The Universe
The Earth's magnetic poles flip every few hundred thousand years. The last flip was some 780,000 years ago (i.e., we are overdue), and an anomaly that precedes and accompanies the magnetic pole flip is occurring now. "When the field flips it also tends to become very weak. What currently has geophysicists...abuzz is the realization that the strength of Earth’s magnetic field has been decreasing for the last 160 years at an alarming rate. " (The Conversation, Feb 17, 2017) The flip does not happen in an instant - it takes 1,000 to 10,000 years to complete.
"Just before a reversal, the extreme weakening of our magnetic field, the shield that protects us from charged particles constantly blasting the atmosphere, could cause trouble. Live Science previously reported these charged solar particles could punch holes in Earth's atmosphere akin to the ozone hole above Antarctica. Whether those holes would have any true impact is debatable, scientists have said. The increased radiation, however, could mess with the navigation of satellites and aircraft as well as electrical power grids." (LiveScience)
So, although we may not be in for a doomsday scenario, when the flip occurs, there will be some effects.
"The second full moon of January passed through Earth's shadow in a Super Blue Blood Moon eclipse today (Jan. 31), a rare lunar sight visible to millions of observers around the world. Today's lunar eclipse was the first to coincide with a Blue Moon – a second full moon in one month – in North America in over 150 years. It was also the second "supermoon" of 2018, with the moon appearing slightly bigger and brighter than usual due to its closeness to Earth. And to top it off, the supermoon passed through Earth's shadow this morning, casting a reddish hue on the lunar surface for more than 4 hours." [Space.com, January 31]
Photo is from Space.com article. Astrophotographer James Jordan captured this view of the Super Blue Blood Moon at totality from Oakland, California. Credit: James Jordan
Signal detected from 'cosmic dawn'
POSTED MARCH 18, 2018
Using a radio telescope in the Australian outback, scientists have detected the "fingerprint" of light from the first stars dating back to just 180 million years after the Big Bang.
"Scientists say they have observed a signature on the sky from the very first stars to shine in the Universe. They did it with the aid of a small radio telescope in the Australian outback that was tuned to detect the earliest ever evidence for hydrogen. This hydrogen was in a state that could only be explained if it had been touched by the intense light of stars. The team puts the time of this interaction at a mere 180 million years after the Big Bang. Given that the cosmos is roughly 13.8 billion years old, it means the first stars lit up a full nine billion years before even our own Sun flickered into life. Dr Judd Bowman of Arizona State University, US, is the lead author on the scholarly paper describing the observation in the journal Nature.
"The...observation may [also] be the first hint that ...interactions [of ordinary matter with dark matter] are possible and the news therefore is likely to galvanise efforts to make the first detections of dark matter particles. "
(BBC, 2/28/2018)
Murchison Australia radio spectrometer (CSIRO Australia)
'Tunguska'-Size Asteroid Makes Surprise Flyby of Earth
POSTED APRIL 18, 2018
An asteroid similar in size to one that exploded more than 100 years ago in Russia's Tunguska region in Siberia gave Earth a close shave on Sunday (April 15), just one day after astronomers discovered the object. The near Earth object was estimated to be more than 3 times larger than the asteroid that crashed in and leveled 500,000 acres of forest in Siberia in 1908. Its closest approach to Earth was about half the average distance from the Earth to the moon.
NASA has a video, "Keeping an Eye on Space Rocks," that explains near Earth objects and how and why scientists are tracking them.
The Kilauea Eruption
POSTED 5/29/2018
The devastating power of a volcanic eruption has been on full display over the past weeks. Kilauea is the biggest and most active of the island of Hawaii’s five volcanoes and is one of the most active volcanoes in the world. Located on the southern shore of Hawaii’s "Big Island" Kilauea has been erupting consistently since 1983 after a period of being dormant. The volcano is now in its fourth week of eruptions and the effects are spreading far from Hawaii. Haze from the Kilauea volcano eruption in Hawaii blanketed the Marshall Islands 3,700 kilometres (2,300 miles) away on Sunday (May 27), as officials warned it would continue moving west. The haze, a phenomenon known as "vog" or volcanic smog, "is spreading across Micronesia," the US National Weather Service based in Guam said.
Closer to the eruption site, Kilauea's lava is "creating more Hawaii" as it flows to the Pacific.
"Lava is reaching the ocean and building land while producing spectacular plumes of steam. These eruptions are hugely important for the creation of new land. But they are also dangerous. Where the lava meets the ocean, corrosive acid mist is produced and glass particles are shattered and flung into the air. Volcanic explosions can also hurl lava blocks hundreds of meters and produce waves of scalding hot water.
"At Kīlauea, lava is erupting from a line of vents on the volcano’s flanks, and is moving downslope to the edge of the island, where it enters the ocean. This is a process that has been witnessed many times at Hawai’i and other volcanic islands. And it is through many thousands of such eruptions that volcanic islands like Hawai’i form."(Popular Science, May 24)
Photo is from EPA and appears in the May 24 Popular Science article.
What kept early galaxies from blowing themselves apart?
POSTED SEPTEMBER 12, 2018
(Science Daily): For the first time, a powerful "wind" of molecules has been detected in a galaxy located 12 billion light-years away. Probing a time when the universe was less than 10 percent of its current age, University of Texas at Austin astronomer Justin Spilker's research sheds light on how the earliest galaxies regulated the birth of stars to keep from blowing themselves apart. "Galaxies are complicated, messy beasts, and we think outflows and winds are critical pieces to how they form and evolve, regulating their ability to grow," Spilker said.
Some galaxies such as the Milky Way and Andromeda have relatively slow and measured rates of starbirth, with about one new star igniting each year. Other galaxies, known as starburst galaxies, forge hundreds or even thousands of stars each year. This furious pace, however, cannot be maintained indefinitely.
To avoid burning out in a short-lived blaze of glory, some galaxies throttle back their runaway starbirth by ejecting -- at least temporarily -- vast stores of gas into their expansive halos, where the gas either escapes entirely or slowly rains back in on the galaxy, triggering future bursts of star formation.
Until now, however, astronomers have been unable to directly observe these powerful outflows in the very early universe, where such mechanisms are essential to prevent galaxies from growing too big, too fast.
Spilker's observations with the Atacama Large Millimeter/submillimeter Array (ALMA), show -- for the first time -- a powerful galactic wind of molecules in a galaxy seen when the universe was only 1 billion years old. This result provides insights into how certain galaxies in the early universe were able to self-regulate their growth so they could continue forming stars across cosmic time.
Right: Artist impression of an outflow of molecular gas from an active star-forming galaxy.
Credit: NRAO/AUI/NSF, D. Berry
Cosmic mysteries: the search for dark matter and dark energy
POSTED OCTOBER 4, 2018
Image is from the phys.org article
The distribution of dark matter (colored in blue) in six galaxy clusters, mapped from the visible-light images from the Hubble Space Telescope. (Source: NASA, ESA, STScI, and CXC) Credit: NASA, ESA, STScI, and CXC
It's a great time to be alive. Year by year, decade by decade, our understanding of the fundamental structure of the universe increases. Progress was so great during the twentieth century that it led some writers to suggest that we were in the twilight of the scientific age - that we were approaching an "end of science," a knowledge limit beyond which we could learn nothing more.
Then, in the 1990's, astrophysicists observed something surprising. The universe was expanding at an accelerating rate with time. First proposed by Edwin Hubble in 1929 based on his observations of the red shift of distant galaxies, the expanding universe was an established theory in astrophysics. But until the observations of the '90's, this expansion was thought to be slowing down - even to the point that it may reverse itself and the universe might end in a Big Crunch.
Another question that puzzled scientists was why galaxies did not fly apart instead of rotating as they do - indeed, why they formed in the first place. The visible matter in many galaxies does not seem to be enough to hold them together, nor does it explain why they move as they do.
These were just two of many observations and discoveries that made us realize that the universe still held mysteries to be uncovered and understood,
The dominant theory to explain these observations is that of dark energy and dark matter. In the case of the accelerating expansion of our universe, "dark energy", a theoretical repulsive force counteracts gravity and causes the universe to expand at an accelerating rate. In the case of galaxy formation and rotation, "dark matter", a hypothetical form of matter, adds to the total mass of galaxies and causes the observed results.
Their names result from their property of not being visible. The visible universe—including Earth, the sun, other stars, and galaxies—is made of protons, neutrons, and electrons bundled together into atoms. The surprising discoveries of the late 20th century were that "this ordinary, or baryonic, matter makes up less than 5 percent of the mass of the universe. The rest of the universe appears to be made of a mysterious, invisible substance called dark matter (25 percent) and a force that repels gravity known as dark energy (70 percent)." (National Geographic)
The questions scientists are wrestling with now are "What is dark matter?" and "What is dark energy?"
Another one, for me at least, is "What caused dark energy to become dominant 7.5 billion years ago?" (see graphic below) Perhaps after 7.5 billion years, the effect of the expansion due to the Big Bang became less important.
Detecting and identifying these exotic forms of matter and energy are prodigious tasks. Dark energy and dark matter, by definition, cannot be detected in our visible universe. We observe them indirectly through their effects. Scientists have devised experiments to try to answer these questions.
The search for dark energy
The search for dark energy is centered around the HETDEX project (Hobby-Eberly Telescope Dark Energy Experiment). "Since scientists don't know what dark energy is, though, they aren't searching for it directly ... Instead, they will study its effect: the accelerating expansion of the universe, which has provided much of the evidence of dark energy's existence. The way in which the universe is accelerating, and changes in the acceleration over time, will help scientists whittle down the list of possible explanations, and may even provide the answer." (HETDEX.org)
he HETDEX studies will probe the universe at different times, from a few hundred thousand years after the Big Bang to the modern epoch, providing a complete picture of how the acceleration has changed over the eons. The searches will use three basic techniques:
Exploding Stars: Plot the distances and velocities of the exploding stars known as supernovae.
Sound Waves: Look at the way galaxies are distributed in the early universe to find patterns imprinted in the Big Bang.
Distortions: Probe the "clumpiness" of the universe at different epochs by studying the shapes of millions of galaxies.
The search for dark matter
As for dark matter, scientists are exploring several possibilities. NatGeo notes: "One leading hypothesis is that dark matter consists of exotic particles that don't interact with normal matter or light but that still exert a gravitational pull. Several scientific groups, including one at CERN's Large Hadron Collider, are currently working to generate dark matter particles for study in the lab. Other scientists think the effects of dark matter could be explained by fundamentally modifying our theories of gravity. According to such ideas, there are multiple forms of gravity, and the large-scale gravity governing galaxies differs from the gravity to which we are accustomed."
There are other smaller-scale efforts underway to detect dark matter. One uses neutrinos, the almost mass-less elementary particle to detect dark matter by studying the neutrino's interaction with "weakly interacting massive particles." (video below) WIMPs are one of the leading candidates for dark matter.
Another candidate for dark matter is a hypothetical subatomic particle, the axion, that may comprise "cold" dark matter. Recent results from the Axion Dark Matter Experiment (ADMX) at the University of Washington suggest that it is now well-tuned enough to detect axions, a theoretical low-mass particle that many physicists believe may account for dark matter. (Vice Motherboard, Apr 10) Scientists at the Henryk Niewodniczanski Institute of Nuclear Physics Polish Academy of Sciences have analyzed ultracold neutrons and determined constraints on the properties of axions. (phys.org, "The search for dark matter—axions have ever-fewer places to hide")
"If we don’t find axions or WIMPs, there’s another back-up: sterile neutrinos. These are theoretical particles supposed to interact only via gravity as opposed to ‘normal’ neutrinos that interact – very weakly – with normal matter....The Japanese space agency, JAXA, together with NASA, sent its Hitomi satellite into orbit on February 17, 2016, carrying what they hoped would be just the right type of spectrometer. Except it didn’t stay there long – having made some initial observations of the Perseus cluster, Hitomi suddenly died three weeks later, breaking up into five pieces." The team has already cobbled together a replacement. XRISM should be launched between April 2020 and March 2021, on a JAXA H-IIA rocket from the Tanagashima Space Centre, following the path of Hitomi. (Wired UK, Sep 28)
The most revolutionary thinking on the composition of dark matter informs the research planned to start at the National Institute of Nuclear Physics at Rome in the coming days. Scientists there plan to search for a fifth* basic force of nature - a "dark force", which "would shape the behavior of the so far unknown particles that constitute dark matter, and could potentially exert the most subtle effects on the forces we are more familiar with." (The Guardian, Sep 3)
*"Physicists, to date, know of only four basic forces of nature. The electromagnetic force allows for vision and mobile phone calls... Without the so-called strong force, the innards of atoms would fall apart. The weak force operates in radiation, and gravity – the most pervasive of nature's forces."
By Ann Feild (STScI) - http://hubblesite.org/newscenter/archive/releases/2001/09/image/g/
Supernova 1987A time lapse created by University of Toronto grad student
POSTED NOV 2, 2018
Supernovae occur in the deaths of massive stars about once every 50 years in the Milky Way and once per second in the universe as a whole. They can briefly outshine entire galaxies and radiate more energy than our sun will in its entire lifetime. They're also the primary source of heavy elements in the universe. During a supernova, the dying star releases very large amounts of energy as well as neutrons, which allows elements heavier than iron, such as uranium and gold, to be produced. In the supernova explosion, all of these elements are expelled out into space to form the building blocks of the universe and ourselves. As Carl Sagan observed, "We are made of star stuff."
"Since it first appeared in the southern night sky on February 24th 1987, Supernova 1987A has been one of the most studied objects in the history of astronomy. The supernova was the cataclysmic death of a blue supergiant star, some 168,000 light-years from Earth, in the Large Magellanic Cloud, a satellite galaxy of our own Milky Way Galaxy. It was the brightest supernova to appear in our skies since Kepler's Supernova in 1604 and the first since the invention of the telescope.
"The brilliant new star was first spotted by two astronomers working at the Las Campanas Observatory in northern Chile the night of the 24th...Now, Yvette Cendes, a graduate student with the University of Toronto and the Leiden Observatory, has created a time-lapse showing the aftermath of the supernova over a 25-year period, from 1992 to 2017. The images show the shockwave expanding outward and slamming into debris that ringed the original star before its demise." - Science Daily (link left)
More on supernovae and the elements:
What Is a Supernova? How elements are formed
Japan finds huge cache of "rare earth" elements
POSTED JANUARY 6, 2019
Rare earth elements play an enormous role in our present-day technologies. Rare earths are used almost everywhere - from headsets and TV's to energy saving lights to cancer treatments. Japan's recent find of these elements beneath their coastal waters will allow it to supplant China as the leading supplier of these valuable materials.
According to the Rare Earth Technology Alliance, due to the "unique magnetic, luminescent, and electrochemical properties, these elements help make many technologies perform with reduced weight, reduced emissions, and energy consumption; or give them greater efficiency, performance, miniaturization, speed, durability, and thermal stability."
The link below left is to The Big Think article, "Japan finds a huge cache of scarce rare-earth minerals ." Click on it to read the story of Japan's find and its upcoming extraction challenges as well as the complete mind-boggling list of uses of these important elements.
Partial listing of rare earths and their uses
Scandium or Sc (21) — TVs and energy-saving lamps.
Yttrium or Y (39) — cancer drugs, rheumatoid arthritis medications, and surgical supplies; superconductors and lasers.
Lanthanum or La (57) — Lanthanum finds use in camera/telescope lenses, special optical glasses, and infrared absorbing glass.
Cerium or Ce (58) — Cerium is found in catalytic converters, and is used for precision glass-polishing. It's also found in alloys, magnets, electrodes, and carbon-arc lighting.
Praseodymium or Pr (59) — This is used in magnets and high-strength metals.
Neodymium or Nd (60) — Many of the magnets around you have neodymium in them: speakers and headphones, microphones, computer storage, and magnets in your car. The mineral is especially important for green tech batteries (for electric cars and wind turbines).
"Why Does the World Exist?" Redux
POSTED JULY 22, 2019
In an earlier post on the Mind & Spirit page, there's a discussion of what William James called the darkest question in all philosophy: “Why is there something rather than nothing?” Here we'll examine one element of why the world exists in light of scientific theories, rather than philosophical thought.
In the symmetrical early universe of the Big Bang, the creation of particles should be equal to the creation of antiparticles. Every antiparticle (e.g., antiproton) would annihilate its equivalent particle (e.g., proton) when they encountered each other. Matter would never be able to exist and thus never able to form stars, galaxies, or ourselves.
So, how did the amount of matter come to exceed the amount of anti-matter in the early universe and give us the matter-filled universe where we exist?
A graphic of the stages of the expansion of the universe after the Big Bang is given below left. An exponential expansion of the universe occurred 10−36 seconds after the Big Bang singularity to ~ 10−32 seconds after it. This period is called the inflationary epoch [see video "What was cosmic inflation?" below left] Quantum fluctuations are theorized to have created ripples in the fabric of space-time which were amplified and formed the "seed" of the currently observed structure of the universe.
But how was the symmetry of the Big Bang singularity "broken" so that matter would not be destroyed by anti-matter?
The Soviet physicist Andrei Sakharov (below) proposed a set of three necessary conditions that a baryon-generating interaction must satisfy to produce matter and antimatter at different rates. Sakharov showed that the Universe can initially start off with exactly the same amount of matter and antimatter, but then develop into a state that which has more of one than the other if three conditions are satisfied. The three early universe symmetries that would have to be violated are: baryon number production, charge-parity (CP), and thermal equilibrium (with the cosmic background radiation).*
Most models propose that this symmetry-breaking occurred after the inflationary period. Stephon Alexander's theory, presented his book, "The Jazz of Physics," is that it occurred during inflation and that it involves the discovery that the inflation field resonates the matter-interacting gravitational waves with much greater amplitude than the anti-matter-interacting gravitational waves. He writes:
"In most inflationary models, two types of gravitational waves are produced, one that spins** in a left-hand manner and one that spins in a right-hand manner...left-handed gravitational waves interact uniquely with matter, right-handed with antimatter...
"[Alexander's team discovery] was that during inflation, the inflation field resonates a left gravitational wave with much greater amplitude than a right-handed wave...The greater amplitude resulted in the resonance of matter over anti-matter and satisfied the Sakharov condition...
"This situation created a simultaneous condition of CP violation and baryon number production from the production of gravitational waves - satisfying two of the three Sakharov conditions from the same agent, the inflation....The last Sakharov condition - out of equilibrium - occurred naturally because during inflation space was expanding much faster than baryons were being created."
As he approached his 75th birthday, Steven Hawking said, "It's been an extraordinary time to be alive and working in the field of cosmology." Cosmology tries to answer some of the deepest questions humankind can ask. The discovery of the cosmic microwave background radiation in 1964 cemented the Big Bang Theory as the dominant explanation for the universe's origin. Developments since then have helped us better understand the aftermath of the big bang, how matter won out over antimatter, and how the universe has expanded at varying rates over the course of its 13 plus billion year history. (See cosmology timeline below right for some of the theories and discoveries discussed in this post.)
*For more details on the Sakharov conditions, see the Wikipedia entry for baryon asymmetry.
**Spin is a property of elementary particles related to the magnetic field generated as the particle moves.
Glossary
Baryon - a subatomic particle that has a mass equal to or greater than a proton
Big Bang Theory - the universe started with an infinitely small, infinitely dense, gravitational singularity containing all the mass and space-time of the Universe which then expanded over the next 13.77 billion years to the cosmos of today. (Graphic left)
Cosmic Inflation, or inflation - theory of exponential expansion of space in the early universe. The inflationary epoch lasted from 10−36 seconds after the conjectured Big Bang singularity to some time between 10−33 and 10−32 seconds after the singularity. Following the inflationary period, the universe continues to expand, but at a less rapid rate
Gravitational waves are disturbances in the curvature of spacetime, generated by accelerated masses, that propagate as waves outward from their source at the speed of light. These 'ripples' in space-time are caused by some of the most violent and energetic processes in the Universe. Albert Einstein predicted the existence of gravitational waves in 1916 in his general theory of relativity. Einstein's mathematics showed that massive accelerating objects would disrupt space-time in such a way that 'waves' of distorted space would radiate from the source (like the movement of waves away from a stone thrown into a pond).
A quantum fluctuation is the temporary change in the amount of energy in a point in space, as explained in Heisenberg's uncertainty principle. This allows the creation of particle-antiparticle pairs of virtual particles. Quantum fluctuations may have been necessary in the origin of the structure of the universe: according to the model of expansive inflation the ones that existed when inflation began were amplified and formed the seed of all current observed structure.
Left: Andrei Sakharov was "one of the main players in the Russian nuclear arms program.. often called the father of the Soviet hydrogen bomb. But he later renounced the proliferation of nuclear arms and became an international voice of pacifism and defender of human rights in the Soviet Union, earning him the [1975] Nobel Peace Prize." - Stephon Alexander, The Jazz of Physics
Sakharov was not allowed to leave the Soviet Union to collect the prize. His wife Yelena Bonner read his speech at the ceremony in Oslo, Norway. Titled "Peace, Progress, Human Rights", Sakharov called for an end to the arms race, greater respect for the environment, international cooperation, and universal respect for human rights. He included a list of prisoners of conscience and political prisoners in the USSR, stating that he shares the prize with them. By 1976 the head of the KGB Yuri Andropov was prepared to call Sakharov "Domestic Enemy Number One". ..Sakharov was arrested on 22 January 1980, following his public protests against the Soviet intervention in Afghanistan in 1979, and was sent to the city of Gorky, now Nizhny Novgorod. Between 1980 and 1986, Sakharov was kept under Soviet police surveillance and their apartment in Gorky was repeatedly subjected to searches and heists. (Wikipedia)
Cosmology Timeline
1964 - CMB radiation discovered
1967 - Sakharov's three conditions
1980 - Guth seminar on cosmic inflation
1998 - dark energy discovered; used to explain the current accelerating expansion of the universe
2001 - WMAP launched
2015 - first direct observation of gravitational waves
Dark energy and cosmic expansion
ORIGINALLY POSTED AS PART OF "Cosmic expansion (11 bya), complex life (3 bya), Ebola drugs (2019)" - Aug 15, 2019
"A trio of articles in the journal Nature provides us with encouraging news about both the quest to understand the nature of the universe and the attempt to halt a deadly disease. The resource-intensive multinational galaxy mapping, the 12 year effort by a group of dedicated biologists to isolate an "oddball" microbe, and a successful clinical trial in the midst of the second deadliest Ebola outbreak in history remind us of what humanity at its best can accomplish."
In the 1990's, astrophysicists observed something surprising. The universe is expanding at an accelerating rate with time. The expanding universe, first proposed by Edwin Hubble in 1929 based on his observations of the red shift of distant galaxies, was an established theory in astrophysics. But until the observations of the '90's, this expansion was thought to be slowing down because of the effect of gravity- even to the point that some scientists thought this expansion might reverse itself and the universe end in a Big Crunch.
In September, astronomers will begin a five year project to capture light spectra from 35 million galaxies and reconstruct the Universe’s history of expansion. Their main aim: to elucidate the nature of dark energy, the enigmatic force that is pushing the Universe to accelerate at an ever-faster pace. The DESI ( Dark Energy Spectroscopic Instrument) survey will reconstruct 11 billion years of cosmic history. It could answer the first and most basic question about dark energy: is it a uniform force across space and time, or has its strength evolved over eons? [below left: link to Nature article on DESI]
Image of cosmological red shift is from Socratic.org.
Light spectra and red shift
Astronomers use light spectra to determine the composition of stars. From the dark absorption lines and bands, they can determine the elemental composition of the star. The red shift - the absorption lines moving towards the red end of the spectrum -indicate an object is moving away from us because it has a longer wavelength.
The discoveries that won the 2019 Nobel Physics award
POSTED OCT 23, 2019
News Item: "Cosmologist James Peebles and astronomers Michel Mayor and Didier Queloz have won the 2019 Nobel Prize in Physics for discoveries about the evolution of the Universe and Earth’s place in it." (Nature, Oct 8)
James Peebles' award honored his life long work in theoretical physics that helped establish the foundation of our current understanding of the evolution of the Universe. Here are just three of his contributions:
CMB radiation, the "afterglow" of the Big Bang: While a young researcher at Princeton, at a time when the Big Bang had not yet been fully accepted, he was part of Professor Robert Dicke's team. The team was working on the theory that "if the universe was expanding, then it must have been much smaller, hotter and denser in the past. The prediction was that the thermal radiation from this epoch might still be observable today as background radiation pervading the universe." [2] When Penzias and Wilson, working at Bell Labs, came to Princeton to consult on some anomalous results, the Princeton group realized that this was indeed the afterglow of the Big Bang that they had predicted. In 1965, Peebles, Dicke and two colleagues "laid out the basic explanation of what the CMB is and how it relates to the Big Bang. They argued that the light had propagated through space almost since the beginning, growing fainter and less energetic over time as the expansion of space stretched it out. From the energy of these photons today, they could infer an early-universe temperature of more than 10 billion degrees Celsius." [1]
Dark matter: In 1966, Peebles made detailed calculations of the "abundances of different isotopes that would have been produced in this process...However, this CMB-based estimate differed from what astronomers have observed in the present-day universe. The discrepancy indicated that crucial ingredients might have been missing. As both theory and observation of the CMB improved, Peebles and other theorists grew confident that the early density of protons and neutrons paled next to that of a different kind of matter, now known as dark matter, that did not readily interact except through gravity." [1]
Structure of the universe: In the 1970s, he pioneered the theory of cosmic structure formation, which describes how the subtle hot spots and cold spots seen in the CMB evolved into the galaxies and voids in the present-day universe.
Michel Mayor's and Didier Queloz's award was for their pioneering work in the search for exoplanets. The search for planets outside our solar system had been stalled - with some beginning to doubt if we would ever find such planets. Then in 1995, Mayor and Queloz made the first discovery of a planet orbiting a star similar to our Sun. They detected the exoplanet through its tiny gravitational pull on its star, 51 Pegasi. Their discovery kicked off the field of exoplanets and their technique, which involved using a spectograph to study many stars at once, became standard in the pre-Kepler-telescope era. Currently more than 4000 exoplanets have been found. "They range from Earth-like rocks to Jupiter-dwarfing giants. Some have their own atmospheres. Others have water. Their numbers and variety have forced astronomers to rewrite the rules of how planets get made. Astronomers now estimate that planets outnumber stars — with hundreds of billions in our galaxy alone." [2]
For more on these discoveries and the men who made them, see the Quanta and Scroll In links below right and left, respectively.
[1] Quanta Magazine
[2] Scroll.in
The astronomers Michel Mayor and Didier Queloz won half of the prize for their 1995 discovery of a Jupiter-like planet orbiting a nearby star. The cosmologist James Peebles won the other half for work exploring the structure of the universe.
The past and future of the rings of Saturn
POSTED NOVEMBER 22, 2019
The rings of Saturn are the most stunningly beautiful sight in the solar system. First observed by Galileo in 1610, their true nature as rings detached from the planet was first deduced by the Dutch physicist Christiaan Huygens in the 1650's.
The Cassini*–Huygens space-research mission, commonly called Cassini, involved a collaboration between NASA, the European Space Agency, and the Italian Space Agency to send a probe to study the planet Saturn and its system, including its rings and natural satellites. Cassini was one of the most ambitious space exploration missions ever. Launched in 1997, the Cassini spacecraft ended its days in a blaze of glory in 2017 still collecting scientific data as it ran out of fuel. NASA describes the "Grand Finale" :
"After 20 years in space — 13 of those years exploring Saturn — Cassini exhausted its fuel supply. And so, to protect moons of Saturn that could have conditions suitable for life, Cassini was sent on a daring final mission that would seal its fate. After a series of nearly two dozen nail-biting dives between the planet and its icy rings, Cassini plunged into Saturn’s atmosphere on Sept. 15, 2017, returning science data to the very end."
Several of Cassini's discoveries are described in the sidebar, and a link to the NASA Cassini Mission web page is below right.
But the Cassini mission had at least one more surprise for scientists, and it has ignited a furious debate about the age of the rings. [see Quanta Magazine link below left]
Formerly, scientists believed the rings formed at the birth of the solar system - about 4.5 billion years ago. This summer, planetary scientists studying data from the "Grand Finale" argued, in a paper published in the journal Science, that the results of their work "show that Saturn's rings are substantially younger than the planet itself" - perhaps forming just 100 million years ago.
As skeptics pointed out the uncertainties in the approach taken and its conclusions, proponents of the younger age stand by their work, but "the debate is about more than the narrow question of the rings’ age. The age of Saturn’s rings will influence how we understand many of Saturn’s moons, including the potentially life-supporting world Enceladus, with its frozen ocean. And it will also push us closer to answering the ultimate question about Saturn’s rings, one that humans have wondered about since Galileo first marveled at them over 400 years ago: Where did they come from in the first place?" [Quanta, Nov 21]
While there is much to argue for and against the newly proposed age, the future of Saturn's rings is more certain. Observations from the Mauna Kea Observatory in Hawaii combined with data from the Cassini mission have led scientists to estimate that the rings will disappear completely in another 100 million years.
The Quanta article [link below left] concludes: "It appears that time is running out for Saturn’s rings, a 'symbol of astronomy,' [planetary scientist Aurélien] Crida said, one universally admired for its staggering beauty. Like many, he considers it fortunate that humanity and the rings coexist — giving us plenty of opportunity to argue about the secrets they hold."
*Giovanni Domenico Cassini was an Italian mathematician, astronomer and engineer. Known for his work in the fields of astronomy and engineering, Cassini discovered four satellites of the planet Saturn and noted the division of the rings of Saturn.
(A few of) Cassini's Greatest Hits
Saturn's polar hexagon and hurricane
Saturn has a hexagonal storm that rages continuously around its north pole. A consequence of fluid dynamics and Saturn's chaotic but rapidly-rotating atmosphere, this is the first such storm ever discovered on a gaseous world. Over 32,000 km (20,000 miles) wide, the storm starts at 78º latitude and extends down for some 100 km (60 miles). (Forbes)
Making icy moons look more habitable than ever
Cassini found evidence of subsurface oceans of liquid water on some of the moons, spotted geysers and other geologic activity, and even found indications of prebiotic chemistry. Based on Cassini's findings, scientists think the Saturn system is home to multiple moons that could be hospitable to life. The science revealed by Cassini will also help scientists search for life in other solar systems. (Space.com)
"Early-Earth-like" Titan, dynamic and active rings
ESA’s Huygens probe parachuted to Titan, making the first landing on a moon in the outer solar system
Found Saturn’s rings to be active and dynamic — a laboratory for how planets or moons form
Revealed Titan to have rain, rivers, lakes and seas; it is shrouded in a thick, nitrogen-rich atmosphere that might be similar to what Earth’s was like long ago (NASA)
A tale of science: the Milky Way's age
POSTED DECEMBER 7, 2019
This story illustrates elements of scientific discovery:
- An international team
37 scientists from 8 countries
- Creative thinking
Using astro-seismology to determine the age of stars
- Advanced technological capabilities
The Kepler telescope "was so sensitive it would have been able to detect the dimming of a car headlight as a flea walked across it."
- Serendipity
In 2013, however, Kepler "broke down, and NASA reprogrammed it to continue working on a reduced capacity." This allowed for a fresh analysis of data.
- A cautionary tale of computer modelling
The confusion from the original data (younger stars in the older portion of the Milky Way) was not a problem of data but of the modelling
Below: link to the Cosmos article
Why is the universe expanding faster now?
POSTED APRIL 29, 2020
When the American astronomer Edwin Hubble was studying the spectra of distant galaxies in the 1920's, he observed a red shift - a shift of the spectral lines towards longer red wavelengths - which could only be explained by these galaxies moving away from us. In 1929, he announced that almost all galaxies appeared to be moving away from us. In fact, he found that the universe itself was expanding with all of the galaxies moving away from each other. His estimate of the rate of expansion was considerably off, but his discovery of the expanding nature of the universe paved the way for the Big Bang Theory, the leading theory about how the universe began.
Since Hubble's discovery, scientists have been attempting to calculate the rate of the universe's expansion. Knowing the rate of expansion would, among other things, allow an estimation of the age of the universe. For many years, astronomers and others believed they knew the answer: the universe was expanding at a constant rate that indicated its age to be estimated as 13.8 billion years.
Then in 2016, NASA and the European Space Agency jointly announced that the universe is expanding up to 9% faster than predicted, a finding they reached after using the Hubble space telescope to measure the distance to stars in 19 galaxies "just" beyond the Milky Way. Based on observations of cosmic background radiation, the "Hubble constant" appeared to have a value of 73.4 kilometers per second per megaparsec. In 2018, another team using the Planck telescope to study the cosmic microwave background - the leftover radiation from the Big Bang - predicted a value of 67.4. Both teams have made increasingly accurate estimates, but the difference between the "local" team and the "Planck team" has not grown any smaller. In other words, the universe appears to be expanding faster now than it did in the early universe.
The question that scientists are grappling with is "Why?" And the reason this is important goes beyond estimating the age of the universe and its ultimate fate. The Standard Model of particle physics, which has successfully explained almost all experimental results and precisely predicted a wide variety of phenomena since the 1970's, may be missing something. The last time our concept of the basic building blocks of matter and energy was upset was in 1998 with the discovery of dark energy.
Quanta magazine discusses some of the current theories (link below right): "Because so little is known about [dark matter and dark energy], they are perhaps the obvious place to begin tampering with the standard model." The challenge is to change the standard model"without ruining the model’s perfect fit with a wealth of other astronomical observations."
Some of the "tampering" with the Standard Model considered in the Quanta article:
"A form of dark matter that decays into a lighter particle and a massless particle known as a dark photon. As more and more dark matter decayed over time, its gravitational pull would have lessened, and thus the expansion of the universe would have sped up."
"An extra dose of dark energy in the early universe, dubbed early dark energy, could reconcile the conflicting values of the Hubble constant."
"A modified-gravity model that was capable of behaving as if there were extra radiation in the early universe; the radiation pressure would have increased the cosmic expansion rate."
So much progress in understanding the universe had been made in the 20th century that, around 1980, Stephen Hawking, the great cosmologist, predicted the end of theoretical physics within 20 years. Around 2001, he amended his prediction to twenty years more from that year. If discoveries such as the varying rate of expansion of the universe are an indication, we may have several additional 20 year periods to go.
The Birth of a Planet
POSTED MAY 25, 2020
The leading theory for star and planet formation goes something like this: A disturbance - perhaps from a nearby supernova explosion or a passing star - causes a pressure change in the loose collection of interstellar gas and dust called a nebula. The nebular cloud of gas and dust collapses into a disc. The center of this disc sees a great increase in pressure and hydrogen atoms begin to come into contact. Eventually, they fuse and produce helium, starting the formation of a star. The newly formed star scoops up nearly all the material in the collapsing cloud. Gravity and other forces cause the remaining material within the disk to collide and clump together. In time, these small grains of dust continue to collide and grow from the width of a human hair to pebbles to mile-sized rocks to eventually planets. A video showing how the solar system might have formed is in the sidebar.
Scientists using the Very Large Telescope in Chile to observe AB Aurigae, a star located 520 light years from Earth, have found the first direct evidence of the birth of a planet. Vice [link below] describes their observation as "a baby picture like no other: A maelstrom of gas and dust swirling around what is likely a newborn giant planet. This stunning portrait is a composite that could be the first direct evidence of the hellacious site of a planet’s birth, according to a study published on Wednesday [May 20] in Astronomy & Astrophysics."
The Search for Life: Superhabitable Planets
POSTED OCTOBER 23, 2020
For centuries scientists, philosophers, and science fiction writers suspected that extrasolar planets existed, but there was no way of knowing whether they existed, how common they were, or how similar they might be to the planets of the Solar System. In the sixteenth century, the Italian philosopher Giordano Bruno, an early supporter of the Copernican theory that Earth and other planets orbit the Sun (heliocentrism), put forward the view that the fixed stars are similar to the Sun and are likewise accompanied by planets. In the eighteenth century, the same possibility was mentioned by Isaac Newton in his Principia. Making a comparison to the Sun's planets, he wrote "And if the fixed stars are the centres of similar systems, they will all be constructed according to a similar design and subject to the dominion of One." [1]
It wasn't until the late 20th century however that scientists had the tools to prove these early speculations correct. The first suspected scientific detection of an exoplanet, a planet outside the solar system, occurred in 1988. Shortly afterwards, the first confirmation of detection came in 1992, with the discovery of several terrestrial-mass planets orbiting a pulsar 2300 light years away.
The search for exoplanets took an exponential leap in 2009 with the launch of NASA's Kepler Space Telescope. Kepler was designed to survey a portion of Earth's region of the Milky Way to discover Earth-size exoplanets in or near habitable zones and estimate how many of the billions of stars in the Milky Way have such planets. Kepler used photometry to monitor the brightness of approximately 150,000 stars. These data were transmitted to Earth, then analyzed to detect periodic dimming caused by exoplanets that cross in front of their host star. During its over nine and a half years of service, Kepler observed 530,506 stars and detected 2,662 planets. [1]
When Kepler was retired after running out of fuel, TESS took its place. TESS launched April 18, 2018 aboard a SpaceX Falcon 9 rocket. NASA’s Transiting Exoplanet Survey Satellite (TESS) is an "all-sky" survey mission - covering a sky area 400 times larger than that monitored by Kepler. The stars TESS studies are 30 to 100 times brighter than those the Kepler mission surveyed, which will enable easier follow-up observations with both ground-based and space-based telescopes. [2]
As of October 22, 2020, Kepler and TESS had identified a total of 4296 exoplanets [link sidebar], many of the them in the habitable zone and many of them "Earth-like". A planet being in the habitable zone does not mean that life actually exists there, just that it has conditions that would allow life to exist.
It may also be possible that there are “superhabitable planets” in the cosmos where the chances for life to develop are even higher. In a recent analysis published in the journal Astrobiology, a research team led by astrobiologist Dirk Schulze-Makuch from the Technical University Berlin says we might have already detected 24 of them. The researchers propose that the search for extraterrestrial life “might be executed most effectively with a focus on superhabitable planets instead of Earth-like planets”. [3]
Schulze-Makuch’s team outlines several criteria that might help spot a superhabitable planet [4]:
A hot, humid planet could be more biologically productive, since Earth’s tropical regions contain its most biodiverse habitats.
Planets that are about 1.5 times as massive as Earth might be especially conducive to biodiversity because they would have more surface area, and would also be more likely to form a thick protective atmosphere.
A planet’s host star is another important factor in its habitability. Our Sun, a yellow dwarf star, may not be the most optimal type of star in superhabitability assessments because of its relatively short lifespan. The stellar sweet spot, according to Schulze-Makuch’s team, is the orange dwarf star. These stars are smaller than the Sun, larger than red dwarfs, and could live for 20 to 70 billion years, extending the timeline for life to emerge.
The team emphasized that data about exoplanets are still extremely limited: “Some of the astrophysical conditions that we identify as crucial for a planet to be potentially superhabitable are far from being observationally testable on planets outside the solar system.” Nevertheless, the new study offers a comprehensive roadmap for follow-up studies aimed at certain targets. Sophisticated new observatories, such as NASA’s James Webb Space Telescope, might eventually be able to pick out signs of life, known as biosignatures, in these worlds. [4]
[1] Wikipedia [2] NASA [3] Extreme Tech [4] VICE
Some definitions
Biosignature -any substance or phenomenon that provides scientific evidence of past or present life. Measurable attributes of life include its complex physical or chemical structures and the production of biomass and wastes.
Habitable zone - the area around a star where it is not too hot and not too cold for liquid water to exist on the surface of surrounding planets. Sometimes referred to as the "Goldilocks" zone. Life began in water on Earth and is a necessary ingredient for life as we know it.
Neutron star - the collapsed core of a massive supergiant star, which had a total mass of between 10 and 25 solar masses.
Photometry - the science of the measurement of light, in terms of its perceived brightness to the human eye
Pulsar - a neutron star that emits beams of radiation that sweep through Earth's line of sight. Like a black hole, it is an endpoint to stellar evolution. The "pulses" of high-energy radiation we see from a pulsar are due to a misalignment of the neutron star's rotation axis and its magnetic axis.
The Christmas Star makes a rare appearance
POSTED DECEMBER 20, 2020
If you look to the southwest near the horizon an hour after sunset on December 21st, you may be able to see the "Christmas Star". Jupiter and Saturn will put on a show that hasn't been seen in almost 800 years. Astronomers are calling it the Great Conjunction* of 2020. The two largest planets in our solar system will appear to almost merge in Earth’s night sky.
For centuries, scholars have speculated about what "The Star of Bethlehem" in the Gospel of Matthew might have been. Meteor, supernova, comet and planetary conjunction have all been put forward as possibilities. It is unlikely that the Star was a meteor, since meteors burn up in a matter of minutes. The only supernova that was visible from Earth around the time of Christ's birth actually happened in the year 185 A.D. and was recorded by Chinese astronomers . In the year 5 B.C., Chinese astronomers also noted the appearance of a “Broom Star” that many researchers have interpreted as a comet. In ancient times, though, comets were usually interpreted as bringers of bad news, not as the coming of the Messiah.
So that leaves us with planetary conjunctions. When the motion of the planets is rewound with observing software, astronomers found that several interesting conjunctions played out in the years around the life of Jesus. In the year 7 B.C., Jupiter and Saturn had three conjunctions in the same constellation, Pisces. So, if Jupiter and Saturn had three close conjunctions in a relatively brief period of time, it’s easy to imagine that ancient astronomers would have taken note, and they also likely would have ascribed some meaning to the event.
Whether a planetary conjunction explains the Star of Bethlehem or not, we will have a rare conjunction of Jupiter and Saturn in the hours just after sunset on the day of the winter solstice.
Lowell Observatory in Arizona will be live streaming the event starting at 5 pm MST/7 pm EST. Astronomy.com has a link to the live stream here.
*A conjunction happens when two celestial objects appear to pass close to one another as seen from Earth. The objects are actually many millions of miles apart but from Earth they appear next to one another. Conjunctions occur frequently but a conjunction of two bright planets like Jupiter and Saturn is rare.
Sources: The Star of Bethlehem: Can Science Explain What It Really Was? (astronomy.com) ; Jupiter and Saturn will form rare "Christmas Star" on winter solstice (astronomy.com)
Top Science Stories of 2020
POSTED DECEMBER 31, 2020
The global effort to understand and stop the novel coronavirus was, by far, the most important scientific effort this year. More than 1.8 million confirmed deaths have been reported. Vaccines have been developed in record time. Here in the US, racial, social and healthcare inequities led to a gross disparity in the mortality rates between whites and people of color.
Beyond the coronavirus, researchers made important discoveries and increased understanding of our world. Here are a few of them.
Despite the temporary downward blip caused by coronavirus lockdowns, climate change intensified. Though 2020’s emissions will drop by 4-7% as compared to 2019’s, atmospheric carbon dioxide levels will increase, the World Meteorological Organization found. Massive wildfires devastated forests in Australia, the Amazon, California and Colorado. The Atlantic hurricane season was the most severe ever recorded.
"NASA’s OSIRIS-REx and the Japan Space Agency’s Hayabusa2 space missions set out to sample rock, dirt, and debris from space rocks. On Oct. 20, the OSIRIS-REx probe successfully touched down on the surface of Bennu, a space rock about 200 million miles from Earth. On Dec. 8, the Hayabusa2 spacecraft returned a sample from Ryugu, an asteroid 180 million miles away, to Earth...Scientists suspect that when asteroids like Ryugu and Bennu pummeled a proto-Earth billions of years ago, they may have helped kick-start life by delivering the necessary building blocks." [1]
Three long-planned Mars missions got off the ground. The latest US rover, and orbiters designed by China and the United Arab Emirates launched in late July. The latest US rover Perseverance will do things no Mars rover has ever done — hunt for signs of life, collect samples for future return to Earth and deploy a miniature helicopter, to name a few. The UAE mission will focus on understanding Mars' weather and atmosphere while China's Tianen-1's scientific objectives include Mars' geology, surface soil and water-ice, ionosphere, electromagnetic fiels and surface climate.
75 years after the atomic bombing of Japan in August 1945, a new international treaty on the prohibition of nuclear weapons is on the table. The new agreement, the Treaty on the Prohibition of Nuclear Weapons (TPNW), is expected to become international law next year once 50 nations haqve signed it. The treaty would make it difficult for individuals (including scientists), as well as companies (including banks), from the treaty’s member countries to play any part in the development and deployment of nuclear-weapons technologies.
Researchers found that even the dendritic arms of neurons in the brain seem capable of processing information, which means that every neuron might be more like a small computer by itself. The analogy to computers is important for AI: "when artificial neural networks capable of “deep learning” tackle problems of perception, the ones that work best have organizational structures remarkably similar to those of the living brain. Both types of systems seem to converge on the same computational solutions, which may mean that deep networks could be increasingly useful tools for deciphering the brain’s secrets." [2]
New precise data from the ESA's Gaia spacecraft has confirmed that the universe is expanding faster than predicted by the standard model of cosmology. In a paper published earlier this month, a research team confirmed an expansion rate of 73.2 kilometers per second per megaparsec, in line with their previous value, but now with a margin of error of just 1.8%. That seemingly cements the discrepancy with the far lower rate of 67 obtained from the standard model of cosmology. [3] The faster than predicted expansion rate points to an unknown in the standard model, which has accurately predicted findings for decades. Astrophysicists are searching for answers as the so-called "Hubble crisis" worsens.
References: [1] PBS/NOVA [2] Quanta Magazine [3] Quanta Magazine
Below: links from PBS (left) and The Smithsonian (right).
What happened before the Big Bang?
POSTED JANUARY 26, 2021
About 13.8 billion years ago, an infinite concentration of energy in an infinitely small space exploded, and our universe of matter, energy, space and time began. The Big Bang Theory is the leading explanation about how it all started. At its simplest, it says the universe as we know it started with a small singularity, then inflated over the next 13.8 billion years to the cosmos that we know today. [sidebar]
For the first 10^-43 seconds of expansion, this density of energy was so extreme physics can't yet provide a clear description of what was happening. [1] Rewinding the expansion of the universe to the Big Bang singularity - this extremely small, massively dense speck of heat and energy - the laws of physics and time as we know them cease to function.
What happened before the Big Bang is speculative, but extrapolating from our current understanding of the universe and the mathematics that explains it, here are some of the theories.
Stephen Hawking's answer to the question "What was there before there was anything?" relies on a theory known as the "no-boundary proposal." Time as we understand it literally did not exist before the universe started to expand. Rather, the arrow of time shrinks infinitely as the universe becomes smaller and smaller, never reaching a clear starting point. Essentially "there was never a Big Bang that produced something from nothing. It just seemed that way from mankind's perspective." [2]
Cal Tech theoretical physicists Sean Carroll and Jennifer Chen have suggested that the universe as we know it is the offspring of a parent universe from which a bit of space-time has ripped off. It's like a radioactive nucleus decaying. "When a nucleus decays, it spits out an alpha or beta particle. The parent universe could do the same thing, except instead of particles, it spits out baby universes, perhaps infinitely. 'It's just a quantum fluctuation that lets it happen,' Carroll said. These baby universes are 'literally parallel universes' and don't interact with or influence one another." [3]
The universe was an "infinite stretch of an ultrahot, dense material, persisting in a steady state until, for some reason, the Big Bang occurred. This extra-dense universe may have been governed by quantum mechanics, the physics of the extremely small scale...The Big Bang, then, would have represented the moment that classical physics took over as the major driver of the universe's evolution." [3]
"Prior to the Big Bang, there was another universe, identical to this one but with entropy increasing toward the past instead of toward the future. Increasing entropy, or increasing disorder in a system, is essentially the arrow of time...so in this mirror universe, time would run opposite to time in the modern universe and our universe would be in the past" [3] [For more on entropy and the arrow of time see the Royal Institution's video in the sidebar]
The "Big Bounce" in which "our big bang" is just one in an infinitely long series of expansions and contractions. Developed from string theory [see sidebar] the "Big Bounce" proposes that this "cyclic universe goes about exactly as you might imagine, continually bouncing between big bangs and big crunches, potentially for eternity back in time and for eternity into the future." [4]
Theoretical physicist Brian Greene discusses these theories in an interview with Joe Rogan. [sidebar]
Cosmic mysteries: the multiverse
POSTED SEPTEMBER 9, 2021
Since the late 19th century, physicists and science wags have been predicting the imminent end of theoretical physics. Mankind would soon know all there is to know about the physical universe and need not look further. 150 years later, the end of physics is nowhere in sight. Like an infinitely-nesting Russian doll, as one mystery is resolved, another comes into view.
In the twentieth century, we learned that energy and matter were related and interchangeable, that gravity causes space to curve, that the universe exploded into existence from an infinitesimally small point, that the world of the very small was stranger than anything we could ever imagine, that 95% of the matter in our universe cannot be seen, that there exist points of infinite density where matter is swallowed and time stops. And on and on.
So much progress in understanding the universe had been made in the 20th century that, around 1980, Stephen Hawking, the great theoretical physicist and cosmologist, predicted the end of theoretical physics within 20 years. Around 2001, he amended his prediction to twenty years more. It looks like we will have several more 20 year cycles if the early 21st century is any indication.
In the first two decades of this century, we learned that the universe is expanding at faster and faster rates, discovered the Higgs boson - the so-called "God particle" that gives elementary particles their mass, found a supermassive black hole at the center of our Milky Way galaxy, identified the first room temperature superconductor, observed gravitational waves predicted by Einstein in 1916, and produced the first ever image of a black hole using a "telescope" the size of planet Earth.
The Event Horizon Telescope, a planet-scale array of eight ground-based radio telescopes forged through international collaboration, captured this image of the supermassive black hole in the center of the galaxy M87 and its shadow. (Image credit: EHT Collaboration) [4]
Still, mysteries remain...how does the Higgs boson give elementary particles different masses? what is causing the ever-increasing rate of expansion of the universe? do dark energy and dark matter obey the same laws of physics as "normal" matter? and what's up with the 1.8 billion-light-year-spanning "cold spot" in the constellation of Eridanus which looks like a giant bite taken out of the universe?
Speculation on the last item - the 1.8 billion light year supervoid in Eridanus is running rampant: "Could it be a blemish left by another universe bumping into our own? Might it be a portal into a region beyond the known universe? Or some sort of matter-destroying 'bubble'?"
Which brings us (finally) to the subject of this post - the multiverse.
What we call our universe - what we can see out to 14 billion years or so in all directions - may not be unique. There may have been more than one Big Bang, producing universes with different physical laws than our own. This is not just wild speculation. The existence of a multiverse, an "entire ensemble of innumerable regions of disconnected space-time", is one of the consequences of Andrei Linde's theory of eternal chaotic inflation.
But I am getting ahead of myself. Let's step back to see how Linde came to develop his theory.
The Big Bang, the creation of our universe 13.77 billion years ago from a singularity of immense energy, is one of the most widely held theories in all of physics. Originally proposed in 1927 by the Belgian cosmologist and Catholic priest Georges Lemaître, it became the go-to explanation for how the universe began when two engineers at Bell Labs accidentally discovered the Cosmic Microwave Background, a remnant from a very early stage of the universe, in 1964. According to the theory, the Big Bang explosion stretched the very fabric of spacetime, sending superheated matter in all directions. As it expanded, the matter cooled and started to aggregate, forming atoms, then elements, then stars, galaxies and, ultimately, all we know and see today. [1]
In 1981, seventeen years after Penzias and Wilson's discovery, while attempting to answer some of the baffling questions about the observable universe and the Big Bang*, astrophysicist Alan Guth proposed the theory of cosmic inflation. The term refers to the explosively rapid expansion of space-time that occurred a tiny fraction of a second after the Big Bang. In another tiny fraction of a second. the expansion slowed to its current rate. According to Guth's theory, for less than a millionth of a trillionth of a trillionth of a second after the universe's birth, an exotic form of matter exerted a counterintuitive force: gravitational repulsion. Although we normally think of gravity as being attractive (picture Isaac Newton and the falling apple), Albert Einstein’s theory of general relativity allows for such a force. Under the conditions present in the early universe, when temperatures were extraordinarily high, Guth says the existence of this material was reasonably likely. “It only has to be a speck**,” he says. “But when that speck starts to inflate, the expansion is exponential.” [1,2]
Inflation answers many of the unresolved questions of the Big Bang and predicts the observable universe. In 1986, Guth's co-Nobel Prize winner Andrei Linde took cosmic inflation a step further. Linde explains his theory of “eternal chaotic inflation” thus: “Instead of a universe with a single law of physics, eternal chaotic inflation predicts a self-reproducing, eternally existing multiverse where all possibilities can be realized.” [3]
Eternal chaotic inflation is also one attempt to answer the questions: what came before the Big Bang? how will the universe end?***
According to Linde’s theory, there has always been a yesterday and there will always be a tomorrow. Our universe grew out of a quantum fluctuation in some pre-existing region of the space-time continuum. “Each particular part of the [multiverse] may stem from a singularity somewhere in the past and it may end up in a singularity somewhere in the future.” [3]
Mind-boggling. Speculative. Yes, and yet lines of corroborating evidence have convinced many cosmologists to such a degree that cosmic inflation and eternal chaotic inflation have become the "standard model" of cosmology. Physicists around the world are working on the theory of an inflationary multiverse consisting of different universes with different laws of physics.
The infinite possibilities opened by Linde's Multiverse Theory suggest that the end of physics will not occur anytime soon.
Graphic: The Standard Cosmological Model
Notes
*Two of these questions: Why does the visible universe appear flat and largely homogeneous when general relativity suggests that space should be curved? How did the Universe get so big in the time since the Big Bang given the current rate of expansion?"
**According to cosmic inflation theory, a hundred-thousandth of a gram of matter would suffice to create a universe.
***The traditional scenarios for the end of the universe have been a) the universe expands indefinitely until all energy and matter reach a "heat death" with temperatures near absolute zero b) the matter in the universe is so great that it causes a reversal of the expansion, galaxies collapse and the universe ends in a "Big Crunch", a reverse Big Bang c) the expansion of the universe reaches a steady-state, expansion halts but the universe does not end in a Big Crunch. In Linde's theory of eternal chaotic inflation, the incredibly rapid expansion of space-time (inflation) is a continual process with new universes being created all the time. While a given universe such as ours would suffer heat death, the Multiverse itself would never end.
Sources: [1] Scientific American [2] space.com -1 [3] Stanford Magazine [4] space.com - 2