How to Destroy the Universe (29 page)

The story subsequently broke in the popular press, leading to Podkletnov being dismissed from Tampere University, presumably because they viewed his work as flaky and damaging to their reputation. Shortly afterward, Podkletnov withdrew his scientific paper on the subject from publication. Various groups around the world at universities and private research organizations—and even NASA—have tried to replicate his results, but without success. These attempts were not helped by the fact that Podkletnov was less than forthcoming in giving away the precise details of his experimental set-up.

Nevertheless, in interviews given to the press since, Podkletnov maintains that his device demonstrates a true antigravity effect. He continues to develop the idea with other theoretical and experimental physicists. Some scientists think Podkletnov is dishonest or crazy, or both; others say he's just plain wrong. But if he is right—and there's at least an outside chance that he is—then his findings will change everything from the exploration of deep space to how we travel to work in the morning.

• The light elements

• Star formation

• Red giants

• Supernova

• Planet formation

• The anthropic principle

• Space for man

When singer Joni Mitchell stated in her 1970 song “Woodstock” that “We are stardust” she may not have been aware that her lyrics were 100 percent scientifically accurate. Human beings, all other life on Earth, and the very planet itself, are made of material forged in the hearts of stars and then scattered across space in enormous stellar explosions known as supernovae.

The Big Bang in which our Universe was created brought into existence space, time and all of the matter that we see around us. But matter can take a variety of forms. The material that our everyday world is made
up of—known to scientists as baryonic matter—is divided into various chemical elements. A chemical element is defined by the number of positively charged proton particles in the nucleus that lies at the heart of every one of its atoms. For example, carbon has six protons while oxygen has eight. And these elements can be converted into one another by nuclear reactions (see
How to turn lead into gold
).

Nuclear reactions come in two types: fission, which involves chopping up large atoms; and fusion, which involves joining together smaller ones. In the Big Bang there were no heavy elements, only primitive subatomic particles, so the only reaction possible was fusion. But fusion requires high temperatures in order to slam protons together hard enough to overcome the mutual repulsion they feel as a result of their positive electrical charge. In the Big Bang fireball the temperature was only hot enough to do this for the first few hundred seconds. And this only gave enough time for the formation of the two lightest chemical elements, hydrogen and helium. The Universe after the Big Bang was composed of about 75 percent hydrogen and 25 percent helium, with a smattering of heavier elements. Studies of primordial gas clouds in deep space have confirmed these proportions. Life requires much more complicated elements than just hydrogen and helium, including oxygen and carbon, but also nitrogen, calcium, chlorine, potassium, iron
and many others. These have to be cooked up in another kind of cosmic nuclear furnace—the cores of stars.

The first stars are thought to have formed from collapsing cosmic clouds about 200 million years after the Big Bang. Stars are formed from giant clouds of hydrogen gas drifting in space. These clouds are very rarefied, with densities of no more than a hundred atoms of gas per cubic meter, but they can span hundreds of light years in size, and contain hundreds of thousands of solar masses of material. Tiny irregularities in the density of such a cloud lead to instabilities as over-dense regions begin to collapse under their own gravity. As they collapse and become denser, their gravity increases, causing them to pull in more mass still, increasing their density further in a positive feedback loop.

This ball of gas is known as a protostar. As it collapses, squashing itself, the temperature inside starts to rise. When the core has reached about 15 million °C, nuclear fusion reactions can ignite, combining nuclei of hydrogen to make helium. Energy floods out and a new star is born. The energy heats the gas in the star's outer layers, raising its pressure until the outward force is sufficient to halt the star's inward collapse under
gravity. Astrophysicists call this balance point hydrostatic equilibrium. Once a star is in hydrostatic equilibrium, it enters the phase that will take up the bulk of its life. How long this lasts depends on the star's mass. For a star like our own Sun, it will be about 10 billion years. Heavier stars, however, live fast and die young. A star 10 times the mass of the Sun will shine for only 10 million years. The maximum size permissible for any star is about 100 solar masses, at which point the copious radiation streaming out from the star blows it apart.

Once a star has run out of hydrogen fusion fuel in its core, a change begins. The core begins to contract. The contraction heats the core to the point where it's hot enough to ignite fusion of helium—which the star has just spent millions or billions of years producing a great deal of—fusing three helium nuclei together to make a nucleus of carbon. The extra energy produced by helium fusion inflates the star's outer surface to 10 times its previous diameter, forming a red giant. Meanwhile the star continues to burn hydrogen in a thin shell around the outside of the core. Sooner or later the supply of helium runs out too and the process repeats. Now carbon ignites in the core and, via a range of fusion reactions, forms elements such as neon, sodium, magnesium and oxygen. Meanwhile helium burning
continues in a shell surrounding the core, with hydrogen burning in a shell outside that. This process continues until the core is made of iron, beyond which the binding energy per particle in the nucleus decreases, making nuclear fusion inefficient. At this point, there is nothing to act as nuclear fuel in the core and it begins to cool. The cooling lowers the pressure. Now the weight of the star pushing down makes it shrink, and it implodes.

What happens next depends on how heavy the star is. Stars up to about 10 times the mass of our own Sun undergo cycles of oscillation as fuel material from the outer shell sinks down into the core. For example, helium produced by the hydrogen burning shell sinks down until the temperature is high enough for it to ignite. This puffs the star up again until it runs out of fuel once more and falls back into collapse. These oscillations become more violent as the star uses up the last of its fuel. The process culminates in one final outward sigh that flings off the star's envelope to form a diffuse and ghostly cloud of gas called a planetary nebula. At the center of the nebula is a bright pinprick of light: a dense white dwarf star.

For stars larger than 10 solar masses, the process is not as serene. Such a star will grow to immense proportions
during its death throes, becoming what is known as a red supergiant. The collapse of a supergiant's core is unstoppable—until, that is, the core density becomes so great that electrons and positrons merge together to form a super-dense blob of neutrons, known as a neutron star. The quantum mechanical pressure inside the neutron star suddenly halts the collapse, causing a “bounce” that catapults the star's outer layers off into space in a cataclysmic explosion known as a supernova, with the neutron star left behind as a remnant at its heart.

Both supernovae and the formation of planetary nebulae serve to scatter the chemical elements cooked up inside a star out across space. Subsequent generations of stars can then form from these element-enriched clouds. When these stars die and scatter their material into space the resulting clouds are enriched further. Once the interstellar medium had acquired enough heavy elements, new stars could also develop a belt of dust and debris circling their equators, known as a protoplanetary disc. Gradually the particles of dust stick together to form small rocks. Once big enough, these chunks of material develop gravitational fields strong enough to attract more material, creating mountain-sized chunks and eventually planets. Close to the raging heat of a newly ignited star, rocky planets form
as all the gases and other volatile materials get blasted away by the intense radiation. Further away, the temperature is much lower. Here, the volatile materials condense to form gas giants, such as Jupiter and Saturn.

We know that on at least one planet in our Solar System a chemical process that we call “life” has emerged. Life is based on a wide range of chemical elements, all of which were forged in the hot cores of long-dead stars. The proliferation of life on Earth has actually helped in the understanding of how these elements came to be. In the 1950s, the British astrophysicist Fred Hoyle pointed out that in order for there to be enough carbon in the Universe for carbon-based life (such as that found on Earth) to exist, there must be a mechanism within physics for carbon to be mass-produced inside stars.

Making carbon is tricky. It has a total of 6 protons and 6 neutrons in its nucleus. Helium—the material inside stars that the carbon has to be made from—has 2 protons and 2 neutrons. So three helium nuclei need to combine to make each nucleus of carbon—and it is unlikely for three particles to come together at a single point in space. However, two helium nuclei can combine to make the element beryllium—with 4 protons and 4 neutrons. The beryllium can then join
with a third helium nucleus, but this shouldn't form carbon because it's unstable—it's got too much energy and breaks apart in a few nanoseconds. Hoyle predicted that there must exist a so-called “resonance” of carbon, an energized state of the carbon nucleus. It would then be energetically more favorable for the berylliumhelium cluster to turn into this energized state of carbon and then drop back down to become an ordinary carbon nucleus, than for the cluster to break apart. And, sure enough, when experimental physicists went away and looked for Hoyle's resonance, they duly found it. It was cited as an example of what's become known as the “anthropic principle”—the idea that the laws of physics must be such as to allow carbon-based life-forms to emerge in the Universe because otherwise we would not be here!

Some physicists regard this as a powerful principle. Others resent the fact that it's even been elevated to principle status, preferring to use the term anthropic reasoning. One of the leading objections to the anthropic principle is that it suggests, in a slightly religious way, that “someone” has somehow fine-tuned the laws of physics in our Universe for our benefit. Some physicists believe the so-called many worlds interpretation of quantum theory (see
How to live forever
) could offer a way out of this predicament. Many worlds
insists that ours is not the only universe that exists, but just one in a sprawling network of parallel universes that physicists have dubbed the multiverse. In this multiverse view, universes with all possible combinations and permutations of the laws of physics must exist. This would mean that the specific set of laws that prevail in this universe—our Universe—are effectively determined at random.

Once you look at it this way, it's really no surprise that we are here to observe physics to be the way it is. Rather than just one universe in which there's just one chance for the conditions to be right for life, there is a virtually infinite number. Inevitably, in some of these the conditions will, by chance, facilitate life—with no need for God-like fine-tuning. And only in these universes—of which ours is clearly one—will there be physicists scratching their heads and wondering why.

• What is MRI?

• Going functional

• Tell me the truth

• Dream watchers

• Mind control

No longer the preserve of self-proclaimed psychics and frauds, real mind reading has been made possible by physics. It is done using a medical scanning technique known as functional magnetic resonance imaging (fMRI), which was originally designed to diagnose and monitor the growth of tumors and other disorders in the brain. Now fMRI has found a new niche revealing exactly what people are thinking.

The first ever magnetic resonance image (MRI) was taken in 1973 and the first studies of its use on humans took place in 1977. MRI is preferred over usual X-ray imaging because it's less harmful (X-rays are a very high-energy form of radiation), making it especially
suited to the treatment of patients with chronic illnesses, such as cancer, who require many scans. MRI works by measuring radio waves given off by water molecules in the body. It does this by using a magnetic field to stimulate the protons that lie at the center of each hydrogen atom inside the water molecules. First, a huge magnetic field is applied to the body. It causes positively charged proton particles in the hydrogen nucleus to snap into alignment with the field. This happens because protons, and many other subatomic particles, have what's called a “magnetic moment,” which can be thought of as the magnetic field generated by the proton's positive charge as it moves.

Just as an ordinary magnet placed in an external magnetic field tends to align its north and south poles with the south and north poles, respectively, of the field (think of how a compass needle moves), so the magnetic moments of the protons are all made to swing into line by the magnetic field of the MRI scanner. The field strength needed to do this is enormous. The largest commercial scanners in operation today generate magnetic fields of up to 7 Tesla: 200,000 times the strength of Earth's natural magnetic field. The hefty magnets needed to generate such fields are the main reason why MRI scanners usually take up a whole room. It's also why no metal objects are allowed anywhere near an MRI scanner—even paperclips can become highly dangerous missiles when accelerated in
such an intense field. Forget an MRI scan if you have a pacemaker fitted. And don't take magnetic media such as credit cards near one, as they will almost certainly be wiped.