Priya draws the 4.5 billion years of the Earth as a clock of 24 hours, with midnight at the…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
Priya draws the 4.5 billion years of the Earth as a clock of 24 hours, with midnight at the formation of the Earth. She marks three events from NCERT: the first cells, 2 billion years ago, the invertebrates, 500 million years ago, and the end of the dinosaurs, 65 million years ago.
- At what time, in hours after midnight, does the first cell appear?
- How many minutes before the next midnight does the clock show the invertebrates?
- How many million years does one minute of this clock stand for?
Need a reminder? The key ideaShow
The Earth is about billion years old. Chemical evolution came first, then non-cellular life, then cells. Pasteur showed that life comes from life. Miller made amino acids from methane, hydrogen, ammonia and water vapour with an electric discharge. A scale of a clock: billion years.
The worked solution
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Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
Given. The Earth is billion years old, shown as hours.
Plan. Find the time after the Earth formed, and scale it.
Step 1. (a) The first cells came billion years after the Earth formed. Clock time: hours.
Step 2. (b) The invertebrates came billion years after the Earth formed. Clock time: hours. The time left is hours, which is minutes.
Step 3. (c) One hour is million years. One minute is million years.
Answer: hours; minutes; million years.
Check. The dinosaurs vanished minutes before midnight, which agrees with the lesson.
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