The Twin Paradox - Questions

The Twin Paradox

































Two identical clocks, one on the ground and the other in an earth satellite are set to the same time as the satellite passes overhead. A year later, the clocks are read again. According to the earth clock, the satellite clock

(A) reads exactly the correct time.
(B) has gained one millisecond.
(C) has lost one millisecond.
(D) has gained ten days.

Hint: Don't calculate anything.
Only one answer makes sense.

Questions --- What this question is about
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Two identical clocks, one on the ground and the other in an earth satellite are set to the same time as the satellite passes overhead. A year later, the clocks are read again. According to the earth clock, the satellite clock

(A) reads exactly the correct time. --- No.

The moving clock will run slow,
so it can't have the correct time.



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Questions --- What this question is about
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Two identical clocks, one on the ground and the other in an earth satellite are set to the same time as the satellite passes overhead. A year later, the clocks are read again. According to the earth clock, the satellite clock

(B) has gained one millisecond. --- No.

In order to gain, the moving clock would have to run fast.




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Questions --- What this question is about
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Two identical clocks, one on the ground and the other in an earth satellite are set to the same time as the satellite passes overhead. A year later, the clocks are read again. According to the earth clock, the satellite clock

(C) has lost one millisecond. --- Yes.

The moving clock will run slower, so it loses a little.
(The amount is correct, by the way.)



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Two identical clocks, one on the ground and the other in an earth satellite are set to the same time as the satellite passes overhead. A year later, the clocks are read again. According to the earth clock, the satellite clock

(D) has gained ten days. --- No.

Impossible because it would require
the moving clock to run fast.



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The "Twin Paradox" is called a paradox because

(A) it seems to contradict common sense.
(B) there is something really wrong with it.
(C) the twins reach opposite conclusions.
(D) nothing like it actually occurs.


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The "Twin Paradox" is called a paradox because

(A) it seems to contradict common sense.
No. Everything about relativity
contradicts common sense. That is not
why it is called a paradox, however.

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The "Twin Paradox" is called a paradox because

(B) there is something really wrong with it.

No. There is actually nothing wrong with it.


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The "Twin Paradox" is called a paradox because

(C) the twins reach opposite conclusions.

Yes. Each twin sees
the other's clocks running slow.

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The "Twin Paradox" is called a paradox because

(D) nothing like it actually occurs.

No. It happens.


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In the twin paradox, the important difference between the reference frame of the stay-at-home twin and the reference frame of the traveling twin is that the traveling twin

(A) is moving while the other twin is not.
(B) must accelerate to leave the earth.
(C) must decelerate upon return to earth.
(D) must turn around at the destination.

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In the twin paradox, the important difference between the reference frame of the stay-at-home twin and the reference frame of the traveling twin is that the traveling twin

(A) is moving while the other twin is not. --- No.
Each twin is moving with respect to
the reference frame of the other.

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In the twin paradox, the important difference between the reference frame of the stay-at-home twin and the reference frame of the traveling twin is that the traveling twin

(B) must accelerate to leave the earth. --- No.

That is a difference but not the important one.

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In the twin paradox, the important difference between the reference frame of the stay-at-home twin and the reference frame of the traveling twin is that the traveling twin

(C) must decelerate upon return to earth. --- No.

That is a difference, but not the important one.

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Questions --- What this question is about
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In the twin paradox, the important difference between the reference frame of the stay-at-home twin and the reference frame of the traveling twin is that the traveling twin

(D) must turn around at the destination. --- Yes.
That is what causes her to use
two different inertial frames to describe the trip.

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Time dilation has been observed

(A) never.
(B) only near the speed of light.
(C) on jet planes and satellites.


Questions --- What this question is about
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Time dilation has been observed

(A) never. --- No.

It has been observed.

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Time dilation has been observed

(B) only near the speed of light. --- No.

It has been observed at ordinary speeds.

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Time dilation has been observed

(C) on jet planes and satellites. --- Yes.
Real clocks on jet planes and satellites
slow down just a little.

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