It's Earth Day! Here are 7 ways to honor the planet

It’s been 43 years since Wisconsin Sen. Gaylord Nelson celebrated the very first Earth Day on April 22, 1970. It’s not yet a federal holiday, but Earth Day is celebrated by schoolkids from coast to coast (along with many adults).

Of course, it goes without saying that for some folks, every day is Earth Day.

Here are seven things you might not have known about Earth Day (and the spirit of environmentalism it represents):

* More than 1 billion people in 192 countries are doing something to mark Earth Day this year, according to estimates from the Earth Day Network. In Veracruz, Mexico, volunteers will clean up beaches to improve the habitat for sea turtles. In Jalandhar, India, students will plant saplings. In Seoul, fans of South Korean pop star Psy’s mega-hit “Gangnam Style” will form a flash mob to perform a variation called “Eco-style.” (You can watch them practice on YouTube here.)

* Earth Day has inspired one of Google’s most ambitious Google Doodles – an animated scene of mountains, a stream and a meadow populated by bears, fish and other creatures. You can even blow virtual dandelions with your computer mouse! Check out this “sightseeing checklist” from the doodle team to make sure you don’t miss any features.

* Climate change is a massive phenomenon, but the Earth Day Network is trying to humanize it with its “Faces of Climate Change” campaign. Click here to see pictures of people from all over the world who are concerned about climate change and trying to do something about it. You can also upload your own photo to the global collection.

* What does the Vietnam War have to do with Earth Day? The “teach-ins” staged by antiwar activists in the late 1960s inspired Sen. Nelson to call for rallies across the country to focus the public’s attention on environmental issues, according to the History Channel.

* You can take this quiz to calculate your ecological footprint. Among other things, the quiz will tell you how many Earths it would take to have enough resources to support the lifestyle you live -- had a house as big as yours, flew in planes as often as you did, ate as much meat as you eat, etc. -- if everyone else on the planet lived it too.

* If you feel daunted by how much needs to be done, watch this video from the Mother Nature Network to see how far we’ve come since the first Earth Day in 1970. (My personal favorite is this tidbit from 2006: “'An Inconvenient Truth' is released, winning Al Gore an Oscar, a Nobel Prize and a lifetime of being criticized every time it snows.”)