1. Leonardo DiCaprio

LeoDio, if you could imagine, is known for much more than his unnecessary death in The Titanic. At the early age of 24, for instance, he established the Leonardo DiCaprio Foundation. Despite the pretentiousness of naming an organization after yourself, the org has done much to advance the name of science and all that sails beneath its name.

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The main aim of Leo’s nonprofit is to help protect nature and wildlife around the world. It is also a strong motivator for conservation, supporting actions to reduce global climate change and raise funds for those affected by natural disasters. His efforts have been recognized nationally, leading to him being recognized as the U.N. Messenger in Peace with an emphasis in climate change.

2. George Clooney

George Clooney is another famed member of the U.N. Messengers of Peace. Along with his compatriot Leonardo DiCaprio, he has helped raise money Haiti when they suffered that horrible 7.0 earthquake in 2010. He did this through the organization Hope for Haiti. Thanks, George!

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Clooney is such a strong advocate for the things he supports that he has even been arrested for protesting. In 2012, he was protesting the war in Darfur outside the Sudanese embassy in Washington D.C. This 2012 event likely didn’t affect his acting career in any negative way, since he’s starred in several movies since then.

3. Mark Ruffalo

Having played in roles ranging from the temperamental green Hulk to a tenacious journalist for the Boston Globe, Mike Rezendes, Mark Ruffalo has done it all. But he’s done more than just act the role of numerous different characters. Of the more science-y things that Ruffalo has supported includes clean energy and anti-fracking measures—all through his organization Water Defense.

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He is also a well-known supporter of other environmental organizations like The Solution’s Project. The Solutions Project is primarily aimed at attempting to get everyone to use nothing but clean energy and clean energy only. For his many efforts, he was awarded The Humanitarian Award.

4. Angelina Jolie

Angelina’s motivation to help the planet came shortly after her travels through Cambodia while filming the 2001 film Tomb Raider. For the most part, her efforts were focused on humanitarianism. Her efforts were so notable that she became a United Nations High Commissioner for Refugees (UNHCR). Her main aim was to end violence against children.

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Along with her partner at the time, Brad Pitt, Jolie started the Jolie-Pitt Foundation to help humanitarian endeavors around the world. They came up with the idea shortly after having met on the set of Mr. and Mrs. Smith. So if there was anything good to have come of that movie, at least it was something that would help the world.

5. Brad Pitt

Independently from his partner at the time (Angelina Jolie), Pitt formed the Make It Right Foundation. The main aspiration of this project was to build affordable green homes for those in need. Among the more notable events held by this charity were fundraising campaigns in the wake of hurricane Katrina, where Brad himself would sometimes go help build.

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Pitt has met with politicians as inimitable as Barack Obama, managing to raise millions in funds for those in need. He has done so much, in fact, that he has been nationally recognized with an award from the U.S. Green Building. His support of science, then, comes in the form and manufacture of green, sustainable homes.

6. Matt Damon

Matt Damon is known for more than just his superlative role in Good Will Hunting and other cinema-changing films. He has also become a strong advocate of clean water initiatives. The most salient of these was the founding of his organization H2O Africa, an org dedicated to providing African communities with clean, sanitized water.

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In 2009, Damon joined with two other organizations with similar aims to provide clean water for all countries. He also worked with several other famous actors, including Brad Pitt, Don Cheadle, and Jerry Weintraub, to start Not On Our Watch. The group’s aim is to prevent genocide from unfolding in other nations.

7.  Don Cheadle

Like Angelina Jolie, Cheadle’s move toward humanitarianism and science policy advocacy came with the filming of a movie. In his case, this movie was Hotel Rwanda, a film that articulated the many horrors and tragedies of the mid-90s Rwandan tragedy. With knowledge, comes empathy. Stupendous wealth is probably also a factor.

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His efforts were so appreciated that he was recognized with the BET Humanitarian Award. But beyond these initial protestations, Cheadle has also attempted to protest against war crimes in Darfur. He also shared a Summit Peace Award (which is distributed by the Nobel Peace Prize Laureates) with George Clooney for these efforts.

8. Robert Redford

Robert Redford is like LeoDio in that he advocates strongly for conservation and ways to ameliorate the effects of climate change. He was an early fighter on this front, in fact, and was responsible for having organized a meeting for climate scientists in the 1980s. Whether it was him or his assistants who did the organizing, that’s beyond the point: he helped get it done.

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Moreoever, he, along with his son, James, started the organization The Redford Center, which aims to create films with a focus on environmental issues like ecosystem restoration. Watershed, for instance, was a film they had made that focused specifically on restoring the Columbia River Basin.

9. Stephen Colbert

This late night show host has done much for the world of science through subtle (and sometimes glaring) advocacy. In several instances, he has pro-science guests and themes that differ from most other late night show hosts. He has had segments, for instance, where he has attempted to cajole scientists into naming things after him.

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In one set of shows, for instance, he attempted to pester NASA into naming some space equipment after him. He also tried to convince several biologists to name newly discovered species after him. In this latter attempt, he was successful. He has had a spider—Aptostichus stephencolberti—named in his honor.

10. James Randi

James Randi was a popular magician and escape artist during the 40s, 50s, and 60s. Among the many things he’s done for science, the most notable was his formation of the James Randi Educational Foundation. This foundation was built specifically to advance the name of science and skepticism in the modern era.

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Randi attempts with his organization to debase the likes of the pseudoscientific, paranormal, and other unscientific shenanigans around the world. He even hosted the Million Dollar Challenge, which was constructed to entice so-called psychics to prove their “skills” in a scientific venue. Shockingly, no one has been able to cash in on this challenge.

11. Seth MacFarlane

Seth MacFarlane has done numerous things to advance the name of science. In one popular way, for instance, he helped produce the revamp of the famous Cosmos series for Fox. He also paid an undisclosed amount to have several of Carl Sagan’s personal work to be published in the Library of Congress so that they’ll be available for everyone to read.

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Carl Sagan, for those who don’t know, was responsible for writing the book Cosmos (after which the series is based) and was one of the first so-called science popularizers. He was an astrophysicist at Cornell University in Ithaca, New York. His influence has spread to many media moguls, a gift that keeps giving.

12. Tom Hanks

Tom Hanks initially had dreams of becoming an astronaut. Unfortunately, this never happened. But his love for space and its contents didn’t end with that dying dream. He has, for instance, spend most of his adult life supporting NASA. He has also produced documentaries on space landings and other astronomical endeavors.

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His efforts have been so prominent, for instance, that he was given the Douglas S. Morrow Public Outreach Award in 2006. The award is only given to those with a strong penchant for science advocacy. We can thank, then, Tom Hanks with a hearty applause from the scientific community.

13. Emma Thompson

This UK actress has done nearly as much for environmental advocacy as she has for her movies. One of the programs that she supports most fervently is the effort to reduce the effects of climate change. Her notoriety, gleaned from things like the Harry Potter series, has helped her to advance this agenda.

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Among the more popular things she has said: “We’re perfectly capable of sorting this out, we just need to get it done.” While this statement might seem a little oversimplified considering the scale of the problem, it indicates that she’s hopeful. And that hope can easily spread to and motivate others.

14. Arnold Schwarzenegger

This man has done it all. He’s been Mr. Universe, the Terminator, and the 38th governor of California. But he was also a movie star, starring in films as life-changing as Predator, Commando, Eraser Man, and Total Recall. If you haven’t seen any of these, I would recommend that you stop what you’re doing and watch them now. Just do it.

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But other than his far-reaching litany of jobs and hobbies, Schwarzenegger is also a firm supporter of climate change initiatives. He has lobbied for much political action in California, for instance, where he was governor. What he should have done was take global warming on head-on. I mean, he has the biceps to do it.

15. Jessica Alba

Other than her role alongside Bruce Willis in Sin City or her co-starring role in Into the Blue, Jessica Alba has been busy busting her businesswoman chops. More relevantly, she’s been busting her businesswoman chops in the world of eco-friendly products. This ranks her as one of our science-friendly advocates—at least in terms of the eco-friendly.

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Her business, The Honest Company, sells everything from diapers to beauty products—and does so with a clean conscience. The aim of the company is to produce products that are eco-friendly while simultaneously being ethically constructed. She differs, in other words, from the likes of Walmart and Amazon, where ethical practices are sometimes in short supply.

16. Aston Kutcher

Many actors, much to the chagrin of the science-friendly, will dismiss genetic engineering and other biotech as anathema to the well-being of our 21st-century society. They claim that it’s detrimental in some way—something like an unnatural poison that we’re imposing on our otherwise healthy bodies. Not so, according to the scientific literature.

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Ashton Kutcher, fortunately, is someone who realizes this. He has, among other things, supported genetic engineering and other scientific endeavors from the start. In one tweet, for instance, he brings attention to crispr, the gene-splicing tool with potential to ameliorate many ills given to us by our genetic inheritance.

17. Bill Gates

Admittedly not a celebrity for his good looks or on-screen acumen, Bill Gates made his name as an early magnate in the tech world. Having founded Microsoft with his partner Paul Allen, Gates is responsible for having pioneered early innovations to the computer. This brought him a lot of money.

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But, also unlike most of the rich, famous people, Gates has decided to donate a substantial portion of this massive wealth to charity. And the charities he chose focus on scientific endeavors like distributing malaria nets and HIV medication to those in desperate need. He also regularly fraternizes and promotes the work of other scientists. Way to go, Mr. Gates!

18. GZA

Known by his friends (and maybe even some of his enemies) as “The Genius,” this Wu-Tang Clan founding member is known for his affinity of physics and, more specifically, quantum mechanics. He has an album entitled “Dark Matter,” for instance, which attempts to outline some of these themes. That’s unusual for a musician.

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For science and the public, however, his reach attempts to expand even further. He is known for working with physics teachers and communicators in the New York area, for instance, to better enhance the science education of New York’s youth. He is definitely an influential science advocate, then. And for that we thank him.

19. Will.i.am

Another musician in favor of all things science is Will.i.am from the Black Eyed Peas. This judge for “The Voice” launched an initiative in 2013 to better the teaching of science, technology, engineering, and math for London school children. And how much did he invest into the program? 500,000 euros (about 570,000 us dollars).

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This generous program places Will.i.am as one of the celebrity promoters of science. While others might lend their support through tweets and blurbs, Will.i.am does so through donations. He is indeed one of those who puts their money where their mouth is. And is this case, his mouth is in the realm of science advocacy.

20. Alan Alda

Popular for his role in shows like M*A*S*H and The West Wing, Alan Alda made a healthy career out of acting. However, his fascination with science led him to create many science-oriented TV shows. Among these are series like Scientific American Frontiers, The Human Spark, and Brains On Trial.

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His science communication affinities have been so popular that he’s earned the Sagan Award, a prize divvied out to those who are thought to have made a significant contribution to the world of science through publicity. Hopefully, he continues along this gleaming career trajectory, promoting both scientific values and the worldview they support.

21. James Cameron

James Cameron is well known for several of his cinematic ventures. He produced blockbusters like the Terminator, Titanic, and Avatar. But other than his major movie hits, Cameron has also done much for the world of science. He’s one of only three people, for instance, to have taken a submarine to the bottom of the Mariana Trench—the deepest point on planet Earth.

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His biggest point of advocacy, then, as you may have guessed, is ocean science. This love for science he has brought to his films, making them curious endeavors for the sci-fi curious. And this fascination will likely inspire many a future scientist to go on and discover something new and exciting.

22. Jane Goodall

Unlike many of the other people on this list, Jane Goodall earned her fame as an actual scientist. A primatologist by trade, Goodall became known for her activism in animal and human rights. Her work with chimpanzees has made both major scientific and public achievements, changing our view humans and nonhuman primates.

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But other than her work with our closest living primate cousins, Goodall is a strong advocate of science education. Through the Jane Goodall Foundation, for instance, she’s run programs in Africa focused on the development of conservation projects and humanitarian efforts. She also has appeared on numerous talk shows as an advocate for science and scientific education.

23. Jack Johnson

This musician has done much more than lend his mellifluous voice to the masses. He’s also worked with conservation companies to protect endangered species everywhere. He has partnered with the Australian Marine Conservation Society, for instance, which works to—among other things—protect endangered sea turtles. He won’t be using those turtle shell picks anytime soon, then.

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Among the other science-y things that Johnson supports are the groups 1% For The Planet, Climate Counts, Heal the Ocean, Live Earth, and Waterkeeper Alliance. These different organizations are oriented toward helping the environment through conservation and scientific innovation. So we can thank Jack Johnson for all his good.

24. Daryl Hannah

Daryl Hannah is known for her role as the one-eyed (spoiler alert: eventually no-eyed) antagonist in the Quentin Tarantino film, Kill Bill. But she’s also known for her efforts to advance environmentally friendly fuel sources. She is the founder of a company that focuses on sustainable biodiesel, for instance (aptly called the Sustainable Biodiesel Alliance).

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Among the other science endeavors that Daryl supports are Mission Blue, the Action Sports Environmental Coalition, and the Environmental Media Association. These different organizations are focused on conservation and building a clean future. If she gets her way, we’ll live in a better world, that’s for sure.

25. Pearl Jam

One of the earliest bands in the grunge era, Pearl Jam became widely known for Eddie Vedder’s growling vocals and the band’s overall 90’s vibe. But they later became known for more than that. Having never lost an affinity for conservation, the band has dedicated many of their resources to environmentally friendly practices.

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As one example, the band has committed themselves to producing all of their albums through ethical means, ensuring that they are produced without toxins, free of poor labor practices, and using the least amount of resources to deliver them as possible. Ultimately, they are aware of their impact on the environment and are trying to ameliorate their negative impact.

26. Gisele Bundchen

This supermodel has done more for the world than just advertise fancy dresses and size zero bikinis. She’s also helped raise awareness about green living in general. She has, for instance, created a totally green flip-flop line. She’s also helped raise funds for the preservation of the Amazon and Atlantic Rainforest.

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Among her other projects includes things like the Clean Water Project, which had been formulated by her and her family to restore the natural habitats in her hometown of Horizontina, Brazil. Her attempts were noticed so much that she was recognized by Harvard’s Center for Health and Global Environment and named the Global Environmental Citizen of 2011.

27. Edward Norton

Edward Norton is definitely one of the most versatile actors on this list. He’s played—like Ruffalo—a bulky green Hulk, the schizophrenic founder of an underground fight club (unlike Ruffalo), and a litany of characters in-between. But other than these roles he’s played in many major films, he’s played a role in conservation and clean energy promotion.

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Of the many projects that Norton’s been involved in, he’s hosted a Planet Earth episode entitled “Strange Days” and put forth much support for the Wilderness Society, which aims to preserve biodiversity everywhere. He’s also part of a group called Friends of the High Line, which aims to preserve green space in New York City.

28. Dave Matthews Band

Like Pearl Jam, the Dave Matthews Band attempts to make their impact on the Earth as green as possible. While we don’t know about the quality of their CDs, we do know that the generators they use at concerts are powered by biodiesel, that they use recycled and composed materials to build their stages. They also use some of the proceeds from their concerts to replant trees and build wind turbines.

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One of the more recent pursuits of the band has been to work with UPS to engage in more green methods of transport for their equipment. The band also founded something called the Green Music Group, which aims to press the music industry into more green practices. The group has been joined by people like Linkin Park, Sheryl Crow, and Willie Nelson.

29. Pierce Brosnan

Apparently equipped with the nickname “Best-Dressed Environmentalist,” Pierce Brosnan is a fervent environmentalist and conservationist. For one, he serves as a board member for many different environmental organizations. Just to name a few, he’s on the Natural Resources Defense Council, the California Coastal Protection Network, and the Sea Shepherd.

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He’s also been inducted into the Environmental Hall of Fame for his attempts to inform people about illegal whale hunting. And, like Norton, his motivations to protect the environment have taken him into the world of voice acting, where he’s performed for things like Planet Earth. You should definitely keep an eye (and an ear) on his work.

30. Adrian Grenier

Another green activist, Adrian Grenier has attained numerous awards for his advocacy. He’s been given the Global Green USA award, for instance, and the Opportunity Green award. Each of these was given for his work on SHFT, a website that advertises the many ways in which you can live green through modest changes to your daily life.

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He also hosts a show entitled Alter Eco, which has the same aim. The show is hosted on a channel called Planet Green, which has aim far broader than just quick changes to daily life. And, as icing on the cake, he drives a Prius like many of us, but also lives in a home powered exclusively by solar power. If only we all we so lucky.