Relativity- stars and spacecraft.

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SUMMARY

The discussion centers on calculating the time and speed required for a spacecraft to make a return trip to a star located 450 light years from Earth, with a focus on relativistic effects. The minimum time for the round trip is established as 900 years, while the challenge lies in determining the necessary speed for the journey to be completed within 30 astronaut years. Participants discuss the use of time dilation and length contraction equations, specifically referencing gamma (γ) and the need to simplify the calculations by focusing solely on time dilation.

PREREQUISITES
  • Understanding of special relativity concepts, particularly time dilation and length contraction.
  • Familiarity with the equations involving gamma (γ) in relativistic physics.
  • Basic knowledge of light years as a unit of distance in astronomy.
  • Ability to solve simultaneous equations in physics contexts.
NEXT STEPS
  • Study the implications of time dilation in special relativity using real-world examples.
  • Learn how to apply the Lorentz transformation equations in various scenarios.
  • Research the concept of gamma (γ) and its calculation in relativistic contexts.
  • Explore practical applications of relativistic physics in space travel and astrophysics.
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Students and enthusiasts of physics, particularly those interested in astrophysics and the effects of relativity on space travel, as well as educators seeking to explain complex concepts in an accessible manner.

C.E
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1.a.) A star is 450 light years from earth.
i) what is the minimum time a spacecraft could make a return trip to this star?
ii)How fast should the spacecraft travel to make the journey in 30 astranaught years?
iii) What is the distance of eart to this star as measured by the astronauts on their 30 year journey?

my answer
1.(i). 900 years
(ii). I tried to do this by solving the following length contraction/ time dilation simultaneous equations:

(where g is gamma and L0=900, to=30)
Lg=lo
t=tog

and whatever I do I can't seem to eliminate enough variables, i.e. I always have a solution in both g and L or t and g or everything disappears and I get 0=0. Are these the right equations to start with? If so, what is going wrong?
 
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Welcome to PF!

Hi C.E! Welcome to PF! :smile:

(have a gamma: γ and try using the X2 tag just above the Reply box :wink:)
C.E said:
1.(i). 900 years

Yes.
(ii). I tried to do this by solving the following length contraction/ time dilation simultaneous equations:

(where g is gamma and L0=900, to=30)
Lg=lo
t=tog

You don't need length-contraction …

do everything in the "stationary" frame, and then use time dilation (only) to convert the time to astronaut time. :wink:
 

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