If the Earth’s axis were perpendicular to the plane of its orbit, which one among the following would not have happened ?

If the Earth's axis were perpendicular to its orbital plane (zero obliquity), the Sun would always be directly overhead at the Equator [t1][t2]. This configuration would result in the Sun being permanently at the horizon for both the North and South Poles, rather than the North Pole lying in darkness [c2]. Under these conditions, every location on Earth would experience equal days and nights (12 hours each) throughout the entire year [c4][t9]. Furthermore, the primary cause of seasonal variation—the tilt of the axis—would be eliminated, leading to a lack of changing seasons [c1][c3][t8]. While options 2, 3, and 4 describe the actual consequences of a perpendicular axis, option 1 is incorrect because the North Pole would experience a permanent twilight/half-sun state on the horizon rather than constant darkness [c2][t9].

Sources

1. [1] Science-Class VII . NCERT(Revised ed 2025) > Chapter 12: Earth, Moon, and the Sun > 12.2.2 Seasons on the Earth > p. 177
2. [2] Science-Class VII . NCERT(Revised ed 2025) > Chapter 12: Earth, Moon, and the Sun > FASCINATING FACTS > p. 179
3. [3] Science-Class VII . NCERT(Revised ed 2025) > Chapter 12: Earth, Moon, and the Sun > In a Nutshell > p. 184
4. [4] Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 19: The Motions of The Earth and Their Effects > Equinox > p. 254
5. [5] https://www.weather.gov/cle/seasons
6. [6] https://education.nationalgeographic.org/resource/axis/