Imagine a survey where you ask “How old is the universe?” as a multiple choice question:
- 1,000’s of years
- 100,000’s of years
- Millions of years
- Billions of years
- Other _______________
What would you expect as a result? Quite a mix?
Well, among scientists this question is essentially settled, as indicated in some Space.com articles.
“How Old is the Universe?” (June 7, 2017) reviews the methods in determining an age. Key concepts are models of stellar evolution and the Big Bang, since scientific estimates of the age of the universe consider its age as the time elapsed since the Big Bang.
The universe cannot be younger than the objects contained inside of it. By determining the ages of the oldest stars, scientists are able to put a limit on the age.
The uncertainty still creates a limit to the age of the universe; it must be at least 11 billion years old. It can be older, but not younger.
The universe we live in is not flat and unchanging, but constantly expanding. If the expansion rate is known, scientists can work backwards to determine the universe’s age, … Thus, finding the expansion rate of the universe — a number known as the Hubble constant — is key.
“Our Expanding Universe: Age, History & Other Facts” (June 16, 2017) summarizes cosmic history since the Big Bang.
The universe is currently estimated at roughly 13.8 billion years old, give or take 130 million years. In comparison, the solar system is only about 4.6 billion years old.
This estimate came from measuring the composition of matter and energy density in the universe. This allowed researchers to compute how fast the universe expanded in the past. With that knowledge, they could turn the clock back and extrapolate when the Big Bang happened. The time between then and now is the age of the universe.
So, as Wiki notes:
What if you don’t agree with this scientific consensus? Are there any implications? Any personal, social, national, or global consequences of other beliefs? Is there impact on public policies, particularly those related to scientific and technological advancement?1
The topic of the age of the Earth will explore such consequences in another post.
 Regarding implications, Carl Sagan wrote:
For me, it is far better to grasp the Universe as it really is than to persist in delusion, however satisfying and reassuring. Which attitude is better geared for our long-term survival? Which gives us more leverage on our future? — Demon-Haunted World: Science as a Candle in the Dark
And as Shawn Otto writes:
The ideological front of the war on science is being waged by religious conservatives in three major battle zones, all of which deal with origins: the nature and age of Earth and the universe, the theory of evolution, and the origin and nature of life and reproduction. Our answers to these three questions lie at the center of physical science, biology, and the health sciences, and of our capacity to make effective policy decisions in education, economic competitiveness, and public health. — Otto, Shawn Lawrence (2016-06-07). The War on Science: Who’s Waging It, Why It Matters, What We Can Do About It (Kindle Locations 4321-4324). Milkweed Editions. Kindle Edition.