Introduction to Earth & Universe- 1 - UPSC Geography Free MCQ Test

Only two

Big Bang Theory: This is the standard cosmological model in which the universe expanded from an initially hot, dense state. Observational evidence includes the galaxy recession described by Hubble's law, the discovery of the cosmic microwave background (CMB) and the predictions of primordial nucleosynthesis. Current estimates place the age of the universe at about 13.8 billion years.

Steady-state theory: Introduced by Hermann Bondi, Thomas Gold and Fred Hoyle in 1948, this model proposed that the universe is expanding but maintains a constant mean density through the continuous creation of matter, implying no beginning or end. It is a cosmological theory about the large-scale origin/existence of the universe, but it was effectively ruled out by observations such as the CMB and evolving galaxy populations.

Giant-impact (Big Splat) hypothesis: This explains the formation of the Moon by a collision between the proto-Earth and a Mars-sized body (often called Theia), producing debris that coalesced into the Moon roughly 4.5 billion years ago. It concerns the formation of the Earth-Moon system (a planetary event), not the origin of the universe.

Because the first two entries are cosmological models about the universe while the third is a planetary formation hypothesis, exactly two of the listed theories pertain to the origin/existence of the universe.

Both 1 and 2

Both statements are correct. The two planet classes differ fundamentally in composition and thermal environment: Terrestrial planets are small, dense and rocky, while Jovian planets are large with extensive gaseous envelopes.

Jovian planets possess massive atmospheres dominated by hydrogen and helium, with additional volatiles (methane, ammonia, water) and cloud particles; they also have associated dust in their ring systems and atmospheric aerosols. This contrasts with Terrestrial planets, which have comparatively thin atmospheres composed mainly of gases like nitrogen, oxygen or carbon dioxide and lack the extensive gaseous envelopes of the giants.

The temperature difference arises from location and energy input: the inner, closer to the Sun terrestrial planets receive much more solar heating than the distant gas giants, so they are generally warmer. In addition, conditions in the inner protoplanetary disk were too hot for light gases to condense, and the combination of stronger solar wind and lower planetary escape velocity for the smaller rocky worlds prevented them from retaining large amounts of primordial hydrogen and helium. The gas giants formed farther out where temperatures were lower and their higher masses allowed them to capture and hold large gaseous envelopes.

Therefore, the first statement about atmospheres (significant amounts of gas and dust on Jovian planets) and the second statement about relative warmth (terrestrial planets being warmer) are both correct.

1, 2 and 3

Statement 1 - True. Because Earth's axial tilt (obliquity) of about 23.5° with respect to its orbital plane changes the Sun's apparent path across the sky during the year, the length of daylight at a given latitude varies with season. The effect grows with latitude; beyond the polar circles (≈ 66.5° N and S) it produces continuous daylight or darkness around the solstices.

Statement 2 - True. The same axial tilt makes one hemisphere receive more direct solar radiation and longer days at certain times of the year, producing the familiar seasons (warmer summers when the Sun's rays are more direct and days are longer, colder winters when the Sun is lower and days are shorter). This seasonal pattern is due to tilt, not the small change in Earth-Sun distance.

Statement 3 - True. The Sun's declination varies between +23.5° and -23.5° over the year, so the midday (solar noon) altitude at a given latitude changes seasonally. (The solar noon altitude depends on latitude and the Sun's declination and thus shifts as the declination changes.)

All three statements are therefore correct.

London is closest. The Prime Meridian, defined as 0° longitude, passes through the Royal Observatory, Greenwich in London, so London lies nearest to that meridian.

By comparison, the other cities lie farther from 0° longitude: Paris at approximately 2.35°E, Madrid at about 3.70°W, and Rome near 12.50°E, so none is as close to the meridian as London.

The Prime Meridian was adopted as the global reference for longitude at the International Meridian Conference in 1884, establishing 0° longitude through Greenwich as the standard reference line.

1, 2, and 3

Statement 1 is correct. Terrestrial planets have a solid, rocky surface composed mainly of silicates and metals, whereas Jovian planets are dominated by thick atmospheres of hydrogen and helium and do not have a well-defined solid surface; they may contain a small rocky/icy core deep inside.

Statement 2 is correct. Mean densities of terrestrial planets lie in the range of about ~3.9-5.5 g/cm³ (e.g., Earth ≈ 5.52 g/cm³), while Jovian planets have much lower mean densities (Jupiter ≈ 1.33 g/cm³, Saturn ≈ 0.69 g/cm³, Uranus ≈ 1.27 g/cm³, Neptune ≈ 1.64 g/cm³), with Saturn being less dense than water (1 g/cm³).

Statement 3 is essentially correct with a qualification: Jovian planets have much larger total masses, so their overall gravitational fields are stronger; for example, Jupiter's surface gravity (~24.79 m/s²) is significantly greater than Earth's (~9.81 m/s²). However, actual surface gravity depends on both mass and radius, so not every Jovian has a higher surface gravity than every terrestrial planet (e.g., Uranus's gravity ≈ 8.69 m/s² is slightly less than Earth's).

All three statements are therefore correct, with the caveat noted for statement 3 about how surface gravity depends on radius as well as mass.

All three

Observations of other planets and moons show them to have round outlines from all viewing angles; for bodies above a certain mass, gravity pulls matter into a nearly spherical shape. By this well-established physical principle, the shapes of major celestial bodies provide strong indirect evidence that our planet is also spherical.

The systematic differences in sunrise and sunset times at different places follow from the Earth's rotation about its axis: different longitudes face the Sun at different times, producing the observed local-time sequence. This spatially coherent pattern of time differences is exactly what a rotating sphere produces.

When the Earth lies between the Sun and the Moon during a lunar eclipse, the shadow cast on the Moon is always circular. A body that casts a circular shadow in every orientation is a sphere (or very nearly so), and this geometric fact was one of the classical proofs used to infer Earth's shape.

Each of the three points above therefore provides independent, syllabus-aligned evidence supporting Earth's sphericity.

Both Statement II and Statement III are correct and only one of them explain Statement I.

Statement I is true: during a total lunar eclipse the Moon typically takes on a deep red or orange hue because the only sunlight reaching the Moon has passed through Earth's atmosphere before entering the shadow.

Statement II is true: the Moon's orbital plane is inclined by about ~5° to the Earth's orbital plane (the ecliptic), which is why eclipses do not occur at every full moon. However, this inclination explains the frequency and geometry of eclipses, not the Moon's reddish color during totality.

Statement III is true and is the correct physical explanation for the color: sunlight from the regions of Earth experiencing sunrise and sunset is bent by atmospheric refraction into Earth's shadow. The atmosphere preferentially scatters shorter (blue) wavelengths via Rayleigh scattering, so the transmitted light is enriched in red wavelengths; that reddened sunlight illuminates the Moon during totality, producing the observed deep red/orange appearance.

Therefore, both statements II and III are correct, and only Statement III explains the reddish color described in Statement I.

Gutenberg discontinuity. The Gutenberg discontinuity is the seismic boundary that separates the mantle from the outer core and lies at about 2,900 km depth.

Across this boundary, S-waves are not transmitted because the outer core is liquid, and P-waves show a marked change in velocity and refraction, producing seismic shadow zones that confirm a liquid outer core above a solid inner core.

For comparison, the Mohorovicic (Moho) discontinuity marks the crust-mantle boundary at roughly ~8 km beneath oceans and ~32 km beneath continents.

The Conrad discontinuity is an internal crustal boundary separating upper and lower continental crust, typically around 15-20 km depth.

The Lehmann discontinuity commonly refers to the boundary between the outer and inner core (the inner-core boundary identified by Inge Lehmann), located at about ~5,150 km depth.

All three

Statement 1 is correct. Twilight duration depends on the angle at which the Sun's apparent path crosses the horizon and on atmospheric refraction. Near the equator the Sun rises and sets almost vertically so the Sun moves quickly through the shallow angles below the horizon and twilight is short; at higher latitudes the Sun's path is more oblique, so it spends more time just below the horizon and twilight is longer (near the poles twilight can persist for very long periods around solstices).

Statement 2 is correct. Because the Earth is an oblate spheroid (flattened at the poles), the meridional arc length per degree varies with latitude. A standard approximation for the length of 1° of latitude as a function of latitude φ is 111132.954 - 559.822 cos(2φ) + 1.175 cos(4φ) - 0.0023 cos(6φ) (m). This gives about 110.574 km per degree at the equator (φ = 0°) and about 111.694 km per degree near the poles (φ = 90°), so a degree of latitude is indeed slightly longer toward the poles (≈ 1.12 km difference).

Statement 3 is correct. The east-west distance represented by 1° of longitude equals the equatorial degree length times the cosine of latitude, approximately 111.320 km · cos(φ). Thus the length is maximum at the equator (≈ 111.320 km) and decreases continuously to 0 km at the poles.

Ionosphere

The ionosphere is a region of the upper atmosphere (roughly 60 km to 1,000 km altitude) where solar ultraviolet and X-ray radiation (and to a lesser extent cosmic rays) create large numbers of ionized particles so the gas behaves as a plasma.

That ionization enables the layer to reflect and refract radio waves through a process called skywave propagation. The effect is most useful for HF (shortwave, ~3-30 MHz) radio, which can be returned to Earth beyond the horizon and so supports long-distance and international communication; medium-wave (AM) signals can also use ionospheric propagation at night when ionization patterns change.

Higher-frequency signals (VHF/UHF) are generally line-of-sight and do not benefit from ionospheric reflection; those rely mainly on the lower atmosphere and direct paths.

32 minutes. The longitudinal separation used in the calculation is 8°.

Because the Earth rotates 360° in 24 hours, this implies 15° = 1 hour, so 1° = 4 minutes.

Therefore the time difference is 8° × 4 minutes = 32 minutes, so the sunrise times differ by about 32 minutes under ideal conditions.

1-4-3-2

Units of the geological time scale in descending duration are: Eon > Era > Period > Epoch (each Epoch is further subdivided into Ages).

A Eon is the largest chronostratigraphic/geochronologic unit; an Era is a major subdivision of an Eon; a Period subdivides an Era; and an Epoch subdivides a Period.

Examples of the current intervals are: the PhanerozoicEon, the CenozoicEra, the QuaternaryPeriod, the HoloceneEpoch, and the present Age is the Meghalayan.

Therefore, the correct descending order is given by 1-4-3-2.

Both A and R are true but R is the correct explanation of A.

Statement A is true. The latitudinal extent is from about 8°4'N to 37°6'N (≈ 29°, commonly quoted as ≈ 30°) and the longitudinal extent is from about 68°7'E to 97°25'E (≈ 29°, ≈ 30°). The north-south distance is about 3214 km and the east-west distance about 2933 km (standard geographical figures).

Statement R is true. Meridians are not parallel but converge toward the poles (i.e., meridians converge), so the ground distance represented by one degree of longitude decreases with latitude. Parallels are essentially equally spaced in the north-south direction, so one degree of latitude has an approximately constant length (~111.32 km everywhere). The length of 1° of longitude at latitude φ is approximately 111.32 × cos(φ) km.

Because India lies mostly in the tropics (mean latitude ≈ 22°N), one degree of longitude there is roughly 111.32 × cos(22°) ≈ 103 km, smaller than the ~111 km per degree of latitude. Therefore a similar angular span (~30°) gives a larger north-south distance than east-west distance; this is why R correctly explains A.

Both 1 and 2

Statement 1 is correct: the International Date Line (IDL) roughly follows the 180° meridian and runs in a generally north-south direction between the North and South Poles, but it deviates east or west around national territories and island groups so as not to split countries or local time zones.

Statement 2 is correct: the IDL is not established by any binding international treaty-there is no internationally binding legal status for the line-so individual sovereign states decide which calendar date and time conventions they observe and may shift the line locally (for example, Kiribati's 1995 change to place the Line Islands on the same calendar day as the rest of the country).

As a practical consequence, crossing the IDL changes the calendar date: crossing from east to west across the line adds a day, while crossing from west to east subtracts a day.

D: Statement I is incorrect, but Statement II is correct.

Statement II is correct. At solar noon on 21 June (the summer solstice) the Sun's declination equals the latitude of the Tropic of Cancer (approximately 23°30′N), so locations lying on that latitude receive the Sun directly overhead at noon.

Statement I is incorrect. The city in question lies slightly north of the Tropic of Cancer (about 23°50′N), so it is not on the Tropic and does not have the Sun directly overhead at noon on the solstice. Only places located on the 23°30′N latitude experience the Sun at zenith at solar noon on 21 June.