Approximate Timelines

Transcript

Approximate TimelinesIf you have lived for a million seconds, how old would you be? We shall look at approximate times and timelines of some events and phenomena, and use powers of 10 to represent and compare these quantities. Time in seconds Comparison to real-world events/phenomena 10^0=1 second - Time taken for a ball thrown up to fall back on the ground (typically a few seconds). 10^1=10 seconds - Time blood takes to complete one full circulation through the body: 10-20 seconds ( 1×10^1-2×10^1 seconds). - Typical waiting time at a traffic signal. Isn't it quite amazing how someone is able to estimate things like the number of ants in the world or the time blood takes to fully circulate? You may carry this wonder whenever you encounter such facts. You will come across such facts in subjects like Science and Social Science, where such estimates are made frequently. ■(&10^2 " seconds " @& ≈1.6" minutes " ) Time needed to make a cup of tea: 5-10 minutes (≈4×10^2-8×10^2 " seconds " ). Time for light to reach the Earth from the Sun: about 8" minutes " (≈5×10^2 " seconds " ). ? 10^5 seconds ≈1.16 days and 10^6 seconds ≈11.57 days. Think of some events or phenomena whose time is of the order of (i) 10^5 seconds and (ii) 10^6 seconds. Write them in scientific notation.10^7 seconds ≈115.7 days / ≈3.8 months - Time spent sleeping in a year: about 4 months. - Time taken by Mangalyaan mission to reach Mars: 298 days ( ≈2.65×10^7 seconds). - Time taken by Mars for one full revolution around the Sun: 687 Earth-days/1.88 Earth-years ( ≈6×10^7 seconds). 10^8 seconds ≈3.17 years - The typical lifespan of most dogs is 3 to 15 years. 10^9 seconds ≈31.7 years - The orbital period of Halley's comet is 75-79 years; the next expected return is in the year 2061 ( ≈2.4×10^9 seconds). - Duration of one full revolution of Neptune around the Sun: 60,190 Earth-days/~165 Earth-years or 89,666 Neptunian days/ 1 Neptunian-year ( ≈5.2×10^9 seconds). A day on Neptune is about 16.1 hours Notice how rapid exponential growth is -10^6 seconds is less than a fortnight, but 10^9 seconds is a whopping 31 years (about half the life expectancy of a human)! 10^10 seconds ≈317 years - The Chola dynasty ruled for more than 900 years ( ≈3×10^10 seconds) between the 3rd Century BCE and 12th Century CE. 10^11 seconds ≈3,170 years - Age of the oldest known living tree: about 5000 years ( ≈1.57×10^11 seconds). - Time since the last peak ice age: 19,000-26,000 years ago ( ≈6×10^11 seconds - 8.2×10^11 seconds). 10^12 seconds ≈31,700 years - Early Homo sapiens first appeared 2-3 lakh years ago ( ≈7×10^12-9×10^12 seconds). The entire population around that time could fit in a large cricket stadium. 10^13 seconds - The Steppe Mammoth is ≈3.17 lakh estimated to have years appeared around 8-18 lakh years ago. 10^14 seconds - A fossil of Kelenken Guillermoi, ≈3.17 million a type of terror bird, is dated years to 15 million years ago (≈ seconds). 10^15 seconds ≈3.17 crore years Age of Himalayas: 5.5 crore years/55 million years ( ≈1.7×10^15 seconds); they continue to grow a few mm every year. Dinosaurs went extinct 6.6 crore years ago/ 66 million years ago ( ≈2×10^15 seconds). Dinosaurs first appeared more than 20 crore/200 million years ago ( ≈6×10^15 seconds). It takes about 23 crore years for the Sun to make one complete trip around the Milky Way ( ≈7×10^15 seconds). 10^16 seconds ≈31.7 crore years - Plants on land started 47 crore/470 million years ago ( ≈ seconds). 10^17 seconds ≈3.17 billion years The oldest fossil evidence suggests that bacteria first appeared about 3.7 billion years ago. - The Earth is 4.5 billion years old. - The Milky Way galaxy was formed 13.6 billion years ago, and the Universe was formed 13.8 billion years ago. Notice that 10^9 seconds is of the order of the lifespan of a human, whereas 10^18 seconds ago the universe did not exist according to modern physics!! The exponential notation can capture very large quantities in a concise manner. Very large quantities are often beyond our experience and comprehension. To put them into perspective, we can relate and compare them with quantities we are familiar with. This can give an essence of how large a number or a measure is!