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renormalised
04-09-2009, 03:09 PM
http://www.abc.net.au/science/articles/2009/05/11/2566814.htm

MOND...mon dieu:P:D

Robh
04-09-2009, 04:47 PM
Carl, thanks for the update.
The plot thickens ...
Just shows that one should never blindly take any theory as a fait accompli.
If the theory doesn't explain the observations then you've got to go back to the drawing board.

le nouveau MONDe :D

Regards, Rob

sjastro
05-09-2009, 07:42 AM
Rethink? Not according to this...........

http://www.nasa.gov/mission_pages/hubble/science/hst_img_20090312.html

Steven

renormalised
05-09-2009, 10:08 AM
That's still conjecture, Steven. They're using dark matter as an explanation for what they're seeing with those dwarf galaxies. We haven't a clue of two things here....1. What the blazes is dark matter, and 2. Does it even exist. Unless you have definitive evidence of its existence, all you can say about this is something is creating the influence that is keeping these galaxies together. What that is, we don't know. Saying something exists in theory and then proving its actual existence are two entirely different things. I think the theorists and such need to take a step back and not proclaim one way or the other what is influencing these galaxies until they have definitive proof, either way.

allan gould
05-09-2009, 11:22 AM
Personally I have a hard time trying to accept dark matter and dark energy. The simplest explanation for dark matter is that there is needed a modification of laws of gravity a la Newton. And this will lead to a better understanding of gravity at the quantum level, while for dark energy - forget it as there was a refutation of the whole idea of dark energy (need to find the paper) that easily refuted dark energy on the basis that from first principles their assumptions were wrong. Its initially stated that in space matter is evenly distributed. But clearly its not as seen from galaxy surveys where there are voids and clumps. So from first principles there initial statements are wrong. The paper i remember then calculated red shifts of galaxies through this clumpiness of the Universe and showed the extra redshift was due to the fact that space has extra clumped material that increased the redsift along the line of site to their exploding supernova. But of course this was ignored by main stream scientists that had a vested interest ie grants tied up to dark energy research. In my opimion the universe is simpler than all these bolt on epicycles that modern scientists are doing - its all to clumsy and inelegant.

sjastro
05-09-2009, 12:06 PM
Dark matter is a hypothesis not a theory. A hypothesis becomes a theory when it is supported by observation.

The same applies to MOND.

Steven

Screwdriverone
05-09-2009, 01:30 PM
Hmmmm, must have caused them to rethink the spelling too?

Garvity eh?

;)

Chris

Robh
05-09-2009, 02:33 PM
I agree about the dark energy hypothesis. I think it seems to much of an "on the fly" fix to observations interpreted as an accelerating expansion of the Universe. Even so, down the track, it could turn out to be right.
However, the dark matter fix is fairly plausible. I think it leads to a simpler mathematical explanation of the assumed "binding" forces required to hold galaxies together than the modified Newtonian equations required by MOND. Having said that, only further observations will establish which is correct- dark matter or MOND or, perhaps, something else.
Flexibility is the key to success!

Regards, Rob

avandonk
05-09-2009, 04:19 PM
Dark matter is simply all the socks lost in the wash since socks began.

Bert

renormalised
05-09-2009, 10:02 PM
My mistake....typo:P

renormalised
05-09-2009, 10:04 PM
The "ho-zone":D:P:D

Now we know:P:D

renormalised
05-09-2009, 10:07 PM
That's not what I meant...by saying something exists in theory meaning it exists only as a matter of conjecture. Basically, an educated guess.

I do know the difference between a hypothesis and a theory:P:D