This article is taken from Les Indispensables de Sciences et Avenir #209 April/June 2022.
Thomas Lepeltier is a PhD in astrophysics and a researcher in the history and philosophy of science.
Sciences et Avenir: The model for the birth of the universe, known as the Big Bang, is experiencing “stresses” – a euphemism for its flaws. Who are they ?
Thomas Lepeltier: Together with astrophysicist Jean-Marc Bonnet-Bidot, we analyzed about ten such stressful situations, which is preferable to the term “default”, since the latter implies an internal problem. However, it is currently impossible to know whether the anomalies encountered by the Big Bang model are only temporary or, conversely, reflect a fundamental problem. This ranges from mysterious dark matter and dark energy, the nature of which astrophysicists cannot determine or even guarantee the existence of, and which, making up 95% of the energy of the Universe, were necessarily active at its birth, to disagreements over the magnitude of the rate of expansion of space, to the complexity of explaining the imbalance between matter and antimatter when the big bang model predicts equal creation. All these problems may prompt cosmologists not to declare the Standard Model fully established.
This article is taken from Les Indispensables de Sciences et Avenir #209 April/June 2022.
Thomas Lepeltier is a PhD in astrophysics and a researcher in the history and philosophy of science.
Sciences et Avenir: The model for the birth of the universe, known as the Big Bang, is experiencing “stresses” – a euphemism for its flaws. Who are they ?
Thomas Lepeltier: Together with astrophysicist Jean-Marc Bonnet-Bidot, we analyzed about ten such stressful situations, which is preferable to the term “default”, since the latter implies an internal problem. However, it is currently impossible to know whether the anomalies encountered by the Big Bang model are only temporary or, conversely, reflect a fundamental problem. This ranges from mysterious dark matter and dark energy, the nature of which astrophysicists cannot determine or even guarantee the existence of, and which, making up 95% of the energy of the Universe, were necessarily active at its birth, to disagreements over the magnitude of the rate of expansion of space, to the complexity of explaining the imbalance between matter and antimatter when the big bang model predicts equal creation. All these problems may prompt cosmologists not to declare the Standard Model fully established.
You also treat inflation, that phase of exponential expansion that the cosmos knew about 10-36 seconds after the Big Bang, as a theory with no physical basis. What is the problem ?
In our book, we report on a heated debate – little known to the general public – on this subject between specialists, some of whom consider it highly speculative. The problem is simple: while in the standard model of the Big Bang the Universe experienced a phase of huge expansion at the very beginning, the physical mechanism for the occurrence of this phenomenon, called inflation, is based on the existence of a field – the inflaton, the existence of which is far from proven.
Don’t the new theories of quantum gravity predict this?
Loop quantum theory is certainly better at relating what it calls the Big Rebound, the great rebound that replaces the idea of an infinitely dense and hot Big Bang, with the inflationary process. But this theory is far from complete. One could even say that, thanks to its efforts to better explain inflation, quantum loop theory shows that, without a new approach to gravity, it is currently unsatisfactory.
Is the existence of dark matter and dark energy the death knell for the Big Bang theory as it is currently being described?
Impossible to say. Tomorrow we will be able to detect this dark matter and understand where dark energy comes from. In this case, the standard Big Bang model will be strengthened. But since we have been looking for the first in vain for about fifty years, and the second we have been stumbling for more than twenty years, we may ask ourselves whether these difficulties arise from a fundamental problem with this standard model.
What should it be replaced with?
The history of cosmology is full of competing theories. To date, none of them has received the support of most cosmologists. But if inconsistencies in the model persist, it may be necessary to revise these proposals or come up with others. By doing this work, we can radically change our vision of the cosmos.
– Jean-Marc Bonnet Bidault and Thomas Lepeltier, “The Big Bang, a critical history of an idea.folio, 2021
-Thomas Lepeltier, “Does the Universe exist? PPU, 2021