# Need help with planck time

1. Apr 28, 2004

### Void

O.k., so i'm reading this article by victor stenger called Fitting the Bible to the Data where he is criticizing this guy Schroeder's attempt to fit the bible creation story in with big bang cosmology. he chooses the time of quark confinement, or 10^-4 seconds to start. this is the part that explains this in more detail with an equation:

"Each of the six days in Schroeder's Genesis actually takes a different length of earth time. The duration D, in earth days, of each cosmic day t is calculated from the formula D = (Ao/L)exp(-Lt), where Ao = 4x1012 (the ratio of the frequencies of the cosmic microwave background at quark confinement compared to now) and L = 0.693 (natural log of 2). More simply, cosmic day one is 8 billion earth years long and you divide by two to get the duration of each succeeding cosmic day."

so i'm talking with stenger trying to understand some things here and he says planck time, or 10^-43 is the only non-arbitrary time to use. now i'm not very experienced with math or phsyics at all, so i'm picking up whatever i can very slowly as i go along, but i'm not even getting the answer 8 billion earth years when i follow what the equation says, probably because i don't know what i'm doing and need help and decided to come here. but what i want to know is how the calculations would work out if you use planck time instead? would you need the ratio of frequencies of the cosmic microwave background at planck time compared to now to figure this out? what is this number? if this makes any sense, could someone help me figure out what the results would be for plank time, because like i said, i look at the equation and try to reproduce the result of 8 billion years, but i'm not getting it. i'm a math moron i guess. anyway, sorry for rambling so much on a topic i'm sure isn't the most important in the realm of physics, but it caught my interest and figured i could get some help.

2. Apr 30, 2004

### Nereid

Staff Emeritus
Well, I haven't got any idea what the quote is all about, nor how the factor Ao was derived, but I can get 8 billion years (more or less):

The first 'cosmic day' is t = 1. This means the exp(-Lt) term is 0.5 (one half). You can confirm this with your calculator, or from the description of what 'L' is (and a little math).

The trick seems to be in: "The duration D, in earth days, of each cosmic day t...", with the same word ('day') being used for two quite different things! Anyway, 4 trillion (4x1012) divided by 0.693 then divided by 365 (Earth days per year) gives ~16 billion, which when multiplied by ...

Since the second 'cosmic day' will be 4 billion Earth years, and the third 2, we're already older than the universe (13.7 billion years), without even adding the fourth day's 1 billion years! Oops, another cute idea is crushed by observational results.