Space is one of the great mysteries that has captivated humanity since the beginning of civilization.
This expansive void that surrounds our planet holds endless fascination, and new discoveries are constantly reshaping our understanding of the cosmos.
From distant galaxies to the particles that make up the universe, the contents of space unlock secrets about our very existence.
The Main Components of Space
At the most fundamental level, matter and energy make up space. Subatomic particles such as protons, neutrons, and electrons group together to form the atoms that constitute everything in the observable universe. Hydrogen and helium are the most abundant elements in the cosmos and on Earth. Stars’ nuclear fusion reactions produce trace amounts of heavier elements in space.
Dark Matter and Dark Energy
In addition to normal matter, two mysterious components fill space: dark matter and dark energy. We cannot directly observe dark matter, but we infer its existence from its gravitational effects on visible matter and light. This invisible matter likely constitutes over 80% of the universe’s total mass. While we don’t yet understand dark matter’s nature, leading theories suggest it consists of undiscovered subatomic particles, such as weakly interacting massive particles (WIMPs).
Dark energy perplexingly drives the universe’s accelerating expansion. This odd energy saturates the cosmos and pushes space outward with a negative pressure. Though invisible, we can observe dark energy’s influence on the universe’s growth over time. Combined, dark matter and dark energy might make up to 95% of the universe’s total energy density.
Atomic and Subatomic Particles
At the smallest scale, a zoo of exotic particles fills space, forming the fundamental building blocks of matter. Once considered indivisible, atoms contain even tinier elementary particles like electrons, protons, and neutrons. When we probe deeper, we can break down these subatomic particles further into quarks and other fundamental particles that quantum mechanics governs.
Some theories suggest that elementary particles called neutrinos constantly travel through space, interacting very rarely with normal matter. Experiments detect billions of these ethereal neutrinos streaming from the Sun. Cosmic ray collisions also produce particles in space, such as positrons and pions, which travel through the void at nearly the speed of light.
This article’s list is not exhaustive, as scientists continue to discover new exotic particles like the Higgs boson using powerful atom smashers. Understanding the relationships between the quantum particles that fill space is an ongoing physics quest.
Gases Like Hydrogen and Helium
Outer space is filled with diffuse clouds of gas, mostly hydrogen and helium. These primordial leftovers from the Big Bang account for about 10-30% of the ordinary matter in the universe. Thin wisps of neutral hydrogen span millions of light years between galaxies.
Denser pockets of gas collapse to form giant clouds where stars are born. Ionized gas gets superheated to millions of degrees in stellar atmospheres and supernova remnants. This hot plasma glows brightly at X-ray wavelengths.
Complex molecules like water and alcohol have also been found in interstellar gas clouds. Space gases interact with cosmic rays and magnetic fields, glowing vividly during collisions. Understanding the life cycle of intergalactic gases is key to mapping galactic evolution.
Electromagnetic Radiation Like Light and Heat
Outer space is awash in electromagnetic radiation, from radio waves to gamma rays. Visible light from stars allows us to see the universe. Infrared radiation carries heat across light years. X-rays and gamma rays flare explosively from supernovae and black holes.
The cosmic microwave background is the thermal radiation left over from the Big Bang, permeating the entire universe. Synchrotron radiation from accelerating charged particles spirals along magnetic fields. Spectral lines reveal the composition of distant stars and gases.
Mapping the electromagnetic spectrum across space and time paints a detailed portrait of cosmic evolution. Radiation signatures help us probe the fundamental forces of nature. Understanding spacetime’s luminous energy flows is key to unraveling what space is made of.
Einstein predicted gravitational waves – ripples in spacetime generated by accelerating masses. In 2015, scientists detected these waves for the first time from two merging black holes over a billion light years away.
Gravitational waves allow us to study the most violent events in the universe, like colliding neutron stars and supermassive black holes orbiting each other. They provide a completely new way to observe the cosmos.
Mapping gravitational waves across space and time will reveal previously invisible black holes and neutron stars. Combining gravitational and electromagnetic observations provides an incredibly detailed multi-messenger view of cosmic events. Understanding gravitational waves is pivotal to unraveling what space-time itself is made of.
Neutrinos are nearly massless subatomic particles produced by nuclear reactions in stars, supernovae, or even particle accelerators on Earth. Trillions of neutrinos pass through your body every second without interacting.
Despite their ghostly nature, neutrinos provide insight into the particle zoo and the evolution of cosmic structures. Detecting solar neutrinos confirmed that nuclear fusion powers the Sun. Observing supernova neutrinos could reveal the mechanism behind these titanic stellar explosions.
Future neutrino experiments will help explain the dominance of matter over antimatter in our universe. Mapping the cosmic neutrino background may unveil conditions in the early universe. Understanding these ubiquitous particles is key to comprehending cosmic evolution across all scales.
The Cosmic Microwave Background
The cosmic microwave background (CMB) is relic radiation from the early universe, just 380,000 years after the Big Bang. As the universe expanded and cooled, photons decoupled from matter, creating this faint afterglow permeating all of space.
First predicted by theories of cosmic evolution, the CMB was serendipitously discovered in 1964 by radio astronomers Arno Penzias and Robert Wilson. Their Nobel Prize-winning observation confirmed the Big Bang theory and launched the field of observational cosmology.
Today, space telescopes like COBE, WMAP, and Planck map tiny temperature fluctuations within the CMB. These anisotropies reflect the primordial seeds that grew into galaxies and cosmic structures. Analyzing the CMB provides precise constraints on essential cosmological parameters, shedding light on cosmic ingredients and evolution.
The CMB’s perfect blackbody spectrum and exquisite uniformity point to the universe’s hot, smoothly distributed beginnings. Delving into this ancient light remains pivotal to unraveling cosmic mysteries and the laws of physics.
Black holes are regions of spacetime exhibiting gravitational acceleration so strong that nothing—no particles or even electromagnetic radiation—can escape from inside the event horizon. The boundary of a black hole, the event horizon, marks the point of no return where the escape velocity equals the speed of light.
According to general relativity, a sufficiently compact mass can deform spacetime to form a black hole. Stellar-mass black holes originate from the gravitational collapse of massive stars at the end of their lifecycles. Supermassive black holes weighing millions to billions of solar masses exist at the centers of most galaxies.
Black holes bend spacetime in their vicinity. Their intense gravity alters paths of nearby matter and photons, giving rise to observational signatures like gravitational lensing and accretion disks with intense X-ray emissions. As no light escapes, black holes cannot be directly observed. But astronomers infer their presence from interactions with surroundings.
The no-hair theorem states that black holes have only three observable properties – mass, charge, and angular momentum. But their gravitational influence has profound implications for astrophysics, from powering quasars and other active galactic nuclei to shaping galaxy evolution.
Antimatter is composed of antiparticles that have the same mass as their particle counterparts but opposite charge. When a particle and antiparticle come into contact, they annihilate each other in a flash of energy. Natural antimatter occurs transiently in some high-energy environments.
The Big Bang should have created equal amounts of matter and antimatter. But today’s universe is almost entirely matter. The small excess enabled matter to prevail over complete annihilation. The source of this asymmetry remains an open question in physics.
Antimatter particles can be generated artificially in particle accelerators. Positrons are used in medical imaging. Future applications could involve antimatter engines or explosives. However, antimatter is scarce and unstable, posing storage challenges for these potential uses.
CPT symmetry requires that matter and antimatter particles share similar properties like mass, spin, and lifetime. However, subtle differences like neutrino oscillations violate CP symmetry. Understanding the matter-antimatter asymmetry may reveal new physics beyond the Standard Model.
While antimatter occurs naturally, it remains unknown whether macroscopic quantities like anti-atoms or anti-stars exist. Some theories predict that antimatter galaxies or anti-universes could exist. But antimatter counterparts to ordinary matter have not been observed astronomically.
What is space made of if not air?
Space is filled with various forms of radiation, magnetic fields, neutrinos, dust, and gas. While there are trace amounts of elements like hydrogen and helium, space is essentially a vacuum containing very little actual matter.
What’s empty space made of?
Empty space contains quantum fields and fluctuations that give rise to virtual particles popping in and out of existence. It also contains dark energy which causes the universe to expand.
Is space made of dark matter?
No, space and dark matter are separate things. Dark matter is a hypothetical form of matter that does not interact with light but exerts gravitational effects. Dark matter exists within space but does not comprise the vacuum of space itself.
Why is space dark?
Space appears dark because there are no nearby stars or other light sources. Photons from distant stars get absorbed over vast cosmic distances, so the space between galaxies is mostly empty and therefore dark.
Space is not completely empty, but consists of a vacuum containing trace amounts of matter and energy. The most abundant elements are hydrogen and helium gases. Space also contains cosmic microwave background radiation, magnetic fields, neutrinos, and dark energy. While dark matter exists within space, space itself does not consist of dark matter. The vast distances between stars and galaxies is what makes most of outer space appear dark.