Venus In Transit — IELTS Reading Answers

examples of different ways in which the parallax principle has been applied

“Johann Franz Encke, Director of the Berlin Observatory, finally determined a value for the AU based on all these parallax measurements: 153,340,000 km. Reasonably accurate for the time, that is quite close to today's value of 149,597,870 km, determined by radar,”

Paragraph F applies parallax to fix the AU, notes radar superseding transits, and extends the principle to stars — several applications.

a description of an event which prevented a transit observation

“He was thwarted by the fact that the British were besieging his observation site at Pondicherry in India. Fleeing on a French warship crossing the Indian Ocean, Le Gentil saw a wonderful transit – but the ship’s pitching and rolling ruled out any attempt at making accurate observations.”

Paragraph D describes Le Gentil thwarted by a siege, then by the ship's 'pitching and rolling', then by cloud — events preventing observation.

a statement about potential future discoveries leading on from transit observations

“But such transits have paved the way for what might prove to be one of the most vital breakthroughs in the cosmos – detecting Earth-sized planets orbiting other stars”

Paragraph G says transits may lead to 'detecting Earth-sized planets orbiting other stars', a potential future discovery.

a description of physical states connected with Venus which early astronomical instruments failed to overcome

“When Venus begins to cross the Sun's disc, it looks smeared not circular – which makes it difficult to establish timings. This is due to diffraction of light. The second problem is that Venus exhibits a halo of light when it is seen just outside the Sun's disc.”

Paragraph E describes Venus appearing 'smeared not circular' and ringed by a halo, effects that defeated accurate timing with early instruments.

He calculated the distance of the Sun from the Earth based on observations of Venus with a fair degree of accuracy.

“Johann Franz Encke, Director of the Berlin Observatory, finally determined a value for the AU based on all these parallax measurements: 153,340,000 km. Reasonably accurate for the time, that is quite close to today's value of 149,597,870 km, determined by radar,”

Encke 'finally determined a value for the AU' at 153,340,000 km, 'reasonably accurate for the time', so D.

He understood that the distance of the Sun from the Earth could be worked out by comparing observations of a transit.

“He realised that, from different latitudes, the passage of the planet across the Sun's disc would appear to differ. By timing the transit from two widely-separated locations,”

Halley realised timing a transit 'from two widely-separated locations' yields the parallax angle and so 'the distance of the Earth from the Sun' — option A.

He realised that the time taken by a planet to go round the Sun depends on its distance from the Sun.

“Johannes Kepler, in the early 17th century, had shown that the distances of the planets from the Sun governed their orbital speeds, which were easily measurable”

Kepler showed 'the distances of the planets from the Sun governed their orbital speeds', which is orbital time depending on distance — B.

He witnessed a Venus transit but was unable to make any calculations.

“Le Gentil saw a wonderful transit – but the ship's pitching and rolling ruled out any attempt at making accurate observations”

Le Gentil 'saw a wonderful transit' yet the ship's motion 'ruled out any attempt at making accurate observations', so C.

Halley observed one transit of the planet Venus.

“In November 1677, Halley observed a transit of the innermost planet, Mercury, from the desolate island of St Helena in the South Pacific Nevertheless, he accurately predicted that Venus would cross the face of the Sun in both 1761 and 1769 – though he didn't survive to see either”

Halley observed Mercury, not Venus, and 'didn't survive to see either' Venus transit he predicted. FALSE.

Le Gentil managed to observe a second Venus transit.

“Ironically after travelling nearly 50,000 kilometres, his view was clouded out at the last moment, a very dispiriting experience”

At the second transit 'his view was clouded out at the last moment', so he failed to observe it. FALSE.

The shape of Venus appears distorted when it starts to pass in front of the Sun.

“When Venus begins to cross the Sun's disc, it looks smeared not circular”

'It looks smeared not circular' means the shape appears distorted as it begins crossing the Sun's disc. TRUE.

Early astronomers suspected that the atmosphere on Venus was toxic.

“While this showed astronomers that Venus was surrounded by a thick layer of gases refracting sunlight around it, both effects made it impossible to obtain accurate timings”

Astronomers deduced only 'a thick layer of gases refracting sunlight'; nothing in the passage says they suspected the atmosphere was toxic.

The parallax principle allows astronomers to work out how far away distant stars are from the Earth.

“The parallax principle can be extended to measure the distances to the stars. If we look at a star in January – when Earth is at one point in its orbit – it will seem to be in a different position from where it appears six months later.”

'The parallax principle can be extended to measure the distances to the stars', and the shift lets astronomers 'calculate the distance'. TRUE.