In the Big Bang theory of the universe, does the value of the speed of light enter into the calculation that determines the age of the universe, and if yes, in which way?
Asked
Active
Viewed 330 times
2 Answers
1
The title of the question is this:
Does the age of the universe depend on the speed of light?
The body of the question is this:
In the Big Bang theory of the universe, does the value of the speed of light enter into the calculation that determines the age of the universe, and if yes, in which way?
These are really two different questions. The speed of light is a constant, and it doesn't make sense to ask how something depends on a constant, only how it depends on a variable. For example, I could ask whether the area of a triangle depends on the value of 1/2. That doesn't really make sense. One way of finding the area of a triangle might be to take the base and the height and do $(1/2)bh$, but that doesn't mean that if we change the value of 1/2 to .503, the area of triangles would change.
We could also ask why the speed of light has the numerical value it does in the SI. The answer is that the meter and second were originally based on properties of the earth and its orbit, so $c$ has the SI value it does because of an accident of the formation of the solar system. It doesn't make sense to ask whether the age of the universe depends on an accident of the formation of the solar system. We might as well as whether the age of the universe depends on the fact that the Mediterranean has an outlet to the Atlantic.
The second question is a different one, and it depends on details of how the age of the universe was determined. There is more than one way to determine the age of the universe. For example, we know that the universe isn't infinitely old, because deuterium still exists, and our universe now only has ways of destroying deuterium, not of replenishing it. On the other hand, the universe can't be younger than the oldest globular clusters. These two observations put a (loose) set of bounds on the age of the universe. Could an intelligent species set these bounds without ever having measured $c$ in their own system of units? I don't know, and the question isn't very meaningful. We would have to know what their system of units was based on, and all kinds of historical and accidental facts about their procedures for defining and measuring various things. And even if we did know those things, we wouldn't know whether there were some other method they could have used for bounding the age of the universe -- perhaps the fossil record, or measurements of the Hubble constant.
0
You can look here for an actual calculation of the age of the universe, assuming a $\Lambda$CDM universe.
As you can see, in this calculation the speed of light doesn't enter, but it probably does in, at least some, of the measurements of the Hubble constant, $H_0$, which is a parameter we need to fix from observation.
Oyvach
- 69