What took us so long? Only in 1998 did astronomers discover we had been missing nearly three quarters of the contents of the universe, the so-called dark energy--an unknown form of energy that surrounds each of us, tugging at us ever so slightly, holding the fate of the cosmos in its grip, but to which we are almost totally blind. Some researchers, to be sure, had anticipated that such energy existed, but even they will tell you that its detection ranks among the most revolutionary discoveries in 20th-century cosmology. Not only does dark energy appear to make up the bulk of the universe, but its existence, if it stands the test of time, will probably require the development of new theories of physics.

Scientists are just starting the long process of figuring out what dark energy is and what its implications are. One realization has already sunk in: although dark energy betrayed its existence through its effect on the universe as a whole, it may also shape the evolution of the universe's inhabitants--stars, galaxies, galaxy clusters. Astronomers may have been staring at its handiwork for decades without realizing it.

This article was originally published with the title The Universe's Invisible Hand.

6 Comments

1. 1. ebcordon 10:27 PM 7/19/08

   I thoroughly enjoyed reading this article. Then totally stumbled when a UK scientist used "close proximity". Totally redundant. I have heard of proximity fuses; but never a 'close proximity fuse'.

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2. 2. MSag1 03:17 PM 7/27/08

   Lets see:
   Start with a problem that arises due to an assumption (the Hubble constant) that is based on an assumption about an assumed property of an astronomical object (Cepheid variable)
   
   Then make up something magic (Dark Matter = magic-1) that makes the original assumption (the Hubble constant) fit with other evidence to give us the answer we want (age of the Universe between 12-14 Gyr).
   
   Then, when evidence comes along that indicates that magic-1 points us in the wrong direction make up magic-2 (Dark Energy) to counteract magic-1.
   
   Since we are better experienced with magic due to working with magic-1 for a while, make magic-2 have additional magical properties that it can change its form and effect depending on where it happens to be in the universe. We must, after all, be careful that our modern concepts of Dark Matter and Dark Energy are not confused with the old quaintly misguided idea of the aether.
   
   Yes, these are magical times for cosmology, although one might say they are very dark days for scientific work.
   

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3. 3. joseph2237 05:18 PM 7/27/08

   How about an alternate version.
   The Big Bank lasted a fraction of a second.
   Inflation lasted some 300K years.
   Then the "transition occurred" i.e. gravity kicked in big time and the universe has been collapseing ever since.
   Speed and preception are relative. If you are in a car doing 40MPH and everyone else is doing 100 MPH you would "assume" you are expanding slower than them.`
   We may very well be headed for a cosmic brick wall in a few (?) billion years. Have no fear we'll just "assume a n escape plan".

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4. 4. Raybron 06:11 AM 1/25/09

   I am just a person that admires and have cosmology as my favorite reading and thinking object. Universe...is a universe, and the rest is just minor parts of it. If we take a simple rational of learning principals steps: General to specific, s�mple to complex, and concrete to abstract, as a base, we - the not scientific class or professional people might also have the right to "guess just using "deductive logic" - wtihout responsability of making mistakes, or people laughing at us. No problem. So I woul like to "kick out the following rational, just to know if there is any theory already in that direction. After all, towsends of teories never reach us:
   "Is it possible to conceve, to have as a theory, that all the - Universe teasue - by its enormous weigh, pressures, mass volume, in a speeding up & slowing down process is because the total, complete universe, with all its laws, materials, all forces existing, HAS AN SPHERICAL FORM? IN WHICH ALL THE TESUE (LIKE A BLANKET) COVERS THE "SURFASE", WITH ALL THE GALAXIES MOVING, CRASHING, PUSHING, FORMING NEW GALAXIES...AND AN INSIDE (BLACK HOLE) OF "BLACK ENEGY AND BLACK SPACE" EXISTS AS A "VECTOR RESULTANT OF THE ENERGY MOVEMENTS, CHOCKS, IN A "INSIDE - DOWN" (FIGURATIVE WE KNOW UNIVERSE HAS NO UP, SIDE OR DOW SIDES) WHERE ALSO THERE ARE GALAXIES, ORBITING, CHOCKING, AND BEING BORNED, AS THE "SKIN OF THE GLOBAL SPHERICAL MAIN PART OF THE UNIVERSE?
   AS A LOGICAL FORM PREDOMINANT IN ALL UNIVERSE, BY EXCLUSION, WE HAVE AS PREDOMINANT GALAXIES AND ATOMIC SCIENCE KNOW (MICRO AND MACRO UNIVERSES) PATTERN: NO LINES, NO SQUARES, NO TRIANGLES, NO EGGS FORMS, OR IRREGULAR FORMS. THE PREDOMINANT IS ALWAYS : THE SPHERE!!! WHY THE ORIGIN COULN NOT BE TAKEN AS BASIC THEORY OT BUILD UP A RATIONAL ...A SPHERE?
   I HAVE AN INTERPRETATION OF LOGICAL CONCLUSION - COMPLETELY IGNORANT, WITHOUT ANY SCIENTIFIC KNOWLEDGE, OR CULTURAL EDUCATION, I AM JUST A NORMAL PERSON THAT LIKES TO READ ABOUT AND IMAGINE ABOUT...THE UNIVERSE : OUR ORIGINAL AND FINAL FRONTIER!
   I SEE 2 SCENARIES, 2 DIMENSIONS INTERACTION MOUVEMENTS:
   1- LIKE AN APPLE ALL THE GALAXIES MOVING SHOCKING, WITH INTERACTION FORCES AND PHISICS LAWS FLOWING LIKE A "TESSUE BLANKET" AND THE GRAVITY, BLACK ENERGY, BLACK MATTER, AND ALL THE DIFFERENT MATERIALS MOVING - LINKID BY ALLTHIS GRAVITY AND ELETROMAGNETIC FORCES, ETC.;
   2- THE OUT SIDE "TESSUE" SHOCKING, RESULTANT FOURCES GETS TO THE INNER SPACE, AS AN INSIDE PART OF THE APPLE, WHERE ANOTHER EFFECTS, FOURCES, HAVE THE SAME CARACTERISTICS AS THE "APPLE SKIN UNIVERSE TESSUE", AS A "TROUBLE WATER"

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5. 5. Martin Urban 02:21 PM 4/18/09

   The article says in paragraph 3: "Dark energy, unlike matter, does not clump in some places more than others; by its very nature, it is spread smoothly everywhere. Whatever the location--be it in your kitchen or in intergalactic space--it has the same density, about 10-26 kilogram per cubic meter, equivalent to a handful of hydrogen atoms." Given this, any mass in the local region will be dominated by local gravity that will counter the effects of dark energy, rendering the "big rip" impossible. Over time we will become more isolated, but will not be torn apart. The eventual fate of the cosmos is that all regions of our known universe will decay into a state of maximum entropy indistinguishable from all other regions.

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6. 6. R.Blakely 12:56 AM 3/31/11

   Redshift may be due to photon gravity. Since photons are affected by gravity, gravity affects photons. As a beam of photons travels for decades thru space the photons attract each other as they gradually diverge, and so they lose energy. Therefore the universe may not be expanding. Thus, dark energy is only a dream.
   

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