- 3464 - GRAVITY - and the Atom? All the other forces are carried by a quantum bundle of energy. The Electromagnetic force is carried by photons. The Weak Nuclear force is carried by W-Z bosons. The Strong Nuclear force is carried by Gluons. But, the force of gravity is in theory continuous without any discrete quantum. As far as we can tell?
------------- 3464 - GRAVITY - and the Atom?
- Galileo started the study of gravity by dropping cannon balls of different weights off the top of the Leaning Tower of Pisa. Everyone expected the heavy ball to strike the ground first, but Galileo heard the two balls hit the ground at the same instant.
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- This concept that all weights fall at the same rate ( if not acted on by another force) was totally counterintuitive at the time, and for many people even today.
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- Actually that’s the story. Galileo for sure used inclined planes and water clocks to come to this conclusion about gravity. Today scientists is performing the same experiment but instead of using cannon balls they are using atoms. Will gravity work with the same rules with matter as small as an atom?
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- Gravity is directly proportional to the mass of two objects and inversely proportional to the distance between them.
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- The latest experiment launches rubidium atoms up a 10 meter vacuum shaft and measures the rate of decent when the atoms fall back down. Rubidium atoms are cooled to within a fraction of a degree of absolute zero and then hit by a laser pulse. Half the atoms accelerate quickly and half the atoms accelerate slowly.
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- Actually each individual atom is separated into two waves, one moving fast and the other moving slow. A second laser then slows down the fast wave and speeds up the slow wave. Both waves start to drop due to gravity.
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- The initial fast wave catches up to the slow wave as they pass by a detector. The combined wave creates an interference pattern. Whether the detector sees the fast wave or the slow wave depends on the phase of the wave.
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- If the force of gravity changes the interference pattern will shift slightly causing the detector to register a different proportion of fast and slow waves. According to the weird laws of quantum physics each rubidium atom wave is in two places at once.
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- When a wave interacts with itself after taking two different paths it produces a distinctive pattern of bands called “interference fringes“. Two different isotopes of rubidium 85 and rubidium 87 are used. Rubidium 87 has 2 more neutrons than rubidium 85 and is therefore heavier. These 2 atoms represent the two cannon balls of different weight.
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- The detector is an interferometer measuring the difference of phase of two very close waves. It is very high precision and a highly sensitive instrument. Triple shielding is needed to insulate the experiment from the Earth’s magnetic field. Massive pieces of lead are strategically placed to correct for variations in the Earth’s gravitational field.
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- Even a person walking around the lab would contaminate the experiment. Every possible source of error must be eliminated or calculated with extreme accuracy. In the final analysis we will learn if atoms fall at the same rate regardless of weight. Was Galileo right?
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- The goal is to verify equivalent gravity rates of acceleration to:
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--------------------------- 1 part in 1,000,000,000,000,000. ( 1 to 10^15).
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- Two other effects this will be looking for to verify the theory of Relativity: A slow moving object should feel a slightly different gravitational force than far fast-moving object. According to Relativity “mass increases at higher velocities“. Secondly, Earth’s gravity itself should gravitate, “the energy of Earth’s gravitation should produce a bit of its own gravity“.
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- The Theory of Relativity says it is a smooth continuous curvature of space-time. But, could gravity have a quantum force carrier we call the “Graviton‘? Maybe this experiments will find out?
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- The other forces work on some particles and not on others. Gravity is different. It works on everything, light, energy, even itself. Gravity is also different because it is 10^30 times weaker that the other forces.
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----------------------- That is a zero then decimal then 30 zeros and a 1
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----------------------- The force of gravity according to Newton = G*M*m/r^2
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----------------------- And, force = mass * acceleration, F = m*a.
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- If we set these two equations equal to each other the mass, m , cancels out. All that is left is the mass of the Earth, M
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------------------------- M = 5.97*10^24 kilograms
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-------------------------- Radius of the Earth = r = 6.38*10^6 meters
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------------------------- Gravitational Constant = G = 6.7*10^-11 m^3/sec^2*Kg
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---------------- The acceleration of gravity at the surface of the Earth = a = g = G*M/r^2
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------------------------- g = 9.8 meters /sec/sec
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------------------------- g = 32 feet /sec/sec
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- In 1971 Apollo 15 astronaut David Scott performed the Galileo experiment on the Moon, dropping a hammer and an eagle feather at the same time. Television video confirmed they both hit the surface at the same time.
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- The astronauts also left mirrors on the Moon . Lasers reflecting off these mirrors measure the Earth-Moon distance to millimeter precision. These lunar ranging tests have confirmed that the Earth and the Moon respond to the Sun’s gravitational force in identical ways, to within 1 part in 10^12. The above experiment is looking for 10^15, a thousand times more accurate.
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February 16, 2022 GRAVITY - and the atom 755 3462
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----------------------------- Thursday, February 17, 2022 ---------------------------
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