The artificial moon – the ambition to light the Earth without lights

The artificial moon is a “fiction” technology that stimulates tremendous curiosity. However, whether it is really necessary or not is a matter of controversy.

Moonlight from ancient times has mystical colors with countless legends and stories woven in all cultures. The origins of these legends are largely based on the fact that the light reflected from the surface of the Moon to the Earth creates strange silver.

Introduced Saudi Arabia’s Neom future city project will include an artificial Moon. It’s unclear how the Middle Eastern nation will implement the technology, but according to its government, Neom will be completed by 2025.

But before that, the name that made the public interested in this type of technology was China. In October 2018, Wu Chunfeng, chairman of a private construction contractor called Chengdu Institute of Aeronautical Science Research and Microelectronics Technology System (Casc), will launch an artificial moon to replace street lights.

More costly than traditional lamps
China’s artificial moon is in fact a group of satellites carrying large space mirrors that can reflect sunlight. The satellite group will fly in a defined trajectory around a certain city, providing night light to replace traditional electric lights.

A satellite about 480 km from the ground will be enough to light an area of ​​about 51 km2, equivalent to a city. Many new improvements promise this technology will light more than 10,000km2.

However, that is only according to the theoretical estimate of Chinese scientists. Dr. Wu said the first satellite will launch in 2020 and add three similar ones by 2022. Details of the specifications as well as where the project funding comes from remain a mystery.

The artificial moon sounds like a lot of potential, but satellite experts say there are many obstacles to it. Ryan Russell of the University of Texas (USA) said that these satellites will not be able to reflect any light on the ground.

The biggest problem with these satellites is that they need to fly close enough to the ground to reflect light. But at such low altitudes, they can’t stand still forever.

Geostationary satellites are inherently fixed relative to the Earth. However, to be “stationary”, they must be at a distance of at least 35,000 km. At that distance, the reflection of light on Earth is almost hopeless. At 480 km, the satellite will fly around the Earth at a speed of several thousand kilometers per hour, thus only reflecting light for about a millisecond for each location.

Naturally, every problem has a solution, one can keep the satellites in one place within a distance of 480 km, but will consume a lot of fuel. This fuel cost will certainly be greater than the electricity cost to maintain the lights in the city.

That’s not to mention the cost of launching a satellite refueling vessel that will far exceed the electricity consumption of the city below.

Is artificial moon necessary?
There are even questions about whether we really want to light up the whole city at night. Some cities around the world like Hong Kong are trying to reduce light pollution, making the darkness darker.

Excess night light disrupts the activity of nocturnal animals, blocks natural light from the stars and affects the circadian rhythms and human health.

The solution to the problem of urban lighting sometimes isn’t to turn on more lights, but to turn off the lights.

Lighting the entire city from above by satellite is more complicated than lighting only certain areas that need lighting, such as streets where traffic is in progress.

In addition, solutions to save lighting costs by “intelligent” sensor systems, human identification, lighting control systems using stored energy from the morning … may be dark. far superior to maintaining an artificial moon in the sky.

In fact, Russian scientist Vladimir Syromyatnikov developed the idea of ​​an artificial moon in 1994. The result was to create satellites made of thin 20-meter-diameter aluminum plates launched from the Mir space station. reflects off the Earth like a star.

However, the project also faces problems with satellite orbits, although the plan to deploy thousands of such reflective disks will help stabilize the light reflected on the Earth.

Eventually, people abandoned the idea of ​​making an artificial moon because satellites that emitted reflective discs with a diameter of 200 meters were having trouble breaking them up.

Today, the reality is that urban people are more concerned about light pollution than insufficient light. Advances in science and technology have made LED lights and smart devices a viable solution to the problem of power saving. Therefore, making “Moon” is not impossible, but becomes impractical.

Three huge black holes are about to collide in the universe

Scientists first observed the phenomenon of three galaxies colliding, placing supermassive black holes at their centers into orbit to merge.

The impact is nearly 1 billion light-years from Earth, in the star system SDSS J084905.51 + 111447.2. To observe this phenomenon, astronomers need to use both ground and space telescopes.

Scientists use the Sloan Digital Sky Survey Telescope in New Mexico to construct star systems by capturing light. The civic community of the Galaxy Zoo project later helped identify the star system as an intergalactic collision, according to CNN.

Many other research efforts have been made. Images taken with the infrared wavelength astronomy telescope (WISE) show infrared light emanating from the collision. The Tia X Chandra Observatory reveals many strong bright points at the center of each galaxy.

NASA also uses NuSTAR, the space telescope to look for X-rays in space, using technology to focus high-energy rays from the source of nuclear spectroscopy, to study this phenomenon. Survey results show that there was gas and dust emitted from the collision.

The scientists sequenced these elements and discovered gigantic black holes that exist and swallow matter in three galaxies. Research on the extremely rare collision was published in the Astrophysical Journal this week.

“At first we were just looking for black holes in the universe. However, through a selective system, we came across this interesting star system,” said Pfeifle, a researcher at George Mason University. , said.

“This is the most compelling evidence that a trio system with supermassive black holes is ‘eating’ and working,” Pfeifle said.

Although the collision was unimaginable, seeing it was not easy. Black holes are constantly swallowing material that obscures the event dust and gas from human light collectors.

Scientists collect images and data at different spectral wavelengths to get enough pieces to build the magnificent picture of the universe.

The phenomenon of two black holes about to collide with each other has been observed. However, science has never recorded a “trio” collision between galaxies and the giant black hole at their center. When collided, they form an even bigger black hole. Having up to 3 cosmic black holes together will make the merging process faster.

Another consequence of this process would be gravitational waves, or fluctuations in space and time structure.

“Double or black hole collisions are very rare. This is a natural consequence of the merging of galaxies, the same way they grow and evolve,” said Shobita Satyapal, co-author of the study. said.

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