Related Clues:

• Workout unit
• "Fancy that!"
• "I'm impressed!"
• "Shucks!"
• "Go right, mule!"
• Exclamation in 17, 23, 50 and 61-Across
• Physics 12-Down
• "Oh my!"
• "No kidding!"
• Bit of energy?
• Piece of work?
• Awed one's reaction
• Take the right course
• Right call
• Sir Isaac of science