Science fiction films have led us to believe that explosions in space produce sound, asteroids travel in dense swarms, and black holes consume everything within their reach. These notions have become so deeply ingrained that they are often accepted as fact. Astrophysicist Oleksandr Veles examined some of the most prevalent myths and explained what actually occurs.
Is there truly silence in space?
Yes, and that is one of the most striking differences between real space and its portrayal in films. On screen, spaceships pass by with the roar of a moped, lasers whistle, and explosions are deafening. If a spaceship were to explode right next to an astronaut, the astronaut would see a bright flash and debris flying in all directions, but would not hear the explosion.
Sound consists of mechanical vibrations of particles and requires a medium — such as air, water, or a solid — to propagate. When we speak, our vocal cords create pressure fluctuations in the air, and these waves reach the ears of the people we are addressing. Interplanetary space is nearly empty; it contains so few particles that sound waves have no medium through which to travel.
The spacecraft contains air, allowing sound to travel through it as it does on Earth. If an astronaut touches the hull, they may feel or even hear vibrations traveling through the structure.
The phrase “listening to space” is appropriate in this context. The universe continually emits signals, including radio pulses from pulsars, electromagnetic radiation from the Sun, and gravitational waves generated by merging black holes. Since humans lack the sensory organs necessary to perceive these signals directly, scientists convert the data into sound through a process known as sonification. Variations in the intensity of a pulsar’s radio signal can be represented by changes in volume, while variations in frequency can be conveyed through pitch, producing a distinct rhythm when heard through headphones. This constitutes an auditory representation of scientific data, even though the waves themselves reached us silently.
Is it possible for a fire to burn in space?
Combustion requires three elements: fuel, an oxidizer (typically oxygen), and a sufficiently high temperature. Removing any one of these elements will extinguish the fire. Because outer space contains virtually no oxygen, a candle thrown overboard will go out immediately.
Rocket engines function effectively in a vacuum. Because a rocket carries both fuel and an oxidizer, it does not require atmospheric oxygen. Combustion can occur in any environment, provided that all necessary components are brought together.
The station has an atmosphere, so ordinary combustion is possible there. However, fire behaves very differently in microgravity. On Earth, a flame rises because heated air is less dense than cooler air; it rises as fresh, oxygen-rich air flows in from below. In microgravity, hot gases do not rise, and oxygen reaches the flame primarily through diffusion—the gradual mixing of molecules. A candle flame becomes nearly spherical, smaller, dimmer, and often blue.
Although a small flame may appear harmless, a fire aboard a space station is among the most dangerous emergency scenarios. Escape to fresh air is impossible from a sealed module, and carbon monoxide and toxic smoke can spread throughout the station through its ventilation system. Accordingly, NASA and other agencies conduct specialized experiments on combustion in microgravity to determine how such fires can be prevented and extinguished.
What would happen to a person without a spacesuit?
Films often portray one of two scenarios: a person in outer space either instantly freezes into a statue or explodes. Neither outcome is likely; however, surviving for an extended period in a vacuum is not possible.
Let us begin with the effects of cold. In a vacuum, there is no air to rapidly draw heat away from the body. The body will lose heat through thermal radiation and the evaporation of moisture, but it will not freeze instantly.
There will be no explosion. The skin and connective tissues are sufficiently strong to keep the body intact. As a result of the sudden pressure drop, gases in the body will begin to expand, and moisture on exposed surfaces — such as saliva on the tongue — may boil even at normal body temperature. Blood in the blood vessels will not boil because it remains under pressure; however, gas and vapor bubbles may form in the tissues, causing them to swell.
The most significant threat is oxygen deprivation. Air is expelled from the lungs, and oxygen levels in the blood decline rapidly. Within approximately 10–20 seconds, a person is likely to lose consciousness as a result of acute hypoxia, or insufficient oxygen reaching the brain. Holding one’s breath in this situation is particularly dangerous: when external air pressure decreases sharply, the air in the lungs expands, potentially causing severe lung injury.
Survival is possible if the person’s blood pressure is restored to normal promptly and oxygen is administered. Within a minute or two, the condition becomes critical, and each additional second spent in a vacuum significantly increases the risk of irreversible injury or death. The reality is more alarming than depicted in films. A person may lose consciousness rapidly and without warning; without immediate assistance, this can result in death.
Is it true that the stars in the sky extinguished long ago?
A widely held belief is both romantic and melancholic: when we gaze at the night sky, we see the light of stars that no longer exist. While this is partly true, the reality is considerably more fascinating.
Light travels at an exceptionally high, yet finite, speed — approximately 300,000 km/s. Consequently, we observe distant objects as they were in the past. We see the Sun as it was approximately eight minutes ago. Light from Proxima Centauri, the nearest star to the Sun, takes about 4.2 years to reach us, while light from Deneb takes more than 2,500 years.
Stars have exceptionally long lifespans. The Sun will remain on the main sequence for approximately 10 billion years, while small red dwarfs can shine for trillions of years — far longer than the universe has existed to date. The few hundred or thousand years that light from most stars visible to the naked eye takes to reach us represents only a small fraction of their age. The claim that most of these stars ceased shining long ago is a popular myth with no scientific basis.
In this respect, a telescope functions as a kind of time machine: the farther into space we observe, the earlier stages of the universe’s history we see. The phrase “we see a star as it was a thousand years ago” is a convenient popular-science simplification. According to the special theory of relativity, the simultaneity of distant events depends on the reference frame and the method used to synchronize clocks; this is a fundamental property of spacetime. The night sky reveals the past, and the vast majority of the stars we observe are still alive.
Does the asteroid belt resemble a scene from “Star Wars”?
Anyone who has seen “Star Wars” may recall a spacecraft racing at breakneck speed through a dense asteroid field while evading enormous boulders. Although spectacular, this scene bears little resemblance to reality.
The main asteroid belt lies between the orbits of Mars and Jupiter, approximately 300 to 500 million kilometers from the Sun. It contains millions of objects, ranging from tiny fragments to bodies hundreds of kilometers in diameter. To provide perspective, the region in which these objects are dispersed is vast. Even among the larger asteroids, neighboring objects are typically separated by hundreds of thousands or millions of kilometers.
A spacecraft traveling through the asteroid belt would most likely not encounter a single asteroid visible to the naked eye, and its pilot would not need to adjust the controls constantly. A realistic depiction of the scene from “Star Wars” would be uneventful: hours, days, or even weeks of travel, with nothing but emptiness visible through the porthole.
How the Sun heats us through a vacuum
Heat is transferred in three ways. Thermal conduction can be observed when a metal spoon is placed in hot tea and gradually warms along its length to the handle; energy is transferred through the material via interactions among its particles. Convection occurs in a teapot, where heat is carried by the movement of the water or gas itself. Because a vacuum separates the Sun and Earth, neither of these mechanisms operates across that space.
The third method is radiation. Any object with a temperature above absolute zero emits electromagnetic waves, and the Sun emits them with extraordinary intensity across the visible, infrared, and ultraviolet ranges. Electromagnetic waves do not require a medium; they propagate through a vacuum at the speed of light and travel the distance from the Sun to Earth in approximately eight minutes.
The ground, oceans, plants, and buildings absorb this radiation, converting its energy into the internal energy of matter and thereby heating these materials. The heated surfaces then transfer heat to the atmosphere through thermal conduction and convection. Solar radiation heats only objects that absorb it, while the empty space between them remains unaffected.
What would occur if the Sun were to disappear suddenly?
Consider a purely hypothetical scenario: The Sun neither explodes nor collapses into a black hole; instead, it ceases to exist instantaneously, along with all its mass. Although the laws of physics do not permit this, it serves as a valuable thought experiment.
Light from the Sun takes approximately 8 minutes and 20 seconds to reach Earth, and we would continue to see it in the sky throughout that interval. The same principle applies to gravity. Earth would not perceive the Sun’s disappearance instantaneously, nor would it fly away at that moment, because changes in the gravitational field also propagate at the speed of light. This is one of the fundamental conclusions of Einstein’s general theory of relativity. Mass and energy warp spacetime, and other bodies move in accordance with its geometry. When the distribution of mass changes, information about that change cannot travel faster than light.
For the first eight minutes or so, nothing unusual would occur on Earth: the Sun would continue to shine, and the planet would follow its usual orbit. Only after 8 minutes and 20 seconds would the final wave of light and information about the change in the gravitational field reach us. The Sun would disappear from view, and Earth would move away in an approximately straight line, tangent to its former orbit, at a speed of about 30 km/s. Its subsequent trajectory would be influenced by the gravitational pull of other celestial bodies. There is no instantaneous communication in the universe, including through gravity; even the geometry of spacetime requires time for light to travel.
Could a black hole consume the Earth?
In science fiction, black holes are frequently portrayed as cosmic vacuum cleaners that consume stars, planets, and even entire galaxies. It is sometimes claimed that a black hole could devour the entire universe. In reality, its gravity follows the same laws as that of any other massive object.
Let us consider a hypothetical scenario in which the Sun is replaced by a black hole of exactly the same mass. From the perspective of orbital motion, almost nothing would change. Earth, Mercury, Venus, Mars, and the other planets would continue to follow nearly the same orbits, because at large distances, the gravitational field of a spherically symmetric body is determined by its mass, regardless of whether it is a star or a black hole. Without sunlight and heat, life on Earth would come to an end; however, nothing would be drawn into the black hole. The event horizon of such a black hole — the boundary beyond which even light cannot escape — would have a radius of only about 3 km. The Sun’s entire mass would be contained within an object approximately 6 km in diameter.
A black hole becomes dangerous when an object approaches it too closely. Powerful tidal forces arise in this region: gravity pulls the nearer part of an object noticeably more strongly than the farther part, and, in extreme cases, the object is literally torn apart. Scientists jokingly refer to this process as “spaghettification.” Even near a black hole, however, not everything falls into it. Stable orbits exist around black holes, and matter that has not lost sufficient orbital energy and angular momentum can remain in orbit for a very long time.
At the center of the Milky Way is the supermassive black hole Sagittarius A*, with a mass approximately four million times that of the Sun. Stars orbit it, while the Solar System is located at a distance of approximately 26,000 light-years. Black holes do not prey on planets. The danger they pose arises from their enormous mass being compressed into an extremely small volume.
Do individuals truly age more slowly in space?
Yes, this phenomenon has been experimentally confirmed. An astronaut who spends time in orbit returns to Earth slightly younger than someone who remains on Earth throughout that period. More than a century ago, Albert Einstein demonstrated that time does not pass at the same rate for everyone; its passage depends, in particular, on velocity and gravity.
The faster a spacecraft travels relative to Earth, the more slowly time passes aboard it compared with a clock on Earth. The International Space Station (ISS) travels at approximately 28,000 km/h; consequently, clocks aboard the station run slightly slower. A second effect is gravity: the stronger the gravitational field, the more slowly time passes. At the ISS’s altitude, Earth’s gravitational field is slightly weaker, so this effect causes the clocks to run faster. These two effects act in opposite directions, but for the station, velocity is the dominant factor. An astronaut who spends six months aboard the ISS returns a few milliseconds younger than if they had remained on Earth. This difference would not be noticeable in a mirror or in how one feels, but it can be measured with ultra-precise clocks.
At high speeds, the effects become increasingly remarkable. Consider a spacecraft traveling with a constant acceleration equal to Earth’s gravitational acceleration. During the first half of the journey, it accelerates; during the second half, it decelerates at the same rate, arriving at its destination at rest before returning in the same manner. A round trip to Proxima Centauri, 4.2 light-years away, would take approximately 12 years according to observers on Earth, but only about seven years for the crew. An expedition to Betelgeuse, 550 light-years away, would return after 1,104 years by the Earth calendar, while only 24 years would elapse aboard the spacecraft. The Andromeda Galaxy is 2.5 million light-years away; according to the crew’s clock, the round trip would take 57 years, although more than five million years would pass on Earth. Under these conditions, even a journey to another galaxy could theoretically be completed within a single human lifetime.
In a certain sense, travel into the future is real, and the ordinary laws of physics are sufficient to explain it. The astronaut will not perceive the slowdown: his heart will beat as usual, his watch will continue to mark the seconds, and his biological processes will proceed normally. The difference will become apparent only upon his return, when he compares his watch with one on Earth.
Does the Moon have a far side?
The Moon does not have a “dark side.” This misconception arose from confusion between the “far side” and the “dark side.” The Moon consistently presents virtually the same hemisphere toward Earth, which is why the same lunar seas and craters are visible through a telescope. It rotates on its axis approximately once every 27.3 days, and its orbit around Earth takes the same amount of time. This phenomenon is known as synchronous rotation, or tidal locking.
The far side receives just as much sunlight. The Sun illuminates both sides of the Moon in turn, just as it illuminates different parts of Earth as the planet rotates. During a full moon, the hemisphere visible from Earth is almost completely illuminated, while the far side is mostly in darkness. During a new moon, the opposite is true: the side facing Earth is almost unlit, while the far side experiences a true lunar day.
