About 99% by mass of Earth's atmosphere is composed of the two elements
a. nitrogen and oxygen.
b. oxygen and carbon dioxide.
c. oxygen and silicon.
d. hydrogen and helium.
a
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The reason why ancient astronomers thought that Earth could not be moving was because stars lacked any measurable parallax beyond one degree
a. True b. False Indicate whether the statement is true or false
If an extrasolar planet suddenly became larger in radius, but kept the same mass and orbit, what would change in the observed Doppler shift of the star?
A) Nothing. The radius of a planet does not affect the Doppler shift. B) The time between peaks in the velocity of the star would decrease. C) The peak velocity of the star would be faster. D) The shape of the velocity curve would become less symmetric. E) The lowest velocity of the star would be slower.
The radio source ________ is located in a place consistent with the center of our Galaxy
A) Cygnus X-1 B) 3C 273 C) 47 Tucanae D) M-8, the Lagoon Nebula E) Sgr A?
Two slits are illuminated with green light (? = 540 nm). The slits are 0.05 mm apart and the distance to the screen is 1.5 m. At what distance (in mm) from the central maximum on the screen is the average intensity 50% of the intensity of the central maximum?
A. 1 B. 3 C. 2 D. 4 E. 0.4