Everywhere but in the vicinity of the earth.

 
Or:

 
90% of the Universe. Too bad that we are in the 10% that it does not occur in.

sbbbugsy ! Yeh ! you to. You'r right about Dark Matter, why don't we see some effect, after all we do live near a galaxy called the Milky Way. I sort of understand the Dark Energy aspect, because it is essentially the attribute of the cosmos, before the big bang started, it is thought to be a constant, where the other expansion attributes of the universe are varibles. The only answer i've received is we do not have instruments sensitive enough to detect Dark Matters effect on our planetary system. And the fact that Mr. Isaac Newton was born here.

how about the fact that some scientists just discovered a couple weeks ago that dark matter is more abundent between the galaxies AND in a web-like pattern.....this leads me to think that if they ask the right questions such as which direction is the inside of the ripple facing? ((( or ))) this will obviously lead us to the center and origin of our universe! just check out this link: http://news.yahoo.com/s/nm/20080520/sc_nm/space_matter_dc

Hi!

I don't think anyone knows what they are, but I think that Dark Matter is considered to be here on Earth, it just doesn't react to the ElectroMagnetic Force, so we can't detect it.

The Dark Matter halo of the Milky Way is about 10 times the size of the Milky Way.   The Distribution of this matter is required for the stars to remain in their current orbits around the supermassive black hole at the center of the galaxy.    So we are flying through Dark Matter right now....

Physicists hope that Dark Matter interacts via the Weak Force, thus the reason for their equipment deep in mine shafts...but it may only react via the Gravitational Force.   In which case their experiments will not find Dark Matter particles, even if they were there....

Dark Energy is a property of space, so as space expands, the total Dark Energy increases.....but nobody knows what that is either, just what the effect of it seems to be...

You can always tell if you are reading a Physics or Astronomy book written before 2000, they spend a chapter talking about the ONLY 3 ways the universe can end (and up pops the 4th way in 2000! lol)

James3D

 This may be a very amateur question but here goes anyway. It seems like almost anything i read on dark matter talks about it making up for the unexpected behavior of galaxies. Any calculation of kinetic energy based on observable mass falls short of explaining galactic motion. I wonder if mass is the only  factor included in these calculations. All bodies have an electromagnetic field. So aren't stars and galaxies essentially giant magnets? Could this explain the observed motion of the stars and galaxies?

Electromagnetism and gravity work on entirely different scales. Another way of saying that is "they have differing levels of effect at the same scale." So, gravity trumps electromagnetism on galactic scales. Electromagnetism trumps gravity on micro scales (atomic and molecular level scales).

 I agree, the forces of gravity and electromagnetism do work on very different scales but according to this article

http://www.ohiou.edu/news/01-02/183.HTML

magnetism does large things on large scales. The speck that is the earth has enough magnetism to align a compass. why cant a super massive black hole hold a few billion stars together? 

At very large scales, electromagnetic force only affects very small things (like gas and dust particles) ... not really massive things like stars and planets. Large scales imply large distances, so while an electromagnetic field has stronger effects at short distances, it has weaker effects at long distances.

A black hole is an even more extreme case. Remember that the mass of a black hole is what is responsible for most of its effects on local objects ... and that helps you understand that it is gravity that wins out on scales above the macro level.

One exception is jets. The spin of a rapidly rotating object generates a localized magnetic field that constricts due to the spin and can accelerate particles into a beam called a jet, which emanates from the poles of the object's spin axis. These streams can be very energetic due to the extreme velociites of the particles within it. The beams are, in effect, collimated and can have a stronger effect at a distance. Again, though, it's not the electromagnetism that has the effect at a distance, but the inertia of the particles that impinge on other objects at a distance.

Qapla1234:

The speck that is the earth has enough magnetism to align a compass. why cant a super massive black hole hold a few billion stars together? 

Again, notice the difference in scale implied by your example: The Earth may be a speck when compared to the Universe, but compared it a compass needle it is truly large. So, comparing the effects of gravity and magnetism at this scale, consider that while gravity doesn't affect which way the compass needle points, it is gravity which keeps the compass from floating away from the Earth. Compared to the Earth, the compass needle is, itself, a tiny speck.

So, it's not so much that electromagnetism has no effect, as that its effect is swamped by that of gravity at this scale.

And, back to black holes, a supermassive one can truly affect the motions of stars in its vicinity. But when you take the measure of "vicinity" you end up right back where you started: at local scales, electromagnetic effects can be more prominent, but at distant scales they are less prominent.

Hi Physics and Astronomy Fans!

It seems that many people seem to think that Gravity and ElectroMagnetism work on different scales.  That is true if you make certain assumptions, but when physicists and scientists make assumptions, they cannot see other alternatives....so let's take a closer look....

Actually, theoretically, Gravity and ElectroMagnetism work on the EXACT SAME scales!  And the ElectroMagnetic Force can be as high as 4 Million Trillion Trillion Trillion (4.2x10power24) Times as strong as the Gravitational Force, so maybe there is something to this question after all and should not be dismissed as easily as large force/small force... 

For 2 objects with the same mass and the same charge:

 F(g) = GMsquared/Dsquared

 F(em) = Qsquared/Dsquared

Where:

F(g) = Gravitational Force
F(em) = ElectroMagnetic Force
G = Gravitational Constant
D= Distance between the Centers of Each Object

Note that for BOTH forces, the Force gets lower as the Square of the Distance...showing that they DO work on the EXACT SAME scales.

In fact, the ElectroMagnetic Force is SO much stronger, that if we add 1 Million Tons of extra Positive Charge on the Sun, and just 3.5 Tons of extra Negative Charge (opposite charge) on the Earth, the Gravitational Force would be cancelled and we'd be heading for the center of the Sun!

Or if we add 1 million Tons of Positive Charge on the Sun, and 3.5 Tons of Positive Charge (same charge) on the Earth, we would Double the Size of Earth's orbit around the Sun!   Maybe this is something we can pull off when the Sun gets too hot!

That is just what we need for our Global Warming problems!  Just add a few pounds of extra charge on the Earth, and a few hundred pounds of the same charge on the Sun, and we could move a bit farther out from the sun and cool down!

But here is why everyone thinks that the ElectroMagnetic Force is no good at large distances...

Gravity is always attractive, but the ElectroMagnetic Charge can be 0, Positive or Negative.  Most larger things are made out of atoms, and atoms typically contain the same amount of Positive and Negative Charges, making the total Charge equal to Zero.   But atoms CAN be charged, and we know of ionized gas and gas clouds in space all over the place....so let's keep going.....

There are also giant magnetic field structures all around these stars, and around everything else that we've found, even neutron starts, pulsars, black holes, etc...

Now, Dark Matter is hypothesized to exist for many reasons.   One is that the rotation rate of the stars and the dust around galaxies moves too fast for the matter inside the galaxy to keep it in orbit.   If there would be a cloud of Dark Matter maybe 10x greater than the size of that galaxy and with around 5 times more mass, then the movements that we see would make sense.  Dark Matter can so far only be detected by gravitational means, so even though it is all around us, we can't feel or see it.   Most physicists hope that Dark Matter is weakly-interactive (responding to the Weak Nuclear Force) so that they may find it in their experimental detectors, but that is just an assumption on their part also.      

But if we did have some ElectroMagnetic Force build-up that was sufficiently strong to add to the Gravitational Calculations, it is hard to see how it could be distributed so uniformly, and how it could effect most normal matter, but could it look like what we see....maybe?   It wouldn't be noticeable on planetary scales, so it would be just like we see in our own Solar System.

But Dark Matter could even be Shadow-Matter from other dimensions of space or from different membranes in M-Theory...right now nobody knows, not even the experts.

The only way forward in science is to question all the old assumptions, that was the greatness of Einstein and many others.....so the Cosmic Mystery just keeps getting stranger and stranger......

James3D
replica3d.com

Yes, both forces work at the same scales. But what I said is that on micro scales electromagnetism overwhelms gravity, and at larger scales gravity overwhelms magnetism. There is a balance point somewhere between the cosmic and micro scales where the two operate at the same force on the same scale. It is a macro scale, but not much above micro.

For example, a strong electromagnet can lift a car body at a junkyard.

I don't know where you get the idea of measuring charge in units of tons, but it would take considerably more than a million tons of force to move the Earth to any noticeable degree.

Hi All!

Well.....your statement: 

"micro scales electromagnetism overwhelms gravity, and at larger scales gravity overwhelms magnetism"

ASUMMES that the space at the macroscale is electromagnetically neutral - which is what we think to be the case in our universe.  We all know that in our Universe the Nuclear Force rules at Nuclear distances, the ElectroMagnetic Force rules over Atomic Distances, and the Gravitational Force rules over Macro distances.....

The idea here is to try and think beyond these basic assumptions and see what happens.  

By 1 Million Tons of Charge and 3.5 Tons of Charge I mean Electrons for Negative Charge, and Positrons for Positive Charge.

The reason is that when you Maximize the Value Q/M (Charge/Mass), you get the biggest charge on the smallest piece of matter.   The smallest mass with biggest Negative Charge is the Electron, and for Positive Charge, it is the Positron.

 The Original article can be found in the great book (and one of my favorites): Asimov on Physics
(published by Avon Books).  Dr. Asimov even states that the math was checked by Linus Pauling and he found an error in the original numbers....he wouldn't tell Dr. Asimov where the error was, he had to find it himself! 

 Anyways, if you get the book, the math is very easy to follow.   It is just that the results are fairly cool....

Electron/Positron  systems don't exist in our universe.  We have Electron/Proton systems.  For these systems the ElectroMagnetic Force is only 2.3X10power39 greater than the Gravitational Force.

And btw.....I know you can't isolate tons or even pounds of charge (electrons and positrons), it would require more energy than we can create.....this is just a mathematical paper example (a thought-experiment) to see how much stronger the ElectroMagnetic Force is than the Gravitational Force.

James3D

James3D:

Hi All!

Well.....your statement: 

"micro scales electromagnetism overwhelms gravity, and at larger scales gravity overwhelms magnetism"

ASUMMES that the space at the macroscale is electromagnetically neutral - which is what we think to be the case in our universe. 

I made no such assumption. If we look at the solar system (per your example) the space throughout is permeated by electromagnetic fields, yet gravity rules overall.

... By 1 Million Tons of Charge and 3.5 Tons of Charge I mean Electrons for Negative Charge, and Positrons for Positive Charge.

I'm still confused. I assume you know that the Sun loses more mass than this every second, yet there are no dramatic shifts in planetary orbits (or even the orbits of asteroids and comets) due to this effect?

Hi ChipDataJeff and other Physics&Astronomy Fans!

ChipDataJeff, your points are well-taken!   I don't mean to be confusing, but I also get confused on these issues...

Yes, I do realize that the Sun has a huge electromagnetic field.    But I think the field itself is fairly neutral (+ and - virtual particles), it just has an effect on charged particles within the field.  I think the sun has an equal amount of positive and negative charge, so they cancel to zero.

And you are also correct about the sun losing more mass than this, I think it loses 6 million tons of (I guess neutral) mass per second!    That always blows my mind! 

Isaac Asimov's gedanken-experiment proposed adding 1 million tons of EXTRA charge of JUST positive or JUST negative particles, and adding an EXTRA 3.5 tons of JUST positive or JUST negative charge to the Earth... in order to make it respond to the extra charge on the sun.

If the sun had an extra imbalance of charge, but the nearby asteroids or planets didn't, they wouldn't be affected.  But if one of the asteroids or planets also had an imbalance of charge, its orbit should change.   We don''t see this happening so we know that these extra charge imbalances don't exist in our solar system...

The thought-experiment just shows how much bigger the one force is than the other by showing that a handful of "charged" mass can affect a much larger "gravitational" mass like the sun/earth system.

But the original question wondered about the role of hypothesizing Dark Matter to explain the rotation rates of stars and dust in galaxies, and we are not quite sure of all the things to be found in the centers and inner reaches of galaxies.    Until 10 years ago, people didn't even know that the galaxies had supermassive black holes in them, and now we have found relationships between the size of these supermassive black holes and the mass of the galaxy, and also the angles of the spiral arms.    

In fact, I have a question that I have never heard addressed, maybe you or someone else has thought about:

I have read that Dark Matter particles are moving slowly (cold dark matter) within this giant Dark Matter sphere around our galaxy (and all other galaxies).  To them it is just like empty space, they move around freely...they pass through the earth and sun like they are not there, similar to neutrinos but even more ghostly.

But what happens when they hit the Supermassive Black Hole? (or any other black hole for that matter?)   They can't be locked within the Event Horizon like ordinary matter would, or the black holes would eventually suck in all the Dark Matter, and the black hole would just increase in size shifting all the mass from the Dark Matter Cloud into the black hole's event horizon!

But if all of the Dark Matter mass from the Dark Matter Cloud were moved to the inside of the black hole, the distribution of matter would not be correct to explain the rotation rate of the stars and dust around the galaxy!   So this can't be happening!    Meaning Black Holes are not Black for Dark Matter!

The Standard Model does not predict Dark Matter or Dark Energy.  Even the "Cosmological Constant" of General Relativity was added by hand by Einstein to make sure the outward and inward forces on the universe matched so he could continue to believe in a static and unchanging universe, not because he thought there might be this "Dark Energy" related to empty space.

Einstein unfortunately firmly held on to his religious assumptions or he could have kept making even further great progress in Quantum Mechanics....he is often quoted as saying "God does not play dice", prompting one of his peers (I think it was Niels Bohr, who is Olivia-Newton John's grandfather) to finally counter-argue: Quit telling God what to do!

Since quantum mechanics is firmly based on probabilities, it seems more likely that God is big-time into playing dice and gambling!

In all seriousness though, I think that pursuing the "Dark Matter in a Black Hole" scenario might bring forth some insight into it's nature...but of all the books and articles I have read, this interaction is never mentioned or discussed...I wonder what that Feynman diagram looks like?

James3D