Calculating Spacetime Interval: Alpha & Beta Supernovae

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SUMMARY

The discussion focuses on calculating the time interval between two supernovae, Alpha and Beta, using the spacetime interval equation. The correct answer for the time between the explosions, as determined by the alien spacecraft, is 67.1 years. The equation utilized is c²t² - x² = c²(t')² - (x')², where it was clarified that light years inherently incorporate the speed of light, thus negating the need to multiply by c² when distances are measured in light years. This understanding is crucial for accurate calculations in relativistic physics.

PREREQUISITES
  • Understanding of spacetime interval equations
  • Familiarity with the concept of light years as a unit of distance
  • Basic knowledge of special relativity
  • Ability to manipulate algebraic equations
NEXT STEPS
  • Study the derivation and applications of the spacetime interval equation
  • Learn about the implications of special relativity on time dilation
  • Explore the concept of simultaneity in different reference frames
  • Investigate the relationship between distance and time in relativistic contexts
USEFUL FOR

Students of physics, astrophysicists, and anyone interested in the principles of special relativity and the calculations involved in astronomical events.

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Homework Statement
The star Alpha goes supernova. Ten years later and 100 ly away, as measured by astronomers in the galaxy, star Beta explodes.

An alien spacecraft passing through the galaxy finds that the distance between the two explosions is 120 ly. According to the aliens, what is the time between the explosions?

Relevant equations
c^2*t^2 - x^2 = c^2(t')^2 - (x')^2 The attempt at a solution
I tried using the spacetime interval equation but the distances are too small to see a difference and gives me a wrong answer. Then i did not include c^2 with the equation and i got the correct answer. Which is 67.1 years. I also tried to multiply x^2 and (x')^2 with c^2 and got the same answer. Is it under specific units, like light years, where we can neglect the c^2 or did I just used the wrong equation in the first place?
 
Physics news on Phys.org
Lightyear is the dist light travels in 1 year, so it's equal to c*1 year, and already the c is inside it, if you measure time in years. That's why you didn't have to multiply by c^2.
 

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