Radio wavelengths are just like ordinary light but they have much longer wavelengths. This allows the light to penetrate very deeply into the cloud. It’s the same affect that you see when there’s a sunset. Why does a sunset appear red? It’s because the short wavelength light, which is a bluer color, has been absorbed by the atmosphere; but the longer wavelength light, the redder color, has made it through. So in the Orion Nebular Cloud which is extremely dense and very dusty, we cannot use blue light—it’s far too short a wavelength, red light is difficult, infrared light is also extremely difficult to see into this cloud; but the very longest wavelength, the radio wavelengths, we can use to penetrate into the cloud.