How to measure the age of a rock…from the moon
By MUNGAI KIHANYA
The Sunday Nation
Nairobi,
09 November 2008
Do you remember Daniel Kungu? Yes, the one with the seven-question record? We answered two in a past article; now let’s attempt the others, starting with: “How do you calculate the age of rocks, e.g. from the moon?”
Before discussing rocks from the moon, let’s talk about those that are right here on Earth. Their age is determined through radioactivity.
The atoms of some materials spontaneously disintegrate emitting (harmful) radiations in the process. The rate of disintegration is directly proportional to the amount of material available. Thus, ten kilograms will disintegrate twice as fast as five kilos and so on.
The rate of disintegration is usually expressed in terms of the so-called “half-life”. This is the time it takes for a given quantity to disintegrate by half. Different radioactive materials have different half-lives, ranging from a small fraction of a second to many thousands of years.
Geologists study newly formed rocks (from active volcanoes, for example) to determine the radioactive materials present and the rate of disintegration. This information is then compared to that from older rocks.
Since the half-life of the particular radioactive material is known, the age of the older rock can be calculated from the rate of disintegration. But to do that, one must make a very important assumption: that when the older rock was formed, it had the same content of radioactive material as the new one.
That assumption is only valid if the two rocks have similar characteristics - mineral content, physical structure, etc. The same procedure is done for rocks from the moon, that is, comparing their radioactivity with that of rocks found on Earth.
Daniel’s fourth question was: “How does one alight from a moving/stationery space craft in space to repair a moving space station”. Well; you simply open the door, get out and do the repairs! But I’m sure Daniel wants more than that…
Here is a common scene in the movies (or the circus): a vehicle is moving at high speed; second one approaches it from behind and begins to overtake. When they are side-by-side, the overtaking vehicle slows down and the two now move at equal speeds. Then a stunts-man gets out of one and hops across to the other…and we all applaud!
It’s the same thing they do in outer space. The spacecraft approaches the station and begins to overtake. When the two are side-by-side, the craft slows down a little so that they now move at equal speeds. Then the astronaut gets out and does the repairs on the station. In fact it is somewhat easier in outer space than on Earth because there is no wind out there.
Daniel’s next questions are religious: “Is it possible to calculate
number of years Adam and Eve stayed in
“When was Satan damped to earth: before or after creation?” I’d say after because there was nothing before creation. He couldn’t have been damped before he was created!
Finally; “What prevents De La Rue from making their own Kenyan money? Why pay them our money to make our money?” The answer to the first part is HONESTY. And to the second part: it is because they are cheaper than doing the printing for ourselves.
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