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




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The most distant ray of space in the universe, from the quasar GB 1428, helps to show how bright 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.RTG: NASA / CXC / NRC / C. Cheung et al; Optical: NASA / STScI; Radio: NSF / NRAO / VLA

For the past generation, we realized that our universe is a particularly dark place. Sure, it is filled with stars, galaxies and a ubiquitous light-emitting phenomenon. But each of the known processes that create light is based on parts of the standard model: normal matter in our universe. All normal matter is – protons, neutron electrons, neutrinos, etc. & nbsp; – represents only 5% of what is out there.

Another 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, in any known way, relate to light or normal matter. And the remaining 68% is dark energy, which appears to be a form of energy inherent in the universe. New set of observations it is challenging what we currently think of dark energy. If it stops, everything we know will change.

Without the dark energy the universe would not be accelerated. But to explain distant supernovae, we see, among other things, that dark energy (or something that mimics it exactly) is necessary.NASA & ESA, about possible models of expanding space

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

In particular, by measuring what is the speed of expansion today, and how the extent of enlargement has changed throughout our cosmic history, we can use these familiar relationships to reconstruct what the universe must be composed of. From the full set of available data, including information from supernovae, the vast structure of space and cosmic microwave radiation, we were able to create a contrasting image: 5% of normal mass, 27% of dark matter, and 68% of dark energy.

Dark energy limitations from three independent sources: the supernovae, the cosmic microwave background (CMB), and baryon acoustic oscillations (BAOs) located in the great cosmic structure of the universe. Note that even without supernova we would need dark energy. There are other current versions of this chart, but the results are largely unchanged.Supernova Cosmology Project, Amanullah et al., Ap.J. (2010)

To our best knowledge, dark matter acts as a normal matter from a gravitational point of view. The total mass of the dark matter is solid, so as the universe expands and the volume increases, the density of the dark matter decreases, just as with the normal mass.

Dark energy, however, seems to be different. Rather than particle type, it seems to behave as if it were the kind of energy that is inherent in space itself. As the space expands, the dark energy density remains constant, rather than falling or growing. As a result, after the long expansion of the universe, dark energy dominates the energy budget of the Universe. Over time, it gradually becomes more dominant than other components, leading to the accelerated expansion we see today.

While matter (normal and dark) and radiation are less dense, as the universe expands due to the increasing volume, dark energy is the form of energy that is inherent in space itself. When a new space is created in the expanding universe, the density of dark energy remains constant.E. Siegel / Beyond the Galaxy

Traditional space expansion measurement techniques were based on one of two observable indicators.

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

The difficulty with one of these techniques – which is a thing that leads astronomers at night – is that our assumptions about internal behavior may be wrong and anticipate our conclusions.

Two of the most successful methods of measuring large cosmic distances are based either on their apparent brightness (L) or on their seemingly angularly large (R) sizes that are directly observable. If we can understand the internal physical properties of these objects, we can use them either as standard candles (L) or as standard rulers (R) to see how the universe has spread and, therefore, what it is made of, over its space history.NASA / JPL-Caltech

So far our best standard candles have taken us very far in the history of the universe: the light that was launched when the universe was about 4 billion years old. Since we live nearly 14 billion years ago, we are able to measure extremely far, with type Ia supernovae, which provide the most reliable and robust distance indicator for dark energy.

Recently, however, a team of scientists began to use quasars that emit X-rays that are much brighter and therefore visible even in earlier times: when the universe was just one billion years old. in interesting new post, scientists Guido Risaliti and Elisabeth Lusso use quasars as a standard candle to go further than we ever measured the nature of dark energy. What they find is still preliminary, but still overwhelming.

A new study using Chandra, XMM-Newton and Sloan Digital Sky Survey (SDSS) suggests that dark energy may change in space. This artist's explanation explains how astronomers watched the effects of dark energy for about one billion years after the Big Bang, with a distance of almost 1600 quasars and fast-growing black holes that shine very clearly. Two of the farthest studied quasars are depicted in Chandra images in the inserts.Illustration: NASA / CXC / M.Weiss; RTG: NASA / CXC / Univ. Florence / G.Risaliti & E.Lusso

Using data from approximately 1,600 quasars and a new method of determining their distances, they have found a strong deal with the results of the quasars supernova of the last 10 billion years: dark energy is real, about two-thirds of the energy in space, and it seems to be the cosmological constant in nature .

But they also found distant quasars that showed something unexpected: at the longest distance there is a deviation of "constant" behavior. Risaliti he wrote a blog post here, detailing the implications of his work, including this jewel:

Our ultimate Hubble diagram gave us utterly unexpected results: while our measurements of the expansion of the universe were in line with supernovae within a common range (from 4.3 billion years to the present day), the inclusion of distant quasars shows a strong deviation from the expectation of a standard cosmological model! If we explain this deviation with the dark energy component, we find that its density has to increase over time.

The relationship between the distance module (y-axis, distance measure) and red shift (x-axis), along with the quasar data, yellow and blue, with supernovae data in azure. The red points are the averages of the yellow quasi-points that are joined together. While the data on the supernovae and the quasar match each other, if both are present (up to a red shift of 1.5 or so), the quasar data goes much further, indicating a deviation from a constant interpretation.G. Risaliti and E. Lusso, author: 1811.02590

It's a notoriously difficult measurement you think, and the first thing you might think is that the quasars we've measured can be unreliable as a standard candle.

If it was your thought: congratulations! This is something that happened earlier when people tried to use gamma flashes as an indicator of distance to cross the limits of what the supernova would teach us. As we learned more about the explosions, we found them to be truly substandard, as well as revealing our own prejudices that could detect types of explosions. One & nbsp; or both of these two types of prejudices are likely to play at least here and this will generally be considered the most likely explanation for this result.

Even if it finds out why it will be an educational effort and a challenge, this evidence is unlikely that many people will convinced that dark energy is not, after all, a constant.

The expected destiny of the universe is an eternal, accelerating expansion, corresponding to w, the quantity on the y axis, exactly -1. If w is more negative than -1, as some data prefer, our fate will instead be Big Rip.C. Hikage et al., ArXiv: 1809.09148

But what if this new study is right? What if dark energy is not constant? What if, as other opinions have done over the past two decades, does it change with time?

The chart above shows results from several different datasets, but what I want to pay attention to is the value & nbsp;w, displayed on the y axis. What we say & nbsp;w is the dark energy equation where & nbsp;w & nbsp;= -1 is the value we get for the fact that dark energy is a cosmological constant: an invariant form of energy inherent in space itself. If & nbsp;w differs from -1, but it could change everything.

Different ways in which dark energy could evolve into the future. The remaining constant or increasing force (into the big Rip) could potentially rejuvenate the Universe, while the sign of reversion could lead to a large Crunchu.NASA / CXC / M.Weiss

Our standard destiny, where & nbsp;w = -1, will cause the universe to expand forever, and the structures that are not bound today are separated by the effects of dark energy. But if & nbsp;w either changes with time or is uneven to -1, all these changes.

  • If & nbsp;w is less negative than -1 (e.g., -0.9 or -0.75), dark energy diminishes over time, and eventually becomes unimportant. If & nbsp;w& nbsp; grows with time and sometimes becomes positive, it can cause the universe to find itself again in the Great Crunch.
  • However, if this new result is true, & nbsp;w is worse than -1 (e.g., -1.2 or -1.5 or worse) then dark energy will be more time-consuming, which will cause the fabric of the space to expand at an accelerated rate. Bound structures, such as galaxies, solar systems, planets, and even the atoms themselves, will separate for a sufficient period of time. The universe ends in a disaster known as Big Rip.

The Big Rip scenario occurs if we find that dark energy increases in strength while remaining negative in the direction over time.Jeremy Teaford / Vanderbilt University

The quest for understanding the ultimate fate of the universe is fascinating humanity since the dawn of time. With the advent of General Relativity and modern astrophysics, it was suddenly possible to answer this question from a scientific point of view. Is the universe expanding forever? Recollapse? Oscillate? Or will you break from the very physics that is the basis of our reality?

The answer can be determined by looking at objects within the Universe itself. But the key to revealing our ultimate cosmic destiny depends on understanding what we are looking at and that our answers are not predetermined by the assumptions we make about the objects we measure and observe. Dark energy may not be constant after all, and only when we look at the Universe itself, we will surely be certain.

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The most distant ray of space in the universe, from the quasar GB 1428, helps to show how bright 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.RTG: NASA / CXC / NRC / C. Cheung et al; Optical: NASA / STScI; Radio: NSF / NRAO / VLA

For the past generation, we realized that our universe is a particularly dark place. Sure, it is filled with stars, galaxies and a ubiquitous light-emitting phenomenon. But each of the known processes that create light is based on parts of the standard model: normal matter in our universe. All normal substances are – protons, neutron electrons, neutrinos, etc. – represent only 5% of what is out there.

Another 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, in any known way, relate to light or normal matter. And the remaining 68% is dark energy, which appears to be a form of energy inherent in the universe. The new set of observations is challenging for what we are currently thinking about dark energy. If it stops, everything we know will change.

Without the dark energy the universe would not be accelerated. But to explain distant supernovae, we see, among other things, that dark energy (or something that mimics it exactly) is necessary.NASA and ESA, about possible models of the expanding universe

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

In particular, by measuring what is the speed of expansion today, and how the extent of enlargement has changed throughout our cosmic history, we can use these familiar relationships to reconstruct what the universe must be composed of. From the full set of available data, including information from supernovae, the vast structure of space and cosmic microwave radiation, we were able to create a contrasting image: 5% of normal mass, 27% of dark matter, and 68% of dark energy.

Dark energy limitations from three independent sources: the supernovae, the cosmic microwave background (CMB), and baryon acoustic oscillations (BAOs) located in the great cosmic structure of the universe. Note that even without supernova we would need dark energy. There are other current versions of this chart, but the results are largely unchanged.Supernova Cosmology Project, Amanullah et al., Ap.J. (2010)

To our best knowledge, dark matter acts as a normal matter from a gravitational point of view. The total mass of the dark matter is solid, so as the universe expands and the volume increases, the density of the dark matter decreases, just as with the normal mass.

Dark energy, however, seems to be different. Rather than particle type, it seems to behave as if it were the kind of energy that is inherent in space itself. As the space expands, the dark energy density remains constant, rather than falling or growing. As a result, after the long expansion of the universe, dark energy dominates the energy budget of the Universe. Over time, it gradually becomes more dominant than other components, leading to the accelerated expansion we see today.

While matter (normal and dark) and radiation are less dense, as the universe expands due to the increasing volume, dark energy is the form of energy that is inherent in space itself. When a new space is created in the expanding universe, the density of dark energy remains constant.E. Siegel / Beyond the Galaxy

Traditional space expansion measurement techniques were based on one of two observable indicators.

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

Problems with one of these techniques – the sort of thing that night astronomers keep in mind – is afraid that our assumptions about internal behavior may be mistaken, which is why our conclusions are contradictory.

Two of the most successful methods of measuring large cosmic distances are based either on their apparent brightness (L) or on their seemingly angularly large (R) sizes that are directly observable. If we can understand the internal physical properties of these objects, we can use them either as standard candles (L) or as standard rulers (R) to see how the universe has spread and, therefore, what it is made of, over its space history.NASA / JPL-Caltech

So far our best standard candles have led us very far into the history of the universe: the light that was launched when the universe was approximately 4 billion years old. Since we live nearly 14 billion years ago, we are able to measure extremely far, with type Ia supernovae, which provide the most reliable and robust distance indicator for dark energy.

Recently, however, a team of scientists began to use x-ray emission quasars, which are much clearer, and therefore visible in earlier times: when the universe was only a billion years old. In interesting newspaper work, scientists Guido Risaliti and Elisabeth Lusso use quasars as a standard candle to go further than we have ever measured the nature of dark energy. What they find is still preliminary, but still overwhelming.

A new study using Chandra, XMM-Newton and Sloan Digital Sky Survey (SDSS) suggests that dark energy may change in space. This artist's explanation explains how astronomers watched the effects of dark energy for about one billion years after the Big Bang, with a distance of almost 1600 quasars and fast-growing black holes that shine very clearly. Two of the farthest studied quasars are depicted in Chandra images in the inserts.Illustration: NASA / CXC / M.Weiss; RTG: NASA / CXC / Univ. from Florence / G.Risaliti & E.Lusso

Using data from approximately 1,600 quasars and a new method of determining their distances, they have found a strong deal with the results of the quasars supernova of the last 10 billion years: dark energy is real, about two-thirds of the energy in space, and it seems to be the cosmological constant in nature .

But they found even more distant quasars that showed something unexpected: at the greatest distance there is a deviation from this "constant" behavior. Risaliti wrote a blog post that describes the implications of his work, including this jewel:

Our ultimate Hubble diagram gave us utterly unexpected results: while our measurements of the expansion of the universe were in line with supernovae within a common range (from 4.3 billion years to the present day), the inclusion of distant quasars shows a strong deviation from the expectation of a standard cosmological model! If we explain this deviation with the dark energy component, we find that its density has to increase over time.

The relationship between the distance module (y-axis, distance measure) and red shift (x-axis), along with the quasar data, yellow and blue, with supernovae data in azure. The red points are the averages of the yellow quasi-points that are joined together. While the data on the supernovae and the quasar match each other, if both are present (up to a red shift of 1.5 or so), the quasar data goes much further, indicating a deviation from a constant interpretation.G. Risaliti and E. Lusso, author: 1811.02590

It's a notoriously difficult measurement you think, and the first thing you might think is that the quasars we've measured can be unreliable as a standard candle.

If it was your thought: congratulations! This is something that happened earlier when people tried to use gamma flashes as an indicator of distance to cross the limits of what the supernova would teach us. As we learned more about the explosions, we found them to be truly substandard, as well as revealing our own prejudices that could detect types of explosions. One or both of these two types of prejudice probably play at least here, and this is generally considered to be the most likely explanation of this result.

Even if it finds out why it will be an educational effort and a challenge, this evidence is unlikely that many people will convinced that dark energy is not, after all, a constant.

The expected destiny of the universe is an eternal, accelerating expansion, corresponding to w, the quantity on the y axis, exactly -1. If w is more negative than -1, as some data prefer, our fate will instead be Big Rip.C. Hikage et al., ArXiv: 1809.09148

But what if this new study is right? What if dark energy is not constant? What if, as other opinions have done over the past two decades, does it change with time?

The graph above shows the results from several different datasets, but I want you to pay attention is value w, displayed on the y axis. What we call w is the equation of the dark energy state, where w = -1 is the value we get for the fact that dark energy is a cosmological constant: an invariant form of energy inherent in space itself. If w differs from -1, but it could change everything.

Different ways in which dark energy could evolve into the future. The remaining constant or increasing force (into the big Rip) could potentially rejuvenate the Universe, while the sign of reversion could lead to a large Crunchu.NASA / CXC / M.Weiss

Our standard destiny where w = -1, will cause the universe to expand forever, and the structures that are not bound today are separated by the effects of dark energy. But if w either changes with time or is uneven to -1, all these changes.

  • If w is less negative than -1 (e.g., -0.9 or -0.75), dark energy diminishes over time, and eventually becomes unimportant. If w grows with time and sometimes becomes positive, it can cause the universe to find itself again in the Great Crunch.
  • However, if this new result is true, a w is worse than -1 (e.g., -1.2 or -1.5 or worse) then dark energy will be more time-consuming, which will cause the fabric of the space to expand at an accelerated rate. Bound structures, such as galaxies, solar systems, planets, and even the atoms themselves, will separate for a sufficient period of time. The universe ends in a disaster known as Big Rip.

The Big Rip scenario occurs if we find that dark energy increases in strength while remaining negative in the direction over time.Jeremy Teaford / Vanderbilt University

The quest for the ultimate fate of the universe is fascinating humanity since the dawn of time. With the advent of General Relativity and modern astrophysics, it was suddenly possible to answer this question from a scientific point of view. Is the universe expanding forever? Recollapse? Oscillate? Or will you break from the very physics that is the basis of our reality?

The answer can be determined by looking at objects within the Universe itself. But the key to revealing our ultimate cosmic destiny depends on understanding what we are looking at and that our answers are not predetermined by the assumptions we make about the objects we measure and observe. Dark energy may not be constant after all, and only when we look at the Universe itself, we will surely be certain.


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