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Dark energy may not be constant, which would lead to a revolution in physics




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The farthest X-ray of the universe, from quasar GB 1428, illustrates how fantastic these fantastic objects are. If we can figure out how to use quasars to measure the expansion of the universe, we can understand the nature of dark energy as never before.X-rays: NASA / CXC / NRC / C.Cheung et al; Optical: NASA / STScI; Radio: NSF / NRAO / VLA

For the past generation, we have recognized that our universe is a particularly dark place. Certainly, it is filled with stars, galaxies, and a multitude of light phenomena wherever we look. But each of the known processes that generate light is based on the particles of the Standard Model: the normal matter in our universe. All normal matter is – protons, neutrons, neutrons, etc. – represents only 5% of what is there.

The other 95% is a dark secret, but it can not be any of the particles we know. According to our best measurements, 27% of the universe is made of some kind of dark matter that does not respond with light or normal matter in any known way. And the remaining 68% is dark energy, which looks like a form of energy inherent in the space itself. A new set of observations is the challenge of what we currently think about dark energyIf he is holding, everything we know will change.

Without dark energy the universe would not accelerate. But to explain the distant supernova we see, among other features, it seems that dark energy is needed (or something exactly imitating it).NASA & ESA, possible models of the expanding Universe

The best technique we have to understand what the universe is made is not to go out and directly count everything out there. If that was the only way to do this, we would literally miss 95% of the Universe, because it is not directly measurable. Instead, what we can do is to use the sorrow of general relativity: the fact that all different forms of matter and energy affect the tissue of the space-time itself, as well as how it changes with time.

Specifically, by measuring what is today the rate of expansion as well as how the rate of expansion has changed through our cosmic history, we can use these known relationships to reconstruct the universe. From the complete set of available data, including supernova information, large universe structure, and cosmic microwave backlighting, we managed to construct an image of match: 5% normal, 27% dark matter, and 68% dark energy.

The limitations of dark energy from three independent sources: supernova, cosmic microwave backgrounds (CMB) and baroque acoustic oscillation (BAO) are in the large universe structure. Keep in mind that even without supernova, we need dark energy. The latest versions of this chart are available but the results are largely unchanged.The supernova cosmology project, Amanullah et al., Ap.J. (2010)

By our best knowledge, dark matter behaves as normal matter from a gravitational standpoint. The total mass of dark matter is fixed so that the universe expands and the volume grows, the dark matter density falls, just as it works for normal matter.

Dark energy is believed to be different. Instead of being a kind of particle, it seems to behave as if that kind of energy is inherent in the space itself. As space expands, dark energy density remains constant, instead of decreasing or increasing. As a result, after the universe has expanded sufficiently long, dark energy comes into dominance in the energy budget of the universe. As time passes, it gradually becomes more dominant over other components, which leads to the accelerated expansion that we are now observing.

While matter (both normal and dark) and radiation become less dense as the universe expands due to increased volume, dark energy is the form of energy inherent in the space itself. As the new space is created in the expanding universe, the dark energy density remains constant.E. Siegel / Out of the Galaxy

Traditionally, space expansion measurements rely on one of two perceptible indicators.

  1. Standard candles: where the intrinsic behavior of the light source is known, and we can measure the observed brightness, which determines its distance. By measuring distance and red shift for a large number of sources, we can reconstruct how the universe expanded.
  2. Standard ruler: where is known the inner size of an object or phenomenon, and we can measure the apparent angular size of that object or phenomenon. By converting from angular size to physical size and measuring red shift, we can similarly reconstruct how the universe expanded.

Difficulty with any of these techniques & nbsp; – what holds an astronomer at night & nbsp; – is the fear that our assumptions about intrinsic behavior can be misleading, changing our conclusions.

The two most successful methods for measuring large cosmic distances are based on either their apparent light (L) or their apparent angle (R), both of which are directly visible. If we can understand the inner physical properties of these objects, we can use them as standard candles (L) or standard rulers (R) in order to determine how the universe expanded, and hence, from which it originated, through its cosmic history.NASA / JPL-Caltech

So far, the best standard candles have been taken away in the history of the Universe: the light emitted when the Universe was about 4 billion years old. Given that we are almost 14 billion years old today, we have been able to measure extremely far, with the IA supernovaes that are the most reliable and robust indicator of the distance for the projection of dark energy.

Recently, however, a team of scientists began using quasars that emit X-rays, which are much brighter and, therefore, visible in earlier times: when the Universe was only a billion-year-old. IN interesting new paper, & nbsp; scientists Guido Risaliti and Elisabeta Luxus use quasars as a standard candle to move more than ever in measuring the nature of dark energy. What they have discovered is still provisional, but still amazing.

A new study using data from Chandra, XMM-Newton, and Sloan Digital Sky Survey (SDSS) suggests that dark energy could vary during cosmic time. The illustration of this artist explains how astronomers monitored the effects of dark energy about a billion years after the Great Bore by determining the distance to nearly 1,600 quasars, fast growing black hills that glitter very bright. Two of the farthest quasars studied are depicted in Chandra's paintings in inserts.Illustration: NASA / CXC / M.Weiss; X-ray: NASA / CXC / Univ. in Florence / G.Risaliti & E.Lusso

Using about 1,600 quasars of data and a new method for determining the distance to them, they found a strong correlation with the supernova results for quasars from the last 10 billion years: dark energy is real, about two thirds of the energy in the universe, and it appears to be in the cosmological nature constant.

But they also found distant quasars that showed something unexpected: at the greatest distances there is a deviation from that "constant" behavior. Risaliti he wrote a blog post here, with details of his works, including this jewel:

Our ultimate Hubble Diagram gave us totally unexpected results: while our universe expansion measurement was consistent with supernovaes in a common range of distances (from 4.3 billion to the present), the inclusion of more distant quasars shows a strong deviation from the expectations of the standard cosmological model ! If we explain this discrepancy through the dark energy component, we will discover that its density over time has to be increased.

The relationship between the distance module (y-section, distance measure) and the red shift (x-part), along with the quasar data, in yellow and blue, with supernova data in the cyan. Red points are the mean of the yellow points of the quasar together. While the supernova and kvazar data agree with each other, where both are present (up to a red shift of 1.5 or so), quasar data goes much further, indicating a deviation from constant interpretation.G. Exit E. Luxus, arXiv: 1811.02590

This is notoriously difficult to do, watch out, and the first thing you can think is that the quasars we have measured can be unreliable as a standard candle.

If that's your thoughts: congratulations! This is something that happened before, when people tried to use gamma rays as a distance indicator to overcome what supernova could learn. As we learn more about these raids, we have found that they are essentially non-standard, as well as discover our own prejudices about what types of firing can be detected. One or both of these two types of bias will probably play here, at least, and this will generally be considered the most likely explanation for this result.

Though revealing why it will be an educational initiative and challenge, it is unlikely that these evidence will convince many that dark energy is not constant.

The expected fate of the Universe is one of the eternal, accelerating expansion, corresponding to w, the amount of y-axis, which is equal to -1 exactly. If w is less than -1, as some data favors, our destiny will instead be Big Rip.C. Hikage et al., ArXiv: 1809.09148

But what if this new study is correct? What if dark energy is not constant? What if, as other remarks have made clear over the past two decades, does it change over time?

The top chart shows results from several different data sets, but I want to pay attention to & nbsp;w, shown on the y-axis. What we call & nbsp;w is the equation of the dark energy state, where & nbsp;w nbsp;= -1 is the value we would get for dark energy as a cosmological constant: the invariable form of energy is inherent in the space itself. If & nbsp;w differs from -1, however, it can change all that.

Different ways in which dark energy could develop into the future. Remaining constant or power gain (in Big Rip) could potentially rejuvenate the universe, while the sign of return could lead to a big scrape.NASA / CXC / M.Weiss

Our standard destiny, where & nbsp;w = -1, will cause the Universe to expand forever, with structures that are not related to today, and which separate the effects of dark energy. But if & nbsp;w or it changes with time or is uneven with -1, it all changes.

  • If & nbsp;w is less negative than -1 (eg, -0.9 or -0.75), dark energy will eventually weaken and eventually become irrelevant. If & nbsp;w& nbsp; grows with time, and always gets positive, it can cause the universe to break in a major crisis.
  • However, if this new result is true, & nbsp;w is worse than -1 (eg -1.2 or -1.5 or worse), then dark energy will only become stronger over time, causing widespread fabric to expand. Related structures, such as galaxies, solar systems, planets, and even atoms themselves, will be torn apart after enough time. The universe will end with a catastrophe known as the Great Rip.

The Big Rip Scenario will happen if we find that dark energy increases, while remaining negative in the direction over time.Jeremy Teaford / Vanderbilt University

Search for & nbsp; realizing the ultimate destiny of the Universe was fascinated by humanity since the dawn of time. With the appearance of general relativity and modern astrophysics, it was suddenly possible to answer that question from a scientific standpoint. Will the Universe expand forever? Recollapse? Oscillate? Or be torn apart by the physics that lies in the fundamentals of our reality?

The answer can be determined by looking at objects found in the very universe. The key to unlocking our ultimate cosmic destiny, however, depends on our understanding of what we are seeing and ensuring that our answers are not biased because of the assumptions we make about the objects we measure and observe. After all, dark energy may not be a constant, and only if we look at the universe itself, we will surely know.

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The farthest X-ray of the universe, from quasar GB 1428, illustrates how fantastic these fantastic objects are. If we can figure out how to use quasars to measure the expansion of the universe, we can understand the nature of dark energy as never before.X-rays: NASA / CXC / NRC / C.Cheung et al; Optical: NASA / STScI; Radio: NSF / NRAO / VLA

For the past generation, we have recognized that our universe is a particularly dark place. Certainly, it is filled with stars, galaxies, and a multitude of light phenomena wherever we look. But each of the known processes that generate light is based on the particles of the Standard Model: the normal matter in our universe. All normal substances are – protons, neutrons, neutrons, etc. – only 5% of what's there.

The other 95% is a dark secret, but it can not be any of the particles we know. According to our best measurements, 27% of the universe is made of some kind of dark matter that does not respond with light or normal matter in any known way. And the remaining 68% is dark energy, which looks like a form of energy inherent in the space itself. A new set of observations provokes what we currently think of dark energy. If he is holding, everything we know will change.

Without dark energy the universe would not accelerate. But to explain the distant supernova we see, among other features, it seems that dark energy is needed (or something exactly imitating it).NASA & ESA, possible models of the wider universe

The best technique we have to understand what the universe is made is not to go out and directly count everything out there. If that was the only way to do this, we would literally miss 95% of the Universe, because it is not directly measurable. Instead, what we can do is to use the sorrow of general relativity: the fact that all different forms of matter and energy affect the tissue of the space-time itself, as well as how it changes with time.

Specifically, by measuring what is today the rate of expansion as well as how the rate of expansion has changed through our cosmic history, we can use these known relationships to reconstruct the universe. From the complete set of available data, including supernova information, large universe structure, and cosmic microwave backlighting, we managed to construct an image of match: 5% normal, 27% dark matter, and 68% dark energy.

The limitations of dark energy from three independent sources: supernova, cosmic microwave backgrounds (CMB) and baroque acoustic oscillation (BAO) are in the large universe structure. Keep in mind that even without supernova, we need dark energy. The latest versions of this chart are available but the results are largely unchanged.The supernova cosmology project, Amanullah et al., Ap.J. (2010)

By our best knowledge, dark matter behaves as normal matter from a gravitational standpoint. The total mass of dark matter is fixed so that the universe expands and the volume grows, the dark matter density falls, just as it works for normal matter.

Dark energy is believed to be different. Instead of being a kind of particle, it seems to behave as if that kind of energy is inherent in the space itself. As space expands, dark energy density remains constant, instead of decreasing or increasing. As a result, after the universe has expanded sufficiently long, dark energy comes into dominance in the energy budget of the universe. As time passes, it gradually becomes more dominant over other components, which leads to the accelerated expansion that we are now observing.

While matter (both normal and dark) and radiation become less dense as the universe expands due to increased volume, dark energy is the form of energy inherent in the space itself. As the new space is created in the expanding universe, the dark energy density remains constant.E. Siegel / Out of the Galaxy

Traditionally, space expansion measurements rely on one of two perceptible indicators.

  1. Standard candles: where the intrinsic behavior of the light source is known, and we can measure the observed brightness, which determines its distance. By measuring distance and red shift for a large number of sources, we can reconstruct how the universe expanded.
  2. Standard ruler: where is known the inner size of an object or phenomenon, and we can measure the apparent angular size of that object or phenomenon. By converting from angular size to physical size and measuring red shift, we can similarly reconstruct how the universe expanded.

The difficulty with any of these techniques – the kind of things astronomers keep at night – is the fear that our assumptions about intrinsic behavior may be wrong, changing our conclusions.

The two most successful methods for measuring large cosmic distances are based on either their apparent light (L) or their apparent angle (R), both of which are directly visible. If we can understand the inner physical properties of these objects, we can use them as standard candles (L) or standard rulers (R) in order to determine how the universe expanded, and hence, from which it originated, through its cosmic history.NASA / JPL-Caltech

So far, the best standard candles have been taken away in the history of the universe: to the light that was emitted when the universe was about 4 billion years old. Given that we are almost 14 billion years old today, we have been able to measure extremely far, with the IA supernovaes that are the most reliable and robust indicator of the distance for the projection of dark energy.

Recently, however, a team of scientists began using quasars that emit X-rays, which are much brighter and, therefore, visible in earlier times: when the universe was only a billion years old. In an interesting new article, Guido Risaliti and Elisabetta Luxus use quasars as a standard candle to move more than ever in measuring the nature of dark energy. What they have discovered is still provisional, but still amazing.

A new study using data from Chandra, XMM-Newton, and Sloan Digital Sky Survey (SDSS) suggests that dark energy could vary during cosmic time. The illustration of this artist explains how astronomers monitored the effects of dark energy about a billion years after the Great Bore by determining the distance to nearly 1,600 quasars, fast growing black hills that glitter very bright. Two of the farthest quasars studied are depicted in Chandra's paintings in inserts.Illustration: NASA / CXC / M.Weiss; X-ray: NASA / CXC / Univ. in Florence / G.Risaliti & E.Lusso

Using about 1,600 quasars of data and a new method for determining the distance to them, they found a strong correlation with the supernova results for quasars from the last 10 billion years: dark energy is real, about two thirds of the energy in the universe, and it appears to be in the cosmological nature constant.

But they also found distant quasars, which showed something unexpected: at the greatest distances there is a deviation from that "constant" behavior. The resonate here wrote a post on the blog with details of his works, including this jewel:

Our ultimate Hubble Diagram gave us totally unexpected results: while our universe expansion measurement was consistent with supernovaes in a common range of distances (from 4.3 billion to the present), the inclusion of more distant quasars shows a strong deviation from the expectations of the standard cosmological model ! If we explain this discrepancy through the dark energy component, we will discover that its density over time has to be increased.

The relationship between the distance module (y-section, distance measure) and the red shift (x-part), along with the quasar data, in yellow and blue, with supernova data in the cyan. Red points are the mean of the yellow points of the quasar together. While the supernova and kvazar data agree with each other, where both are present (up to a red shift of 1.5 or so), quasar data goes much further, indicating a deviation from constant interpretation.G. Exit E. Luxus, arXiv: 1811.02590

This is notoriously difficult to do, watch out, and the first thing you can think is that the quasars we have measured can be unreliable as a standard candle.

If that's your thoughts: congratulations! This is something that happened before, when people tried to use gamma rays as a distance indicator to overcome what supernova could learn. As we learn more about these raids, we have found that they are essentially non-standard, as well as discover our own prejudices about what types of firing can be detected. One or both of these two types of bias are likely in the game, at the very least, and this will generally be considered the most likely explanation for this result.

Though revealing why it will be an educational initiative and challenge, it is unlikely that these evidence will convince many that dark energy is not constant.

The expected fate of the Universe is one of the eternal, accelerating expansion, corresponding to w, the amount of y-axis, which is equal to -1 exactly. If w is less than -1, as some data favors, our destiny will instead be Big Rip.C. Hikage et al., ArXiv: 1809.09148

But what if this new study is correct? What if dark energy is not constant? What if, as other remarks have made clear over the past two decades, does it change over time?

The top chart shows results from several different data sets, but what I want to pay attention is value w, shown on the y-axis. What we call w is the equation of dark energy states where w = -1 is the value we would get for dark energy as a cosmological constant: the invariable form of energy is inherent in the space itself. If w differs from -1, however, it can change all that.

Different ways in which dark energy could develop into the future. Remaining constant or power gain (in Big Rip) could potentially rejuvenate the universe, while the sign of return could lead to a big scrape.NASA / CXC / M.Weiss

Our standard destiny, where w = -1, will cause the Universe to expand forever, with structures that are not related to today, and which separate the effects of dark energy. But if w or it changes with time or is uneven with -1, it all changes.

  • If w is less negative than -1 (eg, -0.9 or -0.75), dark energy will eventually weaken and eventually become irrelevant. If w grows with time, and always gets positive, it can cause the universe to break in a big clutter.
  • However, if this new result is true, i w is worse than -1 (eg -1.2 or -1.5 or worse), then dark energy will only become stronger over time, causing widespread fabric to expand. Related structures, such as galaxies, solar systems, planets, and even atoms themselves, will be torn apart after enough time. The universe will end with a catastrophe known as the Great Rip.

The Big Rip Scenario will happen if we find that dark energy increases, while remaining negative in the direction over time.Jeremy Teaford / Vanderbilt University

The quest for understanding the ultimate destiny of the Universe was fascinated by humanity since the dawn of time. With the appearance of general relativity and modern astrophysics, it was suddenly possible to answer that question from a scientific standpoint. Will the Universe expand forever? Recollapse? Oscillate? Or be torn apart by the physics that lies in the fundamentals of our reality?

The answer can be determined by looking at objects found in the very universe. The key to unlocking our ultimate cosmic destiny, however, depends on our understanding of what we are seeing and ensuring that our answers are not biased because of the assumptions we make about the objects we measure and observe. After all, dark energy may not be a constant, and only if we look at the universe itself, we will surely know.


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