1. If all heavy elements like silicates found in rocks, calcium, oxygen, nickel,
ID: 1769867 • Letter: 1
Question
1. If all heavy elements like silicates found in rocks, calcium, oxygen, nickel, gold, etc. were formed in massive stars and their explosions AND the Earth was made at about the same time as the Sun, then how did those heavy elements get in/on Earth and in us? (5 pts)
2. What are the two observed facts that Einstein based special relativity upon? Explain them in your own words. (4 pts)
3. What are the two observable weird things that occur at relativistic speeds? Describe how these properties change when you view someone in a fast rocket? How would these properties appear to that person in the rocket? How would the same properties appear to the person in the rocket looking at the person on Earth? (6 pts)
4. How is a gravitational redshift different from a Doppler shift? (5 pts)
Explanation / Answer
Problem 4)
Doppler shift: We've experienced the Doppler effect if weve ever had a train go past you and heard the whistle go to a lower pitch (corresponding to a longer wavelength for the sound wave) as the train moves away. The Doppler effect can happen for light waves too (though it can't be properly understood without knowing special relativity). It turns out that just like for sound waves, the wavelength of light emitted by an object that is moving away from you is longer when you measure it than it is when measured in the rest frame of the emitting object.
Gravitational redshift: It describes how gravity's effect on spacetime changes the wavelength of light moving through that spacetime. The classic example of the gravitational redshift has been observed on the earth; if we shine a light up to a tower and measure its wavelength when it is received as compared to its wavelength when emitted, we find that the wavelength has increased, and this is due to the fact that the gravitational field of the earth is stronger the closer you get to its surface, causing time to pass slower - or, "stretched" - near the surface and thereby affecting the frequency and hence the wavelength of the light.
The difference between the two (Doppler redshift and gravitational redshift) is this: in the case of a Doppler shift, the only thing that matters is the relative velocity of the emitting object when the light is emitted compared to that of the receiving object when the light is received. After the light is emitted, it doesn't matter what happens to the emitting object - it won't affect the wavelength of the light that is received. In the case of the cosmological redshift, however, the emitting object is expanding along with the rest of the universe, and if the rate of expansion changes between the time the light is emitted and the time it is received, that will affect the received wavelength. Basically, the cosmological redshift is a measure of the total "stretching" that the universe has undergone between the time the light was emitted and the time it was received.
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