Endlessly fascinating and always controversial, there are a million and one ways to talk about sex. But we reckon even a seasoned sex pert would still be surprised by some of these random facts. Here Yeong Sassall lists the strange and downright crazy things we bet you didn't know about doing the deed. Prepare to be enlightened…

1. Male sperm can live up to 5 days

Male sperm is surprisingly resilient. Sperm inside a woman’s vagina can live in her cervical mucus or upper genital tract for 3-5 days. Provided the sperm remains alive, it may even be able to fertilise the egg, too. Sperm ejaculated outside the body is less tough – it can survive up to a few hours.

2. Sometimes sex is a matter of life and death

If a female ferret doesn’t mate while she’s in heat, she can die! If she’s unable to find a sex partner and stays in heat too long, her body will start to secrete high levels of estrogen, which causes aplastic anemia – a deadly disease for ferrets.

3. A man produces a mind-boggling amount of sperm

There’s plenty of male sperm to go around. And we mean plenty: One single guy produces enough sperm in two weeks to impregnate every fertile woman on the planet. (Wonder if Ryan Gosling knows this?)

4. Sex can increase your pain threshold

Apparently the Divinyls were right – there is a fine line between pleasure and pain – at least during sex, that is. According to a study published in the Journal of Sex Research, when you’re aroused your pain threshold can increase significantly. It’s even better if you reach the big O – orgasms have been known to block pain by releasing a hormone which elevates your pain threshold. 

5. Semen can be used as um, invisible ink

During World War I, members of the British Secret Intelligence Service (MI6) discovered you could use semen as invisible ink. Apparently, it didn’t react with iodine vapour (the main method used to detect invisible ink) and, as a bonus, it was also readily available. They stopped using it once they realised that it began to smell if it wasn’t, uh, fresh. Disturbing, but true!

6. We spend copious amounts of money on sex on the internet

Sex is big, big business. According to a 2005 study published in Sexual Addiction & Compulsivity, more than half of all spending on the internet is estimated to be related to sex. That’s a lot of porn and sex toys. 

7. Sperm contains calories!

While spitting or swallowing semen is always a matter of personal preference, if you’re on a diet you may want to reconsider swallowing. Why? There are five calories in a teaspoon of semen. 

8. There's a reason why it's hard to wee after sex

After you orgasm, your body releases an anti-diuretic hormone, which explains why you may have trouble urinating directly after sex. Stick with it though – going to the loo after sex helps to prevent urinary tract infections.

10. You can increase your bust size by having sex

Ladies, forget push-up bras – just get frisky instead. A woman’s breasts can swell up 25 per cent when she’s aroused. And about one per cent of women are able to orgasm through the stimulation of their breasts and nipples alone.