First, we would expect to see such matter production occuring today, not just in the past.
Second, and much more conclusively, we have specific predictions from Big Bang Nucleosynthesis (which was just 20 minutes after the big bang, when the entire universe was as hot and dense as the interior of a star) that match up to observations today with exquisite detail. BBN is perhaps the most stunning underappreciated fact about our world, even amongst physicists.
Second, and much more conclusively, we have specific predictions from Big Bang Nucleosynthesis (which was just 20 minutes after the big bang, when the entire universe was as hot and dense as the interior of a star) that match up to observations today with exquisite detail. BBN is perhaps the most stunning underappreciated fact about our world, even amongst physicists.