It is difficult to overstate the importance of using units in physics. Back in the day, my physics teacher would take off half the points in a question, if we forgot to include units. A question might be, convert 100°C to degrees F. If you said 212, you’d only get half points. Even if you said 212°, you’d be penalized. The correct answer would be 212°F.
You might think that this is just silly nit-picking. I mean, of course it’s 212°F; what else would it be? Why all the fuss?
Well, in 1999, NASA lost its Mars Climate Orbiter. Everything went well until it was time to put the device into orbit around Mars. Suddenly it failed. The Orbiter had come in too low, had entered the atmosphere, and wound up breaking up and burning.
A review showed that some important values had been calculated in Imperial units, and hadn’t then been converted into metric units. NASA was using SI units, but one of the American companies was still using English units. Somewhere in all the calculations, a conversion had been overlooked, and the Orbiter was destroyed. It was a $125 million loss.
A more complete explanation of this disaster can be found here.
Another useful page is here.
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The Importance of Units
It is difficult to overstate the importance of using units in physics. Back in the day, my physics teacher would take off half the points in a question, if we forgot to include units. A question might be, convert 100°C to degrees F. If you said 212, you’d only get half points. Even if you said 212°, you’d be penalized. The correct answer would be 212°F.
You might think that this is just silly nit-picking. I mean, of course it’s 212°F; what else would it be? Why all the fuss?
Well, in 1999, NASA lost its Mars Climate Orbiter. Everything went well until it was time to put the device into orbit around Mars. Suddenly it failed. The Orbiter had come in too low, had entered the atmosphere, and wound up breaking up and burning.
A review showed that some important values had been calculated in Imperial units, and hadn’t then been converted into metric units. NASA was using SI units, but one of the American companies was still using English units. Somewhere in all the calculations, a conversion had been overlooked, and the Orbiter was destroyed. It was a $125 million loss.
A more complete explanation of this disaster can be found here.
Another useful page is here.
.