Why do scientists assume that the early universe was much hotter and denser than the universe of today?
A) The fact that the universe is expanding implies that objects were closer together in the past, and compressing material makes it hotter and denser.
B) All objects begin their existence in a hot and dense state.
C) The fact that the universe is filled with stars and galaxies implies that matter must once have been hot to have made these objects.
D) Observations of distant galaxies show that they are much hotter than galaxies of today, suggesting that the whole universe was hotter in the past.
A) The fact that the universe is expanding implies that objects were closer together in the past, and compressing material makes it hotter and denser.
B) All objects begin their existence in a hot and dense state.
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a. absorption b. continuous c. emission d. All of the other choices are correct.
Compound Microscope: You have a choice between two lenses of focal lengths fa and fb, where fb = 2fa, to use as the objective lens in building a compound microscope. If the magnification you obtain using lens a is Ma, what will be the magnification when using lens b?
A. Mb = 2 Ma B. Mb = 4 Ma C. Mb = 8 Ma D. Mb = Ma/4 E. Mb = Ma/2
The light produced in the Sun's core is able to pass freely through the Sun.
Answer the following statement true (T) or false (F)
An exerciser of mass 90.0 kg walks up a flight of stairs that are 12.0 meter high. What is the energy of the exercise in Calories?
A. 8.55 B. 7.32 C. 4.66 D. 2.53 E. 1.85