-
NASA | Using Quasars to Measure the Earth: A Brief History of VLBI
VLBI, or Very Long Baseline Interferometry, is a technique that uses multiple radio telescopes to very precisely measure the Earth's orientation. It was originally invented back in the 1960s to take better pictures of quasars, but scientists soon found out that if you threw the process in reverse, you could measure how the ground beneath the telescopes moves around, how long days really are, and how the Earth wobbles on its axis as it revolves around the sun! Learn more about VLBI here!
For more information about NASA's Space Geodesy Project, visit http://space-geodesy.nasa.gov!
This video is presented in both stereoscopic 3D and standard 2D versions.
This video is public domain and can be downloaded at: http://svs.gsfc.nasa.gov/goto?10964
Like our videos? Subscribe to NASA's Goddard S...
published: 21 Jun 2012
-
ALMA explained: very long baseline interferometry (VLBI)
This video is part of the ALMA explained series created by European ARC network and discusses very long baseline interferometry (VLBI)
published: 17 Nov 2021
-
Using Quasars to Make Measurements On Earth | NASA VLBI Interferometry Telescope Radio HD
Visit my website at http://www.junglejoel.com - VLBI (Very Long Baseline Interferometry) can be used to measure movements of and on the Earth. Please rate and comment, thanks!
Credit: NASA GSC
published: 21 Jun 2012
-
Using VLBI to create an Image of the black hole in the center of our Galaxy
This video shows the global net of telescopes in the EHT collaboration.
With a process called Very Long Baseline Interferometry they can be combined into a huge, single telescope the size of the earth.
This enables scientists to observe the black hole in the center of for example our galaxy, which is comparable to photographing an apple on the surface of the moon.
As the single telescopes move with the rotation of the earth more and more information about the observed object is gained.
After 24 hours the shadow of the black hole as well as the bright ring of plasma (see ) can clearly be seen.
Link to our homepage: https://relastro.uni-frankfurt.de/
Link to our gallery: https://relastro.uni-frankfurt.de/gallery/
Link to the EHT website: https://eventhorizontelescope.org/
Link to the Bl...
published: 10 Apr 2019
-
Positions of the telescopes used in the 1.3 mm VLBI observations of the quasar 3C 279
Astronomers connected the Atacama Pathfinder Experiment (APEX), in Chile, to the Submillimeter Array (SMA) in Hawaii, USA, and the Submillimeter Telescope (SMT) in Arizona, USA for the first time, to make the sharpest observation ever of the centre of a distant galaxy, the bright quasar 3C 279. The telescopes were linked using a technique known as Very Long Baseline Interferometry (VLBI). Larger telescopes can make sharper observations, and interferometry allows multiple telescopes to act like a single telescope as large as the separation — or "baseline" — between them. The baseline length from Chile (APEX) to Hawaii (SMA) is 9447 km, from Chile to Arizona (SMT) 7174 km, and from Arizona to Hawaii 4627 km.
Credit:
ESO/L. Calçada
More information:
http://www.eso.org/public/videos/eso1229...
published: 19 Jul 2012
-
Measuring Earth's Orientation with Very Long Baseline Interferometry
David Boboltz of the US Naval Observatory talks about how radio telescopes are used to measure climate change indicators and the shifting of Earth's crustal plates.
Discover more about Our Milky Way Galaxy on our website:
https://public.nrao.edu/radio-astronomy/our-milky-way-galaxy/
Take a virtual tour of the Milky Way Galaxy and its neighbors with NRAO's Milky Way Explorer!
https://public.nrao.edu/explore/milky-way-explorer/
Additional animation and video credits: J. Hellerman and A. Angelich; NRAO/AUI/NSF; Neil Stratford - The Earth's Tilt Motion Graphic http://www.neilstratford.ca/; NASA Earth Observatory image by Robert Simmon, using Suomi NPP VIIRS data provided courtesy of Chris Elvidge (NOAA National Geophysical Data Center). Suomi NPP is the result of a partnership between NAS...
published: 01 Dec 2020
-
[핫클립] VLBI 관측을 할 수 있는 한국우주전파관측망 / YTN 사이언스
한국천문연구원은 전파망원경을 효율적으로
활용하기 위한 연구분야를 개척했다.
깊고 머나먼 우주를 보기 위해 구축한 한국우주전파관측망 KVN
여러 대의 전파망원경을 하나로 연결해 가상의 큰 망원경을
구축해 높은 분해능을 얻는 VLBI 관측을 할 수 있다.
21m 전파망원경을 서울, 울산, 제주에 설치해 볼 수 있다.
========================================
※ Full 영상 ▶ https://youtu.be/QipsmCm3ebw
※ YTN사이언스 구독하기 ▶ https://bit.ly/3raTL0t
========================================
#VLBI 관측 #한국우주전파관측망 #KVN #우주 #전파망원경
VLBI 관측을 할 수 있는 한국우주전파관측망 / YTN 사이언스
[YTN 사이언스 기사원문] https://science.ytn.co.kr/program/view_hotclip.php?mcd=1394&key=202212091700416018
[프로그램 제작 문의] [email protected]
published: 28 Dec 2022
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How to image black holes? VLBI and radio interferometry explained!
In this video, I explain the Very Long Baseline Interferometry(VLBI) technique which is used by the Event Horizon Telescope (EHT) to image the shadow of the black hole M87* and SAG A*. I also explain the basics of radio astronomy and talk about telescopes to help understand the topic well.
In July 2022 my research group and I visited #MIT's Haystack Observatory to discuss our balloon-borne project. Had this fantastic experience of not only meeting some of the most amazing and smart people but also learning a lot about astronomy, instrumentation, and science in general!
Let me know if you have any doubts about whatever you see. See you guys soon!
Timestamps :
0:00 Intro
1:59 EM Spectrum
4:37 What are radio telescope
6:30 Imaging a Black Hole: VLBI
13:44 Outro
published: 29 Oct 2022
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Computational Imaging for VLBI Image Reconstruction
This video is about Computational Imaging for VLBI Image Reconstruction
published: 02 Sep 2016
-
Very Long Baseline Interferometry -Geodesist Chopo Ma explains some of the geodetic uses of VLBI.
Very-long-baseline interferometry (VLBI) is a type of astronomical interferometry used in radio astronomy. In VLBI a signal from an astronomical radio source, such as a quasar, is collected at multiple radio telescopes on Earth. The distance between the radio telescopes is then calculated using the time difference between the arrivals of the radio signal at different telescopes. This allows observations of an object that are made simultaneously by many radio telescopes to be combined, emulating a telescope with a size equal to the maximum separation between the telescopes.
Data received at each antenna in the array include arrival times from a local atomic clock, such as a hydrogen maser. At a later time, the data are correlated with data from other antennas that recorded the same radio s...
published: 07 May 2015
1:52
NASA | Using Quasars to Measure the Earth: A Brief History of VLBI
VLBI, or Very Long Baseline Interferometry, is a technique that uses multiple radio telescopes to very precisely measure the Earth's orientation. It was origina...
VLBI, or Very Long Baseline Interferometry, is a technique that uses multiple radio telescopes to very precisely measure the Earth's orientation. It was originally invented back in the 1960s to take better pictures of quasars, but scientists soon found out that if you threw the process in reverse, you could measure how the ground beneath the telescopes moves around, how long days really are, and how the Earth wobbles on its axis as it revolves around the sun! Learn more about VLBI here!
For more information about NASA's Space Geodesy Project, visit http://space-geodesy.nasa.gov!
This video is presented in both stereoscopic 3D and standard 2D versions.
This video is public domain and can be downloaded at: http://svs.gsfc.nasa.gov/goto?10964
Like our videos? Subscribe to NASA's Goddard Shorts HD podcast:
http://svs.gsfc.nasa.gov/vis/iTunes/f0004_index.html
Or find NASA Goddard Space Flight Center on Facebook:
http://www.facebook.com/NASA.GSFC
Or find us on Twitter:
http://twitter.com/NASAGoddard
https://wn.com/Nasa_|_Using_Quasars_To_Measure_The_Earth_A_Brief_History_Of_Vlbi
VLBI, or Very Long Baseline Interferometry, is a technique that uses multiple radio telescopes to very precisely measure the Earth's orientation. It was originally invented back in the 1960s to take better pictures of quasars, but scientists soon found out that if you threw the process in reverse, you could measure how the ground beneath the telescopes moves around, how long days really are, and how the Earth wobbles on its axis as it revolves around the sun! Learn more about VLBI here!
For more information about NASA's Space Geodesy Project, visit http://space-geodesy.nasa.gov!
This video is presented in both stereoscopic 3D and standard 2D versions.
This video is public domain and can be downloaded at: http://svs.gsfc.nasa.gov/goto?10964
Like our videos? Subscribe to NASA's Goddard Shorts HD podcast:
http://svs.gsfc.nasa.gov/vis/iTunes/f0004_index.html
Or find NASA Goddard Space Flight Center on Facebook:
http://www.facebook.com/NASA.GSFC
Or find us on Twitter:
http://twitter.com/NASAGoddard
- published: 21 Jun 2012
- views: 75863
3:23
ALMA explained: very long baseline interferometry (VLBI)
This video is part of the ALMA explained series created by European ARC network and discusses very long baseline interferometry (VLBI)
This video is part of the ALMA explained series created by European ARC network and discusses very long baseline interferometry (VLBI)
https://wn.com/Alma_Explained_Very_Long_Baseline_Interferometry_(Vlbi)
This video is part of the ALMA explained series created by European ARC network and discusses very long baseline interferometry (VLBI)
- published: 17 Nov 2021
- views: 2203
1:52
Using Quasars to Make Measurements On Earth | NASA VLBI Interferometry Telescope Radio HD
Visit my website at http://www.junglejoel.com - VLBI (Very Long Baseline Interferometry) can be used to measure movements of and on the Earth. Please rate and c...
Visit my website at http://www.junglejoel.com - VLBI (Very Long Baseline Interferometry) can be used to measure movements of and on the Earth. Please rate and comment, thanks!
Credit: NASA GSC
https://wn.com/Using_Quasars_To_Make_Measurements_On_Earth_|_Nasa_Vlbi_Interferometry_Telescope_Radio_Hd
Visit my website at http://www.junglejoel.com - VLBI (Very Long Baseline Interferometry) can be used to measure movements of and on the Earth. Please rate and comment, thanks!
Credit: NASA GSC
- published: 21 Jun 2012
- views: 2714
0:27
Using VLBI to create an Image of the black hole in the center of our Galaxy
This video shows the global net of telescopes in the EHT collaboration.
With a process called Very Long Baseline Interferometry they can be combined into a huge...
This video shows the global net of telescopes in the EHT collaboration.
With a process called Very Long Baseline Interferometry they can be combined into a huge, single telescope the size of the earth.
This enables scientists to observe the black hole in the center of for example our galaxy, which is comparable to photographing an apple on the surface of the moon.
As the single telescopes move with the rotation of the earth more and more information about the observed object is gained.
After 24 hours the shadow of the black hole as well as the bright ring of plasma (see ) can clearly be seen.
Link to our homepage: https://relastro.uni-frankfurt.de/
Link to our gallery: https://relastro.uni-frankfurt.de/gallery/
Link to the EHT website: https://eventhorizontelescope.org/
Link to the Black Hole Cam Website: https://blackholecam.org/
https://wn.com/Using_Vlbi_To_Create_An_Image_Of_The_Black_Hole_In_The_Center_Of_Our_Galaxy
This video shows the global net of telescopes in the EHT collaboration.
With a process called Very Long Baseline Interferometry they can be combined into a huge, single telescope the size of the earth.
This enables scientists to observe the black hole in the center of for example our galaxy, which is comparable to photographing an apple on the surface of the moon.
As the single telescopes move with the rotation of the earth more and more information about the observed object is gained.
After 24 hours the shadow of the black hole as well as the bright ring of plasma (see ) can clearly be seen.
Link to our homepage: https://relastro.uni-frankfurt.de/
Link to our gallery: https://relastro.uni-frankfurt.de/gallery/
Link to the EHT website: https://eventhorizontelescope.org/
Link to the Black Hole Cam Website: https://blackholecam.org/
- published: 10 Apr 2019
- views: 13855
0:37
Positions of the telescopes used in the 1.3 mm VLBI observations of the quasar 3C 279
Astronomers connected the Atacama Pathfinder Experiment (APEX), in Chile, to the Submillimeter Array (SMA) in Hawaii, USA, and the Submillimeter Telescope (SMT)...
Astronomers connected the Atacama Pathfinder Experiment (APEX), in Chile, to the Submillimeter Array (SMA) in Hawaii, USA, and the Submillimeter Telescope (SMT) in Arizona, USA for the first time, to make the sharpest observation ever of the centre of a distant galaxy, the bright quasar 3C 279. The telescopes were linked using a technique known as Very Long Baseline Interferometry (VLBI). Larger telescopes can make sharper observations, and interferometry allows multiple telescopes to act like a single telescope as large as the separation — or "baseline" — between them. The baseline length from Chile (APEX) to Hawaii (SMA) is 9447 km, from Chile to Arizona (SMT) 7174 km, and from Arizona to Hawaii 4627 km.
Credit:
ESO/L. Calçada
More information:
http://www.eso.org/public/videos/eso1229b/
https://wn.com/Positions_Of_The_Telescopes_Used_In_The_1.3_Mm_Vlbi_Observations_Of_The_Quasar_3C_279
Astronomers connected the Atacama Pathfinder Experiment (APEX), in Chile, to the Submillimeter Array (SMA) in Hawaii, USA, and the Submillimeter Telescope (SMT) in Arizona, USA for the first time, to make the sharpest observation ever of the centre of a distant galaxy, the bright quasar 3C 279. The telescopes were linked using a technique known as Very Long Baseline Interferometry (VLBI). Larger telescopes can make sharper observations, and interferometry allows multiple telescopes to act like a single telescope as large as the separation — or "baseline" — between them. The baseline length from Chile (APEX) to Hawaii (SMA) is 9447 km, from Chile to Arizona (SMT) 7174 km, and from Arizona to Hawaii 4627 km.
Credit:
ESO/L. Calçada
More information:
http://www.eso.org/public/videos/eso1229b/
- published: 19 Jul 2012
- views: 2455
2:39
Measuring Earth's Orientation with Very Long Baseline Interferometry
David Boboltz of the US Naval Observatory talks about how radio telescopes are used to measure climate change indicators and the shifting of Earth's crustal pla...
David Boboltz of the US Naval Observatory talks about how radio telescopes are used to measure climate change indicators and the shifting of Earth's crustal plates.
Discover more about Our Milky Way Galaxy on our website:
https://public.nrao.edu/radio-astronomy/our-milky-way-galaxy/
Take a virtual tour of the Milky Way Galaxy and its neighbors with NRAO's Milky Way Explorer!
https://public.nrao.edu/explore/milky-way-explorer/
Additional animation and video credits: J. Hellerman and A. Angelich; NRAO/AUI/NSF; Neil Stratford - The Earth's Tilt Motion Graphic http://www.neilstratford.ca/; NASA Earth Observatory image by Robert Simmon, using Suomi NPP VIIRS data provided courtesy of Chris Elvidge (NOAA National Geophysical Data Center). Suomi NPP is the result of a partnership between NASA, NOAA, and the Department of Defense; NASA Goddard Space Flight Center Image by Reto Stockli (land surface, shallow water, clouds). Enhancements by Robert Simmon (ocean color, compositing, 3D globes, animation): NASA/Goddard Space Flight Center; Google Earth; USGS.
Music: Geodesium
https://wn.com/Measuring_Earth's_Orientation_With_Very_Long_Baseline_Interferometry
David Boboltz of the US Naval Observatory talks about how radio telescopes are used to measure climate change indicators and the shifting of Earth's crustal plates.
Discover more about Our Milky Way Galaxy on our website:
https://public.nrao.edu/radio-astronomy/our-milky-way-galaxy/
Take a virtual tour of the Milky Way Galaxy and its neighbors with NRAO's Milky Way Explorer!
https://public.nrao.edu/explore/milky-way-explorer/
Additional animation and video credits: J. Hellerman and A. Angelich; NRAO/AUI/NSF; Neil Stratford - The Earth's Tilt Motion Graphic http://www.neilstratford.ca/; NASA Earth Observatory image by Robert Simmon, using Suomi NPP VIIRS data provided courtesy of Chris Elvidge (NOAA National Geophysical Data Center). Suomi NPP is the result of a partnership between NASA, NOAA, and the Department of Defense; NASA Goddard Space Flight Center Image by Reto Stockli (land surface, shallow water, clouds). Enhancements by Robert Simmon (ocean color, compositing, 3D globes, animation): NASA/Goddard Space Flight Center; Google Earth; USGS.
Music: Geodesium
- published: 01 Dec 2020
- views: 1900
2:24
[핫클립] VLBI 관측을 할 수 있는 한국우주전파관측망 / YTN 사이언스
한국천문연구원은 전파망원경을 효율적으로
활용하기 위한 연구분야를 개척했다.
깊고 머나먼 우주를 보기 위해 구축한 한국우주전파관측망 KVN
여러 대의 전파망원경을 하나로 연결해 가상의 큰 망원경을
구축해 높은 분해능을 얻는 VLBI 관측을 할 수 있다.
21m 전파망원경을 서울, 울산, ...
한국천문연구원은 전파망원경을 효율적으로
활용하기 위한 연구분야를 개척했다.
깊고 머나먼 우주를 보기 위해 구축한 한국우주전파관측망 KVN
여러 대의 전파망원경을 하나로 연결해 가상의 큰 망원경을
구축해 높은 분해능을 얻는 VLBI 관측을 할 수 있다.
21m 전파망원경을 서울, 울산, 제주에 설치해 볼 수 있다.
========================================
※ Full 영상 ▶ https://youtu.be/QipsmCm3ebw
※ YTN사이언스 구독하기 ▶ https://bit.ly/3raTL0t
========================================
#VLBI 관측 #한국우주전파관측망 #KVN #우주 #전파망원경
VLBI 관측을 할 수 있는 한국우주전파관측망 / YTN 사이언스
[YTN 사이언스 기사원문] https://science.ytn.co.kr/program/view_hotclip.php?mcd=1394&key=202212091700416018
[프로그램 제작 문의]
[email protected]
https://wn.com/핫클립_Vlbi_관측을_할_수_있는_한국우주전파관측망_Ytn_사이언스
한국천문연구원은 전파망원경을 효율적으로
활용하기 위한 연구분야를 개척했다.
깊고 머나먼 우주를 보기 위해 구축한 한국우주전파관측망 KVN
여러 대의 전파망원경을 하나로 연결해 가상의 큰 망원경을
구축해 높은 분해능을 얻는 VLBI 관측을 할 수 있다.
21m 전파망원경을 서울, 울산, 제주에 설치해 볼 수 있다.
========================================
※ Full 영상 ▶ https://youtu.be/QipsmCm3ebw
※ YTN사이언스 구독하기 ▶ https://bit.ly/3raTL0t
========================================
#VLBI 관측 #한국우주전파관측망 #KVN #우주 #전파망원경
VLBI 관측을 할 수 있는 한국우주전파관측망 / YTN 사이언스
[YTN 사이언스 기사원문] https://science.ytn.co.kr/program/view_hotclip.php?mcd=1394&key=202212091700416018
[프로그램 제작 문의]
[email protected]
- published: 28 Dec 2022
- views: 1070
14:42
How to image black holes? VLBI and radio interferometry explained!
In this video, I explain the Very Long Baseline Interferometry(VLBI) technique which is used by the Event Horizon Telescope (EHT) to image the shadow of the bla...
In this video, I explain the Very Long Baseline Interferometry(VLBI) technique which is used by the Event Horizon Telescope (EHT) to image the shadow of the black hole M87* and SAG A*. I also explain the basics of radio astronomy and talk about telescopes to help understand the topic well.
In July 2022 my research group and I visited #MIT's Haystack Observatory to discuss our balloon-borne project. Had this fantastic experience of not only meeting some of the most amazing and smart people but also learning a lot about astronomy, instrumentation, and science in general!
Let me know if you have any doubts about whatever you see. See you guys soon!
Timestamps :
0:00 Intro
1:59 EM Spectrum
4:37 What are radio telescope
6:30 Imaging a Black Hole: VLBI
13:44 Outro
https://wn.com/How_To_Image_Black_Holes_Vlbi_And_Radio_Interferometry_Explained
In this video, I explain the Very Long Baseline Interferometry(VLBI) technique which is used by the Event Horizon Telescope (EHT) to image the shadow of the black hole M87* and SAG A*. I also explain the basics of radio astronomy and talk about telescopes to help understand the topic well.
In July 2022 my research group and I visited #MIT's Haystack Observatory to discuss our balloon-borne project. Had this fantastic experience of not only meeting some of the most amazing and smart people but also learning a lot about astronomy, instrumentation, and science in general!
Let me know if you have any doubts about whatever you see. See you guys soon!
Timestamps :
0:00 Intro
1:59 EM Spectrum
4:37 What are radio telescope
6:30 Imaging a Black Hole: VLBI
13:44 Outro
- published: 29 Oct 2022
- views: 968
12:22
Computational Imaging for VLBI Image Reconstruction
This video is about Computational Imaging for VLBI Image Reconstruction
This video is about Computational Imaging for VLBI Image Reconstruction
https://wn.com/Computational_Imaging_For_Vlbi_Image_Reconstruction
This video is about Computational Imaging for VLBI Image Reconstruction
- published: 02 Sep 2016
- views: 3906
1:46
Very Long Baseline Interferometry -Geodesist Chopo Ma explains some of the geodetic uses of VLBI.
Very-long-baseline interferometry (VLBI) is a type of astronomical interferometry used in radio astronomy. In VLBI a signal from an astronomical radio source, s...
Very-long-baseline interferometry (VLBI) is a type of astronomical interferometry used in radio astronomy. In VLBI a signal from an astronomical radio source, such as a quasar, is collected at multiple radio telescopes on Earth. The distance between the radio telescopes is then calculated using the time difference between the arrivals of the radio signal at different telescopes. This allows observations of an object that are made simultaneously by many radio telescopes to be combined, emulating a telescope with a size equal to the maximum separation between the telescopes.
Data received at each antenna in the array include arrival times from a local atomic clock, such as a hydrogen maser. At a later time, the data are correlated with data from other antennas that recorded the same radio signal, to produce the resulting image. The resolution achievable using interferometry is proportional to the observing frequency. The VLBI technique enables the distance between telescopes to be much greater than that possible with conventional interferometry, which requires antennas to be physically connected by coaxial cable, waveguide, optical fiber, or other type of transmission line. The greater telescope separations are possible in VLBI due to the development of the closure phase imaging technique by Roger Jennison in the 1950s, allowing VLBI to produce images with superior resolution.
VLBI is most well known for imaging distant cosmic radio sources, spacecraft tracking, and for applications in astrometry. However, since the VLBI technique measures the time differences between the arrival of radio waves at separate antennas, it can also be used "in reverse" to perform earth rotation studies, map movements of tectonic plates very precisely (within millimetres), and perform other types of geodesy. Using VLBI in this manner requires large numbers of time difference measurements from distant sources (such as quasars) observed with a global network of antennas over a period of time.
See:
http://en.wikipedia.org/wiki/Very-long-baseline_interferometry
https://wn.com/Very_Long_Baseline_Interferometry_Geodesist_Chopo_Ma_Explains_Some_Of_The_Geodetic_Uses_Of_Vlbi.
Very-long-baseline interferometry (VLBI) is a type of astronomical interferometry used in radio astronomy. In VLBI a signal from an astronomical radio source, such as a quasar, is collected at multiple radio telescopes on Earth. The distance between the radio telescopes is then calculated using the time difference between the arrivals of the radio signal at different telescopes. This allows observations of an object that are made simultaneously by many radio telescopes to be combined, emulating a telescope with a size equal to the maximum separation between the telescopes.
Data received at each antenna in the array include arrival times from a local atomic clock, such as a hydrogen maser. At a later time, the data are correlated with data from other antennas that recorded the same radio signal, to produce the resulting image. The resolution achievable using interferometry is proportional to the observing frequency. The VLBI technique enables the distance between telescopes to be much greater than that possible with conventional interferometry, which requires antennas to be physically connected by coaxial cable, waveguide, optical fiber, or other type of transmission line. The greater telescope separations are possible in VLBI due to the development of the closure phase imaging technique by Roger Jennison in the 1950s, allowing VLBI to produce images with superior resolution.
VLBI is most well known for imaging distant cosmic radio sources, spacecraft tracking, and for applications in astrometry. However, since the VLBI technique measures the time differences between the arrival of radio waves at separate antennas, it can also be used "in reverse" to perform earth rotation studies, map movements of tectonic plates very precisely (within millimetres), and perform other types of geodesy. Using VLBI in this manner requires large numbers of time difference measurements from distant sources (such as quasars) observed with a global network of antennas over a period of time.
See:
http://en.wikipedia.org/wiki/Very-long-baseline_interferometry
- published: 07 May 2015
- views: 2138