Once again, Fjordman has honoured Vlad Tepes with a segment of one of his original essays, and a subject close to my heart, History of Astrophysics. Part IV can be read here: Tundra Tablids Fjordman Cosmology Part IV
Even after the introduction of the telescope it took centuries for Western astronomers to work out the true scale of the universe. The English astronomer and architect Thomas Wright (1711-1786) suggested around 1750 that the Milky Way was a disk-like system of stars and that there were other star systems similar to it, only very far away from us. Soon after, Immanuel Kant in 1755 hypothesized that the Solar System is part of a huge, lens-shaped collection of stars and that similar such “island universes” exist elsewhere, too. Kant’s thoughts about the universe, however, were philosophical and had little observational content.
Johann Heinrich Lambert (1728-1777), a Swiss-born mathematician, astronomer and philosopher, “provided the first rigorous proof that ? (the ratio of a circle’s circumference to its diameter) is irrational, meaning that it cannot be expressed as the quotient of two integers.” Lambert, the son of a tailor, was largely self-educated and early in his life began astronomical investigations with instruments he built for himself. He made a number of innovations in the study of heat and light and corresponded with Kant, with whom he shares the honor of being among the first to believe that certain nebulae are disk-shaped galaxies like the Milky Way.
William Herschel’s On the Construction of the Heavens from 1785 was the first quantitative analysis of the Milky Way’s shape based on careful telescopic observations. William Parsons in Ireland with the largest telescope of the nineteenth century, the Leviathan of Parsonstown, was after 1845 able to see the spiral structure of some nebulae, what we call spiral galaxies. Already in 1612 the German astronomer Simon Marius had published the first systematic description of the Andromeda Nebula (Galaxy) from the telescopic era, but he could not resolve it into individual stars. The decisive breakthrough came in the early twentieth century.
The Mount Wilson Observatory in California was founded by George Ellery Hale. He offered the young astronomer Harlow Shapley (1885-1972) a research post. Shapley had earned a Ph.D. at Princeton University in 1913 and in 1921 became director of the Harvard College Observatory. Before 1920 he had made his greatest single scientific discovery: That our galaxy was much bigger than earlier estimates by William Herschel made it out to be, and that the Sun was not close to its center. He didn’t get everything right, though. In the Great Debate with fellow American astronomer Heber Curtis (1872-1942) he argued that the mysterious spiral nebulae were merely gas clouds that were a part of the Milky Way and that everything consisted of one large galaxy: our own. Curtis, on the other hand, claimed that the universe consisted of many galaxies comparable to our own. Shapley was reasonably correct regarding the size of our galaxy, but Curtis was right that our universe is composed of multiple galaxies.
Jacobus Kapteyn (1851-1922) started the highly productive twentieth century Dutch school of astronomers. He studied physics at the University of Utrecht in the Netherlands, spent three years at the Leiden Observatory and thereafter founded and led the study of astronomy at the dynamic University of Groningen from 1878 to 1921. Kapteyn observed that many of the stars in the night sky could be roughly divided into two streams, moving in nearly opposite directions. This insight led to the finding of the galactic rotation of the Milky Way.
The Swedish astronomer Bertil Lindblad (1895-1965) was a graduate of the University of Uppsala and directed the Stockholm Observatory in Sweden from 1927-65. He studied the structure of star clusters, but his most important work was regarding galactic rotation. His efforts led directly to Jan Oort’s theory of differential galactic rotation. He confirmed Shapley’s approximate distance to the center of our galaxy and estimated its total mass. Oort at the University of Leiden in 1927 confirmed Lindblad’s theory that the Milky Way rotates, and their model of galactic rotation was verified by the Canadian astronomer John Plaskett (1865-1941), originally a mechanic employed by the University of Toronto physics department. Following the lead of Kapteyn, Lindblad and Oort, the Dutch astronomer Hendrik C. van de Hulst (1918-2000) and others in the 1950s mapped the clouds of the Milky Way and delineated its spiral structure. “Van de Hulst made extensive studies of interstellar grains and their interaction with electromagnetic radiation. He wrote important books on light scattering and radio astronomy. He investigated the solar corona and the earth’s atmosphere.”
The job of cataloging individual stars and recording their position and brightness from photographic plates at the Harvard College Observatory was done by a group of women, “human computers” working with Edward Pickering, among them the American astronomer Henrietta Swan Leavitt (1868-1921). The concept of “standard candles,” stars whose brightness can be reliably calculated and used as benchmarks to measure vast astronomical distances, was introduced by Leavitt for Cepheid variable stars. She became head of the photographic photometry department, and during her career she discovered more than 2,400 variable stars. This work aided Edwin Hubble in making his groundbreaking discoveries.
Scientists are flawed like other people. Newton could be a difficult man to deal with, yet he was undoubtedly one of the greatest geniuses in history. Henry Cavendish was a brilliant experimental scientist as well as painfully shy, and Nikola Tesla was notoriously eccentric. Judging from the many stories about him, Edwin Hubble had an ego the size of a small country, but that doesn’t change the fact that he was a great astronomer whose work permanently altered our view of the universe. He was a sociable man who partied with movie stars like Charlie Chaplin and Greta Garbo and with famous writers such as Aldous Huxley.
His contemporary Milton L. Humason (1891-1972), despite a very limited formal education, was a meticulous observer. In 1919, Hubble joined the Mount Wilson Observatory. The 2.5 meter Hooker telescope there was completed before 1920, at which point it was the largest telescope in the world. Using this, Hubble identified Cepheid variable stars in Andromeda. This allowed him to show that the distance to Andromeda was greater than Shapley’s proposed extent of the Milky Way. Hubble demonstrated that there are countless galaxies of different shapes and sizes out there, and that the universe is far larger than anybody had imagined. He then formulated Hubble’s Law and introduced the concept of an expanding universe. “His investigation of these and similar objects, which he called extragalactic nebulae and which astronomers today call galaxies, led to his now-standard classification system of elliptical, spiral, and irregular galaxies, and to proof that they are distributed uniformly out to great distances. (He had earlier classified galactic nebulae.) Hubble measured distances to galaxies and with Milton L. Humason extended Vesto M. Slipher’s measurements of their redshifts, and in 1929 Hubble published the velocity-distance relation which, taken as evidence of an expanding Universe, is the basis of modern cosmology.”
The Austrian physicist Christian Doppler described what is known as the Doppler Effect for sound waves in the 1840s and predicted that it would be valid for other kinds of waves, too. An observed redshift in astronomy is believed to occur due to the Doppler Effect whenever a light source is moving away from the observer, displacing the spectrum of that object toward the red wavelengths. Hubble discovered that the degree of redshift observed in the light coming from other galaxies increased in proportion to the distance of those galaxies from us.
The work of Walter Baade in the 1940s and the American astronomer Allan Sandage (born 1926) in the 1950s resulted in revisions of the value of Hubble’s Constant and by extension the age of the universe. Sandage earned his doctorate under Baade and went on to determine the first reasonably accurate value for age of the universe. “He has calibrated all of the ‘standard candles’ to determine distances of remote galaxies and has several times presented (often with Gustav Tammann) revised estimates of the value of the Hubble constant.”
Hubble’s observational work led the great majority of scientists to believe in the expansion of the universe. This had a huge impact on cosmology at the time, among others on the Dutch mathematician and astronomer Willem de Sitter (1872-1934). De Sitter had studied mathematics at the University of Groningen. A chance meeting with the Scottish astronomer David Gill led to an invitation to work at the Observatory at the Cape of Good Hope. After four years there, de Sitter returned to the Netherlands and became a mathematical astronomer, earning his doctorate under Jacobus Kapteyn. He spent most of his career at the University of Leiden, where he expanded its fine astronomy program. He performed statistical studies of the distribution and motions of stars but is best known for his contributions to cosmology.
According to writers J. J. O’Connor and E. F. Robertson, “Einstein had introduced the cosmological constant in 1917 to solve the problem of the universe which had troubled Newton before him, namely why does the universe not collapse under gravitational attraction. This rather arbitrary constant of integration which Einstein introduced admitting it was not justified by our actual knowledge of gravitation was later said by him to be the greatest blunder of my life. However de Sitter wrote in 1919 that the term ‘… detracts from the symmetry and elegance of Einstein’s original theory, one of whose chief attractions was that it explained so much without introducing any new hypothesis or empirical constant.’ In 1932 Einstein and de Sitter published a joint paper with Einstein in which they proposed the Einstein-de Sitter model of the universe. This is a particularly simple solution of the field equations of general relativity for an expanding universe. They argued in this paper that there might be large amounts of matter which does not emit light and has not been detected.”
The cosmologist Georges Lemaître (1894-1966) from Belgium was a Catholic priest as well as a trained scientist. The combination is not unique. The Italian astronomer Angelo Secchi was a priest and the creator of the first modern system of stellar classification; the Bohemian scholar Gregor Mendel, too, was a priest and the founder of modern genetics. World War I interrupted Lemaître’s studies. Serving as an artillery officer he witnessed one of the first poison gas attacks in history. After the war he studied physics and was ordained as an abbé.
In 1925 he accepted a professorship at the Catholic University of Louvain near Brussels. He reviewed the general theory of relativity and his calculations showed that the universe had to be either shrinking or expanding. Lemaître argued that the entire universe was initially a single particle – the “primeval atom” – which disintegrated in a massive explosion, giving rise to space and time. He published a model of an expanding universe in 1927 which had little impact then, but in 1930, following Hubble’s work, Lemaître’s former teacher at Cambridge University, Arthur Eddington, shared his paper with de Sitter. Albert Einstein confirmed that Lemaître’s work “fits well into the general theory of relativity.”
Unknown to Lemaître, another person had independently come up with overlapping ideas. This was the Russian mathematician Alexander Friedmann (1888-1925), who in 1922 had published a set of possible mathematical solutions that gave a non-static universe. Already in 1905 he wrote a mathematical paper and submitted it to the German mathematician David Hilbert for publication. In 1914 he went to Leipzig to study with the Norwegian physicist Vilhelm Bjerknes, the leading theoretical meteorologist of the time. He then got caught up in the turbulent times of the Russian Revolution in 1917 and the birth of the Soviet Union.
Friedmann’s work was hampered by a very abstract approach and aroused little interest at the time of publishing. Lemaître attacked the issue from a much more physical point of view. Friedmann died from typhoid fever in 1925, but he lived to see the city Saint Petersburg renamed Leningrad after the revolutionary leader and Communist dictator Vladimir Lenin (1870-1924). The astrophysicist George Gamow studied briefly under Alexander Friedmann, but he fled the country in 1933 due to the increasingly brutal repression of the Communist regime, which directly or indirectly killed millions of its own citizens during this time period.
Although Lemaître’s “primeval atom” was the first version of this theory of the origin of the universe, a more comprehensive model was published in 1948 by Gamow and the cosmologist Ralph Alpher (1921-2007) in the USA. The term “Big Bang” was coined somewhat mockingly by Fred Hoyle, who did not believe in it. Gamow decided as a joke to include his friend Hans Bethe as co-author of the paper, thus making it known as the Alpher, Bethe, Gamow or alpha-beta-gamma paper, after the first three letters of the Greek alphabet. It can be seen as the beginning of Big Bang cosmology as a coherent scientific model.
Yet this joke had the practical effect of downplaying Alpher’s contributions. He was then a young doctoral student, and when his name appeared next to those of two of the most famous astrophysicists in the world it was easy to assume that he was a junior partner. As a matter of fact, he made very substantial contributions to the Big Bang model whereas Hans Bethe, brilliant though he was as a scientist, in this case had contributed very little. Ralph Alpher in many ways ended up being the “forgotten father” of the Big Bang theory.
Alpher published two papers in 1948. In another with the scientist Robert Herman (1914-1997) he predicted the existence of a cosmic background radiation as an “echo” of the Big Bang. Sadly, astronomers did not bother to search for this proposed echo at the time; radio astronomy was then still in its infancy. Alpher and Herman went on to calculate the present temperature corresponding to this energy. The remnant glow from the Big Bang must still exist in the universe today, although greatly reduced in intensity by the expansion of space.
The cosmic microwave background radiation, which is considered one of the strongest proofs in favor of the Big Bang theory, was accidentally discovered by Robert Wilson (born 1936) and Arno Penzias (born 1933) in the USA in 1964. Yet they did not initially grasp the full significance of what they had found, whereas Alpher and Herman were totally ignored when Wilson and Penzias received the Nobel Prize in Physics in 1978. In the early 1960s the Canadian James Peebles (born 1935) together with Robert H. Dicke (1916-1997) and David Todd Wilkinson (1935-2002) from the USA had also predicted the existence of the cosmic background radiation and planned to seek it just before it was found by Penzias and Wilson.
An alternative Steady State model was developed in 1948 by the Englishman Fred Hoyle together with Thomas Gold (1920-2004), an Austrian American astrophysicist born in Vienna to a wealthy Jewish industrialist, and Hermann Bondi, (1919-2005), an Anglo-Austrian who was also brought up in Vienna and arrived at Cambridge, Britain in 1937 and worked with Hoyle on radar during WW2. The Steady State model declined in popularity after the discovery of the cosmic microwave background radiation, the clearest evidence discovered so far indicating that something like the Big Bang really happened back in a very distant past.
According to our best current models, in its first 30,000 years the universe was radiation-dominated, during which time photons prevented matter from forming clumps. In the early stages there was an ongoing process of particles and antiparticles annihilating each other and spontaneously coming into being from radiation. Lucky for us there was a tiny surplus of ordinary matter, otherwise matter as we know it could not have existed. After this period the universe became matter-dominated, when clumps of matter could form. Most astrophysicists today believe that during the first 379,000 or so years, matter and energy formed an opaque plasma called the primordial fireball. The cosmic microwave background radiation (CMB) is believed to be the greatly redshifted remnant of the universe as it existed about 379,000 years after the Big Bang. It therefore contains the oldest photons in the observable universe.
Starting from this point, spacetime expansion had caused the temperature of the universe to fall below 3000 K, enabling protons and electrons to combine to form hydrogen atoms, at which point the universe became transparent. Following billions of years of expansion the CMB radiation is now very cold, less than three degrees above absolute zero. This nearly perfect blackbody radiation shines primarily in the microwave portion of the electromagnetic spectrum and is consequently invisible to the human eye, but it is isotropic and fills the universe in every direction we can observe. Only with very sensitive instruments can cosmologists detect minute fluctuations in the cosmic microwave background temperature, yet these tiny fluctuations were of critical importance for the formation of stars and galaxies.
In 1989, NASA launched its Cosmic Background Explorer (COBE) satellite into space under the leadership of American astrophysicist John C. Mather (born 1946). Detectors on board the COBE satellite were designed by a team led by American astrophysicist George Smoot (born 1945) and were sensitive enough to measure minute fluctuations, corresponding to the presence of tiny seeds of matter clumping together under the influence of gravity. A follow-up mission was the Wilkinson Microwave Anisotropy Probe satellite – WMAP – from the USA. Mather and Smoot shared the 2006 Nobel Prize in Physics for providing a view of the CMB in unprecedented detail. The European Planck space observatory was launched 2009 and will study the cosmic microwave background radiation in even greater detail over the entire sky.
Alan Guth (born 1947) is a leading American theoretical physicist and cosmologist, born to a middle-class Jewish couple in New Jersey. He graduated from the Massachusetts Institute of Technology (MIT) in 1968 and held postdoctoral positions at Princeton University, Columbia University, Cornell University and the Stanford Linear Accelerator Center. He was initially interested in elementary particle physics but later shifted to cosmology, bridging the gap between the very big and the very small. In the 1980s he proposed that the expansion of the universe was propelled by a repulsive anti-gravitational force generated by an exotic form of matter.
“Although Guth’s initial proposal was flawed (as he pointed out in his original paper), the flaw was soon overcome by the invention of ‘new inflation,’ by Andrei Linde in the Soviet Union and independently by Andreas Albrecht and Paul Steinhardt in the US.”
Andrei Linde (born 1948) is a prominent Russian theoretical physicist, originally educated at Moscow State University and the Lebedev Physical Institute in what was then the Soviet Union. He eventually moved to the West at the end of the Cold War, first as a staff member of CERN in Western Europe, then as a professor of physics at Stanford University in the USA. The idea of an inflationary multiverse (reality consisting of many universes with different physical properties) was proposed in 1982. According to the concept of cosmic inflation championed by Guth and Linde, during fractions of a second the young universe underwent exponential expansion, doubling in size at least 90 times. As the magazine Discover states:
“Much of today’s interest in multiple universes stems from concepts developed in the early 1980s by the pioneering cosmologists Alan Guth at MIT and Andrei Linde, then at the Lebedev Physical Institute in Moscow. Guth proposed that our universe went through an incredibly rapid growth spurt, known as inflation, in the first 10-30 second or so after the Big Bang. Such extreme expansion, driven by a powerful repulsive energy that quickly dissipated as the universe cooled, would solve many mysteries. Most notably, inflation could explain why the cosmos as we see it today is amazingly uniform in all directions. If space was stretched mightily during those first instants of existence, any extreme lumpiness or hot and cold spots would have immediately been smoothed out. This theory was modified by Linde, who had hit on a similar idea independently. Inflation made so much sense that it quickly became a part of the mainstream model of cosmology.”
The mathematical physicist Edward Witten (born 1951), a leading researcher in superstring theory and widely hailed as one of the greatest scientists of his generation, came from a Jewish family. His father was a physicist specializing in gravitation and general relativity. Edward Witten was educated at the Brandeis, Princeton and Harvard Universities in his native USA and became a professor at the Institute for Advanced Study at Princeton. His early research focused on electromagnetism, but he developed an interest in what is now known as superstring theory and made very valuable contributions to Morse theory, supersymmetry, knot theory and the differential topology of manifolds. Although primarily a physicist he was nevertheless awarded the prestigious Fields Medal in 1990 for his superb mathematical skills.
Neil Turok (born 1958), a white South African, together with Paul Steinhardt (born 1952), director of the Princeton Center for Theoretical Science in the USA, devised a controversial cosmological model in 2002. They proposed the “cyclic model” in which the universe was born multiple times in cycles of fiery death and rebirth. Their idea is based on a mathematical model in which our universe is a three-dimensional membrane or “brane” embedded in four-dimensional space. The Big Bang was caused when our brane crashed against a neighboring one; our universe is just one of many in a “multiverse” of universes. Enormous “branes” representing different parts of our universe(s) collide once in hundreds of billions of years.
Despite all this progress, countless questions remain unanswered. As Alan Guth notes, even if the present form of the Big Bang theory with inflation should turn out to be correct, it says next to nothing about exactly what “banged,” what caused it to bang or what happened before this event. “I actually find it rather unattractive to think about a universe without a beginning. It seems to me that a universe without a beginning is also a universe without an explanation.”
Another major question is whether the expansion that our universe appears to be experiencing at the moment will continue indefinitely, or whether there is enough mass to slow it down and eventually reverse it, causing the universe to collapse onto itself in a “Big Crunch.” The Swiss astronomer Fritz Zwicky already in 1933 stumbled upon observations indicating that there is more than visible matter out there and that this “dark matter” affects the behavior of galaxies.
In the 1970s the American astrophysicist Jerry Ostriker (born 1937) along with James Peebles discovered that the visible mass of a galaxy is not sufficient to keep it together. The astronomer Vera Rubin (born 1928) studied under Richard Feynman, Hans Bethe, George Gamow and other prominent scholars in the United States. She became a leading authority on the rotation of galaxies. She teamed up with astronomer Kent Ford (born 1931) and began making Doppler observations of the orbital speeds of spiral galaxies. Her calculations based on this empirical evidence showed that galaxies must contain ten times as much mass as can be accounted for by visible stars. She realized that she had discovered evidence for Zwicky’s proposed “dark matter,” and her work brought the subject to the forefront of astrophysical research. Rubin is an observant Jew and sees no conflict between science and religion.
In the 1990s, two competing groups began observing a certain type of supernovas as a way to study the expansion of the universe. In 1998 a team led by Saul Perlmutter (born 1959) at Lawrence Berkeley National Laboratory in California completed a search for type Ia supernovas, supplemented by a second team led by Brian P. Schmidt (born 1967) and Adam Riess (born 1969). To everyone’s surprise, their observations indicated that the expansion was not slowing down due to gravitational attraction, as many had suspected, but was speeding up. Further results have confirmed that the expansion of the universe appears to be accelerating.
Astronomers currently estimate that out of the total mass-energy budget in our universe, a meager 4% consists of ordinary matter that makes up everything we can see, such as stars and planets, whereas 21% is dark matter. A full 75% consists of “dark energy,” an even more mysterious entity than dark matter. The US cosmologist Michael S. Turner coined the term “dark energy” to describe the mysterious force which seems to work like anti-gravity.
Petr Horava is a Czech string theorist who is currently a professor of physics at the University of California, Berkeley, and co-author with Edward Witten on articles about string and M-theory. He has proposed a modified theory of gravity, with applications in quantum gravity and cosmology. “I’m going back to Newton’s idea that time and space are not equivalent,” Horava says. At low energies, general relativity emerges from this underlying framework and the fabric of spacetime restitches. He likens this emergence to the way some exotic substances change phase. For example, at low temperatures liquid helium’s properties change dramatically into a “superfluid.” Cosmologist Mu-In Park of Chonbuk National University in Korea believes that this gravity could be behind the accelerated expansion of the universe.
A few scientists have controversially proposed resurrecting the discredited light-bearing ether of nineteenth century physics. Niayesh Afshordi, an Iranian-born USA-based physicist, suggests a model where space is filled with an invisible fluid – ether – as predicted by some proposed quantum theories of gravity such as Horava’s. Black holes may give off feeble radiation, as suggested by many quantum theories of gravity. Afshordi calculates that this radiation could heat the ether and, like bringing a pot of water to a boil, generate a negative pressure of “anti-gravity” throughout the cosmos. This would have the consequence of speeding up cosmic expansion, but it took billions of years for black holes to heat up the ether sufficiently. Another, less exotic alternative theory called Modified Newtonian Dynamics has been introduced by the Israeli astrophysicist Professor Mordehai Milgrom. This proposal has received the backing of some notable scientists, but so far only a minority of them.
Perhaps “dark matter” will turn out to be a new class of particles and matter that behave very differently from the kind of matter we are most familiar with. Perhaps we still don’t know enough about the nature of gravity or the age of the universe and that “dark energy” will in hindsight turn out to be a fancy name for something that does not actually exist, a twenty-first equivalent of phlogiston. Or perhaps we will discover new insights that will fundamentally alter our understanding of the very fabric of spacetime. Whatever the truth turns out to be, the terms “dark matter” and “dark energy” are reminders that scientists cannot yet fully explain some of the observed properties of the visible universe according to known physical laws.
In the late 1800s, many European scholars sincerely believed that they understood almost all of the basic laws of physics. They had reason for this optimism as the previous century had indeed produced enormous progress, culminating in the new science of thermodynamics and the electromagnetic theories of Maxwell. Max Planck was once told by one of his teachers not to study physics since all of the major discoveries in that field had allegedly been made. Lucky for us he didn’t heed this advice but went on to initiate the quantum revolution. We have far greater knowledge today than people had back then, but maybe also greater humility: We know how little we truly understand of the universe, and that is probably a good thing.