Consider the following phenomena : 1. Light is affected by gravity. 2. The Universe is constantly expanding. 3. Matter warps its surrounding space-time. Which of the above is/are the prediction/predictions of Albert Einstein’s General Theory of Relativity, often discussed in media ?

(a) 1 and 2 only
(b) 3 only
(c) 1 and 3 only
(d) 1, 2 and 3 ✓ UPSC's answer

Why the answer is (d)

• General Relativity (1915) describes gravity as the curvature of space-time by mass and energy (3).

• A consequence is that light bends when passing near a massive body (1), confirmed by Eddington's 1919 eclipse observations.

• Einstein's field equations also implied a dynamic, non-static universe; Friedmann and Lemaître derived the expanding-universe solutions, confirmed by Hubble in 1929 (2) — the official key counts this as a prediction of the theory.

• Hence 1, 2 and 3, option (d).

Why the other options are wrong

(a) 1 and 2 only: Space-time warping is the core of General Relativity.
(b) 3 only: Light bending and expansion are also consequences of the theory.
(c) 1 and 3 only: The expanding universe also follows from Einstein's equations.

Asked in the GS Paper I of the UPSC Civil Services Preliminary Examination 2018, held on 3 June 2018. Question and answer key: Union Public Service Commission. Explanation: UPSC Answer Check.