His plays were written in the strict style of Greek drama. They were in verse and no violence could be performed on stage. The plays had to be set away from normal life in Athens, either by telling stories about the gods or by being set, like "The Persians", in a far-away place. Aeschylus' work has a strong moral and religious emphasis. The "Oresteia" plays were about man's position in the universe in relation to the gods, the laws of the gods, and punishment from the gods.
Fifty years after Aeschylus' death, the comic playwright Aristophanes praised him in "The Frogs". Aeschylus is a character in the play and says that his "Seven against Thebes" "made everyone watching it to love being warlike" (line 1022); with his "Persians", he says he "taught the Athenians to desire always to defeat their enemies" (line 1026–7). He says that his plays helped the Athenians to be brave and virtuous (line 1039ff).
Euripides
Euripides (c. 480 BC–406 BC) was an Ancient Greek writer from Athens who wrote about 90 plays. Only 18 of his tragedies have survived complete, more than all other surviving ancient Greek tragedies put together. A nineteenth play, "Rhesus" is sometimes thought to be by Euripides, but not all classicists agree on this.
Euripides was the last of the three greatest Ancient Greek writers of tragedies, the others being Aeschylus and Sophocles.
Chard
Chard (also known as Swiss chard, silverbeet, perpetual spinach, or mangold) is a vegetable. It is in the same family as spinach, "Amaranthaceae".
Half-life (element)
The half-life of a substance is the time it takes for half of the substance to decay. The word "half-life" was first used when talking about radioactive elements where the number of atoms get smaller over time by changing into different atoms. It is now used in many other situations where something declines exponentially, like the time it takes for a drug in the body to be half gone. A Geiger-Muller detector can be used to measure the radioactive half-life; it is the time when the activity is half of the original.
Half-life depends on probability because the atoms decay at a random time. Half-life is the expected time when half the number of atoms have decayed, on average. Carbon-14 has a half-life of 5,730 years. Taking one atom of carbon-14, this will either have decayed after 5,730 years, or it will not. But if this experiment is repeated again and again, it will be seen that the atom decays within the half life 50% of the time.
Radioactive isotopes are atoms that have unstable nuclei, meaning that the nucleus of each atom will decay after enough time has passed. Their nuclei are unstable because the arrangement of protons and neutrons in them are unsteady. This decay, which means they change into completely different types of atoms. This is known as radioactive decay. When they decay, they release particles such as alpha particles, beta particles, gamma rays. Sometimes they decay by fission, which means to break into pieces, to make smaller nuclei. For example, a radioactive carbon-14 atom releases a beta particle to become nitrogen-14. As an example of fission decay, a fermium-256 atom can split into xenon-140 and palladium-112 atoms, releasing four neutrons in the process.
For example, uranium-232 has a half-life of about 69 years. Plutonium-238 has a half-life of 88 years. Carbon-14, which is used to find the age of fossils, has a half-life of 5,730 years.
After ten half-lives, about 99.9% of the atoms have decayed into different atoms, so only 0.1% of the original atoms are left, and 99.9% of the radioactivity from the original kind of atom is gone. Some atoms decay into other atoms that are also radioactive, so the remaining radioactivity depends on the type of atom.
Cyclops
A Cyclops (Ancient Greek: Κύκλωψ, "Kyklōps"; plural Κύκλωπες, "Kyklōpes"), is a member of a primordial race of giants in Greek mythology, each with a single eye in the center of his forehead.
The most famous of these beings is the cyclops Polyphemus, featured in Homer's "Odyssey".
In Hesiod's "Theogony", the Elder Cyclopes – Brontes (Greek: Βρόντης - "thunderer"), Steropes (Greek: Στερόπης - "lightning") and Arges (Greek: Ἄργης - "bright") – were one of three races of beings born to Gaia (Earth) and Ouranos (Sky); they were the brothers of the Hekatonkheires and the Titans. They were strong and stubborn, and very skilled craftsmen and blacksmiths. Ouranos, however, despised his children, and cast them into Tartarus alongside the Hekatonkheires. At the urging of his mother, Kronos, the youngest of the Titans, castrated Ouranos and deposed him, later freeing his monstrous brothers. Kronos soon cast them back into Tartarus, guarded by the female monster Kampê. Zeus and the Olympians later freed the Cyclopes along with the Hekatonkheires, to aid them in their war against Kronos and the Titans. They fashioned thunderbolts for Zeus to use as weapons, as well as Poseidon's trident and Hades' helm of invisibility. After the Titanomachy, the Elder Cyclopes worked for the god Hephaestus, helping him in his forges.
The Elder Cyclopes are not featured in either of Homer's works, but in the Odyssey, Homer describes another race of cyclopes as being the sons of Poseidon, god of the sea. They feature as herdsmen and shepherds with a taste for human flesh.
Magnetic field
In physics, the magnetic field is a field that passes through space and which makes a magnetic force move electric charges and magnetic dipoles. Magnetic fields are around electric currents, magnetic dipoles, and changing electric fields.
When placed in a magnetic field, magnetic dipoles are in one line with their axes to be parallel with the field lines, as can be seen when iron filings are in the presence of a magnet. Magnetic fields also have their own energy and momentum, with an energy density proportional to the square of the field intensity. The magnetic field is measured in the units of teslas (SI units) or gauss (cgs units).
There are some notable kinds of magnetic field. For the physics of magnetic materials, see magnetism and magnet, and more specifically diamagnetism. For magnetic fields made by changing electric fields, see electromagnetism.
The electric field and the magnetic field are components of the electromagnetic field.
The law of electromagnetism was founded by Michael Faraday.
Physicists can say that the force and torques between two magnets are caused by magnetic poles repelling or attracting each other. This is like the Coulomb force repelling the same electric charges or attracting opposite electric charges. In this model, a magnetic "H-field" is produced by "magnetic charges" that are 'smeared' around each pole. So, the H-field is like the electric field E which starts at a positive electric charge and ends at a negative electric charge. Near the north pole, all H-field lines point away from the north pole (whether inside the magnet or out) while near the south pole (whether inside the magnet or out) all H-field lines point toward the south pole. A north pole, then, feels a force in the direction of the H-field while the force on the south pole is opposite to the H-field.
In the magnetic pole model, the elementary magnetic dipole m is formed by two opposite magnetic poles of pole strength "q" separated by a very small distance d, such that m = "q" d.
Unfortunately, magnetic poles cannot exist apart from each other. All magnets have north/south pairs which cannot be separated without creating two magnets each having a north/south pair. Also, magnetic poles do not account for magnetism that is produced by electric currents nor the force that a magnetic field applies to moving electric charges.
The -field is defined as:
With this definition, Ampere's law becomes: