Dark matter's status as a mysterious and invisible lurker in the universe has frustrated scientists for years. Now, one hopes to solve the puzzle a different way: using a modified version of Newton's second law that would eliminate the need for dark matter altogether. Researchers in Brazil have devised an experiment that could put the modified Newtonian dynamics (MOND) to the test, New Scientist reports.
Much indirect evidence for dark matter -- supposedly 25 percent of the mass in the universe -- comes from observing its invisible gravitational effect on visible galaxies and their stars. Deep underground experiments on Earth have attempted to directly detect the weakly interacting particles (WIMPS) that scientists believe constitute dark matter.
But dark matter's existence is based on the assumption that Newton's second law of motion holds true at all physical scales. In 1981, Israeli physicist Mordehai Milgrom hypothesized that Newton's second law might change slightly at extremely small accelerations. That MOND proposal could in turn explain the irregularities astrophysicists have observed in the motion of galaxies and stars without the need for dark matter.
A team headed by Vitorio De Lorenci of the Federal University of Itajubá, Brazi devised an experiment that could finally try to directly test MOND. They discovered that certain points on a well-placed, precisely-controlled spinning disc can cancel out the acceleration of the Earth's rotation, its orbit around the sun, and the orbit of the sun around the galaxy's center.
Canceling out all those interfering accelerations would allow for a measuring device mounted on the disc's rim to work unimpeded. If Newton's second law holds as usual, the device should not detect any unusual force. But if MOND holds true, the device should feel a strange kick.
That would allow scientists to at least see if all forces act differently at small accelerations or not. But the spinning disc would not test another version of MOND that proposes only gravity is affected. Such an experiment would need to take place in space.
"Vitorio De Lorenci of the devised an experiment that could finally try to directly test MOND."
Of the who?
the modified Newtonian dynamics (MOND)
@chefboiaarni Vitorio De Lorenci of the Federal University of Itajubá, Brazil -- thanks for pointing that out
Perhaps a link to a page such as www.en.wikipedia.org/wiki/Newton's_laws_of_motion for those people that can't remember Which law was Newton's Second...
Interesting ideas though, although I don't really understand how you could cancel out the acceleration of the earth's rotation, the earth's orbit, and the sun's orbit...
I'm curious of a couple of things: Would the disk have to spin at thousands of revolutions per minute or even per second in the opposite rotation of the earth and would it be on the same axis as the earth or in a tangential configuration to the surface?
Just some food for thought.
centripetal acceleration = V^2/R
where v = linear velocity and R = radius
Pulling some number off of wikipedia and doing a little math I came up
Ac(orbit) = 5.979 * 10^-3 m/s
Ac(rotation) = 0.337 * 10^3 m/s
Acceleration due to gravity = g = 9.8 m/s
centripetal acceleration at earth's surface is very small which is a good thing. If it were significant compared to g then your effect weight would change depending on the time of day.
For a 1 meter disc to cancel out g it would have to spin at about 30 rmp.
Wow, this is fascinating indeed!
I personally look forward to this test with great hope. While I acknowledge the evidence for Dark Matter, it always worried me that so much "stuff" was missing in action. Kind of like the "ether". The time for MOND has come. Now if we could just do away with multiverses and strings.......
"Such an experiment would need to take place in space"
I'm curious about this statement since depending on the distance from the earth it may negate the need to compensate for its rotation. The other calculations were all based on the disc being on the earth. eh, I guess these guys have that all figured out already.
Anyway, I am hoping that they disprove the theory of Dark Matter. It never sat well with me as I could see it being a major problem for space travel if we cant see/detect it.
"Oops...just lost another ship in an undetected spot of DM."
"For a 1 meter disc to cancel out g it would have to spin at about 30 rmp."
All that work only to come up with a final rotational speed that has not been defined yet. Maybe you meant rpm?
wow cholin 3947 did you figure that one all on your own!? haha you had to "compute" the accleration due to gravity. what a poser. if you had taken any basic physics class you'd already know that it's 9.81 m/s^2......but if it makes you feel smart to "compute" it then go ahead!! hahaha
I never had too many issues with dark matter it's just undetected mass and some of it could be things like brown dwarfs and or even something like neutrinos actually have a very slight mass.
What bugs me is dark energy the whole thing just seems illogical even absurd.
All matter in universe is inside it's gravity field, so there is no empty space. Gravity is bulged around space stuff and concentrated around centers. More matter is compressed, higher is it's energy potential, so in that aspect, matter is also condensed empty space. Highest potential should be inside a black hole, but how about alternative theory. Let's suppose galaxy stuff around it acts like a Faraday cage.
In short, when stuff enters event horizon, it's accelerated due to gravity pressure. Particles starts to spin so fast they appear as they spin backwards, like antimatter. They pass trough a black hole, with electric field striped of and travel faster than light outside the galaxy, where gravity is weaker and there is enough empty space to decelerate, accelerating galaxy disc and pushing space apart. Same process is driving the sun, earth and also atoms. It could also be a source of a background radiation. It's a wild one, I know :)
BTW, can anybody explain why we can see perfectly straight lines and circles, if everything is moving?
wow, normally I would just ignore comments like that but your ignorance is appalling.
First of all you tried to sound smart but absolutely nothing you said makes any sense and you ended up looking pretty stupid. You just made up a bunch of garbage and put it in terrible, non-nonsensical sentences. Please never post again.
To answer your brilliant question; yes, the computer in front of you is moving extremely quickly around the sun but so are you so it cancels out. That's very basic logic.
O, and "perfectly straight lines" shows how little you know since all lines BY DEFINITION are straight!
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