(Have someone read the quote out loud. Pause.)What does that quote mean to you? (Solicit shared responses.) The passing of time is the one thing that we all have in common. We may be in different zones, but time marches on the meter keeps ticking and time passes, standing still only in the figurative sense.
Today, were going to spend a little time talking about a lot of time. Well go over the specifics later so dont worry about taking notes just yet. You will need a piece of paper and something to write with however. Right now, take a minute to think about what time means to you; then well see how time helps us put everything into perspective.
Time flies when youre having fun, doesnt it? On one side of your paper, list as many fast times that you can think of For example, the weekends always seem to end too soon. You have 1 minute. (Start timer.)Time! All right, (insert name), please read one item off your list. Continuing down the row, the next person (insert name), read something different from your list.Good!
On the other hand, a watched pot never boils does it? Turn your paper over and list the times that seem to take forever to pass, like when youre waiting in line for popcorn at the movies. You have 1 minute starting now. (Start timer.)Times up! Lets go through the list like before, starting with (insert name).Excellent!As we can see from these few examples, individuals may perceive time differently, depending on the situation and circumstance.Nevertheless, a minute is a minute is a minute. And so is a year.Your parents, and I, probably seem really old from your point of view. And you all, from where I stand, seem pretty young!To put it into perspective, lets figure out the average age for this particular class. (Tally results on board.) Is anyone less than 11 years old? Please raise your hand if youre 12. How about 13? Is anyone, besides me, 14 or older? (Figure average; example assume 13.)Okay, so the average age in this class of students is 13 years. These days, average life expectancy is about 70 years. Do you realize that youve already lived nearly 20% of your expected life? Your estimated life is a little over 5 times what youve already lived, or 57 years. (13/70 = 0.186; 70/13 = 5.38; 70-13 = 57)Like everything else, time is relative no pun intended! A generation is the time difference between you and your parents. - you know, that HUGE gap! On the high end, the time for one generation is roughly 40 years. For all you history buffs out there, the next slide relates the time unit called a generation to several major world events.
in a galaxy far, far away! Did you know thatThere have been over 5 generations of time since the American Revolution, in 1776.From the time Christopher Columbus discovered America in 1492, over 12.5 generations have passed.Its been about 23 generations since William the Conqueror took over in 1066.And, from the beginning of recorded time, the year AD1, over 50 generations have come and gone.Modern man supposedly showed up on the planet about 20,000 years, or 500 generations, ago.The last dinosaurs roamed the earth nearly 1,625,000 generations, or 65 million years, ago.They first appeared about 235 million years ago; thats the equivalent of 5,635,000 generations!And finally, I promise, the earth is estimated to have formed 4.5 billion years ago off the top of my head, thats 112,500,000 generations ago!As you can see, 13 years, or even one generation, is relatively insignificant in our Mother Earths family album! And you thought I was old!Heres another way to visualize how very long ago the Age of Dinosaurs ended.Imagine yourself at a Dallas Cowboys football game in Texas Stadium. Usually, there would be about 65,000 other people cheering around you. If you had each and every one of them stand in line for 1,000 years to get out after the game, the last person would be 65 million years older than when they came in! Sometimes it seems like it takes that long to get home! Anyway, thats how long its been since the last dinosaur walked around on the field.
The numbers get really big, really fast when we look beyond recorded history. For those of you who just love math, lets quickly review the placeholders from one to a billion. Remember how it goes? (Ones, Tens, Hundreds, Thousands, Millions, Billions)Tonights lotto jackpot is an estimated 54 million dollars Even though a million doesnt seem like very much anymore, it would last me for a few years - maybe! Seriously, think about just how much those big numbers really represent - especially in terms of time. If you counted at a rate of one number per second, it would take about 15 minutes to count to one thousand. Counting at that same rate 8 hours a day, 7 days a week - it would take over a month to count to one million! Thats a lot of counting! In terms of geologic time, however, a million years takes on a different meaning. The main difference between geologists (and astronomers) and most other scientists is their attitude toward time.
Some earth processes like earthquakes - are finished in a matter of seconds; some like flood erosion take a few days to happen; and others like the formation of planets take million of years to complete. The time segments vary by significant orders of magnitude. This diagram shows a logarithmic scale of common events. Remember what logarithmic means? Each division is a successive power of ten. (Review chart)Using general principles and specific procedures that well discuss later, geologists, paleontologists, physicists, astronomers, oceanographers and others have helped devise a geologic clock, called the Geologic Time Scale, that puts the history of the earth into perspective, based on absolute and relative time.
Geologic time is the period of time extending from the formation of the earth to the present. The Geologic Time Scale is an arbitrary chronologic sequence of geologic events.What does this chart tell you? (Solicit responses.)relative dates = one is older than the other absolute dates = number of years agodivisions of time = eon, era, period, epoch (like months, weeks and days)origin of names: region first described =Cambrian - the old Roman name for WalesOrdovician and Silurian -named for ancient tribes of WalesDevonian - named for Devonshire, EnglandMissisippian - exposures along the Mississippi RiverPennsylvanian - exposures in the mountains of PennsylvaniaPermian - province in Russia where rocks are exposedTriassic - exposures in GermanyJurassic - Jura Mountains bordering FranceCretaceous - Latin word for chalk, great exposures of chalk formedQuaternary/Tertiary - no particular meaning (third/fourth) life form (zoo = life) =Phanerozoic = Evident Life Cenozoic = Recent Life, the Age of Mammals Mesozoic = Middle Life, the Age of Reptiles Paleozoic = Ancient Life, the Age of InvertebratesCryptozoic = Obscure Life Pre-Cambrian = before the Cambrian period
Using the information from absolute and relative dates,