The photo stopped me in my tracks: Californians jogging, walking and cycling along a crowded bike path. Surely it must have been snapped weeks ago, before “social distancing” became a phrase on everyone’s lips? No: The photo was dated March 28, almost 10 days after California Gov. Gavin Newsom issued a “stay at home” order to combat the coronavirus pandemic in the state.

Experts have repeatedly assured us it’s safe to spend time outside — in fact it’s pretty much the only activity they have said is safe. Epidemiologists have even framed outdoor exercise as a healthy way to boost the immune system. Certainly, getting outside is essential for mental health — and there have been numerous studies linking time in nature to increased resilience and decreased stress.

But of course, going outside during a pandemic is safe only as long as you stay well away from other people. And since several other things the experts said have turned out to be falsely reassuring — masks wouldn’t help, coronavirus isn’t airborne, you only really have to stay home if you feel sick — it’s no wonder some of us are now wondering if it’s truly safe to take a stroll.