Physicists who speculate
about the multiverse (a vast collection of universes) are very good at
math, but their essays are often shockingly poor at logic. An example
is a recent essay by string theorist Tasneem Zehra Husain.
Husain states this early in the essay: “The same process that created our
universe can also bring those other possibilities to life, creating
an infinity of other universes where everything that can occur,
does.” The origin of our universe in the supremely mysterious Big
Bang is a total mystery. There is no understanding whatsoever of any
natural or physical process that can create a universe or did create
our universe. No
physicist has any understanding whatsoever of a universe creation
process. There is no evidence for any physical universe beyond our
own. As for the notion of a universe-creating process creating not
just one other universe but an infinity of them, that's just
runaway speculation no more substantial than speculating about an
infinity of unicorn kingdoms.
Husain spends most of her
essay talking about how scientists “feel about the multiverse.” I
guess that may be a good way to fill up a long essay when you have no
evidence to back up your central claim (the idea of a multiverse,
that there are countless other universes). Husain offers this reason
for believing in the multiverse:
The multiverse explains
how the constants in our equations acquire the values they do,
without invoking either randomness or conscious design. If there are
vast numbers of universes, embodying all possible laws of physics, we
measure the values we do because that’s where our universe lies on
the landscape. There’s no deeper explanation. That’s it. That’s
the answer.
I give
in this essay six reasons why the multiverse idea is quite worthless
for explaining the fitness of our universe. To explain something
means to discuss one or more causal factors that caused something or
made that likely. You do not do any such thing if you say (as
multiverse theorists do) “There are an infinity of universes, and
our universe just got lucky.” It is also 100% superfluous to
imagine the other universes in such a case, because you can just as
easily say “Our universe just got lucky” when imagining that no
more than one universe exists. You do not increase the likelihood of
our particular universe getting lucky by imagining other universes
(and, more generally, you do not increase the likelihood of success
on any one particular random trial by imagining an increased number of random
trials). So the fine-tuning of our universe (including its physical
constants) does not provide any rationale for believing in a
multiverse. The “why was our universe so lucky" question looms
with equal weight, regardless of whether there is or is not a
multiverse.
When
used to explain cosmic fine-tuning, the multiverse idea therefore
pulls quite the astonishing trick: it brings in infinite baggage, but
with zero explanatory value. Imagine if some theorist were trying to
explain the features of one rabbit by theorizing that there are an
infinite number of rabbits. But suppose that such a theory did
actually nothing to explain the features of that one rabbit. That
would be kind of the ultimate “epic fail,” rather like some
President paying all the money in his country to buy some contraption
that didn't even work. Such is the epic fail of the multiverse
theorist in this regard.
Referring
to some other thinker, Husain states the following:
Your reasoning is in very bad shape
indeed if your best argument for the existence of something is that
it opens up “satisfying” or “gratifying” possibilities. That
reeks of some kind of wish-fulfillment fantasizing rather than hard
thinking.
Husain also gives us this
cringe-inducing howler: “Logically speaking, an infinity of
universes is simpler than a single universe would be—there is less
to explain.” No, very obviously an infinity of universes is
infinitely less simple than a single universe, because it
involves infinitely more to explain.
When our physicists give
us this type of “black is white, squares are round” type of talk,
this type of Orwellian doublespeak, I wonder whether we have ended up
in some strange reality in which words may be used in exactly the
opposite of their dictionary meaning. Faced with such absurdity, it
is helpful to have a few reality checks such as the ones below.
- There is no evidence for any physical universe beyond our own, nor can we can imagine any observations that we might ever have that would give us such evidence (anything we might observe would be part of our universe, not some other universe).
- The idea that there are many universes beyond our own does nothing to explain the life-favorable characteristics of our universe.
- The "cosmic inflation" theory of the exponential expansion of the universe during part of its first instant is not well supported by evidence, and does not intrinsically require any universe beyond our own.
- We have no scientific understanding of what caused the beginning of our universe, nor is there any physical understanding of why the universe is so fine-tuned.
- There is no evidence at all for string theory. String theory has thus far been pretty much a 35-year waste of time, the biggest flop in the history of modern physics. String theory is based on another theory called supersymmetry, which is rapidly dying, because experimental results from the Large Hadron Collider have all but closed the door on it (as discussed here).
From reading an essay such
as Husain's, you might get the impression that the multiverse is some
hot topic that is dominating the papers of theoretical physicists.
But it isn't.
Below is a diagram from a
scientific workshop. The line at the bottom represents the fraction
of papers that have been written about the multiverse.
As we can see, it seems
there are very few scientific papers actually being written about the
multiverse.
There is a way for you to
make your own graph similar to this graph, using the technique below.
- Go to the arXiv server for scientific papers, where copies of all physics and cosmology papers have been posted for the past twenty years.
- Click on the Advanced search link, taking you to this page.
- Type in a search topic, and limit the results to a particular year.
- Note how many papers appear in the search results, and add that number to a row on a spreadsheet.
- Graph the results.
Below is a graph I made
using this technique. The number of papers on the supersymmetry
theory (also called SUSY) should probably be twice as high, because I
searched using only SUSY as a search string, without using
“supersymmetry” as a search string.
My graph above is
consistent with the first graph. What we see is that the number of
scientific papers written about a multiverse is only a tiny fraction
of the papers written about other speculative topics such as string
theory, cosmic inflation theory, and supersymmetry theory.
Here are some numbers from
recent years.
2013 | 2014 | 2015 | 2016 | |
String theory papers | 365 | 419 | 377 | 295 |
Inflation theory papers | 276 | 465 | 402 | 339 |
Multiverse papers | 8 | 10 | 16 | 16 |
SUSY papers | 105 | 104 | 114 | 71 |
Why are there so few
papers written about the multiverse? Is it because physicists don't
like to speculate? No, they love to speculate, as shown by the 1000+
speculative papers listed in the table above (string theory, cosmic
inflation theory, and SUSY are all extremely speculative theories).
The reason so few papers
have been written about the multiverse is pretty much that there's no
factual basis on which to write a multiverse paper. There's no
“there” there.
Don't let Husain fool you.
The multiverse is just a “castle in the sky” that a few fantasist
physicists are building, from a few gossamer threads of speculation.
Postscript: See Peter Woit's post about "Fake Physics," with some relevant comments.
Postscript: See Peter Woit's post about "Fake Physics," with some relevant comments.
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