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Fermi’s paradox; Where are the extraterrestrials?



Fermi's paradox
Fermi’s paradox refers to the contradiction between the high probability of extraterrestrial intelligence in the universe and the fact that we have no conclusive evidence for the existence of such aliens.

Fermi’s paradox; Where are the extraterrestrials?

From NASA’s efforts to scientifically study UFOs or unidentified flying objects to the unveiling of alien bodies in Mexico , these days extraterrestrial intelligence has apparently become a more serious issue for politicians, researchers and the public. Although decades have passed since the first sighting of UFOs in the skies, there is still no evidence that definitively points to their extraterrestrial origin.

We’ve also been listening to space radio signals since about the middle of the last century, maybe for a message from aliens. On the other hand, for decades we have been trying to find extraterrestrial life in its very simple form in our own cosmic neighborhood by sending various spacecraft; But we still haven’t found any sure sign of extraterrestrial life. But how can we be really alone in such a big world?

Table of Contents
  • What is Fermi’s paradox?
  • The abundance of potentially habitable worlds
  • Drake’s equation
  • Large filter
  • Possible answers to Fermi’s paradox
  • Aliens are not advanced yet
  • Life is fragile
  • Intelligent life destroys itself
  • Other answers

What is Fermi’s paradox?

Given that our solar system is very young at approximately 4.5 billion years old compared to the 13.8 billion year old universe, and that interstellar travel may have been relatively easy to achieve over this long period of time, aliens would have to Today they were meeting the earth. But as far as we know, there has been no contact between us and extraterrestrials yet. As a result, the question arises, where are the aliens?

The contradiction between the high probability of the existence of alien intelligence and the lack of evidence for the existence of such aliens is called Fermi’s paradox. This paradox takes its name from Enrico Fermi, a renowned physicist who won the Nobel Prize. Fermi apparently made the above points in 1950 during a casual lunchtime conversation.

Enrico Fermi in his laboratory
Enrico Fermi in his laboratory.

The Search for Extraterrestrial Intelligence (SETI) Institute in California explains the paradox: “Farmey found that any civilization with a moderate level of rocket technology and colonialist motives could quickly colonize the entire galaxy. Over the course of a few tens of millions of years, any star system could be dominated by an empire. Tens of millions of years may seem like a long time, But it is very short compared to the age of the galaxy (which is almost a thousand times longer).”

Fermi died in 1954; As a result, other scientists were responsible for investigating and explaining his idea. One of these people was Michael Hart, an American astrophysicist who published an article in 1975 titled ” An Explanation for the Absence of Extraterrestrials on Earth ” in the Quarterly Journal of the Royal Astronomical Society (RAS). According to some, Hart’s article is the first research that examines Fermi’s paradox; However, it is difficult to prove this claim.

Any civilization with a moderate level of rocket technology and colonialist motives could quickly colonize the entire galaxy.

Hart writes in the abstract of his paper: “We see that no intelligent beings from space currently exist on Earth.” This fact can be explained by the hypothesis that there are no other advanced civilizations in our galaxy.” More research into biochemistry, planet formation, and atmospheres is needed to determine the exact answer, he noted.

Hart argued that if intelligent aliens began their interstellar journey more than two million years ago, they likely visited Earth at some point in our planet’s history. The apparent lack of such visitations, he believes, is most likely due to the lack of intelligent aliens. However, Hart offered four other potential explanations:

  • The aliens never got here because of a physical problem that might be related to astronomy, biology, or engineering that makes space travel impossible.
  • The aliens simply chose never to come to us.
  • Advanced extraterrestrial civilizations emerged too late to reach us.
  • Aliens have visited Earth in the past, But we have not seen them.

Frank Tipler, professor of physics at Tulane University, followed Hart’s argument in a 1980 paper titled ” There Is No Extraterrestrial Intelligence.” The bulk of his paper focuses on how to obtain resources for interstellar travel. According to Tipler, interstellar travel can be achieved by having a self-replicating artificial intelligence that creates multiple copies of itself as it moves from one-star system to another.

Because evidence of such advanced intelligence has never been found on Earth, Tipler argues that we are probably the only intelligent beings in the universe. He also wrote in an article in 1980 that those who believe in extraterrestrial intelligence are similar to UFO enthusiasts; Because they both believe that “we will be saved from ourselves by miraculous interstellar intervention.”

Nowadays, extraterrestrial intelligence is a popular topic, and every year numerous articles from different research groups are published about it. The idea that advanced civilizations may exist beyond Earth has been bolstered by the current revolution in the discovery and study of exoplanets.

The abundance of potentially habitable worlds

A view of an exoplanet facing its star

The universe is incredibly vast and ancient. Data collected by various telescopes show that the observable universe is approximately 92 billion light-years across (and growing faster and faster all the time). Also, separate measurements indicate that the universe is nearly 13.82 billion years old. As a result, alien civilizations have had a lot of time to emerge and expand; But before reaching us, they probably have to cross a big cosmic gulf.

When Fermi came up with his famous idea, the only worlds known to scientists were the planets in our solar system. But in 1992, astronomers saw worlds orbiting a superdense stellar body called a pulsar, and a few years later, the first exoplanet was confirmed around a Sun-like star.

Currently, there are more than five thousand confirmed exoplanets and more are being discovered every year. The large number of alien worlds suggests that life may abound throughout the universe.

Read More: 25 surprising facts about the solar system

The large number of alien worlds suggests that life may abound throughout the universe

Now, with advanced instruments like the James Webb Space Telescope, scientists have found it possible to examine the chemical composition of the atmospheres of some nearby exoplanets. However, “adjacent” is a relative term. The nearest known exoplanet, Proxima b, is located at a distance of 4.2 light years from us, which is approximately 40 trillion kilometers.

The ultimate goal is to find out how likely it is to form rocky planets in the “habitable belt” or “habitable zone” of stars. This region is traditionally defined as the range of orbital distances where water can exist on the surface of the world. However, habitability is not just about water, other factors such as the activity of the host star and the composition of the planet’s atmosphere must also be considered. Also, due to some reasons, the habitable area is considered too simple based on the aforementioned definition. For example, icy moons in our own solar system, such as Jupiter’s Europa and Saturn’s Enceladus, lie far beyond the Sun’s habitable zone; But they may still host life in the seas below their surface.

However, it seems that there are many settlements in the world. For example, a November 2013 study using data from NASA’s Kepler space telescope found that one in five Sun-like stars has a roughly Earth-sized planet orbiting it in the habitable zone. A few months later, Kepler scientists announced the discovery of 715 new worlds. Many of these planets were confirmed using a new technique called “multiple proof” that works in part on the logic of probability. For example, objects that pass in front of their star through the telescope or exert gravitational forces on it, are more likely to be planets instead of companion stars; Because with two stars so close to each other, the whole system is likely to become unstable over time.

Artistic rendering of NASA's Kepler Space Telescope

An artist’s rendering of NASA’s Kepler Space Telescope, an exoplanet finder.

However, Sun-like stars are a minority population in our galaxy. Almost three-quarters of the stars in the Milky Way are small, dim flares known as red dwarfs. Astronomers have found several rocky worlds orbiting in the habitable zone of red dwarfs; Like Proxima B and three planets located in Trappist 1; A system that is about 39 light-years away from Earth and contains a total of seven rocky worlds.

However, it is not known how habitable the planets around red dwarfs are; Because these stars are extremely unstable especially when they are young. As a result, their stellar eruptions may quickly destroy the nascent atmospheres of their neighboring planets, making it very difficult for life to flourish. Scientists say more studies are needed to better understand these stars and the ability of life to survive around them.

Researchers are acquiring more tools to study the stars. For example, NASA’s Passing Exoplanet Mapper satellite was successfully launched in April 2018, tasked with discovering extrasolar worlds as a successor to the Kepler telescope. Also, the James Webb Space Telescope, launched in December 2021, will study biological traces in the atmospheres of alien planets, among other tasks. The European Space Agency’s PLATO (Planetary Transit and Stellar Oscillation) spacecraft is also expected to launch in 2026.

Sun-like stars are a minority population in our galaxy

Three massive ground-based observatories, including the Extremely Large Telescope, the Giant Magellan Telescope, and the 30-meter telescope, which is powerful enough to probe the atmospheres of exoplanets, are slated to begin operating by the end of this decade. On the other hand, one of the more ambitious projects known as “Bractro Starshot” wants to study Proxima b and other nearby worlds with an array of tiny laser-guided nanoprobes. If the technology development process goes well, the first such interstellar spacecraft could be launched by around 2050.

These spacecraft and probes will help scientists improve their relatively rudimentary understanding of astrobiology. For example, we still don’t know if there are life-hosting worlds in our cosmic neighborhood. Studies conducted on Earth indicate that microbes can survive in unfavorable environments; A finding that suggests microbial life may exist on Mars, Europa, Enceladus, or Saturn’s giant moon Titan. But we haven’t explored either of those worlds enough to know for sure.

Drake’s equation

Despite the explanations given, Fermi’s paradox paints a much larger picture of microbes. To resolve this paradox, we need to know not only how common life is on alien planets, but also to what extent those extraterrestrials acquire the ability or desire to communicate with other intelligent life forms or to venture among the stars.

The number of intelligent and detectable alien civilizations is estimated by the Drake equation. According to the Seti Institute, the equation is written as “N = R* • fp • ne • fl • fi • fc • L” and has the following variables:

  • N: number of Milky Way civilizations whose electromagnetic emissions can be detected.
  • R*: the rate of formation of stars suitable for the development of intelligent life (number per year).
  • fp: fraction of those stars with planetary systems.
  • ne: the number of planets in each solar system with habitable environments.
  • fl: fraction of suitable planets where life appears.
  • fi: Fraction of life-bearing planets in which intelligent life arises.
  • fc: fraction of civilizations with technologies capable of producing recognizable signs of their existence.
  • L: average length of time such civilizations produce such signs (years).

None of the values ​​of Drake’s equation are currently known with certainty; This means that it is difficult to predict the number of civilizations willing to communicate. As a result, the Fermi paradox is fertile ground for speculation, and scientists and laypeople alike have come up with hundreds of possible explanations over the years.

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Large filter

Asteroid hitting the earth

The large filter is a general idea that attempts to explain Fermi’s paradox. According to this hypothesis, intelligent interstellar life must take many critical steps to evolve, and at least one of these steps must be highly impossible. In fact, the large filter assumes that there is at least one very large barrier that virtually no species can pass to the next stage. But in order to become a truly advanced and space-faring civilization, what important obstacles must be overcome? Here are a few things:

  • A planet capable of harboring life must form in the habitable zone of a star.
  • Life must grow on that planet.
  • Life forms must be able to reproduce using molecules such as DNA or RNA.
  • Simple cells (prokaryotes) must evolve into more complex cells (eukaryotes).
  • Multicellular organisms must grow.
  • Sexual reproduction, which greatly increases genetic diversity, must occur.
  • Complex organisms capable of using tools must evolve.
  • Those beings must develop the advanced technology needed to colonize space. (This stage is roughly where humans are today.)
  • The spacefaring species must continue to colonize other worlds and star systems while avoiding their own destruction.

The assumption of the large filter is that there is at least one very large barrier that virtually no species can pass.

But which stage is the big filter? Unfortunately, no one knows. Maybe the rarity of life is actually a big filter. Maybe life is common, But most organisms do not evolve beyond unicellularity. It may be the great filter of annihilation technology that wipes out its advanced creators. It is possible that an external factor such as the impact of a stray asteroid is the cause of the destruction of life.

If we have passed the great filter, we can hope for our future. Maybe a wise man is the kind that can colonize the world. But if the big filter is still ahead, we’re probably doomed. In the next section, we mention some hypothetical explanations for Fermi’s paradox.

Possible answers to Fermi’s paradox

A very wide range of answers can be considered for Fermi’s paradox. Probably the most obvious and likely answer is that we haven’t looked hard enough for alien life, and interstellar travel is difficult. As mentioned, the first planets beyond the solar system were discovered just 30 years ago; As a result, in the field of exploring alien worlds, we are still in the most elementary stage.

We have yet to find many planets that look exactly like Earth and orbit a Sun-like star. However, even if we were to achieve such success, the distance between the star systems is too great, and travel to them would be extremely difficult. For example, the closest star system to us, Alpha Centauri, is four light years away from Earth. For comparison, the distance from Earth to Neptune is only 0.0005 light years; As a result, it takes tens of years to reach the nearest neighboring star with current technology.

Aliens are not advanced yet

In 2015, scientists analyzing data from the Hubble Space Telescope and the Kepler Space Telescope concluded that Earth was one of the first worlds in the universe to harbor life. According to the researchers, only 8 percent of all potentially habitable worlds that will emerge in the entire lifetime of the universe existed when Earth formed about 4.5 billion years ago. Consequently, this is one possible explanation for the paradox: aliens will come; But not now.

Life is fragile

Perhaps life is too fragile to last long. A 2016 study in the journal Astrobiology showed that the early part of a rocky planet’s history could be very favorable for life; This means that life may usually emerge 500 million years or more after the planet cooled and liquid water became available. Our own Earth history seems to support this conclusion. There is (controversial) evidence that life appeared on Earth about 4.1 billion years ago, and was definitely established by 3.8 billion years ago. But those good days may not last long as a result of the greenhouse effect (as happened on Venus long ago) or other climate changes.

Perhaps life is too fragile to last long

“Between initial heat pulses, freezing, unstable content changes, and out-of-control positive feedbacks, maintaining life on a rocky, wet young planet in the habitable zone is like trying to ride a wild bull,” said Aditya Chopra and Charlie Lineweaver, researchers of the 2016 study. Life often falls.” The authors add that life may be rare in the universe; not because it is difficult to start, but because it is difficult to maintain habitable environments during the first billion years.

Intelligent life destroys itself

Conditions leading to the collapse of life may occur much later. Some thinkers believe that civilizations may self-destruct shortly after they become technologically capable. Again, Earth supports this hypothesis: humanity came alarmingly close to nuclear war during the 1962 Cuban Missile Crisis. Also, we are probably destroying ourselves and many other types of terrestrial life right now through climate change caused by our own activities or the development of dangerous technologies such as artificial intelligence.

Other Answers

There are many other factors to consider. For example, Alan Stern, a planetary scientist and director of NASA’s New Horizons mission, believes that buried oceans, such as the seas of Enceladus and Europa, are likely the most common environments for life in the Milky Way. As a result, it seems unlikely that the evolved beings in such regions would achieve the necessary technology to build spacecraft. In fact, many of them may not even know that there are other worlds to explore.

Alien psychology can also be effective. For example, maybe there are many advanced alien civilizations in the world; But most of them don’t want to communicate with us or visit Earth. Perhaps Earth and its inhabitants are simply not interesting enough for aliens to waste their time on, and until humanity shows enough intelligence and competence to be accepted into the “galactic club”, it will not attract the attention of extraterrestrials.

Most intelligent aliens may tend to be silent as a general rule; Because they are worried that contact with their cosmic neighbors will lead them to slavery or death. Some researchers, including the late Stephen Hawking, have cited such possibilities with the argument that humans should not actively show their presence.

Most intelligent aliens may tend to be silent as a general rule

In addition to all the aforementioned assumptions, finding intelligent aliens in a very, very vast and ancient universe is associated with complex logistical problems. Mankind only appeared on Earth 200,000 years ago and only started listening to possible radio signals from extraterrestrials in 1960. As a result, the probability that it overlaps with a recognizable alien civilization in terms of time and place does not seem very high.

Most researchers say that there is probably no single solution to Fermi’s paradox. A combination of factors, including perhaps some of the ones discussed above, is probably responsible for the great silence that currently reigns in the world. The nature of those factors will probably be more clearly noticed relatively soon.

For example, suppose scientists find evidence of ancient or current microbial life on Mars, Europa, or any other body in our own solar system. The discovery of such creatures near the Earth, which are completely different from terrestrial life, speaks of the “Second Genesis” and definitely shows the commonness of life throughout the universe. At that point, researchers can cross off a possible explanation on the long list of explanations for Fermi’s paradox. 


Black holes may be the source of mysterious dark energy




black holes
The expansion of black holes in the universe can be a sign of the presence of dark energy at the center of these cosmic giants. The force that drives the growth of the world.

Black holes may be the source of mysterious dark energy


According to new research, supermassive black holes may carry the engines driving the universe’s expansion or mysterious dark energy. The existence of dark energy has been proven based on the observation of stars and galaxies, but so far no one has been able to find out its nature and source.

The familiar matter around us makes up only 5% of everything in the universe. The remaining 27% of the universe is made up of dark matter, which does not absorb or emit any light. On the other hand, a large part of the universe, or nearly 68% of it consists of dark energy.

According to new evidence, black holes may be the source of dark energy that is accelerating the expansion of the universe. This research is the result of the work of 17 astronomers in nine countries, which was conducted under the supervision of the University of Hawaii. British researchers from Raleigh Space, England’s Open University, and King’s College London collaborated in this research.

Black hole accretion pillAn artist’s rendering of a supermassive black hole complete with a fiery accretion disk.

By comparing supermassive black holes spanning 9 billion years of the universe’s history, researchers have found a clue that the greedy giant objects at the heart of most galaxies could be the source of dark energy. The articles of this research were published in The Astrophysical Journal and The Astrophysical Journal Letters on February 2 and 15. Chris Pearson, one of the authors of the study and an astrophysicist at the Appleton Rutherford Laboratory (RAL) in the UK says:

If the theory of this research is correct, it could revolutionize the whole of cosmology, because at least we have found a solution to the origin of dark energy, which has puzzled cosmologists and theoretical physicists for more than twenty years.

The theory that black holes can carry something called vacuum energy (an embodiment of dark energy) is not new, and the discussion of its theory actually goes back to the 1960s; But the new research assumes that dark energy (and therefore the mass of black holes) increases over time as the universe expands. Researchers have shown how much of the universe’s dark energy can be attributed to this process. According to the findings, black holes could hold the answer to the total amount of dark energy in the current universe. The result of this puzzle can solve one of the most fundamental problems of modern cosmology.

Rapid expansion

Our universe began with the Big Bang about 13.7 billion years ago. The energy from this explosion of space once caused the universe to expand so rapidly that all the galaxies were moving away from each other at breakneck speed. However, astronomers expected the rate of this expansion to slow down due to the gravitational influence of all the matter in the universe. This attitude toward the world prevailed until the 1990s; That is when the Hubble Space Telescope made a strange discovery. Observations of distant exploding stars have shown that in the past the universe was expanding at a slower rate than it is now.

Therefore, contrary to the previous idea, not only the expansion of the universe has not slowed down due to gravity, but it is increasing and speeding up. This result was very unexpected and astronomers sought to justify it. Thus, it was assumed that “dark energy” pushes objects away from each other with great power. The concept of dark energy was very similar to a cosmic constant proposed by Albert Einstein that opposes gravity and prevents the universe from collapsing but was later rejected.

Stellar explosions

But what exactly is dark energy? The answer to this question seems to lie in another cosmic mystery: black holes. Black holes are usually born when massive stars explode and die. The gravity and pressure in these intense explosions compress a large amount of material into a small space. For example, a star roughly the same mass as the Sun can be compressed into a space of only a few tens of kilometers.

The gravitational pull of a black hole is so strong that even light cannot escape it and everything is attracted to it. At the center of the black hole is a space called singularity, where matter reaches the point of infinite density. The point is that singularities should not exist in nature.

Speed ​​up dark energyDark energy explains why the universe is expanding at an accelerating rate.

Black holes at the center of galaxies are much more massive than black holes from the death of stars. The mass of galactic “massive” black holes can reach millions to billions of times the mass of the Sun. All black holes increase in size by accreting matter and swallowing nearby stars or merging with other black holes; Therefore, we expect these objects to become larger as they age. In the latest paper, researchers investigated the supermassive black holes at the centers of galaxies and found that the mass of these objects has increased over billions of years.

Fundamental revision

The researchers compared the past and present observations of elliptical galaxies that lack the star formation process. These dead galaxies have used up all their fuel, and as a result, their increase in the number of black holes over time cannot be attributed to normal processes that involve the growth of black holes by accreting matter.

Instead, the researchers suggested that these black holes actually carry vacuum energy, which has a direct relationship with the expansion of the universe, so as the universe expands, their mass also increases.

Black hole visualizationVisualization of a black hole that could play a fundamental role in dark energy.

Revealing dark energy

Two groups of researchers compared the mass of black holes at the center of two sets of galaxies. They were a young, distant cluster of galaxies with lights originating nine billion years ago, while the closer, older group was only a few million light-years away. Astronomers found that supermassive black holes have grown between seven and twenty times larger than before so this growth cannot be explained simply by swallowing stars or colliding and merging with other black holes.

As a result, it was hypothesized that black holes are probably growing along with the universe, and with a type of hypothetical energy known as dark energy or vacuum that leads to their expansion, they overcome the forces of light absorption and destruction of the stars in their center.

If dark energy is expanding inside the core of black holes, it can solve two long-standing puzzles of Einstein’s general relativity; A theory that shows how gravity affects the universe on massive scales. The new finding firstly proves how the universe does not fall apart due to the overwhelming force of gravity, and secondly, it eliminates the need for singularities (points of infinity where the laws of physics are violated) to describe the workings of the dark heart of black holes.

To confirm their findings, astronomers need more observations of the mass of black holes over time, and at the same time, they need to examine the increase in mass as the universe expands.

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Scientists’ understanding of dark energy may be completely wrong




dark energy
The standard model of cosmology says that the strength of dark energy should be constant, But inconclusive findings suggest that this force may have weakened.

Scientists’ understanding of dark energy may be completely wrong

On April 4th, astronomers who created the largest and most detailed 3D map ever made of the universe announced that they may have found a major flaw in their understanding of dark energy, the mysterious force driving the universe’s expansion.

Dark energy has been postulated as a stable force in the universe, both in the current era and throughout the history of the universe; But new data suggests that dark energy may be more variable, getting stronger or weaker over time, reversing or even disappearing.

Adam Reiss, an astronomer at Johns Hopkins University and the Space Telescope Science Institute in Baltimore, who was not involved in the new study, was quoted by the New York Times as saying, “The new finding may be the first real clue we’ve had in 25 years about the nature of dark energy.” In 2011, Reiss won the Nobel Prize in Physics along with two other astronomers for the discovery of dark energy.

The recent conclusion, if confirmed, could save astronomers and other scientists from predicting the ultimate fate of the universe. If the dark energy has a constant effect over time, it will eventually push all the stars and galaxies away from each other so much that even the atoms may disintegrate and the universe and all life in it, light, and energy will be destroyed forever. Instead, it appears that dark energy can change course and steer the universe toward a more fruitful future.

Dark energy may become stronger or weaker, reverse or even disappear over time

However, nothing is certain. The new finding has about a 1 in 400 chance of being a statistical coincidence. More precisely, the degree of certainty of a new discovery is three sigma, which is much lower than the gold standard for scientific discoveries called five sigma or one in 1.7 million. In the history of physics, even five-sigma events have been discredited when more data or better interpretations have emerged.

The recent discovery is considered an initial report and has been published as a series of articles by the group responsible for an international project called “Dark Energy Spectroscopy Instrument” or DESI for short. The group has just begun a five-year effort to create a three-dimensional map of the positions and velocities of 40 million galaxies over the 11 billion-year history of the universe. The researchers made their initial map based on the first year of observations of just six million galaxies. The results were presented April 4 at the American Physical Society meeting in Sacramento, California, and at a conference in Italy.

“So far we’re seeing initial consistency with our best model of the universe,” DESI director Michael Levy said in a statement released by Lawrence Berkeley National Laboratory, the center overseeing the project. “But we also see some potentially interesting differences that may indicate the evolution of dark energy over time.”

“The DESI team didn’t expect to find the treasure so soon,” Natalie Palanque-Delaberville, an astrophysicist at Lawrence Berkeley Lab and project spokeswoman, said in an interview. The first year’s results were designed solely to confirm what we already knew. “We thought we would basically approve the standard model.” But the unknowns appeared before the eyes of the researchers.

The researchers’ new map is not fully compatible with the standard model

When the scientists combined their map with other cosmological data, they were surprised to find that it didn’t completely fit the Standard Model. This model assumes that dark energy is stable and unchanging; While variable dark energy fits the new data. However, Dr. Palanque-Delaberville sees the new discovery as an interesting clue that has not yet turned into definitive proof.

University of Chicago astrophysicist Wendy Friedman, who led the scientific effort to measure the expansion of the universe, described the team’s results as “tremendous findings that have the potential to open a new window into understanding dark energy.” As the dominant force in the universe, dark energy remains the greatest mystery in cosmology.

Imaging the passage of quasar light through intergalactic clouds
Artistic rendering of quasar light passing through intergalactic clouds of hydrogen gas. This light provides clues to the structure of the distant universe.
NOIRLab/NSF/AURA/P. Marenfeld and DESI collaboration

The idea of ​​dark energy was proposed in 1998; When two competing groups of astronomers, including Dr. Rees, discovered that the rate of expansion of the universe was increasing rather than decreasing, contrary to what most scientists expected. Early observations seemed to show that dark energy behaved just like the famous ” fudge factor ” denoted by the Greek letter lambda. Albert Einstein included lambda in his equations to explain why the universe does not collapse due to its own gravity; But later he called this action his biggest mistake.

However, Einstein probably judged too soon. Lambda, as formulated by Einstein, was a property of space itself: as the universe expands, the more space there is, the more dark energy there is, which pushes ever harder, eventually leading to an unbridled, lightless future.

Dark energy was placed in the standard model called LCDM, consisting of 70% dark energy (lambda), 25% cold dark matter (a collection of low-speed alien particles), and 5% atomic matter. Although this model has now been discredited by the James Webb Space Telescope , it still holds its validity. However, what if dark energy is not as stable as the cosmological model assumes?

The problem is related to a parameter called w, a special measure for measuring the density or intensity of dark energy. In Einstein’s version of dark energy, the value of this parameter remains constant negative one throughout the life of the universe. Cosmologists have used this value in their models for the past 25 years.

Albert Einstein included lambda in his equations to explain why the universe is collapsing under its own gravity.

But Einstein’s hypothesis of dark energy is only the simplest version. “With the Desi project we now have the precision that allows us to go beyond that simple model to see if the dark energy density is constant over time or if it fluctuates and evolves over time,” says Dr. Palanque-Delabreville.

The Desi project, 14 years in the making, is designed to test the stability of this energy by measuring the expansion rate of the universe at different times in the past. In order to do this, scientists equipped one of the telescopes of the Keith Peak National Observatory in Arizona, USA, with five thousand optical fiber detectors that can perform spectroscopy on a large number of galaxies at the same time to find out how fast they are moving away from Earth.

The researchers used fluctuations in the cosmic distribution of galaxies, known as baryonic acoustic variations , as a measure of distance. The sound waves in the hot plasma accumulated in the universe, when it was only 380,000 years old, carved the oscillations on the universe. At that time, the oscillations were half a million light years across. 13.5 billion years later, the universe has expanded a thousandfold, and the oscillations, now 500 million light-years across, serve as convenient rulers for cosmic measurements.

Desi scientists divided the last 11 billion years of the universe into 7 time periods and measured the size of the fluctuations and the speed of the galaxies in them moving away from us and from each other. When the researchers put all the data together, they found that the assumption that dark energy is constant does not explain the expansion of the universe. Galaxies appeared closer than they should be in the last three periods; An observation that suggests dark energy may be evolving over time.

“We’re actually seeing a clue that the properties of dark energy don’t fit a simple cosmological constant, and instead may have some deviations,” says Dr. Palanque-Delaberville. However, he believes that the new finding is too weak and is not considered proof yet. Time and more data will determine the fate of dark energy and the researchers’ tested model.

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Why the James Webb telescope does not observe the beginning of the universe?




James Webb telescope

The James Webb Space Telescope is one of the most advanced telescopes ever built. Planning to launch James Webb began more than 25 years ago, and construction efforts took more than a decade. On December 25, 2021, this telescope was launched into space and within a month it reached its final destination, 930,000 miles away from Earth. Its position in space gives it a relatively unobstructed view of the world.

Why the “James Webb” telescope does not observe the beginning of the universe?

The design of this telescope was a global effort led by NASA and aims to push the boundaries of astronomical observation with revolutionary engineering. Its mirror is huge, about 21 feet (6.5 meters) in diameter, which is about three times the size of the Hubble Space Telescope, which was launched in 1990 and is still operating.

According to SF, it’s the telescope’s mirror that allows it to gather light. James Webb is so big that it can see the faintest and most distant galaxies and stars in the universe. Its advanced instruments can reveal information about the composition, temperature, and motion of these distant cosmic bodies.

Astrophysicists constantly look back to see what stars, galaxies, and supermassive black holes looked like when their light began its journey toward Earth, and use this information to better understand their growth and evolution. For the space scientist, the James Webb Space Telescope is a window into that unknown world. How far can James Webb look into the universe and its past? The answer is about 13.5 billion years.

Time travel

A telescope does not show stars, galaxies, and exoplanets as they are. Instead, astrologers have a glimpse of how they were in the past. It takes time for light to travel through space and reach our telescope. In essence, this means that looking into space is also a journey into the past.

This is true even for objects that are quite close to us. The light you see from the sun has left about eight minutes and 20 seconds earlier. This is how long it takes for sunlight to reach the earth.

You can easily do calculations on this. All light, whether it’s sunlight, a flashlight, or a light bulb in your home, travels at a speed of 186,000 miles (approximately 300,000 kilometers) per second. This is more than 11 million miles, which is about 18 million kilometers per minute. The sun is about 93 million miles (150 million kilometers) from the earth. which brings the time of reaching the light to about eight minutes and 20 seconds.

Why the “James Webb” telescope does not observe the moment of the beginning of the universe?

But the farther something is, the longer it takes for its light to reach us. That’s why the light we see from the closest star to us other than the Sun, Proxima Centauri, dates back four years. This star is about 25 trillion miles (about 40 trillion kilometers) from Earth, so it takes a little over four years for its light to reach us.

Recently, James Webb has observed the star Earendel, which is one of the most distant stars ever discovered and the light that James Webb sees is about 12.9 billion years old.

The James Webb Space Telescope travels much further into the past than other telescopes such as the Hubble Space Telescope. For example, although Hubble can see objects 60,000 times fainter than the human eye, James Webb can see objects almost 9 times fainter than even Hubble.

Read more: How can solar storms destroy satellites so easily?

Big Bang

But is it possible to go back to the beginning of time?

Big Bang is the term used to define the beginning of the universe as we know it. Scientists believe that this happened about 13.8 billion years ago. This theory is the most accepted theory among physicists to explain the history of our universe.

However, the name is a bit misleading because it suggests that some kind of explosion, like a firework, created the universe. The Big Bang more accurately represents space that is rapidly expanding everywhere in the universe. The environment immediately after the Big Bang resembled a cosmic fog that covered the universe and made it difficult for light to pass through. Eventually, galaxies, stars, and planets began to grow.

That’s why this period is called the “Cosmic Dark Age” in the world. As the universe continued to expand, the cosmic fog began to lift and light was finally able to travel freely through space. In fact, few satellites have observed the light left over from the Big Bang some 380,000 years after it happened. These telescopes are designed to detect the glow left over from the nebula, whose light can be traced in the microwave band.

However, even 380,000 years after the Big Bang, there were no stars or galaxies. The world was still a very dark place. The cosmic dark ages did not end until several hundred million years later when the first stars and galaxies began to form.

The James Webb Space Telescope was not designed to observe the time to the moment of the Big Bang, but to see the period when the first objects in the universe began to form and emit light.

Before this time period, due to the conditions of the early universe and the lack of galaxies and stars, there was little light for the James Webb Space Telescope to observe.

By studying ancient galaxies, scientists hope to understand the unique conditions of the early universe and gain insight into the processes that helped them flourish. This includes the evolution of supermassive black holes, the life cycles of stars, and what exoplanets are made of.

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