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NASA Discovers "Dark Energy"


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#1 Rhys

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Posted 12 February 2003 - 12:02 PM

http://www.smh.com.a...4725732451.html

Quote

NASA is expected to announce this week that it has proved the existence of "dark energy", a cosmic force that counteracts gravity and will keep the universe expanding forever. The announcement will effectively demolish the theory that life will be wiped out in a "big crunch" when the universe collapses, and should end decades of academic dispute.

Energy that counteracts gravity?

Quote

As the universe expands, all the energy needed to keep the stars and galaxies alight will be used up. What will remain is a universe full of black holes, which after trillions of years will explode to leave nothing but dark energy.

Leaving nothing but black holes?

Where have I heard this before? :)

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#2 Rhea

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Posted 12 February 2003 - 07:25 PM

Hmmmm...let me think. :p
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#3 Uncle Sid

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Posted 12 February 2003 - 08:55 PM

Rhys, on Feb. 12 2003,13:02, said:

Leaving nothing but black holes?

Where have I heard this before? :)

Rhys

Well I guess we know who wins in the Andromeda Universe.  Looks like it's time to join up with the winning team.  

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#4 Kevin Street

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Posted 13 February 2003 - 02:08 AM

We welcome our new Enigmatic Overlords!  ;)

Yeah, that was pretty surprising. I'm taking a course in Astrophysics right now, and the instructor neglected to mention this Dark Energy stuff. (And she never mentioned that it might make up 65% of the universe either! ) 'Course, astrophysics is really trucking along right now. It's a great time to be in science!

"Feel the power of the dark side!"  :D

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#5 QueenTiye

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Posted 14 February 2003 - 02:02 PM

Wow! ... I'm going to have to go read up... but, um... so much for Trance's PPF!

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#6 Delvo

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Posted 14 February 2003 - 05:05 PM

As is often the case with science reporting, the implications were somewhat overstated. For one thing, the "cold death" idea of the universe's end, where it keeps expanding forever even after all the stars burn out, doesn't involve everything being turned into black holes; there's also cold free-floating matter, in the form of un-collapsed stars, planets, rocks, dust, and gas. Also, the existence of this one force really wouldn't dictate that end any more than what we already knew about the observed movements of objects in the sky would.

Gravity itself is not even entirely figured out yet, nevermind this force that's supposed to weaken it. In fact, over large distances like galactic diameters, gravity appears to be too strong for standard predictions if anything, not too weak; that's always been part of the evidence for "dark matter", but could also be interpretted in other ways, such as the "2" exponent in that famous force-of-gravity equation (where you divide the product of the masses by the square of the distance) actually being a variable instead of just a "2"...


#7 Christopher

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Posted 14 February 2003 - 05:57 PM

Delvo, on Feb. 14 2003,17:05, said:

Gravity itself is not even entirely figured out yet, nevermind this force that's supposed to weaken it. In fact, over large distances like galactic diameters, gravity appears to be too strong for standard predictions if anything, not too weak; that's always been part of the evidence for "dark matter", but could also be interpretted in other ways, such as the "2" exponent in that famous force-of-gravity equation (where you divide the product of the masses by the square of the distance) actually being a variable instead of just a "2"...
That's true, but the evidence for dark energy or something like it is observed over cosmic-scale, intergalactic distances.  Specifically, more distant galaxies seem to be receding faster than they should, as though there's some slight "antigravity" force accelerating the expansion of the universe.

That alternative explanation you're talking about is probably MOND, or Modified Newtonian Dynamics.  The Chandra X-ray Observatory recently gained observational data which are consistent with the cold dark matter theory and incompatible with MOND:

http://www1.msfc.nas...002/02-264.html

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