You observe a distant galaxy. You find that a spectral line of hydrogen that is shifted from its normal location in the visible part of the spectrum into the infrared part of the spectrum. What can you conclude?
A) The galaxy is moving away from you.
B) The galaxy is moving towards you.
C) The galaxy has very weak gravity.
D) The galaxy is made purely of hydrogen.
A
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A light ray, traveling obliquely to a concave mirror's axis, crosses the axis at the mirror's center of curvature before striking the mirror's surface. After reflection, this ray
A) travels parallel to the mirror's axis. B) travels at right angles to the mirror's axis. C) passes through the mirror's center of curvature. D) passes through the mirror's focal point. E) passes through the axis midway between the mirror's focal point and center of curvature.
Which of the following explains why the Sun appears to move gradually eastward along the path called the ecliptic on the celestial sphere?
A) Earth rotates once each day. B) Earth orbits the Sun once each year. C) The direction of Earth's axis in space precesses with a period of about 26,000 years. D) Stars appear to move randomly relative to our Sun in the local solar neighborhood. E) The universe is expanding.
Which of the following statements is an explanation, not an observation?
A) Stars can shine brightly for millions of years. B) Stars shine with energy generated by nuclear fusion in their cores. C) More distant galaxies are moving away from us faster than nearby galaxies. D) All planets orbit the Sun in the same direction and in nearly the same plane.
You're in a fast-moving train traveling at constant velocity. If you jump straight up you land
A) slightly ahead of your original position. B) at your original position. C) slightly behind your original position.