These days, there's probably no such thing as a Shared Nation Experience.
Once upon a time, when television channels were more limited in number but greater in scope and appeal, it was often possible to locate specific events that more than 50% of the population experienced together, simultaneously.
But a proliferation of minority interest channels means that, at any one moment, the majority of viewers are likely to be scattered amongst several dozen - if not hundred - media streams.
In my childhood, there were just the three channels until I was about 7 years old. Then there were four. I now have, at the last count, several hundred, although many are variations on a theme.
But the limited number of channels had its benefits. Turning up at school on a morning and saying did you see was almost universally greeted with an affirmative. On this basis, peer pressure decided what you would like to watch, as you needed to talk about it the next day - television not killing but promoting the art of conversation.
But with limited channels, peer pressure had to be translated to parent power. There were few remote controls - those that existed often being wired to the set - so someone had to get up to change station. That someone was usually the father, sometimes the mother, but in the households of my youth, never the children.
The difference was the period before the news: programmes for children. Whilst there may have been a fight between siblings over ITV or BBC children's programming in that slot (though not in my household - my memories of children's programming are of BBC exclusively on weekdays and ITV, usually, on weekends), the actual choice was minimal.
By 5pm, ITV was already skirting its way into other programming, whilst the BBC was generally showing an imported, poorly dubbed miniseries from ARD or ORF and the like.
But not for two days a week. The space between the end of the cartoon-type programmes and Nationwide (later the ill-fated Sixty Minutes, then the BBC Six O'clock News) during everything but the height of summer was filled by Blue Peter.
If launched now, this programme would feature Ant n' Dec look-alikes, mugging at the camera and making smutty jokes. It would be inclusive' so that no one, no matter what his or her level of educational or intellectual attainment, was ever left out.
But Blue Peter had been launched in the 1950s, at a time when the BBC's only television channel had a clear, self-imposed mission. The BBC Television Service - like all BBC domestic services - was there for the middle classes. This was not a Bad Thing.
In fact, this was seen as an altruistic thing. If you wanted to be entertained, you were entertained on the BBC's terms. That meant that the entertainment was also educational, or at least informative. If you tuned in and the crux of the programme went over your head, that was unimportant.
The theory, still true in my childhood and only killed off in the late 1980s, was that, if you didn't understand something in a programme, you would look it up. Go to a library. Pick up a newspaper (preferably a broadsheet). Ask a more learned friend. Write to the broadcaster. Do something.
Therefore television - especially BBC television - never talked down to anyone. It may have had a limited scope, running shallow on viewers' experience and assuming limited horizons for everyone, but it never assumed that the viewer was too stupid, vacuous or time-conscious to care about something.
Blue Peter took that attitude with the section of the audience most likely beyond any to notice it was being talked down to: children.
Young viewers were shown things beyond their understanding, and those things were explained. But they were never handed down written on stone. Features on unusual events or items were presented with the view that the young viewer was interested. If not, they would hang around for the next item, accidentally learning about something in the meantime.
But Blue Peter, almost accidentally, has taught three generations about life itself. By following the ideal that no person should be patronised to, that all events should be presented as they really are, and that no child would be bored by something they weren't interested in as long as it was well presented, Blue Peter set itself the task of explaining life and death.
That seems overblown. How could a children's programme, no matter how good, explain the two greatest unknowns to the nation's next generation?
The answer was simple. Because the presenters were the friends of the viewers. They were older, but they didn't patronise or dumb down. They assumed that the young citizen viewing was an equal. And that made them virtually unique for any child.
The programme also had pets - dogs and cats and even, when such things were thinkable, a tortoise. Kids, whether they had pets or not, identified with the likes of Petra, Shep, Goldie, Jack and Jill.
And thus three generations learnt of death.
We saw the heartbreak in the eyes of Peter Purvis when Petra passed. We saw the unusually subdued opening titles, with an empty beanbag where once Jill had slept.
And more than that. We were told, frankly and without padding, that the end had come through the animal being put to sleep, mercifully sparing it from the pain that only humans - in this country, at least - are expected to leave the planet with.
The heartbreak of the presenters was our heartbreak. The pain they felt was our pain. The retrospective clips were our memories. And another generation learnt that all things end. Pets - and people - die. It is natural. It's painful and unpleasant and it's hardly ever right. But it is how things are.
From memory, the only human to pass in this way was Percy Thrower, the BP gardener. And the pain and grieving was the same. We would never see him again. But that was how it was. You hurt, and you moved on.
At the opposite end of life, we also watched Tina Heath get larger and larger each week. As the child inside of her grew, we learnt about the new science of ultrasound, seeing the baby in the womb live on television.
For those without brothers and sisters, or for the youngest of a family, it was a revelation, an explanation of how the human race relentlessly continues onward. For those with younger siblings, it was a reminder of how we watched our soon-to-be sibling grown from week to week, and of the day that mum disappeared for a day or so and reappeared with a new family member.
(A few years ago, a retrospective on Blue Peter mentioned that Tina Heath's baby was now 18 years old. Somehow this brought me closer to my own mortality, for I am far older than the baby I remember being gestated and that is a shock. The benefit of having a sister who is 4 years younger than me is wiped by having a TV sister who isn't.)
The middle part of life - the age of adventure between the two dramatic events above - was also chronicled.
For one reason or another, it is unlikely that I will ever visit the People's Republic of China, nor the game reserves of Africa or much of the former Eastern Bloc.
But I have visited them. Blue Peter took me there, showed me around, explained how wonderfully different things were and showed clearly how obviously the same all humans are.
I learnt from Blue Peter that, whilst I have nothing at all in common with the average Japanese salaryman, the Masai warrior, the Australian sheep-shearer, I have everything in common with them all. The same hopes, the same dreams, a shared humanity that transcends everything else that may set us apart.
And I know that because of Blue Peter.
If television has any power, any artistry or pretensions to grandeur, it need look no further than that offered by Blue Peter.
This article has been edited to correct Tina Heath's name.