The universe is an astonishingly massive place, filled with trillions of galaxies, stars, and planets. Yet scientists have found that much of the universe seems to be missing. So how much of the universe is actually unaccounted for? Let’s take a closer look at what we know, and what mysteries remain.
How do scientists measure the universe?
Scientists use a variety of methods to measure the amount of matter and energy in the universe. Some key ways include:
- Observing the motion and gravitational effects of galaxies and galaxy clusters
- Measuring radiation from the early universe, known as the cosmic microwave background
- Counting stars, galaxies, and other visible matter
- Detecting dark matter through its gravitational effects
By combining these techniques, scientists aim to tally up everything that makes up the universe. However, some glaring gaps have emerged in this cosmic accounting.
How much of the universe is visible?
The part of the universe humans can actually see – stars, galaxies, nebulae, and other objects – accounts for only about 5% of the universe’s total contents. This visible matter comprises the luminous planets, stars, and gases within galaxies. It makes up the beautiful celestial objects visible in the night sky.
Visible matter may seem abundant. But in the grand scheme of the universe, it’s just the tip of the iceberg. The rest lies out of view in the form of dark matter and dark energy.
What is dark matter?
Dark matter makes up about 25% of the universe. It’s aptly named, as this matter does not absorb, reflect, or emit light. It cannot be directly observed. However, scientists infer its existence based on gravitational effects on visible matter and light.
Some key evidence for dark matter includes:
- Galaxy rotation curves – The outer regions of galaxies rotate faster than expected unless extra mass from dark matter is present.
- Gravitational lensing – Background objects are distorted as their light curves around dark matter.
- Cosmic microwave background – Small fluctuations indicate that dark matter existed in the early universe.
The leading hypothesis is that dark matter consists of as-yet undiscovered subatomic particles that interact through gravity but not electromagnetism. Efforts to identify these dark matter particle candidates are ongoing.
What is dark energy?
Dark energy is even more mystifying than dark matter. This invisible force makes up a whopping 70% of the universe’s contents. The discovery of dark energy stemmed from observations indicating the universe is not only expanding – it’s expanding at an accelerating rate.
Dark energy exhibits an anti-gravitational effect, driving galaxies apart rather than pulling them together. Scientists hypothesize that dark energy is embedded in the fabric of space itself. It exerts a constant repulsive force throughout the universe.
Three key pieces of evidence back up the existence of dark energy:
- Supernova data – Observations showed distant supernovas were dimmer than expected in an expanding universe.
- Cosmic microwave background – It revealed variations suggesting dark energy existed early in the universe’s history.
- Large-scale structure – Galaxies show a different distribution than expected unless accelerated expansion from dark energy is included.
The discovery of dark energy is one of the biggest mysteries in physics today. Its nature remains entirely unknown.
Breakdown of the universe’s composition
Based on current measurements and models, here is how the contents of the universe break down:
- 70% is dark energy
- 25% is dark matter
- Only 5% is visible matter that emits or reflects light
This means a whopping 95% of the universe is missing from our direct view. Dark matter and dark energy make up the vast majority of existence – yet we don’t know what either of them actually is.
Why is most of the universe invisible?
There are a few key reasons why the bulk of the universe defies our perception:
- Dark matter does not emit or absorb light. We can only infer its presence indirectly through gravitational effects.
- Dark energy is uniformly spread out. It does not clump or congregate like normal matter.
- Normal matter is sparse. Even concentrated blobs of matter are dwarfed by the scale of invisible substances pervading space.
- Dark substances far outweigh visible matter. They make up over 95% while normal matter is less than 5%.
In other words, dark matter and dark energy are essentially imperceptible forms of matter and energy that vastly outweigh the “normal” contents of space. Our eyes and telescopes miss them simply due to their ethereal nature.
What does this missing universe mean?
The fact that 95% of the universe is invisible has astonishing implications:
- It shows our knowledge of physics is incomplete.
- There are major components of existence about which we know almost nothing.
- There may be other invisible substances still undiscovered.
- Theories need revision to account for the universe’s full contents.
- Our perceptible world is a tiny fraction of what’s really out there.
In short, realizing how much is missing humbles our understanding of nature. It also presents exciting opportunities to uncover more of existence’s true contents.
Some key unanswered questions include:
- What particles make up dark matter?
- Why does dark energy cause accelerated expansion?
- Do dark substances interact with normal matter and energy?
- Are there other invisible components besides dark matter and energy?
- How will understanding the missing universe refine physics theories?
Solving these mysteries promises to revolutionize our comprehension of the cosmos at a fundamental level.
How can we detect the missing universe?
While most of the universe lies beyond our senses, important ways to detect the missing components include:
- Precision measurements – Improved instruments and observations to map gravitational effects and expansion rates.
- Particle colliders – Smashing particles to produce dark matter candidates detectable in particle detectors.
- Direct detection experiments – Lab devices to measure weak interactions between normal matter and passing dark matter particles.
- Space-based observatories – Missions like the Hubble Space Telescope to see farther back in space and time.
Combining these approaches will give us a more complete cosmological view. Scientists are optimistic that remaining secrets of the invisible universe are within reach of discovery in the coming decades.
The overwhelming majority of the universe is invisible to us – missing from our direct observations. Uncovering why so much is missing is a top priority in physics and astronomy. Dark matter and dark energy seem to comprise 95% of existence, yet their origins remain obscure.
Advancing our knowledge in this area promises to transform our understanding of nature at the deepest level. While the missing pieces of the universe present a profound mystery, scientists are unraveling clues that may soon lead to a breakthrough. Headway on these fascinating questions will surely reveal space to be even stranger and more remarkable than we have ever imagined.