PHYS1160: A NEW WAY TO DISSCOVER THE

 

 

 

 

 

PHYS1160:

A NEW WAY TO DISSCOVER THE UNVERISE

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GRAVITATIONAL WAVE

 

 

By:      Chun-Hung Hsiao             Z5018919

  

 

 

 

 

University of New South Wales

School of Civil and Environmental Engineering

 

JANUARY 2018

introduction

In the past, scientist has inspect the mystery behind the universe through different type of electromagnetic radiation include visible, radio, microwave etc. However these radiation all have limitation since they will interact with the surrounding things when they pass by. On 11th of February 2016, the announcement was made of the detection of gravitational waves from space using the Advanced LIGO facility. Gravitational waves are new types of waves that travel in space with speed of light (where C = 299 792 458 m / s). Gravitational waves are not waves that created or part of Gravitational field, it is a completely new phenomena.

The typical events that generated gravitational waves include:

·         Supernova-when a star explodes asymmetrically

·         When two stars orbit each other

·         When two black holes orbit each other and merge

The main discussion of the essay will be about these three question:

·         What is gravitational wave?

·         How does LIGO detect them?

·         Why is this discovery significant?

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

What is gravitational wave?

Gravitation waves are the ripples in space that cause due to some of the most cataclysmic event in the universe. The prediction of existence of Gravitation wave were bring out in 1946 but its proof existence wouldn’t come to earth until 1974 since it  created by intense cataclysmic event and it’s far away from us. The famous scientist Albert Einstein has subsequently predicted the existence of Gravitational wave in 1916 through his general theory of relativity:

“The laws of physics are the same for all non-accelerating observers and that the speed of light in a vacuum was independent of the motion of all observers.” (Nola Taylor Redd, 2017)

Einstein’s calculations had shown when accelerating objects such as neutron stars or black holes orbiting each other would interfered the space time in a form of “ripples” and distorted space would radiate from the source of the “ripples”, which is the gravitational wave.

The strongest gravitational waves are produced by catastrophic events such as:

·         Colliding black holes

·         Supernova: the collapse of Stellar Cores

·         Merging neutron stars

·         The slightly wobbly rotation of neutron stars that are not perfect spheres

·         The remnants of gravitational radiation created by the birth of the Universe itself

NSF, LIGO, SONOMA STATE UNIV., A. SIMONNET

CRASH AND WAVE   In a galaxy 130 million light-years away, two neutron stars collided. This year, in the first detection of its kind, observatories caught the resulting gravitational waves and light show (illustrated). (EMILY CONOVER, 2017)

For the case of merging neutron stars, the gravitational waves intensity are independents on the orbiting speed and the distance between them. The Gravitational wave intensity will increase while the orbiting speed increase and the distance between the neutron stars reduce. The gravitational waves will travelling at the speed of light (C = 299792458 m/s) through space.

 

Sequence showing two white dwarfs spiralling into one another, merging and then exploding as a supernova. As they spiral around each other, they emit gravitational waves causing them to grow ever closer. Credit: GSFC/Dana Berry. (Astro Bob, 2015)

Base of the theory and prediction on the source of Gravitational wave, it can come from many different types of event. Any object with mass that accelerates can produce gravitational wave which from the biggest object Stars and black holes to the smallest object air-plane and cars. However the gravitational wave created in such a small bodied will be too weak for us to detect. It is impossible to building machines for experimental since we still unable to build a machine that can rotate fast enough to generate the Gravitational wave that’s detectable and building a machine that can maintain in one piece in such high speed rotation. Therefore our only way to observe Gravitational waves are through observing natural cataclysmic event in the universe that will generated Gravitational wave.

There are four type of Gravitational wave that has been discover and categorise so far:

·        
Continuous Gravitational Wave is a continuously wave with identical frequency and amplitude. This type of wave produced by singular spinning huge mass such as neutron star. The Star is spinning at the constant rate and the Gravitational waves are generated from the imperfection surface of the spherical shape during spinning.(Laser Interferometer Gravitational-Wave Observatory, 2015)

Artist’s depiction of a super dense and compact neutron star (Casey Reed/Penn State University)

·         Compact Binary Inspiral Gravitational Waves is produced by orbiting pairs of massive and dense bodies such as white dwarf stars, black holes and neutron stars. Furthermore, there are three different type of Compact Binary Inspiral Gravitational Waves:

o    Binary Neutron Stars ( a pair of Neutron Stars),

o    Binary Black Hole(a pair of Black Holes)

o    NSBH (Neutron Star pair with Black hole).

Each type of Compact Binary Inspiral Gravitational Wave has their own characteristic series but still in the inspiral mechanism. The inspiral of pairs of orbiting stars are refer to the characteristic of:

o    The System’s orbital energy will be transfer and create Gravitational wave

o    As the orbital energy lost, the orbiting bodies will merge and getting close

o    The distance between the merging stars reduce and the orbiting speed will increase, hence the orbiting energy will be continuously loosing

o    Inescapable lock into an runaway accelerating spiralling embrace after infinite loops and become dome

(Laser Interferometer Gravitational-Wave Observatory, 2015)

This computer simulation shows the collision of two black holes, as observed for the first time ever by the LIGO on September 14, 2015. The black holes in the animation are based on the actual data from the collision as detected by LIGO. (Simulating eXtreme Spacetimes (SXS) Project (http://www.black-holes.org))

 

·         Stochastic Gravitational Waves are waves that mixed together at random pattern from the Universe. They are possibly continuous combine with Binary Inspiral Gravitational waves. They are so weak to detect since they have random pattern and weak in intensity. They are possible generated from Big Ban. Detecting these waves can allow us to see farther back into the history of the Universe than ever before but the scientist consider these are the least important compare to other type of Gravitational Wave at the moment. (Laser Interferometer Gravitational-Wave Observatory, 2015)

·         Burst Gravitational Waves are the Gravitational waves that been classify as unexpected wave that we haven’t detected. We are still not fully understand about the physics of the gravitational wave and exactly understand how the gravitational wave are generated from particular source during prediction. For further observations on the Burst Gravitational wave, the scientist must maintain concentrate to recognise different type of Gravitational wave with particular pattern. (Laser Interferometer Gravitational-Wave Observatory, 2015)

 

 

 

 

 

how does ligo dectect them?

LIGO is a Gravitational-Wave interferometer and it is one of the largest Gravitational wave observatories in the world .They are located in Washington and Louisiana.

LIGO observe Gravitational wave by observing the space stretches when it passes Earth. LIGO observatory’s 4km arms are design to detect the stretches by observing the slightly length changes of the arms when Gravitational wave pass by. The observation might be very tiny since the source of wave are very far away from us, usually billion light years away. Therefore the observatory will uses extremely sensitive instruments such as lasers and reflective mirrors to detect any tiny changes on the arms.

LIGO study the properties of light and space to detect the origins of Gravitation wave. LIGO has three properties that distinguish it from other observatory such as telescope and satellite:

1.       LIGO cannot observe electromagnetic radiation such as visible light, radio waves and microwaves. LIGO can only detect and observe Gravitational wave.

2.       LIGO do not need to observe visible light or any other electromagnetic, therefore it doesn’t need to have dish-shaped mirror that telescope has to produce visualisation data. LIGO has two 4km straight tubs and layout as an L shape as an observer for gravitational wave. The facility is protected from concrete enclosure.

An exposed segment of LIGO Livingston’s vacuum tube. (Credit: Caltech/MIT/LIGO Lab)

Right: Access road next to one of LIGO Hanford’s concrete-encased vacuum tubes. The mid-station is barely visible 2 km away. (Credit: Kim Fetrow/Image works)

3.      
LIGO need to operate in unison with another pair of interferometer distant away to allow the local vibration will catch the correct signals from gravitational waves, as a result LIGO can’t function solo. This is also call LIGO’s Dual Detectors.

The general locations of the LIGO Hanford and LIGO Livingston interferometers.

(Credit: Caltech/MIT/LIGO Lab)

 

why is this discovery SIGNIFICANT?

The Gravitational waves that are detectable by LIGO from the cataclysmic event happens in the universe which allow scientist to understand deeper about the cataclysmic events happen in the universe. Provide deeper research in physics astronomy and astrophysics.

In the past, human were alone able to study and observe about the universe through electromagnet radiation include visible light, radio wave and microwave. Each of these sources provide the scientist different view of the universe, Gravitational wave can be an exciting new discoveries for human to discover the universe through a new way.

Gravitational waves are not electromagnetic radiation and it is completely new phenomenon. Gravitational wave can provide other information that electromagnetic radiation cannot carry from the objects and events from the Universe. For example, Colliding black holes will create and emit tiny electromagnetic radiation that cannot be detected by Earth. However, colliding black holes create and emit Gravitational wave. Unlike electromagnetic radiation, Gravitational waves interact weakly with other matter when pass by which might provide a clear view about the universe to us compare with electromagnetic radiation.

Therefore the study on Gravitational waves provide us a better understanding about the nature of the Universe, space and time itself.

 

 

 

 

 

 

 

Bibliography

Astro Bob (2015) Doomed Stellar Relationship To End In Supernova Catastrophe. Available at: https://astrobob.areavoices.com/2015/02/09/doomed-stellar-relationship-to-end-in-supernova-catastrophe/ (Accessed: 18 January 2018).

EMILY CONOVER (2017) ScienceNews?Gravitational waves, ScienceNews. Available at: https://www.sciencenews.org/editors-picks/gravitational-waves (Accessed: 8 January 2018).

Laser Interferometer Gravitational-Wave Observatory (2015) Sources and Types of Gravitational Waves | LIGO Lab | Caltech. Available at: https://www.ligo.caltech.edu/page/gw-sources (Accessed: 10 January 2018).

Nola Taylor Redd, S. co. C. (2017) Einstein’s Theory of General Relativity: A Simplified Explanation, By Nola Taylor Redd, Space.com Contributor. Available at: https://www.space.com/17661-theory-general-relativity.html (Accessed: 18 January 2018).

 

 

 

 

 

 

 

 

 

 

 

 

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