TOPICS 1. From Newton’s Gravity to Einstein’s Spacetime
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TOPICS 1. From Newton’s Gravity to Einstein’s Spacetime 2. “Seeing” Spacetime with Gyroscopes 3. The Science Instrument in a Force-Free Environment ACTIVITIES •Assumptions about Gravity GRAVITY PROBE B: Examining Einstein’s Spacetime with Gyroscopes An Educator’s Guide
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GRAVITY PROBE B: Examining Einstein’s Spacetime with Gyroscopes An Educator’s Guide. TOPICS 1. From Newton’s Gravity to Einstein’s Spacetime 2. “Seeing” Spacetime with Gyroscopes 3. The Science Instrument in a Force-Free Environment ACTIVITIES - PowerPoint PPT Presentation
Transcript of TOPICS 1. From Newton’s Gravity to Einstein’s Spacetime
TOPICS1. From Newton’s Gravity to Einstein’s Spacetime
2. “Seeing” Spacetime with Gyroscopes
3. The Science Instrument in a Force-Free Environment
ACTIVITIES•Assumptions about Gravity•Equivalence Principle •Curved Spacetime Models•Frame-Dragging
GRAVITY PROBE B: Examining Einstein’s
Spacetime with Gyroscopes
An Educator’s Guide
Uncovering Assumptions about Gravity
1. What does the ball represent? The magnet? The magnetic field?
2. How does the ball “know” that the magnet is there? How does
the magnet “pull” the ball toward it?
3. In what ways does this model NOT accurately demonstrate Newton’s gravity? In what ways is gravity different than a magnetic force?
NO HYPOTHESIS
In the Principia (1687), Newton states that “there is a
power of gravity pertaining to all bodies, proportional
to the … quantities of matter which they contain.”
As the story goes, when Newton was questioned about
how his “power of gravity” transmitted from one body to
another, he responded, “I make no hypothesis.”
Which wagon is harder to push?
Which wagon hits first?
swimming swimming
poolpool
Microscopic Angles of GP-B
Geodetic effect ---------- 6600 milliarcseconds(ST curvature)
Frame-dragging ------------ 42 milliarcseconds
GP-B tolerance ------------- 0.5 milliarcseconds
Gyroscopic Performance
Orders of Magnitude
10 10 10 10 10 10 10 10-12-10 -14-8-6-4-20
Earth-based navigational
gyrosGP-B
gyroscopes
Drift Rate (degrees/hour)
Materials -- fused silica, coated with niobium
Diameter --- 1.5 inches
Sphericity -- < 0.3 millionths of an inch (40 atomic layers)
Homogeneity -- < 2 parts per million
Roundest Gyroscope in the World
Roundest Object in the Universe (Almost)
Mach's principle
Inertial effects of mass are not innate in a
body, but arise from its relation to the
totality of all other masses, i.e., to the
universe as a whole. Hence, the “local”
behavior of matter is influenced by the
“global” properties of the universe.
Why do gyroscope’s stay oriented? rotational inertia
Where does a gyroscope’s “inertia”
come from?
Ultra-Low Temperatures for SuperconductivityUltra-Low Temperatures for Superconductivity
273 Kelvin
Niobium = 9.25K
Lead = 4.15KMercury = 3.72K
Aluminum = 1.10KTungsten = 0.0019K
GP-B ProbeTemperature
10K
5K
0K
1.8K
METALS
