# Slowest Perceptible Speed?
**URL:** https://boards.straightdope.com/t/slowest-perceptible-speed/48155
**Category:** Factual Questions
**Created:** [January 2, 2001, 11:16pm UTC](https://boards.straightdope.com/t/slowest-perceptible-speed/48155 "2001-01-02T23:16:43Z")
**Posts on this page:** 9
**Page:** 1
### Author:  [@Speedbump](https://boards.straightdope.com/u/Speedbump)
#### Post date: [January 2, 2001, 11:16pm UTC](https://boards.straightdope.com/t/slowest-perceptible-speed/48155/1 "2001-01-02T23:16:43Z")
I’ve read that young bamboo can grow so fast that the growth can actually be seen. While fast for a plant, a meter a day is damn slow for the rest of the kinetic world. Please tell me- What is the slowest speed perceptible to the human eye? How few inches/feet an hour/day can something move and still be _seen_ to move?
---
### Author:  [@choosybeggar](https://boards.straightdope.com/u/choosybeggar)
#### Post date: [January 2, 2001, 11:39pm UTC](https://boards.straightdope.com/t/slowest-perceptible-speed/48155/2 "2001-01-02T23:39:42Z")
Just a WAG. I can easily see a clock’s second hand move, but cannot perceive motion of the minute hand. So the limit must be somewhere in between.
Assuming the second and minute hands have 2" radii, then each travels 12.56" per revolution. The second hand makes the trip in 60 seconds. Therefore its rate is 0.209"/sec (0.0119 MPH). The mintue hand make the trip in 60 minutes. Therefore its rate is 0.00349"/sec (0.000198 MPH). Somewhere between the two rates is your answer (Hope all the math is correct-guess I’ll find out soon enough :)).
---
### Author:  [@Arjuna34](https://boards.straightdope.com/u/Arjuna34)
#### Post date: [January 2, 2001, 11:54pm UTC](https://boards.straightdope.com/t/slowest-perceptible-speed/48155/3 "2001-01-02T23:54:14Z")
You can see a minute hand moving under magnification - does that count?
One meter/day (sorry, I’m feeling too lazy to stay metric) is about 1/2 mil (1 mil = 0.001 inch) per second. This should be easily visible under 20 or 30x magnification, and probably under 10x, especially if the bamboo happens to be resting next to a metal rod marked in 1 mil increments, so you could see it move past something.
Arjuna34
---
### Author:  [@Mauvaise](https://boards.straightdope.com/u/Mauvaise)
#### Post date: [January 3, 2001, 12:18am UTC](https://boards.straightdope.com/t/slowest-perceptible-speed/48155/4 "2001-01-03T00:18:32Z")
> [@](#):
>
> \*Originally posted by Speedbump \*
> \*\*What is the slowest speed perceptible to the human eye? \*\*
That would be, without a doubt, the speed with which Mr. Mauv moves after being asked to take out the rubbish.
---
### Author:  [@cornflakes](https://boards.straightdope.com/u/cornflakes)
#### Post date: [January 3, 2001, 1:11am UTC](https://boards.straightdope.com/t/slowest-perceptible-speed/48155/5 "2001-01-03T01:11:25Z")
> [@](#):
>
> \*Originally posted by choosybeggar \*
> **Just a WAG. I can easily see a clock’s second hand move, but cannot perceive motion of the minute hand…**
You can if you have a reference. Watch the hand as it passes one of the hour marks (whatever those hash marks are called.)
Yes, I _did_ have too much time in my life way back when.
---
### Author:  [@Astroboy14](https://boards.straightdope.com/u/Astroboy14)
#### Post date: [January 3, 2001, 1:13am UTC](https://boards.straightdope.com/t/slowest-perceptible-speed/48155/6 "2001-01-03T01:13:43Z")
The slowest possible speed?
Try posting a speedy reply to a GQ when the trained chimps who run the LAN at my university are fooling around with the system! Now THAT’s slow!!
---
### Author:  [@choosybeggar](https://boards.straightdope.com/u/choosybeggar)
#### Post date: [January 3, 2001, 1:35am UTC](https://boards.straightdope.com/t/slowest-perceptible-speed/48155/7 "2001-01-03T01:35:48Z")
> [@](#):
>
> \*Originally posted by cornflakes \*
> \*\*
>
> > [@](#):
> >
> > \*Originally posted by choosybeggar \*
> > **Just a WAG. I can easily see a clock’s second hand move, but cannot perceive motion of the minute hand…**
>
> You can if you have a reference. Watch the hand as it passes one of the hour marks (whatever those hash marks are called.)
>
> Yes, I _did_ have too much time in my life way back when. \*\*
You lookin at a clock with a 2" radius minute hand? Bigger is no fair.
---
### Author:  [@PosterChild](https://boards.straightdope.com/u/PosterChild)
#### Post date: [January 3, 2001, 1:48am UTC](https://boards.straightdope.com/t/slowest-perceptible-speed/48155/8 "2001-01-03T01:48:47Z")
If you know how big the clock is (using the clock is a cool idea) with the minute hand that you can see move, then you can calculate the speed, and you’ll have a good approx for the slowest visible speed.
---
### Author:  [@Cartooniverse](https://boards.straightdope.com/u/Cartooniverse)
#### Post date: [January 3, 2001, 1:59am UTC](https://boards.straightdope.com/t/slowest-perceptible-speed/48155/9 "2001-01-03T01:59:04Z")
How fast does the moon set? I sat in my car in Long Island City, NY a few years ago. I was waiting for a shoot to start. I was listening to the radio, and happened to look in my rear view mirror. I saw the moon- just about full, or full. Lovely- the sun had just broken the horizon, and so the moon was wicked bright. There was a street lamp about 200 feet behind me.
As I sat and watched, the moon set. I was aware of the rotation of the earth in a different way than I’d ever been before. I was watching myself turn away from the moon, when normally the perception is that we are stationary, and the moon “sets”. It took quite a few minutes for the moon to move from above the arm of the street light, past it, to below the arm.
I will never forget that feeling for as long as I live. I felt as though I was turning with imperceptable slowness, but the moon indeed was not turning. Because the lamp offered a mark by which I could measure my movement, I felt that I was moving.
Extraordinary. As I recall, that was the single best thing about the entire day, low-budget music videos being what they are.
Cartooniverse