Somebody I didn’t know died last week.

I’d never met her in real life – or, I think I never met her, but I suppose I could have. We shared some of the same friends and acquaintances, some of whom I knew in person and some of whom I didn’t. The two worlds we both inhabited – virtual and real – blended so seamlessly that I didn’t really notice until she’d departed the latter that I was only really acquainted with her in the former.

How do you mourn someone you only knew as an idea?

I will experience more death than my parents, because I know more people than my parents. People I haven’t given any thought to in years, people who – for all generations before mine – would have simply slipped out of mind, can remain on my social radar simply because there they are, archived. Here, look: a wedding album. There: a birthday reminder. And inevitably, at some point: a death.

In the 1990s, British anthropologist and primatologist Robin Dunbar calculated that, using a correlation between the neocortex of a primate’s brain and its group size, the number of people with whom a human being can have a stable interpersonal relationships is roughly 150.

Since the invention of Facebook and Twitter, the brain size factors that limit the size of our potential network size are easily circumvented. I can converse on friendly tones with any one of a vast potential pool of people, all of whom have their identity neatly racked, categorised and explained. Rituals that cement relationships face-to-face – music, dancing, eating, drinking, laughter – have equivalents, or near-equivalents, online.

Our potential social group size is no longer limited by those who we can keep physically close to us; it’s limited only by the time we have for interactions when the cues to interact are digitally provided to us. We can all but seamlessly return back to friendship with someone of whom, in any other age, we would have lost track and met again as strangers.

At 150, according to Dunbar’s original research – and borne out by subsequent studies – human groups begin to struggle to maintain cohesion. Each individual, according to the theory, has to understand every member of the group’s relationship with every other member.

But in an age where the internet acts as a force-multiplier for sociability (if only for those who are native to it), it is now possible to develop friendships with people we’ve never met at all. Twitter is more than just a conversation; it is a schoolyard, a lunchroom, a water cooler. “Internet friends” are still friends – at least as much as “friends” on Facebook who we haven’t seen in years.

I found out that my friend had died late at night, and reflexively direct-messaged her boyfriend on Twitter. The next morning, I wasn’t sure if I’d made a mistake: I was a stranger to them, really. Did mutual following one another on Twitter – the fact that I read their streams of consciousness, and they mine – mean anything to them? What did it mean to me? Was it acceptable or unwelcome that, in his time of grief, I’d inserted myself like there was anything comparable in our experiences of her life?

Twitter gives us a window into other people’s lives, makes us feel like we’re a part of their everyday struggles, their complaints, their jokes, and their celebrations. The problem with that illusion – and it is an illusion – is that I felt a part of her death, too. It’s a peculiar feeling, experiencing someone else’s tragedy by proxy, mediated through the internet.

Somebody I didn’t know died last week, and there was no way to deal with it – no set of mores or traditions, no roadmap to closure, or even a sense of what closure it is even valid to need.

Those traditions, too, will develop organically, over time. But for now, all we are doing is feeling our way through.