Timeline of the History of Astronomy
HISTORY OF CALENDAR
Gregorian Calendar
Before today’s Gregorian calendar was adopted, the older Julian calendar was used. It was admirably close to the actual length of the year, as it turns out, but the Julian calendar was not so perfect that it didn’t slowly shift off track over the following centuries. But, hundreds of years later, monks were the only ones with any free time for scholarly pursuits – and they were discouraged from thinking about the matter of "secular time" for any reason beyond figuring out when to observe Easter. In the Middle Ages, the study of the measure of time was first viewed as prying too deeply into God’s own affairs – and later thought of as a lowly, mechanical study, unworthy of serious contemplation.
As a result, it wasn’t until 1582, by which time Caesar’s calendar had drifted a full 10 days off course, that Pope Gregory XIII (1502 - 1585) finally reformed the Julian calendar. Ironically, by the time the Catholic church buckled under the weight of the scientific reasoning that pointed out the error, it had lost much of its power to implement the fix. Protestant tract writers responded to Gregory’s calendar by calling him the "Roman Antichrist" and claiming that its real purpose was to keep true Christians from worshiping on the correct days. The "new" calendar, as we know it today, was not adopted uniformly across Europe until well into the 18th century.
Here are a few more historical aspects of our calendar
Roman Calendar
The Romans were superstitious that even numbers were unlucky, so their months were 29 or 31 days long
When Rome emerged as a world power, the difficulties of making a calendar were well known, but the Romans complicated their lives because of their superstition that even numbers were unlucky. Hence their months were 29 or 31 days long, with the exception of February, which had 28 days. However, four months of 31 days, seven months of 29 days, and one month of 28 days added up to only 355 days. Therefore the Romans invented an extra month called Mercedonius of 22 or 23 days. It was added every second year.
Even with Mercedonius, the Roman calendar eventually became so far off that Julius Caesar, advised by the astronomer Sosigenes, ordered a sweeping reform. 46 B.C. was made 445 days long by imperial decree, bringing the calendar back in step with the seasons. Then the solar year (with the value of 365 days and 6 hours) was made the basis of the calendar. The months were 30 or 31 days in length, and to take care of the 6 hours, every fourth year was made a 366-day year. Moreover, Caesar decreed the year began with the first of January, not with the vernal equinox in late March.
This calendar was named the Julian calendar, after Julius Caesar, and it continues to be used by Eastern Orthodox churches for holiday calculations to this day. However, despite the correction, the Julian calendar is still 111/2 minutes longer than the actual solar year, and after a number of centuries, even 111/2 minutes adds up
Lunar Calendar
The lunar calendar became the basis of the calendars of the ancient Chinese, Babylonians, Greeks, and Jews
moon solstice has best approximated a solar-year calendar was based on a 19-year period, with 7 of these 19 years having 13 months. In all, the period contained 235 months. Still using the lunation value of 291/2 days, this made a total of 6,9321/2 days, while 19 solar years added up to 6,939.7 days, a difference of just one week per period and about five weeks per century.
Even the 19-year period required adjustment, but it became the basis of the calendars of the ancient Chinese, Babylonians, Greeks, and Jews. This same calendar was also used by the Arabs, but Muhammad later forbade shifting from 12 months to 13 months, so that the Islamic calendar now has a lunar year of about 354 days. As a result, the months of the Islamic calendar, as well as the Islamic religious festivals, migrate through all the seasons of the year
Technological Advancement in Studying Stars
Egyptian Calendar
The Egyptian year coincided precisely with the solar year only once every 1,460 years
egyptian pyramids.
The ancient Egyptians used a calendar with 12 months of 30 days each, for a total of 360 days per year. About 4000 B.C. they added five extra days at the end of every year to bring it more into line with the solar year.1 These five days became a festival because it was thought to be unlucky to work during that time.
The Egyptians had calculated that the solar year was actually closer to 3651/4 days, but instead of having a single leap day every four years to account for the fractional day (the way we do now), they let the one-quarter day accumulate. After 1,460 solar years, or four periods of 365 years, 1,461 Egyptian years had passed. This means that as the years passed, the Egyptian months fell out of sync with the seasons, so that the summer months eventually fell during winter. Only once every 1,460 years did their calendar year coincide precisely with the solar year.
In addition to the civic calendar, the Egyptians also had a religious calendar that was based on the 291/2-day lunar cycle and was more closely linked with agricultural cycles and the movements of the star
7000 BC - Babylonians predict lunar eclipses. The Babylonians used their long record of eclipses to see regular patterns of eclipses.
1465 - Regiomontanus uses printing to produce astronomy books and tables. Regimontanus used the recently invented art of printing to produce books, almanacs, and tables of predictions of the positions of the Sun, Moon, and planets.
2500 BC - Building of Stonehenge. The building of Stonehenge took place over many centuries. Alignments of the stones at Stonehenge mark the rising and setting points of the Sun at the solstices.
1580 - Tycho carries out best pre-telescopic observations ever. Tycho's observations, made using specially built instruments, were the most accurate ever made with the naked eye. Tycho also invented his own geocentric model of the solar system
1609 - Galileo uses telescope for astronomical observations. Galileo didn't invent the telescope but he was among the first to use a telescope to examine the heavens. He carried out important observations of the Sun, Moon, Planets, and Stars.
• 1851 - Jean Foucault uses pendulum to demonstrate Earth rotates. Foucault showed that the pendulum swung in the same plane but the Earth rotated under it, causing an apparent change in the direction of the pendulum's swing.
1914- Edwin Hubble invented Hubble Telescope
1917 - 100" Mt. Wilson telescope completed. The Mt. Wilson telescope was the largest optical telescope in the world for 31 years until the Palomar reflector was completed.
Different Models of the Planet
• Tycho Brahe (1580's) was astronomy's 1st true observer. He showed that the Sun was much farther than the Moon from the Earth, using simple trigonometry of the angle between the Moon and the Sun at 1st Quarter.
Kepler (1600's) a student of Tycho who used Brahe's database to formulate the Laws of Planetary Motion which corrects the problems of epicycles in the heliocentric theory by using ellipses instead of circles for orbits of the planets.
Ptolemy (200 A.D.) was the Librarian of Alexandria who formulated complete description of the Solar System that explained/predicted the apparent motions.
Copernicus (1500's) reinvented the heliocentric theory and challenged Church doctrine.
Galileo (1620's) developed laws of motion (natural versus forced motion, rest versus uniform motion). Then, with a small refracting telescope (3-inches), destroyed the the idea of a "perfect", geocentric Universe
Heraclides (330 B.C.) developed the first Solar System model, beginning of the geocentric versus heliocentric debate
Aristarchus (270 B.C.) developed the heliocentric theory
Babylonians (~1600 B.C.) recorded position of planets, times of eclipses, etc. - also evidence from early Chinese, Central American and North European cultures such as Stonehenge.
(220 B.C.) - The early Greeks knew the Earth was a sphere based on the shadow of Earth on the Moon during lunar eclipses. Eratosthenes proceeded to use this information to measure circumference of Earth in the following manner; he knew that on a certain date that a stick
Theories of the Universe
Intelligent Design Theory
This theory is an offshoot of the creationist theory. This theory says that something above God and outside of our knowledge created the universe. If this theory is right, that would automatically mean the creationist theory is wrong. Some think that if this theory is true, that would mean that aliens are observing us.
Steady State Theory
the density of matter in the expanding universe remains unchanged due to a continuous creation of matter, thus adhering to the perfect cosmological principle, a principle that asserts that the observable universe is basically the same at any time as well as at any place.
Creationist Theory
This theory states that a God created the universe in seven days. This theory is supported by the Bible, but if this is true, the universe would be very young. Some people think that the universe is only 6,000 years old, if this theory is proven true.
Holographic Theory
This theory states that the entire universe is just a hologram. If this theory is correct, it would also mean that every living thing would also be a hologram. This theory is far different from all of the other theories because if it is true, all other theories would be pointless because the whole universe technically wouldn’t exist.
**The Big Bang theory **
says that the universe was in a tiny ball, and then it exploded and become bigger and all of the stars and planets came into existence then. Nobody knows where the original ball came from. If the Big Bang theory is correct, then it happened about 13.7 billion years ago. This theory is supported by the fact that the universe is continually expanding, and the this theory says that the universe just constantly expands. In 1965 two scientists discovered a pocket of heat that is thought to be a remnant of the heat that caused the Big Bang.