You throw a rock straight up into the air. Assuming you don't throw it too hard, it will rise for a while, but eventually the acceleration due to the planet's gravity will make it start to fall down again. If you threw the rock hard enough, though, you could make it escape the planet's gravity entirely. It would keep on rising forever. The speed with which you need to throw the rock in order that it just barely escapes the planet's gravity is called the "escape velocity."
The process can take place in normal or reduced gravity. To understand how acoustic levitation works, you first need to know a little about gravity, air and sound. First, gravity is a force that causes objects to attract one another. The more massive an object is, the more strongly it attracts other objects. The closer objects are, the more strongly they attract each other.. Scientists haven't decided exactly what causes this attraction, but they believe it exists everywhere in the universe.
The two most common factors which have a direct effect upon the amount of air resistance are: - the speed of the object - the cross-sectional area of the object Increased speeds and increased cross-sectional areas result in an increased amount of air resistance. Gravity is what causes objects to fall downwards. If there was no air resistance, all falling objects would accelerate at 10m/s/s (10m/s²) because there would be no other force to change the speed. Acceleration is the rate at which the velocity of an object changes over a period of time. It is measured in m/s², and it tells you how much the velocity will change each second.
The more matter an object has, the stronger its gravitational pull. For example, when you are walking on earth its pulling you and you’re pulling back. However, the earth has significantly more mass than you so your gravitational pull is not strong enough to move the planet. Furthermore, the distance between two objects is a major factor in their gravitational pull on each other. The farther away an object is, the less force it has on another object.
Gravity is the force that pulls two objects together, and the mass of the human body depends on gravity. The more the mass there is, the amount of the gravitational force will increase. The study of the Earth’s gravitational field itself is complex and deeply fascinating. Likewise, studying its relation to the human body makes it even more thought provoking. A gravitational field is simply the area of space neighboring a body that has another body experiencing a gravitational attraction force.
The speed at which the rock will leave a gravitational pull of a planet is called the “escape velocity”. The escape velocity differs on the planet’s mass; the more mass the planet has – the higher escape velocity will be. A black hole has so much mass concentrated in a small radius that its escape velocity is greater than the velocity of light (Bunn). Since it is impossible for anything to travel faster than light, it means that nothing can escape a black hole (Gribbin and White 75). Black holes may form after a star is overwhelmed by its gravitational force, that it can’t keep from collapsing.
Without gravity, there would be no space and time. There is a legend that says that Galileo once dropped two objects off the Leaning Tower of Pisa to show that the heavier of the two objects dropped faster. If a feather and hammer were the two objects he used then obviously the hammer would hit the ground first. This is due to air resistance, which is the force air exerts on a moving object. This force acts in the opposite direction to that of the object's motion.
In a like manner, smoke rose into the sky because it wanted to be closer to the air and farther away from the Earth. In observing this, Aristotle concluded that natural motion came from the tendency of objects to return to their “natural” place and come to rest. He decided that objects intrinsically have either the natural tendency to fall to the earth, which he termed gravity, or the tendency to rise into the sky, which he called levity. Aristotle also believed that heavier objects fell faster than smaller objects because falling speed is proportional to the weight of the object. The bigger the mass, the more intrinsic natural tendency the object contained that would draw it back to the surface of the Earth.
According to relativity, space is malleable, which is how the FTL drive achieves this feat. The early universe, for example, expanded faster than the speed of light because space time itself can expand faster, even though objects within space time cannot accelerate faster. In this scenario, the ship containing the FTL drive actually sits still and is carried along the warp bubble, kind of like a surfboard riding on an expanding wave. This means that time dilation and other relativistic effects are not significant, despite the intense speed. In summary, I believe that in the future we will travel the stars just like how today airplanes travel the skies.
This is called a flat Universe. The third option has almost been ruled out, but there is always a possibility. If the universe is denser than we think, gravity will eventually become stronger than the expansion, perhaps resulting in the universe collapsing in on itself in a ?Big Crunch?. We may not know where our Universe is heading, but the Big Bang theory helps us understand where we have come from. Although there are still many unanswered questions, there is plenty of time left in this young Universe, and plenty of places to explore.