahm

Venerable Ajahn Brahmavamso Mahathera (known to most as Ajahn Brahm) was born Peter Betts in London, United Kingdom on August 7, 1951. He came from a working-class background, and won a scholarship to study Theoretical Physics at Cambridge University in the late 1960s. After graduating from Cambridge he taught in high school for one year before travelling to Thailand to become a monk and train with the Venerable Ajahn Chah Bodhinyana Mahathera.

It’s embarrassing for physics, the most advanced of the sciences, not for human endeavor of course. It is amazing that we, of the middle world with our middle world faculties, can understand so much of the very small and the very large with our mind/brain.

 Signature 

I am, therefore I think.

Profile
 
 
Posted: 20 November 2007 01:08 PM   [ Ignore ]   [ # 14 ]
Sr. Member
RankRankRankRankRankRankRankRankRankRank
Total Posts:  1214
Joined  2007-09-21

How about Theravada Buddhist meditation?

I do see value in meditation as a means of relaxing the mind and body, focusing one’s thoughts, etc.  How, do you reckon, does it allow us to know things?  I don’t see it.

kkwan - 20 November 2007 10:22 AM

It’s embarrassing for physics, the most advanced of the sciences,

I think that that’s OK.  After all, we’re only human.  Even the scientists.  Plus, it almost guarantees future employment for the scientists.  LOL

kkwan - 20 November 2007 10:22 AM

not for human endeavor of course.  It is amazing that we, of the middle world with our middle world faculties, can understand so much of the very small and the very large with our mind/brain.

Agreed.  It is truly amazing… wonderful… beautiful.

Profile
 
 
Posted: 20 November 2007 02:40 PM   [ Ignore ]   [ # 15 ]
Moderator
Avatar
RankRankRankRankRankRankRankRankRankRank
Total Posts:  4052
Joined  2006-11-28

As long as we’re quoting:

Man’s reach must ever exceed his grasp, else what’s a Heaven for?”

Robert Browning (Oops! I had remembered it as Milton. Time to quit writing here and go back to reading my literature!)

I think not knowing everything is one of the great reasons for living, and I don’t consider a big mystery science hasn’t figured out hyet to be an embarrassment. The only people who get worked up over what science doesn’t yet understand are those who prefer mystical or metaphysical explanations and enjoy claiming sciene can’t understand the universe as well as these approaches. Not my cup of tea.

[ Edited: 20 November 2007 08:18 PM by mckenzievmd ]
 Signature 

The SkeptVet
The SkeptVet Blog
Militant Agnostic: I don’t know, and neither do you!

Profile
 
 
   
1 of 6
1