Today in History: LIGO's discovery across 1.3 billion light years
1.3 billion years ago,
Deep in the distant Milky Way,
The collision of two black holes releases a kind of energy.
They are called "gravitational waves".
More than 100 years ago,
Einstein proposed the existence of gravitational waves in the universe.
However, he believes that detecting gravitational waves is almost impossible.
Three years ago, LIGO detected gravitational waves.
The New York Times calls the sound of gravitational waves
Destined to become one of the greatest voices in science.
Extremely tiny
Gravitational waves
The luminosity distance of the gravitational wave source is about 410 Mpc, which is 1.3 billion light years away. However, the diameter of the Milky Way is only 100,000 light years, and the distance to the Andromeda Galaxy is only 2.5 million light years.
1.3 billion years ago, when only blue algae were working hard to produce oxygen on Earth, preparing for the reproduction of life in the long years ahead, two black holes collided and merged. The "ripples" caused by this collision swept across countless galaxies, gases, dust, stars, etc. across 1.3 billion light years, sweeping across the Earth, causing a tiny change equivalent to one ten-thousandth of the diameter of a proton. Although this change is extremely small, it was still detected by intelligent humans.
The tool for detecting super tiny gravitational waves is called "LIGO". As you can imagine, its accuracy is very high.
The highest accuracy
Detection Instrument
LIGO, Laser Interferometer Gravitational-Wave Observatory, means Laser Interferometer Gravitational-Wave Observatory in Chinese. The LIGO system has two jointly operated devices, one in Hanford, Washington, and the other in Livingston, Louisiana. Since gravitational waves do not leave clues on the electromagnetic spectrum and cannot be seen, the main goal of LIGO is to "listen" to the sound of the universe and obtain evidence of the existence of gravitational waves.
Image source: Internet
Image source: Internet
Image source: Internet
Each LIGO device emits a laser in an ultra-high vacuum chamber, splits the laser in half, and sends the two beams down two perpendicular 2.5-mile-long laser arms, which are then reflected back by mirrors at the ends of the arms.
Image source: Internet
Image source: Internet
When a gravitational wave passes, spacetime in this region changes, causing a tiny relative motion between the two laser arms, a tiny change on the order of one ten-thousandth of a proton's diameter. This changes the relative phase of the returning light that enters the receiving optical system, releasing the light to the optical sensor, creating a measurable signal or noise.
Image source: Internet
LIGO's equipment is the most sophisticated instrument in human history. For example, if you gather all the sand from all the beaches on Earth and measure it with LIGO, if a grain of sand moves, LIGO will be able to detect it. This is LIGO, which has achieved such incredible precision that when it directly detected gravitational waves, human understanding of the universe also entered a new stage.
LINK,
ADI Inside！
Scott Wurcer is a design expert in the field of precision amplifiers at ADI. The chips he designs are used in precision products in various industries. Wurcer once said that the customer product he is most proud of is a scientific research project - LIGO.
LIGO uses a large number of ADI's integrated technologies. These technologies all reflect ADI's commitment to precision technology - meeting the current requirements for precision indicators and promoting innovation in the field of precision engineering and the realization of key applications in the future.
In addition to predicting and compensating for all other possible sources of environmental noise, LIGO also requires that their laser amplitude must remain ultra-stable, with amplitude variations no greater than 2x10-9 at about 100 Hz carrier displacement . This is impossible to do directly with the laser, and the LIGO team needs to use a + feedback system to measure the light output and control the amplitude. This requires an ultra-low noise amplifier with specific performance. The LIGO scientific team conducted an extensive review to select the best solution, and ultimately, they chose ADI's AD797 operational amplifier .
To stabilize the laser frequency, the LIGO team uses ADI’s AD590 high-precision temperature sensor to measure the average temperature of the glass vacuum chamber that houses the laser.
While the raw output of the laser is standard, it quickly increases to thousands of watts within the resonant cavity of the laser arm. This generates enough power to create acoustic resonances in the glass mirrors, so LIGO uses ADA4700 high-voltage op amps to drive electrostatic actuators that actively damp the mirrors and keep them in line.
Another ADI device, the AD736 RMS-to-DC converter, is used to measure the energy delivered to the solenoids that drive LIGO’s mirror suspension system and accomplish any required tilt, pitch, and yaw.
Finally, let's take a look at LIGO's introduction by RICH ABBOTT, the chief designer of LIGO's analog circuits.