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INTERNATIONAL SYSTEM OF MEASURES AND PHOTOSYNTHESIS

By SIMO JELAČA, Ph.D.

INTRODUCTION

Professor Dr. Vaclav Smil, a professor at the University of Manitoba in Winnipeg, has published the book Energy, for which Bill Gates says that there is no author whose books he is more excited about than Vaclav Smil’s. Indeed, Professor Smil wrote this book so expertly that it is difficult to find an author in the world who writes better than he does.

Since I also greatly appreciated the content of this book, I thought it worthwhile to present some of its parts, even in an abbreviated version, namely: Energy, International System of Measures, and Photosynthesis.

Note: The Internet automatically increases exponents; please take this into account. The last digits in this text are exponents (superscript and subscript).

ENERGY

The concept of energy has Greek origins and was first presented by Aristotle (384–322 BC) in his work Metaphysics. According to Aristotle, the existence of all objects on Earth is maintained by energy. The word energy represents movement, work, and change. The term practically derives from power and force.

In 1807, Thomas Young (1773–1829) defined energy as the product of mass and the square of velocity, which Albert Einstein (1879–1955) later formulated in his equation:

E = m × c²

INTERNATIONAL SYSTEM OF MEASURES

The international system of measures includes mass, time, electric current, temperature, amount of matter, and intensity of light. These units are used for direct measurements.

The second group of measures includes units that are used every day, namely: area, volume, density, speed, pressure, energy, capacity, and illumination (luminous flux).

There are only three basic units of measurement in use: mass (M), length (L), and time (T), which are necessary for the study of energy.

Surface area (L²), volume (L³), mass density (M/L³), velocity (L/T), acceleration (L/T²), change in velocity per unit time, and force (ML/T²), mass times acceleration, are defined according to Newton’s law of motion. The energy expenditure for work done when a force is applied over a given distance is (ML²/T²). The scientific definition of power is the rate of energy utilization: power equals energy per unit time (ML²/T³).

The SI units are familiar to everyone: for length, the meter (m); for mass, the kilogram (kg); and for time, the second (s). Temperatures are measured in degrees Celsius (°C) and Kelvin (K), electric current in amperes (A), voltage in volts (V), and power in kilowatt-hours (kWh). The amount of matter is measured in moles (mol), and luminosity in candelas (cd).

The kilogram-meter per square second (kgm/s²) is equal to one newton (N). The unit of energy is the joule (J), which is the force of one newton acting over a distance of one meter (kgm²/s²). Power is the flow of energy over a given time (kgm²/s³) and is measured in watts (W). One watt is equal to one joule per second (J/s). Hence, one joule is equal to one watt-second.

The symbols for the SI units of measure are as follows: (deka da = 10¹), 10× magnification; (hekta h = 10²), 100× magnification; (kilo k = 10³), 1000× magnification; etc. (mega M = 10⁶); (giga G = 10⁹); (tera T = 10¹²); (peta P = 10¹⁵); (exa E = 10¹⁸); (zetta Z = 10²¹); and (yotta Y = 10²⁴).

The symbols for the reduced units of the SI system of measures are: (deci d = 10⁻¹); (centi c = 10⁻²); (milli m = 10⁻³); (micro μ = 10⁻⁶); (nano n = 10⁻⁹); (pico p = 10⁻¹²); (femto f = 10⁻¹⁵); (atto a = 10⁻¹⁸); (zepto z = 10⁻²¹); and (yocto y = 10⁻²⁴).

In technology, one unit not included in the SI system is also used: the calorie, the amount of heat required to increase the temperature of one gram of water from 14.5 to 15.5 degrees Celsius (1°C). Since it is a very small unit (1 cal = 4.18 J), the most commonly used unit is 1000 times larger, the kilocalorie (kcal).

The International System of Units has been adopted by all countries in the world, but some countries do not fully apply it. Canada, for example, applies the “Imperial” system in measurements of length, area, volume, and weight, as does the United States, except that the United States also uses it for measurements of speed in miles per hour (mph) and temperature in degrees Fahrenheit (°F).

The units for measuring electrical energy are: for current, the ampere (A), named after André-Marie Ampère (1775–1836); for voltage, the volt (V), named after Alessandro Volta (1745–1827); and for resistance, the ohm (Ω), named after Georg Simon Ohm (1789–1854).

In direct current (DC), electrons flow in one direction, while in alternating current (AC), electrons constantly change amplitude and direction. The standard voltage in North America is 120 V, and in Europe 230 V. A voltage of 120 V cannot normally kill when touched, while a voltage of 230 V can. The pioneer of direct current was Thomas Edison (1847–1931), and the pioneer of alternating current was Nikola Tesla (1856–1943).

PHOTOSYNTHESIS

Photosynthesis in plants is described in great detail in the book Energy. The process of photosynthesis provides oxygen, which ensures the survival of all living things on Earth.

The pigment chlorophyll in plants absorbs sunlight. These cellular organelles give plants their green color. Through this process, six molecules of carbon dioxide (CO₂) and six molecules of water (H₂O) produce one molecule of glucose and six molecules of oxygen:

6 CO₂ + 6 H₂O = C₆H₁₂O₆ + 6 O₂

In reality, the process is much more complex. Dr. Melvin Calvin (1911–1997) was the first to describe the complete process of photosynthesis in 1948, for which he received the Nobel Prize in Chemistry in 1961. In this process of carbon fixation and oxygen production, there is a complex exchange of carbon dioxide and oxygen (photorespiration).

Chlorophylls “a” and “b” are the two dominant pigments formed by radiation, which have approximately similar absorption maxima, the first at 420 and 450 nm and the second at 630 and 690 nm. This means that photosynthesis occurs due to the combination of blue and red energy colors, the visible part of the light spectrum, through pigment absorption, practically without the green and yellow parts of the spectrum, which are reflected during spring and summer and decrease when the pigment begins to break down in autumn.

This also means that photosynthetic activity decreases in autumn to only about 43%. Energy absorption by the pigment causes electron transport (water being the electron carrier and therefore the source of oxygen), which activates an enzyme complex.

The result is the formation of nicotinamide adenine dinucleotide phosphate, one of the most important enzymes in cells, and ATP (adenosine triphosphate), which converts CO₂ into carbohydrates. The proper name for this process is pentose phosphate reduction.

The first step involves one of the biospheric enzymes, ribose 1,5-bisphosphate oxygenase (known as Rubisco). It contains about half of the soluble proteins and catalyzes the conversion of CO₂ into five-carbon ribose 1,5-bisphosphate, forming three-carbon 3-phosphoglycerate.

In the second step, one hydrogen atom added to ATP gives 1,3-bisphosphate. Finally, Rubisco regenerates into triose phosphate or forms carbohydrates and possibly fatty acids or amino acids.

Since plants create oxygen for us, which is essential for our survival, it is very important to protect our forests and every tree in our environment.

Long ago, our famous poet Dr. Jovan Jovanović Zmaj (1833–1904) wrote the following refrain in one of his poems:

“Wherever you find a suitable place, plant a tree there, and the tree is beneficial, and it will reward you.”

In recent years, we have been faced with environmental pollution and huge forest fires in Canada, which are causing enormous material damage and the loss of oxygen that is necessary for all life on planet Earth.

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