Analysis of the State-of-Art Observations for Gravitational Wave

Searching

Shaoping Deng

College of Electrical and Information Engineering, Hunan University, Changsha, China

Keywords: Gravitational Wave, Detection, LIGO, Universe Exploration.

Abstract: Gravitational wave is one of the most mysterious things in the universe. Proposed by the General Relativity,

which is Einstein’s theory, this kind of wave is what scholars have long wanted to detect and understand. The

essence of gravitational waves is the spatiotemporal disturbance caused by mass motion, propagating at the

speed of light, but difficult to detect due to their extremely low intensity. With the development of high-

precision measurement technology, especially the application of laser interferometry technology,

gravitational wave detection has gradually become a research focus. Gravitational wave detection not only

provides new avenues for exploring the universe, but also helps reveal the origin, structure, and properties of

extreme celestial bodies such as black holes and neutron stars. These results give some knowledge about

gravitational wave and introduces some projects in detecting gravitational wave. There are some projects such

as the LIGO, the LISA, Taiji Plan and Tianqin Plan aiming to detect gravitational wave signals.

1 INTRODUCTION

Gravitational wave is a great prediction in Einstein’s

general relativity, and it is a space-time disturbance

caused by mass motion. It travels at the speed of light.

Because of the low intensity of its light body, it is

difficult to be detected. The detection of gravitational

wave began in the 1960s, when Weber used his

resonance mass spectrometry detector to do this

experiment (Weber, 1960). The detection of

gravitational wave is always an important research

subject in the field of physics and astronomy, and it

gradually become possible because the progress of

technology, especially the development of high-

precision measurement technologies such as laser

interferometers. The earliest proposed gravitational

wave dictation scheme in the world was the Laser

Interferometric Space Antenna (LISA) program

proposed by the European and American Union

(ESA&NASA) in 1973 (Martens and Joffre, 2021).

The meaning of detecting gravitational wave is

that it provides a brand new observation method,

which will uncover so many unknown rules and

phenomenon in the university. At present, the

domestic and abroad program of gravitational wave

detection include the LISA (Hammesfahr, 2001;

https://orcid.org/0009-0004-3077-723X

Jennrich 2009) and the Tianqin program led by Sun

Yat sen University (Luo et al., 2016). One can

understand the universe deeper by detecting the

gravitational wave, including the origin, evolution

and structure of the universe, and characters of black

holes and neutron stars.

After the concept of gravitational waves was

proposed, scientists began to detect gravitational

wave. However, because of the restrict of low

technique, the early detection experiment has not

made substantial progress. Until the beginning of 21

century, the detection of gravitational wave made a

breakthrough. In 2015, the LIGO in the USA detected

the gravitational wave for the first time. This

discovery was hailed as the greatest discovery of

physics in 21 century, and the discovery meant that

the epoch of gravitational wave had come. After this

discovery, LIGO cooperated with the VIRGO

Laboratory in European and achieved a series of

important results.

Although there are many achievements in

detecting gravitational wave, there are still some

problems in this detection. The signal of gravitational

wave is so weak that it is difficult to be detected, and

the detection need high precision instruments.

Gravitational wave detection is an expensive project,

264

Deng, S.

Analysis of the State-of-Art Observations for Gravitational Wave Searching.

DOI: 10.5220/0013074700004601

Paper published under CC license (CC BY-NC-ND 4.0)

In Proceedings of the 1st International Conference on Innovations in Applied Mathematics, Physics and Astronomy (IAMPA 2024), pages 264-268

ISBN: 978-989-758-722-1

which requires a significant amount of manpower,

material resources and financial resources. The

detection also need to solve some technical

challenges including improving the sensitivity of the

detector, expanding the detection frequency range,

etc. These problems stimulate exploration enthusiasm

and innovative spirit of scientists. With the progress

of technology and deepening of research,

gravitational detection will achieve a greater

breakthrough in the future. As a new means and tool

for exploring the universe, gravitational wave

detection provides an important way for us to uncover

secrets of the universe. It is believed that gravitational

wave detection will bring us more surprise and

discoveries with the continuous research.

The author’s motivation for writing this paper

mainly originated from a strong interest in exploring

cosmic science and curiosity about the unknown

world. The author believes that the detection of

gravitational wave can promote human progress and

it is an obvious evidence of the General Relativity.

The structure of this paper shows as follows. In the

second part, the author gives some descriptions about

gravitational wave. The third part is about some

principles and facilities aiming to detect the

gravitational wave. The content of forth part is the

state-of-art results. In the fifth part, the author

introduces some limitations and prospects about this

detection. The sixth part is the conclusion.

2 DESCRIPTIONS OF

GRAVITATIONAL WAVE

The gravitational wave was firstly mentioned in

General Relativity, and it is a type of time and space

ripples caused by some huge gravitational sources.

The gravitational wave propagates in the form of

waves, and the speed of it is the light speed.

Gravitational wave can be defined by this equation

(Yang, 2023):











= 𝑎













(1)

The generation of gravitational wave needs fast

changes of mass distribution, such as the rotation,

approaching or merging of binary star systems.

During these processes, violent movements and

changes in mass and energy generate gravitational

waves that propagate at the speed of light in a

vacuum. Gravitational wave barely interacts with

other matters in the universe, so it is challenging to

detect it. However, these slight fluctuations contain

some information of their sources, such as the mass,

energy and direction. This information is important to

scientists, because it can help us have a deeper

understand of the evolution of the universe, and they

can also offer the character of some massive objects

such as neutron stars and black holes. Information

about gravitational wave could even uncover the

secret of dark matter and dark energy.

Although detection of gravitational wave is a very

difficult task, scientists have made some progress

through persistent efforts and the design of

sophisticated instruments. These signals make us hear

the voice from deep universe. Gravitational wave is

not only the confirmation of General Relativity, but

also it brings the infinite possibility to do more

research and update technology. With the progress of

detective technology and new discovery of

gravitational wave, one can further reveal characters

of extreme objects. Scholars even want to use

gravitational wave for cosmic navigation, find new

energy sources or achieve a brand-new information

transmission mode.

3 PRINCIPLE AND FACILITY

FOR OBSERVATION

The principle and facility for observation of

gravitational wave dictation constitute a sophisticated

system. This system is designed to capture and study

the tiny space-time perturbations created by the

accelerating motion of massive objects in the universe.

Detailed introduction of principle and facility for

observation are discussed as following.

Gravitational wave can cause tiny transformation,

and this transformation can be detected by precise

equipment. The basic principle of gravitational wave

detection is influence on the two remote parts of the

detector. When gravitational waves pass by, the plane

perpendicular to them will be in a state of continuous

stretching and shrinking, that is, longitudinal

stretching when transverse contraction, and

longitudinal contraction when transverse stretching.

This kind of transformation will lead to tiny change

between these two parts of detector, and then the

detector sends signals to researchers. By measuring

this transformation, one can indirectly know

gravitational wave is here.

The most used detective facility is the Laser

Interferometric Gravitational-Wave Observatory

(LIGO). LIGO consists of two detectors located

thousands of kilometres apart, and each detector

contains two laser interferometers perpendicular to

each other. Laser beam is sent to two interferometers

and then reflected. When gravitational wave gets

through this detector, it will cause the phase of the

laser to change. One can determine the existence and

Analysis of the State-of-Art Observations for Gravitational Wave Searching

265

character of gravitational wave via this phase change.

To increase the sensitivity of detector, LIGO uses

highly stable optical and mechanical systems, and it

is in a place that keeps away from cities and other

man-made disturbance. LIGO also need numerous

data processing and analysis to extract real signal of

gravitational wave from the noise. LIGO-Virgo

reduces the distance and position of GW170817 to

40±8Mpc, which is approximately 30deg2 in the sky

(Collaboration and Aasi 2015; Acernese et al. 2015).

Except for the LIGO, there are some other

gravitational detectors under construction and

operation. The Laser Interferometer Space Antenna

(LISA) plans to use the Interferometer network

consisted of man-made satellites to conduct long-

distance detection. LISA's telescope research team

conducted index analysis and decomposition of the

telescope (Livas and Sankar, 2016; Sankar and Livas

2014; Livas and Sankar 2015). What is more, there

are still some gravitational wave detection methods

based on pulsar time difference and astronomical

observations are also being studied. These methods

are based on different principles and technologies,

and these methods detect the gravitational wave

indirectly by measuring the interaction between this

kind of wave and the substance.

In conclusion, the principle of gravitational wave

detection is measuring the effect of gravitational

waves on the space between two distant positions, and

using sophisticated detectors to capture this kind of

tiny changes.

4 STAET-OF-ART RESULTS

The most advanced gravitational wave detections are

reflected in multiple aspects, and these detections not

only deepen the understanding of cosmology, but

they also promote the rapid development of related

detection technologies. In the field of gravitational

wave detection, scientists have achieved

unprecedented precision and sensitivity. The Taiji

plan adopts laser interference method, which

establishes connections between satellites through

lasers. When the gravitational wave signals pass

through the detector, these signals will cause

temporal and spatial bending, thereby changing the

distance of the beam transmitted between the two

measurement points. By using a high-precision laser

interferometer to read out this distance change, the

inversion of gravitational wave signals can be

achieved (Luo, et al. 2020; Luo, et al. 2021). In the

aspects of accumulation and analysis of observational

data, there has been many gravitational wave

detection such as LIGO and Virgo, etc. These projects

have accumulated numerous observational data, and

via deep analysis into these data, scientists not only

have verified the prophecy of general relativity, but

multiple gravitational wave sources have been

discovered, which include extreme celestial

phenomena such as black holes or neutron star

mergers. These observational conclusions uncover

the most mythical and extreme cosmological

phenomena in the universe.

Table 1: Median values of the distributions of parameter estimation uncertainties for multiband BBHsa (Zhao et al. 2023).

GW detector ΔΩ

90%

LISA-Taiji 8.2×10

-1

1.1×10

-1

3.4×10

-6

5.5×10

-3

AMIGO 1.1×10

-1

7.5×10

-2

4.5×10

-7

4.7×10

-4

ET-CE 5.7×10

-3

1.8×10

-3

1.6×10

-3

2.5×10

-3

LT-AMIGO 5.4×10

-1

5.8×10

-2

1.5×10

-7

3.0×10

-4

LT-ET-CE 1.5×10

-1

1.3×10

-3

4.7×10

-8

1.5×10

-4

AMIGO-ET-CE 4.9×10

-4

1.1×10

-3

2.4×10

-7

7.9×10

-5

LT-AMIGO-ET-CE 4.6×10

-5

1.1×10

-3

2.9×10

-8

6.1×10

-5

Scientists have successfully captured multiple

important gravitational wave by using the most

advanced gravitational wave detector. The LIGO-

Virgo team observed a gravitational wave signal from

the merger of two black holes named GW190412.

This signal has extremely high scientific value, and it

shows the powerful abilities of gravitational wave

detector when it is measuring a complex

cosmological phenomenon. By analysing this signal,

scientists could measure some cosmological

characters of the black hole system, such as distance,

mass, distribution and rotating speed, etc. As can be

seen from the Table 1, the Space Gravitational Wave

Detector Network (LT AMIGO-ET-CE) of LISA,

Taiji, AMIGO, ET, and CE can improve parameter

estimation accuracy by two orders of magnitude

(Zhao et al. 2023).

With the continuous advancement of detection

technology and improvement of data processing

capabilities, scientists are gradually uncover the

mystery of gravitational wave universe. Future

projects of gravitational wave detection will more

IAMPA 2024 - International Conference on Innovations in Applied Mathematics, Physics and Astronomy

266

concentrate on the collaborative development of

multi band and multi messenger astronomy. By

combining data from different wave bands,

astrophysical processes in the universe will be

understanded more comprehensively, which will

offer a deeper and comprehensive cosmology for

humans, and will promote further development of

disciplines such as astronomy and physics.

To sum up, the most advanced consequences of

detection of gravitational wave are reflected in the

breakthroughs in detection technology, accumulation

and analysis of observative data and capture of

important gravitational wave signals, etc. These

consequences not only deepen understanding of

human, but they also offer valuable data and

theoretical support for scientific researches in the

future.

5 LIMITATIONS AND

PROSPECTS

In the journey of exploring the profound mysteries of

the universe, as a unique and powerful observation

method, gravitational waves have been attracting

endless exploration of scientists since the General

Relativity was proposed. However, the road of

detecting gravitational wave is not flat. Gravitational

wave, which is the tiniest fluctuation in the universe,

is difficult to be detected. The intensity of

gravitational waves is extremely low. Even the most

intense celestial events such as black hole collision or

neutron star merger occurring in the universe, the

gravitational wave signals that produced by these

events are almost negligible when they reach Earth.

The tiny characteristic make the detector of

gravitational wave must have extremely high

sensitivity and accuracy, with which the detector

could capture signals from the deep universe. What is

more, there are obvious limitations on underground

gravitational wave detection. Nowadays, ground-

based detectors such as the LIGO located in the

United States mainly rely on high-precision laser

interferometry technology to detect gravitational

waves. Limited by ground noise and experimental

scale, these detectors can only measure high

frequency gravitational signal, but these detectors

cannot touch the richer mid to low frequency range.

Gravitational waves in the mid to low frequency

range usually contain deeper and more meaningful

cosmological and physical principles, but these waves

are difficult to be captured by existing technology.

The interaction between gravitational waves and

matters is so tiny that gravitational waves can

penetrate almost any substance without loss, but this

character makes the detection of gravitational wave

more difficult. To solve these problems, scientists

must improve the accuracy and sensitivity of

detectors. In the Taiji Plan, The Institute of

Mechanics of the Chinese Academy of Sciences and

other core participating units have made major

breakthroughs in pico laser interferometry

technology, high-precision weak force measurement

technology and other aspects, built a nano radian laser

capture and tracking integrated ground simulation

system, and developed the first photoviscous

interferometer prototype in China (Luo, et al. 2020;

Luo, et al. 2021). Detection of gravitational wave will

uncover more secretes from the universe. Extreme

celestial bodies such as black holes and neutron stars

are important resources of gravitational wave. By

detecting gravitational wave signals generated by

these celestial bodies, scientists can gain a deeper

understanding of the internal structure and motion

patterns of these celestial bodies, thereby revealing

the most fundamental physical laws in the universe.

The development of gravitational wave detection

technology will drive common progress in relative

field. The application of laser interferometry

technology, high-precision measurement technology,

etc. in gravitational wave dictation, not only promotes

development of these technologies themselves, but it

also offers vital technology support and reference for

other scientific fields. This interdisciplinary

integration and interaction will inject new vitality into

scientific research and technological development

6 CONCLUSIONS

The gradual promotion of gravitational wave

detection means that human understanding the deep

structure of the universe reached an unprecedented

level. From the theoretical argumentation to

experimental verification, this process not only shows

the hardship and glory in scientific exploration, but

also it shows the power of interdisciplinary

collaboration and technological innovation.

With the application of advanced detection

technologies such as high precision laser

interferometer and pulsar timing array (PTA),

scientists successfully captured gravitational wave

signals from the deep universe. These signals carry

valuable information about the merger of dense

binary systems, and uncover some important events

in the early universe. In terms of detection

Analysis of the State-of-Art Observations for Gravitational Wave Searching

267

technology, laser interferometry plays a crucial role

in gravitational detection due to its extremely high

sensitivity and accuracy. The successful operation of

detectors such as the LIGO confirmed the existence

of gravitational wave, and it also offered scientists

some new ways to do some research on extreme

astrophysical phenomena. As an emerging detection

method, the PTA makes scientists detect the

persistent gravitational wave background in the

universe because this method has a unique ultralow

frequency detection capability, which further

broadens the perspective of gravitational wave

research.

The success of gravitational detection is not only

an important confirmation to the General Relativity,

but this success also brings new chances and

challenges for cosmology and physics. Gravitational

wave detection makes scientists explore the mysteries

of the universe in an unprecedented way, uncover

physical characters of extreme celestial bodies such

as black holes and neutron stars, and find the

evolution process in the early universe. As a unique

information carrier in the universe, its propagation

characteristics enable us to penetrate the obstruction

of interstellar media to obtain information which

cannot be transferred by electromagnetic waves.

These characteristics offer new perspective and tools

to cosmological researches. With the promotion of

detection technologies, a brand new age of astronomy

will be opened up. More advanced detectors will

detect weaker and father gravitational wave signals,

and these detectors will uncover more secretes about

the universe. These detections will promote the deep

researches in basic physics, the understanding of the

structure of spacetime, the essence of gravity, and

other related issues.

In conclusion, the development and application in

technology of gravitational wave detection is the

crystallization of human wisdom and innovative

spirit. The detection not only reveals deep secretes of

the universe for us, but it also injects new vitality and

motivation to cosmology and physics.

REFERENCES

Acernese, F., Agathos, M., Agatsuma, K., et al. 2014.

Advanced Virgo: a second-generation interferometric

gravitational wave detector. Classical and Quantum

Gravity, 32(2), 024001.

Collaboration, T. and Aasi, J. 2015. Advanced LIGO. Class.

Quantum Gravity, 32(7), 074001.

Hammesfahr, A. 2001. LISA mission study overview. Class

Quantum Grav, 18(19), 4045−4051.

Jennrich, O. 2009. LISA technology and instrumentation.

Class Quantum Grav, 26(15), 153001.

Livas, J. and Sankar, S. 2015. Optical telescope design

study results. Phys Conf Ser, 610, 012029.

Livas, J. and Sankar, S. 2016 Optical telescope system-level

design considerations for a space-based gravitational

wave mission. Proc SPIE, 9904, 99041K.

Luo, J., Chen, L., Duan, H., et al. 2016. TianQin: a space-

borne gravitational wave detector. Class Quantum

Grav, 33(3), 035010.

Luo, Z., Guo, Z., Jin, G., et al. 2020. A brief analysis to

Taiji: science. Results Phys, 16, 102918.

Luo, Z., Wang, Y., Wu, Y., et al. 2021. The Taiji program:

a concise overview. Prog Theor Exp Phys, 2021(5),

05A108.

Martens, W. and Joffre, E. 2021. Trajectory design for the

ESA LISA mission. The Journal of the Astronautical

Sciences, 68(2), 402-443.

Sankar, S. and Livas, J. 2014. Optical telescope design for

a space based gravitational-wave mission. Proc SPIE,

9143, 14.

Weber, J. 1960. Detection and generation of gravitational

waves. Physical Review, 117(1), 306.

Yang, S. 2023. The Interface Connection Problem of Wave

Equations. University Physics, 42(11), 1-4.

Zhao, Y., Lu, Y., Yan, C., et al. 2023 Multiband

gravitational wave observations of stellar binary black

holes at the low to middle and high frequencies. Mon

Not Roy Astron Soc, 522, 2951–2966.

IAMPA 2024 - International Conference on Innovations in Applied Mathematics, Physics and Astronomy

268