Historical clue formulations

• ___ 1 (speed of sound) — 2025-12-01
• Scientist whose "number" is a dimensionless ratio — 2025-06-27
• Supersonic speed number — 2025-01-06
• Kind of number represented by the equation M = v/c — 2024-09-20
• Physicist Ernst — 2023-12-25
• Ernst who studied sonic booms — 2023-03-29
• Speed of sound — 2022-01-22
• It's calculated relative to the speed of sound — 2021-08-27
• Speed measure — 2020-02-20
• South American landmark whose name means "old peak" — 2019-05-16
• Eponymous physicist Ernst — 2019-03-13
• Eponymous physicist Ernst — 2017-01-20
• Speed-of-sound ratio — 2015-09-16
• See 13-Down — 2013-08-07
• Physicist Ernst who studied shock waves — 2012-03-16
• Name often followed by a number — 2010-11-21
• Supersonic unit — 2007-03-07
• Word often followed by a numeral — 2006-03-22
• Number associated with a boom — 2006-02-04
• Physicist with an eponymous number — 2003-05-02
• Jet speed unit — 2001-09-17
• ___ one — 2000-11-01
• Speed-of-sound number — 1999-07-20
• Jet speed measure — 1998-11-17
• Flight ratio — 1998-09-23
• Speed ratio — 1998-05-20
• Word before 1 or 2 — 1997-11-15
• Airspeed unit — 1996-02-19
• High-speed number — 1995-10-17
• Supersonic number — 1995-09-19
• Kind of number — 1995-04-23
• Physicist Ernst — 1994-09-18