BEST IELTS Academic Reading Test 581

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IELTS ACADEMIC READING TEST 581 – PASSAGE -3

IELTS ACADEMIC READING TEST 581

READING PASSAGE – 3

Listening to the Universe: The Science of Gravitational Waves

A. In 2015, a ripple travelled across the cosmos and gently passed through Earth, setting off detectors in Louisiana and Washington, USA. This ripple was not in water, air, or sound—it was in the very fabric of space and time. Known as gravitational waves, these distortions were first predicted by Albert Einstein in 1916 as part of his general theory of relativity. For a century, they remained theoretical, until the Laser Interferometer Gravitational-Wave Observatory (LIGO) recorded the first confirmed signal, caused by the collision of two black holes more than a billion light years away.

B. Gravitational waves are produced when massive celestial objects like black holes or neutron stars accelerate, such as during collisions or mergers. These events are so energetic they cause space-time itself to stretch and squeeze. However, by the time these ripples reach Earth, they are incredibly faint—thousands of times smaller than a proton. Detecting them requires extraordinarily sensitive instruments. LIGO and its European counterpart, Virgo, use laser interferometry to measure changes in distance smaller than one ten-thousandth the diameter of a hydrogen atom.

C. The detection process involves splitting a laser beam along two perpendicular arms, each several kilometers long. When gravitational waves pass through, they distort the lengths of the arms slightly, causing shifts in the interference pattern when the beams are recombined. These changes are then analysed to determine the origin, distance, and cause of the wave. While the technology is mind-boggling, what excites scientists is the potential: gravitational wave astronomy provides a completely new way of observing the universe—one that is not based on light.

IELTS ACADEMIC READING TEST

D. Traditional telescopes rely on electromagnetic radiation—light, X-rays, radio waves—to observe celestial bodies. However, light can be absorbed, scattered, or blocked by dust and gas. Gravitational waves are not affected in the same way. They pass through matter virtually undisturbed, offering a direct view into some of the most extreme and mysterious parts of the cosmos. For instance, the interiors of black holes, the exact moment of a neutron star merger, and the first seconds after the Big Bang may all be accessible through this new form of detection.

E. The scientific implications are enormous. For one, these detections confirm key aspects of Einstein’s theory. More importantly, they open up possibilities for discovering events never previously observed. Already, gravitational wave observations have led to the discovery of intermediate-mass black holes, a category that had only been theorised. In 2017, the merger of two neutron stars was detected both through gravitational waves and traditional telescopes, marking the first multi-messenger astronomy event—where gravitational and electromagnetic data are combined to study the same phenomenon.

F. Despite its promise, gravitational wave astronomy is still in its infancy. LIGO and Virgo can only detect a small portion of events in the universe, and they rely on highly synchronised global networks. Future observatories, like the proposed Einstein Telescope in Europe and LISA (Laser Interferometer Space Antenna) planned by the European Space Agency, aim to detect lower-frequency waves and cover a broader range of cosmic events. These advancements may eventually allow scientists to detect signals from the early universe—long before galaxies ever formed.

G. The field of gravitational wave astronomy not only enhances our understanding of the universe but also symbolises a new era in scientific exploration. Much like Galileo’s first telescope opened up the night sky to detailed scrutiny, gravitational wave detectors promise a deeper, more dynamic map of reality. By ‘listening’ to the universe, we are beginning to uncover cosmic secrets previously hidden in silence.

IELTS ACADEMIC READING TEST

Questions 27–33

The reading passage has seven paragraphs, A–G.

Which paragraph contains the following information?

Write the correct letter, A–G.

27. The comparison between gravitational waves and traditional light-based observation

28. Description of how gravitational wave detectors work

29. The extreme sensitivity required to identify gravitational waves

30. The confirmation of a theory made over a hundred years ago

31. How gravitational waves can bypass cosmic obstacles

32. The limitations of current detection technology

33. A groundbreaking observation involving two types of signals

Questions 34–35

Choose the correct letter, A, B, C, or D.

34. What causes gravitational waves?

A. The rapid expansion of space

B. Movement of any object in space

C. Collisions between massive celestial objects

D. Light reflecting off cosmic dust

35. What makes gravitational waves difficult to detect on Earth?

A. They only occur very rarely

B. They are distorted by Earth’s atmosphere

C. Their effects are extremely small

D. Most of them travel away from Earth

IELTS ACADEMIC READING TEST

Questions 36–40

Choose ONE WORD ONLY from the passage for each answer.

Gravitational waves are generated when massive objects such as black holes or 36.__________ move rapidly or collide. Although these events release immense energy, the effects of gravitational waves are extremely faint when they reach Earth. Instruments like LIGO detect them using 37__________ beams split into perpendicular arms, and the interference patterns reveal slight distortions in space.

Unlike traditional astronomy, which depends on forms of 38__________ radiation like visible light, gravitational waves are not affected by gas or dust. This allows scientists to observe violent cosmic phenomena directly. One major achievement was the detection of a neutron star merger in 2017, which marked the first use of 39__________ to study the same event through different data sources. Future missions like LISA will aim to detect gravitational signals from the 40__________ universe, opening new windows into the early cosmos.

IELTS ACADEMIC READING TEST

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