Stephen Hawking’s favorite idea is that the universe is created from nothing. That it originated as a quantum oscillation with literally no pre-existing state; no space, no time, nothing. Creation from scratch is sustainable with a zero-energy universe. The zero-energy universe hypothesis assumes that the total energy in the universe is zero and is the only universe that can come out of nothing. There is another idea in science about the creation of the universe; that the universe came from something, but that something was simply chaos, with space, time, and energy, but no order; an empty space with vacuum energy.
From chaos or nothing, entities have been created from which our observable universe is built. An entity is something that has an existence. An observation is processed by man through the neural processes in the nerves. We only perceive something when our brains can process its existence. An object does not need to be physically perceived to exist; if it is mentally perceived, it also exists. Mental objects are ideas, memories, imaginations or representations. Mental objects, however, do not exist physically and are a subjective experience of reality, created by the interpretation of sensory perceptions and representations of a human being. For example, memories are not completely true to objective events, but merely a representation of what is experienced and colored by your own experience.
For the interpretation of the awareness of physical systems, a connection between the brain and the quantitative concept is required to be able to express or measure physical systems. To make this possible, Galileo Galilei (1564-1642) introduced mathematics in science. A mathematical formula must describe a peculiarity of nature and strives to minimalize uncertainties. Albert Einstein’s (1979-1955) theory of relativity describes reality according to the findings in physics. The relativity theory of Einstein is therefore mathematically expressed in the Einstein equation.
Our universe consists of observable entities. Examples are; space, time, matter, energy, gravity, etc. These entities mean something to us because we experience them and we have conceptualized them. The meaning of these entities has been given by yourself or by information from others, via, for example, publications from science, from the media or from people from your immediate environment. Space and time have units that can be measured in a dimension. Space-time, as defined by Einstein, has four dimensions (three spatial dimensions and one-time dimension). In space-time, where our reality consists of, time can not be separated from space. The four dimensions are interdependent and make up the space-time.
The image above shows the four-dimensional space-time continuum we are in, seen from time. In the image, you can see that space and time maintain each other. Without space, there would be no time and vice versa. The past, the present and the future are all in the same space, that is why it is a continuum. There can only be one phenomenon at one point in space-time, that is; every point in space-time is unique. The past and the future are only at another point in the space-time continuum, you can, therefore, only be in the present.
Einstein has shown in his theory of relativity that matter causes gravity and that the mass of this matter determines gravity. The greater the mass, the stronger is its gravity. Mass causes space-time to curve, this bending of space-time is gravity. To make this understandable an example with a bowling ball is used. Imagine putting a bowling ball on a trampoline; the trampoline will bend through the mass of the bowling ball. The image below gives an impression of what this would look like.
Suppose you are putting a tennis ball next to the bowling ball, then you will see that the tennis ball rolls to the bowling ball. This is due to the gravity caused by the bending of the trampoline because of the mass of the bowling ball. This was a simplified example in two dimensions. The image below shows how you can imagine one planet in a three-dimensional space where we leave out the dimension of time for convenience.
Now you can see that the mass of the planet is pulling the space around itself. The greater the mass of matter, the greater the bending of space-time, and the greater its gravity. This same principle applies to all matter in the universe.
Mass is solidified energy and is a property of matter. Energy is measured in Joules and consists of; radiation, kinetic energy, electromagnetic energy, nuclear energy, heat, chemical energy, electrical energy, magnetic energy, elastic energy, sound energy (waves) and mass. Einstein concluded that mass equals energy in the well-known formula E = mc². With E as the total energy, m stands for the mass in kilograms and c represents the speed of light in meters per second. This means that energy is equated with mass and vice versa. A small amount of mass equates to a very large amount of energy.
The above variants of energy are regarded by scientists as positive energy. The zero-energy universe hypothesis assumes that an equal amount of potential negative energy is present in the attraction that exists between all positive energy particles. Stephen Hawking (2002) writes in his book ‘The Theory of Everything’ about negative energy, that two particles of matter that are close to each other have less positive energy than the same two particles that are far away from each other. Since you need positive energy to remove the two particles from each other, the energy of the gravity that keeps the particles together is negative.
Let’s look at an example based on two magnets to illustrate the above. To keep the explanation understandable, magnetic attraction and gravity are equated in this example. When two magnets get close enough to each other, they are pulled together through the bending of space-time. To remove them again, a certain amount of energy is needed, for example by moving your arms and hands. If you have to add energy to remove the magnets from each other, the gravity of the magnets must have negative energy because the two magnets have not changed when they are divided again. The amount of positive energy you need to pull them apart is proportional to the amount of negative energy that keeps the magnets together.
Since the gravity of matter is determined by the mass of matter, the potential negative energy of gravity cancels the positive energy of all matter. This phenomenon applies to all particles in the universe and therefore, according to the zero-energy universe hypothesis, the total amount of energy in the universe equals zero.
 . Lincoln, M.; Wasser, A. (2013). “Spontaneous creation of the Universe Ex Nihilo”. Physics of the Dark Universe. 2 (4): 195.
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 . https://www.livescience.com/33129-total-energy-universe-zero.html