Passage
It’s always a welcome thing to learn that ideas that are commonplace in science fiction have a basis in science fact. One such fictional concept, “the warp drive” – alternately known as FTL (Faster-Than-Light) travel, Hyperspace, Lightspeed, etc. – actually has one foot in the world of real science. In physics, it is what is known as the Alcubierre Warp Drive. On paper, it is a highly speculative, but possibly valid solution of the Einstein field equations, specifically how space, time and energy interact.
Since Einstein first proposed the Special Theory of Relativity in 1905, scientists have been operating under the restrictions imposed by a relativistic universe. One of these restrictions is the belief that the speed of light is unbreakable and hence, that there will never be such a thing as FTL space travel or exploration. But then, in 1994, a Mexican physicist by the name of Miguel Alcubierre came along with proposed method for stretching the fabric of space-time in way which would, in theory, allow FTL travel to take pace.
To put it simply, this method of space travel involves stretching the fabric of space-time in a wave which would (in theory) cause the space ahead of an object to contract while the space behind it would expand. An object inside this wave (i.e. a spaceship) would then be able to ride this region, known as a “warp bubble” of flat space. This is what is known as the “Alcubierre Metric”. Interpreted in the context of General Relativity, the metric allows a warp bubble to appear in a previously flat region of spacetime and move away, effectively at speeds that exceed the speed of light. The interior of the bubble is the inertial reference frame for any object inhabiting it.
The mathematical formulation of the Alcubierre metric is consistent with the conventional claims of the laws of relativity and conventional relativistic effects. Since the ship is not moving within this bubble, but is being carried along as the region itself moves, the laws of relativity would not be violated in the conventional sense.
One of the reasons for this is because this method would not rely on moving faster than light in the local sense, since a light beam within this bubble would still always move faster than the ship. It is only “faster than light” in the sense that the ship could reach its destination faster than a beam of light that was traveling outside the warp bubble.
However, there are few problems with this theory. For one, there are no known methods to create such a warp bubble in a region of space that would not already contain one. Second, assuming there was a way to create such a bubble, there is not yet any known way of leaving once inside it. As a result, the Alcubierre drive (or metric) remains in the category of theory at this time.
In 2012, NASA’s Advanced Propulsion Physics Laboratory (aka.Eagleworks) announced that they had begun conducting experiments to see if a “warp drive” was in fact possible. This included developing an interferometer to detect the spatial distortions produced by the expanding and contracting space-time of the Alcubierre metric.
The team lead – Dr. Harold Sonny White – described their work in a NASA paper titled Warp Field Mechanics 101. He also explained their work in NASA’s 2012 Roundup publication: “We’ve initiated an interferometer test bed in this lab, where we’re going to go through and try and generate a microscopic instance of a little warp bubble. And although this is just a microscopic instance of the phenomena, we’re perturbing space time, one part in 10 million, a very tiny amount… The math would allow you to go to Alpha Centauri in two weeks as measured by clocks here on Earth. So somebody’s clock onboard the spacecraft has the same rate of time as somebody in mission control here in Houston might have. There are no tidal forces, no undue issues, and the proper acceleration is zero. When you turn the field on, everybody doesn’t go slamming against the bulkhead, (which) would be a very short and sad trip.”In 2013,Dr. White and members of Eagleworks published their results, which were deemed to be inconclusive.
When it comes to the future of space exploration, some questions like “how long will it take us to get the nearest star?” seem rather troubling when we don’t make allowances for some kind of hypervelocity or faster-than-light transit method. How can we expect to become an interstellar species when all available methods will either take centuries (or longer), or will involve sending a nanocraft instead?
At present, such a thing just doesn’t seem to be entirely within the realm of possibility. And attempts to prove otherwise remain inconclusive. But as history has taught us, what is considered to be impossible changes over time. Until then, we’ll just have to be patient and wait on future research.
Question for 100 RCs for Practice Questions- 57
Try yourself:Which of the following best describes the 2012 experiment of Eagleworks?
Explanation
Option 1 is correct. In paragraph 8, the passage quotes NASA’s 2012 Roundup publication as “We’ve initiated an interferometer test bed in this lab, where we’re going to go through and try and generate a microscopic instance of a little warp bubble.” Thus, we can infer that the team attempted to create a warp bubble and to detect that bubble using an interferometer (which can be said to be an investigative tool). Also, paragraph 3 states that “This method of space travel involves stretching the fabric of spacetime in a wave which would (in theory) cause the space ahead of an object to contract while the space behind it would expand. An object inside this wave (i.e. a spaceship) would then be able to ride this region, known as a “warp bubble” of flat space.” Thus, we can infer that a warp bubble can be obtained by creating a wave that would distort spacetime. Retain option 1.
Option 2 is incorrect. As seen in paragraph 8, “no tidal forces, no undue issues, and the proper acceleration is zero” are the just conditions necessary for the experiment to be successful, they do not sum up the research done by the NASA team. Eliminate option 2.
Option 3 is incorrect. Paragraph 8 states that the NASA team attempted to create a microscopic instance of a warp bubble, not of a spacecraft. Eliminate option 3.
Option 4 is incorrect. Similar to option 3, paragraph 8 states that the NASA team attempted to created a microscopic warp bubble not a spacecraft. Eliminate option 4.
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Question for 100 RCs for Practice Questions- 57
Try yourself:It can be inferred from the passage that the interferometer developed by NASA Eagleworks team would
Explanation
Option 1 is incorrect. Paragraph 7 clearly states that the NASA team developed an interferometer to detect spatial distortions. There is no mention of any relation between interferometer and measuring speed of light. Eliminate option 1.
Option 2 is correct. Paragraph 7 states, “This included developing an interferometer to detect the spatial distortions …” Also, paragraph 8 states that “We’ve initiated an interferometer test bed in this lab, where we’re going to go through and try and generate a microscopic instance of a little warp bubble.” Thus, we can conclude that the interferometer would be able detect minute disturbances in space time. Retain option 2.
Option 3 is incorrect. From paragraphs 7 & 8 we can infer that the interferometer would detect the microscopic instance of a little warp bubble generated on an interferometer test bed. Thus, the interferometer itself does not generate a microscopic warp bubble. Eliminate option 3.
Option 4 is incorrect. “[To] maintain somebody’s clock onboard the spacecraft at the same rate of time as somebody in mission control in Houston might have” is a procedure to be followed during the experiment. It is not an activity done by the interferometer. Eliminate option 4.
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Question for 100 RCs for Practice Questions- 57
Try yourself:Which of the following statements holds true for Alcubierre Warp drive?
Explanation
Option 1 is incorrect. Paragraph 1 states that “the fictional concept [of] warp drive […] actually has one foot in the world of real science. In physics, it is what is known as the Alcubierre Warp Drive.” We cannot infer whether the concept in physics is inspired from ideas in science fiction. Thus we can eliminate option 1.
Option 2 is incorrect. Paragraph 2 states that “Since Einstein first proposed the Special Theory of Relativity in 1905, scientists have been operating under the restrictions imposed by a relativistic universe.” Also, paragraph 4 states that, “[In Alcubierre metric] Since the ship is not moving within this bubble, but is being carried along as the region itself moves, the laws of relativity would not be violated in the conventional sense.” Thus, we can infer that Alcubierre metric would work under the restrictions imposed by a relativistic universe. Eliminate option 2.
Option 3 is incorrect. Paragraph 3 states that “… the metric allows a warp bubble to […] move away, effectively at speeds that exceed the speed of light.” Thus, we can conclude that the warp bubble and not an object would move at speeds greater than the speed of light. Also, if an object moves at speeds greater than speed of light, then it would violate Einstein’s laws of relativity. Eliminate option 3.
Option 4 is correct. Paragraph 3 states that “… this method of space travel involves stretching the fabric of space-time in a wave which would (in theory) cause the space ahead of an object to contract while the space behind it would expand.” Thus, we can conclude that creating an Alcubierre warp drive requires expanding and contracting space around an object.
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Question for 100 RCs for Practice Questions- 57
Try yourself:The author comes to the conclusion that:
Explanation
Option 1 is incorrect. In the last paragraph, the author is optimistic that even though Alcubierre drive or FTL travel does not seem possible at present, history has shown that what we consider impossible changes over time. Option 1 does not convey the optimistic tone of the conclusion made by the author. Thus, we can eliminate option 1.
Option 2 is correct. The last paragraph states that“At present, such a thing just doesn’t seem to be entirely within the realm of possibility. [...] But as history has taught us, what is considered to be impossible changes over time. Until then, we’ll just have to be patient and wait on future research.” Option 2 conveys the optimism expressed by the author. Retain option 2.
Option 3 is incorrect. The passage is about the “Alcubierre warp drive” and the possibility of humans becoming interstellar species. Compared to option 2, option 3 does not convey the conclusion of the author in its entirety and is also a distortion of the passage. Eliminate option 3.
Option 4 is incorrect. It is irrelevant to the conclusion made by the author. In second last paragraph, the author contemplates over questions like “how long will it take us to get the nearest star?” and “How can we expect to become an interstellar species when all available methods will either take centuries (or longer) … ?” But, it is not the conclusion of the passage. Eliminate option 4.
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Question for 100 RCs for Practice Questions- 57
Try yourself:Alcubierre metric remains in the category of theory because
Explanation
Option 1 is correct. Paragraph 4 states that“The mathematical formulation of the Alcubierre metric is consistent with the conventional claims of the laws of relativity and conventional relativistic effects.” Also, paragraph 6 lists some problems with the Alcubierre metric and states that “As a result, the Alcubierre drive (or metric) remains in the category of theory at this time.” Further, paragraph 8 states that experiment to prove the Alcubierre metric “was deemed inconclusive”. Thus, we can conclude that Alcubierre metric remains in the category of theory since it is proven only mathematically. Retain option 1.
Option 2 is incorrect. Paragraph 6 mentions that “…there is not yet any known way of leaving once inside it.” But, the passage does not speculate on the survivability inside the warp bubble. Eliminate option 2.
Option 3 is incorrect. The passage does not speculate on the amount of energy required to warp spacetime. Eliminate option 3.
Option 4 is incorrect. The passage does not speculate on the time experienced by an object inside the warp bubble. Eliminate option 4.
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