What's going on with this junction box?

Post date: 2022-01-24 10:16:34
Views: 187
I removed a ceiling light in my apartment only to discover a junction box with wiring I did not expect. Photo here. Left to right: two-strand white wire; four-strand blue wire; single-strand red wire.

This is an old (late 1960s) apartment building in NYC, and I'm all but certain the box dates to that time. The white and red wires were connected to the old lamp. It's the blue wire that I'm confused by. (All wires had wire nuts before I removed them.) I was hoping to see a green grounding wire, but alas.

So, what's up with the blue wire? Do I need to be calling in an electrician here? Thanks for your advice.
Number of Comments
Please click Here to read the full story.
 
Other Top and Latest Questions:
UK PM Keir Starmer suffers major blow after his party comes third in key vote
Where can I ask the MetaFilter board all my burning questions?
U.S. and Iran wrap up 'most intense' nuclear talks with no deal — more negotiations ahead
UBS turns bullish on Palantir, says buy the dip on this clear AI winner
Anthropic faces lose-lose scenario in Pentagon conflict as deadline for policy change looms
OpenAI's Altman admits defense deal 'looked opportunistic and sloppy' amid backlash
Iran war live updates: U.S. embassy in Riyadh hit by drones, Trump promises response 'soon'
Movie: A Useful Ghost
Monarch: Legacy of Monsters: Cause and Effect
Saturday Night Live: Connor Storrie/Mumford & Sons