Earth Day is Friday, and it’s a time to reflect on the beauty of Mother Nature and learn ways (and teach others) to keep her healthy. Environmental activists the world over will try to carry their message to millions of people in hopes of encouraging environmental sustainability.

The first Earth Day was celebrated in 1970 on college campuses across the U.S. and was the creation of Gaylord Nelson, a Wisconsin Democratic senator who thought up the idea watching the student-led anti-war protests of the 1960s. For many, April 22, 1970, marks the start of the modern environmental movement.

Here are 16 sayings — inspirational, wise and funny — to help you make the most of Earth Day.

1. “A true conservationist is a man who knows that the world is not given by his fathers, but borrowed from his children.” — John James Audubon ​

2. “Live in each season as it passes; breathe the air, drink the drink, taste the fruit, and resign yourself to the influence of each.” — Henry David Thoreau

3. “Look deep into nature, and then you will understand everything better.” — Albert Einstein

4. “Only when the last tree has died and the last river been poisoned and the last fish been caught will we realize we cannot eat money.” — Cree Indian proverb

5. “Environmentalists have long been fond of saying that the sun is the only safe nuclear reactor, situated as it is some ninety-three million miles away.” — Stephanie Mills

6. “For 200 years we’ve been conquering nature. Now we’re beating it to death.” — Tom McMillan

7. “In every walk with nature one receives far more than he seeks.” — John Muir

8. “An understanding of the natural world and what’s in it is a source of not only a great curiosity but great fulfillment.” — David Attenborough

9. “A nation that destroys its soils destroys itself. Forests are the lungs of our land, purifying the air and giving fresh strength to our people.” — Franklin D. Roosevelt

10. "Nature does not hurry, yet everything is accomplished.” — Lao Tzu

11. “Nature, to be commanded, must be obeyed.” — Francis Bacon

12. “The earth is what we all have in common.” — Wendell Berry

13. “You can’t be suspicious of a tree, or accuse a bird or a squirrel of subversion or challenge the ideology of a violet.” — Hal Borland

14. “To see a world in a grain of sand, And a heaven in a wild flower, Hold infinity in the palm of your hand, And eternity in an hour.” — William Blake

15. “As we grow older we should become not less radical but more so.” — Margaret Laurence

16. “Here is your country. Cherish these natural wonders, cherish the natural resources, cherish the history and romance as a sacred heritage, for your children and your children’s children. Do not let selfish men or greedy interests skin your country of its beauty, its riches or its romance.” — Theodore Roosevelt