Many or perhaps most believe that the Big Bang hypothesis of the origin of the universe from a singularity or a black hole is the only option.
From: What Was Universe Like before Big Bang? | Physics | Sci-News.com
What Was Universe Like before Big Bang?
Although cosmic inflation is well known for resolving some important mysteries about the structure and evolution of the Universe, other very different theories can also explain these mysteries.
In some of these theories, the state of the Universe preceding the Big Bang — the so-called primordial Universe — was contracting instead of expanding, and the Big Bang was thus a part of a Big Bounce.
To help decide between inflation and these other ideas, the issue of falsifiability — that is, whether a theory can be tested to potentially show it is false — has inevitably arisen.
“Falsifiability should be a hallmark of any scientific theory,” Professor Loeb said.
“The current situation for inflation is that it’s such a flexible idea, it cannot be falsified experimentally. No matter what value people measure for some observable attribute, there are always some models of inflation that can explain it.”
Professor Loeb and co-authors applied an idea they call a ‘primordial standard clock’ to the non-inflationary theories, and laid out a method that may be used to falsify inflation experimentally.
In an effort to find some characteristic that can separate inflation from other theories, the researchers began by identifying the defining property of the various theories — the evolution of the size of the primordial Universe.
The signals generated by the primordial standard clock can serve such a purpose. That clock is any type of heavy elementary particle in the primordial Universe. Such particles should exist in any theory and their positions should oscillate at some regular frequency, much like the ticking of a clock’s pendulum.
The primordial Universe was not entirely uniform. There were tiny irregularities in density on minuscule scales that became the seeds of the large-scale structure observed in today’s Universe. This is the primary source of information physicists rely on to learn about what happened before the Big Bang.
The ticks of the standard clock generated signals that were imprinted into the structure of those irregularities.
Standard clocks in different theories of the primordial Universe predict different patterns of signals, because the evolutionary histories of the Universe are different.
The team calculated how these standard clock signals should look in non-inflationary theories, and suggested how they should be searched for in astrophysical observations.
“If a pattern of signals representing a contracting Universe were found, it would falsify the entire inflationary theory,” said co-author Dr. Zhong-Zhi Xianyu, a postdoctoral fellow in the High Energy Theory Group in the Department of Physics at Harvard University.
The success of this idea lies with experimentation.
“These signals will be very subtle to detect and so we may have to search in many different places,” said co-author Dr. Xingang Chen, a senior lecturer at the Harvard-Smithsonian Center for Astrophysics.
“The Cosmic Microwave Background radiation is one such place, and the distribution of galaxies is another.”
“We have already started to search for these signals and there are some interesting candidates already, but we need more data.”
Other scientific proposals concerning a cyclic universe to follow.
From: What Was Universe Like before Big Bang? | Physics | Sci-News.com
What Was Universe Like before Big Bang?
Although cosmic inflation is well known for resolving some important mysteries about the structure and evolution of the Universe, other very different theories can also explain these mysteries.
In some of these theories, the state of the Universe preceding the Big Bang — the so-called primordial Universe — was contracting instead of expanding, and the Big Bang was thus a part of a Big Bounce.
To help decide between inflation and these other ideas, the issue of falsifiability — that is, whether a theory can be tested to potentially show it is false — has inevitably arisen.
“Falsifiability should be a hallmark of any scientific theory,” Professor Loeb said.
“The current situation for inflation is that it’s such a flexible idea, it cannot be falsified experimentally. No matter what value people measure for some observable attribute, there are always some models of inflation that can explain it.”
Professor Loeb and co-authors applied an idea they call a ‘primordial standard clock’ to the non-inflationary theories, and laid out a method that may be used to falsify inflation experimentally.
In an effort to find some characteristic that can separate inflation from other theories, the researchers began by identifying the defining property of the various theories — the evolution of the size of the primordial Universe.
The signals generated by the primordial standard clock can serve such a purpose. That clock is any type of heavy elementary particle in the primordial Universe. Such particles should exist in any theory and their positions should oscillate at some regular frequency, much like the ticking of a clock’s pendulum.
The primordial Universe was not entirely uniform. There were tiny irregularities in density on minuscule scales that became the seeds of the large-scale structure observed in today’s Universe. This is the primary source of information physicists rely on to learn about what happened before the Big Bang.
The ticks of the standard clock generated signals that were imprinted into the structure of those irregularities.
Standard clocks in different theories of the primordial Universe predict different patterns of signals, because the evolutionary histories of the Universe are different.
The team calculated how these standard clock signals should look in non-inflationary theories, and suggested how they should be searched for in astrophysical observations.
“If a pattern of signals representing a contracting Universe were found, it would falsify the entire inflationary theory,” said co-author Dr. Zhong-Zhi Xianyu, a postdoctoral fellow in the High Energy Theory Group in the Department of Physics at Harvard University.
The success of this idea lies with experimentation.
“These signals will be very subtle to detect and so we may have to search in many different places,” said co-author Dr. Xingang Chen, a senior lecturer at the Harvard-Smithsonian Center for Astrophysics.
“The Cosmic Microwave Background radiation is one such place, and the distribution of galaxies is another.”
“We have already started to search for these signals and there are some interesting candidates already, but we need more data.”
Other scientific proposals concerning a cyclic universe to follow.
