| 100% | BIGBANG | 7 | A theory that explains the origin of the universe |
| 72% | BIGBANG | 7 | Theory that explains the creation of our universe |
| 53% | PTOLEMY | 7 | Greek, posited a geocentric theory of the universe |
| 51% | DEAD | 4 | With 8-Across, subject of a theory that claims that most of the activity on social media is generated by bots |
| 49% | AREA | 4 | ___ 51, said to be a government facility that is the subject of UFO conspiracy theories |
| 49% | COSMOLOGY | 9 | The science related to the origin of the universe |
| 48% | BIGBANG | 7 | Theory of the universe, or a hint to the starts of 17-Across and 7-, 10-, 35- and 40-Down |
| 47% | BANG | 4 | "The Big ___ Theory," American sitcom with a few episodes that refer to "The Lord of the Rings" |
| 46% | INSTEP | 6 | Part of a shoe that covers the arc of the foot |
| 46% | ORIGIN | 6 | Story that explains the birth of superheroes |
| 46% | TREK | 4 | "Star ___," sci-fi show that is a favorite of the characters on "The Big Bang Theory" |
| 46% | HEAT | 4 | ___ wave, climate condition leading to high temperatures that is a proposed theory for the extinction of dinosaurs |
| 46% | COLD | 4 | ___ wave, climate condition leading to freezing temperatures that is a proposed theory for the extinction of dinosaurs |
| 46% | DEFINING | 8 | Explaining the meaning of a word |
| 46% | INTERPRET | 9 | Explain the meaning of a dream |
| 45% | DEFINE | 6 | Explain the meaning of, as a word |
| 45% | CHARLESDARWIN | 13 | Biologist who gave the theory of evolution in "On the Origin of Species", that is depicted in the 2009 movie "Creation": 2 wds. |
| 45% | LUNISOLAR | 9 | Like a calendar that combines the positions of the 9-Across and the sun |
| 45% | BOOT | 4 | Surname for a wizarding family in the "Harry Potter" universe that is also the name for a type of winter footwear |
| 45% | SHIFT | 5 | Tectonic plate ___, movement of the earth's tectonic plates that is a proposed theory for the extinction of dinosaurs |
| 45% | FOOD | 4 | ___ scarcity, term referring to a lack of nutritional sources that is a proposed theory for the extinction of dinosaurs |
| 45% | DRYCOUNTY | 9 | Part of a state that prohibits the sale of alcohol |
| 44% | WHOA | 4 | Cry to a horse that's the opposite of "Giddyup!" |
| 44% | SEA | 3 | ___ level change, condition leading to oceanic water level changes that is a proposed theory for the extinction of dinosaurs |
| 44% | ENDPIN | 6 | Part of a cello that supports the instrument on the floor |
| 44% | SOLO | 4 | Part of a song that features one member of the band |
| 44% | COEQUALLY | 9 | In a way that's like people of the same rank |
| 44% | EVOLUTION | 9 | Theory in Darwin's On the Origin of Species |
| 44% | NECK | 4 | That part of a violin that supports the fingerboard |
| 44% | BIGBANG | 7 | Scientific theory of the universe's beginning |