What is this? Vapour trail? Unidentified?

Hi, I'm new to these boards and I've done a quick check to see if this video has been discussed on a prior thread. I couldn't find a mention. Apologies if it's a tired topic.

I was reading the 'Wormhole' thread from yesterday and was impressd that the pictures were explained so quickly. It reminded me of this video I saw on youtube Youtube's full of crap, I agree, but I couldn't readily explain this.

I thought maybe it's a firework trail that's been slowed down to appear more mysterious. Maybe some vapour trail? The stills are more interesting in the second half. I'd also advise that if you watch it, turn the sound down. The narrative is ridiculous.

So please; what is it?

uk.youtube.com...

Don't go bitching me out if it's something obvious I'll be embarrassed enough thanks!