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Why does the mud fly off the tires of a pickup traveling down the interstate? Copernicus had difficulty convincing his peers of the validity of his heliocentric model because if Earth were moving around the Sun, stellar parallax should have been observed, which is wasn’t. If Earth’s orbital radius about the Sun were magically doubled, would this make stellar parallax easier or harder to observe? Explain.

Why does the mud fly off the tires of a pickup traveling down the interstate? Copernicus had difficulty convincing his peers of the validity of his heliocentric

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Page 1: Why does the mud fly off the tires of a pickup traveling down the interstate? Copernicus had difficulty convincing his peers of the validity of his heliocentric

Why does the mud fly off the tires of a pickup traveling down the interstate?

Copernicus had difficulty convincing his peers of the validity of his heliocentric model because if Earth were moving around the Sun, stellar parallax should have been observed, which is wasn’t. If Earth’s orbital radius about the Sun were magically doubled, would this make stellar parallax easier or harder to observe? Explain.

Page 2: Why does the mud fly off the tires of a pickup traveling down the interstate? Copernicus had difficulty convincing his peers of the validity of his heliocentric

Why are there no hurricanes on the equator?

Page 3: Why does the mud fly off the tires of a pickup traveling down the interstate? Copernicus had difficulty convincing his peers of the validity of his heliocentric

Special Theory of Relativity

Page 4: Why does the mud fly off the tires of a pickup traveling down the interstate? Copernicus had difficulty convincing his peers of the validity of his heliocentric

Michelson-Morley Experiment

Page 5: Why does the mud fly off the tires of a pickup traveling down the interstate? Copernicus had difficulty convincing his peers of the validity of his heliocentric
Page 6: Why does the mud fly off the tires of a pickup traveling down the interstate? Copernicus had difficulty convincing his peers of the validity of his heliocentric

Einstein advanced the idea that the speed of light in free space is the same in all reference frames, an idea that was contrary to the classical ideas of space and time.

For the speed of light to be constant, the classical idea that space and time are independent on each other had to be rejected.

Page 7: Why does the mud fly off the tires of a pickup traveling down the interstate? Copernicus had difficulty convincing his peers of the validity of his heliocentric

Postulates of the Special Theory of Relativity

The idea of an absolute frame of reference was gone with the idea of stationary ether.

Page 8: Why does the mud fly off the tires of a pickup traveling down the interstate? Copernicus had difficulty convincing his peers of the validity of his heliocentric

First Postulate

All laws of nature are the same in all uniformly moving frames of reference.

Page 9: Why does the mud fly off the tires of a pickup traveling down the interstate? Copernicus had difficulty convincing his peers of the validity of his heliocentric

What would the light beam look if you traveled along beside it?

Page 10: Why does the mud fly off the tires of a pickup traveling down the interstate? Copernicus had difficulty convincing his peers of the validity of his heliocentric

Second Postulate

The speed of light in the free space has the same measured value for all observers, regardless of the motion of the source or the motion of the observer; that is, the speed of light is a constant.

Page 11: Why does the mud fly off the tires of a pickup traveling down the interstate? Copernicus had difficulty convincing his peers of the validity of his heliocentric

Simultaneity

Page 12: Why does the mud fly off the tires of a pickup traveling down the interstate? Copernicus had difficulty convincing his peers of the validity of his heliocentric

Two events that are simultaneous in one frame of reference need not be simultaneous in a frame of reference moving relative to the first frame.

Page 13: Why does the mud fly off the tires of a pickup traveling down the interstate? Copernicus had difficulty convincing his peers of the validity of his heliocentric

This non simultaneity of events in one frame that are simultaneous in another is a purely relativistic effect – a consequence of light always having the same speed for all observers.

Page 14: Why does the mud fly off the tires of a pickup traveling down the interstate? Copernicus had difficulty convincing his peers of the validity of his heliocentric

Question

Suppose that the observer standing on a planet sees a pair of lightning bolts simultaneously strike the front and rear ends of the high speed rocket ship compartment. Will the lightning strikes be simultaneous to an observer in the middle of the rocket ship compartment?

Page 15: Why does the mud fly off the tires of a pickup traveling down the interstate? Copernicus had difficulty convincing his peers of the validity of his heliocentric

Spacetime

Page 16: Why does the mud fly off the tires of a pickup traveling down the interstate? Copernicus had difficulty convincing his peers of the validity of his heliocentric

Two side-by side observers at rest relative to each other share the same reference frame. Both would agree on measurements of space and time intervals between given events, so we say they share the same realm of spacetime.

Page 17: Why does the mud fly off the tires of a pickup traveling down the interstate? Copernicus had difficulty convincing his peers of the validity of his heliocentric

space/time = SPACE/TIME=SPACE/TIME = c

Page 18: Why does the mud fly off the tires of a pickup traveling down the interstate? Copernicus had difficulty convincing his peers of the validity of his heliocentric

Time Dilation

Page 19: Why does the mud fly off the tires of a pickup traveling down the interstate? Copernicus had difficulty convincing his peers of the validity of his heliocentric
Page 20: Why does the mud fly off the tires of a pickup traveling down the interstate? Copernicus had difficulty convincing his peers of the validity of his heliocentric

Lorentz Factor,

2

21

1

cv

Page 21: Why does the mud fly off the tires of a pickup traveling down the interstate? Copernicus had difficulty convincing his peers of the validity of his heliocentric

If you are moving in a spaceship at a high speed relative to the Earth, would you notice a difference in your pulse rate? In the pulse rate of people back on the Earth?

Will observers A and B agree on measurements of time if A moves at half the speed of light relative to B? If both A and B move together at half the speed of light relative to the Earth?

Page 22: Why does the mud fly off the tires of a pickup traveling down the interstate? Copernicus had difficulty convincing his peers of the validity of his heliocentric

Space travelers on the way to colonize a planet orbiting a distant star decide to cook a “three-minute-egg”. Would a clock on Earth record the cooking time as less than, equal to or greater than 3 minutes? Why?

Page 23: Why does the mud fly off the tires of a pickup traveling down the interstate? Copernicus had difficulty convincing his peers of the validity of his heliocentric

Skip Parsec ventured into space without taking his watch. Wishing to cook a perfect “three-minutes-egg” on board his fast-moving ship, Skip is forced to rely on a clock on Earth. He cooks his egg for 3 minutes according to the Earth clock. Is his egg undercooked or overcooked?

Page 24: Why does the mud fly off the tires of a pickup traveling down the interstate? Copernicus had difficulty convincing his peers of the validity of his heliocentric

In an experiment to measure the lifetime of muons moving through the laboratory, scientists obtained an average value of 8 microseconds before a muon decayed into an electron and two neutrinos. If the muons were at rest in the laboratory, would they have a longer, a shorter, or the same average life? Why?