In space, astronauts and all kinds of objects that are not fixed will float. They are not attracted to the floor like gravity on Earth. In addition, the universe is also “floating” a variety of massive objects, whether they are planets, stars, or galaxies, they seem to be suspended. So, is there no gravity in space? Why on earth not as an object theredown?
In fact, there is a lot of gravity in space, and gravity is everywhere. Indeed, as you move further from the Earth, its gravity will diminish. But its rate of decay is rather slow (compared to nuclear power). Gravity does not completely disappear, gravity is ubiquitous, but sometimes the gravitational effects look different.
When you are very close to another giant celestial body, such as the moon, Mars, or the sun, the gravitational effects of these objects will far exceed the gravitational effects of the Earth. Only then will you ignore the gravity of the earth. Because gravity is everywhere in space, the celestial bodies are always falling: toward the earth, toward the sun, toward the center of the galaxy. Although the celestial bodies are constantly falling, they seem to be ungravitated, but floating in space for two reasons.
First, at Earth’s standards, space is very large and relatively empty. When you jump off a bridge, you know that you are falling, because you feel the air rushing up, seeing the mountains rushing up, the water is approaching quickly, and then you feel like you are slamming into the water.
Because space is relatively empty, when you fall, there is not much air that makes you feel embarrassed, and there is no landmark to indicate that you are moving. Space is vast, you need hours to years to fall from space until you actually hit a planet surface (assuming it’s aligned with the target, it will actually hit), instead of a few seconds from the bridge Jumped up.
Second, gravity is not so obvious in space because celestial bodies tend to orbit around rather than hitting them. Orbital operation means that a celestial body falls to the central celestial body due to gravity and constantly misses it. In contrast, space is so big, planets are so small, it’s actually hard to really hit the planet. Space objects usually surround the planet in a hyperbolic orbit, or slide into orbit around the planet. Therefore, the Mars probe flies to the surface of Mars and requires a very precise calculation by the team of scientists to ensure that the Mars probe will not miss Mars.
Falling around a planet instead of hitting it doesn’t look like the gravity of the earth we are used to, but it is exactly the same fall. Astronauts in Earth orbit did not experience “no gravity.” They experience almost all of the Earth’s gravity, but there is no resistance. This is the so-called “free fall”, which appears to be floating in the falling frame of reference.
Confusingly, scientists call a space orbital environment “microgravity.” What they really mean is “micro acceleration”, which is another term for free fall. This confusing naming rule stems from the fact that the word “gravity” has historically been used to refer to any acceleration, not just gravity. For example, when a modified car reaches 4 g acceleration, the acceleration is caused by the rotating tire at this moment, regardless of gravity.