What have we discovered in Gravitational Waves?

By Stephen Hughes

Earth

In 1915, ten years after the publication of the theory of special relativity, Albert Einstein published a new theoretical description of gravity, the theory of general relativity. Before general relativity, gravity was understood in terms of Newton’s law of gravitation, which gives excellent agreement between the predicted and observed positions for most of the planets in the Solar System. However, the predictions regarding the planet Mercury’s orbit around the Sun are slightly wrong. One of the first confirmations that general relativity was the correct description of gravity came from the theory accounting for this discrepancy. A theoretical model, such as general relativity, should lead to a better understanding of the phenomena it is trying to describe. There should also be predictions regarding the outcome of experiments when measurements are made. Ideally the predictions should not only explain what is already known but provide some insight into new effects. General relativity gives many predictions regarding previously unknown effects while accounting for everything that is already known from Newton’s work.

Physics Motion

In 1916 Einstein found his theory predicted the existence of gravitational waves. Many of the other predictions of general relativity have been confirmed experimentally in the early decades that followed. Einstein’s gravitational waves have eluded direct experimental confirmation for a century, leaving some uncertainty if they actually exist. During the past century many experiments have been designed to detect and study gravitational waves. The instruments used to detect gravitational waves need to be extremely sensitive to small disturbances in space-time. Gravity is the result of mass and energy curving space-time. Gravitational waves are ripples in space-time, propagating at the speed of light. When propagating through a region of space-time, the gravitational waves change the curvature of space-time by a small amount in that region. This is what the experiments try to measure. Only large scale processes, such as the collision of two stars, are likely to produce significant gravitational waves to be detected based on present instrument sensitivity. Gravitational waves carry away some of the energy from the collision. Detecting and measuring the gravitational waves gives information about the colliding masses.

In September 2015 the gravitational wave detectors comprising LIGO (Laser Interferometer Gravitational-Wave Observatory), resumed after undergoing an upgrade designed to increase the sensitivity of the instruments. Shortly after this upgrade in February 2016 the paper ‘Observation of Gravitational Waves from a Binary Black Hole Merger’ was published in the journal Physical Review Letters. This work represents the collaborative effort of a large team of scientists, engineers and mathematicians from different countries, working together over many years. Their work documents the first direct confirmation of gravitational waves. While this is a triumphant confirmation of Einstein’s ideas about gravity it is also the beginning of a new era of astronomical observations. Traditionally objects in the Universe are observed by collecting visible light through the aperture of a telescope. Visible light represents only a small range of the electromagnetic spectrum. Observing the Universe using only visible light restricts the information that can be obtained. Extending the range to include other parts of the electromagnetic spectrum gives more information, leading to a better understanding. When viewing nebulae, the birth place of stars, while only detecting visible light, the features of these systems can be obscured by a large cloud of gas and dust surrounding the newly forming stars. However, observing the same systems with detectors sensitive to light from other regions of the electromagnetic spectrum reveals more structural detail. The gas and dust in this case are not preventing the light from leaving the system.

Space Small

Astronomers now have a new technique for observing objects and events in the Universe. These first gravitational waves measured by LIGO originated when two black holes merged together, the first time this type of event has ever been observed. There are presently several gravitational wave detectors being constructed and others planned for construction in the near future. Perhaps the most promising of these are DECIGO (DECI-hertz Interferometer Gravitational wave Observatory), and eLISA (Evolved Laser Interferometer Space Antenna), which are anticipated to be launched in 2027 and 2038 respectively. These space based instruments will be more sensitive and capable of detecting gravitational waves from a greater range of astronomical events. Since gravitational waves also travel through space-time unaffected by other events, those produced in the early Universe are still propagating through space-time today. If measured these primordial gravitational waves could lead to a better understanding of the origin of the Universe.

To learn more about Einstein’s general relativity, space-time and gravitational waves why not enrol onto 101 Years of General Relativity with Stephen Hughes starting Monday 4th April 2016 you can enrol here

5th Annual Archaeology and the Bible Day conference:Persia and the Bible

5th Annual Archaeology and the Bible Day Conference

Theme: Persia and the Bible

Saturday 14th May 2016, 10am – 4.30pm

Persia and the Bible

For many centuries the Bible – both Old and New Testaments – has been subject to rigorous academic scrutiny. While some have defended the Bible by resorting to simplistic or wild, unustainable claims, others have dismissed it without reference to the cultures and literature that were contemporary with it. The tradition of the Archaeology department of the University of Liverpool over many decades, as exemplified by Dr. William Martin and Professors Kenneth Kitchen and Alan Millard, is upheld by this successful annual conference. The Bible is examined critically within its contemporary context, but theoretical and unprovable assumptions as to its origins are not given weight. This year sees the fifth such annual conference. Having considered Treaty, Law and Covenant, Egypt, the New Testament and Babylon over the past four years, this year we turn our attention to the Bible’s connections with ancient Persia.

Timetable 

10.00am(1 hour)     Dr. Paul Lawrence – The Medes and Persians in the Bible and beyond
  From being an inspiration for US mail, the UN Declaration of Human Rights, the late Shah of Iran and modern Kurdish nationalism it can be argued that the Medes and the Persians still influence modern affairs. After looking at the history of both peoples in brief overview we shall consider their role in Bible history. What archaeological evidence is there to substantiate the Bible’s claims that Daniel, Esther, Ezra and Nehemiah all prospered under Persian rulers?
11.00am(30 mins) Break (Refreshments in Foyer)
11.30am(1 hour) Prof. Christopher Tuplin (The University of Liverpool) – The Fall and Rise of the Jewish Temple at Elephantine.
  One day (or perhaps night) in July-August 410 BC the Jewish Temple on Elephantine Island, near the first cataract of the Nile, was ransacked and burned by a group of Egyptians led by a Persian officer. This lecture discusses the causes and consequences of  this violent event and puts them in the wider context of Persian attitudes to the non-Persian religions of their imperial subjects.
12.30pm(1 hour) Lunch (in Foyer) 
 
1.30pm(1 hour) Emeritus Professor Alan Millard (The University of Liverpool) – Aramaic – the Language of the Persian Empire 
  Under the Persian kings, Aramaic was used from Afghanistan to Egypt, from Turkey to Arabia. The lecture will begin with the earliest specimen of Aramaic, inscribed statue of a ruler in the 9th century B.C.,observe its spread under Assyrian and Babylonian kings until it became the international language of the Persian Empire. Most of the Aramaic documents were written perishable materials, but some survive in dry places, and with texts on stone and notes on potsherds they illustrate aspects of life in the empire and set the letters in Ezra 4-7 and other biblical texts in their contexts.
2.30pm(30 mins) Break (Refreshments in Foyer) 
3.00pm(1 hour) Dr. Selim Adalı (Social Sciences University of Ankara) – Persia in the Book of Ezekiel
  Ezekiel 38:5 refers to Persia alongside Cush and Put, as nations gathered around Gog and Magog. Such mention of Persia has aroused much discussion among scholars. This paper seeks to go through the reception of Persia in the Book of Ezekiel. The case is made that Persia was a recognized region and kingdom before its rise as an Empire under the Achaemenid dynasty. To this end, Assyrian and biblical references to Persia are presented. This provides for the opportunity to discuss the origins of the Persian Kingdom and its transition into the Achaemenid Empire.
4.00pm(30 mins) Questions for the SpeakersIf you would like to book on this course – click here Persia and the Bible booking