As seen from the Earth, the Sun, Moon, and planets all appear to move along the ecliptic. ... Unlike the Sun, however, the planets don't always move in the same direction along the ecliptic. They usually move in the same direction as the Sun, but from time to time they seem to slow down, stop, and reverse direction!
Because of various events in their (unknown) past history that resulted in deviations from the theoretical orbit. That formed in the plain of the ecliptic.
Capturing a large passing comet or asteroid might do it.
The harmonic frequency of a musical instrument is the minimum frequency at which a string that is fixed at both ends in the instrument may vibrate. The harmonic frequency is known as the first harmonic. Each subsequent harmonic has a frequency equal to:
n*f, where n is the number of the harmonic and f is the harmonic frequency. Therefore, the harmonic frequency may be calculated using:
f = 100 / 2
f = 50 Hz
An example of an environmental issue is the acid rain in Germany. The acid rain is caused by pollution. Pollution that was caused by car putting harmful gases into the air is the main reason that there is acid rain in Germany. This is a problem because the acid rain is destroying Germany’s forests. Hope this helped!