# Is it possible to understand inflation through Einstein?

• Stoney Pete
In summary, the conversation discusses the topic of Leibniz's question "Why is there something rather than nothing?" and the inflationary theory proposed by Guth as a potential explanation for the origin of the universe. The speaker mentions that they are writing a philosophical article and thus cannot delve into technical details, but they are struggling to understand how the inflation process involves an increase of negative gravitational energy and positive energy while maintaining a zero overall energy level. They propose an interpretation of gravity as representing negative energy, but not all physicists agree with this.

#### Stoney Pete

Hi guys,

I am writing a philosophical article about Leibniz's famous question "Why is there something rather than nothing?" and in this context I also discuss scientific theories about the origin of the universe, among these the inflationary theory proposed by Guth. Now since it is going to be a philosophical article, I can't discuss these theories in full technical details (which are over my head anyway, since I am not in the least bit mathematically gifted). This approach works fine for most of the theories I intend to discuss but I am having some special problems with the inflationary theory. I'm trying to understand how the inflation process involves an increase of negative gravitational energy and positive energy with the overall energy level remaining zero. I thought that maybe I could use Einstein's general theory of relativity to clarify this, namely as follows:

On Einstein's general theory of relativity, gravity just is the curvature of space. But gravity also represents negative energy as opposed to the positive energy represented by matter. The process of the inflationary expansion of space, therefore, can also be seen as a process in which the negative energy of gravity increases exponentially. But how is this possible, given the law of energy conservation? This is possible because of the mutual cancellation of positive and negative energy. One form of energy can increase arbitrarily only as long as the opposite form of energy increases with the same amount, so that the total amount of energy remains constant. This is precisely what happened during inflation: the exponential increase of the negative energy of gravity/space went hand in hand with an equal increase of positive energy. Out of this positive energy then emerged matter and antimatter through quantum fluctuations. Thus as Hawking writes about the inflation process: "when the universe doubles in size, the positive matter energy and the negative gravitational energy both double, so the total energy remains zero. During the inflationary phase, the universe increases its size by a large amount. Thus the total amount of energy available to make particles becomes very large." (Hawking, A Brief History of Time, p.147)

Now my question to you is: Does this interpretation of inflation by way of the idea that space=gravity=negative energy make sense or is it total bollocks?

The interpretation of gravity as representing "negative energy" (more precisely, that the gravitational potential energy of the universe is negative and exactly balances the positive energy due to matter and radiation) does make sense, in the sense that there is a way to interpret GR's description of the universe so that the total energy of the universe is exactly zero. However, not all physicists agree with this interpretation. An article describing the "gravity is negative energy" interpretation is here. An article describing an opposing interpretation--that energy is simply not conserved in GR in a non-stationary spacetime, such as our expanding universe--is here.

bapowell

## 1. What is the theory of inflation?

The theory of inflation is a cosmological model that explains the rapid expansion of the early universe. It suggests that in the first fractions of a second after the Big Bang, the universe underwent a period of exponential expansion, causing it to grow from the size of an atom to the size of a basketball in a fraction of a second.

## 2. How does Einstein's theory of general relativity relate to inflation?

Einstein's theory of general relativity is the foundation for understanding the physics of inflation. It describes how gravity works on a large scale and is essential for understanding the expansion of the universe during the inflationary period.

## 3. What evidence supports the theory of inflation?

There are several key pieces of evidence that support the theory of inflation, including the observation of the cosmic microwave background radiation, the distribution of galaxies in the universe, and the overall structure and uniformity of the universe.

## 4. Can we directly observe the inflationary period?

No, we cannot directly observe the inflationary period as it occurred in the very early stages of the universe, billions of years ago. However, scientists have been able to observe its effects through various measurements and observations of the universe.

## 5. How does understanding inflation help us understand the universe?

Understanding inflation is crucial for understanding the origins and evolution of the universe. It helps explain the large-scale structure of the universe, the distribution of matter and energy, and the existence of galaxies and other cosmic structures. Additionally, it provides insights into the fundamental laws of physics and the nature of the universe itself.