Why is the cosmic microwave background (CMB) so cold if the early Universe was so hot?
a. Enough time has passed for matter in the universe to release enough heat to cool down.
b. The CMB constantly interacts with atoms, which effectively cool down the photons.
c. The expansion of the Universe has redshifted those photons to an effectively cooler temperature.
d. Misleading; The big bang was initially hot but the CMB was released from cold material much later on.
c
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The pupil of the eye increases in size under which condition?
a. eye is focused on a distant object b. eye is focused on a nearby object c. object viewed is dimly illuminated d. object viewed is well illuminated
In a two-dimensional Cartesian system, the x-component of a vector is known, and the angle between vector and x-axis is known. Which operation is used to calculate the magnitude of the vector? (taken with respect to the x-component)
a. dividing by cosine b. dividing by sine c. multiplying by cosine d. multiplying by sine
What is one piece of evidence that some organelles like mitochondria and chloroplasts within eukaryotes used to be independent prokaryotes that were incorporated into eukaryotic cells?
A) the DNA inside organelles is not made of the same four bases as the DNA in the host cells B) organelles float around independently inside eukaryotic cells C) prokaryotes are seen incorporating into cells today D) organelles are very similar to present-day bacteria, suggesting a common ancestor
The matter field of a hydrogen atom could best be described as
A) a probability pattern. B) an electromagnetic wave. C) a cloud of photons. D) a collection of electrons.