The Laser Interferometer Gravitational-Wave Observatory (LIGO) is a joint project between Caltech and MIT, supported by the National Science Foundation. It operates three interferometers at two sites in the United States, designed to detect gravitational waves (GWs) from astrophysical sources. LIGO's goal is to detect and study GWs, which are ripples in spacetime caused by massive accelerating objects. These waves can provide insights into general relativity, exotic objects like black holes and neutron stars, and new astrophysical phenomena. LIGO uses Michelson interferometers, which are highly sensitive to changes in arm length caused by GWs. The interferometers are designed to detect GWs in the frequency range of 40–7000 Hz, with a sensitivity of $10^{-21}$ strain. The detectors are located at Hanford and Livingston, with arms of 4 km and 2 km, respectively. They are sensitive to GW strains smaller than one part in $10^{21}$, allowing for the detection of very weak signals. The interferometers use advanced techniques such as Fabry-Perot cavities and power recycling to enhance sensitivity. They also employ vibration isolation and active feedback systems to maintain stability and suppress noise. The detectors are sensitive to a variety of GW sources, including binary neutron stars, binary black holes, and supernovae. LIGO's data are analyzed by the LIGO Scientific Collaboration, which includes researchers from various institutions. The collaboration has developed a global network of GW detectors, including Virgo and TAMA, to improve detection capabilities and source localization. The interferometers are calibrated using laser wavelength measurements and injected sine waves to ensure accuracy. The response of LIGO to GWs is characterized by a single-pole transfer function, with a pole frequency related to the storage time. The interferometers are sensitive to GWs propagating orthogonally to the plane of the arms, with linear polarization along the arms. Other angles and polarizations result in reduced sensitivity. LIGO's detectors are crucial for opening a new window on the universe, offering insights into strong-field gravity and astrophysical phenomena.The Laser Interferometer Gravitational-Wave Observatory (LIGO) is a joint project between Caltech and MIT, supported by the National Science Foundation. It operates three interferometers at two sites in the United States, designed to detect gravitational waves (GWs) from astrophysical sources. LIGO's goal is to detect and study GWs, which are ripples in spacetime caused by massive accelerating objects. These waves can provide insights into general relativity, exotic objects like black holes and neutron stars, and new astrophysical phenomena. LIGO uses Michelson interferometers, which are highly sensitive to changes in arm length caused by GWs. The interferometers are designed to detect GWs in the frequency range of 40–7000 Hz, with a sensitivity of $10^{-21}$ strain. The detectors are located at Hanford and Livingston, with arms of 4 km and 2 km, respectively. They are sensitive to GW strains smaller than one part in $10^{21}$, allowing for the detection of very weak signals. The interferometers use advanced techniques such as Fabry-Perot cavities and power recycling to enhance sensitivity. They also employ vibration isolation and active feedback systems to maintain stability and suppress noise. The detectors are sensitive to a variety of GW sources, including binary neutron stars, binary black holes, and supernovae. LIGO's data are analyzed by the LIGO Scientific Collaboration, which includes researchers from various institutions. The collaboration has developed a global network of GW detectors, including Virgo and TAMA, to improve detection capabilities and source localization. The interferometers are calibrated using laser wavelength measurements and injected sine waves to ensure accuracy. The response of LIGO to GWs is characterized by a single-pole transfer function, with a pole frequency related to the storage time. The interferometers are sensitive to GWs propagating orthogonally to the plane of the arms, with linear polarization along the arms. Other angles and polarizations result in reduced sensitivity. LIGO's detectors are crucial for opening a new window on the universe, offering insights into strong-field gravity and astrophysical phenomena.