This year’s Earth Day, April 22, was about March for Science rallies taking place in Washington, DC, and dozens of other cities around the world.

Back in India, this year’s theme of “Environmental and Climate Literacy” was to create awareness about protecting nature and natural resources. While describing the Earth Day “a day of gratitude to mother earth”, PM Modi said: “It is our duty to live in harmony with the plants, animals and birds we share the earth with. We owe this to our future generations.”

“Eat less meat, opt for carpooling and unplug unused electronic devices — do your bit and make a huge difference to saving Earth,” suggested Google’s Earth Day doodle.

A lot has changed since the very first Earth Day in 1970. Back then, America’s most urgent environmental problems were smog and water pollution. In the years since, we’ve made remarkable progress mopping that up, only to confront fresh challenges like global warming and ocean acidification, transforming the atmosphere, for better and worse, reforestation…

As our knowledge of the Earth keeps evolving with each passing year. I am reminded of best new discoveries we’ve made, uncovered new geological features, about this breathing, seething, never-dull planet of ours — the only place in the universe where life is known to exist.