Each of the following is a prediction of the theory of relativity ...

[SAVANNAHHOOPER23]

Each of the following is a prediction of the theory of relativity (special or general). Which one is crucial to understanding how the Sun provides light and heat to Earth?
 
  A) Gravity is curvature of spacetime.
  B) E = mc2
  C) If you observe someone moving by you, you'll see his/her time running slow.
  D) Space is different for different observers. Time is different for different observers. Spacetime is the same for everyone.

Question 2

Why can one not use quasars to check the Hubble relation relating distances of objects to their velocity of recession?
 
  What will be an ideal response?

[billybob123]

Answer to Question 1

B

Answer to Question 2

The Hubble relation requires that the velocity of recession (or better, the redshift) and the distance to objects at cosmological distances be known. But astronomers do not know the distances to quasars except through using the Hubble relation. Quasars do not appear to be a standard candle, and most are variable in their luminosity over time as well.

[SAVANNAHHOOPER23]

Great answer, keep it coming

[ultraflyy23]

Thanks for the timely response, appreciate it