Day 314: Escape From Quantopia

Giordano Bruno discovered in the lights of the night sky a bottomless ocean of suns where others saw only sketches projected from human imagination. Alone among the pioneers of science, Bruno fully absorbed the lesson of Copernicus, something even the solar revolutionary himself failed to grasp. Not only is the cosmos not centered on Earth but the very idea of center has no physical meaning. There’s no more a privileged location from which all places are subject to objective measurement than a virgin or a goatfish in the sky.

“For there is in the Universe,” wrote the itinerant philosopher, “neither center nor circumference, but, if you will, the whole is central, and every point also may be regarded as part of a circumference in respect to some other central point.” If Earth seems like the center of all things, that’s only because we live on it. To lunar dwellers the Moon is center-stage. It’s all perspective.

Bruno never hesitated to announce his relativistic revelation to any and all. For this and other “impieties,” the church ordered him burned at the stake on Ash Wednesday 1600.

His successors lacked his penetrating insight. Following Isaac Newton’s observation that massive bodies attract each other at a distance, consensus opinion coalesced around the idea of a subtle kind of matter permeating space that mediates the force of gravity much as water mediates waves on the ocean. In the nineteenth century scientists updated this approach with their contention that electromagnetic waves propagate across a “luminiferous aether.” Aside from serving as a fixed framework establishing the boundaries and absolute center of the universe, the aether was thought to enable the cosmic machine to operate by contact mechanics, not unlike the contraptions we fashion down here on the terrestrial plane.

By the turn of the twentieth century, the great questions of existence seemed to be dissolving in the magic potion of science. The world had never been so clear, the ground never so solid and dependable.
Since then all center and substance have shattered. Bruno could at least count on God. Now we’ve got nothing, adrift in a void without reference points. The Great Wall of Certainty has collapsed under its own density. From the other side Bruno confronts us with crackling skin and blazing eye.

Up until 1897 the idea of material substance wasn’t generally regarded as a pre-scientific mirage. But in that year JJ Thomson cut the “uncuttable” atom. The solid core of matter turned out to be internally differentiated, with vast empty gulfs punctuated by occasional pinpricks of mass. An electron isn’t so much a thing as a field of possibilities across which a “particle” randomly bops around like a speck of static on a TV screen. It’s a dance whose steps can be calculated according to a probability wave. Let’s say an electron is trapped inside a perfectly sealed container. As it bounces off the walls, its probability wave gradually seeps out to the surrounding area until the electron itself is no longer inside the container.

This is why quantum physicists don’t speak of substance. Reality is composed of “information.” The randomness of the quantum level averages out to the predictability of the perceptual level. All that is solid melts into stats.

The de-centering of all centers began in 1887 when Albert Michelson and Edward Morley carried out an experiment designed to prove the existence of the aether. Their “interferometer,” a box containing a telescope and mirrors set at odd angles, could measure the speed of light on Earth relative to its speed in outer space. Since our planet is in motion, scientists reasoned that the light reaching us from a distant source should be either faster or slower than in the stillness of space, depending on whether we’re approaching the starlight or receding. But when Michelson and Morley looked at their results, they found no interference and therefore no difference in the speed of light relative to Earth’s motion.
For years their findings puzzled physicists, though Hendrick Lorentz wrote up some interesting equations meant to explain how the aether was somehow still relevant despite the no-show in ‘87. Not until Einstein came along did anyone see the true weight of the Michelson-Morley results. With a little tweaking of Lorentz’s equations, he demonstrated that space has no fixed framework, no center or circumference. As far as the universe is concerned, we are nowhere. Bruno was vindicated.

Whether you’re adrift in deep space or breezing along at 185,000 miles per second, light always travels faster, at 186,000 miles per second. light always travels 186,000 miles per second faster. Change your frame of reference and the flow of time changes along with it. Only the speed of light remains constant.

Or so we thought. Light has many different speeds, depending on what kind of medium it’s traversing. Water, for instance, slows it down by 75%. In the final days of the twentieth century, researcher Lene Vestergaard Hau imprisoned a beam of light in a frozen cloud of atoms, stopping it dead in its tracks and demonstrating, once and for all, that nothing is sacred.
...
You don’t have to consult Aristotle to realize something is holding all this up. You can’t have miles and miles of accident and no essence anywhere in sight. Something’s got to be substantial, not just informational. Absolute, not just relative. Even illusion is illusory only in contrast to reality. Who or what is hallucinating this hallucination?
For the answer we must go back, once more, to that magnetic moment when the world turned inside out. The clock is winding down on the nineteenth century as young Henri Bergson, a Polish Jew transplanted to France, studies philosophy at the Ecole Superier Normale. Captivated by the English positivist Herbert Spencer and his book, Progress: Its Law and Cause, Bergson is dazzled by the promise of a completely coordinated system of knowledge, a synthetic scheme founded on a single absolute principle: the persistence of force. Physical science, prophecies Spencer, shall render the world transparent, granting unimagined power to the human race.

Then one day Bergson is shaken by a terrible insight, as if the whole twentieth-century intellectual meltdown has appeared to him in a blast.

There’s no time in physics.

“Newton’s laws of motion,” according to physicists Christopher Hill and Leon Lederman, “make no distinction between past and future, and time can apparently flow in any direction.” On their website devoted to mathematician Emmy Noether and her principle of symmetry-breaking, Hill and Lederman describe the universe as a movie that could run through a projector in reverse as readily as forward. “When applied to simple systems, billiard balls colliding on the table, atomic collisions, etc., it would not be possible to tell in which direction the film was progressing. The motion we see satisfies laws of motion that are the same, whether run forward or backward.”5 Future and past are effectively interchangeable.

“Notice another peculiar aspect of physics,” write Hill and Lederman. “Nowhere in any formulation does the issue of a special point in time called ‘now’ ever occur. Yet, we humans sense something we call ‘now.’ Is it an illusion? We call this the ‘Now’ question.”

I can’t help but feel present. Even memories concern moments once present. To be human is to be temporal, informed by a past and oriented toward a future. Without ongoing presence our consciousness, the sensation of now, is null and void. Lacking real time, we aren’t real either.

~~Escape From Quantopia: Collective Insanity in Science and Society -by- Ted Dace

Day 313: How We'll Live on Mars

Recently, after one of his rockets exploded just above its launch pad, Elon Musk wryly tweeted: “Rockets are tricky.” He’s right: close to two-thirds of all the attempts to get probes to Mars have failed.

A casual observer might well wonder why humans have had so much trouble getting to Mars when getting to the moon more than fifty years ago seemed relatively easy. Mostly, it’s a matter of distances. The scale changes are phenomenal. The moon floats between 225,000 and 250,000 miles from Earth, depending on the lunar cycle. Mars can be up to a thousand times farther away. In 2003, Mars and Earth were closer than they had been in almost sixty thousand years—only about 34 million miles apart. But because Earth’s orbit around the sun takes 365 days and Mars’s takes 687 Earth days, the two planets can get out of sync and wind up very far apart, with each on a different side of the sun. When they are far apart, they are really far apart—about 250 million miles. Mars thus varies between being 140 and 1,000 times farther away from Earth than the moon.

Put another way, humans can make a round-trip to the moon and back in six days. (We could have gotten there in one day with the boost the Saturn V rocket offered, but we would have been going so fast when we arrived that we would simply have shot by instead of being captured by the moon’s weak gravity.) Using the Hohmann transfer orbits suggested by von Braun in Das Marsprojekt, even if we went much faster than the speed at which the Apollo astronauts went to the moon, we would still have to fly about a thousand times farther than the distance to the moon to end up at Mars. That’s because we simply can’t carry enough fuel to blast ahead in a straight line. Without unlimited cheap energy, we will always be in orbit around something in this solar system, so all our trajectories will be curved. There are no foreseeable shortcuts in the next twenty years that could get us to Mars in much less than 250 days each way, although SpaceX is designing more powerful and more efficient rocket engines that could shorten the trip substantially.

Even the early, more straightforward missions to Mars—missions that merely attempted to fly by the planet—regularly met with disaster. The far more difficult Mars orbiter missions, and especially the lander missions, made something of a mockery of our grasp on space technology.

The Soviets seemed to get the worst of the early Martian calamities. The first Earth object ever to reach the surface of Mars was a Soviet lander called Mars 2. It crash-landed in November of 1971, and was a follow-up project to Kosmos 419, which never got out of orbit around the Earth, much less headed to Mars. The next month, Mars 3 actually made a successful landing but stopped sending signals after twenty seconds. Mars 4’s guidance system failed, and it whizzed by the planet completely. Mars 5 was the most successful Soviet probe. It was inserted into an elliptical orbit in February 1974, and returned about sixty photos during twenty-two orbits, then failed. Mars 6 reached the planet in March of 1974 and launched a lander that crashed on the surface. It transmitted atmospheric data for about four minutes before it went silent, but the data was largely incomprehensible because of a computer chip failure. Mars 7 also entered orbit in March 1974 but launched its lander four hours too early and missed the planet. There were a handful of other earlier Mars missions launched by the Soviets that failed, as well as later failed missions. In 1996 the Russian Space Agency launched an orbiter/lander called Mars 96 that didn’t escape Earth’s gravity and broke up over the Pacific Ocean. Since then, the Russians have seemed less than eager to challenge their jinx.

A huge hindrance to successfully landing a probe on Mars is that it takes communications a long time to arrive from Earth. When Earth and Mars are farthest apart, it takes a radio signal twenty-one minutes to get from Earth to Mars, and then another twenty-one minutes for a return signal to get back to Earth. Unmanned spacecraft must therefore use artificial intelligence software to make decisions in emergencies, because there’s no time to call home for help.

But all the bad history of early lander mission failure slipped into the darker reaches of our consciousness after NASA scored big by successfully landing the Spirit and Opportunity rovers on Mars. More recently, the success of the Curiosity rover has stolen our attention. Opportunity is still actively exploring Mars after more than a decade. Curiosity finished a Martian year’s (just under two Earth years) worth of exploration in 2014, and is just getting started on its longer mission. Nevertheless, the distances these rovers have covered is not impressive. Opportunity has traveled only about twenty-six miles since 2004, and Curiosity has gone a bit more than six miles in nearly three years.

Despite the failures of the past, NASA’s success with Curiosity proves that relatively large payloads can be delivered to the surface of Mars, making not only manned flights more realistic but also the idea of cargo and resupply flights. Changing the equation from large payloads like Curiosity to human cargo is mostly just a step up in scale, frequency of cargo launches, and oxygen. SpaceX is refining a Dragon spacecraft with the ability to carry seven astronauts that it expects to fly to the International Space Station as early as 2016, although Musk recently said that “2017 is probably a realistic expectation of when we’ll send a human into space for the first time.” He has joked that a stowaway astronaut on its current Dragon vehicle that resupplied the International Space Station would survive the flight because part of the craft is pressurized; it was designed from the start to be converted to carry astronauts instead of cargo.

Currently, the Russian Soyuz spacecraft is the only vehicle that can get astronauts to the space station and back in the absence of the space shuttle. It dates to 1966 and, along with the Soyuz rocket that carries it into space, has proven to be the most reliable space vehicle in history. As made famous in the movie Gravity, at least one Soyuz spacecraft is attached to the International Space Station at all times for use as an emergency escape vehicle. The Russians charge more than $50 million to fly an astronaut to the space station. SpaceX wants that business.

~~How We'll Live on Mars -by- Stephen L. Petranek

Day 276: Galileo’S Daughter

Most Illustrious Lord Father,

We are terribly saddened by the death of your cherished sister, our dear aunt; but our sorrow at losing her is as nothing compared to our concern for your sake, because your suffering will be all the greater, Sire, as truly you have no one else left in your world, now that she, who could not have been more precious to you, has departed, and therefore we can only imagine how you sustain the severity of such a sudden and completely unexpected blow. And while I tell you that we share deeply in your grief, you would do well to draw even greater comfort from contemplating the general state of human misery, since we are all of us here on Earth like strangers and wayfarers, who soon will be bound for our true homeland in Heaven, where there is perfect happiness, and where we must hope that your sister’s blessed soul has already gone. Thus, for the love of God, we pray you, Sire, to be consoled and to put yourself in His hands, for, as you know so well, that is what He wants of you; to do otherwise would be to injure yourself and hurt us, too, because we lament grievously when we hear that you are burdened and troubled, as we have no other source of goodness in this world but you.

I will say no more, except that with all our hearts we fervently pray the Lord to comfort you and be with you always, and we greet you dearly with our ardent love.

FROM SAN MATTEO, THE 10TH DAY OF MAY 1623.
Most affectionate daughter,
S. Maria Celeste

The day after his sister Virginia’s funeral, the already world-renowned scientist Galileo Galilei received this, the first of 124 surviving letters from the once-voluminous correspondence he carried on with his elder daughter. She alone of Galileo’s three children mirrored his own brilliance, industry, and sensibility, and by virtue of these qualities became his confidante.

Galileo’s daughter, born of his long illicit liaison with the beautiful Marina Gamba of Venice, entered the world in the summer heat of a new century, on August 13, 1600—the same year the Dominican friar Giordano Bruno was burned at the stake in Rome for insisting, among his many heresies and blasphemies, that the Earth traveled around the Sun, instead of remaining motionless at the center of the universe. In a world that did not yet know its place, Galileo would engage this same cosmic conflict with the Church, treading a dangerous path between the Heaven he revered as a good Catholic and the heavens he revealed through his telescope.

Galileo christened his daughter Virginia, in honor of his “cherished sister.” But because he never married Virginia’s mother, he deemed the girl herself unmarriageable. Soon after her thirteenth birthday, he placed her at the Convent of San Matteo in Arcetri, where she lived out her life in poverty and seclusion.

Virginia adopted the name Maria Celeste when she became a nun, in a gesture that acknowledged her father’s fascination with the stars. Even after she professed a life of prayer and penance, she remained devoted to Galileo as though to a patron saint. The doting concern evident in her condolence letter was only to intensify over the ensuing decade as her father grew old, fell more frequently ill, pursued his singular research nevertheless, and published a book that brought him to trial by the Holy Office of the Inquisition.

The “we” of Suor Maria Celeste’s letter speaks for herself and her sister, Livia—Galileo’s strange, silent second daughter, who also took the veil and vows at San Matteo to become Suor Arcangela. Meanwhile their brother, Vincenzio, the youngest child of Galileo and Marina’s union, had been legitimized in a fiat by the grand duke of Tuscany and gone off to study law at the University of Pisa.
   
Thus Suor Maria Celeste consoled Galileo for being left alone in his world, with daughters cloistered in the separate world of nuns, his son not yet a man, his former mistress dead, his family of origin all deceased or dispersed.

Galileo, now fifty-nine, also stood boldly alone in his world-view, as Suor Maria Celeste knew from reading the books he wrote and the letters he shared with her from colleagues and critics all over Italy, as well as from across the continent beyond the Alps. Although her father had started his career as a professor of mathematics, teaching first at Pisa and then at Padua, every philosopher in Europe tied Galileo’s name to the most startling series of astronomical discoveries ever claimed by a single individual.

In 1609, when Suor Maria Celeste was still a child in Padua, Galileo had set a telescope in the garden behind his house and turned it skyward. Never-before-seen stars leaped out of the darkness to enhance familiar constellations; the nebulous Milky Way resolved into a swath of densely packed stars; mountains and valleys pockmarked the storied perfection of the Moon; and a retinue of four attendant bodies traveled regularly around Jupiter like a planetary system in miniature.

“I render infinite thanks to God,” Galileo intoned after those nights of wonder, “for being so kind as to make me alone the first observer of marvels kept hidden in obscurity for all previous centuries.”

The newfound worlds transformed Galileo’s life. He won appointment as chief mathematician and philosopher to the grand duke in 1610, and moved to Florence to assume his position at the court of Cosimo de’ Medici. He took along with him his two daughters, then ten and nine years old, but he left Vincenzio, who was only four when greatness descended on the family, to live a while longer in Padua with Marina.

Galileo found himself lionized as another Columbus for his conquests. Even as he attained the height of his glory, however, he attracted enmity and suspicion. For instead of opening a distant land dominated by heathens, Galileo trespassed on holy ground. Hardly had his first spate of findings stunned the populace of Europe before a new wave followed: He saw dark spots creeping continuously across the face of the Sun, and “the mother of loves,” as he called the planet Venus, cycling through phases from full to crescent, just as the Moon did.
All his observations lent credence to the unpopular Sun-centered universe of Nicolaus Copernicus, which had been introduced over half a century previously, but foundered on lack of evidence.

Galileo’s efforts provided the beginning of a proof. And his flamboyant style of promulgating his ideas—sometimes in bawdy humorous writings, sometimes loudly at dinner parties and staged debates—transported the new astronomy from the Latin Quarters of the universities into the public arena. In 1616, a pope and a cardinal inquisitor reprimanded Galileo, warning him to curtail his forays into the supernal realms. The motions of the heavenly bodies, they said, having been touched upon in the Psalms, the Book of Joshua, and elsewhere in the Bible, were matters best left to the Holy Fathers of the Church.

Galileo obeyed their orders, silencing himself on the subject. For seven cautious years he turned his efforts to less perilous pursuits, such as harnessing his Jovian satellites in the service of navigation, to help sailors discover their longitude at sea. He studied poetry and wrote literary criticism. Modifying his telescope, he developed a compound microscope. “I have observed many tiny animals with great admiration,” he reported, “among which the flea is quite horrible, the gnat and the moth very beautiful; and with great satisfaction I have seen how flies and other little animals can walk attached to mirrors, upside down.”

Shortly after his sister’s death in May of 1623, however, Galileo found reason to return to the Sun-centered universe like a moth to a flame. That summer a new pope ascended the throne of Saint Peter in Rome. The Supreme Pontiff Urban VIII brought to the Holy See an intellectualism and an interest in scientific investigation not shared by his immediate predecessors. Galileo knew the man personally—he had demonstrated his telescope to him and the two had taken the same side one night in a debate about floating bodies after a banquet at the Florentine court. Urban, for his part, had admired Galileo so long and well that he had even written a poem for him, mentioning the sights revealed by “Galileo’s glass.”

The presence of the poet pope encouraged Galileo to proceed with a long-planned popular dissertation on the two rival theories of cosmology: the Sun-centered and the Earth-centered, or, in his words, the “two chief systems of the world.”

It might have been difficult for Suor Maria Celeste to condone this course—to reconcile her role as a bride of Christ with her father’s position as potentially the greatest enemy of the Catholic Church since Martin Luther. But instead she approved of his endeavors because she knew the depth of his faith. She accepted Galileo’s conviction that God had dictated the Holy Scriptures to guide men’s spirits but proffered the unraveling of the universe as a challenge to their intelligence. Understanding her father’s prodigious capacity in this pursuit, she prayed for his health, for his longevity, for the fulfillment of his “every just desire.” As the convent’s apothecary, she concocted elixirs and pills to strengthen him for his studies and protect him from epidemic diseases. Her letters, animated by her belief in Galileo’s innocence of any heretical depravity, carried him through the ordeal of his ultimate confrontation with Urban and the Inquisition in 1633.

No detectable strife ever disturbed the affectionate relationship between Galileo and his daughter. Theirs is not a tale of abuse or rejection or intentional stifling of abilities. Rather, it is a love story, a tragedy, and a mystery.

~~Galileo’S Daughter- A Historical Memoir of Science, faith, and love  -by- Dava Sobel

Day 195: Cosmos

The conventional bombs of World War II were called blockbusters. Filled with twenty tons of TNT, they could destroy a city block. All the bombs dropped on all the cities in World War II amounted to some two million tons, two megatons, of TNT—Coventry and Rotterdam, Dresden and Tokyo, all the death that rained from the skies between 1939 and 1945: a hundred thousand blockbusters, two megatons. By the late twentieth century, two megatons was the energy released in the explosion of a single more or less humdrum thermonuclear bomb: one bomb with the destructive force of the Second World War. But there are tens of thousands of nuclear weapons. By the ninth decade of the twentieth century the strategic missile and bomber forces of the Soviet Union and the United States were aiming warheads at over 15,000 designated targets. No place on the planet was safe. The energy contained in these weapons, genies of death patiently awaiting the rubbing of the lamps, was far more than 10,000 megatons—but with the destruction concentrated efficiently, not over six years but over a few hours, a blockbuster for every family on the planet, a World War II every second for the length of a lazy afternoon.

The immediate causes of death from nuclear attack are the blast wave, which can flatten heavily reinforced buildings many kilometers away, the firestorm, the gamma rays and the neutrons, which effectively fry the insides of passersby. A school girl who survived the American nuclear attack on Hiroshima, the event that ended the Second World War, wrote this first-hand account:

Through a darkness like the bottom of hell, I could hear the voices of the other students calling for their mothers. And at the base of the bridge, inside a big cistern that had been dug out there, was a mother weeping, holding above her head a naked baby that was burned bright red all over its body. And another mother was crying and sobbing as she gave her burned breast to her baby. In the cistern the students stood with only their heads above the water, and their two hands, which they clasped as they imploringly cried and screamed, calling for their parents. But every single person who passed was wounded, all of them, and there was no one, there was no one to turn to for help. And the singed hair on the heads of the people was frizzled and whitish and covered with dust. They did not appear to be human, not creatures of this world.

The Hiroshima explosion, unlike the subsequent Nagasaki explosion, was an air burst high above the surface, so the fallout was insignificant. But on March 1, 1954, a thermonuclear weapons test at Bikini in the Marshall Islands detonated at higher yield than expected. A great radioactive cloud was deposited on the tiny atoll of Rongalap, 150 kilometers away, where the inhabitants likened the explosion to the Sun rising in the West. A few hours later, radioactive ash fell on Rongalap like snow. The average dose received was only about 175 rads, a little less than half the dose needed to kill an average person. Being far from the explosion, not many people died. Of course, the radioactive strontium they ate was concentrated in their bones, and the radioactive iodine was concentrated in their thyroids. Two-thirds of the children and one-third of the adults later developed thyroid abnormalities, growth retardation or malignant tumors. In compensation, the Marshall Islanders received expert medical care.

The yield of the Hiroshima bomb was only thirteen kilotons, the equivalent of thirteen thousand tons of TNT. The Bikini test yield was fifteen megatons. In a full nuclear exchange, in the paroxysm of thermonuclear war, the equivalent of a million Hiroshima bombs would be dropped all over the world. At the Hiroshima death rate of some hundred thousand people killed per equivalent thirteen-kiloton weapon, this would be enough to kill a hundred billion people. But there were less than five billion people on the planet in the late twentieth century. Of course, in such an exchange, not everyone would be killed by the blast and the firestorm, the radiation and the fallout—although fallout does last for a longish time: 90 percent of the strontium 90 will decay in 96 years; 90 percent of the cesium 137, in 100 years; 90 percent of the iodine 131 in only a month.

The survivors would witness more subtle consequences of the war. A full nuclear exchange would burn the nitrogen in the upper air, converting it to oxides of nitrogen, which would in turn destroy a significant amount of the ozone in the high atmosphere, admitting an intense dose of solar ultraviolet radiation.* The increased ultraviolet flux would last for years. It would produce skin cancer preferentially in light-skinned people. Much more important, it would affect the ecology of our planet in an unknown way. Ultraviolet light destroys crops. Many microorganisms would be killed; we do not know which ones or how many, or what the consequences might be. The organisms killed might, for all we know, be at the base of a vast ecological pyramid at the top of which totter we.

The dust put into the air in a full nuclear exchange would reflect sunlight and cool the Earth a little. Even a little cooling can have disastrous agricultural consequences. Birds are more easily killed by radiation than insects. Plagues of insects and consequent further agricultural disorders are a likely consequence of nuclear war. There is also another kind of plague to worry about: the plague bacillus is endemic all over the Earth. In the late twentieth century humans did not much die of plague—not because it was absent, but because resistance was high. However, the radiation produced in a nuclear war, among its many other effects, debilitates the body’s immunological system, causing a deterioration of our ability to resist disease. In the longer term, there are mutations, new varieties of microbes and insects, that might cause still further problems for any human survivors of a nuclear holocaust; and perhaps after a while, when there has been enough time for the recessive mutations to recombine and be expressed, new and horrifying varieties of humans. Most of these mutations, when expressed, would be lethal. A few would not. And then there would be other agonies: the loss of loved ones; the legions of the burned, the blind and the mutilated; disease, plague, long-lived radioactive poisons in the air and water; the threat of tumors and stillbirths and malformed children; the absence of medical care; the hopeless sense of a civilization destroyed for nothing; the knowledge that we could have prevented it and did not.

~~Cosmos -by- Carl Sagan

Day 46 : Book Excerpt : Making Starships and Stargates

Ernst Mach, an Austrian physicist of the late nineteenth and early twentieth centuries, is now chiefly known for Mach “numbers” (think Mustang Mach One, or the Mach 3, SR71 Blackbird). But during his lifetime, Mach was best known for penetrating critiques of the foundations of physics. In the 1880s he published a book – The Science of Mechanics – where he took Newton to task for a number of things that had come to be casually accepted about the foundations of mechanics – in particular, Newton’s notions of absolute space and time, and the nature of inertia, that property of real objects that causes them to resist changes in their states of motion.

Einstein, as a youngster, had read Mach’s works, and it is widely believed that Mach’s critiques of “classical,” that is, pre-quantum mechanical, physics deeply influenced him in his construction of his theories of relativity. Indeed, Einstein, before he became famous, had visited Mach in Vienna, intent on trying to convince Mach that atoms were real. (The work Einstein had done on Brownian motion, a random microscopic motion of very small particles, to get his doctoral degree had demonstrated the fact that matter was atomic). Mach had been cordial, but the young Einstein had not changed Mach’s mind.

Nonetheless, it was Mach’s critiques of space, time, and matter that had the most profound effect on Einstein. And shortly after the publication of his earliest papers on General Relativity Theory (GRT) in late 1915 and early 1916, Einstein argued that, in his words, Mach’s principle should be an explicit property of GRT. Einstein defined Mach’s principle as the “relativity of inertia,” that is, the inertial properties of material objects should depend on the presence and action of other material objects in the surrounding spacetime, and ultimately, the entire universe. Framing the principle this way, Einstein found it impossible to show that Mach’s principle was a fundamental feature of GRT. But Einstein’s insight started arguments about the “origin of inertia” that continue to this day. Those arguments can only be understood in the context of Einstein’s theories of relativity, as inertia is an implicit feature of those theories (and indeed of any theory of mechanics). Since the issue of the origin of inertia is not the customary focus of examinations of the theories of relativity, we now turn briefly to those theories with the origin of inertia as our chief concern.

Einstein had two key insights that led to his theories of relativity. The first was that if there really is no preferred reference frame – as is suggested by electrodynamics – it must be the case that when you measure the speed of light in vacuum, you always get the same number, no matter how you are moving with respect to the source of the light. When the implications of this fact for our understanding of time are appreciated, this leads to Special Relativity Theory (SRT), in turn, leads to a connection between energy and inertia that was hitherto unappreciated. The curious behavior of light in SRT is normally referred to as the speed of light being a “constant.” That is, whenever anyone measures the speed of light, no matter who, where, or when they are, they always get the same number – in centimeter-gram-second (cgs) units, 3 10 10 cm/s. Although this works for SRT, when we get to General Relativity Theory (GRT) we will find this isn’t quite right. But first we should explore some of the elementary features of SRT, as we will need them later. We leave detailed consideration of Einstein’s second key insight – the Equivalence Principle – to the following section, where we examine some of the features of general relativity theory.

Mention relativity, and the name that immediately jumps to mind is Einstein. And in your mental timescape, the turn of the twentieth century suffuses the imagery of your mind’s eye. The principle of relativity, however, is much older than Einstein. In fact, it was first articulated and argued for by Galileo Galilei in the early seventeenth century. A dedicated advocate of Copernican heliocentric astronomy, Galileo was determined to replace Aristotelian physics, which undergirded the prevailing Ptolemaic geocentric astronomy of his day, with new notions about mechanics. Galileo hoped, by showing that Aristotelian ideas on mechanics were wrong, to undercut the substructure of geocentric astronomy. Did Galileo change any of his contemporaries’ minds? Probably not. Once people think they’ve got something figured out, it’s almost impossible to get them to change their minds. As Max Planck remarked when asked if his contemporaries had adopted his ideas on quantum theory (of which Planck was the founder), people don’t change their minds – they die. But Galileo did succeed in influencing the younger generation of his day.


~~Making Starships and Stargates- The Science of Interstellar Transport and Absurdly Benign Wormholes -by- James F. Woodward