I’ll set the scene. There will be a man and a woman and they are having sex. Up against a wall, in a bed, in a car, anywhere. Vertically, horizontally. Clothed or unclothed. None of that matters, because the outcome will be the same. Within a minute, usually, the man and woman will have an orgasm at the same time. It will be visible, spectacular, satisfying. Then perhaps, she will have another and another and another.

This scene will be familiar because it has been enacted ever since sex was allowed onscreen. But it is fiction. Not because women can’t have multiple orgasms. But if they do, it is unlikely to be because of thrusting. That’s if they get an orgasm in the first place.

The orgasm. “A feeling of intense sexual pleasure that happens during sexual activity,” according to the NHS. That much is known. But dive any deeper into the science of women’s genitalia, and how they work, and there will be surprises. We’re still in a black hole of not knowing very much about the sexual health and mechanisms of half the population. A few things that scientists and academics are still fiercely debating: how a female orgasm is triggered, what it does and what it’s for. Things are better than they were in the 19th century, when male gynaecologists examined women while standing behind a cloak. But in the late 1970s, medical men were still having earnest discussions in the pages of medical journals about whether menstruating women emitted a poisonous substance called menotoxin, that made flowers wilt. The US National Institutes of Health only set up a programme to research vaginal health in 1992 – the male orgasm was first researched a century earlier.

There are just nuggets of information for women: a paper from the 1930s establishing that women reported having several orgasms. In the 1960s, studies by the superstars of sexology, Masters and Johnson, and others that found 14-16% of women had multiple orgasms. Or they said they did: proper analysis of even the single female orgasm has only become possible with the advent of diagnostic tools such as the fMRI scanner or EEG, which can see what happens in the brain. Before that, researchers were dependent on what women told them, always an inadequate method (as humans don’t tell the truth about sex). even when – as in one survey by Florida State University in 1991 – the respondents were nurses, chosen for their articulacy about body parts. (Nearly half of the 805 nurses questioned reported multiple orgasms.)

Blood flow to the genitals, an important part of orgasm, can now be tracked. We can watch over 30 areas of the brain light up, including ones that govern emotion and joy, and release oxytocin, a feelgood chemical that enables bonding. We can see the physiological process of orgasm: the tensing of muscles, the acceleration of heart-rate, the blood flowing to the genital area, and then the blessed feeling of release and pleasure. At this point, women and men diverge. For a start, the man is more likely to have had an orgasm than a woman. A recent national study in the US found that 95% of heterosexual men and 89% of gay men said they always climaxed during sex. In heterosexual women, the rate was 65% (but in lesbians 86% ). This is called the “orgasm gap” and it is usually filled by lying: 67% of heterosexual women admitted faking an orgasm in a 2010 study, while 80% of men were convinced their partner never faked it. I look at that gap, and see the clitoris. This mighty, magnificent organ, that has more nerve endings than the penis, exists, as far as we know, only to give pleasure. As possibly the female orgasm does: it has no known reproductive purpose, but there is no clarity. One theory: that the orgasm is a way for the female body to capture more sperm with the contractions of climax. This is called, delightfully,“insucking” or “upsucking.” The role of the female orgasm in reproduction, or even human behaviour, is, wrote one baffled researcher in the journal Socioaffective Neuroscience & Psychology, “a vexed question”.

After climax, or resolution, the man enters a “refractory period,” where he has to recover. This varies from a few minutes in young men to 20 hours in older ones, but however long it is, there will be no response to sexual stimulation. A woman has no such barrier. If she has had an orgasm, and not faked it, she may “plateau”, but within seconds or minutes, or when she feels like it, given the right stimulation – probably (but not only) clitoral – she can feasibly orgasm again. The circumstances required include her environment, her partner (if she needs one), and her knowledge of her own body. It’s surprising, says Professor Linda Cardozo, a spokesperson for the Royal College of Obstetricians and Gynaecologists, “how many women don’t even know what their genitalia are called”. We say vagina (the internal passage leading to the cervix) when it’s the vulva (external genitalia). We see images of women with improbably shaven genitalia, and supposedly female dolls with no external labia. The authors of one study that attempted to understand how women’s genitalia varied in appearance marvelled that “even some recent textbooks of anatomy do not include the clitoris on diagrams of the female pelvis”. When women come to her thinking they are dysfunctional in some way, says Sarah Martin, executive director of the World Association of Sex Coaches, one of the most powerful things she can do is send them away to look at their vulva in a mirror. Using the right words is important too. Vulva, not vagina. Otherwise, says Vincenzo Puppo, a sexologist at the University of Florence, women think of their vagina as “just a hole”.

Martin also tries to get women to relax. Before orgasm, alpha waves in our brains slow down. A recent documentary on the “super-orgasm” – actually multiple orgasms – found that women who had multiple orgasms had slower alpha waves than the average woman. Their brains were quieter, making more room for pleasure. “The thing about sex of all sorts,” says Martin, “is that sex takes place in the body. It’s very hard to think about pleasure if you are worrying instead of focusing on your body.”

What might you be worrying about? Probably whether you’re going to have an orgasm. Only about 20% of women can reach orgasm by penetration alone; the rest of us need clitoral stimulation. The vagina is marvellous, but it is not packed with nerve endings like the clitoris.

You may think differently about the vagina if you believe in the G-spot. Puppo has little patience with it, and labels anatomical illustrations with: “the invented zone for the G-spot”. It is named after Ernest Gräfenberg, who wrote a paper in 1950 about an erogenous zone on the vaginal anterior wall. This was launched into popular perception by an eponymous 1981 book written by two psychologists and a nurse, and by countless articles since. The nurse was Beverley Whipple, who told the Science Vs podcast that her team had investigated by inserting fingers into women’s vaginas and feeling around the clock. “Between 11o’clock and 1 o’clock,” Whipple says, “we got a lot of smiles.”

What a great thought. Except Gräfenberg never wrote about a G-spot. He did write about women he called “frigid,” and reported that some women were stimulated by inserting hat pins. There is still no good scientific data to prove its existence, although plenty of women believe they have one. “The G-spot,” wrote the neuroscientist Terence Hines in 2001, “will remain a sort of gynaecologic UFO, much searched for and discussed, but unverified by objective means.” The debate matters, says Puppo, because “women who fail to ‘find’ their G-spot, because they fail to respond to stimulation as the G-spot myth suggests that they should, may end up feeling inadequate or abnormal”.

Cardozo is circumspect. “There is some doubt as to whether a particular spot in the anterior vaginal wall is relevant in terms of orgasm. When women have had that part of the anterior wall excised, they have still been able to orgasm.”

The G-spot debate hasn’t prevented cosmeto-gynaecologists from offering procedures such a G-spot amplification, a concept first offered by the Californian gynaecologist David Matlock, who decided injecting collagen into the vaginal wall would enhance sensation for four months and the chance of single or multiple vaginal orgasms. The American College of Obstetricians disagreed, deciding that the procedure had no scientific basis, and anyway, Cardozo says, “the herd of cows that provided the collagen died out”. Now the money-maker is the O-shot (O for orgasm), an injection into the vaginal wall of platelet-rich plasma (PRP) derived from the woman’s blood.

“There is no scientific data on this,” says Cardozo, with some finality, although PRP has worked in dental patients, allegedly enhancing the healing process. You probably want tips for how to get a multiple orgasm here. Or even a single one. I prescribe better research, of course. But also, better talking. Communication is as powerful as lube, whether it’s with a partner or a doctor. For women who think they need to surgically alter their vulva because they are abnormal, the American College of Obstetricians prescribes “a frank discussion” about the wide range of normal genitalia.

I also prescribe a feminisation of gynaecology, but that is already happening: in the US, 82% of residents in gynaecology now are female, and half of the UK’s Royal College of Obstetricians and Gynaecologists’s members are women. I prescribe better knowledge: women can orgasm singly and multiply orgasm, but often it has to be learned.

The clitoris should be placed on equal standing with the penis. All these prescriptions can combine for as pleasing an outcome as an orgasm, single or multiple. Because it matters. The female orgasm may have a reproductive role or not: I’ll leave that up to scientists to debate, and celebrate the fact that they are debating it. Perhaps it’s enough to know that an orgasm feels good, and in these dark times you deserve it, or many.