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--------------- 1850 - Dark Matter? Do we have it right this time?
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- We can not see Dark Matter. We only believe it is there due to its effects on Gravity. We assume we know the laws of Gravity and the same laws exist throughout the Universe. If we modify the equations for gravity we can duplicate the results we see in observations. But, should we? Maybe we are missing mass in the equations?
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- This is not the first time our laws had to change in order to match observations. The laws of Gravity started with Isaac Newton in the 1600’s. Newton’s equations matched the motion of projectiles, rolling weights, pendulum clocks, the orbit on the Moon, even put 2 astronauts on the Moon in 1962.
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- Kepler’s laws were a special case of Newton’s laws and they matched the observed orbits of the known planets. Planets moved in closed ellipses with the Sun as one focus.
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- “ The area swept out by each planet as it orbited the Sun was the same in any given time interval at all points along the orbit. The period of the planet’s orbit, squared was proportional to the cube of the semi-major axis. “ See footnote (1) that illustrates this equation for the asteroid Ceres:
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----------------------- p^2 = a^3
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---------------------period^2 = radius ^3
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- When Uranus was discovered in 1781 observations showed that its orbit speed dipped below Gravity equations predictions. Was the law of Gravity needing modification? Or, is there Dark Matter out there that we do not have in these equations?
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- That “Dark Matter” turned out to be the planet Neptune that was discovered in 1846. It was discovered based on the projected influence of Gravity. The equations worked!
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- A similar problem occurred with the planet Mercury. Kepler’s law of perfect ellipses with the Sun as a focus needed modification to match observations. Ellipses precessed over time possibly caused by another unseen planet.
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- The undiscovered planet was even named, “Vulcan”. The precession was 43 seconds of arc per century, 0.012 degrees over 100 years. ( See footnote (2) to learn the calculations using pi).
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- Was the law of gravity wrong or was there an unseen planet, Vulcan?
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----------------------- F = G * m * M / r^2 , does it need modification?
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- In 1915 the new law modifying this equation came along. It was Einstein’s Theory of Relativity. With the new law for Gravity the warping of space-time explained how the math matched observation for the planet Mercury. But, space had to shorten and time had to slow with relative motion. Space and Time were not absolutes, they were relative to motion. Again the math was king!
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- In 1970’s this idealism in perfect math failed again. Vera Rubin measured velocity profiles of galaxy’s spiral discs using redshifts and blueshift data on either side of the spiraling galaxy. She expected the interior stars to be rotating faster, the outer stars more slowly. Vera’s data showed rotational speeds to be constant regardless of radius. This was totally contrary to how our Solar System works. The laws of Gravity for spiral galaxies meant the galaxies should be flying apart.
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- Again, were the laws of Gravity in need of more modification, or, was there unseen mass that needs to be added to these equations?
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- In 1981 the calculations were made showing the equations need only be changed fractions of nano-merters-per-second-squared to match Vera’s galaxy rotation curves.
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- For Dark Matter to match observation it would need to not be Normal Matter, made of protons, neutrons and electrons. It would need to be a large halo of mass surrounding the galaxy that did not interact with light. It didn’t stick to itself. It didn’t stick to normal matter, and it has never been discovered before now.
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- Modifying the laws of Gravity were a better match than calculations made with adding massive Dark Matter halos in the Einstein equations. At first.
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- Except, the gravity law equations failed with more observations on other distant galaxy clusters. Then, Gravitational Lensing was discovered where some unseen mass was bending starlight magnifying the background distant galaxies. Dark Matter could explain time dilation and gravitational redshifts. It cold explain the effect of Gravitational Lensing.
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- Either laws of physics need more modification or there is Dark Matter out there yet to be discovered. Collision less, cold Dark Matter now has a name, WIMPS, Weakly Interactive Massive Particles. There needs to be 5 times as much Dark Matter as visible matter.
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- We do not know if Dark Matter is just found in halos around galaxies It may be spread out in the space between galaxies/
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- More confirmation was found in the collision of two galaxy clusters. The gas inside the collision should heat up, slow down and emit X-rays. But, gravitational lensing showed the unseen matter surrounded the visible matter in the collision as the two masses separated in the collision. Dark Matter extends 10 to 20 times the size of visible regions of galaxies.
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- Today’s conclusion: . At least 90% of the matter in the Universe is Dark Matter. We still believe the laws of Gravity from Newton and Einstein to be correct. Now, it is up to astronomers to discover WIMPs and explain to us what Dark Matter really is. Then, when they get that done ,explaining 23% of the Universe, start working on Dark Energy that is 73% of the Universe.
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- More work to do. Stay tuned, an announcement will be made shortly.
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- The Sloan Digital Sky Survey measured and averaged 50 background galaxies using gravitational lensing of light piercing the halos of 30,000 foreground galaxies. (1999).
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- The averaged result showed that typical galaxy halos extend at least 1.3million lightyears into space from the luminous galactic disks. The Milky Way Galaxy is 100,000 lightyears across and contains 100 billion stars. That is the visible part. Using gravity to make this measurement and not just light the invisible galaxy is 1,000,000 lightyears across and weighs 5 trillion Solar Mass.
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- The Andromeda Galaxy is 2 million lightyears away. Using these metrics the 2 galaxies may actually be brushing up against each other.
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- What are the right answers? Do we need new math or do we discover new mass. Or, is the undiscovered energy acting like mass. Stay tuned.
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- Request these Reviews to learn more:
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- Dark Energy Reviews: 1800, 1749, 1516, 1499, 1290, 1147, 1083, 1084, 1085, 1047, 822 and nine more reviews.
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- Dark Matter Reviews: 1535, 1823, 1820, 1777, and twelve more reviews
- Footnote (1) The largest asteroid, Ceres, at one time was once thought to be a planet. It orbit’s the Sun at a distance of 2.77 AU.
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---------------------- a^3 = (2.77)^3 = 21.25
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---------------------- p^2 = 21.25
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---------------------- p = 4.6
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- The period for Ceres orbit around the Sun is 4.6 years.
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- Footnote (2) The calculations using the number pi: In 1424 Jamshid al-Kashi, a Persian astronomer, calculated pi to 17 digits. Today NASA only uses pi calculated to 15 digits, 3.141592653589793. Is this accurate enough to send a spacecraft across the Solar System? Voyager I is 12.5 billion miles away. If we drew a circle with that radius and used this value of pi the circumference would be 78 billion miles. How much of an error do we get cutting off pi at 15 decimal points. Do the calculation to satisfy yourself. But, the answer is you could be off by 1.5 inches. 78 billion miles around and off by 1.5 inches. Close enough for government work.
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----- 707-536-3272 ---------------- Sunday, April 3, 2016 -----
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