I take the position that the Universe is about 13.8 billion years old and the Earth is about 4.5 billion years old. In my opinion, one of the larger pieces of evidence against a young Earth, is Hubble's Law.
Hubble's law states that galaxies outside of the Local Group are moving away from earth, and the speed at which they are moving away is proportional to the distance they are from Earth.
In a formula Hubble's Law is the following:
Meaning the speed at which a distant galaxy is moving in km/s is equivalent to its distance from earth in megaparsecs (mpc) multiplied by Hubble's Constant, which is about 71.
With this formula we can calculate the age of the earth.
Distance divided by velocity is time. So we now know the age of the universe is equal to the inverse of Hubble's Constant.
Hubble's Constant is in [km/s]/[mpc] so we can plug that in.
There are 3.0857e19 kilometers in a megaparsec.
We can cancel out the kilometers and get the following:
So the universe is 4.3460563e17 seconds old. Which is 13.78 billion years.
So my question to young earth creationists is:
How do you reconcile a belief that the earth is less than 10,000 years old with Hubble's Law?
But, a YEC's response, if I were to guess... would be that the Big Bang never happened. So they simply would not accept such an assumption. And therefore, the tracking-the-calculation-back-to-when-galaxies-were-touching would be irrelevant.
Like taking the speed of someone on an escalator, tracking back their position and saying "10 minutes ago you were in the ground beneath this building!!" To a YEC, it doesn't make sense to make a linear-ish assumption.
The conversation would probably move to trying to prove the big bang then, which I think there is plenty of evidence for.
I think you can reconcile the two things with a version of last Thursdayism. The universe was created 6000 years ago with the stars and galaxies and space expanding at just about their current rates in just about their current positions, where just about means the minor adjustment for 6000 years.
Well, there's a reason last Thursdayism isn't scientificaly accepted. While it's possible, it's also a positive claim that requires the last Thursdayist to meet their burden of proof.
I see the same thing with a univerese "created old" its a positive claim that requires proof and without that, I see no reason to believe it.
It disproves a young earth, but only if we already assume that the big bang is true. If someone would like to contest this I can provide evidence for the big bang theory.
If we assume the big bang is true, an alternative for why we get 13.8 billion years from Hubble's Constant must be presented in order to discount my argument. A universe that's "created old" is a possibiltiy but would need to be proven, which it hasn't been.
Making that distinction, you're totally correct. It disproves a young universe but not a young Earth. If a christian believed in a young Earth but an old universe, like you said I would point to Genesis 1:1. Since it implies the Earth and universe are the same age.
Interesting, so what do you think is a valid argument against, my post? Even if you think there are other things that prove an old universe/Earth. Remember, I've conceded that it a) it assumes the big bang theory to be true and b) says nothing about the age of the Earth. But I currently still do think it can prove the age of the universe to be billions of years old.