In what sense are telescopes "time machines" that allow us to study the formation and evolution of galaxies?
What will be an ideal response?
Answer: Telescopes see objects as they were when the light left them. For distant objects, this "lookback time" can be billions of years, which means in some cases we can literally see galaxies in the process of formation. Moreover, by looking to different distances (lookback times), we see other galaxies in various stages of life between formation and the present day.
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The Sun causes tides on the Earth in addition to the Moon.
Answer the following statement true (T) or false (F)
Answer the following questions for projectile motion on level ground assuming negligible air resistance (the initial angle being neither 0º nor 90º: (a) Is the acceleration ever zero? (b) Is the acceleration ever in the same direction as a component of velocity? (c) Is the acceleration ever opposite in direction to a component of velocity?
A. (a) No, (b) No, when the projectile is coming down, (c) No, on way up, because the acceleration is always downward throughout the satellite trip. B. (a) No, (b) Yes, when the projectile is coming down, (c) Yes, on way up, because the acceleration is always downward throughout the satellite trip. C. (a) Yes, (b) No, when the projectile is coming down, (c) Yes, on way up, because the acceleration is always downward throughout the satellite trip.
Giant irregulars are the most massive of all known galaxies
Indicate whether the statement is true or false
The three colors that comprise the image on a TV screen are
A) red, blue, and yellow. B) red, blue, and green. C) yellow, blue, and green. D) magenta, cyan, and yellow. E) red, green, and yellow.