FIG. 2.10 A spacetime diagram showing the worldlines of various particles. P2.1 The spacetime diagram in figure 2.10 shows the worldlines of various particles moving along the x axis in space. Note that (as is conventional in spacetime dia- grams), I have calibrated the t and x axes in this diagram to have the same scales in the same units: this ensures that the worldline of a photon (which has a speed of 1) makes a 45° angle with each axis. For each labeled world- line, describe (1) where the particle is at time t = 0, (2) about how fast and in what direction (in the +x direction or the-x direction) the particle is moving at that time, and (3) whether the particle's speed subsequently increases or decreases as time passes. Also identify the one worldline that is physically impossible, and explain why. с5 m#₂-5 mAE5 mFIG. 2.10 A spacetime diagram showing the worldlines ofvarious particles.P2.1 The spacetime diagram in figure 2.10 shows theworldlines of various particles moving along the x axisin space. Note that (as is conventional in spacetime dia-grams), I have calibrated the t and x axes in this diagramto have the same scales in the same units: this ensuresthat the worldline of a photon (which has a speed of 1)makes a 45° angle with each axis. For each labeled world-line, describe (1) where the particle is at time t = 0, (2)about how fast and in what direction (in the +x directionor the-x direction) the particle is moving at that time, and(3) whether the particle's speed subsequently increases ordecreases as time passes. Also identify the one worldlinethat is physically impossible, and explain why.

A spacetime diagram showing the worldlines of various particles. P2.1 The spacetime diagram in figure 2.10 shows the worldlines of various particles moving along the x axis in space. Note that (as is conventional in spacetime dia- grams), I have calibrated the t and x axes in this diagram to have the same scales in the same units: this ensures that the worldline of a photon (which has a speed of 1) makes a 45° angle with each axis. For each labeled world- line, describe (1) where the particle is at time t = 0, (2) about how fast and in what direction (in the +x direction or the-x direction) the particle is moving at that time, and (3) whether the particle's speed subsequently increases or decreases as time passes. Also identify the one worldline that is physically impossible, and explain why.

A spacetime diagram showing the worldlines of various particles. P2.1 The spacetime diagram in figure 2.10 shows the worldlines of various particles moving along the x axis in space. Note that (as is conventional in spacetime dia- grams), I have calibrated the t and x axes in this diagram to have the same scales in the same units: this ensures that the worldline of a photon (which has a speed of 1) makes a 45° angle with each axis. For each labeled world- line, describe (1) where the particle is at time t = 0, (2) about how fast and in what direction (in the +x direction or the-x direction) the particle is moving at that time, and (3) whether the particle's speed subsequently increases or decreases as time passes. Also identify the one worldline that is physically impossible, and explain why.