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# Solar Lights: Astronomy Homework Questions? (7/7/2011)

Hey everyone! I was wondering if any of you had any insight to these multiple choice questions. These are review for a test and I would like to be sure I am studying the correct answers. There are only four since I answered the rest of them but If you know just one or two, that’s fine as well! Any help would be appreciated. Thank you!

1. Even though no object with mass, and no information, can travel faster than the speed of light, in principle an astronaut could reach a star that is 500 light years away within the current average human life span. True or False?

2. According to the theory of special relativity, two electrons moving at close to the speed of light in opposite directions, that collide head-on, meet with a relative speed of:

a. almost twice the speed of light.

b. exactly the speed of light.

c. almost the speed of light.

d. much less than the speed of light but still super fast man!

3. Star clusters in our Milky Way galaxy have allowed us to deduce how stars evolve with time. This is because realizing that the stars in a star cluster are bound together by gravity, each cluster provides two useful properties that we can immediately conclude just from the fact that the cluster exists at all, and which we would not have if we just looked at a random bunch of stars in the sky. Which of the following lists one of these special properties?

a. All stars in a star cluster were formed at the same time.

b. All stars in a star cluster are like the Sun.

c. All stars in a cluster will die at the same time.

d. All stars in a star cluster have the same mass.

4. Suppose that you are on a nearby star and look at the Solar System. You happen to see the Sun’s brightness dimming as Jupiter transits across its disk. Given that Jupiter’s diameter is about 10 times smaller than the Sun’s diameter, how much fainter will the Sun become during this transit, compared to its normal brightness?

a. A factor 0.1 (so 10%).

b. A factor 0.01 (so 1%).

c. Only about one in a million.

d. There would be no effect on the Sun’s brightness.
Yep! I did have some guesses, I’ll list them here:
1. False
2. B
3. A
4. A or B

More Pages:

misslabeled July 7, 2011 at 11:23 am

I thought you just had one little question, not that you were looking for someone to do your homework for you. Did you read the material? Did you at least try yourself first?

Swim July 7, 2011 at 11:45 am

1. False. 500 years is 500 years.
2. C
3. A
4. B

I’m not absolutely sure about any of my answers as I have been out of touch with astronomy for 20 years now.

Good luck.

brew July 7, 2011 at 12:41 pm

!!! 1 could be true dude think about worm holes!!!

oklatonola July 7, 2011 at 1:34 pm

For number 1. it would be true for the astronaut on the space ship if it traveled close to the speed of light, but everyone else would have died while the astronaut was going to the star . It’s kind of a trick question, but if you UNDERSTAND relativity a little bit, it’s true for the astronaut. Relativity is slippery like that.

4. b

The inverse square law applies to luminosity too. 10^ 2 = 100 1/100 = 0.01

Edward Sharp July 7, 2011 at 2:19 pm

Question 1) Wormholes the size which could accomodate a human’s size do not exist, so this is, in principle, false. In the absence of these wishful “shortcuts”, it will take at least 500 years (or the “invention” of Warp Drive, whichever comes first).

Question 2) Drawing upon “ancient studies” and Wiki, wherein:

“Composition of velocities – velocities (and speeds) do not simply ‘add’, for example if a rocket is moving at 2⁄3 the speed of light relative to an observer, and the rocket fires a missile at 2⁄3 of the speed of light relative to the rocket, the missile does not exceed the speed of light relative to the observer. (In this example, the observer would see the missile travel with a speed of 12⁄13 the speed of light.)