Final answer:
Aliasing in the context of the Doppler effect happens when the sampling rate is too low to accurately record the frequency changes caused by the relative motion between source and observer, resulting in blueshifts or redshifts.
Step-by-step explanation:
Aliasing will occur at the point when the Doppler shift is such that the sampling rate is not high enough to capture the frequency changes accurately. This is described by the Nyquist Theorem, which states that to prevent aliasing, the sampling rate must be at least twice the maximum frequency of the signal. The Doppler effect itself is an alteration in the observed frequency of a wave due to the motion of either the source or the observer. When the source of waves, such as sound or light, moves toward an observer, a blueshift occurs due to a decrease in wavelength, shifting the colors of light toward the blue end of the spectrum. Conversely, when the source moves away from the observer, a redshift occurs due to an increase in wavelength. For sound waves, this results in changes in pitch, with a higher pitch as the source approaches and a lower pitch as it moves away.