Why myths about space stick
Space is far away, strange to our everyday experience, and often illustrated with dramatic films and loose analogies. It is easy to pick up half-truths along the way. Here are several common ones, with the more accurate picture.
Myth: The Big Bang was an explosion in space
This is probably the most widespread misconception. The Big Bang model does not describe a bomb going off at one spot in an empty void. It describes the expansion of space itself from a hot, dense state. There was no outside location from which to watch, and no center from which everything flew outward. Every region was part of the early universe, and every region expanded.
A helpful picture is a loaf of raisin bread rising in an oven. Each raisin sees the others moving away, and none is in the middle. The picture is imperfect, because the loaf has an edge and sits in an oven, but it conveys the point that distances grow everywhere. It is also worth noting that the model describes what happened after the earliest moments. It does not explain what, if anything, came before. The Big Bang evidence, such as the faint microwave glow and the measured mix of light elements, supports an expanding, cooling universe, not a blast inside a pre-existing space.
Myth: Galaxies are flying away from us because we are at the center
Following from the above, we are not special, and cosmic expansion looks the same from everywhere. Observers in any galaxy would see distant galaxies receding. The space between galaxies is stretching, and the farther away a galaxy is, the faster the gap grows. Within galaxies and groups, gravity holds things together, so we are not expanding, and neither is the Solar System.
Myth: Seasons happen because Earth is closer to the Sun in summer
Earth’s orbit is only slightly oval, and our planet is actually a little closer to the Sun in early January than in early July. Seasons come from the tilt of Earth’s axis, which changes how directly sunlight strikes each hemisphere and how long the days last. When the Northern Hemisphere is tilted toward the Sun, it has summer while the Southern Hemisphere has winter.
Myth: Black holes suck everything in
Black holes have strong gravity, but they do not behave like cosmic vacuum cleaners. If the Sun were somehow replaced by a black hole of the same mass, Earth’s orbit would not change much, though we would lose sunlight. Gravity depends on mass and distance, not on whether an object is a black hole. Only material that gets close enough to the event horizon is trapped. Many black holes also get no new material for long stretches.
Myth: There is a dark side of the Moon
The Moon is tidally locked, so the same hemisphere always faces Earth. The far side is often called the “dark side”, but it receives sunlight just as the near side does. It is simply the side we never see from Earth. Which parts are lit changes with the Moon’s phase.
Myth: You can hear explosions in space
Sound is a vibration that needs a medium such as air to travel through. Space is close to a vacuum, so sound as we know it does not travel across it. Dramatic space battles in films add sound for effect. Light, radio waves and other electromagnetic signals do cross empty space, which is why we can see stars and communicate with spacecraft.
Myth: Astronauts float because there is no gravity in orbit
Gravity at the altitude of a typical low orbit is still strong, only a little less than at the surface. Astronauts float because they and their spacecraft are in continuous free fall around the Earth. They keep missing the ground because they are moving sideways very fast. That is why the sensation is called weightlessness or microgravity.
Myth: The asteroid belt is a dense field of rocks
In movies, the asteroid belt is a hazardous maze. In reality, the objects are spread across such an enormous region that spacecraft have crossed it without any special difficulty. The total mass is also much smaller than that of the Moon. Neighboring asteroids are typically very far apart.
Myth: Dark matter and dark energy mean science is just guessing
Sometimes people point to these unexplained components as a sign that cosmology is broken. A more careful view is that scientists have measured effects they cannot yet explain and have given them placeholder names. Admitting an unsolved problem is part of how science works, and it does not undo the large body of observations that is well supported.
How to spot a space myth
A few habits help. Be careful with analogies, since each is partial. Be cautious about claims that begin “scientists say” without naming what was measured. And treat statements that sound too dramatic with a bit of suspicion. When in doubt, check against several reputable sources, and be comfortable with answers that include “we do not know yet”.