All the contents of the universe, in a graph
Scientists agree that the universe consists of three distinct parts: everyday visible (or measurable) matter and two theoretical components called dark matter and dark energy.
The latter two are theoretical because they have not yet been directly measured, but even without a full understanding of these mysterious puzzle pieces, scientists can infer that the composition of the universe can be broken down as follows:
ComponentValue Dark energy68% Dark matter27% Free hydrogen and helium4% Stars0.5% Neutrinos0.3% Heavy elements0.03%
Let’s look at each component in more detail.
dark energy
Dark energy is the theoretical substance that counteracts gravity and causes the rapid expansion of the universe. It is the largest part of the makeup of the universe, permeating every corner of the cosmos and dictating how it behaves and how it will end.
dark matter
Dark matter, on the other hand, has a constraining force that works closely alongside gravity. It is a kind of “cosmic cement” responsible for holding the universe together. Despite eluding direct measurement and remaining a mystery, scientists believe it constitutes the second largest component in the universe.
Free hydrogen and helium
Free hydrogen and helium are elements that float freely in space. Despite being the lightest and most abundant elements in the universe, they represent approximately 4% of its total composition.
Stars, neutrinos and heavy elements
All other hydrogen and helium particles that do not float freely in space exist in stars.
Stars are one of the most populous things we can see when we look up at the night sky, but they make up less than one percent, about 0.5%, of the cosmos.
Neutrinos are subatomic particles that are similar to electrons, but are almost weightless and carry no electrical charge. Although they come out of every nuclear reaction, they make up about 0.3% of the universe.
Heavy elements are all elements other than hydrogen and helium.
Elements are formed in a process called nucleosynthesis, which takes place inside stars throughout their lives and during their explosive deaths. Almost everything we see in our material universe is made up of these heavy elements, but they make up the smallest part of the universe: a tiny 0.03%.
How do we measure the universe?
In 2009, the European Space Agency (ESA) launched a space observatory called Planck to study the properties of the universe as a whole.
Its main task was to measure the afterglow of the explosive Big Bang that originated the universe 13.8 billion years ago. This afterglow is a special type of radiation called cosmic microwave background radiation (CMBR).
Temperature can tell scientists a lot about what’s out there in outer space. When investigating the “microwave sky,” researchers look for fluctuations (called anisotropy) in the temperature of the CMBR. Instruments like Planck help to reveal the extent of irregularities in the temperature of the CMBR and inform us about the different components that make up the universe.
Below you can see how the clarity of CMBR changes over time with multiple space missions and more sophisticated instrumentation.
What else is out there?
Scientists are still working to understand the properties that make up dark energy and dark matter.
NASA is currently planning the 2027 launch of the Nancy Grace Roman Space Telescope, an infrared telescope that will hopefully help us measure the effects of dark energy and dark matter for the first time.
As for what lies beyond the universe? Scientists aren’t sure.
There are hypotheses that there may be a larger “super universe” that contains us, or that we are part of an “island” universe separate from other island multiverses. Unfortunately, we can’t measure anything that far yet. Unraveling the mysteries of the deep cosmos, at least for now, remains a local endeavor.