Theme: Just a Theory - Tribute puzzle.
17A. Online matchmaker : eHARMONY
22A. = : EQUALS SIGN
34A. "U Can't Touch This" rapper : MC HAMMER
46A. Looked ready to fight : SQUARED OFF
53A. See 42-Down : EINSTEIN
42D. With 53-Across, physics Nobelist who devised the formula that begins 17-, 22-, 34- and 46-Across : ALBERT
Argyle here. Rows: 15, Columns: 14, Words: 73; did you notice? A bit more serious than Clement's first puzzle. link here.
Albert Einstein's paper “Does the Inertia of a Body Depend Upon Its Energy Content?” was published in the journal "Annalen der Physik" on November 21, 1905.
Across:
1. Popeye's nemesis : BLUTO
6. Electrolux, briefly : VAC. (vacuum cleaner)
9. Nos. on beach lotion labels : SPFs. (Sun Protection Factor)
13. Pachelbel composition : CANON
14. Tel Aviv's country: Abbr. : ISR. (Israel)
15. Opera highlight : ARIA
16. Small thicket : COPSE
19. "Look before you __" : LEAP
21. School course with slides : BIOLOGY
25. Lawyer's charge : FEE
26. Carry with effort : LUG
27. Partner of hither : YON
28. For the lady : HERS
29. Inlaid designs : MOSAICS
32. Apple music players : iPODS
36. Web destinations : SITES
38. Worded : PHRASED
42. They're usually divided into scenes : ACTS
43. Wisecracking West : MAE
44. MLB's Indians, on scoreboards : CLE. (Cleveland Indians)
45. __ Vegas : LAS
50. Obscure from view, as in an eclipse : BLOT OUT. or Wite-Out, as in ....
52. Continually : EVER
55. Vacant : EMPTY
58. San __: Riviera resort : REMO
59. Ambient music pioneer Brian : ENO
60. Bete __ : NOIRE. French: literally, black beast (a person or thing strongly detested)
61. Tijuana three : TRES
62. Athletic center : GYM
63. Pig's sniffer : SNOUT. Ever had them pickled?
Down
1. Secretly keep in the email loop, for short : BCC. Blind carbon copy; semi-CSO to our leader.
2. Philosopher __-tzu : LAO
3. Disconnects from the outlet : UNPLUGS
4. Where sailors go : TO SEA
5. Ryan or Tatum : O'NEAL. Father and daughter actors.
6. Compete : VIE
7. Hearth receptacle : ASH BIN
8. Online guy with a list : CRAIG. Started in 1995.
9. O.T. prophet : SAML. (Samuel)
10. Reviewed for errors : PROOFED
11. Piano players? : FINGERS. Cute one.
12. Make a proposer smile : SAY YES. Crosses eHarmony. Also cute.
18. Director Howard : RON. Little Opie all grown up.
20. Gives a pep talk, with "up" : PSYCHS
22. Stately tree : ELM
23. Status __ : QUO
24. Slugger Sammy : SOSA
28. Bar mitzvah dance : HORA
30. Bill totals: Abbr. : AMTS. (amount)
31. Cocktail rocks : ICE
32. Announcement upon arrival : "I'M HERE!". No ice at Tinbeni's.
33. For each : PER
35. Movie-rating org. : MPAA. (Motion Picture Association of America)
36. Like large reptiles, compared to smaller ones : SCALIER
37. "My treat" : "IT'S ON ME"
39. Many a November birth, to astrologers : SCORPIO
40. Helper for Santa : ELF. I had to let this little guy go.
41. Dict. entry : DEF. (definition)
43. Problem on the Caine : MUTINY
46. Drunkard : SOT
47. Captain of the Caine : QUEEG. He was the real problem but not a sot.
48. Coin toss call : EVENS. I'd say "TAILS".
49. Exorcism target : DEMON
51. General __ chicken : TSO'S
54. __ de plume : NOM. Pseudonym adopted by an author
56. Capote nickname : TRU. Real name, Truman Streckfus Persons. Bio
57. To this point : YET
Argyle