Compound metaphors are like a multiple punch, hitting the listener repeatedly with metaphoric elements. Where the complex metaphor uses stacked layers to enhance the metaphor, the compound metaphor uses sequential words. The compound metaphor is also known as a loose metaphor.
A live metaphor is one which a reader notices. A dead metaphor is one no-one notices because it has become so common in the language.
Two people walk off a tennis court. Someone asks the loser: "What happened?".
Metabolism
Metabolism is the chemical reactions which keep us alive. It happens in the cells of living organisms.
Reactions catalyzed by enzymes allow organisms to grow, reproduce, maintain their structures, and respond to their environments. The word ‘metabolism’ can also refer to digestion and the transport of substances into and between different cells.
Metabolism is usually divided into two categories. Catabolism breaks down organic matter and harvests energy by way of cellular respiration. Anabolism uses energy to construct molecules such as proteins and nucleic acids.
The chemical reactions of metabolism are organized into metabolic pathways, or cycles, like the Krebs cycle. One chemical is transformed through a series of steps into another chemical by a series of enzymes.
The metabolic system of an organism decides which substances it finds nutritious and which poisonous. For example, some prokaryotes use hydrogen sulfide as a nutrient, yet this gas is poisonous to animals. The speed of metabolism, the metabolic rate, influences how much food an organism will need, and how it is able to get that food.
A striking feature of metabolism is the similarity of the basic metabolic pathways and components between even vastly different species. For example, the set of carboxylic acids that are best known as the intermediates in the citric acid cycle are present in all known organisms, being found in species as diverse as the unicellular bacterium "Escherichia coli" and huge multicellular organisms like elephants. These striking similarities in metabolic pathways are likely due to their early appearance in the evolution of life, and kept because of their efficiency.
Microscope
A microscope is a scientific instrument. It makes small objects look larger. This lets people see the small things. People who use microscopes frequently in their jobs include doctors and scientists. Students in science classes such as biology also use microscopes to study small things.
The earliest microscopes had only one lens and are called "simple microscopes". "Compound microscopes" have at least two lenses. In a compound microscope, the lens closer to the eye is called the "eyepiece". The lens at the other end is called the "objective". The lenses multiply up, so a 10x eyepiece and a 40x objective together give 400x magnification.
Microscopes make things seem larger than they are, to about 1000 times larger. This is much stronger than a magnifying glass which works as a simple microscope.
There are many types of microscopes. The most common kind of microscope is the compound light microscope. In a compound light microscope, the object is illuminated: light is thrown on it. The user looks at the image formed by the object. Light passes through two lenses and makes the image bigger.
The second most common kind are a few kinds of electron microscopes. Transmission electron microscopes (TEMs) fire cathode rays into the object being looked at. This carries information about how the object looks into a magnetic "lens". The image is then magnified onto a television screen. Scanning electron microscopes also fire electrons at the object, but in a single beam. These lose their power when they strike the object, and the loss of power results in something else being generated—usually an X-ray. This is sensed and magnified onto a screen. Scanning tunneling microscopes were invented in 1984.
A fluorescence microscope is a special kind of light microscope. In 2014, the Nobel Prize in Chemistry was awarded to Eric Betzig, William Moerner, and Stefan Hell for "the development of super-resolved fluorescence microscopy". The citation says it brings "optical microscopy into the nanodimension".
Mass
The mass of an object is a measure of the amount of matter in a body. A mountain has typically more mass than a rock, for instance. Mass should not be confused with the related but quite different concept of weight.
We can measure the mass of an object if a force acts on the object. If the mass is greater, the object will have less acceleration (change in its motion). This measure of mass is called "inertial mass" because it measures inertia.
A large mass like the Earth will attract a small mass like a human being with enough force to keep the human being from floating away. "Mass attraction" is another word for gravity, a force that exists between all matter. When we measure the force of gravity from an object, we can find its "gravitational mass". Tests of inertial and gravitational mass show that they are the same or almost the same.
The unit of mass in the International System of Units is the kilogram, which is represented by the symbol 'kg'. Fractions and multiples of this basic unit include the gram (one thousandth of a kg, symbol 'g') and the tonne (one thousand kg), amongst many others.
In some fields or applications, it is convenient to use different units to simplify the discussions or writings. For instance,
Traditional units are still in encountered in some countries: imperial units such as the ounce or the pound were in widespread use within the British Empire. Some of them are still popular in the United States, which also uses units like the short ton (2,000 pounds, 907 kg) and the long ton (2,240 pounds), not to be confused with the metric tonne (1,000 kg).
Mass is an intrinsic property of the object: it does not depend on its volume, or position in space, for instance. For a long time (at least since the works of Antoine Lavoisier in the second half of the eighteen century), it has been known that the sum of the masses of objects that interact or of the chemicals that react remain conserved throughout these processes. This remains an excellent approximation for everyday life and even most laboratory work.
However, Einstein has shown through his special theory of relativity that the mass "m" of an object moving at speed "v" with respect to an observer must be higher than the mass of the same object observed at rest "m" with respect to the observer. The applicable formula is
formula_1
where "c" stands for the speed of light. This change in mass is only important when the speed of the object with respect to the observer becomes a large fraction of "c".
Mercury (planet)
Mercury is the smallest planet in the Solar System. It is the closest planet to the sun. It makes one trip around the Sun once every 87.969 days. Mercury is bright when it is visible from Earth, ranging from −2.0 to 5.5 in apparent magnitude. It cannot be easily seen as it is usually too close to the Sun. Because Mercury is normally lost in the glare of the Sun, Mercury can only be seen in the morning or evening twilight or during a solar eclipse.
Less is known about Mercury than about other planets of our Solar System. Telescopes on the Earth show only a small, bright crescent, and putting a satellite in orbit around it is difficult. The first of two spacecraft to visit the planet was Mariner 10, which mapped only about 45% of the planet’s surface from 1974 to 1975. The second is the MESSENGER spacecraft, which finished mapping the planet in March 2013.