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The Allure of Pet Ideas |
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And indeed it takes from our achievements, though performed at height, the pith and marrow of our attribute. |
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Shakespeare |
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A popular science blogger recently posted a video purporting to debunk the “ten biggest myths in physics”, and the biggest myth of all (we’re told) is “Faster than light travel is incompatible with Einstein’s theories”. Her debunking of this “myth” consists of the following: |
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You can totally have faster than light travel in Einstein’s theories. What is true is that Einstein’s theory also tells you that it takes an infinite amount of energy to accelerate from below the speed of light to above the speed of light… in any other instance in which physicists encounter something becoming infinitely large, they say that’s not physically real, it just means that the theory breaks down. I think it’s the same for faster than light travel. It’s not impossible, just difficult. |
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There are several obvious problems with this reasoning. First, special relativity (i.e., local Lorentz invariance) does not say anything about the energy required to accelerate something from below to above the speed of light, it says the amount of energy increases without limit as the speed approaches the speed of light. Since we cannot supply infinite energy, nothing can be accelerated to, let alone above, the speed of light (in terms of any standard system of inertial coordinates). |
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The blogger has mis-represented what special relativity says, by claiming that it talks about “accelerating objects from below to above the speed of light”, and then on this basis claiming that special relativity entails an actual infinite energy to achieve this. Then she asserts that this is an unrealistic proposition, since an actually infinite amount of energy can’t be realized. But this is not a criticism of special relativity, which does not entail an infinite energy for any entity, it is a criticism of her misrepresentation. |
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Moreover, the blogger’s reasoning is self-defeating, because her thesis is that faster-than-light (FTL) travel is compatible with special relativity, and yet by her own argument, she concludes that special relativity must “break down” in order for FTL travel to be possible. This is not an argument for being compatible with special relativity, it is an argument for being blatantly incompatible. |
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We’ve discussed elsewhere many of the irrefutable reasons why, as Einstein put it, FTL travel, or even just signaling, “has no possibility of existence” given local Lorentz invariance, i.e., special relativity. See also this article for a related discussion. Temporal propagation along a spacelike interval (with imaginary proper time) doesn’t even make sense. It is a contradiction in terms. Of course, one can deny local Lorentz invariance (despite the failure of all tests to find the slightest violation of it), but the question at issue is not whether special relativity is correct, but whether FTL travel is compatible with special relativity… and the answer to that question is unambiguously no. |
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How is it possible, then, for this blogger, who has presumably studied physics at the university level, to hold such a silly belief? It seems to be a fixed “pet idea” of hers, and this isn’t just some side issue, we find her returning to this topic repeatedly, now even asserting that Einstein’s stated belief about the incompatibility of FTL travel with special relativity is not just wrong, but that it is the single biggest myth in physics! |
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And why does she always carefully refer to “Einstein’s theories” rather than to special relativity or local Lorentz invariance? Ordinarily one would just overlook the weird verbiage, and assume that she’s just using “Einstein’s theories” as a quaint colloquial expression… and yet… she so scrupulously avoids ever actually referring to the relevant theories by name, always choosing instead to talk about “Einstein’s theories”, it makes me wonder if this is a clue as to what’s going on in her mind. In previous postings she referred to special relativity by name, so is this just a new style of writing, or does the change from “special relativity” to “Einstein’s theories” have some deeper significance? |
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It’s actually not uncommon to encounter anti-relativity kooks who tout Einstein, the personage, but who believe that everyone except themselves misunderstands “Einstein’s theories”, including Einstein. This blogger herself used to claim that Einstein never once said FTL travel was impossible in the context of special relativity, but then people pointed out to her that he did indeed say precisely that, numerous times, and furthermore that he explained the irrefutable reasons for it (again, given local Lorentz invariance). Since then, she seems to less frequently deny that Einstein ever said that, but she still has no appetite to engage with the reasons that Einstein (and others) described. Instead, she just refers to “Einstein’s theories”, usually plural, even though her discussions invariably focus on the domain of special relativity. For example, she isn’t talking about closed time-like loops in general relativity, etc., nor is she talking about the photo-electric effect, Bose-Einstein statistics, Brownian motion, or any of Einstein’s other “theories”. |
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So, her assertion that FTL travel is compatible with “Einstein’s theories” raises the question of what she actually regards as “Einstein’s theories”, and how those are related (if at all) to what scientists understand as special relativity and local Lorentz invariance. Does she have in mind some different theories? |
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It’s also not uncommon to encounter anti-relativity kooks who are self-avowedly motived by their devotion to the science fiction image of space travel. Indeed, our blogger has admitted that this is a large factor in her belief in FTL travel. Perhaps at some early age these individuals fall in love with the idea of inter-stellar space travel, allowing journeys of adventure that could be completed in a small amount of elapsed Earth time, and became determined to “debunk” the belief that such travel is incompatible with “Einstein’s theories”. This becomes a pet idea that stays with them, and they never subject it to ordinary adult critical scrutiny. It may even have been a significant part of their motivation to study physics in the first place. It’s a point of faith, not subject to rational refutation. It’s interesting how even seemingly rational people often have some particular pet idea, and they become kooks on the subject. Each of us may do well to examine our own ideas, to see if we’re carrying any pet ideas that don’t stand up to scrutiny. |
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Somehow this reminds me of the old story about a conversation between two guys attending a lecture by Arthur Eddington in his later years. “Does everyone become a crackpot eventually?” one of the guys asked. “No”, said the other, “A genius may sometimes go nuts, but guys like us just get dumber and dumber.” |
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