Briefly explain why an expanding universe implies a beginning (called a Big Bang)
What will be an ideal response?
The fact that the universe is expanding means the average distance between galaxies is growing, which implies that this average distance was smaller in the past. Extrapolating back in time, there must have been a time when the distance between galaxies (or their precursors) was zero, which must be the beginning of the universe.
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Density: A plastic block of dimensions 2.00 cm × 3.00 cm × 4.00 cm has a mass of 30.0 g. What is its density?
A. 0.80 g/cm3 B. 1.20 g/cm3 C. 1.25 g/cm3 D. 1.60 g/cm3
Earth's interior is warmed by ________ and Earth's surface is warmed by ________
A) radioactive processes; fusion in the Sun B) fission; fossil fuels C) volcanoes; solar energy D) terrestrial radiation; terrestrial radiation
The sum of two vectors of fixed magnitudes has its minimum magnitude when the angle between these vectors is
A) 0° B) 90° C) 270° D) 180° E) 360°
What effect does the formation of sea ice in polar regions have on the density of seawater?
What will be an ideal response?