the longest wavelength that we can measure using current technology under normal circumstances is in the radio wave region of the electromagnetic spectrum. Radio waves have wavelengths ranging from millimeters to kilometers, and we have developed instruments capable of detecting and measuring radio waves of varying lengths.
For instance, radio telescopes are designed to observe and study radio waves emitted by astronomical objects. They can detect and measure radio waves with wavelengths up to several meters or even longer. These instruments allow us to explore and analyze cosmic phenomena such as pulsars, quasars, and the cosmic microwave background radiation.
It's important to note that the notion of time dilation doesn't directly impact the measurement of wavelengths. Time dilation refers to the phenomenon where time appears to pass differently for objects moving relative to each other or in strong gravitational fields. While it can have implications for measuring time intervals or frequencies, it doesn't fundamentally restrict the measurement of wavelengths.