In my volunteer role as manager of a youth hostel in remote Welsh mountainous terrain, I’ve needed to apply physics to provide the services expected by today’s visitors. There’s no mains water, no landline phone, and no mobile phone signal. Our organisation also has a second hostel which has no mains electricity. The hostels are looked after by a different volunteer warden each week, while I’m 200 miles away in Wiltshire. Everything must be sufficiently reliable to function under those challenging conditions.