*Physicist, Gerald Schroeder, has written four books on the relation of biblical wisdom to modern science. In his book, *The Science of God*, he explains his biblical cosmology in detail. I’ve created an illustrated slideshow here (see also the “Six Days” tab at the top) that covers the basics of his model. The gist is that Schroeder is able to convincingly reconcile a literal interpretation of Genesis 1 –six 24-hour days of creation –with a universe that is billions of years old by invoking the phenomenon known as time dilation. That’s the slowing down of time in one reference frame as observed from another reference frame. It’s a scientifically sound model, but it’s also a bit difficult for the average scientific layperson to understand, because it involves one of the trickiest concepts in science — the nature of time. There are also other details that can be confusing to a reader not deeply versed in science, so I’m answering questions about the model sent in by readers. *

LH sends in another question from a forum discussion on Schroeder’s biblical cosmology:

At any point in time, the CMBR is not a single frequency, but a continuous spectrum of frequencies — to choose the “average” frequency, which doesn’t correspond to any single photon, to define a clock is questionable (unlike the frequency used to define a second, which is that of an actual photon). Also, the usual way of using light of a particular frequency to act as a clock is by defining the unit of time to be a fixed number of cycles or oscillations of the light wave (this is what is done in defining the second). Since the CMBR at early times has a higher frequency (shorter wavelength), it takes less time to go through a fixed number of cycles, so the unit of time (a “Day”) defined using the CMBR in the early universe is shorter in terms of years than it would be now, i.e. the Genesis days measured in Earth time should be getting progressively longer, not shorter (7 billion years, 3.5 billion years, 1.8 billion years, …).

It’s true the CBR has a blackbody spectrum with a distribution of frequencies, but, like every blackbody, it is characterized by a peak frequency (or wavelength, as shown below) that corresponds to its temperature. Every blackbody has one, and only one, peak frequency that corresponds to its temperature. This is why astronomers refer to just one color for the surface of a star. Stars can be approximated as blackbodies, they have a distribution of frequencies in the radiation from their surfaces, but they still have just one characteristic peak frequency that corresponds to surface temperature. And, in terms of redshift, anything that happens to one of those frequencies is going to happen in the exact same way to the other frequencies. I don’t see this as a valid criticism of Schroeder’s approach.

In terms of the length of a day, this person is mistakenly assuming that the number of cycles in a Genesis day is fixed — it’s not. The problem arises from not choosing the correct reference frames for comparison. We must compare one Genesis day with another from the point of view of our position on Earth today looking backward in time. I have an example that illustrates by analogy how we should be looking at it.

Let’s take the example of the flow of time for two different reference frames where gravitational redshift is creating a time dilation effect. The duration of a second is defined as ~9.2 billion cycles based on a particular transition of the cesium atom. This is as measured from a particular reference frame — the surface of the Earth. But let’s consider another reference frame, that of an observer in a spaceship orbiting some distance from the surface of the Earth. Let’s say the spaceship guy also has a cesium atom and is measuring the same transition, and that he is also able to measure the radiation coming from the cesium transition in the lab on the surface of the Earth. Now, in the time it takes the spaceship guy to count off 9.2 billion cycles for his spaceship cesium atom, he measures fewer than 9.2 billion cycles coming from the Earth’s cesium atom. In other words, in his one second of spaceship time is “faster” than one second of Earth time. The same number of cycles are both are experienced as one second by observers within their respective reference frames, but the cycles from Earth have been stretched by some factor corresponding to the effect of Earth’s gravity as measured by the guy in his spaceship reference frame.

Now, let’s extreme-ify this example by considering a planet — Planet X — for which the gravity is so extreme that, instead of the tiny time dilation effect observed due to Earth’s gravity, time near the surface of Planet X flows at half the rate as time for a spaceship orbiting Planet X. Let’s posit hypothetical observers on the surface of Planet X and in the spaceship, respectively. The guy on Planet X has a telescope he can use to peer into the spaceship and observe everything the spaceship guy is doing. He notices that the spaceship guy is doing everything twice as fast as he is on Planet X. He notices that a day passes on Planet X while two days pass for the guy on the spaceship. Note that the same number of cycles are not taking place on Planet X and on the spaceship during this little scenario; there is no requirement that this happen.

The difference in the flow of time in the previous two examples is due to gravitational redshifting, but we can take the same principle of time getting stretched out when viewed from different reference frames and apply it the expansion of the universe. In this case, however, instead of two reference frames that differ in *location*, we’ll consider two reference frames that differ in *time*.

Let’s consider time dilation as measured from the light curves of identical supernovae. A light curve is the brightness of a supernova as a function of time (usually measured in days). Type Ia supernovae have characteristic light curves that are always the same, because they all originate from the same type of star — this is what makes them excellent standards by which we measure cosmological effects. We can observe a nearby (roughly corresponding to the present time) Type 1a supernova and see that it takes about 20 days for the supernova to fade appreciably from peak brightness. If we observe another Type 1a supernova that’s at a distance corresponding to when the universe was about half its present age, the light curve makes it appear as though it takes 40 days for its brightness to fade by the same amount — twice as long for the exact same type of supernova. This is the time dilation effect due to the expansion of the universe. The light we receive now from an event that happened billions of years ago has been stretched to half the frequency — time appears to be flowing at half the rate *now* that it was when the light was emitted *then*. Again, there is no requirement that the number of cycles be made to equal each other in this comparison.

In the last example, we are comparing the flow of time at two different times in cosmic history from the point of view of the Earth, looking backward in time. There is no requirement that the number of cycles be the same for each day. Each successive day, when compared this way, is shorter than the previous day, because the flow of time has slowed down compared with the previous day. This forms the basis of Schroeder’s biblical cosmological model.

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