Tag Archives: Astronomy

The Speed of Light: The Universe’s Ultimate Limit

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Due to another recent sleepless night thanks to my mind working in overdrive, I found myself contemplating the speed of light, and the more I contemplated it, the more it wouldn’t let me go back to sleep, and the stranger it seemed.

It’s one of those things you hear about your whole life. School, documentaries, random science articles, the closing song to Monty Python’s The Meaning of Life, so much so you sort of take it for granted. Light goes very fast. End of story, right?

Er, no. The more I started thinking about it, the more I realised it’s not just about how fast light travels.

It’s something much deeper than that.

So, what actually is the speed of light?

At its most basic level, it’s just a number, but not just any number. It is a number that quietly governs everything in the universe, how fast signals travel, how time flows, how gravity behaves, and even how reality itself is stitched together.

That number is the speed of light, usually written as c.

It’s not just the speed at which sunlight reaches your face or lasers shoot across a room. It goes far deeper than that. It is, in many ways, the fundamental rhythm of reality.

The speed of light in a vacuum is: c = 299,792,458 metres per second.

That’s about 300,000 kilometres per second, or if you prefer it in imperial, 186,000 miles per second, fast enough to go around the Earth more than seven times in a single second.

But here’s the interesting part: this number isn’t just measured, it’s defined. Since 1983, the metre itself has been based on how far light travels in a fraction of a second.

So, in a strange way, we’re not just measuring light, we’re using it to define reality.

Another thing that’s easy to miss is that c isn’t really about light on its own. It’s the speed of all electromagnetic radiation, from radio waves to gamma rays, and even appears in the laws governing phenomena like gravitational waves.

Nothing in the universe can go faster than light. Not matter, not energy, and not information. That’s what gives the universe its speed limit. Why? I hear you ask. And the answer, my friends, is because anything with mass accelerating toward c will require more and more energy. To actually reach it would require infinite energy, which is impossible.

The speed of light is therefore not just fast, it is absolute.

This is where Einstein comes in. Back in 1905 he made a radical leap. He proposed that the speed of light is the same for all observers, no matter how fast they themselves are moving.

That seemingly simple idea shattered classical physics to smithereens (I might be being a bit over dramatic there) and led to the theory of special relativity, and with it came strange and beautiful consequences: time slows down for objects moving near light speed, and length shrinks in the direction of motion. Mass and energy turned out to be two sides of the same coin too, which gives us the most famous equation of all:

In that one brilliant moment, the speed of light became more than just a velocity. It became a statement about how we see the universe itself: because light travels at a fixed speed, we never see the universe as it is, only as it was.

So, if you look at the Sun you are seeing it from 8 minutes in the past, the moon is from 1.3 seconds ago, any nearby stars you gaze at are years ago, and if you were to look at distant galaxies, they are from millions or billions of years ago. Amazing, isn’t it? Every time you look into the night sky, you are literally looking into history.

Let’s take a closer look at light, fields, and the deep structure of physics.

In the 19th century, James Clerk Maxwell showed us that light is actually an electromagnetic wave, and its speed comes from the properties of empty space itself, which in itself is a bit mind bending!

Then, in modern quantum physics, we go a step further. Reality, as far as we can tell, is made of fields. Particles are just ripples in those fields, and the speed of light is the maximum speed those ripples can travel. In this view, c is not just about light, it is the speed of all cause-and-effect in the universe.

And this ties into black holes as well (as I was rambling about in my last post). If you make gravity strong enough, you eventually reach a point where the escape velocity equals the speed of light and that’s the event horizon. Beyond that, nothing gets out, not because something is pulling it back in like a cosmic vacuum cleaner, but because spacetime itself is warped in such a way that every possible path leads inward.

What’s that? Another question I hear? Can we go faster than light? No, we can’t, not with the laws of physics as we understand them now. Modern physics is very strict on this; nothing can move through space faster than light.

But the universe does have a trick up its sleeve. Space itself can expand faster than light. Distant galaxies are being carried away faster than light so that some are forever beyond our reach. Crucially, this doesn’t break relativity, because nothing is actually moving through space faster than light, space itself is stretching.

Which leads us to another question: if we could travel faster than light, why would doing so break reality?

And the answer to that question is this: if faster-than-light communication were possible, something extraordinary, and dangerous, would happen. Cause and effect could reverse, which in some reference frames means a message would arrive before it was sent, creating a paradox where an effect precedes its cause.

And this is why physicists think of c not as the speed of light, but as the speed of causality.

Still with me? Good, I’m going to get a bit more technical here and bung in an equation, I try to avoid equations as much as possible as they can be baffling to understand (apart from the one above, obviously), it’s only as I have got older and more learned (hark at me!!) that I am better able to get my head around them.

Anyway, the speed of light also appears in one of physics’ most mysterious numbers, The fine-structure constant:

It basically shows us how strongly electromagnetism works, and it depends on the speed of light, along with quantum mechanics and electric charge and other quantumy stuff. Anyway, together these constants define how atoms hold together, how chemistry works, and ultimately how anything exists at all, but that is for another blog post, so you’ll just have to take my word for it for now.

All this brings us to the one final mystery which nobody really has an answer to. Why this number? Why does the speed of light have this exact value? We know how to measure it. We can use it. We know it shapes spacetime itself. But why that value?

At the deepest level, where quantum mechanics meets gravity, we still don’t know. Remember, I’m just an amateur here and I definitely have no idea. However, some theories suggest spacetime may emerge from something deeper, and that c might emerge with it.

Putting all this into perspective (and adding some cool bullet points), the speed of light is:

  • The maximum speed of information
  • The structure of spacetime
  • The limit of cause and effect
  • A link between energy, mass, space, and time

It is not just a property of light. It is a property of reality itself. How’s that for a statement?

But wait, it gets even better as perhaps the strangest thing of all is that every single moment, everything in the universe is obeying that limit.

Whether we notice it or not, the future is only ever unfolding as fast as light allows.

A thought experiment about how advanced civilisations might preserve knowledge. Not through communication, but through persistence

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I’ve been thinking about the Fermi Paradox again recently, that slightly uncomfortable question about why, if intelligent life is likely in the universe, we don’t seem to have any real evidence of it.

For decades, the search has mostly focused on listening. Radio signals, communication, signs that something out there is trying to make itself known. So far, despite years of searching we have nothing definitive.

This got me wondering whether we’ve been looking for the wrong thing entirely. If you look at what we’re doing as a civilisation, there’s been a noticeable shift.

We’re getting very good at storing information by placing huge amounts of data in tiny physical space. We have materials designed to last for extremely long periods (fused silica, for example), and more recently, even starting to think about storing data off-world

There are already data payloads on the Moon, essentially early attempts at creating long-term archives beyond Earth. In a similar spirit, earlier missions like Pioneer 10 and 11 even carried engraved plaques, simple, durable messages intended to outlast the spacecraft themselves and potentially be understood by any intelligence that might encounter them.

Because we are sending these data stores to the moon, it feels like a subtle but important step, it suggests something quite different about where technology might be heading. Not outward and loud, but inward and durable.

So, I had this idea, and my thought is this:

What if advanced civilisations don’t broadcast signals, those huge technosignatures and radio communications that SETI have been searching for? What if they leave records instead?

Rather than trying to communicate across vast distances, they might create something that simply persists as a kind of long-term archive. If that’s the case, those archives would probably be small and compact. passive (no need for active power), and extremely durable, designed to last for very long periods, and possibly deliberately placed somewhere stable and discoverable.

If you were looking for a place to store something long-term in our solar system, Mars orbit actually starts to make a lot of sense.  It’s relatively quiet compared to Earth orbit as there is less atmospheric drag, fewer large perturbations, and a simpler gravitational environment overall. There’s also the added point that Mars itself likely had a very different past, thicker atmosphere, liquid water, maybe even early-life conditions. So, it’s not just stable, it’s interesting from a biological perspective.

From an engineering standpoint, there are a couple of obvious candidates. Higher Mars orbit (away from atmospheric effects and lower orbital decay), gravitationally stable regions like the Lagrange points (L4 and L5), where objects can remain relatively stable over long periods.

What would we actually see though? If something like this existed, I doubt it would look like a spacecraft in the way we tend to imagine it. It would probably be small. Passive. Unremarkable at first glance. Maybe the sort of things we’d need to look for are:

  • Small objects in unusual but stable orbits
  • Occasional bright reflections, glints, where light catches on a surface
  • Slightly odd thermal behaviour
  • Shapes or edges that don’t quite look natural

In other words, subtle anomalies. Nothing dramatic. Nothing obvious. Just things that don’t quite fit. None of this is especially speculative, it’s just basic orbital mechanics.

One of the most interesting parts of this idea is the possibility that we might already have the data.

We’ve been observing Mars for decades now, with high-resolution imagery, radar data. And thermal measurements, But, all of that work has been focused on the surface, not on systematically looking for small, anomalous objects in orbit. Which means there’s a gap. We might already have the data; we’ve just never really asked this particular question of it.

Is all this actually testable? The answer is yes, and that’s what makes this idea interesting to me.

It’s not just a thought experiment,. It’s something that could be tested, even at a basic level by taking existing Mars datasets and running anomaly detection on them. We can search for anything that looks odd or behaves in an unexpected way while filtering out the obvious stuff such as known spacecraft, debris, noise, etc.

Even if nothing turns up, we’d still learn something about what’s there, and what isn’t.

Why does this matter? I hear you ask. Well, If something like this did exist, even just one confirmed example, it would completely change the situation, because it wouldn’t rely on communication, It wouldn’t rely on timing or distance or whether anyone is still “out there”. It would just be… evidence. At that point, the Fermi Paradox wouldn’t really be about silence anymore, it would be more like: Have we simply not recognised what we’re looking at?

As a final thought, I’m not claiming that there are definitely extraterrestrial archives sitting out there in Mars orbit, but it does feel like one of those ideas that sits right on the edge between speculative and testable. And more importantly:

It’s something we haven’t really looked for.

Given how much data we already have, and how our own technology is evolving — it feels like a question that’s at least worth asking properly, because if those kinds of records did exist, we might not even realise we’re looking at them.

Hypothesis (for clarity)

Advanced extraterrestrial civilisations may prioritise long-term information preservation over visible energetic expansion, and may therefore deploy compact, durable archival systems in stable orbital environments, such as Mars orbit or associated gravitationally stable regions, where such artefacts could plausibly persist over extended timescales and be discoverable through systematic analysis of orbital data.

This is a simplified statement of the idea discussed above.

Full Paper

If you’d like to explore the idea in more detail, including the full framework, methodology, and supporting reasoning:

👉 Download my full paper (PDF):
https://malandally.co.uk/wp-content/uploads/2026/07/andrews_2026_06_12.pdf