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Gravity | SciByte 1

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This week on SciByte …
We look at the results from Gravity Probe B and how they relate to Einstein’s predictions on mass, space, time and how they all interact with one another. We’ll also open up the guts of that crazy contraption, and discuss some of the impressive tech that made the whole experiment possible to begin with.

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Show Notes:

Gravity?

-Sir Issac Newton [Mathematician]
-1687 – His predictions predicted the existence of Neptune based on the motions of Uranus
-Mercury’s Orbit hower can NOT be explained by Newtonian math alone, but was resolved with Einsteins general theory of relativity in 1915
-Newtonian Calculations however still are accurate enough for most applications
-General Relativity – Albert Einstein [1907-1915] The observed gravitational attraction between masses results from their warping of space and time.
→ Space-Time is not flat, but can be stretched and warped by matter
-What this means, boiled down: Time moves slower under gravity

Gyroscope

-A device for measuring or maintaining orientation, based on the principles of conservation of angular momentum.
-Video : Gyroscope
-Video : Conservation of Angular Momentum : Spinning Skater

Gravity Probe A

-“A” confirmed the prediction that gravity slows the flow of time, and the observed effects matched the predicted effects to an accuracy of about 70 parts per million. [1976, and lasted <2hours]
-Used a hydrogen maser, a highly accurate frequency standard, to measure the rate change of a clock in lower gravity with high precision.

Gravity Probe B

-A star, a telescope, a spinning sphere [conceived in 1959, launched in 2004, decommissioned in Dec 2010]  [A Star, telescope, and space time]
-Gravity Probe B Cutaway
-Reference telescope sighted on IM Pegasi, a binary star in the constellation Pegasus
-Drag Free System
-Solar Radiation Pressure – Particles streaming away from Sun transferring momentum
-Atmospheric Drag [@624KM]
-Compensation done with helium boosters, full 6-degree motion (first ever)
-London moment gyroscopes
-A spinning superconductor generates a magnetic field whose axis lines up exactly with the spin axis of the gyroscopic rotor.
-Are housed in a dewar of superfluid helium @ a temperature of under 2 kelvins (−271 °C, −456 °F)
-A magnetometer determines the orientation of the generated field, which is interpolated to determine the axis of rotation.

** The pointer shifted by just 6,000 milliarcseconds — the width of a human hair as seen from 10 miles away
* At the time, the gyroscopes were the most nearly spherical objects ever made.

~ size of ping pong balls, they are perfectly round to within forty atoms
- Scaled to the size of the Earth, the elevation of the entire surface would vary by no more than 12 feet
* Measured changes in gyroscope the equivalent to an angular separation the width of a human hair viewed from 32 kilometers (20 miles) away over a one-year period. [0.5 milliarcseconds (1.4×10−7 degrees)]

Already Proven?

The Apollo astronauts left retro-reflector mirrors on the Moon, and laser ranging from Earth can now track their positions to millimeters. At that level of precision, the Moon’s motion in orbit has confirmed gravitomagnetism, the source of frame-dragging, to 0.15%, or 130 times better than GP-B.

Precision measurements of the Shapiro effect or gravitational time delay for light, most recently in 2002 by the Cassini space probe

Gravity – no uniform model for all scales

The laws of classical Newtonian physics remain accurate in predicting the behavior of the vast majority of large objects—of the order of the size of large molecules and bigger—at velocities much smaller than the velocity of light

Quantum mechanics

-By Newtonian Standards Atoms can’t exist
-Newtonian physics says that electrons would fall out of orbit into the nuclues
-Electron Orbits in actuality can only exist as very specific points
-Heisenburg Uncertainty principle – can’t know location AND speed

Black holes

-First conceptualized in 1783 by Henry Cavendish
-Infinite Density; Event Horizon [point of no return]

Dark Matter

-Matter that is inferred to exist from gravitational effects on visible matter and background radiation, but is undetectable by emitted or scattered electromagnetic radiation

Dark Energy

-Hypothetical form of energy that permeates all of space and tends to increase the rate of expansion of the universe
-Dark Matter/Dark Energy Estimates
-Some estimates state The Universe is made up of 23% Dark Matter; 72% Dark Energy; and Atoms a mere 4.6%

Additional Information :

SPACETIME: From the Greeks to Gravity Probe B
NASA : Gravity Probe B
Sky&Telescope : Gravity Probe B: Relatively Important?
PC Magazine : It Took More Than 50 Years, But NASA Proves That Einstein Was CorrectScientific American : Earth’s Mass and Motion Warps Spacetime as Einstein Said
engadget : NASA concludes Gravity Probe B space-time experiment
National Geographic : Einstein Theories Confirmed by NASA Gravity Probe
NASA Gravity Probe Confirms Two Einstein Theories
Wired : Floating Gyroscopes Vindicate Einstein
spaceRef : NASA’s Gravity Probe B Confirms Two Einstein Space-Time Theories
PCWorld:Experiment Confirms Space-Time Vortex Around Earth, Makes Our Heads Hurt
What’s 96 Percent of the Universe Made Of? Astronomers Don’t Know
YouTube | Lecture 1 | Modern Physics: Quantum Mechanics (Stanford)

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