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Our future, our universe, and other weighty topics


Friday, February 6, 2015

3 Reasons the Age of the Universe is Highly Uncertain

Last month cosmologist Ethan Siegel made these dogmatic declarations with a naive enthusiasm:

The Universe is 13.81 billion years old... The uncertainty on this is tiny, at only around 120 million years, meaning that we know the age of the Universe to a 99.1% accuracy!

But in this post I will give three reasons why we do not know with any certainty the exact age of the universe, contrary to Siegel's claim. This will not at all be some post designed to get you to think that the universe is about 6000 years old, and I have never used the book of Genesis as a guide when considering the age of the universe. But even without considering any scripture or holy book, it is easy to come up with several good reasons why we cannot have any certainty about how old the universe is.

Reason #1: There are very many uncertainties in the very long and complex chain of assumptions used to derive an age of 13 billion years for the universe.

Before considering the age of the universe, let's consider something simpler: the age of our planet. By what reasoning do scientists conclude that Earth is 4.5 billion years old? A scientist would answer: earthly rocks have been dated to an age of more than 4 billion years.

But we can think of such a claim as something that is sitting on a 3-legged table. There are three legs that support such a claim, and each of these legs involves complexities and uncertainties. The three supporting legs are these:
  1. The assumption that we have correctly figured out the decay rate or half-life of one or more radioactive isotopes used to date the rock.
  2. The assumption that this decay rate has not changed in the past.
  3. The assumption that we have correctly measured the amount of the radioactive isotope in the rock.
The first assumption cannot be justified through any simple argument, because a long and complex chain of reasoning is required to back up any claim that a particular isotope has a particular decay rate. The second assumption is basically just an article of faith. We have no way of knowing whether the decay rate or half-life of isotopes may have changed in the past. The third assumption also involves uncertainties. When scientists measure the amount of radioactive isotopes in a rock, they are usually measuring incredibly small quantities; and such measurements may involve errors.

For scientists to be wrong when they claim that a particular rock has been dated to an age of 4 billion years, it's not necessary that all of these assumptions be wrong. It would merely need to be that one of these assumptions be wrong. Since each of these assumptions involve a good deal of uncertainty, we cannot be so certain that a rock supposedly dated to an age of 4 billion years has such an age. Such a rock probably is much, much older than 6000 years old, but we can't be quite so certain about the rock's age.

The situation described here in regard to the dating of a rock is similar to the situation in regard to the scientific dating of the age of the universe. If you were to get an astronomer to explain in detail how we know that the universe is 13 billion years old, he might start on a chain of reasoning involving complex topics such as galactic redshifts and even murkier assumptions such as how much dark matter exists. But there are great uncertainties involved at many points in such a chain of reasoning. Cosmologists like to gloss over these uncertainties, and talk as if everything is “cut and dried,” but it isn't.

If I do a Google search for “how do we know hold old the universe is,” the second item in my search results is a wikipedia.org article on “Age of the universe.” I don't see how anyone can read that article and claim it is a coherent explanation of evidence showing the universe is exactly 13 billion years old. The article also notes, “Calculating the age of the Universe is accurate only if the assumptions built into the models being used to estimate it are also accurate.” That's exactly the problem. Our estimates of the age of the universe depend on model assumptions, some of which may be inaccurate. If any of the assumptions are inaccurate, the estimate may be wrong, and possibly very wrong.

Moving on to the third in my search results for “how do we know hold old the universe is,” I get a web site for a scientific space probe. That site basically argues: we know the universe is older than 10 billion years old, because globular clusters are at least that old. But the chain of reasoning used to establish the age of globular clusters is also a long and complex chain of reasoning, and there is no way to directly and simply measure the age of such a cluster. The site notes that some estimates come up with an age for globular clusters as high as 18 billion years old – five billion years older than the estimated age of the universe.

A globular cluster (Credit: NASA)

In short, there is much, much less certainty here than one would think from reading some cosmologists. When someone such as Siegel refers to a 99.1% accuracy in an age estimate, what he really means is: given the assumptions of my model,there is a 99.1% chance that the universe's age falls within this range. But there may be a 30% chance that one or more such model assumptions may be wrong. So the real uncertainty is much higher.

Reason # 2: The universe we observe may have been created much less than billions of years ago, by some power (divine or not) that started it out in a relatively complex state.

Imagine a father gives a child named Susan a story to read. The story tells the tale of a man named John who was born 22 years ago. The father asks Susan to determine the age of John. Then there might be a conversation like this:

Father: So tell me, Susan, how old is John?
Susan (after re-reading the story): John is exactly 22.
Father: Are you sure of that?
Susan: Yes, I'm quite certain of that. It clearly says he was born 22 years ago.
Father: Well, you're wrong. The correct answer is: John is only two hours old. Because that's when I wrote this story involving John.

We may be making the same kind of mistake as Susan. We live in a universe that seems to have within it a kind of “background story” that it is something like 13 billion years old. But that whole universe, including this “background story,” may have been created much more recently.

Let us consider the fact that an omnipotent God could create any type of universe that he wants, including universes other than universes which have that “just created” appearance. An omnipotent God could instantly create from nothing a universe exactly like the universe that existed in 1000 BC or 100 AD or 1000 AD or January 1, 2000. Consider if God wanted to create a universe exactly like the one that existed on midnight Eastern Standard Time at January 1, 2000. God would merely need to will into existence an expanding universe of billions of galaxies, a universe that would include at least one planet with billions of people. God could instantly will into existence those people existing at that date, having them suddenly come into existence with various memories and various states of motion (some walking, some driving, some sleeping, some celebrating the new year in Times Square). Under such a scenario, billions of people would suddenly come into existence, convinced they had lived for years. But they would actually just be recently created.

My point is that we cannot be certain that such a thing did not happen any length of time ago-- 100,000 years ago, 10,000 years ago, or perhaps only 10 years ago. The fact that you may have memories of having lived for 20 years does not make it certain that you actually have lived for twenty years. You and everything else in the universe could have been created ten years ago.

Now some might argue that it would be deceptive for God to give you memories of some meaningful social experiences you didn't actually have. Even if you grant such debatable reasoning, we are still left with no reason why the universe could not have been created from nothing in the exact state we think the universe had in 3000 BC or 50,000 BC. In fact, we can think of a reason why such a thing might have happened. Perhaps God wanted to “cut to the chase,” as they say, and create a universe immediately filled with interesting life forms, rather than waiting billions of years for such life forms to appear.

If you don't like the theistic tone of this reason, there is an alternate version involving no theistic assumptions. It could be that we are just living in a computer simulation, as Nick Bostrom has suggested, perhaps a simulation created by some civilization vastly older than ours. If so, such a simulation may not have been created billions of years ago, but only hundreds of years ago, or thousands of years ago. In such a case, the real age of the universe might not be 13 billion years, but perhaps some vastly smaller number.

Reason # 3: There are philosophical reasons why the universe might not be any older than the time when Mind first existed.

The standard assumption of scientists is that matter is the father of Mind. The assumption is that first there was only matter for many eons, and that later Mind arose from matter. But there are difficulties in such an assumption. How could Mind (something immaterial you can't touch, see, or directly observe) arise from matter, a totally different type of thing? The concept of Mind arising from matter sometimes seems like the idea of blood oozing out when you squeeze a stone.

So it may be we have things mixed up. Rather than matter being the father of Mind, Mind may be the father of matter. It may be that matter did not exist in any real sense until there were minds to perceive that matter. Such an idea can be supported by arguments such as those given by the famous philosopher George Berkeley. Such an idea can also be supported by arguments derived from quantum mechanics, arguments that infer that consciousness is a vital ingredient in the collapse of the wave function, involved when probabilities become actualities.

Suppose such a radical assumption is true – that Mind is the father of matter, rather than matter the father of Mind. Then we would have to rethink the age of the universe. Under such a scenario, the age of the universe might be considered the length of time that conscious beings have existed. Such an age might be 100,000 years, or perhaps many millions of years or a few billion years (considering the possibility of extraterrestrial intelligence that may have arisen long ago).

The uncertainties here are many. Rather than pretending that we are very wise beings who have figured out the exact age of the universe, we should humbly realize that we are bumbling little newbies who have only just started to put together a few pieces of the vast cosmic jigsaw puzzle.