What lines of evidence show that the Milky Way Galaxy is indeed a spiral galaxy?
What will be an ideal response?
The plane of the disk is obscured by dust, but it can be mapped using 21 cm. radiation. The central bulge can be observed at radio wavelengths, and it is clear that there is little significant structure above or below the disk, except the halo.
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What is the maximum theoretical efficiency possible for an engine operating between 
and 
A. 25%. B. 45%. C. 55%. D. 75%.
According to the atomic materialist philosophy, certain things are regarded as "real" and other things as merely "imaginary." Which of the following is [or are] regarded by this philosophy as real?
A) human emotions B) directly observable phenomena such as color and warmth C) atoms D) Both answers A and B are correct. E) None of the above are regarded as real by the atomic materialist philosophy.
A battery operating a large flashlight produces a current of 2 amperes in a light bulb that has a resistance of 4 ohms. The voltage of the battery is
a. 0.5 volts. b. 2 volts. c. 8 volts. d. none of the above.
Which of the following ranges corresponds to the shortest wavelengths?
a. infrasonic b. audible c. ultrasonic d. All have the same wavelengths.