Let’s see how you did! If you didn’t get a few of these, don’t let it stress you out – it just means you need to play with more experiments in this area. We’re all works in progress, and we have our entire lifetime to puzzle together the mysteries of the universe!
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Answers:
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1. This implies that there is something special about one reference frame over another. Relativity states that all reference frames are equal.
2. The two will return the same age but arrive younger than the Earthbound triplet.
3. The traveling person could take only minutes or second to make the trip, and an Earthbound observer would see the trip as taking just over 88 years. The traveler would arrive just over 88 years into the future at the same age as they left.
4. The traveling twin would have taken 20 years instead of 15 years for the trip, so their age difference would be only five years upon return.
5. From the runner’s point of view, the pole will reach the second door before the pole clears the first door. From the farmer’s point of view, the pole will reach the second door after it clears the first door. The events are not in the same order for both viewpoints. Yet both are right. These events are not simultaneous.
6. No. It is elsewhere in events that are too far away to influence any events occurring right now.
7. Since events can be different depending on your viewpoint, my past may not be the same as yours. You might see two lights switch on at the same time whereas I saw one light up before the other; hence our past experiences are different. Yet both are correct.
8. No. If two particles combine and annihilate each other (a positron and electron, for example), then the number of particles will decrease but the amount of energy generated may escape.
9. The larger rock has more inertia (resistance to motion) and takes longer to accelerate. And it probably is larger and will have more air drag as well, although this problem didn’t mention this effect.
10. The shortest distance on a sphere is the Great Circle Distance. Gravity curves spacetime and objects will now travel along a curve that takes the shortest possible line along this curved path.
11. I will see your clock running at a different rate than mine due to gravitational time dilation.
12. The escape speed is very slow compared to the speed of light.
13. Nothing. The moon does not care what shape the Earth is. It’s only responding to the mass of the Earth.
14. No, you would see the clock ticking by as usual as you passed the event horizon and drifted in for awhile, until you were stretched thin from the gravitational forces of the black hole and shredded at the subatomic level.
15. My reference frame is in uniform motion (constant speed and in a straight line) and thus just as good as the stationary observer at the airport. I observe nothing unusual going on in my reference frame. The laws of physics apply to my viewpoint just as well as any other reference frame in uniform motion.
16. There IS gravity in space, otherwise the planets would not orbit around the sun. The weightless the astronaut feels has to do with the orbit he takes around the Earth – the astronaut is not just ‘sitting’ out there in orbit, he’s traveling about 5 miles per second around the Earth, which keeps him in orbit. His travels at the same rate that the Earth is curving away from him. To simulate artificial gravity, he would need to be in a rotating space station.
17. Speed c is relative to all observers.
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