Cosmology Feed

September 28, 2008

Quantum Suicide and The Large Hadron Collider

Stern-Gerlach Experiment
Stern-Gerlach experiment. Source: Wikipedia Commons. Licensed under GNU Free Documentation License version 1.2.

Quantum mechanics is a theory that describes the behavior of objects at the atomic scale. The effects of quantum mechanics are typically observable only at this small scale, and not at larger ones, except in unusual or contrived situations.

Electron Spin

Electrons have a property called spin that may be measured in relation to an arbitrary axis. The name is somewhat misleading. It's not quite the same concept as a ball rotating around an axis but there are some useful similarities. Since an electron has an electric charge, its spin causes it to interact with a magnetic field, deflecting the electron's path in a manner similar to the way a charged sphere's course would be altered. An electron can have its spin measured by passing it through a magnetic field. If electrons were truly spinning spheres, a beam of electrons would spread out smoothly when passed through a shaped magnetic field since each rotating sphere would take on an arbitrary spin alignment.

However, what is actually observed is amazing and counter-intuitive. The 1922 Stern-Gerlach experiment showed that spin is quantized and only two values are observed - denoted up and down.

Standard Interpretation

In the standard Copenhagen interpretation of Quantum Mechanics, the electron does not have a definite spin until a measurement is made, and the quantum wave function collapses to a definite value. Schrödinger's Cat is a famous thought experiment which was originally conceived by Austrian physicist Erwin Schrödinger as a critique of the Copenhagen interpretation. In a variation of this thought experiment, one imagines that a cat is placed in a box with a flask of poison and a device that can measure electron spin.

If a single electron that is passed through the device is measured with spin up, the flask of poison is released and the cat expires. If the spin is down, the cat survives. There is a 50 percent chance of either outcome. If the box is sealed so that it is impossible to determine the state of the experiment from outside, the cat will exist in a superposition of states to the outside world with equal probability of it being alive and dead. It's not that the cat actually exists in one state or another according to the Copenhagen interpretation. The cat has become entangled in the quantum wave function describing the contents of the box and truly exists in a superposition of both states.

Quantum Suicide; Many Worlds
iStockphoto / Sirin Buse.

Quantum Suicide

However, in the Many-Worlds interpretation of Quantum Mechanics, two different worlds exist - one in which the cat remains alive, and another in which the cat has perished.

A thought experiment called Quantum Suicide has been crafted as a hypothetical test of the Many-Worlds interpretation. In this experiment, an observer takes the place of the cat and the experiment is performed many times. In some worlds, the observer perishes, but his conscious experience continues in the worlds in which he survives. He will never observe his own death. The observer perishes in half of the worlds, but it does not appear that way from his point of view. After repeating the experiment as many times as necessary to satisfy his curiosity, the observer concludes that the Many-Worlds interpretation is correct.

With the Large Hadron Collider shut down for two months due to a malfunction, some have suggested with tongue-in-cheek that the Quantum Suicide experiment is being conducted in real time with our own world. In some parallel universes, the LHC creates stable black holes which destroy the Earth. We only remain conscious to observe this in universes where that doesn't happen. In those universes, events happen that prevent the LHC from creating those kinds of black holes.

While the LHC's troubles are more likely explained by mundane problems, the idea behind the Quantum Suicide thought experiment is still an intriguing one.


September 22, 2008

Searching for the Higgs Boson

Higgs Boson Production
The Higgs Boson may be produced through the decay of two gluons. Source: Wikipedia Commons. Licensed under GNU Free Documentation License, Version 1.2.

The Large Hadron Collider's Search

The Higgs boson is the only particle left that has not yet been observed by experimental research in the Standard Model of particle physics which lists some 40 species of elementary particles. One of the goals of CERN's Large Hadron Collider, situated beneath the border between France and Switzerland, is to search for this particle when it reaches full operation.

The Higgs boson is a component of the proposed Higgs field. Even in completely empty space, the Higgs field has a value that is non-zero. It is theorized that this non-zero value gives mass to other elementary particles that do in fact have mass.

How Does Mass Arise?

But how can one particle give rise to mass in another particle? This would seem at first glance to involve circular reasoning. The Exploratorium gives a great analogy here:

Imagine you're at a Hollywood party. The crowd is rather thick, and evenly distributed around the room, chatting. When the big star arrives, the people nearest the door gather around her. As she moves through the party, she attracts the people closest to her, and those she moves away from return to their other conversations. By gathering a fawning cluster of people around her, she's gained momentum, an indication of mass. She's harder to slow down than she would be without the crowd. Once she's stopped, it's harder to get her going again.

One reason that the Higgs boson has not yet been observed is because of the predicted large amount of energy necessary to create it. Generally, physicists believe that the Higgs boson will have a mass between 114 and 1,000 GeV / c2. The LHC will be able to operate at up to 7,000 GeV  / c2 on two beams.


September 16, 2008

Animals Survive Experimental Exposure to Open Space

Tardigrade. Source: Wikipedia Commons. Licensed under Creative Commons Attribution ShareAlike version 3.0. reports that tiny 8-legged animals were able to survive in open space during an experiment performed on a European Space Agency spacecraft. Tardigrades, more commonly called water bears, are similar to the brine shrimp Sea-Monkeys.

The Foton-M3 spacecraft carrying the experiment was launched by the European Space Agency in September 2007 and exposed the creatures to the extreme environment of space. Many of the Tardigrades were able to withstand the exposure to vacuum, ultraviolet radiation and cosmic rays.

The results of the experiment lend support to the panspermia hypothesis - that seeds of life may be able to travel between planets and throughout the universe by a number of possible mechanisms.


September 01, 2008

LHC Nearing Full Operation, May Produce Black Holes

CMS Higgs Event
Source: CMS Media/CERN

The Large Hadron Collider (LHC) at CERN continues on target to ramp up to full operation after a second and final test of the beam synchronization systems was completed on Friday, August 22, 2008.

Scientists are excited about the possibility that the collider will produce unstable, short-lived black holes or even dark matter. Physicists Steven Giddings and Michelangelo Mangano have ruled out the potential for dangerous, stable black holes to be created in a paper entitled Astrophysical implications of hypothetical stable TeV-scale black holes published in the journal Physical Review D on August 15, 2008.

The first attempt to circulate a beam of particles is set for September 10, 2008 and will be webcast live.

August 28, 2008

The Fermi Paradox. Why Are We Alone In The Universe?

The Fermi Paradox
© / geopaul

Where Are They?

Nobel prize-winning Italian physicist Enrico Fermi asked the question "Where are they?" regarding the question of life existing elsewhere in the universe. If one assumes the mediocrity principle - that the development of life on earth is typical in comparison to the rest of the universe - we should see evidence of other life. The Fermi paradox is the contradiction between estimates of the number of extraterrestrial civilizations and a corresponding lack of evidence of these civilizations - both physical and radio (the Great Silence).

It's obvious that civilizations can exist - we are one. Why not others?


  • The universe is extremely old. Its current age is estimated at approximately 13.73 billion years
  • The number of stars in the visible universe is extremely large - approximately 5 x 1022.
  • Some of these stars will have habitable planets which develop intelligent life that can produce radio signals.
  • Interstellar travel is possible, and some civilizations desire to colonize stars.

More intelligent estimates of the Drake Equation have been possible with recent advances in astronomy and astrobiology. One estimate in the July 2000 edition of Scientific American suggests the number of civilizations that have existed in our galaxy in the past is 12 billion, with 1,000 of them still transmitting radio evidence of their existence.

Despite those assumptions, limited radio searches of the skies for nearly 50 years have found no evidence of extraterrestrial life. And, it would take only one civilization that desires so between 5 and 50 million years to colonize the entire galaxy - a blink of an eye compared to the age of the universe. So where are they?

Possible Solutions

Clearly there must be something wrong with assumptions that have been made. Some possible resolutions to the Fermi Paradox are:

  • A Great Filter drastically limits the number of civilizations in the universe. Life faces existential risks which are difficult to overcome. For example, the development of the ability to communicate by radio occurs at roughly the same time as the development of nuclear weapons. Professor Nick Bostrom claims that the lack of evidence of extraterrestrial life is a positive sign for the outcome of our own existence.

  • One or more of our assumptions is wrong. Perhaps we're not searching in the right way. Before the invention of radio, for example, the only way to search for life would have been optically. Perhaps neutrinos or some other communication method is used instead.

  • Transcendence - Life passing through a singularity stage may discover a way to exit the universe, or find more meaningful ways of existing. Maybe we are boring and they have no interest in making contact or communicating with us.

  • Perhaps we are living in a simulation.

  • The Zoo hypothesis - we are being isolated intentionally.

  • Perhaps abiogenesis occurs less frequently than current assumptions and we really are alone.

What do you think?


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August 02, 2008

White House advised of pending NASA announcement regarding "potential for life" on Mars

Update 8/5/2008: NASA has issued a press release which indicates the potential discovery of perchlorate on Mars, a chemical which may make Mars less habitable than previously thought. You can follow the Mars Phoenix team's twitter log here.


Aviation Week is reporting that the Bush Administration's Presidential Science Advisor's office has been advised of information that NASA plans to release sometime between mid-August and September 2008 concerning the habitability of the Phoenix landing site and the potential for life on Mars. While not directly pointing to evidence of life currently or in the past on Mars, the information is apparently "far more provocative" than previous announcements confirming the presence of water.

Although the original mission was scheduled to end in late August, NASA recently announced that the Phoenix Mars Lander mission will be extended through September 30, 2008.

This information will be of concern to Oxford professor Nick Bostrom, because of his recent argument regarding the Fermi paradox and the implications that the discovery of extraterrestrial life would have for the human species.

Chris K. Haley, Subscribe Get free RSS or email updates here. 

July 22, 2008

Speculations on Gödel's Incompleteness Theorems, the Halting Problem, and The Simulation Argument

Fermi Paradox
© / David Marchal

Kurt Gödel

Kurt Gödel was a mathematician whose 1931 seminal work was the proof that all formal mathematical systems of sufficient complexity are necessarily incomplete. In other words, there are mathematical statements within these systems that are true, but which can never be proven within the system itself. Gödel proved this by showing that statements can be created which state that they can never be proven within the formal system. While these statements are in fact true, they can't be proven so - if they could, by definition they would not be true!

An analogy is the sentence "This sentence is false". This sentence cannot be a true statement, because if it were, we would have to believe what it states - that it is false. Similarly, it cannot be a false statement, because if it were, it would be true.

Nick Bostrom

Nick Bostrom is the Director of the Future of Humanity Institute at Oxford who has authored a Simulation Argument. Essentially, it states that:

Unless one of the following statements is true,

  • The human species goes extinct before reaching a posthuman stage.
  • Humans never become capable of running (or desire to run) computer simulations of their history.

then we are most likely living in a simulation now.

Turing Machines and the Halting Problem

The halting problem is a question in computability theory which asks if an algorithm can be found that decides whether a program (a Turning machine) will finish, or run forever, once given a description of such a program and a finite amount of input. Alan Turing proved in 1936 that a general algorithm to solve the halting problem for all possible program-input pairs cannot exist. The ideas within Gödel's incompleteness theorems are quite similar to those presented by the halting problem.


Suppose that the universe that we live in is in fact a simulation, and it is being simulated by the equivalent of a Turing Machine. What are the ramifications of the halting problem and Gödel's incompleteness theorems in this regard? The "Scientific and technological approaches" section of the Simulated Reality entry in Wikipedia has some interesting speculations on software glitches, Easter Eggs, limitations on processing power, and the Heisenberg uncertainty principle.

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February 13, 2008

Boltzmann Brain Paradox

Digital Brain
© Sebastian Kaulitzk

Random Fluctuation Created Universe

Ludwig Eduard Boltzmann was an Austrian physicist who made important contributions to the area of statistical thermodynamics. He lived in the last half of the 19th century and proposed that the low-entropy (high order) universe that we live in is the result of a random fluctuation in a larger, higher entropy (lower order) metaverse.

Quantum Fluctuations

Although Boltzmann's proposal was made in advance of quantum mechanics, his idea is similar to modern day theories that the universe arose from a quantum vacuum fluctuation. Quantum mechanics predicts that particles can spontaneously arise from the vacuum if they are short-lived. Even in a perfect vacuum, pairs of particles and anti-particles are constantly being created and destroyed. This is possible because the total energy of the particle anti-particle pairs is zero.

In fact, the total energy of the universe appears to be zero [Stephen Hawking, A Brief History of Time, chapter 8]. Particles have positive energy, and the negative energy represented by the gravitational field of the entire universe appears to be exactly enough to cancel out the positive energy of the particles.


This idea leads to the Boltzmann Brain Paradox. In a metaverse that is larger than ours, random fluctuations of the size to create a universe such as our own will happen. Due to the size and number of particles in such a universe, these fluctuations will be exceedingly rare. The anthropic principal - the fact universes will only be observed when they are hospitable to observers - makes the amount of time between such fluctuations meaningless. These fluctuations could be happening every quadrillion years, or once every googolplex number of years. Fluctuations of a much smaller magnitude that simply create one fully formed brain for a brief amount of time should be happening with enormously higher frequency than universe-creating fluctuations. Such brains would be the smallest possible creations that would give rise to a sentient observer and are called Boltzmann Brains. The fact that such brains do not appear to exist is called the Boltzmann Brain Paradox.

There are a number of ways out of this paradox. One of the base assumptions could be false. Perhaps there is no metaverse or such quantum fluctuations do not happen on large scales.

Or, it possible that the concept of the Boltzmann Brain is true and you are the only sentient observer in the universe right now, complete with false memories of a life which did not exist. False inputs to your brain only make it appear that there are other observers with you. If true, it's possible that you will cease to exist in just a ...

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