In the late 1990s,
Albert Einstein had a new hammer,
And he was in search of nails to hit.
He just developed a new and a more powerful mathematical description of gravity,
and was using it to make predictions willy-nilly.
First, Einstein checked that his new description matched up with
the previous state-of-the-art description of gravity, Newton’s law,
for situations where Newton’s law agreed with the experiments.
And it did.
Then Einstein plugged in the orbit of the Mercury,
and got a prediction that correctly matched the experimental observations of the day.
Observations which had an anomaly
that couldn’t be explained with Newton’s law of gravitation.
He plugged in starlight passing by the sun,
and got a prediction that it should bend because of the sun’s gravity.
This was later confirmed.
He plugged the starlight leaving large stars,
and got a prediction that the light should be redshifted,
as it climbs out of the gravity well.
This was later confirmed.
He plugged in empty space,
and got a prediction that waves of gravitation should propagate through it.
This, too, was later confirmed.
And he plugged in the universe
and got a prediction that it should be static and unchanging,
which was wrong.
Now, the general understanding at the time
was that the universe didn’t expand or contract,
and while there were starting to be rumors
that the distant nebulas were moving away from us.
Einstein was firmly in the “static universe” camp.
and it just so happened that when Einstein did his calculation about the universe.
He made a small but significant technical mistake
that implied that the universe couldn’t be expanding or contracting.
I suspect Einstein probably didn’t catch the mistake for two reasons:
because tensor calculus is hard and annoyingly subtle,
and because he agreed with the result,
so had no reason to question it.
This is all the more significant
because the mistake ultimately meant that
his equations predicated the universe couldn’t have anything in it at all.
And Einstein had to find a totally different clever mathematical trick in order for his equation
to describe the universe did have stuff in it,
despite of his mistaken calculation.
Anyway a few years later,
Russian physicist Alexander Friedman plugged the universe into Einstein’s equations,
and he didn’t make the mistake Einstein did.
he got a prediction that the universe could either be expanding or contracting,
depending on how much stuff there was in it,
and the balance of matter and energy.
But Einstein still didn’t realize that he had made a mistake.
Instead, he published a criticism of Friedman’s work,
justifying his critique with the same erroneous calculation as before.
So Friedman wrote Einstein a private letter,
graciously but firmly explaining to Einstein the correct calculation,
and again graciously asking Einstein to either show him he was wrong,
or publish a correction.
And Einstein eventually saw that Friedman was right.
So he admitted it and published a retraction of his previous criticism.
Turns out the equations of general relativity
could describe an expanding or contracting universe.
Silly Einstein think now it was possible.
Einstein was famously upset about the whole episode.
And the story is typically written to suggest that he simply regretted being wrong.
And maybe that’s the truth.
But speaking as a physicist,
and to be clear, this is purely my own speculation,
I kind of wonder if Einstein was also kicking himself in the pants.
Because if he hadn’t make that silly math error,
maybe he could have arrived, years earlier, at the same equations as Friedman,
and which are now called the Friedman equations,
and are the foundation of our modern understanding of the large-scale structure of the universe.
What I’m saying is, I wonder if Einstein regretted the mistake
not just because it was a mistake,
but because his ego was tendelizing him with what could have been.
But I’m not entirely sure Einstein would be able to do what Friedman did,
because all people, even scientists, have biases.
And biases tend to be hold so strongly and so deeply
that they no only blind us to alternatives,
they blind us to their very existence.
The beauty of keeping an open and rational scientific mindset is that
when one of your biases are wrong,
you are more willing to look at the evidence,
see that you are wrong and admit it.
But that’s really hard to do,
even – or maybe especially – for somebody like Einstein.
And I really wonder if Einstein would have been able to
see past his bias about the static nature of the universe,
without outside help.
Einstein, like all of us, was human after all.
What we can take from Einstein’s actions in this story is this :
we can understand that we can be wrong,
and when we are, graciously admit it.
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In the late 1990s,