What observational evidence supports the galactic fountain model, which describes how gas cycles between the disk of the galaxy and regions high above the disk?
A) We see hot gas high above the region of the disk near our solar system, along with cool gas that appears to be raining down from the halo.
B) We have discovered a jet of ionized gas shooting out of the bulge of our galaxy.
C) We have discovered that the entire galactic disk is being uniformly "rained on" by cool gas coming from the halo.
D) We have observed a lot of water molecules in the interstellar medium.
A) We see hot gas high above the region of the disk near our solar system, along with cool gas that appears to be raining down from the halo.
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During the period each year when we see Mars undergoing apparent retrograde motion in our sky, what is really going on in space?
A) Mars is moving around the Sun in the opposite direction from which Earth is moving around the Sun. B) Earth and Mars are getting closer together. C) Earth is catching up with and passing by Mars in their respective orbits. D) Earth and Mars are on opposite sides of the Sun.
An object covers a distance of 8 meters in the first second of travel, another 8 meters during the next second, and 8 meters again during the third second. Its acceleration is
A) 0 m/s2. B) 5 m/s2. C) 8 m/s2. D) 24 m/s2.
Currently, most of the mass of the matter of the universe is believed to consist of:
A) baryonic matter, made up of protons and neutrons. B) tachyonic matter, travelling only faster than the speed of light. C) dark matter not made of protons and neutrons. D) dark energy. E) tiny but very numerous black holes.
Two sources of light illuminate a double slit simultaneously. One has wavelength 570 nm and the second has an unknown wavelength. The m = 5 bright fringe of the unknown wavelength overlaps the m = 4 bright fringe of the light of 570 nm wavelength
What is the unknown wavelength? A) 456 nm B) 326 nm C) 380 nm D) 713 nm