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No dark matter?
No dark matter?
An alternative theory has been proposed to dark matter and dark energy. Instead of the universe being dominated by said invisible components, it's actually gravity changing on the relevant scales.


Critics have slammed it, however it better predicts the relationship between a galaxies' rotation speed and its mass, not to mention actually addresses the "flat rotation curve" problem, one of the major unsolved problems in physics.
RE: No dark matter?
Is there an axiv.org link?
RE: No dark matter?
The theory has been around since the 1980s. It's not surprising that it could be made to predict reasonably well the galaxy rotation curve since that is precisely what it was explicitly crafted to predict. The problem with this theory is it hasn't yet acuurately predict anything it wasn't explicitly crafted to predict, as any theory with any fundamental basis in physical reality should be able to do.

RE: No dark matter?
The real problem with this seems to me to be that, as Chuck says, it fits the data by construction.

Incidentally, when Einstein was developing GR, there was a theory around the time about modified gravity too. The only real problem with Newtonian gravity at the time was that it incorrectly predicted the precession of the perihelion of Mercury. So the modification made was that instead of gravity going as the inverse square of the distance, it went as the inverse of the distance to the power of 2.000002 (maybe not the correct number of zeroes there, but you get the idea). This fitted the data quite well, but it's a horrible ad hoc "solution".

This idea to explain rotation curves seems like a similar kind of ad hoc solution to me.
Galileo was a man of science oppressed by the irrational and superstitious. Today, he is used by the irrational and superstitious who claim they are being oppressed by science - Mark Crislip
RE: No dark matter?
Has it made any acurate predictions?
or is it just reverse engineered to meet the facts?

You can fix ignorance, you can't fix stupid.

Tinkety Tonk and down with the Nazis.


RE: No dark matter?
This thread confuses and infuriates me!
RE: No dark matter?
(March 6, 2011 at 11:13 am)Skipper Wrote: This thread confuses and infuriates me!

Why? That strikes me as an odd reaction to this thread, can you elaborate?
RE: No dark matter?
It really only confuses me. The "infuriates" part was just a line from Futurama. haha
RE: No dark matter?
(March 7, 2011 at 7:57 am)Skipper Wrote: It really only confuses me. The "infuriates" part was just a line from Futurama. haha

I see, it is a confusing subject. The problem is that we don't have a good understanding of what gravity is and how it works. These two theories are basically speculation on how we could make the model work in cases were it doesn't currently work. I think we need to go back and look at the model, and try to figure out what gravity is and how it really works.
RE: No dark matter?
(March 6, 2011 at 11:12 am)downbeatplumb Wrote: Has it made any acurate predictions?
or is it just reverse engineered to meet the facts?

The latter.

Kinda like how relativity contributed that .00002 to the inverse distance squared law, or so it was thought.

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