What Causes the Aurora Borealis ?

The aurora appears as a curtain, an arc or a spiral, usually following the lines of Earth’s magnetic field. Most displays are green, but strong occurrences can be red, violet, and white. For most of human history, the colors were a source of mystery. Northern cultures created legends about the lights, often associating them with life after death. The Inuit believed the spirits of their ancestors were dancing across the sky, and in Norse mythology, the aurora was a bridge of fire connecting the gods to the heavens. But by the 1880s, scientists suspected a connection between the northern lights, as they are also known, and the Sun.

The temperature above the surface of the Sun is millions of degrees Celsius, causing frequent and violent collisions among gas molecules. Electrons and protons thrown free by the collisions hurtle outward from the Sun’s rotation and escape through holes in the magnetic field. Solar wind carries the charged particles, most of which deflect off Earth’s magnetic field. However, near the North and South Pole, the magnetic field is weaker, allowing some particles to enter the atmosphere. When the charged particles from the Sun strike the atoms and molecules in Earth’s atmosphere, they excite those atoms. An excited atom is one whose electrons move to high-energy orbits, and in the process the atom releases a particle of light, or photon. Different gases in the atmosphere give off light of different colors. Oxygen causes a green display and nitrogen produces red or blue colors. We perceive the collisions between solar particles and atmosphere gases as the northern lights. Many tourists trek to the northern and southern poles of Earth to catch a glimpse of the auroras, now considered one of the seven wonders of the natural world. And even though science can explain the oncemysterious phenomenon, the dazzling display of lights still provokes magical thoughts of dancing ancestors and bridges to the world beyond.

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What Causes Volcanic Lightning?

On March 10, 2010, Eyjafjallajökull volcano, a caldera in Iceland covered by an ice cap, erupted. It sent plumes of clouds across most of Europe and the Atlantic Ocean. Photos of the eruption show lightning originating and ending in the cloud of ash that hovered over the volcanic opening. The largest volcanic storms are similar to supercell thunderstorms that spread across the American Midwest. But while those thunderstorms are fairly well understood, volcanic lightning still remains mysterious. The remote location of volcanoes and infrequent eruptions make volcanic lightning difficult to study. In general, lightning occurs through the separation of positively and negatively charged particles. Differences in the aerodynamics of the particles separate the positive and negative. When the difference in charge is great, electrons flow between the positive and negative regions. A lightning bolt is a natural way of correcting the charge distributi...

Is Cold Fusion Possible?

Italian inventor Andrea Rossi really wants us to believe in cold fusion. He claims that his Energy Catalyzer, or E-Cat, a liter-sized device he designed, can output three times as much energy as it draws via low energy nuclear reactions, or LENRs As hydrogen passes over an electrified nickel-based catalyst, hydrogen nuclei supposedly fuse to the nickel, transmuting the metal into copper and releasing heat in the process. If we could harness that heat, the process could furnish cheap electricity banishing greenhouse simultaneously production gases-all creating any harmful waste. There's only one problem: Cold fusion is almost certainly a myth. Backers aside, has yet to perform a truly independent test of his E-Cat; in most tests by third parties, Rossi handled the materials or was involved in some way. Critics argue that Rossi's device doesn't produce nearly as much energy as he claims and that his suggestion of building factories for large...

What Is the Moon Illusion?

The Moon seems larger when it is near the horizon than when it is high in the sky, a phenomenon called the Moon illusion. Although recognized for centuries—the horizon Moon was important to early civilizations that functioned according to the Moon’s cycle—this ancient phenomenon has only recently been explained. Early astronomers believed the Moon at the horizon was physically closer to Earth than when it was high in the sky, and the closeness meant a larger Moon. However, Newton’s description of the Moon’s orbit showed the contrary to be true. The Moon Is actually closest to the observer at its zenith, or when it is high in the sky, but the difference is so small that it is negligible anyhow. Others theorized that the Moon illusion was caused by refraction when light rays passed through more of Earth’s atmosphere. Today, scientists guess that the illusion occurs not externally, but through a trick of our brains. Optical illusions p...

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