Last Updated：2025/12/04
(physics) An apparent perpetual motion machine, the subject of a thought experiment, that would consist of a tiny paddle wheel and a ratchet, and might seem to be able to extract useful work from random fluctuations (heat) in a system at thermal equilibrium, in violation of the second law of thermodynamics.
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Brownian ratchet
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Source Word
Brownian ratchet
Noun
(physics)
An
apparent
perpetual
motion
machine,
the
subject
of
a
thought
experiment,
that
would
consist
of
a
tiny
paddle
wheel
and
a
ratchet,
and
might
seem
to
be
able
to
extract
useful
work
from
random
fluctuations
(heat)
in
a
system
at
thermal
equilibrium,
in
violation
of
the
second
law
of
thermodynamics.
Japanese Meaning
(物理学) ブラウン運動（微視的なランダムな熱振動）を利用して、見かけ上永続的な運動をするように見える装置の概念。具体的には、微小なパドルウィールとラチェットから構成され、熱平衡状態にある系におけるランダムな熱揺らぎから仕事を抽出できるかのように見えるが、これは熱力学第二法則に反するという点が強調される思考実験上の機構
Sense（1）
(physics)
An
apparent
perpetual
motion
machine,
the
subject
of
a
thought
experiment,
that
would
consist
of
a
tiny
paddle
wheel
and
a
ratchet,
and
might
seem
to
be
able
to
extract
useful
work
from
random
fluctuations
(heat)
in
a
system
at
thermal
equilibrium,
in
violation
of
the
second
law
of
thermodynamics.
（ plural ）
