NEW DELHI — There are countless downsides to the world’s getting walloped by the coronavirus and being put under severe lockdown.

But here in one of the most polluted cities on earth, where many people routinely wear face masks to filter out the filth, something rare and wonderful has emerged: a pure blue sky.

Because there are so few cars on the road, few factories belching out black smoke and almost no active construction sites to create clouds of choking dust, pollution levels in New Delhi, India’s megalopolis capital, have dropped to remarkably low levels.

At night there are stars. During the day the air is so clean that, for once, you can’t taste it, free of the usual smoky metallic tang. One cruelty of the coronavirus is to be under a tight lockdown right now, with parks bolted shut, ordered to stay indoors unless vitally necessary, only to look out your windows and see this.