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:
- 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.
- The assumption that this decay rate has not changed in the past.
- 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.
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.
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