Russell Humphreys' cosmology (Starlight and Time) has arguably received the most attention in the last decade (although he has revised his model over the years). It is even highlighted in some of the curricula I have reviewed including, Jeannie Fulbright's Exploring Creation with Astronomy, Apologia, and Sonlight (I think).
More recently, Australian physicist, John Hartnett, has put forth an alternative cosmological model. Hugh Ross and Jeff Zweerink read Hartnett's book (Starlight, Time, and the New Physics) recently and then interviewed him in an effort to try and understand his model (largely because we keep getting questions about it).
"SPECIAL EDITION - Podcast: Interview with physicist John Hartnett"
I listened to the entire interview today. Now, I'm going to warn you, it gets somewhat technical at points and there are some aspects of Hartnett's model that I honestly don't understand. (For example, he makes an appeal to a fifth dimension, but I'm not sure what it is or how it functions.) Be that as it may, I did find listening to this to be a valuable exercise because it really highlights the bind that knowledgeable and honest young-earth creationists are finding themselves in and the rather unusual gymnastics they have to go through to appeal to unconventional, unproven, and possibly even untestable cosmological models.
One of the more telling moments in the interview is when Hugh asked Hartnett about the Oort Cloud.
HR: What about the Oort Cloud? Where do you place that?This is a great example of (what I consider to be) the kind of hand-waving that young-earth creationists engage in on a regular basis. If a body of evidence doesn't fit their model, they just assert that it "doesn't exist" because their model has "no need of it."
JH: The Oort Cloud?
JH: Well, it doesn't exist.
HR: So you don't think the Oort Cloud exists?
JH: Well, I-I don't see any need for it.
I also found it interesting that Hartnett believes Humphreys' model has "problems" and "deficits." Hugh and Jeff attempted several times to try and clarify the ways in which the two models are similar and different, which was very helpful (even if I didn't understand all of it).
HR: One reason we're asking all these questions, John, is the question we get a lot is, how does your model, your cosmological model, differ from the model of Russ Humphreys? So that's why we're trying to ask these...Toward the end, Hugh and Jeff were really trying to nail Hartnett down on how his model could be tested, verified and/or falsified. If I understood him correctly, I think Hartnett basically admitted that it's a "weakness" of his model that it lacks that sort of observational testability. In my opinion, that's a little like saying, "There's an invisible elephant in the tree, but it can't be proven." This is where I have a really hard time with young-earth cosmology. Do they expect us to believe in their model based on total blind faith? Or is it reasonable to expect some kind of objective confirmation?
JH: Well, there's hardly any, hardly any similarity at all.
HR: Right. Right. I think these kinds of questions are going to help our people appreciate where your model is different.
JH: I would point out that Russ Humphreys has abandoned his earlier model completely. He no longer holds to that model at all.
HR: Right, but doesn't he still hold to the idea that gravitational time dilation is responsible for, uh, cosmic clock rates?
JH: Yes. He's got a completely new metric now and a different model completely. But you're right. His model is based on a gravitational well (?) and I pointed out to him a long time ago that it's got all sorts of problems and I think after many discussions with him, probably he won't admit this, but uh, I influenced him a bit...
JH: ...to recognize that it did have some deficits. And he's, and he's worked on alternatives since then.
HR: That would be accurate that a fundamental difference between his model and your model is that. He's sticking with gravitational time dilation as an explanation for why cosmic clocks run at a different rate whereas you're appealing to a fifth dimension.
JH: That's correct.
My question is, why? This all seems so unnecessary to me. If a reasonable and faithful interpretation of Genesis 1 allows for the "days" to be either 24-hours or long periods of time, why not allow the record of nature decide the matter? A straight-forward reading of the record of nature is that the universe is, indeed, billions of years old. Appeals to exotic models like Humphreys' and Hartnett's are simply unnecessary, in my opinion.
For more, see my book, The Bigger Picture on Creation, where I lay out the biblical case for old-earth creationism.