The Travelers’ Temperature Predicaments (2)

Temperature measurement is very important to a whole range of areas and activities: science, scientific research, manufacturing, medicine and travel. Many European, Asian and African businessmen and tourists often travel to the USA and UK. These countries have not adopted the use of the modern metric system of measurement i.e. the SI system.

The accepted base SI unit of temperature is the Kelvin. A change of 1K is the same as 1 degree Celsius. As the degree Celsius is a convenient, easy to grasp in every – day – life metric unit, therefore both units are used in parallel. The Kelvin is used by scientists and engineers and the degree Celsius by everybody else worldwide. There are however, two prominent exceptions: the USA and UK who commonly use the Fahrenheit scale.

Daniel, Gabriel Fahrenheit, a German physicist was born in 1686 in Gdansk, Poland. The concept of the thermometer for measuring temperature changes is credited to Galileo. Fahrenheit is known for inventing the alcohol and mercury thermometers. His temperature scale is based on affixing 32º for melting point of ice and 212º for the boiling point of water under normal atmospheric pressure. The interval between two affixed points is being divided into 180 equal parts (the degrees Fahrenheit). The Fahrenheit scale was generally in use by English speaking countries up until 1970.
Travelers to the USA and UK are often faced with the problem of how to efficiently convert the temperature in the degree Fahrenheit to the temperature expressed in the degrees Celsius without making a mistake and with a sufficient approximation.

The conversion formula “Fahrenheit to Celsius” is:

ºC = 5/9 (ºF – 32º); read:

“In order to express the temperature in the degrees Celsius, I need to divide 5 by 9 and the result multiply by the temperature in Fahrenheit lowered by 32º”.

Quite awkward, isn’t it?

A much simpler way to remember and easier method to do mentally is to memorise the four following steps:

ºF→→→ºC : “Subtract 32, divide by 2, add 10% ( or 1/10) of the result and add 1% of the total”.

Let us see how it works:

E.g. 1: 98 ºF (your normal body temperature) →→→66 →→→33 →→→36.3 →→→36.7 ºC (rounded off to one decimal place).

E.g. 2: 102 ºF (your possible body temperature) →→→70→→→35→→→38.5→→→38.9 ºC

(High, pay a visit to the doctor!).

E.g. 3: 68 ºF (pleasant, refreshing outdoor temperature)→→→36→→→18→→→19.8→→→20 ºC

If you in a good mood, hum these four steps before the travel: “su-di-a-a”, “su-di-a-a”, “su-di-a-a”…!

Have a nice trip and keep warm!

Wacek

PS.: Have you read my former article: “The Travelers Temperature Tips”?

If so, you will be able to find the answer to the following puzzle:

FORGETFULNESS

A student solving a problem on transfer of heat found a correct temperature change. However, he presented the answer without a unit. As it turned out, it did not matter whether he gave the temperature in the degrees Fahrenheit or the degrees Celsius. The answer remained the same. What temperature was it?

Wind Anemometers – How to Measure Wind Speed Accurately

For a science that is constantly in the lives of everyday folk, wind speed measurement certainly manages to keep out of the public eye. The measuring of wind speed happens to be an important part of a number of everyday technologies. Of course there is meteorology, the measuring of weather phenomena, that wholly depends on the gauging of wind speed; but a surprising number of other everyday specialties depend on wind speed measurements too, chief among them being aviation and marine and navigation, stability management in skyscrapers, environmental sciences and disaster management. Wind measurement is done with a device known as a wind anemometer; though it might be argued that that is a redundancy since anemometer comes from the Greek Anemos = wind.

Any device that measures wind speed is bound to sense the pressure of it too. For this reason, many anemometer designs are successful when used as pressure meters too in addition. A version of anemometer is known to have existed since around 1450. The modern wind anemometer though, has been around for more than a century and a half now; the first successful design was one that used a structure with four arms fanned out, each one with a cup attached that caught the wind and spun the structure. The inventor, Dr. John Robinson, held the impression when he made his invention that any cup anemometer would share the characteristic that it would spin at a third of the speed of the wind blowing past it, no matter what size it was built to be. Researchers took his word at its face for quite a while before it was discovered that the size of design used always affected the results. Researchers who had used the inventor’s figures for their calculations for years had to start over from scratch.

Cup anemometers, these simple devices, are remarkably accurate machines today nevertheless; the best examples can approach a 99% accuracy level, and still be no more expensive than about $1000. But the cup anemometer is still a mechanical technology that is prone to maintenance lubrication issues, friction, mechanical damage and ice formation. There are competing technologies that attempt to eliminate the problems seen in the mechanical design. One of the most popular wind anemometer technologies in use today is the ultrasonic kind. The principle of the ultrasonic design is this: the speed of sound depends on the speed and the direction of the air that it passes through. A headwind slows sound down, and a tail wind speeds it up. An ultrasonic wind anemometer fires high-frequency sound pulses back and forth between two receivers. If the pulse takes more time travelling in one direction than the other, that is a sign that the slower trip had a headwind working against it. The time differential helps calculate the wind speed. You’ll find these in use on tall buildings, on weather buoys and at weather stations.

Another wind anemometer design that is particularly ingenious is the constant-temperature anemometer. A thin wire held between two electrodes is heated up electrically to hold a constant temperature. A sensor measures the amount of current needed to hold the temperature at ambient temperature levels. Any loss of temperature that is faster than would be explained by the ambient temperature levels would have to come from wind speed. This is a particularly accurate method of measurement of wind turbulence. However, like the laser measurement method below, this can be a quite inexpensive device to buy and maintain.

Ultrasonic and constant temperature anemometers may be accurate enough for most purposes; but laser Doppler anemometers offer extremely tight accuracy. A laser anemometer uses two laser beams; one that travels through a sealed and clean pathway, and one that travels through exposed air. The beam that travels through the exposed air encounters dust particles that are borne along at the speed of the wind at the point. The laser bounces off those dust particles, and measures by Doppler shift the speed at which the particle has been traveling. The Doppler shift is compared to what is measured for the beam traveling through the sealed tube and a relative measurement is made.

It would appear from these descriptions that anemometers always need to be large and permanent installations; as it happens though, small and inexpensive handheld versions with digital displays exist for use by field researchers and trainer pilots. The most striking feature of these is the way they recognizably use nothing other than the same mechanics and structures of the professional devices, only miniaturized for handheld use.

Time Travel – A Possibility or Just the Stuff of Science Fiction?

It’s been written about in hundreds of books, the subject of fantasy for everyone at one time or another, and the government has actually devoted research at one time or another on the subject. If you do a search on the Internet for time travel you will find millions of entries on it, and hundreds of websites fully devoted to talking about it. Wouldn’t it be cool if you could travel back in time? You could correct mistakes you’ve made in your life, study any period of time that interests you, not to mention build a financial empire on your foreknowledge of events. Beginning with H.G. Wells’ The Time Machine, the concept of time travel has been one of the main staples of science fiction. Some of my favorite reads are David Gerrold’s The Man Who Folded Himself and The Light of Other Days by Stephen Baxter and Arthur C. Clarke.

So is it really possible to travel in time?

First of all we are all already time travelers in the sense that time moves forward, and at the same apparent rate of speed, for all of us. There seem to be no obstacles in physics to accelerating the forward momentum of time in one way or another. Cryogenics is a concept much written about as one method of “forward” time travel; lowering the body temperature to a little above absolute zero to nearly stop the metabolism as a way to sleep away millennia. The practical hurdles to this put any possibility of this far into the future. Although simpler organisms have been successfully frozen and returned, the human body is too complex to yet survive the process because of water crystallization and other factors. Another method of accelerating time is time differentials due to the relativistic effects of high velocity.

According to Einstein’s Theory of Relativity, as an object approaches the speed of light one of the effects is time dilation. As a relativistic object’s speed increases the passage of time slows for it in relation to a non-moving object. Take for example a spacecraft traveling at 10% of the speed of light, or 18,628 miles per second. If this imaginary spacecraft maintained this speed consistently for 24 hours (according to our clocks back home), then at the end of that 24 hours only about 23 hours, 53 minutes would have passed onboard the spacecraft. Much higher speeds to within a fraction of a percent of the speed of light have to be achieved to get a really noticeable effect. Take that same spacecraft and accelerate it to .999999 light speed (or to 186,281.81 miles every second) and something really bizarre happens, achieving something more like time travel. If you take that spacecraft out on a joyride at that speed for 24 hours of your traveler’s time and return home, you will find that almost two years have past on Earth.

In actuality, this has been observed in experiments done when atomic clocks were sent on jetliners to observe the effects of time dilation. The difference was observed as predicted, helping to support Einstein’s theories. Naturally the difference was small, measured in nanoseconds. Unfortunately for any aspiring time travelers, the kind of speeds needed for relativistic effects are still well outside our technology. The fastest spacecraft yet launched were the Helios spacecraft sent to study the sun in the 70s. They achieved speeds of about 158,000mph, or about 44 miles per second; this is about .02% light-speed, still not close to relativistic speeds.

And what about the possibility of travel back in time?

This makes great material for science fiction, but the data here doesn’t seem promising. Physicists have been able to envision certain circumstances under which time travel MAY be allowable under the laws of physics, but the energy levels and exotic matter requirements seem to be well beyond anything we are likely to achieve anytime soon. Some have suggested that wormholes may be bridges to other universes, distant parts of this universe, or other times. Wormholes remain a theoretical concept, neither proven nor dis-proven to exist. It seems that for all practical purposes the universe has (at least temporarily) denied us the opportunity to revisit our past directly. So let us turn to a discussion of what the possibilities would be if time travel did exist.

First of all we must look at the fact put forward by modern physics that space and time are related aspects of the topology of our universe. In other words, our universe consists of the three observable dimensions of space and one of time. Putting together a theory that explains the existence of our universe required combining time and space into one continuum. Assuming this to be true, it follows that there should be a parallel measurement in space equivalent to measurements in time. It may seem nonsensical to talk of measuring space in seconds or time in miles, but the two are tied together through the speed of light. Therefore it follows that to convert one second of time into distance, we simply look at how far light travels in one second. That would be approximately 186,282 miles or three quarters the distance to the moon. This means that traveling one second back in time would be equivalent to traveling nearly the distance to the moon. Then there is the fact that a change in temporal position would mean having to adjust for the motion of the earth, sun and galaxy as they rotate and revolve. A lot harder than it looked, huh? Ok, let’s pretend we overcome this obstacle and achieve real, meaningful time travel. Could you go back in time and kill your grandfather early in his life, assuring that you will never be born? Time travel is full of paradoxes such as this. For the most part this can be overcome by incorporating quantum mechanics into the concept of time travel, and branching realities.

Quantum mechanics is a field of theory which developed in the first quarter of the twentieth century through the work of Niels Bohr, Pauli, Planck, Heisenberg, and Schrodinger. It’s basic tenets are that at a fundamental level matter exists as a cloud of uncertainty and probability. Heisenberg’s Uncertainty Principle states that one cannot measure both the position and momentum of an elementary particle because the act of observation changes the outcome. In this branch of physics cause and effect is said to break down and one can only state the probability of something being true. The most famous example of what quantum mechanics means in the real world was given as a thought experiment by Erwin Schrodinger and is known as Schrodinger’s Cat. Here it follows:

A cat is placed in a sealed box. Attached to the box is an apparatus containing a radioactive nucleus and a canister of poison gas. This apparatus is separated from the cat in such a way that the cat can in no way interfere with it. The experiment is set up so that there is exactly a 50% chance of the nucleus decaying in one hour. If the nucleus decays, it will emit a particle that triggers the apparatus, which opens the canister and kills the cat. If the nucleus does not decay, then the cat remains alive. According to quantum mechanics the unobserved nucleus is described as a superposition (meaning it exists partly as each simultaneously) of “decayed nucleus” and “undecayed nucleus”. However, when the box is opened the experimenter sees only a “decayed nucleus/dead cat” or an “undecayed nucleus/living cat”.

The paradox of this experiment is that the cat is said to be both dead and alive until someone opens the box. (*No cats or animals of any kind were harmed in the writing of this article). This paradox can be resolved if we say that instead of both being true in one reality, that reality actually branches into two. In one universe the cat is alive and in the parallel universe it is dead. In this way our universe is constantly splitting into alternate universes in which every possibility is encompassed. This also solves the paradoxes of time travel. When our time traveler returns and makes changes in the past he would be creating an alternate universe without destroying the other. In this way, as he or she continued to make changes, our time traveler would never be able to return to their original timeline, although he could create one similar to it with the right changes. All of the possibilities and repercussions of a scenario such as this are spectacularly presented in the science fiction novel The Man Who Folded Himself, by David Gerrold.

In summary, time travel is a highly entertaining concept for science fiction, and actually holds some plausibility in certain concepts of modern physics. But as a practical application, it is not likely to become a part of our lives anytime soon. Of course, not being a time traveler myself, I cannot speak with certainty.

Time will tell.