The most common malfunctions of a manual gearbox are grinding when switching, self-disengaging gears (the lever fails to stay locked), too much free travel of the lever, impossible shifting into first (this is very common in old heavy German machines), impossible shifting into reverse.
Someone who knows more about brain scanning technology than I do might be able to show that such a machine is impossible: that for technical reasons we could not freeze and read the state of every neuron.
My new MacBook Pro, for example – a multi thousand dollar machine – is impossible to repair or upgrade.
The physics literature contains various no-go theorems for time machines, i.e., theorems which purport to establish that, under physically plausible assumptions, the operation of a time machine is impossible.
What is being described is, in effect, a perpetual motion machine, an impossible contraption of the sort that clutters in-boxes at the Patent Office (and, I might add from personal experience, at magazines).
To those who would argue that the notion of a perpetual motion machine is impossible, we give you the revolving door -- that ever-spinning entrance and exit between public service in government and the hugely profitable private sector.
Every single piece of a bike — every bolt and screw — is custom-made, making the machines almost impossible to value.
He lists five subjects or concepts that he thinks every educated person should understand: Darwinian evolution, the Copernican solar system, the size of the universe, the laws governing the conservation of energy (that way people would know that infinite energy sources and perpetual motion machines are impossible) and ratios (so people would have a sense of scale).
The machines were impossible to find last Christmas, but the company says it has ramped up supply for this year's buying crush.
While infinitely shrinking machines appear to be consistent with Newtonian mechanics, Davies (2001, 672) points out that the atomic and quantum mechanical nature of matter in our universe makes infinitely shrinking machines physically impossible.
