Theia

The name of the hypothesized protoplanet is derived from the mythical Greek goddess Theia, a Titan who gave birth to the Moon goddess Selene. According to the giant impact hypothesis, Theia formed alongside the other planet size bodies in the Solar System about 4.6 Ga (4.6 billion years ago), and was approximately the size of Mars.

One formation theory is that Theia materialized at the L4 or L5 Lagrangian points relative to Earth (in about the same orbit and about 60° ahead or behind),[1] similar to a trojan asteroid.[9] The stability of Theia's orbit was affected when its growing mass exceeded a threshold of about 10% of the Earth's mass.[1] Gravitational perturbations by planetesimals caused Theia to depart from its stable Lagrangian location, and subsequent interactions with proto-Earth caused the two bodies to collide.[1]

Astronomers think the collision between Earth and Theia happened about 4.53 Ga; about 30-50 million years after the rest of the Solar System formed. However, evidence presented in 2008 suggests that the collision may have occurred later, at about 4.48 Ga.[10]

Origins
In 1898, George Howard Darwin made an early suggestion that the Earth and Moon had once been one body. Darwin's hypothesis was that a molten Moon had been spun from the Earth because of centrifugal forces, and this became the dominant academic explanation.[5] Using Newtonian mechanics, he calculated that the Moon had actually orbited much closer in the past and was drifting away from the Earth. This drifting was later confirmed by American and Soviet experiments using laser ranging targets placed on the Moon.

However, Darwin's calculations could not resolve the mechanics required to trace the Moon backwards to the surface of the Earth. In 1946, Reginald Aldworth Daly of Harvard University challenged Darwin's explanation, adjusting it to postulate that the creation of the Moon was caused by an impact rather than centrifugal forces.[6] Little attention was paid to Professor Daly's challenge until a conference on satellites in 1974 where it was reintroduced. It was then republished in Icarus in 1975 by Drs. William K. Hartmann and Donald R. Davis. Their models suggested that, at the end of the planet formation period, several satellite-sized bodies had formed that could collide with the planets or be captured. They proposed that one of these objects may have collided with the Earth, ejecting refractory, volatile-poor dust that could coalesce to form the Moon. This collision could help explain the unique geological properties of the Moon.[7]

A similar approach was taken by Alfred G. W. Cameron and William Ward, who suggested that the Moon was formed by the tangential impact of a body the size of Mars. The outer silicates of the colliding body would mostly be vaporized, whereas a metallic core would not. Hence, most of the collisional material sent into orbit would consist of silicates, leaving the coalescing Moon deficient in iron. The more volatile materials that were emitted during the collision would probably escape the Solar System, whereas silicates would tend to coalesce.[8]

The giant impact hypothesis proposes that the Moon was created out of the debris left over from a collision between the young Earth and a Mars-sized body. This is the favored[1] scientific hypothesis for the formation of the Moon. Evidence for this hypothesis includes Moon samples which indicate the surface of the Moon was once molten, the Moon's apparently relatively small iron core and a lower density than the Earth, and evidence of similar collisions in other star systems (which result in debris disks). The colliding body is sometimes called Theia (or Orpheus) for the mythical Greek Titan who was the mother of Selene, the goddess of the moon.[2][3]

There remain several unanswered issues surrounding this hypothesis. Lunar oxygen isotopic ratios are essentially identical to Earth's, with no evidence of a contribution from another solar body.[4] Also, lunar samples do not have expected ratios of volatile elements, iron oxide, or siderophilic elements, and there is no evidence to suggest that the Earth ever had the magma ocean implied by this hypothesis.

Giant impact hypothesis



Artist's depiction of the giant impact that is hypothesized to have formed the Moon.

Roman school

The Roman school is the education system of Ancient Rome.
Each school week of Ancient Rome was believed to begin before sunrise, and last until late afternoon. The fixed beginning of the school year was March 24, which is held in honor of Minerva, the Roman Goddess of Wisdom and Knowledge.
In earlier times, a boy's education would have taken place at home. His father would have taught him to read and write with ivory alphabet blocks, and would have prepared him for war with wooden swords. On the other hand, mothers taught their daughters to sew, weave, clean and spin cloth.
The Roman education was divided into three stages:
Contents
hide
•   1 Primary (first stage)
•   2 Secondary (second stage)
•   3 Tertiary (third stage)
•   4 Teachers
•   5 See also
•   6 References

 Primary (first stage)
The primary school was for the children aged seven to twelve. Students would be accompanied by slaves: one to escort him and another to carry his books and possessions. The students would write on a cera or tabula (wax tablet) with a Stylus (in Latin Stilus) to practice their scripting. This then gave them the option of writing in ink on parchment or papyrus with a quill. If the students were disobedient they would suffer corporal punishments such as a rap across the knuckles with a rod for being disobedient or disrespectful, being hit with a birch branch for not knowing the answer to a question, being whipped with a leather strap for making a serious mistake, and being whipped with a strap with knots in it continuously for not knowing the answers to multiple questions.
 Secondary (second stage)
Boys aged 12–15 studied language and literature either at home with a personal tutor, a gifted slave, or (only boys would go away from home) in public with a grammaticus. Under the Empire, a primary position was given to Virgil's Aeneid. Girls were taught at home by the same personal tutor who taught their brothers. The works that were studied allowed students to practice their reading and to develop their ability to comment on grammar, figures of speech, and the writer's use of mythology. The schools cost a lot of money, and not every parent sent their child to school.
 Tertiary (third stage)
Around 16, rhetoric was studied in public lectures. Things like lawyers and politicians were the most important jobs. There were two main types of rhetorical exercise:
1.   Suasoriae: Developed boy's skills in constructing arguments
2.   Controversiae: Devised arguments for and against the accused
 Teachers
At Rome from the time of Julius Caesar onwards, there were privileges for teachers who were also Roman citizens. Emperor Vespasian (Emperor from 69-79 AD) founded two chairs for the teaching of Greek and Latin rhetoric; Quintilian was the first holder of the Latin chair. Outside Rome, Vespasian granted exemption from civic obligation to teachers of grammar and rhetoric.
The spread of Roman culture and domination in the West was made possible by the teaching of a fairly standard and difficult curriculum to the sons of the local elites.
See also
•   Education in Ancient Rome for a more general perspective on the education in Ancient Rome

Timeline of ancient Greece

Greek Bronze Age / Aegean civilization (3300 BC - 1100 BC)

Mainland Greece (Helladic period)
Early Helladic EH 2800-2100 BC
Middle Helladic EH 2100-1500 BC
Late Helladic LH 1500-1100 BC / (Mycenaean Greece (1600 BC - 1100 BC))
•   Eruption of Thera (Santorin Island) volcano dated probably between 1660 to 1613 BC.
 Crete (Minoan civilization)
Early Minoan EM 3650-2160 BC
Middle Minoan MM 2160-1600 BC
Late Minoan LM 1600-1170 BC
 Cyclades (Cycladic civilization)
Early Cycladic 3300-2000 BC
Kastri = EH II-EH III (ca. 2500-2100) BC
Convergence with MM from ca. 2000 BC
 Ancient Greece (1100 BC - 146 BC)
 Dark Age (ca.1100 BC - 800 BC)
 Archaic Period (750 BC - 480 BC)
•   776 Traditional date for the first historic Olympic games.
•   757 The first Messenian war starts. (date disputed by Jerome, Pausanias and Diodorus; this estimate is based on a reading of Diodorus' Spartan king lists and Pausanias' description of the war)
•   757 Office of Archon reduced to 10 years. Members of the ruling family to hold the office starting with Charops. (dating based on Pausanias)
•   754 Polydorus becomes king of Sparta.
•   738 Alternate date for the end of the first Messenian war.
•   735 Perdiccas I of Macedon flees from Argos to Macedonia and conquers the land.
•   734 Polydorus sends colonists to Italy.
•   727-717 Hippomenes, archon of Athens, who killed his daughter's adulterer by yoking him up to his chariot and then locks his daughter up with a horse until she dies. (Pausanias and Aristotle)
•   c. 725 Lelantine War between Chalcis and Eretria. Many Greek cities are allied with one or the other. Dates before this point uncertain.
•   719 Polydorus The king of Sparta is murdered by Polymarchus.
•   716 The reign of the Heraklids over Lydia is ended when Candaules, known as Myrsilus to the Greeks, is murdered by Gyges because of his wife’s anger.
•   690 Pheidon becomes tyrant of Argos
•   687 Annual office of Archon established. Any Athenian citizen can be elected to office if they meet the requirements. Creon elected first annual archon. (dating based on Pausanias)
•   685 The second Messenian war begins
•   665 The second Messenian war ends
•   656 Cypselus subjects Corinth to tyranny
•   645-560 Spartan wars with Tegea all unsuccessful
•   642 or 634 Battus establishes a Greek colony in Cyrene in Libya
•   632 Cylon, Athenian noble, seizes Acropolis and tries to make himself king, fails
•   630 Formal pederasty is introduced, first in Crete, as a means of population control and an educational modality
•   621 Draco, Athenian lawgiver, issues code of laws where everything is punishable by death – Draconian
•   594 Solon, Athenian statesman, becomes Archon pre-582BC (cf. ML6 (death of Kypselos 585BC) and Plutarch Sol. 14), captures Salamis from Megarians- later, when member of the Areopagus is appointed to effect social reforms in order to preserve order in Athens, which include the abolishment of the security of debts on the debtor's person (Aristotle Ath. Pol. 6), returning exiled Athenian slaves (Solon fr. 4 in Ath. Pol. 12), changing the value of weights and measures to the Korinthian standard, prohibiting the export of grain from Attica and encouraging the planting of olives (Plut. Sol. 22-4), established the property classes (Ar. Ath. Pol. 7) and the council of 400 (Ar. Ath. Pol. .
•   590 Sappho, Greek poet and priestess, flourishes on island of Lesbos.
•   569 Pythagoras was born.
•   565 Peisistratos, Athenian general, organizes Diakrioi, party of poor people.
•   546 Pythagoras founded science and philosophy.
•   510 Pythagoras founded his own school.
•   500 Pythagoras died in Crotona, Italy, when he was in Metapontum.
 Late Archaic Period
•   561 Pisistratus takes power in Athens for first time,
•   555 Pisistratus driven out by Lycurgus who leads nobles
•   549 Pisistratus restored by help of Megacles
•   546 Croesus, rich king of Lydia, captured at Sardis by Persians
•   542 Pisistratus expelled, makes fortune from Thracian mines
•   532 Pisistratus restored by Thessaly and Lygdamis of Naxos
•   527 Pisistratus dies, succeeded by sons Hippias and Hipparchus
•   525 Persian Darius I, son-in-law of Cyrus the Great takes Egypt
•   515 Hippias becomes sole ruler after the death of Hipparchus
•   508 Hippias is forced to leave Athens.
•   507 Cleisthenes, Greek reformer, takes power, increases democracy
•   490 Themistocles and Miltiades, Athenians, defeat Darius at Marathon, Phidippides runs with news
•   484 Aeschylus, Athenian playwright,
 Classical Period (480 BC - 323 BC)
•   480 Leonidas, Spartan, makes sacrifice of 300 Spartans at the Battle of Thermopylae so main force can escape; Xerxes son of Darius is leading the Persians
•   480 Simultaenous with Thermopylae, the Greeks and Persians fight to a draw in the naval Battle of Artemisium
•   480 Battle of Salamis - Themistocles, Athenian general, lures Persians into Bay of Salamis, Xerxes loses and goes home, leaves behind Mardonius
•   479 Pausanias, Greek general routs Mardonius at the Battle of Plataea
•   479 Battle of Mycale frees Greek colonies in Asia. After the Battle of Salamis, Athens set up the Delian League, treasury on island of Delos, a confederacy of cities around the Aegean Sea. It was intended as a military defense association against Persia but was turned into an empire, collecting tribute and deciding policy of its associates. Sparta formed rival Peloponnesian League
•   476-462 Cimon elected general each year, he was victorious over Persia and then enforced military power on Delian League
•   474 Pindar, Greek poet moves to Thebes from court at Syracuse
•   471 Themistocles ostracized
•   468 Sophocles, Greek playwright, defeats Aeschylus for Athenian Prize
•   461 Cimon ostracized
•   457 Pericles, Athenian statesman begins Golden Age, he was taught by Anaxagoras, who believed in dualistic Universe and atoms
•   456 Aeschylus dies
•   449 Herodotus, Greek Historian, writes History of Greco-Persian War from 490-479
•   448 Ictinus and Callicrates, Greek architects rebuild Acropolis from Persian destruction
•   441 Euripides, Greek playwright, wins Athenian prize
•   440 Heraclitus, Greek philosopher, believes everything is mutable
•   435 Phidias, Greek sculptor, completes Zeus at Elis 1 of 7 wonders
•   433 Corinth, Sparta, Megara and Aegina ally against Corfu, Athens, Rhegium, and Leontini
•   432 End of Golden Age, Athens under Pericles blockades Potidaea (Battle of Potidaea), Corfu declares war on Corinth (Battle of Sybota)
•   431 Sparta led by Archidamus II sets out to destroy Athens thus starting the Peloponnesian War
•   431 Empedocles, Greek doctor, believes body has Four Temperaments.
•   430 Failed peace mission by Athens, bubonic plague year, Sparta takes no prisoners
•   430 Leucippus, Greek philosopher, believes every natural event has natural cause. Athenian Plague appears in Athens.
•   429 Phormio, Athenian admiral, wins the Battle of Chalcis
•   429 Pericles dies of Athenian Plague, possibly typhus or bubonic plague
•   429 Hippocrates, Greek doctor, believes diseases have physical cause
•   428 Plato born.
•   428 Mitylene rebels, chief city of Lesbos
•   427 Archidamus II dies, Alcidas, Greek admiral sent to help Lesbos, raids Ionia and flees after seeing Athenian might Athenian Plague returns
•   427 Mitylene surrenders to Athens, Plataeans surrender to Athens
•   427 Aristophanes, Greek playwright, wins Athenian Prize
•   426 Corfu secures island for Athens
•   426 Demosthenes, Athenian general, and Cleon, Athenian demagogue, revitalizes Athenian forces, makes bold plans opposed by Nicias, his first military campaign barely succeeds
•   425 Athenian fleet bottles up Spartan navy at Navarino Bay, Nicias resigns
•   424 Syracuse sends Athenians home
•   424 Pagondas of Thebes crushes Athenian army at the Battle of Delium, Brasidas a Spartan general makes a successful campaign, Cleon exiles Thucydides for 20 years for arriving late
•   423 Truce of Laches supposed to stop Brasidas but doesn't, Nicias leads Athenian forces in retaking Mende
•   422 Cleon meets Brasidas outside of Amphipolis, both are killed (Battle of Amphipolis)
•   421 Peace of Nicias brings temporary end to war, but Alcibiades, a nephew of Pericles, makes anti-Sparta alliance
•   420 Quadruple alliance of Athens, Argos, Mantinea, and Elis confronts Spartan-Boeotian alliance
•   419 King Agis, ruler of Sparta, attacks Argos, makes treaty
•   418 Battle of Mantinea, greatest land battle of war, gives Sparta victory over Argos, which broke treaty, Alcibiades thrown out, alliance broken
•   416 Alcibiades makes plans, is restored to power
•   415 Hermai are mutilated in Athens, Alcibiades accused, asks for inquiry, told to set sail for battle (Sicilian Expion), is condemned to death in absentia, he defects to Sparta
•   414 Lemachus, Athenian commander killed at Syracuse
•   413 Nicias and Demosthenes killed at Syracuse
•   412 Alcibiades is thrown out of Sparta, conspires to come back to Athens
•   411 Democracy ends in Athens by Antiphon, Peisander, and Phrynichus, overthrown by Theramenes, Constitution of the 5000, Athenian navy recalls Alcibiades, confirmed by Athenians
•   410 After several successes, Athenian demagogue Cleophon rejects Sparta peace overtures
•   409 Byzantium recaptured by Alcibiades for Athens
•   408 Alcibiades reenters Athens in triumph, Lysander, a Spartan commander, builds fleet at Ephesus
•   407 Lysander begins destruction of Athenian fleet, Alcibiades stripped of power
•   406 Callicratides, Spartan naval leader, loses Battle of Arginusae over blockade of Mitylene harbor, Sparta sues for peace, rejected by Cleophon
•   405 Lysander captures Athenian fleet, Spartan king Pausanius lays siege to Athens, Cleophon executed, Corinth and Thebes demand destruction of Athens
•   404 Athens capitulates Apr 25 Theramenes secures terms, prevents total destruction of Athens, Theramenes and Alcibiades are killed
•   401 Thucydides, Greek historian, leaves account of Golden Age of Pericles and Peloponnesian War at his death (History of the Peloponnesian War)
•   399 Socrates, Greek philosopher, condemned to death for corrupting youth.
•   387 Peace of Antalcidas concluded between the Greeks and the Persians.
•   347 Plato, Greek philosopher, founder of Academy, dies.
•   342 Aristotle, Greek philosopher, begins teaching Alexander, son of Philip of Macedon
•   338 Philip of Macedon defeats Athens and Thebes at Chaeronea Aug 2 and establishes League of Corinth in winter of 338 BC/337 BC .
•   336 Alexander succeeds father, who was assassinated by Pausanias of Orestis
•   333 Alexander defeats Persians at Battle of Issus, Oct, but Darius III escapes
•   332 Alexander conquers Egypt
•   331 at Battle of Gaugamela Oct 1, Alexander ends Achaemenid Dynasty and takes Persian Empire
•   330 Democritus, Greek philosopher, develops Atomic theory, believes cause and necessity, nothing comes out of nothing
•   329 Alexander conquers Samarkand
•   327 Alexander invades Northern India, but his army is despondent and refuses to march further eastwards.
 Hellenistic Period (323 BC - 146 BC)
•   323 Alexander dies, his generals vie for power in Wars of the Diadochi:Antigonus- Macedon, Antipater- Macedon, Seleucus- Babylonia and Syria, Ptolemy- Egypt, Eumenes- Macedon, Lysimachus, later Antipater's son Cassander also vies for power.
•   323 - 322 Lamian War.
•   322 - 320 First War of the Diadochi.
•   320 Partition of Triparadisus.
•   320 - 311 Second War of the Diadochi.
•   316 Menander, Greek playwright, wins Athenian prize.
•   310 Zeno of Citium founds his stoic school in Athens.
•   307 Epicurus founds his philosophic school in Athens.
•   301 Battle of Ipsus.
•   300 Euclid, Greek mathematician, publishes Elements, treating both geometry and number theory (see also Euclidean algorithm).
•   295 Athens falls to Demetrius, Lachares killed.
•   280 - 275 Pyrrhic War.
•   281 Creation of the Achaean League.
•   279 Gallic invasion of the Balkans.
•   274 - 271 First Syrian War.
•   267 - 262 Chremonidean War.
•   265 Archimedes, Greek mathematician, develops screw, specific gravity, center of gravity; anticipates discoveries of integral calculus.
•   260 - 253 Second Syrian War.
•   246 - 241 Third Syrian War.
•   219 - 217 Fourth Syrian War.
•   214 - 205 First Macedonian War.
•   203 - 200 Fifth Syrian War.
•   200 - 196 Second Macedonian War.
•   192 - 188 Roman–Syrian War.
•   172 - 167 Third Macedonian War.
•   170 - 168 Sixth Syrian War.
•   150 - 148 Fourth Macedonian War.
 Notes
1.   Wasson, Ruck, Hofmann, The Road to Eleusis: Unveiling the Secret of the Mysteries, Harcourt, Brace, Jovanovich, 1978. ISBN 0-15-177872-8.