The millihertz (mHz) is a unit of frequency equal to one-thousandth of a hertz. While it sounds minuscule, frequencies at this scale have critical applications in science and technology. For example, the Earth’s rotation slows down over time, a phenomenon observable at the millihertz level. Measuring such tiny variations requires precise timing methods, akin to those used in atomic clocks that define international time standards.
In the realm of biology, certain very slow rhythms in the human body, such as some brainwave patterns, occur at millihertz frequencies. Understanding these subtle oscillations can provide insights into sleep cycles and neurological conditions. Millihertz frequencies are also employed in geophysics for monitoring seismic activities and gravitational wave detection, highlighting their significance in uncovering the mysteries of the universe.
The rotation per minute (RPM) is a fascinating unit of rotational speed that measures the number of complete turns an object makes in one minute. Though RPM is most commonly associated with car engines and records players, it’s a vital metric in a wide array of industries, including aviation, where turbine engines can reach up to 10,000 RPMs. Fun fact: beyond Earth, RPM played a crucial part in the Apollo missions—during re-entry, the command module performed a slow spin at around 2 RPMs to ensure even heat distribution!
In the everyday whimsy of RPM, consider that your average washing machine can spin at an impressive 1,200 RPM during the spin cycle. Additionally, high-speed trains like the Japanese Shinkansen have wheels rotating at about 280 RPM while cruising at speeds over 300 km/h, showing how RPM bridges the gap between mundane household chores and cutting-edge transportation technology.
Millihertz | Rotations per minute |
---|---|
0
mHz
|
0
rpm
|
10
mHz
|
0.6
rpm
|
20
mHz
|
1.2
rpm
|
30
mHz
|
1.8
rpm
|
40
mHz
|
2.4
rpm
|
50
mHz
|
3
rpm
|
60
mHz
|
3.6
rpm
|
70
mHz
|
4.2
rpm
|
80
mHz
|
4.8
rpm
|
90
mHz
|
5.4
rpm
|
100
mHz
|
6
rpm
|
110
mHz
|
6.6
rpm
|
120
mHz
|
7.2
rpm
|
130
mHz
|
7.8
rpm
|
140
mHz
|
8.4
rpm
|
150
mHz
|
9
rpm
|
160
mHz
|
9.6
rpm
|
170
mHz
|
10.2
rpm
|
180
mHz
|
10.8
rpm
|
190
mHz
|
11.4
rpm
|
200
mHz
|
12
rpm
|
210
mHz
|
12.6
rpm
|
220
mHz
|
13.2
rpm
|
230
mHz
|
13.8
rpm
|
240
mHz
|
14.4
rpm
|
250
mHz
|
15
rpm
|
260
mHz
|
15.6
rpm
|
270
mHz
|
16.2
rpm
|
280
mHz
|
16.8
rpm
|
290
mHz
|
17.4
rpm
|
300
mHz
|
18
rpm
|
310
mHz
|
18.6
rpm
|
320
mHz
|
19.2
rpm
|
330
mHz
|
19.8
rpm
|
340
mHz
|
20.4
rpm
|
350
mHz
|
21
rpm
|
360
mHz
|
21.6
rpm
|
370
mHz
|
22.2
rpm
|
380
mHz
|
22.8
rpm
|
390
mHz
|
23.4
rpm
|
400
mHz
|
24
rpm
|
410
mHz
|
24.6
rpm
|
420
mHz
|
25.2
rpm
|
430
mHz
|
25.8
rpm
|
440
mHz
|
26.4
rpm
|
450
mHz
|
27
rpm
|
460
mHz
|
27.6
rpm
|
470
mHz
|
28.2
rpm
|
480
mHz
|
28.8
rpm
|
490
mHz
|
29.4
rpm
|
500
mHz
|
30
rpm
|
510
mHz
|
30.6
rpm
|
520
mHz
|
31.2
rpm
|
530
mHz
|
31.8
rpm
|
540
mHz
|
32.4
rpm
|
550
mHz
|
33
rpm
|
560
mHz
|
33.6
rpm
|
570
mHz
|
34.2
rpm
|
580
mHz
|
34.8
rpm
|
590
mHz
|
35.4
rpm
|
600
mHz
|
36
rpm
|
610
mHz
|
36.6
rpm
|
620
mHz
|
37.2
rpm
|
630
mHz
|
37.8
rpm
|
640
mHz
|
38.4
rpm
|
650
mHz
|
39
rpm
|
660
mHz
|
39.6
rpm
|
670
mHz
|
40.2
rpm
|
680
mHz
|
40.8
rpm
|
690
mHz
|
41.4
rpm
|
700
mHz
|
42
rpm
|
710
mHz
|
42.6
rpm
|
720
mHz
|
43.2
rpm
|
730
mHz
|
43.8
rpm
|
740
mHz
|
44.4
rpm
|
750
mHz
|
45
rpm
|
760
mHz
|
45.6
rpm
|
770
mHz
|
46.2
rpm
|
780
mHz
|
46.8
rpm
|
790
mHz
|
47.4
rpm
|
800
mHz
|
48
rpm
|
810
mHz
|
48.6
rpm
|
820
mHz
|
49.2
rpm
|
830
mHz
|
49.8
rpm
|
840
mHz
|
50.4
rpm
|
850
mHz
|
51
rpm
|
860
mHz
|
51.6
rpm
|
870
mHz
|
52.2
rpm
|
880
mHz
|
52.8
rpm
|
890
mHz
|
53.4
rpm
|
900
mHz
|
54
rpm
|
910
mHz
|
54.6
rpm
|
920
mHz
|
55.2
rpm
|
930
mHz
|
55.8
rpm
|
940
mHz
|
56.4
rpm
|
950
mHz
|
57
rpm
|
960
mHz
|
57.6
rpm
|
970
mHz
|
58.2
rpm
|
980
mHz
|
58.8
rpm
|
990
mHz
|
59.4
rpm
|
1000
mHz
|
60
rpm
|
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