"Every time you look up at the sky, every one of those points of light is a reminder that fusion power is extractable from hydrogen and other light elements, and it is an everyday reality throughout the Milky Way Galaxy." -Carl Sagan

(This post is coauthored by Dr. Peter Thieberger, Senior Physicist at Brookhaven National Laboratory.)

A cheap, clean, efficient and virtually limitless source of energy would be just what our world needs right about now. The cheap sources -- coal, oil, and gas -- are dirty, destructive, and limited, while the clean sources -- wind and solar -- are expensive and inefficient. Nuclear power is abundant and efficient, but with the dangers of radioactivity (and Fukushima still fresh in people's minds), it clearly isn't an ideal solution either. What would be ideal, rather than the current nuclear fission power we use, would be nuclear fusion, where lighter elements are fused together into heavier ones. Unlike a nuclear fission reaction, neither the original reactive material nor the products are radioactive in most instances of nuclear fusion.

Video credit: an old Soviet documentary , featured in Trinity and Beyond

Nuclear fusion is responsible for the most powerful release of energy ever generated on our planet: the Tsar Bomba, above. No other known reaction (that doesn't involve antimatter) is capable of generating as much energy from a given amount of matter as nuclear fusion can, in the entire Universe.

Of course, a reaction like the Tsar Bomba is not what we want when it comes to meeting our energy needs. Perhaps more pointedly, we'd like to have controlled nuclear fusion, where we can control the rate of fusion and harness practically all of the energy generated from the reactions. To accomplish this, all you'd need is two atomic nuclei whose initial states have more total mass than the final fused nucleus will -- which is possible thanks to binding energy -- and you can, in principle, have nuclear fusion between those two elements.

Image credit: David Darling.

Nuclear fusion happens all around us in the Universe: it's the very process that powers every single star visible to your naked eye in the sky.

Image credit: Wally Pacholka of TWAN; click for an amazing panorama.

This even includes our own Sun! By combining hydrogen atoms into heavier isotopes and then into helium, one mere milligram of hydrogen fusion in the Sun generates as much energy as over 300 pounds of TNT! Of course, this is hard to do: you need the temperature in the core of your star to rise above 8 million Kelvin in order to fuse hydrogen into helium, and you'd need temperatures even higher than that (on the order of 100 million Kelvin) to fuse helium into heavier elements!

Image credit: Phil Anderson, St. Rosemary Educational Institution.

All of our successful attempts at generating nuclear fusion here on Earth require similarly high pressures and/or temperatures to those found at the core of each and every fusion-powered star. In mainstream physics, there are three types of setups verified to create nuclear fusion, all of which are working towards the (metaphorical) holy grail goal of the breakeven point. If you can reach and go beyond that point, you'll produce more usable energy from your setup than you put into it in order to create the fusion reaction.

But recently, attempts to create nuclear fusion with a relatively low-pressure, low-temperature experiment -- what's commonly known as cold fusion -- have been making a lot of noise.

Image credit: Focardi and Rossi with their e-Cat, retrieved from Brian Wang.

In the past, claims of cold fusion have been unable to be scientifically reproduced under controlled conditions, but it is universally recognized that if cold fusion could be achieved, it would be amazingly useful as a clean, cheap, safe, abundant energy source. Last week, this site expressed some healthy skepticism about the latest sensational claims concerning Andrea Rossi's claimed cold fusion device: the Energy Catalyzer, or e-Cat.

Briefly, here's what the e-Cat claims to do.

Image credit: Schematic of Rossi's e-Cat reactor, retrieved from peswiki.com.

They start with nickel powder -- ordinary nickel as found on Earth -- and combine it with hydrogen gas under modest pressure. You will see claims that this is high pressure, but in the world of physics, the claimed 25 times our normal atmospheric pressure (or even 100 or 1000 times) isn't anything spectacular. (For comparison, inertial confinement fusion compresses hydrogen to be about a factor of 20 denser than solid lead to obtain fusion, in line with well-understood physics.)

The nickel and hydrogen mix, under pressure, is heated through simple electrical currents in the presence -- it is claimed -- of a "secret mix" of catalysts.

Image credit: retrieved from nickel + hydrogen = energy.

And it's claimed that a nuclear fusion reaction takes place between the nickel and the hydrogen, producing copper! The relevant part of the periodic table of the elements is shown below.

Image credit: retrieved, highlighted and cropped from ptable.com.

This claim is made for two reasons:

There is anomalous heat/energy being generated by the device, as evidenced by water that has been heated and/or boiled by the e-Cat. This heat is measured by outside observers and cannot be accounted for, completely, by the external power input.

A sample of the claimed products of the reaction was made available, which contained some nickel powder, but about 10% of the sample was copper, claimed to be completely generated from an initial sample that was 100% nickel.

Right here, this very site claimed that these results were probably faked, and now we're going to show you the physics of why these claims are definitely untrue.

Image generated using the free graphing software at nces.ed.gov.

There are five known stable isotopes of Nickel, and here on Earth they are found in the percentages shown in the chart above. These isotope ratios are the same on Earth as they are in meteorites and in the Sun, and are pretty universal to any sample of nickel naturally found here on Earth.

If you want to create copper from any of these elements by adding a proton (hydrogen nucleus) to them, here are the reactions you're looking for:

58 Ni + 1 H → 59 Cu*,

Ni + H → Cu*, 60 Ni + 1 H → 61 Cu*,

Ni + H → Cu*, 61 Ni + 1 H → 62 Cu*,

Ni + H → Cu*, 62 Ni + 1 H → 63 Cu*,

Ni + H → Cu*, 64Ni + 1H → 65Cu*.

That doesn't look so prohibitive, does it? Of course, there is the fact that you've got to overcome the tremendous Coulomb barrier (the electrical repulsion between nickel and hydrogen nuclei), which -- according to our knowledge of nuclear physics -- requires temperatures and pressures not found naturally anywhere in the Universe. Not in the Sun, not in the cores of the most massive stars, and (to the best of our knowledge) not even in supernova explosions!

From both an astrophysics and a nuclear physics standpoint, we can conclude that these reactions are not happening, and that they're certainly not happening at the incredibly low energies claimed by the e-Cat team. Let's look at the astrophysics first.

Image credit: SOHO/LASCO consortium, ESA / NASA, retrieved from beyondweather.ehe.osu.edu.

This is the Sun, known to contain a significant abundance of nickel, and to primarily be composed of hydrogen. Given the pressures and temperatures present in the Sun, you might expect any or all of the fusion reactions mentioned above to happen. But when we look at the Sun, we see that there is a much larger amount of nickel than copper, with no evidence that any of the Sun's nickel has, over the 4.5 billion years of the Sun's life, been fused into copper; there's something like more than 100 times as many nickel atoms as copper atoms.

Image credit: Catherine Michelle Deibel's Ph.D. Thesis.

But it is worth noting that there are stars that form copper from nickel, but they do not do it by adding protons. When our Sun runs out of hydrogen fuel, it will expand, becoming a red giant, and begin burning helium atoms into the element carbon. While the Sun will be capable of creating a few elements heavier than carbon, such as nitrogen, oxygen, and (probably) neon, that's the end of the line for the Sun. But significantly more massive stars can go farther.

Image credit: the one-minute-astronomer.

If a star is at least eight times as massive as our Sun, not only are copious amounts of neon produced, but the pressures and temperatures are high enough to burn neon into still heavier elements. By combining a helium nucleus with the element neon, these very massive stars can produce the element magnesium plus a free neutron. Those neutrons, since they're uncharged (and do not have to contend with the repulsive Coulomb force between atomic nuclei), can interact with a nickel nucleus, which can capture it. Two of these cases are very important: where Nickel-62 and Nickel-64 capture a neutron. Here's why.

Add a neutron to Ni-62 (or Ni-64) and it becomes Ni-63 (or Ni-65). But both of these isotopes are unstable, and will β-decay, forming copper. More specifically, they undergo the reactions shown below.

62 Ni + 1 n → 63 Ni* → 63 Cu + β - + γ + ν ̅ e ,

Ni + n → Ni* → Cu + β + γ + ν ̅ , 64Ni + 1n → 65Ni* → 65Cu + β- + γ + ν ̅ e ,

where ν ̅ e is an anti-electron neutrino. This is vital for copper, because these are the only stable isotopes of copper in the Universe, and because this is the primary way the Universe's copper is made!

Image credit: NASA, ESA and Allison Loll/Jeff Hester.

When these stars then go supernova, they eject these elements out across the Universe, and that's where -- to the best of our knowledge -- all of the copper on Earth comes from. And it comes in a 70-30 ratio: 70% copper-63 and 30% copper-65, naturally.

In other words, even the most massive stars, at the incredible pressures and temperatures found at their cores, cannot fuse nickel and hydrogen nuclei together. From the point of view of astrophysics, the claims of cold fusion do not hold up.

But who knows; maybe there is some "magic secret catalyst" that could make this reaction happen? It couldn't be anything like an atom, an atomic nucleus, an electron, a neutrino, or anything else present in the Sun, because then it would happen there, too. (However, it's worth noting -- at this point -- that Focardi's original experiment claimed to have no catalyst, which means Ni + p → Cu should have definitely happened in the Sun for at least one of the isotopes, changing the isotopic abundance from what is observed.)

Image credit: Rossi, Kullander, Essen and the e-Cat, retrieved from energydigital.com.

But it isn't happening, and the above picture pretty much proves that it isn't happening. Here's why. Remember the conceivable nuclear reactions we talked about, above, for nickel fusing with hydrogen? The problem is, for all of the five isotopes, the product is unstable (which is why they were marked with asterisks), and will radiate. Let's finish the reactions, and show how:

58 Ni + 1 H → 59 Cu* → 59 Ni + β + + γ + ν e ,

Ni + H → Cu* → Ni + β + γ + ν , 60 Ni + 1 H → 61 Cu* → 61 Ni + β + + γ + ν e ,

Ni + H → Cu* → Ni + β + γ + ν , 61 Ni + 1 H → 62 Cu* → 62 Ni + β + + γ + ν e ,

Ni + H → Cu* → Ni + β + γ + ν , 62 Ni + 1 H → 63 Cu* → 63 Cu + γ,

Ni + H → Cu* → Cu + γ, 64Ni + 1H → 65Cu* → 65Cu + γ.

So three of these hypothetical reactions -- which, remember, represent over 95% of the total initial nickel -- will decay back into nickel, releasing β+ particles (i.e., positrons), gamma rays and neutrinos, while the other two will produce stable copper, along with γ-radiation.

First, let's take a look at what positrons do.

Image credit: PET physics.

Since they're being created inside of normal matter -- which is made up of nuclei and electrons -- these positrons will annihilate with electrons, producing two high-energy photons of 511 keV of energy (kilo-electronVolts) apiece, or two gamma rays (γ-rays).

In other words, in short order, all of the possible fusion reactions will produce γ-radiation. While the γ-rays from these reactions can come in a wide variety of energies in theory, from as small as a few dozen keV up to a maximum of a few MeV (Mega-electronVolts), we are guaranteed that we will at least be producing copious amounts of 511 keV γ-rays. And what does it take to stop γ-radiation?

Image credit: Cameco.com.

Unlike α-particles, your skin won't do it. Unlike β-particles, a thin sheet of aluminum (or even lead) foil won't do it. For very energetic particles like γ-rays, you need a lot of shielding to protect you from them, because the only way to shield yourself from γ-rays is to put enough material between the source of these γ-rays and yourself to sufficiently reduce the intensity.

It normally takes a substantial amount of material -- whether it's a foot of lead, a meter of concrete, or a few meters of water -- to sufficiently protect you from high-energy γ-rays. For example, in large nuclear fission reactors, there's usually a big setup like this.

Image credit: Peter Barendse at Boston University.

Why is all this necessary? A huge amount of shielding is needed so that this high energy γ-radiation doesn't irradiate you. Without any shielding, γ-rays can travel through many kilometers of air unimpeded. And you know what happens when you get hit by large amounts of γ-rays?

Image credit: Stan Lee, Jack Kirby, Paul Reinman and Artie Simek.

Right, you'll turn green with giant muscles!

Or, perhaps, if you don't live in a comic book, you'll start experiencing the effects of acute radiation syndrome, an extremely nasty way to go. So in these e-Cat experiments of Rossi and Focardi, how much shielding are they using, and how good is that shielding against γ-rays?

Image credit: Rossi's e-Cat, retrieved from the blog Nickel + Hydrogen = Energy.

With only 2" of lead shielding, it is true that more than 96% of the γ-rays will be blocked. But that is horrible for nuclear physics; if more than 3% of the γ-rays were to get through the shielding, they would be easily detectable with even primitive equipment, and deadly to a human bystander within minutes. But the expected γ-radiation was not detected -- even with sensitive equipment -- during these tests!

So what's been going on here? After all, they claimed to produce copper from nickel and hydrogen, and they claimed to have detected large amounts of excess heat that cannot be explained by the input power alone. Have the laws of nuclear physics been circumvented on both the reactants side and on the products side?

Image credit: okokChina.com's copper powder.

Or was the whole thing faked, with natural copper powder added to natural nickel powder and passed off as "products" of the reaction? (Remember, from above, that copper is naturally found with 70% Cu-63 and 30% Cu-65 isotopic abundance.) What do you suppose was the ratio of copper "created" by this e-Cat? Analysis of the "final sample" showed that it contained the exact same 70-30 split of copper-63 to copper-65 found in nature. If you're not convinced that this is very suspicious as well, you may also want to consider that even if 100% of the initial nickel-62 and nickel-64 was fused with hydrogen into copper, you'd get less than half the copper (4.5%) in your products compared to what was claimed (10%). Furthermore, -- assuming hydrogen was the fuel -- no more than 1% of the total final sample could have been transmuted into copper-65 given any conceivable chain reaction involving nickel nuclei and hydrogen, compared to the claimed 3%.

In fact, the entire "observed" effect of having your system continue to generate heat even after it's been turned off is remarkably simple to rig.

Much easier than hiding a person inside a mechanized chess machine, don't you think?

With other companies now trying to capitalize off of this speculative, unverified and highly dubious claim, it's time for the e-Cat's proponents to provide the provable, testable, reproducible science that can answer these straightforward physics objections. Independent verification is the cornerstone of all scientific investigation and experiment, it's how we weed out all sorts of errors from miscalibration to contamination, and how we protect ourselves from unscrupulous swindles. Given everything that we know, as others also demonstrate (thanks, Steven B. Krivit), it's time to set aside the mirage of Nickel + Hydrogen fusion and get back to work finding real solutions to our energy and environmental problems.