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光速或纬度的数值完全跟单位进制标准有关,这些是绝对值。不同标准数值不同,巧合了完全就是无稽得很。
但是有些相对值数字是宇宙普适的。比如圆周率、勾股值、自然对数、……,这些出现巧合才能说明问题!不过这也就不算巧合了,因为既然是宇宙通理,到底是人(可以说明当时的人认识到这个数值)还是动物(动物很多“知晓”自然道理,比如蜂巢的内角)还是自然现象(比如玄武岩结晶六棱柱、雪花六角形)还是外星人造出来的,就不好说!其实人类认识的真理都是相对的(这些太自然,太科学,就不会被人当神迹),但是人类总是把主观的绝对值当神迹!
偈子曰:
相对静止可观测,绝对运动实难察!
不同维度万千变,海森伯说那由他!

癯鹤 发表于 2018-4-12 16:02

凡所有相皆是虚妄
若见诸相非相
即见如来

凡所有相皆是虚妄
若见诸相非相
即见如来
佛示如来!false~realise!神术or魔术?神经呀神经,把观察到的相对当做绝对,难怪信神的大部分都是被他人或自己蒙蔽! ...
癯鹤 发表于 2018-4-13 16:48
绝对的不同也要用相对值来衡量,这个问题比较悬,我只懂哲学原理,技术问题没学通,不敢卖乖。但是这个新闻好像就是说的这个问题:


只用时钟就能找到暗物质粒子、撬动现代物理的基石?
只用时钟就能找到暗物质粒子、撬动现代物理的基石?
2018年04月20日 10:03环球科学
缩小字体放大字体收藏微博微信分享34腾讯QQQQ空间






图片来源:quantamagazine
  除了为我们提供最准确的时间,一台精密的原子时钟还有哪些出人意料的应用?答案是,成为一台暗物质探测器。通过探测原子跃迁频率,一批科学家试图用这类最小的探测器,找出暗物质的踪迹。
  撰文 | Gabriel Popkin
  翻译 | 李昌浩
  审校 | 吴非
  上世纪90年代末,在美国科罗拉多大学博尔德分校的JILA研究所,年轻的物理学家叶军作出了一个极大影响他人生轨迹的决定:投身于开发全世界最精密的原子钟。他花了不少精力去研究不同的原子,例如镁原子、钙原子和钡原子,最终他选择了性质较为稳定的锶原子。之后,他开始搭建一个以合适频率激发锶原子的激光平台,它的工作原理就像普通钟表的振荡器一样。
  但叶军不知道的是,他设计的原子钟同时也是一台暗物质探测器。2015年4月,他收到一封澳大利亚南威尔士大学物理学家Victor Flambaum的邮件,在邮件中Flambaum告诉叶军,根据一些理论,暗物质可能会略微改变物理定律常数,从而改变时钟运行速度。但由于暗物质的影响非常微弱,一般的时钟根本探测不到这一现象。叶军开发的最新一代时钟(精度比第一版提升了两万倍)是世界上为数不多的能够探测这一极为细微现象的仪器之一。
  现在,叶军正通过世界上最不寻常的实验之一,搜寻暗物质的踪迹。科学家认为宇宙中暗物质的含量大约是普通物质的5倍,但目前只能通过观测它对天体的引力来推测其含量。通过精密测量原子钟的频率是否发生改变,研究者可以揭示暗物质粒子和原子内部组成之间的相互作用。这样的发现很有可能会震惊物理学界。
叶军是JILA研究所研究员、美国国家科学院院士
  越来越多的物理学家认为高能粒子对撞机并不是解决物理领域终极问题的唯一方案,Flambaum和叶军就在其中。与对撞机实验不同的是,他们利用精细控制下的原子和激光,去聆听宇宙之弦发出的轻柔乐声。尽管这样的实验可能只需要占用一张桌子的面积,但物理学家正在证明,它们足以用来探测暗物质、观察相对论效应、研究其他的基础物理领域,甚至最终可以探测引力波和量子引力。
  “人们总是问我,你觉得这样的原子钟有什么实际用途?GPS?他们通常会用很实际的眼光看待时钟,”叶军说,“对于我而言,时钟最令人兴奋的方面总是在于研究基础物理。”
  寻找alpha常数
  故事要从一次令物理学界震惊的,对源自宇宙深处的光线的测量开始讲起。在上世纪90年代末,Flambaum的同事,天体物理学家John Webb发现宇宙深处的一个星系传来的光线频率与理论预测不符。观测结果表明,在Webb研究的这个星系中,精细结构常数(fine-structure constant)与在地球上的测量结果大不相同。
  自从1916年Arnold Sommerfeld对氢原子的量子力学结构进行分析后,(在此之前三年,尼尔斯·玻尔刚刚发表了突破性的原子核-电子模型)精细结构常数对于物理学家一直就是一个谜。Sommerfeld把这个常数叫做alpha,它表征了电磁相互作用的强度。电磁相互作用几乎存在于日常生活中随处可见的一切现象中,例如光、电、摩擦、燃烧,是物理学中的基本作用力之一。
  尽管Sommerfeld对刚出现的量子理论做了很大的完善,他的理论中所包含的alpha常数仍然在接下来的一个世纪中困扰着物理学家。正如它的名字alpha所暗示的一样,它亟待被修复或替代。对于物理学家来说,他们总是希望自己的理论是完备的,理论中出现一个看似随机的常数确实是一个大问题。曾获得诺贝尔物理学奖的美国物理学家理查德·费曼写道:“所有优秀的理论物理学家都在试图探寻这个常数的意义。”
  从保罗·狄拉克在1937年发表的论文开始,理论物理学家指出,alpha或者质子/电子质量比这样的基本常数一旦发生改变,现代物理理论的基石(如相对论)将产生裂隙。精细结构常数最终变成了标准模型中20多个经验常数中的一个。标准模型是目前最接近于在基础层面上完整描述宇宙的理论。一个自身变化的“常数”可能暗示着在引力、电磁力、强相互作用和弱相互作用之外,还有第五种基本相互作用存在。换句话说,非定值的alpha可能是通向未知的一扇大门。
  带着这样的期望,Flambaum帮助Webb分析了他得到的有可能带来全新理论的结果。但是Flambaum知道如果没有过硬的证据,物理学家不会接受alpha会改变的假说。他随之想到,新一代基于电子跃迁的原子钟或许可以提供他们所需的证据。与目前掌控着全球时间的微波时钟相比,新一代的“光学时钟”在一秒内包含的波峰数量是前者的五万倍。在几年内,可以用它测量出相当精准的alpha常数,可以与Webb从宇宙深处数十亿年前的光线得到的alpha常数相媲美。
  缩小限制范围
  从某种意义上说,原子是大自然创造的时钟。每一次电子在原子不同能级间的跃迁(也被称为量子跃迁)会发射或者吸收特定频率的光。接近这个特定频率的激光可以诱导原子发光,或者散射其他的激光。通过光子流来驱动反馈信号,物理学家可以将激光锁定在原子跃迁频率。这样得到的激光的波峰就是时钟的“滴答声”。
  原子跃迁频率由这个原子的电子和质子之间的电磁相互作用所决定,而电磁相互作用的强度取决于alpha常数的大小。因此原子钟也间接测量了精细结构常数。确实,我们可以认为整个宇宙的原子都在不断地用自身的性质来测量这个常数,我们所需要做的只是找到观测它们的方法。
  但是这样的实验比想象中要难。要观测alpha常数的变化,需要测量两个原子钟的频率,因为只对一个原子钟测量得到的结果既可以解释为alpha常数的变化,也可能是原子钟自身或者环境的影响。相比之下,两个原子钟频率的比值,是一个仅和alpha常数有关的无量纲量。
  2004年,德国联邦物理技术研究院的物理学家Ekkehard Peik率先迈出了一大步,他比较了光学镱原子钟和微波铯原子钟的频率。为了降低统计不确定度,Peik的团队测量了两个原子钟两周之内的平均频率,并花了一年时间改进它们,然后重新测量了频率。数据显示alpha常数的变化幅度不超过每年一千万亿分之二。这个限制仍然大约为Webb从遥远星系观测得到的alpha常数变化幅度的两倍。
  2008年,在科罗拉多州博尔德的美国国家标准与技术研究院(NIST)的研究者将alpha常数的变化幅度再度缩小,为10-17,他们的方法是舍弃了精准度较低的铯原子钟,改为使用基于铝和汞的光学原子钟。这个实验对Webb的alpha常数出现变化的观测结果是一个很大的挑战。去年,Peik的团队把变化幅度进一步缩小,基于对镱离子钟和锶原子钟的观测,他们宣称初步结果为10-18。
  Flambaum说:“他们不会特别频繁地发表自己的结果,但一旦发表,观测结果的精度就会得到巨大提升。”
  但在原子钟课题组完成他们耗时极长的实验之前,Flambaum也不会仅仅是苦苦等待。他正忙于思考原子钟和基本常数的其他用途。在2015年,他和另一位同事发表了一篇关于暗物质如何使alpha常数产生偏移和波动的论文。他也建议叶军梳理之前收集的原子钟数据,并尝试在其中寻找暗物质的踪迹。
  叶军产生了一个新的想法。“我觉得你的提议可以进一步改进。”他对Flambaum说。
叶军实验室的锶原子钟
  另类暗物质候选者
  Flambaum并不是第一个提议用原子钟来捕捉暗物质踪迹的人。2014年,两位科学家意识到另一类原子钟可以用来探索新物理定律——这类原子钟已经环绕地球超过20年。用于全球定位系统(GPS)的卫星中内含原子钟,用于计算与地球上每一个点的距离。这种原子钟采用微波计时,精度与实验室中有极高工艺水平的原子钟相差了十万倍。但是它们非常可靠,并且始终处于可启用状态。在1996年这些原子钟的数据解密以后,NASA喷气推进实验室的地球科学家建立了接收器,来下载并且储存它们得到的时间数据;时间数据存在轻微的波动,这可能是由于地壳的轻微振动所引起的。
  加拿大圆周理论物理研究所的物理学家Maxim Pospelov和内华达大学的物理学家Andrei Derevianko提出用GPS系统的数据来寻找暗物质。虽然不少科学家认为暗物质可能是至今没有寻找到的弱相互作用大质量粒子(WIMPS),但它也可能由其他有弱相互作用的物质组成。
  有一种暗物质假说包含了普遍存在的超轻量粒子,其质量小于电子质量的一百万分之一。在宇宙大爆炸之后,这些存在于假说中的暗物质粒子可能被冻结为团块状、弦状或墙状。当地球进入或离开与地球大小相当的暗物质团时,暗物质可能会对精细结构常数产生轻微的影响,从而改变卫星上原子钟的频率。时钟突然的变化可能会像波一样传遍整个GPS系统。“目前这仅仅是一个猜测,”Pospelov承认,“但是我们还没有一个合适而且可靠的暗物质模型。所以这个模型的提出或许是一件不错的事情。”
  2017年秋天,Derevianko、Pospelov和他们的同事称,他们在长达16年的GPS系统数据中还没有发现暗物质的踪迹——也就是计时的突然变化,这意味着“拓扑”暗物质理论的限制范围缩小到一千至十万分之一(取决于暗物质团块理论上的尺寸)。
  与此同时,圆周理论物理研究所的理论物理学家Asimina Arvanitaki在考虑探测另一类暗物质候选者的可能性,它们是从试图统一相对论和量子力学的理论中自然诞生的。这些理论中包含了著名的弦论,微小的、无自旋的“类伸缩子”粒子形成了在空间弥漫的场,进而影响alpha常数等基本物理常数。Arvanitaki表示,因为这种粒子与正常物质之间的相互作用非常微弱,它们可能是神秘的暗物质的一个重要组成部分。
  像其他粒子一样,与伸缩子类似的暗物质粒子与量子波有关。并且就像很多可以形成激光的粒子一样,多达10100个暗物质粒子的集合将会自然地形成一束能量巨大且协调的波,其频率和振幅与粒子的质量相关。原子能级以及原子钟的振动频率将会在这种波的频率附近轻微波动。
  不幸的是,弦论没能计算出这个频率。它可能是秒量级,年量级,或者介于它们之间。还好一种叫做傅里叶变换的数学技巧使分析杂乱无章的振动信号成为可能。唯一的限制因素是时间:实验物理学家同时进行两组原子钟频率测定实验,其持续时间时间越长,能寻找的频率区间就越宽。“原则上任何拥有原子钟的人都可以做这个实验,“Arvanitaki说。
  在Arvanitaki的论文发表于论文预印本网站arxiv.org几周后,加州大学伯克利分校的物理学家Dmitry Budker告诉她,他正在试图寻找从镝原子电子跃迁数据中找到这个频率的振动。过了一段时间Budker发表了他的结果,他没有观测到这个特定频率的振动。这项研究将类伸缩子暗物质和普通物质相互作用的限制缩小到一万分之一。不到两年后,巴黎天文台的一个课题组用他们测量铯原子钟和铷原子钟的数据把上述的相互作用限制范围再次缩小了10倍。
  实验物理学家通常需要花费数年来将理论精度提高一个数量级。10000倍的精度提升是一个很大的突破。“这个领域还有很多工作等待发掘,”Arvanitaki说,“你完全可以通过较为简单的工作而取得重大突破。”
  旧数据推动新实验
  上述科学家们的工作掀起了一股分析旧数据的浪潮。在David Hume之后,一位工作于NIST的物理学家在读了Budker的论文并收到Flambaum同事的邮件后,开始分析他的实验室在21世纪初测量铝-汞原子钟的数据。他发现他已经有了世界上用于验证类伸缩子暗物质的最佳数据集。他目前忙于制作性能更好的新原子钟,来测量精细结构常数是否在过去的几十年中产生变动。这项测量很有可能在Peik最新结果的基础上进一步提高精度。
  2015年收到Flambaum的邮件时,叶军正在对课题组里的锶原子钟进行进一步完善,它将会在不久之后打破课题组之前保持的精度记录。他对于探测暗物质的提议非常感兴趣,但是他也在提议中加入了自己的想法。原本的实验方案是将他课题组里的锶原子钟频率与其他类型的原子钟频率进行比较,他提出了替代实验方案,即比较锶原子钟频率和组里用来稳定激光的孔状单晶硅直径。叶军解释道,单晶硅中的孔本身就可以测量精细结构常数的变化,因为孔直径是玻尔直径(原子直径)的整数倍,而玻尔直径受精细结构常数影响。在2017年末,他启动了世界上首项搜寻类伸缩子暗物质的精密实验。迄今为止他已经收集了两个月的数据,并且很有信心地认为这项实验将会刷新目前已发表测量结果的精度。
  目前用原子钟寻找暗物质的实验方案层出不穷,叶军希望通过课题组新建的原子钟,他们可以探索其他关于暗物质的假设,例如2015年Flambaum的邮件中提到的原子钟计时中断。Derevianko设想,将世界上精度最高的原子钟通过光缆相互连接并同时运行,他计算后认为这个实验方案比GPS卫星上的原子钟测量精度高10000倍。在过去两年间,伦敦、巴黎和布伦瑞克已经建立了光纤网络,但将网络扩展到欧洲之外还需要更发达的光纤和卫星通信技术。Derevianko和Budker也在尝试说服原子物理学家公开高精度的数据档案数据,以便于验证层出不穷的新猜想。
  物理学家认为,在没有一个令人满意的理论存在的情况下,这种尽一切可能的方法是正确的策略。“我认为研究者应该穷尽任何可能有新发现的领域。”特拉华大学的理论物理学家Marianna Safronova说。但是原子钟也会存在精度极限,因为物理学家已经花费几十年的时间来完善原子钟技术,从而更加精确地测量时间。“我们不会为了一些费时费力的实验而建造一个超大型的新机器。”Peik说。
  包括Peik在内的数个课题组正在关注一种新提出的原子钟,它不是基于电子能级跃迁,而是原子核内的能级跃迁。大多数的原子核内跃迁的频率极高,但是幸运的是,一种钍同位素的核内跃迁频率落在了激光所能达到的频率范围之内。科学家尚不知道这个频率的确切值,而且激光技术需要进一步发展。但是基于这种原理的原子钟在理论上还是会比当今世界上最好的光学原子钟精确一个数量级。更加精确的原子钟可能在探测引力波和验证量子引力理论等方面有潜在的应用,叶军表示。
  确实,如Arvanitaki所说,这样的原子钟“将会是极精确的测量一切基本物理量的工具。”
  原文链接:
  https://www.quantamagazine.org/ultra-accurate-clocks-lead-search-for-new-laws-of-physics-20180416/



关键词 : 原子钟暗物质美原子
http://blog.sina.com.cn/aganmu;安德(嗨,前一个无辜被封):
http://blog.sina.com.cn/kilarler
说到外星人,也说不定地球生命最初来自于外星呢!光音天在哪里?不过《道德经》倒是提到了不朽的播种者“谷神”:

《道德经·第六章》:“谷神不死,是谓玄牝。玄牝之门,是谓天地根。绵绵若存,用之不勤。”

现在高道不做科研是不了解这句话的深妙含义的!看看这个新闻,谷神星,有机物在火流星中绵绵若存到地球,莫非就是天地根——地球生命播种者!呵呵呵,老子说的没错哟,哟西!道可道,非恒道,名可名,非恒名!无名,天地之始,有名,万物之母!给谷神星命名,却这么巧合像是为《道德经》做验证似的。到底是不是言与神同在呢?
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癯鹤 发表于 2018-1-21 22:08
万里古德,万里谷德!神农氏,谷神星,其中有道,其中有根!







'Building blocks of life' may exist on the dwarf planet Ceres in higher amounts than thought
  • New analysis of Dawn data suggests Ceres has more abundant organic material
  • The material was first revealed last year, in patches seen in a northern crater
  • Scientists say it may have been produced on Ceres, or brought by comet impact

By Cheyenne Macdonald For Dailymail.com

Published: 20:19 BST, 14 June 2018 | Updated: 21:02 BST, 14 June 2018


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The dwarf planet Ceres may be even better suited for supporting life than previously thought.
A new analysis of data from the Dawn spacecraft suggests previously-identified patches of organic material on the surface may contain much higher abundance of carbon-based compounds than initially estimated.
While it doesn’t mean life exists on the dwarf planet, the discovery adds new clues to the question of Ceres’ potential habitability.
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Scientists first announced the discovery of organic material – a necessary component for the existence of life – last year. Organics can be produced through non-biological processes as well. Just how they arrived on Ceres, however, remains a mystery

‘What this paper shows is that you can get really different results depending upon the type of organic material you use to compare with and interpret the Ceres data,’ said Hannah Kaplan, a postdoctoral researcher at the Southwest Research Institute, who led the research while attending Brown University.
‘That’s important not only for Ceres, but also for missions that will soon explore asteroids that may also contain organic material.’
Scientists first announced the discovery of organic material – a necessary component for the existence of life – last year.
Organics can be produced through non-biological processes as well.
Just how they arrived on Ceres, however, remains a mystery.




As the planet is also known to contain an abundance of water ice, scientists say the possibility of more widespread organic material is certainly intriguing.
The Dawn spacecraft orbited the dwarf planet in 2015, and captured signals consistent with organic molecules in the Ernutet Crater on the northern hemisphere.
The team then compared the data with laboratory reflectance spectra of organic material on Earth.

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A new analysis of data from the Dawn spacecraft suggests previously-identified patches of organic material on the surface may contain much higher abundance of carbon-based compounds than initially estimated

In the latest analysis, researchers re-examined the data to compare it with material seen in meteorites, which have been known to contain organic material that is slightly different than that seen on Earth.
‘What we find is that if we model the Ceres data using extraterrestrial organics, which may be a more appropriate analog than those found on Earth, then we need a lot more organic matter on Ceres to explain the strength of the spectral absorption that we see there,’ Kaplan says.
‘We estimate that as much as 40 to 50 percent of the spectral signal we see on Ceres is explained by organics.
‘That’s a huge difference compared to the six to 10 percent previously reported based on terrestrial organic compounds.’
WHAT IS THE DWARF PLANET CERES AND WHY IS NASA STUDYING IT?Ceres is 590 miles (950 km) across and was discovered in 1801.
It is the closest dwarf planet to the sun and is located in the asteroid belt, making it the only dwarf planet in the inner solar system.
While it is the smallest of the known dwarf planets, it is the largest object in the asteroid belt.
It lies less than three times as far as Earth from the sun - close enough to feel the warmth of the star, allowing ice to melt and reform.
Nasa's Dawn spacecraft made its way to Ceres after leaving the asteroid Vesta in 2012.
There is high interest in the mission because Ceres is seen as being a record of the early solar system.

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According to the researchers, there are two likely explanations for Ceres’ organic material: production on the planet itself and later exposed to the surface, or import from an impact by a comet.
‘If the organics are made on Ceres, then you likely still need a mechanism to concentrate it in these specific locations or at least to preserve it in these spots,’ said Ralph Milliken, an associate professor in Brown’s Department of Earth, Environmental and Planetary Sciences.
‘It’s not clear what that mechanism might be. Ceres is clearly a fascinating object, and understanding the story and origin of organics in these spots and elsewhere on Ceres will likely require future missions that can analyze or return samples.’
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本帖最后由 癯鹤 于 2018-9-18 19:08 编辑
说到外星人,也说不定地球生命最初来自于外星呢!光音天在哪里?不过《道德经》倒是提到了不朽的播种者“谷神”:

现在高道不做科研是不了解这句话的深妙含义的!看看这个新闻,谷神星,有机物在火流星中绵绵若存 ...
癯鹤 发表于 2018-1-21 22:08
Ceres——Seres,谷神——塞里斯,神农氏鬼方真是古老,而且老外为啥很早就知道?赤狄、白狄、戎胡很早就西征,也是欧人祖先基因和文化的来源之一。

NASA发现冰火山 冰火山在哪里 冰火山喷发的物质是什么




2018-09-18 16:33:29科技日报


据英国《自然·天文学》杂志17日在线发表的一项研究,美国国家航空航天局(NASA)的“黎明”号小行星探测器首次发现,矮行星谷神星(Ceres)上的冰火山“从未沉默”,其曾在历史上不断喷发。这一发现能让人类更多地了解太阳系的起源和行星的形成。

与地球火山喷发熔岩不同,冰火山喷发的是液体或气体挥发物,如氨气、水或甲烷。此前在外太阳系的多个天体上都已发现了冰火山活动的痕迹。2015年,“黎明”号探测器入轨谷神星,并发现了一座圆拱型山峰,这座名为阿胡纳火山(Ahuna Mons)的山峰被认为是一座冰火山。不过从那以后,谷神星上尚未发现过类似构造的物体。

科学家认为,冰火山穹丘会逐渐变得扁平,并最终与周围地形融合。基于这种观点,美国亚利桑那大学天文学家迈克尔·索利及其同事,此次运用了穹丘形状较平的模型,在“黎明”号探测器拍摄的谷神星照片上找到了22个曾是冰火山的位置。通过对这些冰火山的年龄进行估算,研究人员发现,在过去的10亿年里,谷神星上平均每5000万年就有新的冰火山出现。

据研究团队估算,喷发到谷神星表面的结冰物数量是地球、月球、金星和火星上火山喷发的熔岩数量的百分之一到十万分之一。不过,与地球上标准的火山活动相比,谷神星上持续不断的火山活动并未对其表面造成同等程度的广泛影响。

“黎明”号小行星探测器是历史上第一个探测小行星带并造访矮行星的人造设备,开启了人类探索太空的新纪元。2017年,“黎明”号在谷神星一处火山口附近检测到有机物质,这是人类第一次在小行星带发现有机化合物,而其正是地球上生命的基石。




终极之源,忠极之渊,唯冰夷恒都焉。有穷氏、有寒氏、寒武纪、冰火山!


The 'explosion of life' on Earth 500 million years ago was NOT sparked by meteorites?
  • Cambrian explosion saw a vast number of new species explode onto the scene
  • Researchers believe an increase in meteorite impacts might have played a role
  • But it appears the moon did not experience more impacts during this period
  • Study suggests the samples collected in the 1960s during lunar missions were skewed towards recording only the most recent activity
By PHOEBE WESTON FOR MAILONLINE
PUBLISHED: 19:01 BST, 17 September 2018 | UPDATED: 19:11 BST, 17 September 2018
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The Cambrian explosion of early life on Earth may not have been caused by an increase in meteor strikes 500 million years ago, a prominent professor has suggested.
The Cambrian explosion was a time when a wide variety of animals burst onto the evolutionary scene and the diversity of life began to resemble that of today.
Some researchers thought that an increase in meteorite impacts might have played a role in this.
However, it seems that the moon did not experience more meteorite impacts during this period.
Instead a new study suggests that the samples collected in the 1960s Apollo missions were skewed towards recording more recent activity as they just scraped the surface rather than drilling down.
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The Cambrian explosion of early life on Earth may not have been caused by an increase in meteor strikes 500 million years ago, a prominent professor has suggested. Pictured is an astronaut taking lunar samples in the 1960s  

Much of the evidence from Earth's early history has been destroyed by plate tectonics and weathering so astronomers often look to the moon and Mars for clues about our beginnings.
When meteors crash into the moon, the impact creates so much heat that it melts the surface.
Some of that melt product cools and eventually becomes shiny little orbs known as lunar glass spherules.
Ya-Huei Huang, a graduate student in earth, atmospheric and planetary sciences at Purdue University in Indiana, looked to these spherules for clues about the rate of meteoroids crashing into the moon.
The samples they looked at were collected by Apollo astronauts in the 1960s.
They found the same number of beads dated to the last 500 million years as from the previous four million years.
This coincides with the Great Ordovician Biodiversification Event (GOBE) which vastly expanded marine life diversity.

It kicked off about 70 million years after the first explosion of life on Earth during the preceding Cambrian period, some 540 million years ago.
Some scientists contend that the Ordovician event was sparked by a collision of objects in the asteroid belt between Mars and Jupiter raining debris down on our planet.
'If there was this increase in impacts around the same time, it would support the idea that life was stimulated or seeded by organic molecules from elsewhere in the solar system,' Professor Paul Renne from the Berkeley Geochronology Center in California, who was not involved in the research, told New Scientist.  
Such a bombardment may have changed the environment just enough to stimulate diversification of existing life, the theory goes.
However, if this increase turns out not to be true, scientists will have to look for other explanations, said Professor Renne, an expert in Earth and planetary science.

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The samples they looked at were collected by Apollo astronauts in the 1960s (pictured). They found the same number of beads dated to the last 500 million years as from the previous four million years

Most of the spherules were relatively young, which might indicate that the rate of impacts on the moon has increased in the recent past.
However, Dr Huang and his team were sceptical of this interpretation.
'[It] has remained a mystery as to whether this is because the impact rate was higher in the recent past, or if there was some process that was biasing these samples toward a young age', scientists wrote in the paper published in Geophysical Research Letters.
Co-author Nicolle Zellner, a researcher at Albion College, created a model for the formation and distribution of lunar glass spherules.
WHAT WAS THE 'CAMBRIAN EXPLOSION'?Scientists have long speculated that a large oxygen spike during the 'Cambrian Explosion' was key to the development of many animal species.
The Cambrian Explosion, around 541 million years ago, was a period when a wide variety of animals burst onto the evolutionary scene.
Before about 580 million years ago, most organisms were simple, composed of individual cells occasionally organised into colonies.
Over the following 70 or 80 million years, the rate of evolution accelerated and the diversity of life began to resemble that of today.
It ended with the Cambrian-Ordovician extinction event, approximately 488 million years ago.

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A recent study linked the historic rise in oxygen responsible for the formation of animal life on Earth to fossil fuels. Pictured: This black shale, formed 450 million years ago, contains fossils of trilobites and organic material that helped support these in oxygen


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She found the impact rate on the moon has most likely been constant but that the small sample of spherules collected was biased toward younger impacts.
'We find that the young age bias is only seen because the Apollo samples were collected in the upper few centimeters of the lunar surface', researchers wrote.
'The astronauts used a rake to collect samples from the surface of the moon, but if they were able to take samples from a few meters deeper, we might see a more accurate age distribution,' said David Minton, a professor of earth, atmospheric and planetary sciences at Purdue who oversaw the research.
'If we ever go back to the moon, we could collect samples differently and actually see if the rate of impacts has changed.'
Understanding the impact rate is an important part of understanding the history of life on Earth.
Such impacts have casued mass extinctions, such as that of the dinosaurs.
Because Earth has destroyed most of the evidence of its ancient history, the moon is an important piece of this puzzle.
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