In modern cosmology, the dynamic development of the concept of a multiverse appears as the paradigm of understanding the universe-whole, an entity including both observable and unobservable regions. The multiverse denotes generically the universe-as-a-whole and thus is highly speculative but finds some compelling support. A popular variation, the many worlds of eternal inflation presumes a background universe comprising quantum fields with infinitely many pocket universes.
Pocket universes are vast expanses of space where some initial conditions or even different physical laws are realized, consistent with the enormous variety of possibilities allowed by quantum field theory, high-energy physics, general relativity, quantum gravity, and thermodynamics. Our observable universe is part of one pocket universe; we cannot see its boundaries yet, and it may be well that we are deeply inside of it.
In eternal inflation, the pocket universes are separated by transition regions of high-energy vacuum; it is this that is called a false vacuum. Those transition regions can be smooth or even sharply bounded. Eternal inflation multiverse obeys general relativity and therefore cannot be static but must also have a complex mix of expansion and contraction.
These may be pocket universes where the physical laws differ, as allowed by myriad possibilities from quantum field theory, high-energy physics, and thermodynamics. But if we’re to begin to make sense of the multiverse, some restrictions on those possibilities are needed, otherwise, we run the risk of admitting we have nothing to say about the multiverse.
The multiverse and the pocket universes are mere speculations and may not exist at all, but their concepts have just been indispensable in cosmological discussions of today. By definition, a “universe” normally refers to a structure that encompasses and resembles the observable universe. With that fact in mind, there’s a need for terms like “multiverse” and “pocket universe” when describing the entirety of physical existence.
Gravity wells tend to be more of a relevant concern on a space travel basis. This is because a star or planet takes the space around it and warps it in a dimple-like fashion due to its gravity. Although this is a highly incomplete analogy, generally it refers to referring to the problem of achieving a greater speed than what gravity can pull down. Indeed, while escape velocity diminishes with distance, it never actually reaches zero.
The dominating gravitational pull of our solar system comes from the Sun, where the escape velocity on its surface is approximately 618 kilometers per second. For the inner planets, such as Earth, a much smaller gravity well exists, with substantial energy nevertheless required to overcome Earth’s gravity. For Earth, the escape speed is approximately 11 km/s, and most of that energy is used up during the initial phases.
Saturn’s gravity well, for instance, is only three times deeper than Earth’s. Yet Saturn is roughly a hundred times more massive. That’s because Saturn has low density – the same mass spreads over an unproportionately large volume. The depth to which one can dig into the well of a planet’s gravity depends not on the planet’s mass, but rather on how close one can approach the planet’s center.
Understanding these gravity wells is paramount both in military and exploratory space missions. The quantity of energy to breach Earth’s gravity well is huge, and extra energy should be spent on a mission to counteract that energy coming from the gravitational pull of the Sun. For instance, traveling to Mars requires breaching the Earth and the Sun’s gravity wells, which simply makes space missions energy-intensive and complex.
General context incorporates the multiverse and problems of space exploration into modern cosmology and military strategy. It is clear that as long as we are going to explore the cosmos, these understandings are crucial for future missions and progressions to find out more about the universe.