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“秒”要被重新定义了 潘建伟团队这项“国际首次”研究功不可没_我的网站

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Staff members secure aircraft at Hangzhou Xiaoshan International Airport to prepare for Typhoon Dolphin on August 9, 2026. Photo: VCG
    Staff members secure aircraft at Hangzhou Xiaoshan International Airport to prepare for Typhoon Dolphin on August 9, 2026. Photo: VCG
Typhoon Dolphin made landfall in Taizhou, East China's Zhejiang Province, on Sunday afternoon, bringing strong winds up to 42 meters per second and heavy torrential rain to the coastal regions amid a red alert - the highest level in the country's typhoon warning system - issued for it earlier that day. 
Authorities in East China's Fujian have relocated nearly 100,000 residents, while coastal provinces are suspending railway services and canceled flights, making an all-out effort to mitigate possible risks.
The NMC maintained orange rainstorm and blue severe convective weather alerts at 6 am on Sunday, forecasting exceptionally heavy rainfall of 250 to 440 millimeters in some areas along the eastern coast of Zhejiang, with heavy to torrential rains expected across Jiangsu, Zhejiang, Shanghai, and Anhui between Sunday morning and Monday morning, China Central Television (CCTV) reported. 
In response to the typhoon, China's meteorological authority on Sunday upgraded its emergency response for severe meteorological disasters from Level III to Level II.
Fujian raised the emergency response level for typhoon prevention to Level II at 9 am on Sunday.
As Typhoon Dolphin gathers strength and approaches the coastal areas, Fujian's flood control authority, as of 6 pm on Saturday, deployed a total of 17,800 officials to and relocated 98,900 people from high-risk areas, Xinhua News Agency reported on Saturday.
Fujian has suspended all 115 marine engineering projects and moved 290 construction vessels to safe waters, while 55 passenger ferry routes in affected waters have been halted, chinanews.com reported. 
Meanwhile, railway services in the affected regions including Fujian, Zhejiang, Shanghai have also been suspended from Sunday to Monday, according to chinanews.com.
Fujian authorities have urged stronger safety measures for returning vessels, offshore platforms and coastal and island tourism, as well as reinforcement of aquaculture facilities. They also called for timely evacuations from flood- and landslide-prone areas to guard against secondary disasters from the typhoon and heavy rain, chinanews.com reported. 
In Zhejiang, Wenzhou city has closed all 85 A-level national tourist attractions, turned away more than 7,400 visitors and evacuated over 1,600, with the relocation effort ongoing, according to CCTV. Next, Wenzhou will next implement a "five suspensions" policy, halting outdoor group activities, classes, work, business operations and transportation.
All fishing vessels at Shitang Fishing Port in Wenling, Zhejiang, have returned to port, with all personnel evacuated ashore and maritime rescue teams on standby. Authorities urged vessels to stay off the sea during the typhoon. 
In Shanghai, Pudong and Hongqiao airports operated at reduced capacity on Sunday, with nearly 60 percent of flights canceled. A total of 1,384 flights are scheduled to be canceled including 871 at Pudong and 513 at Hongqiao. Passengers are advised to check with their airlines for the latest updates and adjust travel plans accordingly, according to CCTV.
According to Hu Xiao, meteorological analyst at the NMC, the typhoon has several notable features, including its strong intensity and expansive circulation. The typhoon also has several unusual features. Forming unusually far east, near 180°E, it has traveled more than 7,200 kilometers, making its potential landfall in China a rare event and possibly the easternmost such landfall since 1951. Its 12-day lifespan is also well above the typical seven-to-10-day average, CCTV reported. 
According to Ma Jun, director of the Institute of Public and Environmental Affairs, Typhoon Dolphin traveled a long distance and remained at typhoon or severe typhoon strength of its lifespan so far. Despite passing through some areas that were unfavorable to its development, its powerful inner core remained intact, while its extensive cloud system continued to absorb moisture and energy, fueling the potential for torrential rainfall.
The typhoon has remained at sea for more than 260 hours and experienced a rare "three rises and three falls" in intensity. Its unusually long lifespan has allowed it to absorb more moisture and energy, while repeated intensity fluctuations have complicated forecasts of its future track and intensity of wind and rainfall, according to CCTV. 
After landfall, Typhoon Dolphin may move slowly, prolonging heavy rainfall and raising the risk of extreme precipitation and related disasters. Its track later in the week remains uncertain as it could interact with the southwest monsoon and cold air from the northwest, potentially broadening and intensifying its impacts, Ma told the Global Times on Sunday.

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根据实验结果来看,研究有效验证了星地链路高精度光频标比对的可行性,向建立广域光频标网络迈出重要一步。对此,中国科学技术大学张强教授表示:将来如果放在卫星上能做洲际的时间比对,我们就可以实现新一代的“秒”定义。为什么“秒”要被重新定义了?咱们现在经常提到的时间概念“秒”,是自 1976 年以来,一直由铯-33 原子钟来定义的。原子钟最初是英国物理学家 Louis Esseb 创造,它的工作原理是计算原子中的电子自旋的翻转频率。而在 1976 年这一年,科学家们通过铯-133 原子在微波频率下的跳动,重新定义了这个时间基本单位:1 秒 = 铯原子的电子自旋翻转 9192631770 次的持续时间。虽然说这种方式已经够精确了,但科学家们似乎却不满足于此。

B | 截至目前,自然领域中对时间的测量精度已经步入 10-19 的量级。这种量级通俗点来讲,就是百亿年期间误差不会超过 1 秒。而且时间是目前七大基本物理量中测量最精确的那一个。但单有最精确的计时还是不够的,因为它还需要“配套”一个与之精度相匹配的时间传递技术。二者的重要性可以说是画等号的。

C | 但地面附近自由空间的环境复杂,大气中的各种扰动、湍流、链路损耗、环境变化等因素,给自由空间长距离时频传递带来了极大困难。此前,自由空间中的光频传输技术只能实现 10 公里量级的传输。而潘建伟团队要攻克的正是这一难题:在光源方面,研制出高功率、高稳定度光输。在光信号收发信道方面,研制出高稳定性、高效率的光收发望远镜系统。还采用线性光学采样的干涉测量方式,实现了高精度的时间测量。最终,潘建伟团队在相隔 113 公里的新疆南山天文台和高崖子天文台之间,实现了万秒 10-19 量级稳定度的时频传递。
据张强介绍:把我们非常精密的这种时间信号,通过这个望远镜打到这个 100 公里以外的另外一个望远镜。那边的话,然后我的这个信号被那边的一个同样的一个望远镜接收,接收了之后他们进行一些比较精密的时间探测。同时那边也会打一个同样的一个精密的光源信号也打过来,在这边也做一个同样的一个精密探测,然后两边的信号再做一个对准,做一个校正。

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据了解,该实验在如此自由空间时频传递过程中:时间传递万秒稳定度达到飞秒量级,频率传递万秒稳定度优于 4E-19,系统相对偏差为 6.3E-20±3.4E-19,系统可容忍最大链路损耗高达 89dB,远高于中高轨星地链路损耗的典型预期值(约 78dB)。
而国际计量组织计划 2026 年讨论“秒”定义的变更,也正因这项研究成果的实现,张强认为:如果能够实现洲际的比对的话,那么我们就可以实现新一代的这个“秒”定义。与日常生活相关那么接下来的一个问题便是,这项研究成果会带来哪些影响?引用 Nature 审稿人的评价就是:该工作是星地自由空间远距离光学时间频率传递领域的一项重大突破,将对暗物质探测、物理学基本常数检验、相对论检验等基础物理学研究产生重要影响。但除此之外,其实这项研究也与人们的日常生活息息相关。

E | 例如卫星的导航精度与计时精度紧密相关,若是希望定位更加准确(毫米以下),就需要更好的计时精度。在大地测量、地质勘探、雷达探测等涉及社会民生的领域,精确的时间也都将发挥重要的作用。那么对于未来新“秒”的定义,你期待了吗?参考链接:[1]https://www.nature.com/articles/s41586-022-05228-5[2]https://weibo.com/2032139271/Mb1zivEhA?type=comment[3]https://mp.weixin.qq.com/s/MCbQ6UJFNflzF0VmrtPw4Q[4]https://tv.cctv.com/2022/10/06/VIDEYEjxB0UTcY85WichtWvz221006.shtml?spm=C45404.PCHhhgX3efBE.Ev0XVtu8CoWN.224[5]https://ishare.ifeng.com/c/s/v002EZ3vLgfck1LPf29qCKM51b4D1bqKqLDSTFiDq8nGUgw__。

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