# Highest RPM?

by fedorfan
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 P: 113 Does anyone know what the highest rpm in the universe is?
 P: 555 RPM? are you talking about tires or computers or what if its speed related dont doubt the power of c
P: 1,295
 Does anyone know what the highest rpm in the universe is?
No, but John Wheeler would jokingly discuss the maximum upper limit on horsepower (about 10^64), an engine with which would instantly rip itself into a black hole .

 P: 113 Highest RPM? My best guess would be a turbocharger at like 180,000 rpm. I guess the universal speed limit would be the speed of light. Also, Im talking about whatever is rotating the fastest. Not pkanets or something though, I mean revolutions per minute, not year.
P: 1,295
 Quote by fedorfan My best guess would be a turbocharger at like 180,000 rpm.
This illustrates the problem with the question, because RPM on its own has no limit (as the revolving system decreases in radius). Using a radius about one meter, the speed of light limits us to an RPM of about 18 billion, so that is a safe upper limit.
 PF Gold P: 8,964 My semi-educated guess is that the fastest that anyone will ever likely run across in reality would be a black hole. Since the angular momentum of the remains of the original star is conserved, those suckers can spin.
 P: 113 Yeah danger, thats probably a very close guess, although I suspect a microscopic black would be even faster.
 P: 113 Noone else knows anything?
 P: 1 I'd say it is the flagellum at up to 17,000 rpm....if you look at a figure of it you'll be pretty amazed at it's complexity and sophistication
P: 363
 Quote by fedorfan My best guess would be a turbocharger at like 180,000 rpm. I guess the universal speed limit would be the speed of light. Also, Im talking about whatever is rotating the fastest. Not pkanets or something though, I mean revolutions per minute, not year.
Electrons around nuclei in atoms good enough candidates?
 PF Gold P: 8,964 To start with, that would be revolving, not rotating... but it doesn't count anyhow. As for the electron spin component, it isn't really spin. I think that you pretty much have to stick with macroscopic phenomena.
 P: 1 http://www.popsci.com/gear-amp-gadge...est-motor-ever apparently the highest RPM device in existence?
PF Gold
P: 8,964
 Quote by drboylecj http://www.popsci.com/gear-amp-gadge...est-motor-ever apparently the highest RPM device in existence?
Holy ****ing sheepgarbage! 104,000 rpms? Jeez, I thought that those 30,000 rpm satellite stabilization motors were fast. This is just outrageous.
Still, though, for non-man-made objects my money is on the black hole.
 HW Helper P: 2,327 How could one convince one's self that Dyson's little motor is running at such a high rpm? Even with an oscope, how would one know that the oscope isn't simply picking up "fake" electronic signals from the control circuit? I don't believe that I can hear such a high pitch. Maybe some angular momentum test?
 P: 119 The maximum RPM in the universe is dependent on the radius of the spinning object. The formula for calculating velocity of the outer edge of the "wheel" using RPM is: $$\upsilon=C*RPM$$ Therefore: $$RPM=\frac{\upsilon}{C}$$ Plugging the speed of light in for velocity (and making it an inequality to show that it has to be less than c): $$RPM<\frac{c}{C}$$ So the maximum RPM of an object is the speed of light divided by the object's circumference. That means the smaller the object, the faster it can spin.
PF Gold
P: 8,964
 Quote by Superstring So the maximum RPM of an object is the speed of light divided by the object's circumference. That means the smaller the object, the faster it can spin.
Which brings us back to black holes...
HW Helper
P: 2,155
 Quote by Superstring The maximum RPM in the universe is dependent on the radius of the spinning object. The formula for calculating velocity of the outer edge of the "wheel" using RPM is: $$\upsilon=C*RPM$$ Therefore: $$RPM=\frac{\upsilon}{C}$$ Plugging the speed of light in for velocity (and making it an inequality to show that it has to be less than c): $$RPM<\frac{c}{C}$$ So the maximum RPM of an object is the speed of light divided by the object's circumference. That means the smaller the object, the faster it can spin.
Well, actually
$$\omega < \frac{c}{r}$$
and convert to revolutions per minute. (RPM is a unit, it sows confusion to try to use it as a variable)

I got
$$\omega < \frac{2.86\times 10^9\,\mathrm{m}}{r}\cdot\frac{\mathrm{rev}}{\mathrm{min}}$$
so... for something with radius equal to the Planck length, $1.77\times 10^{44}$ revolutions per minute? (If such a thing could exist, of course)
P: 5
 Quote by drboylecj http://www.popsci.com/gear-amp-gadge...est-motor-ever apparently the highest RPM device in existence?

WRONG!

1 Million would be the fastest.

http://gizmodo.com/5087710/matchbook...ion-rpm-record

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