Antimatter: why didn’t it wipe us out at the beginning of the universe?
SVET ZA 5 MINÚT · Science and space · approximately 6–8 minutes to read
When a particle meets its antiparticle, the two can annihilate. Yet the early universe produced enormous quantities of both matter and antimatter. Why did their encounters leave enough building material for galaxies, Earth and us?
There are two parts to the answer. The first is a tiny excess of matter: after most of the pairs disappeared, something remained. The second, more important part is still missing. Why did that excess arise in the first place? This is why scientists make and study antimatter. Its greatest value may lie less in the energy it releases than in what it can reveal about our origins.
What exactly is antimatter?
Ordinary atoms contain electrons and nuclei made of protons and neutrons. These particles have counterparts: the electron has the positron, the proton has the antiproton, and the neutron has the antineutron. Antimatter is material made from antiparticles. It is not an invented substance from a thriller; the positron was experimentally discovered in 1932. 1
The electron and positron provide the simplest example. They have the same mass but opposite electric charges: the electron is negative, the positron positive. Similarly, a proton has a positive charge and an antiproton a negative one. Bind an antiproton to a positron and you have an atom of antihydrogen.
Opposite charge is a useful introduction, rather than a complete definition. Neutrons and antineutrons are both electrically neutral; they differ in their internal quark and antiquark composition and other properties. Some particles are even their own antiparticles. The prefix “anti” therefore means more than simply reversing an electrical sign. 2
Particles disappear; energy does not
An encounter between a particle and its antiparticle can lead to annihilation. The original pair disappears, but its energy and momentum are carried away by the reaction products. A slow electron and positron can produce two gamma-ray photons travelling in approximately opposite directions.
Our reel represents this with two pulses of light. Their colour, size and speed are illustrative: gamma rays are invisible to human eyes. What matters is that annihilation does not leave “nothing”. Energy continues in another form.
Not every annihilation produces just two photons. A proton and antiproton can produce other particles as well. It is therefore more accurate to describe a transformation into radiation or other particles than a universal disappearance into “pure energy”. The products are physical things that carry energy, rather than an undefined substance called energy. 1
Why expect equal amounts in the first place?
The early universe was extraordinarily hot and dense. Energy could produce particle–antiparticle pairs, which could annihilate again. This was not a single explosion involving two ready-made clouds of material. It was a vast network of reactions in an environment that was expanding and cooling.
In many familiar processes, a particle is created together with its antiparticle. A symmetrical beginning is therefore a natural starting point: without a mechanism favouring one side, we cannot explain today's enormous imbalance. Saying that “equal amounts of matter and antimatter should have formed” expresses this expectation. It does not mean someone has directly counted particles at the Big Bang. 1, 2
As the universe cooled, making heavier pairs became harder, while annihilation continued to remove existing pairs. If the balance had been perfect and every pair had annihilated, no material would have remained for ordinary atoms, stars or people. A full cosmological calculation must also account for reaction rates and expansion. The essential problem is that a simple symmetrical picture does not explain the matter-filled universe we observe.
So what actually happened?
The leading explanation is that a small surplus of matter emerged early in cosmic history. A common illustration is approximately one extra matter particle for every billion matter–antimatter pairs. This conveys the scale of the imbalance; it is not a precise snapshot of one instant. 2
Imagine ten blue tokens and ten orange tokens. Remove one of each colour at a time and none remain. Start instead with eleven blue tokens and ten orange ones, and a blue token survives. It was not tougher or more powerful than the others. It simply ran out of partners to be removed with.
This analogy explains how a very small initial advantage can determine the final outcome. It does not explain where the eleventh token came from. That is where the scientific investigation begins. Nor did stars and planets appear seconds after annihilation: the surviving excess became part of a much longer cosmic history. The familiar objects around us emerged far later.
The distinction matters. “A little more matter survived” describes the outcome we need to explain. It is not, by itself, a mechanism that explains the imbalance. Replacing a mystery with a new name would not solve it.
Have we already found differences?
Yes. Certain particle decays reveal different behaviour between matter and antimatter. This is associated with the violation of CP symmetry. In a simplified description, the question is: if we replace particles with antiparticles and also mirror the spatial arrangement, will the process occur with the same probability? In some cases, the answer is no. 3
This does not mean antimatter generally has less mass or always decays faster. These are differences in particular processes and probabilities. For example, in 2025 the LHCb collaboration announced an observation of CP asymmetry in decays of the lambda-b baryon and its antiparticle. Baryons are the particle family that includes protons and neutrons, but the lambda-b studied here is a heavy, short-lived relative. 4
Such discoveries are not yet a complete explanation for our existence. The known sources of CP asymmetry in the Standard Model are insufficient to account for the observed cosmic imbalance. Researchers therefore search for additional mechanisms while measuring familiar ones more precisely. A meaningful new clue and a solved cosmic mystery are different achievements. 3
How do you study something that annihilates on contact?
You cannot simply pour antiparticles into a container. Its walls are made of ordinary matter. Scientists instead hold charged antiparticles in a vacuum using a suitable combination of electric and magnetic fields, keeping their trajectories away from the walls. Neutral antihydrogen atoms require a different magnetic trapping technique and sufficiently low temperatures. 1, 5
The BASE experiment, for instance, compares the magnetic properties of protons and antiprotons. Other teams investigate how antihydrogen absorbs light. These comparisons test whether fundamental physical rules hold for antimatter. Agreement constrains alternative explanations; a carefully measured absence of a difference is valuable evidence too. 5, 6
These experiments do not all test the same symmetry. Precision measurements of basic properties often test CPT symmetry, which also includes time reversal. A violation of CPT would be distinct from the already observed CP violation in decays. Finding the latter does not mean the former has also been broken.
This is one reason a story about “scientists finding a difference” needs context. Which property? Which reaction? How large is the uncertainty? The answers determine whether a measurement confirms an expectation or challenges it.
Does antimatter fall upwards?
Negative electric charge is not negative mass. In 2023, the ALPHA-g experiment directly tracked released antihydrogen atoms and observed behaviour consistent with Earth's gravitational attraction. In that experiment, antihydrogen fell downwards. 7
This did not settle every question about gravity and antimatter. The result had a finite precision, and further measurements can test for subtler deviations. It was, however, a decisive move from speculation about “antigravity” to measurements of actual antiatoms.
Could it supply our electricity?
Annihilation can release a large amount of energy from a small mass. Using Einstein's E = mc², complete annihilation of one gram of antimatter with one gram of matter would release approximately 1.8 × 10¹⁴ joules, equivalent to 50 gigawatt-hours of energy. This is our calculation for two grams in total, not an estimate of usable electrical output.
The catch is production. We first have to manufacture the antimatter, currently spending far more energy than we can recover. Further losses arise in capture, storage and conversion of the annihilation products into useful energy. 8
Manufactured antimatter would therefore be an exceptionally demanding energy store, rather than a new primary energy source. Perfect storage would not remove the need to make it first. Nor do the portable supplies imagined in films resemble the minute amounts handled in laboratories. 1
Useful already — and still a profound mystery
Positrons are used in PET, or positron emission tomography. A radioactive tracer emits positrons inside the body. After slowing down, they annihilate with electrons, and the scanner detects the resulting photons. Many such events allow the tracer's distribution to be reconstructed, providing information about tissue function. 9, 10
Antimatter does not have to power a station to be useful. Its scientific importance reaches further still. Here, “why do we exist?” means a specific physical question: why did enough matter survive to build structures from which life could eventually emerge? It is not an explanation of life's purpose or a final answer to why the universe itself exists.
We know that matter remained. We can investigate its antiparticle counterparts. What we still lack is the complete story of how an almost balanced beginning became the universe we inhabit.
Follow @svetza5minut — discover what is happening on Earth and beyond.
Sources and further reading
Fact-checked 25 October 2026