Last Updated：2025/12/08
(physics) A relativistic paradox concerning the concept of Born rigidity within special relativity, where an ideally rigid cylinder that is made to rotate about its axis of symmetry. The radius R as seen in the laboratory frame is always perpendicular to its motion and should therefore be equal to its value R₀ when stationary. However, the circumference should appear Lorentz-contracted to a smaller value than at rest. This leads to the contradiction that R = R₀ and R < R₀.
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Ehrenfest paradox
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Source Word
Ehrenfest paradox
Proper noun
(physics)
A
relativistic
paradox
concerning
the
concept
of
Born
rigidity
within
special
relativity,
where
an
ideally
rigid
cylinder
that
is
made
to
rotate
about
its
axis
of
symmetry.
The
radius
R
as
seen
in
the
laboratory
frame
is
always
perpendicular
to
its
motion
and
should
therefore
be
equal
to
its
value
R₀
when
stationary.
However,
the
circumference
should
appear
Lorentz-contracted
to
a
smaller
value
than
at
rest.
This
leads
to
the
contradiction
that
R
=
R₀
and
R
<
R₀.
Japanese Meaning
特殊相対性理論において、ボーン剛体性の概念に関連するパラドックス。具体的には、理想的な剛体と考えられる回転する円筒で、実験室系では回転軸に対して垂直な半径は静止時と同じ値（R₀）であるのに対し、周囲はローレンツ収縮により静止時の値よりも短く観測されるために生じる矛盾を説明する。
Sense（1）
(physics)
A
relativistic
paradox
concerning
the
concept
of
Born
rigidity
within
special
relativity,
where
an
ideally
rigid
cylinder
that
is
made
to
rotate
about
its
axis
of
symmetry.
The
radius
R
as
seen
in
the
laboratory
frame
is
always
perpendicular
to
its
motion
and
should
therefore
be
equal
to
its
value
R₀
when
stationary.
However,
the
circumference
should
appear
Lorentz-contracted
to
a
smaller
value
than
at
rest.
This
leads
to
the
contradiction
that
R
=
R₀
and
R
<
R₀.
（ canonical ）
