Narrating a science documentary is no easy task. One has to make complex material viscerally and emotionally appealing. One has to get both facts and intonation correct. One has to speak quietly so as not to scare the Gibbons. Truth be told, there are only a few dozens humans who have ever done this work with panache.

Who are the best of the best? Voice quality, timbre, intonation, and acting ability are all important, but the most paramount trait belonging to any documentary narrator is an audible and believable connection to his or her material. Even Jacques Cousteau’s thick French accent didn’t mask the obvious respect he had for ocean life and small red caps. The optimism in Carl Sagan’s voice made him a more engaging tour guide to the cosmos than Neil deGrasse Tyson, who can’t quite shake his skepticism, has become.

It’s little factors like this that separate the good from the truly great.

12) Tilda Swinton

Major Documentaries: BBC’s Galapagos

Vocal Strengths: Androgynous tone, slight high-class British accent, keen acting skills, general otherworldliness

Tilda Swinton’s voice is so powerful that even when describing a car, as she is in the above clip, she seems transported by what she’s saying. On Galapagos, she was able to make the islands, full of unusual wildlife, sound ethereal and mystical. She may not have a colloquial enough voice for more casual projects, but if a documentary’s subject matter has any bit of mystique to it, Swinton can do it justice.

11) John Hurt

Major Documentaries: BBC’s Human Planet

Vocal Strengths: British accent, sly tone, an affectation that makes the viewer feel as if Hurt is realizing things about the footage at the same time as his audience

Hurt has a voice that’s perfect for describing anything ancient. Every situation sounds perilous when he narrates it, and he occasionally turns up his sentences at the end, in mock surprise.

10) Sigourney Weaver

Major Documentaries: BBC’s Planet Earth (when broadcast to American audiences), Discovery Channel’s Why Dogs Smile & Chimpanzees Cry, BBC’s Gorillas Revisited, The National Resources Defense Council’s Acid Test

Vocal Strengths: Fame (Weaver was cast as the American narrator for Planet Earth because her voice is so iconic to American viewers), acting skills (she whispers through intimate nature scenes, as if crouching in the forest with the viewer), emotional timbre and resonance

Sigourney Weaver may have had a career in anonymous documentary narration if she hadn’t become an international celebrity so quickly. Her voice has a unique texture, and a smidgen of androgyny that frames nature scenes well. Since her primary fame comes from onscreen acting, Weaver has only led her narration skills to causes she cares about, and this passion comes through in her voice.

9) Patricio Guzmán

Major Documentaries: Many documentaries on Chilean history, 2015’s The Pearl Button

Vocal Strengths: Deep resonance, a sense of rhythm, lyrical Spanish, emotional connection to his subjects

Before this year, Guzmán’s entire narration career was spent making films on Chilean history and culture. His first foray in nature documentaries is notable because he maintains the same qualities he demonstrated in his earlier filmography: control of emotion, and a lyricism that almost sounds musical. Also of note: he is the only documentary narrator on our list who does not speak in English.

8) Neil deGrasse Tyson

Major Documentaries: NOVA: The Pluto Files, The Inexplicable Universe: Unsolved Mysteries, Cosmos: A Spacetime Odyssey

Vocal Strengths: Dynamic tone, rich resonance, expertise in his field

Neil deGrasse Tyson was always famous among those in his field, and fans of his scientific critiques and public interrogations of popular culture. In 2014, deGrasse Tyson took the Cosmos helm and rocketed himself into much larger fame, becoming the new voice of science-minded skeptics. Though he’s not quite at the caliber of Carl Sagan, deGrasse’s Cosmos is worth a watch.

7) Tamara Bernier

Major Documentaries: Discovery Channel’s The Baby Human

Vocal Strengths: Light and feminine tone, good sense of timing, sense of humor

Tamara Bernier is an unusual, and unique, choice for this list, but her narration work on Discovery Channel’s Baby Human is both important and fun to experience. Without Bernier’s warm, lithe dialogue, some of the studies conducted on children in the documentary could have seemed careless, or even cruel. Bernier leads her audience through the psychological developments of the human child with care, infusing her voice with a laugh when appropriate, and with a concerned, almost maternal tone in other cases. On certain subjects, Bernier could, and should be, a go-to narrator.

6) Kenneth Branagh

Major Documentaries: Many historical and cultural documentaries, BBC’s Walking with Dinosaurs, Walking with Beasts, Walking with Monsters

Vocal Strengths: Superior acting abilities, classical training, sense of humor, high-class British accent

Branagh’s extensive Shakespearean training make his narration skills top-notch, although it’s a pity that his dinosaur-themed projects for the BBC haven’t aged well.

5) Morgan Freeman

Major Documentaries: The Smithsonian’s Cosmic Voyage, Science’s Through the Wormhole, Discovery Channel’s Curiosity, Island of Lemurs: Madagascar, March of the Penguins

Vocal Strengths: Exceptional tone, vibrato, his role as the human mouthpiece of the one true God

Morgan Freeman’s only downfall as a narrator is that his voice is instantly recognizable. In some cases, like the runaway hit that was March of the Penguins, Freeman’s involvement only makes a project more marketable. If a documentary needs to be about its subject, and not about the narrator at the controls, Freeman has to be excluded. Still, he has one of the most pliant and pleasant voices in cinematic history, and any documentary narrated by him is sure to be enjoyable.

4) Carl Sagan

Major Documentaries: Cosmos: A Personal Voyage

Vocal Strengths: A mix of intellectual expertise and childlike wonder, willingness to sound silly, familiarity with subject

Carl Sagan was one of a kind in many ways. He was a gifted screenwriter in addition to being a prolific and influential scientist, and his gift for poetry and emotional expression made him a fantastic narrator when he hosted Cosmos back in the 1970s. He was a rare combination of both orator and scientist, and his narration is still some of the best.

3) Werner Herzog

Major Documentaries: Many cultural and historical documentaries, Handicapped Future, Land of Silence and Darkness (on deafness and blindness), Fata Morgana (on mirages), How Much Wood Would a Woodchuck Chuck (on the linguistics of fast-speaking auctioneers), The White Diamond (on aviation), Encounters at the End of the World (on Antarctica)

Vocal Strengths: Iconic, intellectual-sounding German accent, gravel-y tone

Fewer documentarians have even approached Herzog’s prolific career. For a man with a grave, German-accented deep voice, he has a noticeable sense of humor (as illustrated in his cameo appearance on Rick and Morty). There are those who swear by his films as the best documentaries ever made, and after listening to Herzog for a few minutes, it’s easy to see why.

2) Sir David Attenborough

Major Documentaries: There are literally hundreds of science and nature documentaries featuring Attenborough’s voice. His first, Coelacanth, was produced in 1952. This year he’ll release Great Barrier Reef with David Attenborough.

Vocal Strengths: International fame, tone control, sense of humor, approachable-sounding British accent

Many would consider it heresy that we’re not ranking Attenborough at number one, but we’ll get to that. As a narrator of historical events and cultural happenings, Attenborough is in a league of his own. He’s beloved by the British people, as well as documentary-fans all over the world, and his pleasant, grandfatherly voice is one of the most comforting sounds ever recorded. Though he has had a considerable career in science and nature documentaries, one might argue that they are not his strong suit. It’s in his descriptions of human stories, historical and mythological, where Attenborough’s voice really shines.

1) Jacques Cousteau

Major Documentaries: There are, again, literally hundreds of documentaries featuring Jacques Cousteau’s voice. Series titles include The Undersea World of Jacques Cousteau, Oasis in Space, The Undersea World of Jacques Cousteau II, North American Adventures, Cousteau’s Amazon Series, and Cousteau’s Rediscovery of the World I,II, & III

Vocal Strengths: Iconic French accent, emotional timbre and tone, passion for his subject matter

Although Attenborough may have Cousteau beat when it comes to familiarity, Cousteau’s lifelong passion for undersea exploration, wildlife, and the mysteries of the deep make him the greatest science documentary narrator the world has ever known. For one, his French-accented speech sounds methodical, and he rarely wavers. Second, he dedicated his life to the subjects of his films, and it’s easy to hear how much he cares about the ocean. “People,” as Cousteau said, “protect what they love,” and Cousteau loved nothing more than the sea.

He was the ideal science-documentary narrator because the subject came first. Though his peculiar sense of style, and his nomadic, seafaring nature made him a pop culture personality, the heart of his filmography is exploration, and in capturing and sharing images of the ocean with as many people as he could reach.