[Lex Computer & Tech Group/LCTG] Here is something I never knew. From an email I get

[Steve Isenberg]

Speed of sound in steel is 5,960 m/s (not km/s).
Or so I hear.
-steve

On Wed, Jan 20, 2021 at 9:26 AM john rudy <jjrudy1 at comcast.net> wrote:

> If I have a solid object which is 1 light year long and I push it and there
> is somebody else on the other end, how long would it take for them to
> notice
> that I pushed it?
>
> When you push on an object - even one that appears completely solid - the
> movement takes time to move through the object. In pushing on the object,
> you're actually generating a wave that propagates through the object, as
> atoms push on adjacent atoms. When a baseball player begins to swing a bat,
> the far end of the bat actually lags behind the near end of the bat. The
> length of the bat is short compared to the speed at which the effect
> propagates through the bat, so it appears to be completely rigid. But the
> longer the object, the more noticeable it will be that the force takes time
> to move through the object.
>
> And how fast does the force move through the object? At the speed of sound.
>
> And how fast is that? Depends on the substance. Suppose the solid object is
> made of steel. Movement would propagate through the object at 5.960
> km/second. So if you had a steel object that was a bit less than 6 km long
> and you push on one end, someone on the other end would feel the effect 1
> second later.
>
> If you had steel rod that was one light-year in length, a force would take
> a
> little over 50,000 years to propagate to the other end.
>
>
>
>
>
> John Rudy
>
> 781-861-0402
>
> 781-718-8334 (cell)
>
> John.rudy at alum.mit.edu <mailto:John.rudy at alum.mit.edu>
>
>
>
> 13 Hawthorne Lane
>
> Bedford, MA  01730-1047
>
>
>
>
>
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