The Cosmic Zoom

This page is a plain-language summary of what is currently known about the universe, organised by scale to match the animation above. Jump straight to any chapter of the zoom: Earth · the Moon · the Sun · the outer planets · the heliopause · the nearest star · the Milky Way · the Local Group · Laniakea · the cosmic web · the observable universe · and beyond.

How small are we, exactly?

If the entire Earth were shrunk down to the size of a single grain of sand on Auckland’s Mission Bay beach, then on the same scale the Moon would be a smaller grain of sand sitting about 30 centimetres away. The Sun would be a marble 100 metres up the beach. Pluto would be a speck of dust 4 kilometres further on. The nearest other star would be another marble in Brisbane. The Milky Way as a whole would be a swarm of marbles spread across the entire surface of the Earth. The nearest other galaxy like ours would be a similar swarm somewhere in the asteroid belt. The observable universe would be a sphere of swarms-of-marbles reaching out roughly to the orbit of Pluto.

That’s the visualisation problem the animation above is trying to solve. The numbers individually feel manageable. The relationships between them do not. The journey from “this beach” to “this galaxy” passes through about ten orders of magnitude; the journey from “this galaxy” to “all the galaxies we can see” passes through another ten. The mind doesn’t have a native handle for those gear ratios. The animation gives you something close to a felt sense of them — the acceleration required to keep pulling out is itself the message.

Earth and low orbit

The journey starts at the only place in the universe confirmed to host life. Earth is 12,742 kilometres across, 4.54 billion years old, and — as far as roughly seventy years of space science, radio astronomy and planetary exploration have been able to establish — unique. Everything else on this page is inference from light. This is the one place we have actually stood.

The first chapter of the animation, low Earth orbit, covers the thin shell where almost all human spaceflight has happened. Space legally begins at the Kármán line, 100 kilometres up. The International Space Station orbits at about 400 kilometres, circling the planet every 90 minutes, and has been continuously crewed since November 2000 — meaning there are now adults who have never known a moment when every human was on the planet at once. Alongside it orbit many thousands of active satellites, from communications constellations to the weather and positioning systems that New Zealand’s forecasts, aviation and EFTPOS terminals quietly depend on. For scale, honesty demands this admission up front: if Earth were the size of a classroom globe, the ISS would orbit about a centimetre above its surface. Everything humans have done in space, apart from nine crewed voyages to the Moon, has happened inside that centimetre.

The Moon

The Moon is 3,474 kilometres wide and orbits at an average distance of 384,400 kilometres — about 1.3 light-seconds, or thirty Earths laid side by side. It formed, on the leading account, from debris blasted into orbit when a Mars-sized body struck the young Earth about 4.5 billion years ago. It is drifting away from us at 3.8 centimetres a year, a figure known precisely because Apollo astronauts left mirrors on the surface that observatories still bounce lasers off today.

Twenty-four humans have travelled to the Moon and twelve walked on it, all between 1969 and 1972. It remains the only other world where people have stood. Its gravity is also the main reason New Zealand’s coastlines breathe in and out twice a day — the physics of that is genuinely stranger than most people think, and we’ve built an animated explainer at How Tides Actually Work, with live tide times for 28 New Zealand ports at NZ Tide Pulse.

The Sun

The Sun is a middle-aged yellow dwarf star, 1.39 million kilometres across — 109 Earths side by side — containing 99.86 percent of all the mass in the solar system. Every planet, moon, asteroid and comet combined amounts to a rounding error on the Sun. In its core, at around 15 million degrees, it fuses roughly 600 million tonnes of hydrogen into helium every second, and has been doing so for 4.6 billion years. It is about halfway through its life; in around five billion years it will swell into a red giant and then settle down as a white dwarf.

Sunlight takes 8 minutes and 19 seconds to reach Earth, which means you never see the Sun as it is — only as it was. The Sun also streams charged particles outward as the solar wind, and when an especially violent burst of that wind reaches Earth, the result over southern New Zealand is the aurora australis. Our live aurora forecast tracks exactly that, using the same NOAA space-weather feeds professional forecasters use. The Sun’s activity rises and falls on a roughly 11-year cycle, and its behaviour over the next day is genuinely hard to predict — one of many reminders that even our own star keeps secrets.

The planets and the edge of the solar system

Eight planets orbit the Sun: four rocky worlds close in, then four giants. Jupiter is eleven Earths wide and could swallow 1,300 of them; Saturn’s density is so low it would float in a sufficiently large bathtub; Uranus and Neptune are “ice giants” of slush and gas that no spacecraft has visited since Voyager 2’s flybys in the 1980s. Pluto, reclassified as a dwarf planet by the International Astronomical Union in 2006, turned out — when New Horizons flew past in 2015 — to be a startlingly active little world with nitrogen glaciers and a haze-blue sky, one of thousands of icy bodies in the Kuiper Belt.

Further out lies the heliopause, where the solar wind finally gives way to the thin gas between the stars. Voyager 1 crossed it in 2012, thirty-five years after launch, and is now about 25 billion kilometres from home — far enough that its radio signals, travelling at light speed, take almost a full day to arrive. Both Voyagers, launched in 1977 with computers less powerful than a modern car key, are still transmitting. Beyond them, the solar system does not so much end as fade: the Oort Cloud, a hypothesised spherical halo of trillions of frozen comet nuclei, is thought to extend almost a light year out. It has never been directly observed — we infer it from the long-period comets that occasionally fall in from all directions — which makes it a good early lesson in how astronomy works. Much of what we “know” is careful inference, clearly labelled.

The nearest stars

Cross four and a quarter light years of nothing and you reach Proxima Centauri, a dim red dwarf invisible to the naked eye, gravitationally bound to the bright pair Alpha Centauri A and B. In 2016 astronomers confirmed Proxima hosts at least one roughly Earth-sized planet in its temperate zone — the nearest known exoplanet. Even at the record speed of the Parker Solar Probe, the fastest object humans have ever built, the trip would take more than six thousand years.

The wider stellar neighbourhood holds hundreds of stars within fifty light years — Sirius at 8.6 light years, Vega at 25 — and one cluster every New Zealander now gets a public holiday for: Matariki, the Pleiades, about 440 light years away. Since 1995, when the first planet around another Sun-like star was found (a discovery that earned the 2019 Nobel Prize in Physics), astronomers have confirmed more than 5,500 exoplanets, and the statistics from NASA’s Kepler mission point to a remarkable conclusion — planets outnumber stars in our galaxy. Worlds are not the exception; they are the rule. If you want to see any of this yourself, our stargazing forecast scores tonight’s sky, cloud and moonlight for every region of New Zealand.

How stars are born and die

Every star visible from your backyard follows the same basic biography. A cloud of gas, mostly hydrogen, collapses under its own gravity until the core grows hot enough to ignite fusion. What happens next depends almost entirely on mass. Small red dwarfs like Proxima Centauri sip their fuel so slowly they will burn for trillions of years — every red dwarf ever formed is still shining, because the universe is not yet old enough for a single one to have died. Mid-weight stars like the Sun burn for around ten billion years, swell into red giants, puff off their outer layers, and retire as white dwarfs the size of Earth but half the mass of the Sun — a teaspoon of one would weigh tonnes.

The heavyweights live fast and die spectacularly. A star more than eight times the Sun’s mass runs through its fuel in mere millions of years, then collapses and rebounds in a supernova that can briefly outshine its entire galaxy, leaving behind a city-sized neutron star or a black hole. These explosions matter personally. The Big Bang made essentially only hydrogen and helium; everything else — the calcium in your bones, the iron in your blood, the oxygen you are breathing — was fused inside stars and scattered by their deaths, to be swept up into later generations of stars, planets and eventually people. The astronomer Carl Sagan’s line that we are made of star stuff is not poetry; it is an inventory. Betelgeuse, the red supergiant in Orion’s shoulder — high in New Zealand’s summer sky — is expected to go supernova sometime in the next hundred thousand years, at which point it will briefly rival the full Moon.

The Milky Way

Zoom far enough out and the sky’s faint band resolves into what it really is — our own galaxy seen edge-on from inside. The Milky Way is a barred spiral roughly 100,000 light years across containing somewhere between 100 and 400 billion stars (the honest range; counting stars you cannot see individually is hard). The Sun sits about 26,000 light years from the centre, out in a minor spiral arm, completing one galactic orbit every 230 million years or so. The last time we were on this side of the galaxy, dinosaurs were new.

At the exact centre sits Sagittarius A*, a black hole of 4.3 million solar masses. Its existence was established by tracking stars whipping around an invisible point at thousands of kilometres per second — work that won the 2020 Nobel Prize in Physics — and in 2022 the Event Horizon Telescope produced a direct image of its glowing shadow. New Zealand, incidentally, has one of the best seats in the house for galaxy-watching: from our latitudes the galactic centre passes nearly overhead on winter nights, and the Magellanic Clouds — two dwarf galaxies 160,000 and 200,000 light years away, orbiting the Milky Way — are visible only from the southern hemisphere.

Black holes and gravitational waves

Black holes deserve their own section, partly because the modern theory of them is a New Zealand export. In 1963 Roy Kerr, born in Kurow and educated at Canterbury, solved Einstein’s equations for a rotating mass — the Kerr metric — which turned out to describe essentially every real black hole in the universe. Physicists regard it as one of the most important exact solutions in general relativity, and it earned Kerr the 2016 Crafoord Prize, astronomy’s counterpart to a Nobel.

For decades black holes were theory. Now they are catalogued. The Event Horizon Telescope has photographed two (the giant in galaxy M87 in 2019, our own Sagittarius A* in 2022). And since 2015, when the LIGO observatories felt two black holes collide 1.3 billion light years away, we have been able to hear them: gravitational waves, ripples in space-time predicted by Einstein a century earlier, are now detected routinely. One 2017 event — two neutron stars merging — was seen in both gravitational waves and light, and confirmed that collisions like it forge most of the universe’s gold and platinum. The wedding rings of New Zealand were made in events like that one.

The Local Group and the Andromeda collision

Galaxies come in groups. Ours, the Local Group, spans about ten million light years and contains the Milky Way, the larger Andromeda Galaxy at 2.5 million light years, the Triangulum Galaxy, and around a hundred dwarf galaxies — with new faint members still being discovered. Andromeda is the most distant object routinely visible to the naked eye; the light entering your eye when you spot it left before humans existed.

Andromeda is also approaching us at about 110 kilometres per second. In roughly 4.5 billion years the two galaxies will collide and, over a billion further years, merge into a single giant galaxy. “Collide” is a gentle word here — stars are so far apart that essentially none will hit each other. The galaxies will pass through one another like two swarms of gnats, be pulled apart by gravity, fall back, and settle into one. The Sun, by then a dying star, will likely be flung to a new orbit in the merged galaxy’s outskirts.

Superclusters and the cosmic web

Groups of galaxies cluster into superclusters. Ours was long called the Virgo Supercluster, some 110 million light years across, but in 2014 a team led by astronomer R. Brent Tully redrew the map by tracking how galaxies actually move, and found we belong to something larger — Laniakea, “immense heaven” in Hawaiian, a basin of gravitational attraction 520 million light years wide containing roughly 100,000 galaxies. Within it, everything drifts towards a mass concentration called, with astronomers’ typical understatement, the Great Attractor.

If you somehow could step back to a vantage point billions of light years away and look at the universe, you would not see galaxies scattered randomly. You would see filaments — vast strings and walls of galaxies, arranged in a pattern that astronomers call the cosmic web. Between the filaments are voids — regions of nearly empty space, hundreds of millions of light years across, with almost nothing in them. Surveys like the Sloan Digital Sky Survey have mapped millions of galaxies to reveal this structure directly, including walls of galaxies more than a billion light years long.

The cosmic web’s pattern emerged from tiny variations in density in the very early universe — quantum fluctuations that got blown up to cosmic size. Wherever the density was a little higher, gravity pulled more matter in over the following billions of years; wherever it was a little lower, matter drained away. Supercomputer simulations that start from the infant universe’s measured conditions and run 13.8 billion years forward produce webs statistically identical to the one we observe — one of the quiet triumphs of modern cosmology. We sit on a filament, near the boundary of a great void called the Local Void, in a galaxy that is one of trillions.

The observable universe by the numbers

Here is the current best accounting of everything we can see. Age: 13.8 billion years, measured to better than one percent by the Planck satellite‘s map of the Big Bang’s afterglow. Diameter: 93 billion light years. Contents: somewhere between 200 billion and two trillion galaxies, holding a number of stars usually estimated at around a billion trillion — by some estimates, more stars than grains of sand on all of Earth’s beaches. Temperature: 2.7 degrees above absolute zero, the faint microwave glow left over from the beginning, discovered by accident in 1965 and mapped in exquisite detail since.

And the composition — the single most humbling pie chart in science. Ordinary matter, meaning every star, planet, gas cloud, and person, makes up about 5 percent of the universe. About 27 percent is dark matter, and about 68 percent is dark energy. Everything astronomy has ever photographed is a twentieth of what exists.

The size of the universe is the size of light’s journey

Everything we know about the size of the universe is constrained by the speed of light. The observable universe isn’t the whole universe — it’s the part close enough that light has had time to reach us in the 13.8 billion years since the Big Bang. The radius of that bubble works out to about 46 billion light years (more than 13.8 because space itself has been expanding while the light was in transit). Outside that bubble, by definition, we can see nothing. There may be more universe out there — almost certainly there is — but its light hasn’t arrived and never will under our current understanding of physics.

Inflation theory, the leading account of the universe’s earliest fraction of a second, suggests the actual universe is at least 250 times larger than the observable bubble in every direction. Some versions of inflation suggest it is effectively infinite. We don’t know which, and we may never know. The pixel at the end of the animation isn’t “the edge of the universe.” It’s the edge of what we can see. Beyond it could be more of the same, indefinitely.

Looking out is looking back in time

Because light travels at a fixed speed, every telescope is a time machine, and the universe arrives at your eye in layers of history. You see the Moon as it was 1.3 seconds ago and the Sun as it was 8 minutes ago. Matariki’s light left around the time of the English Civil War. Look at Andromeda and you are seeing light that set out 2.5 million years ago, when our ancestors were early hominins on the African savannah — and an astronomer in Andromeda pointing a telescope back at us tonight would see exactly that Earth, not ours. The deepest images from the James Webb Space Telescope show galaxies as they were more than 13 billion years ago, within a few hundred million years of the beginning.

This is not a defect of astronomy; it is its superpower. Because distance equals lookback time, the universe conveniently displays its own history at every depth, like geological strata laid out in the sky. Astronomers cannot watch one galaxy evolve for billions of years, but they can compare millions of galaxies at different distances — different ages — and read the whole storyline. It also means “now” is a slippery idea at cosmic scales. There is no universal present moment stretched across the universe; there is only what the light arriving here tonight can tell you.

How we measure distances in space

A fair question about everything above is — how could anyone possibly know? The answer is a chain of overlapping methods astronomers call the cosmic distance ladder. The first rung is parallax, simple geometry: as Earth orbits the Sun, nearby stars appear to shift slightly against the background, and the size of the shift gives the distance. The European Space Agency’s Gaia mission has measured positions and parallaxes for nearly two billion stars, turning the Milky Way into a three-dimensional map.

Beyond parallax’s reach, astronomers use standard candles — objects whose true brightness is known, so their apparent faintness reveals their distance. Cepheid variable stars pulse at a rate tied to their brightness; a particular kind of exploding white dwarf, a Type Ia supernova, detonates with near-identical brightness every time and can be seen across billions of light years. The final rung is redshift — light from distant galaxies arrives stretched to redder wavelengths because space itself has expanded during the journey, and the amount of stretching tells you how far the light has come. Each rung calibrates the next, and the whole ladder is cross-checked constantly. It is not perfect — the two best methods for measuring the universe’s current expansion rate disagree by about nine percent, a live controversy called the Hubble tension — but disagreements like that are how the field moves.

The history of the universe

Run the expansion backwards and everything converges on a beginning 13.8 billion years ago. What banged, and why, is unknown — the Big Bang theory describes what happened after the first instant, not the instant itself. From there the story is surprisingly well established. In the first minutes, the entire universe was hot enough to act as a fusion reactor, cooking up the primordial mix of about 75 percent hydrogen and 25 percent helium that stars have been reprocessing ever since. Every heavier atom in your body was assembled later, inside stars.

At 380,000 years, the universe cooled enough for atoms to form and light to travel freely — that liberated light is the cosmic microwave background mapped by the WMAP and Planck missions, a baby photo of the universe showing temperature ripples of one part in 100,000 that would grow into every galaxy. Then came a hundred million years of darkness before the first stars ignited. The James Webb Space Telescope has now photographed galaxies whose light left them less than 300 million years after the Big Bang — the universe building its first structures faster and more vigorously than models predicted, which is exactly the kind of productive surprise a good telescope exists to deliver. Since then the story has been nine billion years of galaxy assembly, the birth of the Sun and Earth 4.6 billion years ago from a cloud enriched by earlier stellar generations, and — at least once, on one damp rock — chemistry that learned to ask questions.

Dark matter and dark energy

The two largest entries in the cosmic inventory are placeholders for ignorance, and it is important to say so plainly. Dark matter is the name for whatever provides the extra gravity that observations demand: galaxies rotate too fast to hold together on visible matter alone, clusters bend light more than their visible mass allows, and the cosmic web grew too quickly without it. Something real is there — five times more of it than ordinary matter — and decades of increasingly sensitive experiments, including detectors deep underground, have so far failed to catch a single particle of it. Every non-detection narrows the possibilities.

Dark energy is stranger. In 1998 two teams measuring distant supernovae — expecting to find the expansion of the universe slowing under gravity — found it accelerating, a result so unexpected it earned the 2011 Nobel Prize in Physics. Whatever pushes that acceleration is called dark energy, and it behaves like a property of space itself: more space, more push. Intriguingly, recent results from the DESI galaxy survey hint that dark energy’s strength may be weakening over time. If that holds up — and it is early days, not a settled result — it would be the biggest shift in cosmology in a generation. Watch this space, in the most literal sense available.

What we still do not know

An honest summary of the universe has to include the open questions, because they are not small. We do not know what 95 percent of the universe is made of. We do not know what happened in the first instant, whether inflation is correct, or what — if anything — preceded the Big Bang. We do not know why the universe’s expansion rate measures differently by two rigorous methods, why matter exists at all when the Big Bang should have made matter and antimatter in equal, mutually annihilating amounts, or whether the constants of physics are fixed everywhere and forever.

And we do not know whether anyone else is out there. The galaxy is old enough, and planets common enough, that the silence is itself a data point — the puzzle physicist Enrico Fermi posed in 1950 with the question “where is everybody?” Perhaps life is common but intelligence rare; perhaps civilisations are short-lived; perhaps the listening has simply been too brief — serious radio searches span mere decades against a galaxy 13 billion years old. It remains one of the deepest unanswered questions a person can hold in their head at 2am, which is why several of the essays linked above orbit it.

The far future of the universe

The current picture points to a long, slow ending. In five billion years the Sun becomes a red giant, likely ending Earth’s habitability well before that. The Milky Way and Andromeda merge. Star formation, galaxy by galaxy, gutters out over the next hundred trillion years as gas runs low, leaving white dwarfs, neutron stars and black holes. If the expansion keeps accelerating, distant galaxies slip one by one over the horizon of visibility, until — on timescales that make the current age of the universe a rounding error — a far-future astronomer in our merged galaxy would look out and see nothing at all, and might reasonably conclude the universe was one galaxy in an infinite dark. The lesson cosmologists draw from that thought experiment is worth keeping — we may already be similarly fooled about things the universe’s history has hidden from us.

None of this is cause for alarm — the timescales are beyond comprehension, and predictions this far out inherit every uncertainty above, particularly whatever dark energy decides to do. It is simply the current best extrapolation, held as lightly as it should be.

New Zealand’s place in the story of the universe

For a small country, New Zealand has left real fingerprints on cosmology. Roy Kerr’s 1963 solution for rotating black holes, mentioned above, is on any shortlist of the twentieth century’s great results in physics. Beatrice Tinsley, raised in New Plymouth and educated at Canterbury, founded the modern study of how galaxies evolve — showing they change and fade over cosmic time, which upended distance measurements that had assumed galaxies were constant — and became Yale’s first female professor of astronomy before her death at just 40 in 1981. A peak in Fiordland’s Kepler Mountains now carries her name. And on a February night in 1987, Albert Jones, a legendary amateur observer in Nelson with over half a million variable-star observations to his name, became one of the first people on Earth to see Supernova 1987A brightening in the Large Magellanic Cloud — the nearest supernova in four centuries, visible only from southern skies.

The southern sky itself is a national asset. The University of Canterbury’s Mt John Observatory at Tekapo has operated since 1965, and its MOA telescope — a Japan–New Zealand collaboration — has discovered distant exoplanets by catching the momentary gravitational lensing of background stars. The surrounding Aoraki Mackenzie International Dark Sky Reserve, established in 2012, is among the largest in the world, joined since by dark sky sanctuaries and reserves at Aotea Great Barrier Island, Rakiura Stewart Island and Wairarapa. Matariki’s return to the winter dawn sky has been a calendar anchor in te ao Māori for centuries and is now a public holiday for everyone. Few countries have better naked-eye access to the galactic centre, the Magellanic Clouds and the aurora australis — the Royal Astronomical Society of New Zealand maintains resources for anyone who wants to start looking up.

Quick answers about the universe

How old is the universe? 13.8 billion years, measured from the cosmic microwave background to better than one percent precision.

How big is the universe? The observable universe is about 93 billion light years across. The whole universe is at least 250 times larger, and may be infinite — we genuinely do not know.

What is the universe made of? About 5 percent ordinary matter, 27 percent dark matter and 68 percent dark energy. The nature of the last two is unknown.

How many galaxies are there? Estimates range from 200 billion to two trillion in the observable universe alone.

How many stars are there? On the order of a billion trillion in the observable universe — around 100 to 400 billion in our Milky Way.

What is at the centre of the universe? Nothing — or equivalently, everywhere. The Big Bang happened at every point at once; space itself has been expanding ever since. Every galaxy sees the others receding from it.

What is beyond the observable universe? Almost certainly more universe, whose light has not had time to reach us. Its extent is unknown and possibly unknowable.

Will the universe end? Current evidence favours indefinite expansion — a slow fade over timescales trillions of times the universe’s current age — but that forecast depends on dark energy, which we do not yet understand.

What is a light year? The distance light travels in one year — about 9.46 trillion kilometres. It measures distance, not time, though it doubles as a reminder that looking far away means looking into the past.

What is the cosmic microwave background? The oldest light in existence — the glow released when the universe became transparent 380,000 years after the Big Bang, now stretched by expansion into a faint microwave hiss arriving from every direction at 2.7 degrees above absolute zero.

Can humans travel to another star? Not with any current or near-term technology. The nearest star system is 4.24 light years away; the fastest spacecraft ever flown would take thousands of years. Proposals exist — laser-driven light sails could in principle cut that to decades for gram-scale probes — but they remain proposals.

Where did the Big Bang happen? Everywhere. It was not an explosion into empty space; it was the expansion of space itself, and it happened at every point in the universe at once — including the point where you are sitting.

Sources and further reading

The figures on this page reflect the mainstream published values as of 2026, drawn from NASA’s solar system science pages, the Voyager mission status, ESA’s Gaia and Planck missions, the NASA Exoplanet Archive, the Event Horizon Telescope, LIGO, the Sloan Digital Sky Survey and the 2014 Laniakea paper in Nature. Where the science is unsettled — dark energy’s behaviour, the Hubble tension, the universe’s total size — the text says so rather than pretending otherwise.

Why this changes anything

The numbers are too large to mean much in a physical sense. We don’t have intuitions for them. But the awareness of where we sit in this scale changes some practical things. It is much harder to hold onto certain kinds of self-importance. It is much easier to recognise that the things that worry us locally — careers, ambitions, small daily catastrophes — are real but operate on a vanishingly thin slice of a vast and largely empty cosmos. The four “Shit That Keeps Me Awake” pieces above explore what people have done with this knowledge: ideas about the universe being alive, or us being microbes inside something larger, or a Great Filter explaining the silence we hear when we listen for other civilisations. They are speculation, but they are honest speculation about what it means to live inside a universe this large.