How To Build A Time Machine

How To Build A Time Machine: The Real Science of Time Travel by Brian Clegg 


New Scientist, 10 December 2011


At 10pm on Saturday May 7 2005, some 400 people waited at the Massachusetts Institute of Technology for some very special guests to arrive. Time travellers from any and every point in the future had been invited to join the party in Cambridge. “The idea was a simple one that might at first seem trivial but was, in fact rather clever,” Brian Clegg explains in How to Build a Time Machine. “If time travel is possible, why not flag up a certain place and time in history and invite time travellers to attend?” 

The organisers had tried to ensure that the relevant information seeped into the future, and hoped a combination of the internet, print media and TV coverage would do the job. How could any curious, party-loving time traveller resist?

The no-show raises a simple question about the possibility of travelling back in time: We may not yet have the technology to move freely through the ages, but if time machines are going to be built at some point in the future, why hasn't anyone come back to visit us? According to the theory of special relativity, as one moves faster and faster and approaches the speed of light, time slows down. At the speed of light, time stands still. If one could go faster than light, then in principle it is possible to travel back in time. So, Clegg asks, “Where are the time travellers?”

Accelerating beyond light speed to go back to the future requires an infinite of energy, so is practically ruled out (though a huge question mark hangs over faster-than-light neutrinos). However, general relativity does permit the construction of a time machine if space-time is twisted to create a loop, allowing a traveler heading into the future to circle back to an event in his or her own past. This is possible in curved space-time because it’s like a rollercoaster with a loop-the-loop: the cars always go forward but the track circles back to a previous point. 


If a time machine is constructed in the year 2100, for example, it means the loop in space-time starts then: the time machine can be used to go back to 2100 but not to a time before. This feature of time machines has been suggested by physicists J. Richard Gott and Kip Thorne - the former using cosmic strings and the latter, wormholes. Time travel is possible machine when strings cross or wormhole mouths are moved.

Despite its impracticality, Clegg believes it’s never too soon to consider the potential social and ethical impact of a functioning time machine. He devotes a chapter to the classic “grandfather paradox” - travelling back in time to kill your grandfather before he ever meets your grandmother, rubbing yourself out of existence. It was to handle such conundrums that Stephen Hawking suggested the chronology protection conjecture - the laws of physics conspire to prevent time travel to the past on a macroscopic scale.

H G Wells

Though 116 years have passed since H.G. Wells published his novella, The Time Machine, it is only in recent decades that time travel has leapt from the pages of science fiction to those of physics journals.  While Clegg offers an introduction to time travel, unlike the preceding How to Build a Time Machine by Paul Davies or Gott’s Time Travel in Einstein’s Universe, he doesn't offers much new understanding. In surveying the basics he does conclude – somewhat reassuringly – that,  “time travel technology is not something an amateur can cobble together in the garage”, and that when it does happen it will be down to sophisticated science, “subject to checks and safeguards”. In the end, I suppose, only time will tell.

Incoming!

ET Rock

Incoming!:or, Why we should stop worrying and learn to love the meteorite by Ted Nield

New Scientist, 21 January 2011

From AD 218 to 222 the Roman empire worshipped a meteorite. This bizarre episode ended when the transsexual priest-emperor Elagabalus was hacked to bits and hurled into the Tiber. This is just one of the many stories Ted Nield skilfully weaves into his entertaining history of meteorites.

In July 2010, two spectators at a cricket match in Sussex in the south of England witnessed an extremely rare meteor strike. The rock, 12 centimetres long, broke in two when it hit the ground with a piece ricocheting into the chest of one man. Luckily he was unharmed. Nield reckons the "global risk of death by extraterrestrial impact to be a negligible 1 in 720,000". Meteorites pose little threat, but says Nield, "we humans have transplanted into meteorites the geological aliens, the heart of our own times, as we searched them for signs of times to come".

Sleights of Mind

A fascinating look at a new branch of cognitive research: "neuromagic"

Sleights of Mind: What the neuroscience of magic reveals about our everyday deceptions by Stephen L Macnik, Susana Martinez-Conde and Sandra Blakeslee

New Scientist, 20 November 2010

MAGIC, it mystifies and captivates us. We shake our heads in disbelief as coins are conjured out of thin air, as cards are mysteriously summoned from a pack, and as the magician's assistant vanishes before our eyes. Of course, there is no such thing as "magic", so how does magic work? It's a question that neuroscientists like Stephen Macknik and Susana Martinez-Conde are trying to answer. In the process they have conjured up a new branch of cognitive research called neuromagic.

From misdirection and the magical practice of "forcing", to mirror neurons and synaptic plasticity, Sleights of Mind is a spellbinding mix of magic and science. The authors invite us to sip this heady potion as they show us how understanding the myriad ways in which the brain is deceived by magic may solve some of the mysteries surrounding how it works.

“Magic tricks fool us because humans have hard-wired processes of attention and awareness that are hackable,” say the authors. Magicians use your mind’s intrinsic properties against you. In a magical feat of their own, the authors persuaded magicians such as James Randi and Teller from the Las Vegas headline act Penn and Teller to deconstruct tricks so that Macknik and Martinez-Conde could later attempt to reconstruct what is going on inside your head “as you are suckered”.

Magic, say the neuroscientists, could reveal how the brain functions in everyday situations such as shopping. However, it is a stretch to believe, as the authors do, that if you’ve bought an expensive item that you never intended to buy, then you were probably a victim of the “illusion of choice”, a technique magicians use to rob their dupes of genuine choice.

The magician toys with us when he appears to put a coin into his right hand, closes it, waves his left over it, and then opens the right. The coin, which we feel must still be there, has “vanished”. He makes us experience the impossible by disrupting the expected relationship between a cause and its effect.

What we see, hear, and feel is based on what we expect to see, hear and feel due to our experiences and memories. When these expectations are violated the brain takes more time to process data or our attention focuses on the violation. Success or failure for the magician relies on his skill in diverting our attention away from the method and towards the magical effect.

Great magicians, through countless hours of practice, manipulate our attention, memory and causal inferences using a bewildering combination of visual, auditory and tactile methods. The greatest magic show on earth, though, is the one happening in your brain.

Neutrino

Ghost Particle

Neutrino by Frank Close

New Scientist, 6 November 2010

For a moment in the late 1920s, Niels Bohr considered the unthinkable: abandoning the notion of conservation of energy. He wasn't calling for its wholesale rejection, only that it be disregarded whenever a neutron decayed into a proton and an electron, as some energy appeared to go missing along the way.

Wolfgang Pauli, who was wont to damn poor ideas as "not even wrong", came up with a solution he called "a terrible thing" - an unknown particle to account for the missing energy. Since it had to be electrically neutral with little or no mass, it was called the neutrino, the "little neutral one".

In this short and informative book, Frank Close recalls those who had the ingenuity and patience to catch and understand this elusive particle that barely interacts with other matter. Their successors are hunting neutrinos left over from the big bang, and no one knows what story these relics will tell.

The Naked Scientist

Bare Essentials

The Naked Scientist by Chris Smith

New Scientist, 30 October 2010

If you are not a fan of Jamie Oliver, aka the Naked Chef, then the title alone may be enough to put you off this book. But resist the temptation to judge it by its cover. This is science packaged as light entertainment, with flash-facts and bite-sized stories ranging from how fish help pollinate flowers to why booze makes us drunk. Among the more fascinating entries are a study that found that people are less likely to remember brands advertised during violent and sexually explicit programmes, and the possibility that eating curry could help ward off Alzheimer's.

The Naked Scientist is the alter ego of University of Cambridge virologist Chris Smith, who wants to "strip down science to the bare essentials and expose you to what it really is - addictively enjoyable, interesting and occasionally a bit naughty". With Christmas looming, and in search of an audience, Smith bares just enough to pull it off.

The Amazing Story of Quantum Mechanics

Captain Quantum

The Amazing Story of Quantum Mechanics: A math-free exploration of the science that made our world by James Kakalios

New Scientist, 16 October 2010

“EXTRAVAGANT Fiction Today, Cold Fact Tomorrow” was the bold claim of Amazing Stories, the first American magazine devoted to science fiction. Beginning in the 1930s, these sci-fi pulps and comics envisaged that by the year 2000 we would be living in a world with domed underwater cities and travelling in flying cars and by jetpacks. Instead we have mobile phones, laptops and DVDs.

The predictions were off, says James Kakalios, because implicit in the promise of flying cars is the availability of lightweight power supplies capable of producing enormous quantities of energy. In fact, the capacity of batteries to act as reservoirs of energy is limited by the chemical and electrical properties of atoms – and we cannot change the physics of atoms.

This is Kakalios’s cue to explain the key concepts of quantum mechanics and show how these ideas account for the properties of metals, insulators and semiconductors – and how they underlie the magnetic properties of atoms that let us store vast amounts of data on computer hard drives and build MRI scanners that can see inside the human body.

The physicists who developed quantum theory and the fans of sci-fi pulps had one thing in common, says Kakalios, and that is a willingness to suspend disbelief as they accepted the impossible as real. Three such quantum facts were: light is an electromagnetic wave that is actually composed of chunks of energy; matter is composed of particles that exhibit a wave-like nature; and both light and matter have a property called spin that can only have certain values.

Having provided the reader with these counter-intuitive notions, Kakalios looks at the problems they solved. To help explain Planck’s discovery of the quantum, the photoelectric effect, the quantum atom, wave-particle duality, Schrödinger’s wave equation, the probabilistic interpretation of the wave function, the uncertainty principle and more besides, comic-loving Kakalios enlists a legion of superheroes, from Superman to Dr Manhattan.

In addition to his bright-blue appearance, Jon Osterman aka Dr Manhattan, appears to have gained control of his quantum- mechanical wave function. This, the starting point for Kakalios’s highly readable presentation of quantum ideas, give him the ability to alter his size at will, to teleport himself and others from one place to another, and to experience the past, present and future simultaneously.

The scientist as a world- changing hero is an apt description for the physicists who developed quantum mechanics, Kakalios believes. He has a point. The discoveries by a handful of physicists back in the 1920s and 1930s of the rules that govern how atoms interact with light and each other continue to shape and change the world we live in.

Why Beliefs Matter

A Matter of Faith

Why Beliefs Matter: Reflections on the nature of science by E. Brian Davies

New Scientist, 7 August 2010

Albert Einstein once asked, does the moon exist when no one is looking at it? Such questions had been the preserve of philosophers, but with the discovery of quantum mechanics in the 1920s they became legitimate queries for physicists, too.

Niels Bohr, one of the founders of quantum mechanics, did not believe that science grants us access to an objective reality and insisted that the task of physics was not to find out "how nature is" but only "what we can say about nature". Einstein, on the other hand, maintained an unshakeable belief in a reality that exists out there. Otherwise, he said, "I simply cannot see what it is that physics is meant to describe".

Einstein based his view of quantum mechanics on his belief in an independent reality - the moon does exist when no one is looking at it. In contrast, Bohr used the theory to construct and underpin his belief that the atomic realm has no independent reality. The two agreed on the equations but disagreed on what they meant.

"Scientists, like everyone else, have beliefs," writes distinguished mathematician E. Brian Davies in Why Beliefs Matter. He is not only referring to religious beliefs but to philosophical ones, too. While religious beliefs can be easy to leave at the laboratory door, philosophical beliefs are much harder to sideline.

Some mathematicians, for instance, subscribe to a Platonic view in which theorems are true statements about timeless entities that exist independent of human minds. Others believe that mathematics is a human enterprise invented to describe the regularities seen in nature. The very idea that nature has such regularities which render it comprehensible is itself a belief, as is the idea that the world we perceive is not some sort of delusion or practical joke.

The title of Davies's book, significantly, is a statement, not a question. For him, beliefs do matter. Davies offers a series of snapshots of how various philosophical views inform science, rather than a systematic inquiry into the nature of belief. Along the way he discusses the scientific revolution, the mind-body problem, machine intelligence, string theory and the multiverse. The result is a wide-ranging, thought-provoking meditation rather than a populist read. Beliefs, it seems, are a serious business, and they come in all shapes and sizes.

"At the highest level, beliefs become world views, fundamental beliefs that we use to evaluate other beliefs about the world," says Davies. World views can be evaluated, compared and changed, but you cannot avoid having one. Davies is a self-proclaimed pluralist. That is, he believes that humans have a limited mental capacity and will always need a multiplicity of ways of looking at the world in order to understand it. There may be two or more equally valid and complementary descriptions of the same phenomenon, he says - not unlike the concept of wave-particle duality in quantum mechanics. That does not mean that all world views are equally good - some simply don't hold up under the scrutiny of experiment.

The scientific revolution that began in the 16th century was a triumph of rationality and experiment over the superstition and speculation of the Middle Ages. Even so, nearly 40 per cent of Americans believe that God created humans some time within the last 10,000 years.

World views are not founded on logic, so the most that one can demand is that they should be consistent with what science has discovered. Yet, as the writer C. S. Lewis noted, some arguments are impossible to refute. "A belief in invisible cats cannot be logically disproved," he said, although it does "tell us a good deal about those who hold it".

Energy, the Subtle Concept

Elusive Stuff

Energy, the Subtle Concept: The Discovery of Feynman’s Blocks from Leibniz to Einstein by Jennifer Coopersmith

New Scientist, 17 July 2010

MOST of us have a vague idea of what energy is, if only because we have to pay for it. We know that it is the E in Einstein's famous equation, E=mc2, and all of us have an opinion about the pros and cons of nuclear energy. For William Blake's devil in The Marriage of Heaven and Hell, energy was "eternal delight", yet Newton never fully appreciated the importance of a concept that was rarely used until the 19th century.

So, what is energy? Easy to ask the question but, as Jennifer Coopersmith shows in Energy, the Subtle Concept, finding the answer was a messy and tangled affair, involving plenty of argument and controversy. It's a tale of persecuted genius, of royal patronage, of social climbers and dreamers, of rich men and poor men, a foundling, entrepreneurs and industrialists, lawyers, engineers, a taxman, a spy and a brewer. Some were showered with honours, others neglected until long after death.

The concept of energy is hard to grasp because it is something that cannot be directly observed. It was only in the early 19th century that it was even recognised as a distinct physical quantity. Since then it has played a vital role in the development of science and technology. Its importance lies in the fact that it possesses the very rare property of being preserved. Energy cannot be created or destroyed; it can only be converted from one form to another. So fundamental is this property to nature that it is enshrined, in more sober scientific terms, as the first law of thermodynamics.

The first step on the long road to understanding the true nature of this relationship had been taken in the 1800s by Benjamin Thompson, an Anglo-American physicist, inventor and soldier of fortune. While supervising the boring of new cannons Thompson realised that heat might be a form of motion rather than a special weightless substance called "caloric". Most remained unconvinced, largely because Thompson was a notorious opportunist and spy. The turning point came in the form of experiments performed, in the 1840s, by English brewer and amateur scientist James Prescott Joule, who introduced the term thermodynamics.

The conservation of energy is arguably the most important law in physics. But what exactly is being conserved? Are some forms of energy more fundamental than others? You will have to read the book to find out. Coopersmith sets out to answer such questions and to explain the concept of energy through the history of its discovery. This is neither a straightforward narrative nor one for the faint-hearted. Those not put off by the odd bit of mathematics, will be well-rewarded by dipping into this book.