Final answer:
If the Hubble constant is 35 km/sec per Mpc instead of 70 km/sec per Mpc, the universe's age would be previously thought, approximately 30 billion years. The estimated age of the universe is based on the reciprocal of the Hubble constant, known as the Hubble time.
Step-by-step explanation:
If we discovered tomorrow that the distances we measured to galaxies were incorrect, and that Hubble's constant is 35 km/sec per Mpc instead of 70 km/sec per Mpc, we would conclude that the universe's age is previously thought.
The age of the universe is estimated using the reciprocal of the Hubble constant, known as the Hubble time. With a Hubble constant of 35 km/sec per Mpc, the estimated age would be approximately double the previous estimate. Therefore, the universe's age would be roughly 30 billion years.
It is important to note that there is still some uncertainty in the Hubble constant, with estimates ranging from about 19.9 km/sec per million light-years to 23 km/sec per million light-years. This uncertainty means that the estimated age of the universe is also uncertain by about 5%.