Thomas Edison tried
two thousand different
materials in search of a
filament for the light
bulb. When none worked
satisfactorily, his
assistant complained,
“All our work is in vain.
We have learned
nothing.”
Edison replied very
confidently, “Oh, we
have come a long way
and we have learned a
lot. We know that there
are two thousand
elements which we
cannot use to make a
good light bulb.”
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