Homework Chapter 13 and Chapter 19 (Process of Science: Constancy of the Speed of Light)
Examine the fourth figure(Figure 4) , which shows Jackie with her spaceship engines on, so that she accelerates continuously. As she accelerates, Jackie would say that __________ and you would say that __________. Check two responses below, one for each of the two blanks in the question.
(Blank 1) the headlight beam is always racing away from her at c (Blank 2) her speed gets faster and faster but never quite as fast as the speed of the headlight beam Jackie always says the beam is racing away from her at c, because everyone always measures the same speed of light. You see Jackie going faster and faster as she accelerates, but because you must also agree that she is going slower than her headlight beam—and that the headlight beam is traveling at c—you can never see her reach the speed of light.
Examine the first figure(Figure 1) , in which you see Jackie's spaceship traveling at 1000 km/hr as she throws the baseball at a speed of 100 km/hr. How fast would you say the baseball is going?
1100 km/hr Before Jackie throws the ball, you will see it moving with her at a speed of 1000 km/hr. Therefore, because she throws it in the same direction that you see her moving, you will see the ball moving at 1000km/hr+100km/hr=1100km/hr.
Based on these thought experiments, what can you conclude?
Jackie can never reach or exceed the speed of light. The key point is this: Because everyone measures the same speed of light, no one can ever catch up with one's own light. Therefore, anyone else observing the traveler will see that traveler going slower than the traveler's light, which means slower than c.
Examine the third figure(Figure 3) , in which you see Jackie's spaceship traveling at 0.99c. This time, Jackie would say that a beam of light from the headlight is traveling at __________ and you would say that the beam of light is traveling at __________. Check two responses below, one for each of the two blanks in the question.
c - speed of light Even though Jackie is now traveling by you at 99% of the speed of light, both of you will still find that the light beam is traveling at the speed of light, c. This is a consequence of the fact that everyone always measures the same speed of light through space.
Examine the second figure(Figure 2) , in which you see Jackie's spaceship traveling at 1000 km/hr, with the ship's headlight on. According to special relativity, Jackie would say that a beam of light from the headlight is traveling at __________, and you would say that the beam of light is traveling at __________. Check two responses below, one for each of the two blanks in the question.
c - speed of light (both) A fundamental premise of relativity is that everyone always measures the same speed of light, c, no matter how the observer or the light source may be moving. Note that this makes light different from material objects such as baseballs (see Part A).
In science, it is now well accepted that the speed of light is always the same and therefore nothing can travel faster than light. These ideas gained acceptance primarily because __________.
they have been verified through actual observations and experiments In science, an idea is accepted only if it has been verified by observations or experiments. Observations and experiments have confirmed that the speed of light through space is always the same, and experiments in particle accelerators have shown that no matter how much subatomic particles are accelerated, they never quite reach the speed of light.
