The Last Prediction by Einstein is Verified: Scientists Announce The First Direct Detection Of Gravitational Waves

愛因斯坦最後的預測得到證實:科學家宣佈首次偵測到重力波

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By  Frederico Arroja

On Thursday, the 11th of February of 2016, an international team of scientists, including physicists from the LIGO and VIRGO collaborations, announced [press conference link] the discovery of gravitational waves as predicted by A. Einstein 100 years ago.

“Ladies and Gentlemen, we have detected gravitational waves. We did it!” Prof David Reitze, executive director of the LIGO project announced to a room packed with journalists in Washington DC.

Gravitational waves are “ripples” in the fabric of spacetime and according to Einstein’s theory of General Relativity they are produced every time masses are moved around.

The gravitational wave signal was measured by both LIGO detectors on the 14th of September of 2015 at 09:50:45UTC and it originated from a binary black hole merger at about 1.3 billion light-years away from Earth and came from a direction in the Southern Hemisphere.

 The masses of the two black holes that collided were about 36 and 29  solar masses and the peak velocity during the collision was about 60% of the speed of light. The signal was visible for about 0.2 seconds and released an energy equivalent to about 3 solar masses. That is 50 times more energy than the total energy released by all the stars in the visible Universe during that time. The final product of the collision was a single massive black hole of about 62 solar masses.

These waves have been traveling to us since the collision happened 1.3 billion years ago and when they entered the detector they deformed it by a tiny amount, approximately one thousandth of the size of a proton.

This historical discovery is so remarkable and important because firstly it is a direct confirmation of the last major prediction of General Relativity and secondly it opens up a whole new way of exploring our Universe. It constitutes a revolution in Astronomy akin to when about 400 years ago Galileo pointed his telescope at the sky and observed the planets and satellites of our Solar System.

This amazing discovery also has implications for the search of the final theory of quantum gravity, a search that is being carried out also by researchers at LeCosPA.

A series of research papers has been posted to the arXiv online repository  and LIGO website  and the discovery paper has been published in the peer-reviewed journal Physical Review Letters . A more technical commentary on the discovery can be found here.

Find out more about the detectors and the teams

The Laser Interferometer Gravitational-Wave Observatory, LIGO, is a system of two identical L-shape detectors, each with two arms about 4km long that have been built in two distinct locations in the USA (Livingston, Louisiana and Hanford, Washington) and are able to detect incredibly minute deformations of the length of their arms caused by passing gravitational waves. They were built by MIT and Caltech researchers and funded by the USA National Science Foundation with other major contributions coming from several USA and international partners.

VIRGO, is a detector similar to the LIGO detectors that is located near Pisa, Italy, and will restart operations later this year. The LIGO and VIRGO collaborations include about 1000 scientists from 80 institutions in 15 countries around the world. Find out more about LIGO and VIRGO in http://www.ligo.org/ http://public.virgo-gw.eu/language/en/

文章 艾若哲 / 翻譯 陳勁豪

2016年二月十一日,來自LIGO及VIRGO兩個團隊的一群國際科學家正式宣佈發現了愛因斯坦於一百年前所預測的重力波的存在。

LIGO計畫的主持人David Reitze教授在華盛頓在座無虛席的記者會現場宣佈:”各位女士先生,我們已經偵測到了重力波。我們做到了。”

重力波是時空結構受到擾動所產生的漣漪。根據愛因斯坦的廣義相對論,當帶有質量的物體運動的時候,就會產生重力波。

兩部LIGO偵測器是在2015年九月十四日世界標準時間上午九點五十分四十五秒偵測到重力波的訊號。這個重力波訊號是由離地球十三億光年遠的兩個雙星黑洞於合併的過程中所放出,而且約略是由南半球的方向傳來的。

這兩個相互碰撞的黑洞質量分別為36跟29個太陽質量,而碰撞過程中的最大速度約略是光速的60%。這個重力波的訊號大約維持了0.2秒,合併過程中所放出的總能量相當於三個太陽質量。因此所放出的總能量約略是當時可見宇宙所放出的總能量的五十倍。兩個黑洞合併後的新黑洞,質量大約是62個太陽質量。

這些重力波經過了十三億年的旅行而被偵測器探測到。重力波對偵測器產生了極微小的形變,約略是質子尺寸的千分之一而已。

這個歷史性的發現之所以重要是因為這是對愛因斯坦的廣義相對論最後一個重要預測的直接觀測證據。

這個重要的新發現將對尋找量子重力理論的發展產生影響,這也是台大梁次震宇宙學與粒子天文物理學研究中心的主要研究課題之一。

與此發現的一系列相關論文可以在arXiv網站LIGO的官方網站上找到。刊載這個重要發現的論文已經發表於物理評論通訊(Physical Review Letters)上。更技術性的討論可以參考此連結

更多關於偵測器與研究團隊的資訊

雷射干涉重力波觀測站(Laser Interferometer Gravitational-Wave Observatory, LIGO)是一個由兩具完全相同的L型偵測器所構成的實驗。每具L型偵測器的兩臂各約4公里長,並分別設置在美國路易斯安那州的Livingston及華盛頓州的Hanford。這些偵測器可以偵測到偵測器兩臂因為重力波影響所造成的微小形變。這個實驗主要由麻省理工學院及加州理工學院的研究人員所建立而成,並由美國的國家科學基金會及其他國際團隊共同出資。

VIRGO位於義大利比薩附近,是一個類似LIGO的偵測器。VIRGO預計今年稍晚會重新開始運作。LIGO跟VIRGO團隊由來自15個國家,80個研究單位,共約一千位科學家所共同組成。更多關於LIGO跟VIRGO的介紹可以參考以下網站:http://www.ligo.org/ http://public.virgo-gw.eu/language/en/