In the wettest winters, the marsh behind the village floods right up to the train tracks. This is the only time of year when the train line which takes you away from London is more exciting than the line that takes you towards it. The benches on what is usually the footpath along the bank are half-submerged in the middle of the flood; the kissing gates are only just peeking out; every branch of the willow in the second field after the marina is reaching down and turning into itself.

Some wires got crossed in my head at school: we were told how the moon is responsible for the daily highs and lows of water, and I extrapolated this to mean it must also be responsible for floods and droughts. On the train home in the early evening, leaning against my Dad and looking at the tiniest sliver of a new moon stood above the swollen body of water, I thought, how did THAT do THIS? What a wonder. What a dangerous thing to be allowed to come so close to.

Dad would have put me right, so I’m glad I didn’t say anything. There would probably have been diagrams. This is not to say I didn't like explanations or diagrams or knowing the truth, just that it was such an irritation to grow up later and have to know all about how soil erosion has left the fields upstream with poor water retention because of government subsidies for keeping them fallow, about poor lock maintenance, about climate change, none of which are as good as the moon.

Now that I'm an adult, complete with a 3 minute pub rant about the poor decision making displayed by the Department for Rural Affairs which I can deliver at any level of sobriety, I work at a start-up. Until recently, above the display of company-provided tampons in the toilets (which is one way you can tell it's a start-up, my previous corporate job could NEVER) was a sign that said something like:

Mooncups are a comfortable, reusable, environmentally friendly alternative to tampons or pads.
If you’d like to know more, please talk to Serena, who is a veteran Mooncup user.

The Serena of the sign was the old Head of Building Management. She left the company a long time before the sign got taken down, but I still feel like if someone mentioned Mooncups in the pub after work she’d reappear, like building managers always seem to when something needs fixing, except maybe she’d be holding a shandy.

Sometimes I only remember that I’ve had my Mooncup in all night when I’m on the way to work. Swaying on the tube, knowing that all of last night’s menses and a good chunk of this morning’s are swaying along in a silicone cup inside me, and knowing I won’t be able to do a thing about this for the next 45 minutes: it’s disconcerting.

It’s not a big problem. Unlike the Thames and its banks, I have never come anywhere close to overflowing a Mooncup.

When I was still at my previous corporate job, perched on the 8th floor of a glass building on the edge of the City, a woman messaged me to say she had read a lot of my writing. We got chatting, agreed to go for drinks. I was in an open relationship with a boy where basically anything was fine so long as you told the other person. I didn’t say anything in advance because I didn’t think this was a date.

She’d suggested the bar, in Soho, easy for us to walk to from our respective workplaces. It turned out to be a cocktail bar. I wasn’t prepared for this, underdressed in my work clothes: soft dress, cardigan, flats. She was elegant, all in black. She did not appear to be an axe murderer. 

She put her card behind the bar when we got there and insisted on paying for everything. We talked for hours, worked through the cocktail menu. She was married and had a similar open set-up with her wife. It turned out I sort-of-knew her sort-of-boyfriend. She made me hash out some sexual ethics I hadn't thought through. I still refer to principles from that conversation today. We talked about sex a lot. I made her laugh. Each time she came back with another round of cocktails things felt more and more datelike.

The bar was in a basement, but we were right by the door. We didn’t realise that the metal walkway over the stairs functioned like a Faraday cage, blocking all phone signal, until we stumbled out and found she had twenty safe-call messages from a wife who was increasingly concerned I'd turned out to be an axe murderer.

I had a single text from the boy. I felt a surge of guilt for having worried him, until I remembered that he didn't know he ought to be worrying at all, at which point I felt a surge of entirely different guilt. 

His text said: OH MY G-D LOOK AT THE MOON. 

The moon was hanging low, framed by the buildings either side of Seven Dials. Huge. Next day, the internet would tell the boy it was a blood moon.

The woman rang her wife to apologise profusely and reassure her about the lack of axe murdering on my part. I texted a lot of hearts to the boy.

I admired the moon with the woman. We left in opposite directions, her towards the river and me away from it. I didn't tell the boy about the drinks, but neither did I see the woman again.

Menses are such a good colour, a red that really means itself. The way they cling. While Wikipedia is not helpful on this subject, I would not be surprised if they turned out to be a non-Newtonian fluid. 

My flatmate refers to my slow-cooker as my cauldron because it’s shaped like one and it bubbles. As far as I’m concerned, the only true cauldrons in the flat are our Mooncups. This is because of a line from Mary Ruefle's essay Poetry and the Moon

It has been proved, using highly sensitive equipment, that even a cup of tea is subject to lunar tides. 

Several other facts in Madness, Rack and Honey, the book where this essay appears, have turned out not to be particularly true (in On Theme she says that the Shakers revolutionised medicine by inventing pills, which as far as I can tell is outright bollocks) and so I have not checked this one, just in case. If you are reading this and have any solid info on the hydrodynamics of cups of tea, please do not share it with me. Yes, Dad, that includes you.

Assuming Ruefle's fact is true: what distinguishes a menstrual cup from a tampon or a pad or those absorbent knickers which let you pretend the whole thing isn't happening is that, since the cup is not absorbent, the liquid it contains will still be subject to lunar tides. Infinitesimally, the moon could be pulling on the core of your body.

Here is a set of facts that nobody will bother to check unless I'm murdered before this is published: I have drafted the bulk of this essay on the train back from a gig in Birmingham. It is half eleven by now, and the train will not get into London until past midnight. There is a man sitting across the aisle from me. He is wearing a suit and a wedding ring and is white and in his thirties and has quite a boring face. He has been there for my whole journey.

Almost every time I have looked up he has been staring at me. I checked the wedding ring situation on one of the few occasions he was looking elsewhere, because I didn’t want him to see me looking to see if he was married.

This is a Pendolino train and the seats are tall, so I'm not certain that we are alone in the carriage, but we are the only two people I can see.

These facts are not really to do with the moon, except that they have been true while I have been writing about the moon, and I want to acknowledge them.

But there is also the fact that like the moon this act probably surfaces every night. Maybe even this same man’s stare rises and hovers over someone on this same train every night, depending on how often he travels late.

And there is also the fact that every time someone travelling alone has ever been stared at by a man late at night, anywhere in the world, the moon has stood high over the watcher and the watched, witnessing. And that sometimes I fantasize that eventually the moon will have had enough, and will do something with all of this information. That eventually THAT will do THIS, and the THIS that the THAT will do will involve blood. A lot of blood, as is the moon's right.

ANNA KAHN is the host of the Unfinished Edits podcast. She's a Barbican Young Poet and a former member of the Roundhouse Collective. Her work has been published by The London Magazine, Right Hand Pointing, and The Rialto, amongst others. By day she does something inexplicable in tech.