Article on Clowes.blog

How Apollo 11 communicated with Earth

Mon, 20 Apr 2026 20:16:22 +0100

I’ve never been especially interested in space or NASA. I find space so intimidating to learn about. And it hurts my brain if I think about it too much – the vastness of it all. It’s a real blind spot in my knowledge. And I must fix that. But watching the film “Apollo 13” has stirred my imagination. I haven’t got to the end of the film yet, but I’m really enjoying it. I like films about people “working the problem”. And one question I’ve always had about Apollo 11’s mission to the moon is: how did NASA get all this near-realtime data in the 1960’s‽ Voice, telemetry, etc. Well, I found out.

The Minor Delay

They got all this data via something very simple: radio.

The Moon is ~384,000 km away. Radio signals travel at the speed of light, giving a one-way delay of ~1.3 seconds (~2.5 seconds round trip). This is why there’s a noticeable pause in all Apollo mission audio.

The Ground Station Network

NASA used a global chain of stations ensuring one was always facing the Moon as Earth rotated (radio needs line of sight). Key stations: California and two in Australia.

The spacecraft used a steerable high-gain dish antenna to beam a focused signal back to Earth.

What Was Transmitted

A single radio link carried multiple streams simultaneously (multiplexed):

Voice communications
Biomedical telemetry (heart rate, respiration per astronaut)
Systems telemetry (hundreds of parameters: pressure, temperatures, voltages, thruster status)
TV video (slow-scan format, converted before broadcast)
Ranging data (signal travel time used to calculate precise distance)

How Physical Measurements Become Radio Signals

The full chain:

Sensor measures something physical (temperature, pressure, voltage)
Sensor outputs a proportional electrical voltage
An ADC (Analogue-to-Digital Converter) samples this voltage and converts it to binary numbers
A multiplexer cycles through hundreds of sensors rapidly, producing a continuous binary data stream
A modulator encodes that binary stream onto a radio carrier wave by varying one of its properties (Apollo used phase modulation — a phase shift one way = 0, the other way = 1)
The wave travels to Earth, where a ground antenna demodulates it, stripping the data back off the carrier
You’re back to a binary stream — just data

How the Ground Knew Which Reading Belonged to Which Sensor

As I was learning all of the above, my digitally minded brain was confused how it could be done without something like JSON. But no metadata or labels were used. Instead: time-division multiplexing with a fixed frame structure. Before launch, both the spacecraft and ground agreed on a fixed, hardcoded schedule — the multiplexer always cycled through sensors in the same order at the same rate. Position 1 was always sensor X, position 2 always sensor Y, and so on. The ground just counted positions; no labelling needed.

To mark the start of each cycle, a sync word (a distinctive fixed bit pattern) was transmitted at the beginning of each frame. When the ground decoder spotted it, it reset its positional counter.

Readings were organised in two tiers:

Minor frame — one full cycle through all sensors
Major frame — multiple minor frames grouped together; slower-changing sensors (e.g. cabin temperature) only appeared once per major frame to conserve bandwidth

This was extremely efficient — zero bandwidth wasted on metadata — but brittle. If sync was lost, the system had to wait for the next sync word to re-lock.

A beautifully simple combination of analogue and digital. Remarkable.

The existence of AI video creates plausible deniability for everything

Sat, 18 Apr 2026 19:30:32 +0100

Many are worried that the rise of realistic looking AI video tech will lead to fake videos of people doing bad things to smear their name.

But another worrying side effect of AI is how people will cry out “it’s AI” to genuine videos, just because they don’t want to believe it’s real – or want to convince others that it’s not real.

AI creates plausible deniability.

I see this battle over truth every single day in the comments on social media.

This was a few of the comments on a video about abuse in Romanian orphanages:

What files from your Mac do you actually need on your phone?

Sun, 13 Oct 2024 20:48:25 +0100

I recently dropped Dropbox to save myself £10/mo. I’ve replaced it with iCloud Drive, which I pay for already.

Mostly I used it so I can access my files on my iPhone too. But I’ve realised there’s only a few folders I need:

Documents. For tickets, ID, or personal info.
Screenshots. I occasionally screenshot info or as a reminder. So I need access on the go.
Blog drafts. I like to write or refine posts on the train.

The other folders I have are temp ones for getting files from my phone to my Mac. For example audio notes, scanned documents, or TikTok videos I’ve downloaded. Hazel on the Mac then auto-moves them to their final destination on the file system.

Digital legacy

Fri, 27 Sep 2024 00:58:12 +0100

I’m 32. So hopefully death is still many decades away. But I still really need to document how I want my family to handle my digital legacy. Especially my websites. I don’t care if my personal files on my Mac disappear. But I’d like my websites to remain online for as long as possible after I die.

Right now I have three sites powered by Hugo and hosted on AWS. They should remain up for a decade or two as long as the $5/mo bill is paid. My biggest concern would be AWS introducing a new login or payment system that requires manually migrating to. A non-techy family member might struggle with that.

I also have my Micro.blog blog. As of today it doesn’t hate enough posts for me to be upset at the prospect of it disappearing. But if I did want to preserve it my main concern would be that Micro.blog could very easily be shut down. Luckily it’s all static pages and is Hugo again behind the scenes, so it shouldn’t be too tricky for a somewhat tech savvy friend/family member to get a copy of it all onto AWS.

My main concern are my Obsidian notes that get turnt into Learnt.me. In many ways that site is the most in-depth digital representation of who I am, so I’d like it to survive after I died. It’s turned into a website via Obsidian’s ‘Publish’ feature. But the site seems very JavaScript-y and not the easiest to have backups of. Luckily all the notes that the site are based on are just Markdown notes. And there’s also at least one other service that offers something like Obsidian Publish. But either way, worse case scenario all my notes could just be uploaded to an Apache web server and be browsed and viewed via the folder hierarchy. However I really like how Learnt.me looks and works. It would be a shame to lose that.

I’m not sure what the best solution is long term. I thought about having all the content hosted on NearlyFreeSpeech. It’s pay as you go, so I could deposit a bunch of money into it. But to be honest, as long as I can find a way for the AWS bill to be paid, that would be the easiest and most reliable route for long term hosting.

But either way, my digital ‘estate’ is in a much more stable long term state than it has been in the past. Sure, I have too many sites, which makes things more tricky. But at least none are powered by WordPress, which would make things very brittle and tough to keep up and running.

🍿 Film Review: Air (2023)

Thu, 18 Jul 2024 09:26:00 +0100

“Air” is about the creation of Air Jordan shoes at Nike. It’s silly and corny, but very enjoyable.

Moving along at a quick, fun pace and feels a bit like an Adam McKay film at times.

This is also quite the ‘Dad film’ (another one for Matt Damon, after Ford v Ferrari).

You might have missed “Air”. But you should correct that, as it’s a great way to spend 111 minutes and very much worth a watch. It’s hard to dislike it.

Also: are you ever unsatisfied by the “where are they now” segment at the end of “based on a true story” film, when they don’t go into enough detail? Well this delivers in this department.

After “Air” you should watch:

The Last Dance, a documentary about Michael Jordan.
BlackBerry, another ‘business film’. It’s another solid film you might have missed..

71%

Find out where to stream it.
This review is also on Letterboxd.

A hip church, a modern poet

Thu, 04 Jul 2024 12:43:02 +0100

I recently saw the poet Harry Baker. My girlfriend was the fan and wanted to go, though I had also enjoyed what little I had seen of him.

It was at Saint Saviours Church Hall, St Albans, which is the hippest church I’ve been to. There was kegs of beer, fairy lights and some sofas to the side of the nave. And the vicar had a shaved head, tattoos and wore cargo shorts.

I was a huge poetry nerd in my tormented teen years (14-17). But these days I don’t have much interest – and certainly not in modern poetry. So I wasn’t massively looking forward to a night of non-stop poems.

But the show was great. His poetry is perfect for the modern era. Funny, witty and with a great musicality. The way his voice delivers lines is wonderful. There’s an earnestness to the way he speaks that is enrapturing.

And he didn’t overstay his welcome. I was worried it would be 2 hours+ of non-stop poetry. But it was just the right length, with a break in between where you could buy a book and meet him.

When my girlfriend met him she decided to go down the more casual route. Rather than a “huge fan of your work, you’re my hero”, she went with a simple “hello, how are you?”. He didn’t appear to be expecting such an unassuming greeting and it led to 45 seconds of incredibly uncomfortable awkwardness. The stilted back-and-forth continued painfully as she hurriedly chose a book and he hurriedly got out the card reader. I couldn’t help but laugh.

Blogging like Dave Winer: the case for making more of your thoughts public

Wed, 03 Jul 2024 03:16:19 +0100

Dave Winer has been blogging since 1994. And extensively too. His output is remarkable. And the result of that is nearly everything that he references and talks about from the past has a blog post he can link to. You can see his thinking in real time and get a great deal of context.

And it makes me want to both blog more freely and frequently and also live life more publicly online. And I think that there’s good arguments to be made for writing publicly on a weblog, rather than in offline software.

I’ve used the journaling app Day One for years. It’s been around for a while and now that it’s owned by Automattic I expect it will continue to be around for many years.

But generally speaking, software is more brittle than the web. It often uses proprietary formats and is prone to abandonment. Whereas the web is more open, easier to back up and won’t go away any time soon. In 50 years time I’d be shocked if a HTML/CSS webpage can’t still be shown the average computer still. I doubt Day One will still be around.

And in my 20 years of writing and journaling I’ve used many different software. The end result of that is my writing is all over the place, in different formats and different apps.

So what if that whole time I just used something like WordPress instead? Today my thoughts would all be in one place, nicely tagged¹, easily searchable and with a URL that I could link to.

Then there’s the tricky subject of death. If I die today no one is accessing my journal. A journal that might be interesting to my family. But if my thoughts were on a blog they could see them easily.

Of course there’s privacy concerns with the web. WordPress does let you make posts private or hidden behind a password. But data breaches can happen and things can leak. So that is a downside.

But my whole point is that I want more of my thoughts and life to be public. If I’m honest I’m not one of those people who pours my heart out in my journal anyway.² So 90% of what I write I’d happily make public and that’s my aim.

With clowes.blog I’m attempting to live a bit more publicly. But it still doesn’t come close to what Dave Winer’s scripting.com does. For me to get there I need to share and write more frequently.

So I’m going to try it. I think future me will be glad I did.

I did my best to transfer my data from one service to another down the years. But one of the things that was always hardest to keep in the transfer were things like tags. If I used WordPress I would have had the same tag system from the start. ↩︎
It’s actually one of the things I like least about my journaling style. I am always thinking of an audience when I journal. I know that no one other than me is going to read it, but yet I still can’t open up and share exactly what I’m feeling. ↩︎

June 19th, 2024

Wed, 19 Jun 2024 08:53:36 +0100

Good morning all. It’s currently 14°C in London 🌤️

🚆 Trains reads:

🧍‍♂️Me update:

4hr 9m of sleep 🛌
I could really do with my next pay cheque to arrive, I must say.
I’ve really cut down my caffeine intake these days. But I might try none for a while to see if it helps with my occasional insomnia.
Had a sore stomach last night that has continued into the morning.
I have sadly pulled off the mythical upset-your-girlfriend-before-9am 😬

A place to write where you just don't care

Tue, 18 Jun 2024 16:39:55 +0100

🔗 Stream on

Simon Collison has written about having a longer form blog and also a short one.

A primary motivation for creating my Stream was the paralysing sense that a blog post needed appropriate length and weight.

I understand that feeling well. I am always too aware of my audience when I write. To the point that anything too short or off topic feels like I’m wasting their time. As a result I have created way too many blogs down the years (and I still maintain too many).

So I’ve found my recent discovery of Micro.blog very freeing. I don’t care too much on here. I just share what’s on my mind. No matter how short, long or off topic.

1988 Flannel

Tue, 18 Jun 2024 15:55:30 +0100

Daughter Realizes Dad Has Worn Same L.L.Bean Flannel Shirt Since 1988

I’m a recent convert to flannel. Like pickup trucks they do just look a bit silly in the UK. But the benefits outweigh that for me.

They’re so versatile. Lovely and warm in the autumn, often letting you go out without a jacket. And you can wear a t-shirt underneath and then unbutton the shirt if you get too hot. And in the winter they’re often thick enough that when paired with a jacket you are nice and toasty.

Flannel is also hardy and long lasting (though not as hardy as they once were I’m sure). I drunkenly fell off my bicycle last year wearing an Abercrombie & Fitch one. It has a few scuffs, but it survived very well indeed. And if I wasn’t wearing it my skin would have been covered in road rash.

Another reason I like this story is because it reminds me of the ‘capsule wardrobe’. The idea that you have a default outfit – or a few default outfits. Meaning you don’t spend a bunch of time working out what to wear each day.

I have too many clothes to have a ‘capsule’. But I would say I have a ‘uniform’ at work. I wear the same Cos fleece, Charles Twyitt trousers and Clark’s dessert boots each day.

Digital legacy

Mon, 17 Jun 2024 14:58:36 +0100

At least once a week I think about what’s going to happen to my websites once I die. Within a month or two they’ll probably disappear, which upsets me.

What can I do to avoid that? It shouldn’t be too difficult. All my sites are static, aside from Learnt.me which is put online via Obsidian Publish. But Learnt.me is probably the site I’d like to remain online the most after I die.

WordPress now offers their 100-Year Plan. But it’s $38,000.

NearlyFreeSpeech is pay-as-you-go. So I could conceivably top up my account with as much as I could afford and it should last a while (assuming they stay in business).

My current sites are largely on Amazon S3. So as long as there’s an active card to pay the $3-4 monthly pay it should keep working for many years.

But ideally my Will gives some instructions and some money for preserving my digital legacy. And one of my more tech-y friends could carry it out.

I don’t plan on dying any time soon. But it would be good to put a plan in place.