How Far Are the Cosmic Ray and Photon at t=0s According to the Observer?

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SUMMARY

The discussion centers on calculating the distance between a cosmic ray and a photon as observed at t=0s, with the cosmic ray having a gamma factor of 10^10. The observer records the photon passing at t2=1.33x10^-8 seconds. Participants conclude that special relativity is not necessary for this specific calculation, as the distance can be determined using the formula distance = ct2, where c represents the speed of light. However, they note that subsequent parts of the problem may involve relativistic considerations due to the galaxy's motion relative to the cosmic ray.

PREREQUISITES
  • Understanding of basic physics concepts, particularly the speed of light (c).
  • Familiarity with the concept of gamma factor in special relativity.
  • Basic knowledge of time intervals and distance calculations.
  • Awareness of the implications of relativistic motion in astrophysics.
NEXT STEPS
  • Research the implications of gamma factors in special relativity.
  • Learn how to apply the formula distance = ct in various scenarios.
  • Explore the effects of relativistic motion on observations in astrophysics.
  • Investigate follow-up questions involving relative motion between cosmic entities.
USEFUL FOR

Students of physics, particularly those studying special relativity and astrophysics, as well as educators looking for practical examples of relativistic calculations.

roman15
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Homework Statement


A cosmic ray of gamma=10^10 is chased across the Milky Way by a photon. The cosmic ray passes an Observer at one edge of the galaxy and t=0s then the photon passes at t2=1.33x10^-8. These times are recorded by the Observer
How far away are the cosmic ray and photon at t=0s according to the observer?


Homework Equations





The Attempt at a Solution


Im not really seeing how to apply special relativity to this, wouldn't the distance between them just be ct2, because its asking according to the observer and from t=0 to t2, the distance traveled by the photon in that time would be the distance between them right?
 
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roman15 said:
Im not really seeing how to apply special relativity to this, wouldn't the distance between them just be ct2, because its asking according to the observer and from t=0 to t2, the distance traveled by the photon in that time would be the distance between them right?
Right. Relativity is not needed to answer this question. (I suspect that there are followup questions that might require special relativity.)
 
Doc Al said:
Right. Relativity is not needed to answer this question. (I suspect that there are followup questions that might require special relativity.)

haha you there are, the next couple of parts of the question deal with the galaxy moving relative to the cosmic ray
 

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