we love space!

Astronomer and Linguist Mihir Kulkarni, a graduate student at Columbia University, spoke in Pupin Hall for the first big event hosted by Columbia Astronomy Outreach this academic year called “Clocks of the Universe.” The night consisted of a lecture, a 3D virtualization, and stargazing, which was unfortunately canceled due to weather. New Bwoggers Michael Beltz and Mary Clare Greenlees covered the event.

When walking into Pupin Friday night, there were signs directing us to the fourth floor, where we were told the lecture part of the program was going to be held. We were greeted by a graduate student, handing us a small survey to provide data for the Astronomy Outreach Program. Questions varying from how old you are, your occupation, and whether you learned anything from the lecture. We sat in the fifth row, in the middle for a perfect viewing experience. The audience is what shocked the most, there were young children there, groups of university students, and older adults. One of us is a potential Astrophysics major, while the other is potentially majoring in Civil Engineering. Having both come from STEM backgrounds, we thought that the event would be a lot of fun and teach us something new. The event began with a 45-minute lecture by Kulkarni about time. This lecture, which he called“Clocks of the Universe,” focused on how our concept of time has changed throughout history and how we can create a timescale by looking at the sky. We have 3 astronomical tellers of time: the day, the month, and the year. The day is represented by the time it takes for the earth to fully rotate: about 24 hours. The month is represented by the time it takes the moon to complete a lunar orbit around the earth. The year is commonly defined as about 365 days, represented by the time it takes the earth to orbit the sun.

But as Kulkarni went on, he explained that the definitions of these terms can vary. A day could be either a sidereal day, the time it takes for a distant star to be in the same spot in the sky, or a solar day, the time it takes for the earth to rotate with respect to the sun. A solar day is slightly longer because it is the time it takes for the earth to rotate 360 degrees plus the angle the earth has orbited around the sun at that time. The slight inaccuracies in days can be seen in sundials, which have to be readjusted every day to account for the sun’s changing relative position in the sky in relation to the Earth at noon. This change is a result of the earth’s tilt on its axis which affects the length of the day at different points of the year. Today, for example, is the autumnal equinox, one of the two days of the year where day and night are the same lengths! Days in the summer are longer in the northern hemisphere because of the tilt toward the sun, and days in the winter are shorter.

Kulkarni explained how we measure years. A year can be measured by studying the ecliptic, the sun’s position to background stars (sidereal), and the path of the sun throughout the sky. This method measure around 365.25636 days in one year. Another measurement used was a tropical year, which is the time it takes the sun to travel along from the ecliptic from one vernal equinox (where the plane of the equator aligns with the center of the sun-fun fact the vernal equinox is today!) to the next. This measures at 365.242189 days, 20 minutes less than the ecliptic method. Why would there be a 20-minute difference in how they are measured? Because of the precession motion of Earth. The Earth’s axis is rotating. Currently, Polaris is at the position of North Pole (approximately by 1 degree), however, in 2000 years, it won’t be because the direction North is pointed is slowly changing because of this rotation.

Time is relevant to all of us – getting the most out of the day is something that we all struggle to do. But for the longest time, we were wasting time because it was not correctly measured. The Roman Calendar, was a mess, to say the least. Random months were added, and those who were in rural areas most likely would not have gotten the necessary information about the additional months. So, in 46 BC, Julius Caesar decided that he had enough and standardized the Julian Calendar. Making the average length of the year was 365.25 days. The calendar was off, meaning that a day would be lost every 128 years. This was the system that was more or less used until the 16th century. All of this changed because of the Catholic Church. Easter traditionally falls on the Sunday after the Spring Equinox, but it kept being pushed up, so to combat this, Pope Gregory XIII took it upon himself to create the Gregorian Calendar, which we use today. In order to account for the days that were lost, October 4, 1582, became October 15, 1582. The average length of the year was now 365.2425 days, now one day was lost every 3200 years. However, because of religious tensions, it was only adopted by Great Britain and the colonies in 1752 and wasn’t accepted in Russia until after the Bolshevik Revolution (meaning that the October Revolution didn’t technically happen in October according to the Gregorian Calendar).

Although the cloudy skies canceled stargazing, we were assured that we could still take a tour of the observatory on Pupin’s roof or visit the 3D Wall on the 13th floor. We walked into the dark room and were directed to pick up a pair of 3D glasses. A graduate student was guiding us through different computer-generated simulations of deep space objects. The attendees were of all ages, ranging from retired to children. A little boy with light up shoes asked, “What if all the galaxies exploded and then came back together?” The audience laughed at the boy’s question, but the graduate student went into an in-depth explanation about what happens when galaxies “explode.” Even though the boy was still young, he nodded along to his words and understood what he said. The ability for this event to touch such a broad range of people and still have audience members of all backgrounds learn new things is what makes it so approachable and welcoming.

beautiful space picture via Bwog Archives