The 4th episode of COSMOS had a good number of quotable/tweetable takeaways, including ones that address the creationist belief that the universe is ~7,000 years old. Why is COSMOS even talking about non-science based beliefs about the age of our universe? Because unfortunately, 46% of Americans believe in the creationist view that God created humans in their present form within the last 10,000 years. Forty-six freaking percent. Almost half of America does not believe in evolution and has no idea how old the universe is. This is significantly higher than most parts of the world, which is why some viewers were confused as to why NDT would even address it on a science show.
NDT crushes this creationist belief with one short point, but we’ll get to that. First, we have to talk about the speed of light. NDT begins the show by using the speed of light to describe why the night sky is essentially “a sky full of ghosts.”
1. A Sky Full of Ghosts
Light travels 300,000 km per second. That is incredibly fast – but not infinitely fast. It takes time for light from far away sources to reach our eyes. In fact, it actually takes the light reflecting off of the moon about 1 second to reach our eyes (i.e. it is 1 light-second away). That means every time you look at the moon, you are seeing 1 second into the past. Similarly, the Sun, is 8 light-minutes away.
This same concept applies to the stars we see in the sky. The light from some stars takes decades to reach us. Some stars are so far away that it takes many thousands of years for their light to reach us. That means that many of the stars we see in the night sky have already “died.” We see their light in the sky, but their bodies have been gone for many years. This is what NDT means when he refers to a “Sky Full of Ghosts.” Based on this, he says that “a telescope is a time machine.”
2. “To believe in a universe as young as 6,000 or 7,000 years old is to extinguish the light from most of the galaxy”
NDT offers one simple explanation as to why the universe MUST be much, much older than 7,000 years. If the universe were as young at 7,000 years old, we would not be able to see the light from stars farther than 7,000 light-years away. There simply would not have been enough time for their light to reach us! He uses the image above to show a 7,000 light-year radius of a creationist's “viewable universe,” with the Earth at the center. And that’s just in our own personal Milky Way Galaxy. This doesn’t even include the light that we can, in fact, see from the other ~100 billion galaxies in our actual observable universe.
So essentially, if creationism were true, we would not be able to see most of the stars and galaxies we can most definitely see. Sorry, Ken Ham. The universe is much grander and more complex than you would lead people to believe.
3. “Black holes may very well be tunnels through the universe”
Lastly, NDT touches on the concept of black holes. I’m not going to pretend to understand black holes. Not in the slightest. But in this fourth episode, NDT took us on a ride through one. It's a bit trippy so you should definitely check it out.
One of the mind boggling theories that NDT offers up is that “if you were able to survive a black hole, you might find yourself in a different universe altogether. And that universe could have other black holes which could give rise to other universes.” This may be how our universe came to be. In fact, our universe itself might be inside of a black hole. He says, "If you want to know what being inside of a black hole is like, just look around you."
So let that roll around in your mind for a while without it exploding.