That the Universe was created within a single point in space time.
The Big Crunch hypothesis.
the big bang
Our concept of the "big bang" has no explanation about how or why, but our hypothesis is that there was NOTHING before the Big Bang created the universe.
The Big Bang is a theory in cosmology that explains the origin and evolution of the universe, supported by a significant amount of observational evidence. It is not a hypothesis, as a hypothesis is an initial explanation to be tested and either supported or rejected based on evidence.
The Big Bang Theory - 2007 The Big Bran Hypothesis 1-2 is rated/received certificates of: Argentina:13
The Big Bang Theory - 2007 The Infestation Hypothesis 5-2 is rated/received certificates of: Netherlands:AL
Hubble's red shift observation.
Fred Hoyle was a proponent of the steady-state theory of the universe and was critical of the Big Bang theory. He famously likened the Big Bang theory to a "Big Bang" creation event and continued to advocate for his steady-state theory even after evidence supporting the Big Bang theory emerged.
The Big Bang Theory - 2007 The Alien Parasite Hypothesis 4-10 is rated/received certificates of: Netherlands:AL
The big bang hypothesis is just that, a hypothesis, and a hypothesis based on an extrapolation of an explanation of a Doppler frequency shift that is itself an unable to be proved hypothesis. So asking what went on before the big bang is meaningless and of course unanswerable. Consider this: The expressions, before and after imply the measure of time. Time did not exist before the BB, therefore the question is nonsensical. We can only spreak of 'after' the BB. Not before! Setting aside the issue of evolution and looking just at the Big Bang, the Big Bang created both space and time. It created the fabric we call spacetime in modern physics. It's not like the Big Bang happened in an "empty universe" that was here already with time passing in the void. No, the Big Bang actually "created the space" in which it now expands. And it created the time, too. These ideas are consequences of the Big Bang theory, and it is currently the best scientific way we have to explain the universe, explain how it formed and became what we can see all around us.
Thomas Aquinas was entirely unaware of the big bang hypothesis. Aquinas was a 13th century Sicilian monk, while the big bang concept was first developed in the early 1960s. So, he would not have been able to refute it.
Ironically, the phrase "Big Bang" came from Fred Hoyle, a very outspoken OPPONENT of the hypothesis. Although many people assume he meant it as an insult to the idea, he was very clear he only invented the term to emphasize the difference between that hypothesis and his own, the now-discredited Steady State Hypothesis.