10 January1946, the antennae of Camp Evans emit a short signal with very great power towards the Moon. A little more than two seconds later, they capture a slight echo. This was the first success for Project Diana, two years after its launch. Giving form(s) — in all the senses that this term may include — to what is invisible is at the heart of Simon Ripoll-Hurier’s practice. From amateur radio operator clubs to ghost hunters, from bird watchers to the drums that could send signals on battle fields, the challenge here is to successfully establish contact with a distant, absent being, by using much more mysterious means than those inhabiting our daily lives. So, although the machine appears in diverse forms, the challenge is probably more linked to the immaterial, to the silence or to the background noises that constantly disturb the efforts and attempts