Final answer:
Based on our current understanding of physics, we can understand the conditions that prevailed in the early universe as far back in time as the Planck time, which is approximately 10-43 second after the Big Bang.
Step-by-step explanation:
According to our current understanding of physics, we can understand the conditions that prevailed in the early universe as far back in time as the Planck time, which is approximately 10-43 second after the Big Bang. At this time, the universe was unimaginably hot and dense, and quantum effects of gravity dominated physical interactions. Theorists believe that inflation occurred somewhat later, between 10-35 and 10-33 second after the Big Bang, when the universe was between 1027 to 1028 K in temperature. During this period, the electromagnetic, strong, and weak forces were unified, and Grand Unified Theories (GUTs) are applicable.