Original appeared on January 3, 2007, Latest Revision on August 10, 2019

By Sing H. Lin, Ph.D., E-Mail: SINGHLIN@GMAIL.COM

Abstract

Mysteries in Astronomy: Many astronomers and scientists all over the world have been struggling with the strange and puzzling phenomena of dark energy and dark flow based on astronomical observations. These astronomical observations on the inter-galactic scale have found the following surprising phenomena: (a) the accelerated expansion of universe caused by an unknown mysterious dark energy, (b) several methods have been used by several teams of scientists in last 20 years to measure the expansion rate of the universe. The measured universe’s expansion rate based on physics of the early universe tend to have lower values than those based on the late universe by about 10 %, (c) The universe expansion rate measured by several different methods are not the same, but are different by several percent, and (d) strange huge flow of hundreds of galaxy clusters in certain direction. These strange phenomena imply the existence of huge amount of unknown and mysterious dark energy in the universe, but our scientific knowledge still does not understand that "dark side of the cosmos" well yet. The significant discrepancy in measured expansion rate of our universe is considered by many scientists as a crisis in modern science and may be an indication for the need for new physics.

By using Theory of Parallel Universes, String theory, M-Theory and Big-Bang-Inflation Theory, I propose that the mysterious dark energy that is causing the accelerated expansion of our universe is the inter-universe coupling gravity coming from matters residing in other parallel universes surrounding our universe. In other words, dark energy is inter-universe coupling gravity. This theory, based on the concept of parallel universes and inter-universe coupling gravity, can explain all the four observed surprising phenomena (a), (b), (c) and (d) as related to dark energy and accelerated expansion of universe.

In later years, our universe has expanded to become much larger universe with greater distances among all galaxies in our universe. The dark energy becomes stronger in later years due to two factors: (a) The inward gravity pull among all galaxies in our universe becomes weaker because of the greater distances among galaxies in our larger universe in later years. (b) As our universe become larger, many galaxies in our universe are getting closer to neighboring parallel universes and are experiencing stronger outward gravity pull because of the shorter distance to neighboring parallel universes. With weakening inward gravity pull, and stronger outward gravity pull from other parallel universes, the outward gravity pull becomes the dominant force. Therefore, dark energy becomes stronger in recent 7 or 8 billion years. In this sense, dark energy is NOT constant but is time varying and is increasing with time. Therefore, the 10 % discrepancy in measured expansion rate between measurements based on later years and those based on earlier years of universe is to be expected from my theory and is not a crisis in modern science.

It is wonderful to realize that the Big Bang Inflation Theory is a highly consistent theory that describes not only the beginning of the universe very well, but also predicts the existence of multiverse which logically predicts accurately the accelerated expansion of universe in later years through my theory of inter-universe coupling gravity coming from multiverse. In other words, the Big Bang Inflation Theory describes not only the beginning of the universe very well , but also predicts correctly the entire accelerated expansion process of the universe in the later mature years.

1. Introduction on Issues of Dark Energy

1.1 Discovery of Expanding Universe

In about 1929, Edwin Hubble and several other scientists discovered that the spectral lines in the light received from distance galaxies are all shifted toward red light end of the spectrum. Edwin Hubble further discovered that the amount of red-shift is proportional to the distance of galaxy from us. A red-shift can occur when the light source is moving away from an observer, similar to the Doppler shift that changes the perceived frequency of sound waves. The observed red-shift implies that: (1A) Galaxies are running away from us, (1B) The receding speed of a galaxy is proportional to its distance from us, and (1C) Universe is not static, but is expanding.

1.2. Surprising Discovery of Accelerated Expansion of Universe

Since all matters have gravity pulling on each other, such gravity pull is expected to slow down the expansion of universe. In 1998, two independent teams of scientists did two independent astronomical measurements to try to measure the rate of slowing down of expanding universe (i.e. to measure the ultimate fate of our universe). These two teams are the Supernova Cosmology Project at the Lawrence Berkeley National Laboratory and the High-z Supernova Search Team.

However, these two teams of scientists and the whole world were all surprised in 1998 to find that the expansion of universe is NOT slowing down, but is accelerating. These two independent teams of scientists were scared and thought that they might have some errors in their measurements. But their careful checks found no errors in their two independent sets of measurements. All scientists and astronomers have been in a state of collective bewilderment since this surprising discovery in 1998.

The key question is what is causing such accelerated expansion of universe? For the time being, scientists have to postulate a mysterious “Dark Energy” that is a hypothetical form of energy that permeates all of space and tends to increase the rate of expansion of the universe.

1.3. Dark Energy Acts Only in Grand Scale

Even though many astronomical observations indicate consistently that our universe is expanding and the expansion is accelerating, but the size of our earth orbit around the sun is NOT expanding, the size of solar system is NOT expanding, the size of our Milky Way Galaxy is NOT expanding and the sizes of all galaxies are NOT expanding. It is only the spacing among all galaxies are expanding. In this sense, the dark energy acts only in the grand scale of spacing among all galaxies, but does not expand the size of galaxy, of solar system and of earth orbit.

1.4. Serious Discrepancy in Measured Expansion Rate of Universe

Several different methods have been used by several teams of scientists in last 20 years to measure the Hubble "Constant" which is a proportionality "constant" used to describe the expansion rate of the universe as described here , here and here. But the Hubble Constant measured by these several different methods are not same. Such discrepancy among several sets of measured Hubble Constant is considered by some scientists as a crisis in modern science and may be an indication for the need for new physics.

1.4.1. Expansion Rate based on Physics of Early Universe vs Those Based on the Late Universe

The measured Hubble Constant based on physics of the early universe tend to have lower values than those based on the late universe by about 10 %.

1..4.2. Different Measurement Methods Yield Significant Different Values of Hubble Constant

Some measurement methods of Hubble Constant use the exploding stars, called Type IA supernovae, to serve as "standard candles" for accurate measurement of distance of the exploding star, while some other measurement methods use quasars or red giant stars as the standard candles. The Hubble Constant measured by these different methods differ by several percent. Again, such discrepancy among several sets of measured Hubble Constant is considered by some scientists as a crisis in modern science and may be an indication for the need for new physics.

1.5. Discovery of Huge Dark Flow in the Universe

"Dark Flow" was discovered in 2008 by Alexander “Sasha” Kashlinsky of NASA’s Goddard Space Flight Center. Dark Flow represents the movement of hundreds of galaxy clusters at about two million miles per hour in the direction of a patch of sky between the constellations Centaurus and Vela.

2. Dark Energy is Inter-Universe Coupling Gravity - A New Theory

With the concept of parallel universes and of Big Bang Inflation, our universe is NOT the only universe that is going through the big bang expansion. There are other parallel universes that are out there surrounding our universe. For discussion purpose, let our universe be represented by the Universe A and other parallel universes be represented by Universe B, universe C, universe D, universe E, etc. as illustrated in the following Figure 1.

Figure 1 - Concept of Parallel Universes with Inter-Universe Coupling Gravity among our universe and many other parallel universes surrounding our universe.

In this way, the matters in other parallel universes are exerting their inter-universe coupling gravity to pull outward on all matters in our Universe A. In other words, the inter-universe coupling gravity from other parallel Universes is causing accelerated expansion of our Universe A.

Based on concept in Figure 1, I , therefore, propose that dark energy is just the plain old gravity, in the format of inter-universe coupling gravity.

The background supporting information on multiverse, parallel universes and Big Bang Inflation Theory are in Appendix A.

3. Implication of the Observation Fact that Dark Energy Acts only in Grand Scale

The implication of the observation fact that dark energy acts only in grand scale is that dark energy is NOT an intrinsic property of space because dark energy does not expand the space of earth orbit, does not expand the space of solar system and does not expand the space of any galaxy. This observation fact is consistent with the theory that dark energy is inter-universe coupling gravity coming from many other parallel universes outside of our universe. This outward inter-universe coupling gravity pull everything in our universe to fly outward to expand our universe. This inter-universe coupling gravity pulls our entire solar system including the sun, the earth and all planets together to fly outward from the center of our universe. But this inter-universe coupling gravity does not pull the earth to go away from our sun, does not pull any other planets to go away from the sun.

Therefore, this theory of inter-universe coupling gravity for dark energy is consistent with the observation fact that (3A) dark energy acts only in the grand scale and (3B) dark energy is NOT intrinsic to the empty space to expand all empty space.

4. Explanation for the Serious Discrepancy in Measured Expansion Rate of Universe

4.1. Expansion Rate Based on Physics of Early Universe vs Those Based on Late Universe

In early years of universe, the universe was smaller. The matters and galaxies in early universe were more crowed in the smaller earlier universe. Therefore, the inward gravity pulls among all matters and all galaxies in our universe were stronger in those early years of smaller universe with shorter distances among all the galaxies in our universe. Such stronger inward gravity pull inside our smaller and earlier universe acts against the outward gravity pulls from those matters in other parallel universes. With such strong inward gravity pull, the dark energy appears to be weaker in earlier years of our smaller universe, and hence, smaller value of universe expansion rate based on the physics of earlier universe.

However, in late years, our universe has expanded to become much larger universe with greater distances among all galaxies in our universe. The dark energy becomes stronger in late years due to two factors: (4.1.A) The inward gravity pull among all galaxies in our universe becomes weaker because of the greater distances among galaxies in our larger universe. (4.1.B) As our universe become larger, many galaxies in our universe are getting closer to neighboring parallel universes and are experiencing stronger outward gravity pull because of the shorter distance to neighboring parallel universes. With weakening inward gravity pull, and stronger outward gravity pull from other parallel universes, the outward gravity pull becomes the dominant force. Therefore, dark energy becomes stronger in recent 7 or 8 billion years. In this sense, dark energy is NOT constant but is time varying, and is increasing with time. This is consistent with the experimental finding that (4.1.C) the expansion of our universe is accelerating and (4.1.D) The measured expanding rates of our universe in late years are greater than those based on earlier physics of our baby universe. .

Such difference in measured Hubble Constant based on physics of early universe vs those based on later years implies that Hubble "Constant" is not a constant but is increasing with time and that dark energy is not constant, but is also increasing with time.

4.2. Reason for Observed Dark Flow

There is no reason that the distribution of other parallel universes must be perfectly symmetrical with respect to our observation position on earth in our Universe A. Then the inter-universe coupling gravity from all those parallel universes on our Universe A is not perfectly symmetrical with respect to our observation position on earth. Therefore, the accelerated expansion of our Universe A is not perfectly symmetrical to our position on earth, not perfectly uniform in all of our observation angles, and not perfectly homogeneous at all positions in our universe. This may be the reason for the "Dark Flow" discovered in 2008 by Alexander “Sasha” Kashlinsky of NASA’s Goddard Space Flight Center. Dark Flow represents the movement of hundreds of galaxy clusters at about two million miles per hour in the direction of a patch of sky between the constellations Centaurus and Vela. Such observed dark flow is a proof that the expansion of our universe is NOT uniform in all observation angles as observed from earth.

Since the inter-universe coupling gravity between Universe A and other parallel universes is not perfectly symmetrical, the shapes of our Universe A and of other parallel universes may not be perfectly spherical either.

Therefore, Hubble "Constant" representing the expansion rate of our universe is not a constant, but varies with our observation angle as viewed from earth.

4.3. Reason for Different Values of Universe Expansion Rate Measured by Different Methods

Some measurement methods of expansion rate of our universe use the exploding stars called Type IA supernovae, to serve as "standard candles" for accurate measurement of distance of the exploding star, while some other measurement methods use quasars or red giant stars as the standard candles. Since the observation angles of Type 1A supernovae are different from those of quasars or red giant stars, the expansion rate of universe may be slightly different at these different observation angles. Therefore, a few percent difference in measured expansion rates by these different measurement methods are to be expected because the expansion rate of universe is NOT uniform in all observation angles as explained in Section 4.2.

5. Concluding Remark

The String Theory, M-Theory and Theory of Parallel Universe indicate that gravity can "leak" from one universe into other parallel universes. Therefore, parallel universes are not totally independent of each other, but are coupled to each other through such inter-universe coupling gravity. The accelerated expansion of our universe is caused by such inter-universe coupling gravity coming from other parallel universes. The Dark Flow detected in our universe is also caused by such inter-universe coupling gravity.

Since the sources of this inter-universe coupling gravity are matters residing in other parallel universes, we cannot see and cannot touch those matters in other parallel universes. Therefore, the effects of this inter-universe coupling gravity show up in our universe as very strange phenomena, namely: (5-1) accelerated expansion of our universe by strange unknown dark energy, and (5-2) Dark Flow of hundreds of galaxy clusters in certain direction.

It turns out that these major mysteries and crisis at the frontier of modern physics and astronomy are all caused by the same plain old gravity - in the format of inter-universe coupling gravity.

The consistency of the predictions from this theory with the observed behavior of dark energy and of accelerated expansion of universe may be considered as additional evidence for the existence of multiverse and of big bang inflation theory.

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Appendix A - Supporting Information on Multiverse, Parallel Universe and Big Bang Inflation Theory

Several aspects at the cutting edge of science are relevant and important to the understanding of dark energy, accelerated expansion of our universe and dark flow. They include String Theory, M-Theory, Multiverse (or Parallel Universe) and Big Bang Inflation Theory. They are driven by several surprising and uncomfortable discoveries from astronomy scale and from sub-atomic scale of quantum physics (i.e., from very large scale and from very small scale). For almost a hundred years science has been haunted by a dark secret: that there might be mysterious hidden worlds beyond our human senses. Recent advances in investigations and studies of these strange discoveries by many scientists are all pointing consistently to the possible existence of parallel universes (multiverse) and to the development of String Theory, M-Theory and Big Bang Inflation Theory.

According to Professor Alan Guth in MIT and Professor Andrei Linde in Stanford University, the two main contributors to the inflation theory, inflation, once started, is eternal in the sense that it created not only our universe, the rest of the cosmos will continue blowing up, spinning off other bubbles endlessly, a concept known as the Multiverse with many parallel universes. In other words, our universe is one of many inflationary universes in a vast Multiverse.

A.1. Some Key Characteristics of Parallel Universes

The following team of leading scientists and professors in physics and astronomy in prestigious universities jointly provides detailed in-depth explanations of this cutting-edge field of research on parallel universes, String-Theory and M-Theory in a series of documentary TV programs which are often shown on educational TV channels such as Science Channel or History Channel:

NIMA ARKANI-HAMED, Professor of Physics, Harvard University,

MICHAEL DUFF, Professor of Physics, University of Michigan, and Imperial College (London),

ALEX FILIPPENKO, Professor of Astronomy, University of California, Berkeley

ALAN GUTH, Professor of Physics, Massachusetts Institute of Technology,

MICHIO KAKU, Professor of Theoretical Physics at the City University of New York

BURT OVRUT, Professor of Physics, University of Pennsylvania,

LISA RANDALL, Professor of Physics, Harvard University,

PAUL STEINHARDT, Professor of Physics, Princeton University,

NEIL TUROK, Professor of Mathematical Physics, Cambridge University

The transcript of this series of video programs on Parallel Universes is also available at:

http://www.bbc.co.uk/science/horizon/2001/parallelunitrans.shtml

These science documentary TV programs are very helpful and educational to many people, including me. According to the preliminary theory of parallel universes as explained by this team of scientists, there are many, infinitely many, universes that exist in parallel to our known universe, we are not alone!

A.2. Gravity Coupling Among Parallel Universes

According to the String Theory, most forces are based on open strings that are attached to a brane (i.e., a universe) such that most forces are confined within their own universe. But gravity is different and is based on a closed-loop string that is not attached to a given brane. The close-loop string based gravity can float from one brane to another brane such that gravity can "leak" from one universe into other parallel universes

Since gravity can leak from one universe into other parallel universes, it means that the parallel universes are not totally independent of each other, but are coupled through gravity. I, therefore, propose that:

(A.2.1.) the inter-universe coupling gravity is the dark energy that is causing accelerated expansion of our universe as explained in Section 2,

(A.2.2.) the inter-universe coupling gravity is causing the Dark Flow in our universe as explained in Section 4.2.

The effects of this inter-universe coupling gravity show up in our universe as very strange gravity phenomena and gravity mysteries because their sources in other parallel universes cannot be seen and cannot be touched from our universe.

A.3. Signatures of Collision of our universe with other universes

In studying Cosmic Microwave Background (CMB), a team of scientists have identified disc shaped signatures on CMB as preliminary evidences of collisions of our universe with other parallel universes in the past. Some descriptions of this discovery of collision signatures are in the following websites:

http://www.messagetoeagle.com/evidencepararelluniverse.php#.U01U8lVdV8G

http://www.preposterousuniverse.com/blog/2010/12/22/observing-the-multiverse-guest-post/

A.4. 1998 Discovery of Accelerated Expansion of Our Universe

A brief description of the surprising 1998 discovery accelerated expansion of our universe is in Section 1.2. of this web page. According to my theory in Section 2, such accelerated expansion of our universe is due to inter-universe coupling gravity from other parallel universes surrounding our universe. In other words, the mysterious dark energy is inter-universe coupling gravity coming from other parallel universes surrounding our universe. Therefore, the surprising discovery in 1998 of accelerated expansion of our universe can be considered as a strong hint for the existence of parallel universes.

A.5. Discovery of Huge Dark Flow in 2008 by Alexander “Sasha” Kashlinsky of NASA’s Goddard Space Flight Center

"Dark Flow" was discovered in 2008 by Alexander “Sasha” Kashlinsky of NASA’s Goddard Space Flight Center. Dark Flow represents the movement of hundreds of galaxy clusters at about two million miles per hour in the direction of a patch of sky between the constellations Centaurus and Vela. According to my theory in Section 2, this dark flow is due to the inter-universe coupling gravity coming from the asymmetrical distribution of parallel universes surrounding our universe as explained in Section 4.2. Therefore, the discovery of dark flow can be considered as a hint for the existence of parallel universes.

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The index of websites of Dr. Sing H. Lin's research on science including dark matter, dark energy, Gravity Hills and Mystery Spots is at:

• Index of Websites of Dr. Sing H. Lin's Research on Science

Biography of Dr. Sing H. Lin is at:

• Biography of Dr. Sing H. Lin