首页 >  > 


時間:2022-08-15 來源:本站 點擊:258次



A Major Time Travel Perk May Be Technically Impossible

A bit of sad news for prospective time travelers — your efforts to change the past are futile, according to mathematical modeling by a pair of researchers at the University of Queensland. The past is immutable, it seems. But that implies some good news, too, for even as these findings crush our hopes of changing history, they may also remove a barrier to journeying back in time.


The rationale goes like this: If our actions in the past won’t alter anything, they also won’t produce the paradoxes that have prompted some experts to rule out time travel altogether. For example, we can’t endanger our own existence, à la Marty McFly in Back to the Future, by preventing our parents from falling in love and conceiving us. In fact, we may not be able to alter anything at all. Therefore, no logical conundrum stands between us and our temporal excursions (though they may not even be technically feasible).


That line of thinking has existed for decades and is embodied in Russian astrophysicist Igor Novikov’s self-consistency principle, which states there is zero chance of an event occurring if it would change the past in any way — the universe simply forbids revision. But now it’s supported by the calculations of Fabio Costa, a theoretical physicist, and Germain Tobar, a Cambridge student pursuing a masters in mathematics, which were published last year in the journal Classical and Quantum Gravity. The results, Costa says, “are the stuff of science fiction.”

这种想法已经存在了几十年,俄罗斯天体物理学家伊戈尔·诺维科夫(Igor Novikov)早就提出过“自身一致性原则”,该原则认为,如果某一事件以任何方式改变过去,那么它发生的可能性为零:宇宙历史不允许修改。现在,理论物理学家法比奥·科斯塔(Fabio Costa)和正在剑桥大学攻读数学硕士学位的热尔曼·托巴尔(Germain Tobar)的计算结果支持了这一观点,这些计算结果去年发表在《经典与量子引力》(Classical and Quantum Gravity)杂志上。科斯塔说,他们的研究成果“就像科幻小说里的情节。”

The Perils of Paradox


Though no one knows whether time travel is physically possible, Einstein’s theory of general relativity proves the concept is at least theoretically sound. Specifically, his equations allow for closed timelike curves, or CTCs: loops in space-time that end where they begin. An object following one of these circular trajectories would eventually arrive back at the place (and time) it started, and could interact with its past self.


There’s no guarantee they actually exist. Many eminent physicists have argued against the possibility of CTCs, whether natural or engineered via time machines made by intelligent beings. “The laws of physics do not allow the appearance of closed timelike curves,” Stephen Hawking wrote matter-of-factly in 1992. He half-jokingly dubbed this idea the “chronology protection conjecture,” a feature of reality that “makes the universe safe for historians.”


But even as a pure thought experiment, time travel is plagued by challenges. The granddaddy of them all, aptly enough, is the grandfather paradox. The name originated with the famous scenario in which a person goes back in time to kill their own grandfather before he has children. If they succeed, they’ll never be born in the future; but in that case, who killed granddad? More abstractly, it refers to any change in the past that produces a logical inconsistency.


The simplest solution to the paradox is to contend that time travel just isn’t possible — we can’t defy logic if the laws of nature prevent us from doing so in the first place. But Costa and Tobar’s modeling suggests an alternative: Try as we might to create a paradox, events will always play out the same and reach the destined outcome.


Time Without Beginning


If that last sentence sounds bizarre, it’s because we tend to get these mind-bending causal sequences backward. As Costa explains, “everything that has ever happened has happened only once,” and in precisely one way. Our contrary intuition (that the past is changeable) stems in part from the fact that we imagine time travel as external to the mainline of history. In reality, it’s just as entangled in that history as any other event.


If you visit a previous era, then you have always visited and always did whatever you did there. There was no “first time around” in which it occurred differently. “If a time traveller is going to travel to some past time, then she has already been there,” as the Australian philosopher Nicholas J. J. Smith wrote in a 1997 paper titled “Bananas Enough for Time Travel?” She can affect the past, certainly, but not change it. Her actions will never alter the course of events — it’s just the way things went the only time around.

如果你回到了过去,你会一直旁观,一直做你已经做过的那些事情。现实不像游戏,不会给你那么多“从第一轮”开始的机会。澳大利亚哲学家尼古拉斯·J。 史密斯(Nicholas J。 Smith)在1997年的一篇论文《为时间旅行准备的香蕉皮够多吗?》中写道,“如果一个时间旅行者要回到过去的某个时间,那么历史上他已经在那里出现过了。”他可以影响过去,但不能改变最后的结局。他的行为永远不会改变事情的发展轨迹——这是事情唯一的发展方式。

It may help to realize that although we’re accustomed to thinking of time as linear, this is an inherent human bias. It suits our standard notions of chronology, but “when there is time traveling involved, this way of reasoning doesn’t really work anymore because you cannot have a story with a beginning and an end,” Costa says. The frames in the movie reel of life are no longer side-by-side, but overlapping. “We tell the story all at once,” he says.


For physicists like Costa, there is a practical upshot here: You can’t study events in a time loop the same way you would in our familiar world by extrapolating an outcome based on initial conditions. There are no “initial” conditions, and the word loses meaning. So Costa and Tobar shifted the perspective. Their model doesn’t proceed from some imaginary beginning but rather from a set of fixed variables that you can imagine as human choices. From there, Costa says, “the physics writes the rest of the story.”


And what is the story? It’s one in which people are still “free,” in some sense, to act as they will. In the sacrosanct procession of time, Costa says, “the universe is just doing the only thing it can do, which is to be consistent with itself.”


And if visiting the past is possible, it could come with other caveats. First off, hypothetical designs for time machines typically require either infinite mass or negative energy, a power source we’re nowhere near harnessing. Second, due to the nature of closed timelike curves, a time machine can venture back no farther than the moment of its creation. So if we do manage to build or discover one, our voyages will still be limited. You’ll likely have to abandon those dreams of riding a brontosaurus.


The subject comes with enough complications to deter many scholars from tackling it. “Time travel isn’t the most studied subject,” Costa says, “because most likely it doesn’t exist.” But it remains a perennial subject of wonder and fascination, and not without reason: “The tantalizing aspect,” he adds, “is that we can’t prove it’s impossible.”


Mixed days for Chinese competitors in Badminton World Championships******

MADRID, Dec. 15 (Xinhua) -- There were mixed results for the Chinese players in the TotalEnergies BWF Badminton World Championships in Huelva, Spain on Wednesday.。

14th seed Wang Zhiyi progressed to the third round thanks to a 21-7, 2-17 win over Germany's Yvonne Li in women's singles, but the results were less good in the various doubles tournaments.。

The men's pairing of Hi Jiting and Tan Qiang fought their way back from a set down to overcome the English duo of Callum Hemming and Steven Stallwood. After losing the first set 21-16, the Chinese pair recovered their form and composure and move into the last 16 thanks to winning the last two sets 21-12 each.。

Ou Xuanyi and Zhang Nan couldn't follow their compatriots into the next round and went out of the competition after a mammoth battle against the number four seeds, Aaron Chia and Soh Wooi Yik from Malaysia.。

The Malaysian duo sneaked the first set 21-18, before the Chinese duo fought back to take a tense second set 22-20, before Chia and Yik showed their experience to win the final set 21-16.。

Guo Win Wa and Zhang Shuxian also went out in the mixed doubles after they were beaten by the Danish pairing of Mathias Christiansen and Alejandra Boje, 21-16, 17-21, 21-14, in a match where an improved second set gave the Chinese duo hope of winning through, only for their rivals to come back strongly to qualify.。

In women's doubles, China's 10th seeds, Li Wenmei and Zheng Yu moved into the last 16 with a 21-9, 21-14 triumph over the Thai pairing of Benyapa Aimsaard and Nuntakarn Aimsaard.。

However, the other Chinese pairing of Lui Xuanxuan and Xia Yuting had less fortune as the number 14 seeds were knocked out of the tournament 21-11, 9-21, 21-13 in an entertaining match against India's Ashwini Ponnappa and Reddy N Sikki. Enditem。

【红运彩票app_红运彩票app下载-标准版👉👉十年信誉大平台,点击进入👉👉 打造国内最专业最具信赖的彩票平台,为您提供红运彩票app_红运彩票app下载-标准版用户登录全网最精准计划软件,APP下载登陆,强大的竞彩网上推荐!!】

驻陕某战略支援军队面向社会招考文职人员 西安招考职位140个******



  战略支援军队某旅遍布在中国好几个省份,配有国家级重点实验室和博士研究生研究工作平台。依次塑造出多位中科院院士、专业技术人员大将,30多人次当选国家“万人计划”、新时代百千万人才工程项目和军队自主创新人才工程项目、被评选为全国各地出色科技工作者、获中国科协“实事求是”奖等,60人享有国家国务院津贴;喜获国家科学交流会奖2项,国家国家科技进步奖17项,部队国家科技进步奖近600项,30好几个团体和本人喜获一等功以上奖赏。吕炳宏 小编 赵明。



西安第三轮核酸筛查检出阳性400人 第四轮检出阳性病例数逐渐降低******














3.新款宝马M135i路试谍照曝光 2023年正式亮相


© 1996 - 红运彩票app_红运彩票app下载-标准版 版权所有 xxxxx




乐喜彩票_首页-网盟彩票-网盟购彩快三-VIP彩票平台-安全购彩-彩票双胆独-官网-巴特彩票 - 官方网站-公海bb彩票下载-爱心彩票-购彩大厅-凤凰彩票代理-Lee【天天】-第1彩票 app下载-新版APP下载-一分快3-首页-中财彩票_中财彩票app下载_中财彩票app官网-快三登录-快3登录平台-首页-彩票返水-官网-乐福彩票-购彩大厅-凤凰彩票app下载-新版APP下载-天逸彩票_购彩大厅
山东临沂退役军人服务中心:一张张“光荣单”,一份份爱兵情| “康老虎”康虎振将军逝世,曾在自卫反击战中重创敌王牌师| 孙春兰在海南调研:刻不容缓落实措施 以快制快尽早扑灭疫情| 中国最没存在感的省会,但逢“赌”必赢| 这张照片侧面证实了解放军“封岛”演习区选择的深意| 男子将保险柜伪装成垃圾放垃圾桶旁边 24万现金被捡走| 一张照片 侧面证实了解放军"封岛"演习区选择的深意| 苏醒老婆廖语辰疑怀二胎 被发现晒照中有月子餐| 专家解读:日本核废水排海背后危机| 策动代理人战争还不够 美国对叙利亚“敲骨吸髓”| 公安部10个“百日行动”专项督察组赴全国,组长均亮相| 北京:此次疫情重症和危重症患者比例明显偏低| 外交部:敦促美方停止抹黑中国军民融合发展政策| 压实四方责任,兼顾暑期防疫与旅游| 三个月三次调整职务,他最终落马!曾与今年最特殊的“老虎”共事| 不良信息举报 Complaint Center| 香港地标珍宝海鲜舫今日驶离香港,将“移居”东南亚| 深圳"0首付"买房被叫停!深房中协发布风险提示|