Suppose the Earth's axis has no tilt. Would we still have seasons?
Why or why not?
2

Imagine that you could drive your car in space at a constant speed of 116 km/hr. (In reality, the law of gravity would make driving through space at a constant speed all but impossible.)

(a) How long would it take to circle the Earth in low orbit? (Hint: Use the Earth's circumference of 40,087 km.)

Enter a number.

1 days
(b) Suppose you started driving from the Sun. How long would it take to reach Earth? Use the data in Table 1.1.

Table 1.1

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2 years
How long would it take to reach Uranus?

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3 years
(c) How long would it take to drive the 4.4 light years to Alpha Centauri? (Hint: You'll need to convert the distance to kilometers.)

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4 years
(d) The Voyager 2 spacecraft is traveling about 50,000 km/hr. At this speed, how long would it take to reach Alpha Centauri (if it were headed in the right direction, which it is not)?

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5 years

Suppose that, through a horrific act of an angry god (or a very powerful alien, if you prefer), all the mass in your body was suddenly converted into energy according to the formula E = mc². How much energy would be produced? Assume that your mass is 62 kg. (Hint: Multiply your mass in kilograms by c².)

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1 J
Compare this to the energy released by a 1 megaton hydrogen bomb (see Table 4.1).

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2 times 3 ---Select--- greater. lesser.

The Sun's average surface temperature is about 5,800 K. Use Wien's law to calculate the wavelength of peak thermal emission from the Sun.

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1 nm
What color does this wavelength correspond to in the visible light spectrum?
In light of your answer, why do you think the Sun appears white or yellow to our eyes?
3

Decide whether the following statement is sensible.
We can't see galaxies beyond the cosmological horizon because they are moving away from us faster than the speed of light.
Explain why it is or is not.
2