Science IELTS Listening Reading Practice
Science IELTS Listening Reading Practice
Selected Text (below 500 words)
Source: https://www.space.com
Time travel — moving between different points in time — has been a popular topic for science fiction for decades. Franchises ranging from “Doctor Who” to “Star Trek” to “Back to the Future” have seen humans get in a vehicle of some sort and arrive in the past or future, ready to take on new adventures. The reality, however, is more muddled. Not all scientists believe that time travel is possible. Some even say that an attempt would be fatal to any human who chooses to undertake it.
Understanding time
What is time? While most people think of time as a constant, physicist, Albert Einstein, showed that time is an illusion; it is relative — it can vary for different observers depending on your speed through space. To Einstein, time is the “fourth dimension.” Space is described as a three-dimensional arena, which provides a traveler with coordinates — such as length, width and height —showing location. Time provides another coordinate — direction — although conventionally, it only moves forward. (Conversely, a new theory asserts that time is “real.”)
Einstein’s theory of special relativity says that time slows down or speeds up depending on how fast you move relative to something else. Approaching the speed of light, a person inside a spaceship would age much slower than his twin at home. Also, under Einstein’s theory of general relativity, gravity can bend time.
Picture a four-dimensional fabric called space-time. When anything that has mass sits on that piece of fabric, it causes a dimple or a bending of space-time. The bending of space-time causes objects to move on a curved path and that curvature of space is what we know as gravity.
Both the general and special relativity theories have been proven with GPS satellite technology that has very accurate timepieces on board. The effects of gravity, as well as the satellites’ increased speed above the Earth relative to observers on the ground, make the unadjusted clocks gain 38 microseconds a day. (Engineers make calibrations to account for the difference.) In a sense, this effect, called time dilation, means astronauts are time travelers, as they return to Earth very, very slightly younger than their identical twins that remain on the planet.
Through the wormhole
General relativity also provides scenarios that could allow travelers to go back in time, according to NASA. The equations, however, might be difficult to physically achieve. One possibility could be to go faster than light, which travels at 186,282 miles per second (299,792 kilometers per second) in a vacuum. Einstein’s equations, though, show that an object at the speed of light would have both infinite mass and a length of 0. This appears to be physically impossible, although some scientists have extended his equations and said it might be done.
A linked possibility, NASA stated, would be to create “wormholes” between points in space-time. While Einstein’s equations provide for them, they would collapse very quickly and would only be suitable for very small particles. Also, scientists haven’t actually observed these wormholes yet. Also, the technology needed to create a wormhole is far beyond anything we have today.
2. What does the following expression imply? [Time 0:28]
1. What are the two methods through which we can travel to the future?
Traveling to the future, as commonly depicted in science fiction, remains theoretical with our current understanding of physics. According to Einstein’s theory of relativity, time dilation suggests that if one were to travel at speeds close to the speed of light, time would pass slower for them relative to those on Earth, effectively “traveling” into the future. However, practical implementation of such travel is beyond our current technological capabilities and remains a subject of scientific speculation and research.