For home canning it is necessary to thoroughly sterilize the containers. In the …

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For home canning it is necessary to thoroughly sterilize the containers. In the past, I have had to boil the jars in a large container. This is dangerous. If I were to moisten the jars and place them in the microwave, would there be enough heat to sterilize them? — CM

While you could sterilize jars in a microwave oven, doing so would be extremely dangerous. Your chances of successfully sterilizing the jars without blowing one of them up is very small. Here is an explanation.

When you place a canning jar in boiling water, what you are really doing is exposing that jar to a water bath at a temperature of 212° F (100° C). Boiling water self-regulates its temperature very accurately, making it a wonderful reference for cooking. Below water’s boiling temperature, water molecules evaporate relatively slowly from the surface of water so that when you add heat to the water, it tends to get hotter and hotter. But once the water begins to boil—meaning that evaporation begins to occur within the body of the water—water molecules evaporate so rapidly that when you add heat to the water, more of it converts into steam and its temperature doesn’t change much. When you boil canning jars for 5 minutes, you are simply making sure that the canning jars sit at about 212° F for about 5 minutes; long enough to kill bacteria in the jars. Since the boiling temperature of water diminishes at high altitudes and lower atmospheric pressures, you must wait longer for your jars to be adequately sterilized if you live in the mountains.

Microwave cooking wouldn’t heat the jars to any specific temperature. As you cooked the jars in a microwave oven, their contents would become hotter and hotter. Even if we ignore the fact that microwave cooking is uneven, so that the temperature inside each jar won’t be uniform, there will be nothing special about the temperature 212° F. If you cook the food long enough, its temperature will reach 212° F, but will then keep rising. As it does, the water vapor in the jars will become more and more dense and its pressure will rise higher and higher. If the canning jar had been properly capped, the metal lid ought to be loose enough to allow this steam to escape. However, the canning system wasn’t designed to handle large amounts of escaping steam and an over-tightened jar might not permit the steam to escape at all. With the steam trapped inside, the pressure inside the jar may become large enough to cause it to explode. Since too little time in the microwave oven will leave the jars unsterilized and too much time in the microwave oven may cause them to explode, I suggest sticking to the tried and true method of sterilizing your jars in boiling water.

I was told by an electrician to use 130-volt bulbs, which he said were outlawed …

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I was told by an electrician to use 130-volt bulbs, which he said were outlawed by the electric bulb makers because they last so long. He said that electricians can buy them and not the public. I found them and have used them for 5 years and he is right! They last forever. Why is that? How do they compare to more energy efficient lights? — J

When you use a bulb designed for 130 volts in a fixture that operates at 120 volts, the bulb’s filament runs at less than its rated temperature. This temperature change has two consequences—one good and one bad. The good news is that operating the filament at less than its normal temperature slows the evaporation of tungsten atoms and prolongs the filament’s life. That’s why your bulbs are lasting so long. The bad news is that incandescent bulbs become much less energy efficient as you lower their filament temperatures. The light emitted by the filament is thermal radiation and its color spectrum and brightness depend almost exclusively on its temperature. These 130-volt bulbs emit redder and dimmer light than a normal bulb and they are significantly less energy efficient as a result. Incandescent bulbs already emit far more invisible infrared light than visible light and operating them at reduced temperatures only makes this problem worse. I recently read the statement “this bulb burns cooler than a normal bulb” on a package of super-long-life bulbs—as though burning cooler was a good thing rather than a serious shortcoming.

As energy becomes more and more precious, making the most of it becomes more and more important. I would suggest saving these 130-volt bulbs for fixtures that are so difficult to reach that you want to avoid changing bulbs at all costs. In more easily accessible fixtures, replacing bulbs is only a minor inconvenience associated with improved energy efficiency. Better still, switch to fluorescent lamps—which are much more energy efficient than even the best incandescent lamps.

What is the chemistry involved with natural dyes adhering to surfaces?

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What is the chemistry involved with natural dyes adhering to surfaces? — AG, Aloha, OR

Unless a chemical reaction binds them permanently in place, dye molecules that are soluble enough to wash into fabrics are equally likely to wash back out of the fabrics later on. To remain in place, the dyes must undergo chemical reactions that attach them to the fibers of the fabric. Some dyes react spontaneously to the fabric molecules but many others need help. The traditional scheme for binding dyes to fabrics involves mordents—relatively colorless chemicals that bind to both fabric and dye, and that hold the two together. Tannic acid and various metal salts have been used as mordents for centuries. They form insoluble compounds that wedge themselves into hollow spaces in the fibers and then bind chemically to the dye molecules. These mordents hold the dye molecules in place in much the same way that technical climbing gear holds rock climbers to the face of a cliff.

How does cathodic protection work?

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How does cathodic protection work? — MM, Dominican Republic

The rusting of damp steel is an electrochemical reaction in which iron atoms in the steel are converted into positively charged iron ions (Fe2+) in the water. However, each iron atom that becomes an ion releases two negatively charged electrons and rusting can only continue if there is a suitable destination for these electrons. Normally, the electrons pass through the steel metal and are used together with oxygen molecules to form negatively charged hydroxide ions (OH–) in the water. Overall, the rate at which the steel rusts is limited by how quickly hydroxide ions can be formed to use up the electrons.

Cathodic protection is a scheme in which a piece of reactive metal, typically magnesium, is connected to the steel to form an electrochemical cell. Magnesium ions (Mg2+) form more easily than iron ions and enough electrons are given up by the magnesium atoms as they become positive ions to completely dominate the hydroxide ion formation process. With nowhere for their electrons to go, the iron atoms can’t become iron ions and rusting can’t proceed. As long as the magnesium metal, often called the “sacrificial anode”, remains intact and connected to the steel, the steel won’t rust significantly.

As an alternative to this approach, some companies use a power supply to pump negative charges onto the steel to prevent it from rusting. Pipeline companies often do this and that action has led to some interesting complications: metal objects that are brought into contact with such a pipeline can be protected against rusting as well. For example, when people chained their bicycles to protected pipelines, the bicycles became part of the protected materials. This may have been good for the bicycles, but it confused the pipeline companies who found that they needed to pump extra charge onto the pipelines to handle the increased load. It was particularly bad when the bicycles accidentally grounded the pipelines and allowed the negative charges to escape.

Can light be bent by electric fields, magnetic fields, and gravity fields? If so…

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Can light be bent by electric fields, magnetic fields, and gravity fields? If so, can these fields be made to make light travel in a circle? — RS

Light consists of electromagnetic waves, meaning that it is composed of electric and magnetic fields. While light isn’t affected by other electric or magnetic fields, it is affected by gravitational fields. Like everything else in our universe, light falls when exposed to gravity. However, because light travels so fast, it’s very hard to detect that it falls. The first observation of light falling in a gravitational field was made during a total eclipse in 1919 and served as dramatic confirmation of the predictions of Einstein’s general theory of relativity. As for light traveling in a circle, this can occur near the surface of a black hole. When light traveling tangent to the surface of the black hole falls at just the right rate, it will orbit the black hole indefinitely.

I recently place a green tomato in the microwave oven. I forgot to turn on the m…

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I recently place a green tomato in the microwave oven. I forgot to turn on the microwave and in the morning the tomato was ripe. Can you explain this? — KH

No. When a microwave oven is off, the cooking chamber contains nothing special at all—just some trapped air and perhaps a little light that enters through the window. Even when it is operating, a microwave oven never produces any ionizing (high energy) radiation so there are no long-term effects such as radioactivity present in the cooking chamber when the oven is off. The tomato was simply sitting in a sealed metal box overnight. Since some fruits ripen faster in sealed environments, perhaps that accounts for your observation.

Does a device that has radio waves and uses ozone and negative ions have the abi…

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Does a device that has radio waves and uses ozone and negative ions have the ability to clean the air in my home? — KTR, Halifax, Nova Scotia

There are many simple electronic devices that claim to clean the air in your home by making negative ions and ozone (if they involve any radio waves, it’s a minor side effect of their internal electronics). The claim is accurate—they do make both ozone and negative ions, and they do clean the air in your home. However, that’s not the whole story. First, ozone may have the “fresh” smell that occurs after a thunderstorm (a potent producer of ozone), but ozone is a powerful oxidizing agent and chemical irritant that’s considered an environmental pollutant rather than a charming scent. The manufacturers are taking a nuisance effect and touting it as a “valuable feature.” Second, the negative charges emitted by these electronic devices attach themselves to dust, ash, pollen, and smoke particles and cause those particles to bind themselves to your walls and furniture. The air really does become cleaner, but every surface in your home becomes dirtier as a result.

If you’re seriously interested in cleaning the air in your home, you are probably better off with a full electrostatic air cleaner. Small home versions of this common industrial workhorse are easy to obtain at a local heating and air conditioning store. Properly designed machines use positive ions to avoid producing ozone and provide a negatively charged surface for the positively charged dirt to stick to so that it doesn’t deposit itself on your walls.

Why do we have time?

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Why do we have time? — KD, McMinnville, Oregon

Time is the fourth dimension, similar to but not equivalent to the three spatial dimensions. With four dimensions in our universe, we need four values to specify the exact location of each event—three values that specify that event’s location in space and one value that specifies its location in time. Space and time are intimately related so that we perceive time in terms of space and space in terms of time. For example, you sense the distance of a remote city by how long it would take you to get there. Similarly, you sense the large separation between two moments in time by how far you could travel between those two moments. But as to “why we have time,” I can only answer that it’s part of the nature of our universe.

Is it possible that time is not just an abstraction but also a sort of resonant …

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Is it possible that time is not just an abstraction but also a sort of resonant force that can be contained and manipulated within a controlled environment? — SK, Cape Town, South Africa

Time is a dimension, much like the three spatial dimensions. Objects and events are located in time, just as they are located in space. Because time is part of the framework in which objects and events exist, and not an object or an event, time can’t be manipulated easily. So the short answer to your question is no, time can’t be contained or manipulated. However, time and space are related and how we perceive the two depends on our velocity—the special theory of relativity. Moreover, time and space can be warped by the presence of mass/energy—the general theory of relativity. Still, the dream of playing with space-time like it was taffy that could be stretch, bent, and folded at will is just that, a dream. It takes an enormous concentration of mass/energy to cause even the most barely perceptible deformations of space-time and even the effects of celestial objects on space-time are limited. Finally, about the expression “resonant force”: a resonance is a motion or action that spontaneously follows a repetitive cycle while a force is a push or a pull, an influence that causes something to accelerate. Thus, the expression “resonant force” is interesting sounding jargon but it doesn’t have any meaning.

How do neon lights work?

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How do neon lights work? — MT, Cement City, MI

A neon light uses a very high voltage to propel an electric current through a low-density gas of neon atoms. These neon atoms are trapped inside a glass tube and the current passes between two metal electrodes at opposite ends of that tube. A high voltage power supply—typically a neon sign transformer—pumps a large number of negative charges onto one electrode and a large number of positive charges onto the other electrode. Because like charges repel while opposite charges attract, there are strong forces pushing the charges from one electrode toward those on the other electrode. Eventually, charges at the two ends of the tube begin to leap off the electrodes and into the neon gas so that they can flow toward one another. Current begins to flow through the tube. As the charges move through the gas, they frequently collide with neon atoms and occasionally transfer some of their energies to those neon atoms. During such an energy transfer, an electron in the neon atom shifts from its normal orbital to a higher energy orbital in which the electron doesn’t normally travel. The electron soon returns to its normal orbital and releases a particle of light—a photon—in the process. Since the most common orbital shift in an excited neon atom releases a particle of red light, a neon light emits a bright, reddish glow.