THE SOUTHWORTH PLANETARIUM 207-780-4249 www.usm.maine.edu/planet <http://www.google.com/url?q=http%3A%2F%2Fwww.usm.maine.edu%2Fplanet&sa=D&sntz=1&usg=AFQjCNHulkHuLP13bOG2PkNrPazsGWFs2A> 70 Falmouth Street Portland, Maine 04103 43.6667° N 70.2667° W Altitude: 10 feet below sea level Founded January 1970 Julian Date: 2459353.18 2020-2021: CXXXII THE DAILY ASTRONOMER Wednesday, May 19, 2021 The End is a tricky matter. Then again, which astronomical concept is truly ever straightforward? Our two-part discussion pertaining to space-time has led to contemplations about the great conclusion: the end of our Universe. How will the cosmos perish? Is it possible that it won't perish? Although cosmologists are confident that the Big Bang event brought the Universe into existence about 13.8 billion years ago, they haven't reached a consensus about its death. Instead, they offer an array of possible scenarios, akin to a movie with a list of alternate endings. Comfortingly, the only common denominator is that the end won't occur for quite some time to come. *WHAT WE KNOW* The Universe is expanding and has done so since its inception. The observational evidence substantiating this assertion is so compelling that no cosmologist disputes it. What remains unclear is what will transpire in the far distant future. *A WHIMPER* That's right, T.S., this magnificent space-time system capable of producing thousands of stars each second while also accommodating billions of galaxies, could simply perists forever. The expansion continues as the material within the Universe becomes cooler and more diffuse. In this scenario *entropy*, the tendency of the Universe toward states of greater disorder, ultimately prevails. We beleaguered humans are all too familiar with entropy. We exert ourselves just to keep entropy at bay: to maintain ourselves, our cities and societies. The modern world, as well as those who inhabit it, are miracles of organization. However, entropy will hold sway at the end as the stars fitter away their prodigious energy stores into the expanding Universe. Heat energy becomes scarce and even the longest-lived stars will perish, leaving a cold dark Universe bereft of life and complexity. Were this scenario to play out, this heat death won't occur for a very long time. The Universe will continue for a period equal to thousands of times its current age before the final star if snuffed out. Then, eternity: a period a thousand thousand thousand times greater than that which preceded it and this resultant period raised to its own power a billion times over and then some. Our mortal minds experience exceeding difficulty when we ponder infinities of time and space, so, perhaps, we best proceed. *THE BIG RIP!* Cosmology, already an intriguing branch of science, became all the more interesting once cosmologists discovered that the Universal expansion was actually accelerating. They had logically presumed that material within the Universe would gravitationally impede the expansion. The question then pertained to the ultimate fate: would it expand forever, stop entirely, or even cause an eventual collapse that would, itself, precipitate another Big Bang? Now, we add another possible scenario: the Big Rip! The Universal expansion could continue to accelerate until the space-time fabric is literally ripped apart, casting everything asunder. The cosmos doesn't just cool off and spread out. It is reduced to tatters! This self-destruction won't occur for quite some time. *BORN AGAIN* Perhaps the Universal expansion acceleration will eventually stop. The Universe will continue to expand for a while until it stops and then falls back on itself. After quite a long time -an immense amount of time!- the Universe implodes back to a singularity which then "erupts" to cause another Big Bang: the birth of another Universe. One can infer from this scenario that our Universe could have been born out of a previous version. Moreover, ours could be an *oscillating Universe*, defined as one that is constantly born, destroyed and then reborn continuously. *WHAT WE KNOW* More than 13 billion years preceded our births and trillions of years will elapse after our deaths. We know that a small part of our minds yearns to know what will transpire in the unfathomably remote future when the cosmos meets its fate, if if ever does. We could be living in a Universe that will persist for all time. Or, the cosmos might ultimately be as mortal as all of us. We know that the Universe exists now and we are fully alive in it. To subscribe or unsubscribe from the Daily Astronomer: https://lists.maine.edu/cgi-bin/wa?SUBED1=DAILY-ASTRONOMER&A= <https://lists.maine.edu/cgi-bin/wa?SUBED1=DAILY-ASTRONOMER&A=1>