UPSC Prelims 2018 · GS Paper I
Question 62: Science and Technology
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 ?
AnswerUPSC’s answer is (d).
General Relativity treats gravity as the curvature of space-time produced by matter and energy, so matter warps the space-time around it. Light follows curved space-time and so is bent by gravity, as confirmed by the 1919 eclipse observations. Its field equations also describe a universe that can expand or contract; Einstein first added a cosmological constant to keep it static, and expansion was later confirmed by Hubble's observations. All three are predictions of the theory.
- 1. Gravity bends the path of light.
- 2. The field equations allow an expanding universe.
- 3. Matter and energy curve space-time.
How you could have got this
- If you were sure statement 2 is correct, (b) and (c) go: each of them leaves 2 out.
What you needed to know: The field equations allow an expanding universe.
- Then, if you were sure statement 3 is correct, (a) goes: it leaves 3 out.
What you needed to know: Matter and energy curve space-time.
Only (d) is left. You didn’t need statement 1.
Which options go is worked out from UPSC’s key and the options, not by a model.
Why each option is right or wrong
- (a) Incomplete: matter warping space-time is also a prediction.
- (b) Incomplete: light bending and expansion also follow from the theory.
- (c) Incomplete: an expanding universe also follows from the theory's equations.
- (d) Right: all three.
Answer: UPSC’s key. Explanation: written by UPSC Grade, not by UPSC.
Source: UPSC, Civil Services (Preliminary) Examination 2018, General Studies Paper I, Series A. The paper on upsc.gov.in.