| Suppose that you wanted to measure the speed of light by putting a mirror on a distant mountain, setting off a camera flash, and measuring the time it takes the flash to reflect off the mirror and return to you, as shown in Figure 16-24 | Each orbit of Io takes 42 |
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| Earth travels the distance calculated in part a in 42 | How far does light travel in 13 s? Each orbit of Io takes 42 |
How many kilometers away would the mirror have to be? An astronomer is looking at the spectrum of a galaxy and finds that it has an oxygen spectral line of 525 nm, while the laboratory value is measured at 513 nm.
19| An astronomer is looking at the spectrum of a galaxy and finds that it has an oxygen spectral line of 525 nm, while the laboratory value is measured at 513 nm | Explain whether the galaxy is moving toward or away from Earth and how you know |
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| Calculate how fast the galaxy would be moving relative to Earth | Without instruments, a person can detect a time interval of about 0 |
Earth travels the distance calculated in part a in 42.