Question

Say you send out a radar pulse at T=-22h as registered by yourclock and receive a return reflection from an alien spacecraft atT=+12h, as registered by your clock. Is the spaceship inside oroutside the solar system? When did the spaceship reflect the radarpulse?

Answer 1

The time difference is

delta T = 12 h - (-22 h) = 34 h = 122400 s

Thus, as light travels 3E8 m/s, then the distance between you and the alien is

d = 3.67E12 m

The radius of the solar system is around 4.5E12 m. Thus, IT IS INSIDE THE SOLAR SYSTEM! [ANSWER]

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The spaceship reflected the impulse exactly in between 12h and -22 h, as light travels the same distance (hence, same time) back and forth. Thus,

T_reflect = [12 + (-22)]/2

= -5.0 h   [It reflected at t = -5 h, ANSWER]