All the content of the universe, in a single graph
Scientists agree that the universe is made up of three distinct parts: everyday visible (or measurable) matter and two theoretical components called dark matter and dark energy.
The latter two are theoretical as they have yet to be 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:
|Free hydrogen and helium||4%|
Let’s look at each component in more detail.
Dark energy is the theoretical stuff that counteracts gravity and causes the universe to expand rapidly. It is the biggest part of the makeup of the universe, permeating every corner of the cosmos and dictating how it behaves and how it will eventually end.
Dark matter, on the other hand, has a restraining force that works closely with gravity. It is a kind of “cosmic cement” responsible for holding the universe together. Although it evades direct measurements and remains a mystery, scientists believe it is the second largest component of the universe.
Free hydrogen and helium
Free hydrogen and helium are elements that float freely in space. Although they are the lightest and most abundant elements in the universe, they make up about 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 populated things we can see when looking at the night sky, yet they make up less than 1% (about 0.5%) of the cosmos.
Neutrinos are subatomic particles similar to electrons, but they are nearly weightless and carry no electrical charge. Although they explode with each nuclear reaction, they represent about 0.3% of the universe.
Heavy elements are all other elements except hydrogen and helium.
Elements are formed in a process called nucleosynthesis, which takes place in stars throughout their lifetime and upon their explosive death. 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 measly 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 gave birth to 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 space. When studying the “microwave sky”, researchers look for fluctuations (called anisotropy) in the temperature of the CMBR. Instruments like Planck help reveal the extent of CMBR’s temperature irregularities and tell us about the different components that make up the universe.
You can see below how the clarity of CMBR changes over time with multiple space missions and more sophisticated instrumentation.
What else is 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 is beyond the universe? Scientists aren’t sure.
There are hypotheses that there could be a larger “super universe” that contains us, or we could be part of an “island” universe separate from the other island multiverses. Unfortunately, we are not yet able to measure anything from that far away. Unraveling the mysteries of the deep cosmos, at least for now, remains a local business.