Gravity's Dark Side

Sincere apologies for posting a bad URL in my mini-article. The correct link is What is gravity?.

This whole dark matter business reminds me of the pre-Copernican and Keplerian days of epicycles and eccentrics. Grituitously convoluted mathematics and geometric models were needed to describe the motion of the planets through the sky, and the people of the time were blind to the truth due to an adherence to the long believed "perfection" of circular motion. Kepler saw through the nonsense, and proposed a much simpler, explanatory theory of planatory motion: elliptical orbit.

As stated in the article, dark matter is a "fudge factor," numbers being added to the data to make it fit the model. It seems to me that the model should be modified to fit the data. This is apparently what physicists are trying to do, but perhaps their dedication to the established relativity paradigm is blinding them. I say we stick to good old Occom and his razor, and give cosmological physics a much needed shave. We should search for a simplified theory that can explain our universe accurately and sensibly, even if it requires abandoning our much beloved and trusted Einsteinian physical model.

Quote from Goose's #5986: "As stated in the article, dark matter is a "fudge factor," numbers being added to the data to make it fit the model. It seems to me that the model should be modified to fit the data." I think you are a bit unkind to the cosmologists - their dark matter adds numbers to the model, not to the data!
That said, the relativistic "MOND" or "TeVeS" are very interesting, indeed. Although a bit empirical, it comes quite close to the measured data. But is empirical theories not just another "fudge factor"?

Alright, I admit I may have been a bit unfair, but I attribute this to my lack of experience with "dark matter" and cosmological physics in general. I'm still only a mechanical engineering student, so I can't know it all... yet.

I am, however, very interested in cosmology, dark matter, and physics / relativity in general. The thought of switching to a physics major has tempted me several times. Just to satiate my curiosity, does anyone know of any informative websites on dark matter, or other current problems facing cosmologists? Or about the MOND and TeVeS theories in more detail? I have a decent background in relativity and quantum physics thanks to classes and Brian Greene, so technical information doesnt daunt me (too much). Please let me know!

You can try my "engineering-spin" on cosmology as a starter. You will find it here.

Once you've looked at my "engineering-spin", you can try this - much more technically demanding!

Sorry, typo in url: I repeat it this.

One quick question.. is it "the "dark matter" thought to hold galaxies together is still nowhere to be found" or no evidence of its existence..?? if its the later case, there are evidence of its existence. Althought I'm very much interested in cosmology, I'm an electical and computer systems major, so spare me if I'm talking nonsence. but I saw this documentry "Stephen Hawkings Universe - Part 3 - Cosmic Alchemy", in that they show the tracks of an electron an the positron (which is the "dark matter" cousine of an electron) also when they meet how a photon is formed. The demostration was done in a cloud chamber, and images were reproduced, if I'm not wrong. But yes, it not really anywhere to be "found" or see, as they say.

There is only indirect evidence for dark matter, e.g. galaxy rotation, galaxy formation and gravitational lensing of quasars – the light is bent more than what the visible matter can achieve. There may one day be an acceptable theory that does not require dark matter, e.g. the tentative "relativistic MOND" or "TeVeS" theory referred to before.

BTW, the positron is not dark matter; it's anti-matter, which is proven to exist. Dark matter cannot be anti-matter; otherwise it would annihilate normal matter it comes in contact with. And as far as we can tell, if dark matter exists, it mingles freely with visible matter.

Each cubic meter of open space is being trespassed by a wide spectrum of electromagnetic waves, departing from low radio frequency through microwaves, infrared, light, ultraviolet, X-Rays, Gamma Rays up to cosmic rays, and that is energy, one of the two states of matter. . It is possible to calculate the amount of energy present at any time within a cubic meter of open space, regardless of where in the space, may be between the Moon and the Earth, or beyond Pluto, or at midway between the Sun and Alpfa Centaurus, or at midway between the Milky Way and Andromeda. . If the amount of energy present within a cubic meter of free space is E, then the equivalent mass can be calculated by . E = M*C^2 . Thus . M = E/C^2. . Then "M" is the "dark" or "transparent" matter; it is just the mass equivalent of the radiant energy available for free in open space, and this means that a large portion of universe matter is not in mass state but in radiant energy state . In fact a light beam can be deviated by a gravity field, and gravity is a reciprocal force, in this case between mass and energy, the two states of matter.

The short answer is: yes, radiation energy is present in 'empty' space and it has 'mass', but today it is so small that it can be ignored. It was only in the universe's extreme youth, with white-hot radiation present, that it was significant. More 'light' on the long answer can be found in a download available from The Friedmann Equation.

Dear Jorrie

The mass equivalent of all radiant energy available in open space is significant considering the following:

Power Of The Sun P = Energy/Time = 3.6E+25[W]
Radiated Energy each Second E = M*C^2 = 3.6E+25[J]
Speed of Light C = 3.00E+08[m/s]

Equivalent Mass Converted Into Radiation each Second M = E/C^2 = 4.00E+08[Kg/s]

The Sun has been converting mass into energy for some 4600E+6[Years]

Each Year has 365*24*3600[seconds]

The Sun is an average star in Milky Way, with 10^11 Stars

And God only knows the age of the Milky Way
And God only know haw many galaxies there are in the universe.

So the energy available in free space of Universe has a huge equivalent mass, because mass has been converted into radiation since some 13 billion years, and from many stars.

Its should be possible to measure the equivalent mass of all radiation contained into a sphere some 50000 light years radius around Milky Way subtracting the real mass of all stars, but Milky Way is just one among thousands or may be millions of galaxies.

Best regards from Chile

Hey, I am not an anonymous Coward, I repeat:

Dear Jorrie

The mass equivalent of all radiant energy available in open space is significant considering the following

Power Of The Sun P = Energy/Time = 3.6E+25[W]
Radiated Energy each Second E = M*C^2 = 3.6E+25[J]
Speed of Light C = 3.00E+08[m/s]

Equivalent Mass Converted Into Radiation each second M = E/C^2 = 4.00E+08[Kg/s]

The Sun has been converting mass into energy for some 4600E+6[Years]
Each Year has 365*24*3600[seconds]

The Sun is an average star in Milky Way, with 10^11 Stars
And God only knows the age of the Milky Way
And God only know haw many galaxies there are in the universe.

So the energy available in free space has a huge equivalent mass, because mass has been converted into radiation since some 13 billion years, and from many stars. Its should be possible to measure the equivalent mass of all radiation contained into a sphere some 50000 light years radius around Milky Way subtracting the real mass of all stars.

Best regards from Chile

Jaime Soto Figueroa
http://www.matharts.cl/

Greetings Jaime:

According to the best theory of the universe that we have, visible (i.e. radiating) matter makes up about 4% of the energy of the universe. Only a tiny fraction of that energy gets converted to radiation. Now spread that (tiny fraction) radiation energy over the immense volume of the observable universe. Contemplate the energy available per square meter, square kilometer, square light-year, or whatever. Further, divide that small amount (relatively speaking) by c^2 and you have the equivalent mass density of that radiation. You get my drift? It's tiny when compared to the mass density of the universe today!

Bets regards,

Jorrie

Conveniently M theory may have an answer to the ellucive dark matter as well as variable gravity. Virtual matter may fill the void.

Yes, there are 7 extra dimensions wherein dark matter may hide. It is the latest (unified) quantum-gravity theory, combining the 5 best string theories. But the jury is still out...

For those who wonder, the "M" in M-theory stands for "Magic, Mystery or Membrane, according to taste", says its creator, Ed Witten, as quoted in the PBS documentary based on Brian Greene's book "The Elegant Universe".