Where and When Objectives Understand what the Modified Julian Calendar is and why it was made. Be able to tell today’s date in the Modified Julian Calendar. Understand Universal Transverse Mercator. Be familiar with Celestial and Galactic Coordinate Systems. Be able to find and place objects on a Galactic Coordinate map Understand why these are used in Cosmic Ray detection.

Where and When Modified Julian Calendar In 1583 a French scholar, Joseph Justus Scaliger, invented the Julian Period. It was designed to replace Western calendars which were based on the ruling eras of nation.

Where and When Modified Julian Calendar The Julian period is equal to 7980 years of exactly days 7980 is based off of the time it takes for three common cycles of the time to align again at (1,1,1) o 28 year solar cycle o 19 year lunar cycle o 15 year Roman indiction cycle 28 (Solar) * 19 (Lunar) * 15 (Indiction) = 7980

Where and When Modified Julian Calendar The solar cycle is the time that it takes for calendar days of years to repeat. Thus you only ever need to own 28 consecutive calendars.

Where and When Modified Julian Calendar The lunar cycle is the time it takes for the moon to be approximately the same phase at the beginning of the year In other words there are 19 years in between years that begin with a full moon

Where and When Modified Julian Calendar The indiction cycle is an old Roman tax period It has historical importance because dates were often recorded using this cycle No one knows where it came from

Where and When Modified Julian Calendar Scaliger determined what year the solar and indiction cycles were in in the year of Christ’s birth o The solar cycle was in the 9 th year o The indiction cycle was in the 3 rd year The lunar cycle was set to 1 on that year and so year 1 in our calendar became (9,1,3) or the 4713 rd year The year 4713 B.C. then became the first year in the Julian Period

Where and When Modified Julian Calendar The calendar started at 0 at noon on January 1 st 4713 B.C. Each day adds 1 to the count with partial days adding a partial count o i.e. 12 hours adds.5 to the count o 3 hours adds.125 o 18 hours and 30 min. adds Today’s date is very long o is midnight Sept. 22, 2000 Recently the Modified Julian Calendar has been put into use

Where and When Modified Julian Calendar The modified Julian calendar has 2 primary benefits o The Julian day number is reduced in length by at least 2 digits o The day begins at midnight instead of noon The modified Julian calendar day equals the Julian calendar day minus Zero is now midnight Nov. 17, 1858 All dates there after are consecutive just like the Julian Calendar

Where and When Why Do We Care? This Won’t Ever Come Up! (Will It?) On June 15, 763 B.C. there was a solar eclipse seen at Nineveh. On April B.C. there was a lunar eclipse seen at Nineveh. How many days elapsed between these two celestial events?

Where and When Same Example Using Julian Days On the Julian Date of 1,442,903 there was a solar eclipse seen at Nineveh. On the Julian Date of 1,566,296 there was a solar eclipse seen at Nineveh. Now it is easy to see that there were 123,393 days between these two recorded celestial events.

Where and When The Galaxy Awaits The Earth is a wonderful place and all, but how can we locate things that aren’t on Earth. One of the major issues currently with Cosmic Rays is determining where they come from. Once we determine where they come from, how do we keep track of that location? A very perplexing problem!

Where and When Don’t Worry Homer Luckily for us, Astronomers have devised ways to locate and map objects. It is called Galactic Coordinates. And it looks like this:

Where and When Our Galaxy (Aren’t We Pretty?) Galaxy Center

Where and When Latitude Measurement

Where and When Longitude Measurement

Where and When The Poles Defined (Well, Shown Anyway)