What's the longest wavelength possible??? 1) If radio waves have wavelengths around 100 meters long and a frequency of about 10*7 Hz, are there any wavelengths in the EM Spectrum that are longer? 2) I've heard the Gravity Probe LISA is using interferometers spaced 5 million km apart to measure gravity, does this mean gravity waves are supposed to be about 5 million km long? If so why? 3) Also, if Wavelength = 300,000km/s / frequency and frequency = 1, then that means the Wavelength is 300,000km for f=1. So then, how could a gravity wave be longer than light speed's frequency of 1? Did space's expansion stretch the 300,000km into 5 million km? Please help me, I'd really like to know, thanks.