Humility and the argument from authority

The “argument from authority” consists in backing your point with a statement from an authority. Of course, it is not a demonstration per se. Of course again, it has no value if your authority has no reason to be knowledgeable about the field related to your statement. Yet, provided your authority is definitely knowledgeable about your point, like quoting Einstein on physics, I think this kind of argument has some value.

Here’s how.

The problem of the Now

A few years ago, I came across an article on the “problem of the Now”. Why nothing in physics singles out the present moment, which is so important to us? At first, I thought “what the hell is this about”. And then I learned that this problem was of great concern to Einstein[1],

“Once Einstein said that the problem of the Now worried him seriously. He explained that the experience of the Now means something special for man, something essentially different from the past and the future, but that this important difference does not and cannot occur within physics.”

I thought to myself that if someone like Einstein, who knew a little bit about physics, was interested in this, it may not be completely silly. I later learned that this problem continues to occupy people like David Mermin[2]. In short, it seems to be a serious problem. But I had to see that people of this calibre were taking it seriously before I would consider it as such.

A matter of humility

Obviously, calling an Einstein to the rescue does not in itself mean that a thesis is correct. No one writes in a scientific paper “this assertion is true because so-and-so said it”. Strictly speaking, this is not a demonstration.

However, if the argument of authority has any value, provided the authority in question is indeed an authority, it is perhaps in the humility of the receiver. Indeed, it would have been presumptuous of me to declare that this “problem of the Now” is a farce and that Einstein and Mermin understand nothing about it.

So when I see people denouncing an argumentum ad populum, which is how you call this kind of argument when you want to appear erudite, I can’t help thinking that the denunciation is very legalistic.

Granted, just because an Einstein said something about physics doesn’t mean it’s true[3], but humility demands that we don’t throw it out the window.


[1] Cited in Paul Arthur Schilpp, The Philosophy of Rudolf Carnap, La Salle, IL: Open Court, p. 37.

[2] David Mermin is the prototype of the high calibre physicist virtually unknown to the public.

[3] For example, he was wrong about quantum mechanics. But his objections were incredibly fruitful.

Why is there less disruptive science? My 5 cents

An article recently published in Nature reported that Papers and patents are becoming less disruptive over time. I don’t object to its conclusions. I don’t think scientists are dumber than before, or that they have grown lazy, or that they are now more interested in grants than in science. I think the main raison is that we already discovered all the scientific continents that were within our reach [1].

Let me explain a bit.

Warning 1: I’ll talk only about physics.

Warning 2: To make it as short as possible, I have simplified the story and refrained from many potential disgressions. Also, I don’t reference everything I mention. There would be hyperlinks and/or footnotes in every sentence. Yet, I don’t think anything below is groundbreaking. Just Google the names to find out more about anything.

First love

How do we learn stuff? You come up with an idea, then test it through observation or experiment. Or the other way around. At any rate, without observation or experiment, there’s no way to know whether your idea holds water.

Often, observation or experiment tell you something is wrong with your ideas. For example, Mercury’s orbit, an observation, doesn’t obey Newton. Or hydrogen heated in a tube, an experiment, emits discrete wavelengths of light. Mercury’s observation only requires a 19th century telescope and was an element, not the only one, which prompted General Relativity (GR). The hydrogen in a tube can be done in a kitchen, and was an element, not the only one, which prompted Quantum Mechanics (QM).

So you find GR. It does a good job with Mercury. But you want more tests. So you predict how light should deviate near a star. The observation can be done. Eddington does it. And GR is right. More people think about ways to test GR, they can do the tests, and GR is found right over and over. So right that it eventually makes its way to technology: the GPS.

Also, you find QM. It fits the experiments that were already there. But you want more. So you apply QM to all sorts of chemical elements, to molecules, to metals, to liquid, even to stars. Each time, you can do a prediction, and you can do the experiment or the observation. And it works.

These are the first love moments. Everything is new.

Discovering GR and QM was like discovering 2 scientific continents. Everything you saw had never been seen. Everything you touched had never been touched. Every idea was new. And as long as you could do experiments or observations, you could know whether your new ideas were good or bad. And so, you kept progressing. Such a period necessary produces disruptive research constantly. It’s like discovering America: any place you step on has never been stepped on (by a European, of course), so you keep announcing discoveries to Isabella the Catholic, inventing names for newfound places on a regular basis.

Inflation of required resources

But as you keep discovering stuff, you need each time more elaborated experiments or observations to test new ideas.

To progress QM, you soon need particle accelerators. The “inflation” of required resources kicks in. The days of the kitchen size experiments are over, but you can still do experiments. So you keep progressing. As Andrew Strominger puts it, “I started graduate school [circa 1978] near the end of a really strong heyday of particle physics when new results were coming out of accelerators practically every week and there was all kinds of excitement”.

Or as David Gross puts it, “it would have taken centuries to find QCD without the large, very large number of experimental facts and clues”, before adding, “there’s nothing like experiment to guide us”.

To keep progressing QM, you now need bigger and bigger machines. And it eventually takes the 5 billion euros LHC, a very expensive kitchen, to confirm the Higgs boson. 48 years after its prediction.

And then, you’ve reached a point where you’re stuck with QM, because new physics does not show up in the LHC, and you’d need an even bigger machine to look for it, something that you can’t build, be it for practical or monetary reasons.

In parallel, you also want to progress GR. Granted, some of it, the GPS part, has become business as usual. But you want more, like for example, finding out about black holes. And suddenly, the “inflation” of required resources starts here also. To track the motion of some stars around the center of the Milky Way, where a black hole could lie (it does), you need the 10 meters wide Keck telescope, observing for about a decade. Then, to image the shadow of a black hole, you need the Event Horizon Telescope, which indeed is not even a telescope, but a network of telescopes across the world.

Game over?

As you were exploring the QM and GR continents, you had to use increasingly costly experimental tools, or resort to increasingly tricky observations, in order to keep learning by asking nature whether you were right or wrong. Of course, such exploration produced “disruptive papers” on a regular basis since everything was new.

Now you’re at the point where even the biggest machines in the world seem to fall short of teaching you. In the absence of experimental/observational judge capable of pruning the tree of ideas, ideas just grow, “uncontrolled”. Not that scientists refuse control. They just can’t communicate with the judge.

So game over? Is the era of “frequently disruptive science” over?

In my view, probably yes. I’m not surprised by the findings of the Nature paper.

Why? Because the next continent to explore, namely the union of QM and GR, seems so out of reach of experiment, that I wonder if we’ll ever find out how QM and GR play together. Now, if some ultraprecise experiments are done that allow to test theories of quantum gravity, then we’ll be back to the kind of exhilarating years we had some 100 years ago. This time it would all be about the exploration of the brand-new quantum gravity continent.

Now that we already discovered all the scientific continents that were within our reach, we have to make disruptive science within them. It’s not impossible at all, like Philipp Anderson once reminded us in his More is Different, of like people like Roger Blandford have been doing repeatedly simply playing with good old GR. It’s just not so easy than having to explore new ground.

I don’t think disruptions will happen as often as before, during the days of exploration. After all, it’s easier to find a fancy bar you didn’t know about in a city you’re discovering, than in the one you were born in.

[1] An option that was mentioned in another Nature article, in reference to the disruptive science paper: “In many disciplines, the fundamentals are agreed on, so most further advances will be incremental, rather than disruptive.”

A Babel universe?

Translated from “El universo Babel”, published in the Spanish review Acontecimento, nb 139, 2021.

How big is the universe?

A long-standing question that has received various answers over the centuries. Curiously, it seems that the numbers have been steadily increasing until today. Let’s go for a short walk through this matter. A short walk since many have studied the subject over the last millennia. An exhaustive review would be a book or a PhD thesis.

In the cosmology of the ancient Hebrews, our world lies beneath a dome. By identifying the most remote places mentioned in the book of Genesis, we can get an idea of the size of this vault, since it would be a hemisphere placed on the ground. From the mythical Tarshish in the west, which some place near Gibraltar, to the Kingdom of Sheba in the southeast, probably around our Yemen, we end up with a dome of at least 6,000 kilometers in diameter. According to the Pesachim of the Babylonian Talmud (about 4th century), “the size of the world is six thousand parasangs” (Pesachim 94a), that is, about 30,000 km.

Light, which circles the Earth 7 times in 1 second, takes between 0.02 and 0.1 seconds to cross this universe.

To the joy, or despair, of the students of the last 2 millennia and more, the Greeks invented [1] geometry, trigonometry, and a couple of other “y’s”. After a series of clever measurements, they managed to measure the diameter of the Earth and the distance to the Moon or to the Sun. As for the diameter of the Earth, 12,800 km, Eratosthenes got it right [2]. As for the distance to the Moon, about 380,000 km, Hipparchus of Nicaea also got it right. As for the distance to the Sun, Hipparchus himself gave 16 million km, falling short of the actual 150 million.

What was the size of their universe? From Aristotle to Copernicus, it was thought that the cosmos surrounded the Earth in concentric spheres. The Sun did not occupy the last sphere but the fourth. Before the last sphere, that of the “prime mover”, the penultimate sphere was that of the “fixed stars”. How far away were they? According to Al-Farghani, a Persian astronomer of the 9th century, they were located at about 20,000 Earth radii, that is, 128 million km. Ptolemy came to the same conclusion.

Light, which circles the Earth 7 times in 1 second, takes 15 minutes to cross this universe.

Centuries go by, and so do the measurements. In the 17th century, Johannes Kepler estimated the distance to the “fixed stars” at 60,000,000 Earth radii, or 384 billion km.

Light takes 15 days to cross this universe [3].

Centuries go by, and so do the measurements. In 1838 Friedrich Bessel succeeded in measuring the distance to a distant star. The model of “fixed stars” on a penultimate sphere was already abandoned. This time the answer does not come in light minutes, nor in light days. It comes in light years. 10.5, to be precise.

Light takes at least 21 years (2×10.5) to cross the Bessel universe.

Centuries and measurements pass. Our galaxy, the Milky Way, has been known for millennia. One just has to look up on a summer night to admire this marvel. But for centuries, people didn’t know that this whitish trail that obliterates the night sky was actually the sum of countless stars. This ensemble came to play the role of the “universe”. In 1920, it was supposed to be about 30,000 light-years large [4].

Light takes at least 30,000 years to traverse the 1920 universe.

Let’s take a momentary step back… to move forward. In the 10th century, Abd Al-Rahman Al Sufi, another Persian astronomer, describes in his “Book of Fixed Stars” (the title rings a bell, isn’t it?) what we now call the Andromeda galaxy. For Al Sufi, as for everyone until 1920, Andromeda was not another galaxy like ours. It was “something”, a “nebula” [5], inside our Milky Way. Then some started to suspect it was outside. It took until 1920 for this “Great Debate” to be settled: Are nebulae like Andromeda inside or outside our galaxy? Answer: outside. It was like realizing that New York is not a western suburb of Madrid, but another immense city on the other side of the Atlantic. Suddenly, the scale expands again. How far is Andromeda? 2.5 million light years. The famous Edwin Hubble played a role in this story.

Light takes at least 2.5 million years to cross the 1920 universe.

Twentieth-century observations continued to expand the universe. They showed that there’s more than one galaxy out there. There are billions of billions. Today, the diameter of the observable universe is estimated at nearly 100 billion light-years. It has 2 trillion galaxies. Each with billions of stars.

Are we there yet? Not sure. There may be even more.

Einstein taught us that space is just another physical object that can be stretched or compressed. Until Einstein, space was the unchanging stage in the theater of the universe. With Einstein, space becomes another actor in the play. In fact, observations over the last 100 years have shown that our universe is expanding. Really. It went through the famous Big Bang some 13 or 14 billion years ago and since then, it is expanding. Now, according to speculative theories, any point in our universe could begin to “inflate”, giving birth to another Big Bang from which another universe would expand, like a bubble growing from the surface of another. And the process would never stop. Each universe in turn would give birth to other universes, which would give birth to other universes, and so on.

Of course, that seems far-fetched. However, from planet Neptune to antimatter, through a dozen of elementary particles like the famous “Higgs boson”, it happened so many times in the history of science that something predicted by a theory ended up being found in the real world, that we’d better delay the mockery [6].

If these speculations are true. If this “multiverse” really exists, then our universe of 100 billion light years minimum, is just one more. One more among millions of millions or even maybe an infinite number of universes.

0.02 light seconds, 15 light minutes, 15 light days, 21 light years, 30,000 light years, 2.5 million light years, 100 billion light years, multiverse… Our perception of reality has not stopped growing. In a little more than 20 centuries, it went from about 10-10 to 1011 light years!

Could it be that we live in something like Jorge Luis Borges’ The Library of Babel ? In Borges’ novel, we could imagine that “the men of the Library” first thought that their library occupied what they had in sight. Then, as they explored it, they realized it was much larger than they thought. They even suspected that it might be infinitely large. In fact, the infinite potentials of our universe and those of the library of Babel have received a common attention by some physicists.

It seems “common sense” is not well adapted to assess reality. I don’t think wise men like Aristotle would have ever suspected that their universe was so small compared to the real one. But the most amazing thing of all is that maybe in a certain sense, Borges’ The Library of Babel really exists.

Some bibliography

Planetary Astronomy from the Renaissance to the Rise of Astrophysics, Part A, Tycho Brahe to Newton, R. Taton, C. Wilson, Michael Hoskin, Cambridge University Press, 2003.

Elementary Cosmology: From Aristotle’s universe to the Big Bang and beyond, James Kolata, ‎ Institute of Physics Publishing, 2020.


[1] Or, discovered ? Fascinating debate. In this regard, I recommend the excellent Conversations on Mind, Matter, and Mathematics, by Jean-Pierre Changeux and Alain Connes.

[2] By the way, that the people of the Middle Ages thought the earth was flat is what we now call a Fake News. They knew very well that it was round. On the origin of this Fake News, see Inventing the Flat Earth by Jeffrey Burton Russell, or the recent PhD thesis of my friend Pablo de Felipe at the University of Bristol, Flattening the Medieval Earth. The Early Modern Origins of the “Flat Error”.

[3] The invention of the telescope is not unrelated to this sudden increase in measured distances.

[4] See the April 26, 1920 debate between Harlow Shapley y Heber Curtis, The Scale of the Universe, Bulletin of the National Research Council, Vol. 2, Part 3, May, 1921, Number 11, pp 171-217.

[5] Scientific synonym for “I have no idea what it is”.

[6] See the Wikipedia page on Timeline of particle discoveries.

Unexplained doesn’t have to be supernatural

1913. Some experiments just revealed the structure of the atom. A positively charged nucleus with electrons turning around. The problem? The known laws of physics at that time cannot explain it. According to XIX century physics, the electrons should eventually crash on the nuclei [1].

It took quantum mechanics to solve the conundrum.

The atom doesn’t break any laws of physics. It is not supernatural. It’s just that back in 1913, the laws it follows were unknown.


100 years later, same pattern. We know that some 13 to 14 billion years ago the universe was extremely dense and hot, and that it has been expanding since then. This is what we call the Big Bang. But we do not know how it got there in the first place. Why? Because we do not know the laws of physics that apply before.

It’ll take quantum gravity to solve the conundrum.

The pre–Big Bang era doesn’t break the laws of physics. It doesn’t have to be supernatural. It’s just that as of 2022, the laws it follows are still unknown to us.

Unexplained doesn’t mean supernatural.


[1] The Niels Bohr’s article linked is for free here.

On Leonard Susskind’s Theoretical Minimum

I just finished watching Leonard Susskind’s Theoretical Minimum. A series of 6 + 9 courses on theoretical physics. An adventure. Really.

The first 6 are the “Core Courses”. The next 9 are the “Supplemental Courses”. Save a few exceptions, each course amounts to some 10 lectures, nearly 2 hours each. In total, that gives you 15 x 10 x 2 = 300 hours of physics. It took me 1 or 2 years to complete the program.

What about the level of the course? To start with, you must be fluent in calculus. All the more than Susskind frequently forgets a sign or a constant here and there, or simply drops one when he doesn’t want to drag it further into the algebra. For the rest, if what I write below rings more than a bell, then it’s OK.

Each lecture comes with a short summary on its YouTube page.

Short version: Fantastic.

Longer version: Here are some comments

  • Susskind’s emphasis is on physics more than math. It’s clear that he masters most of contemporary theoretical physics. He sees the unity of it all and wants to convey it to the audience. On many occasions I found him “Feynman-like”.
  • His exposition of the Dirac equation is stunning. It can be found in Lecture 6 of the Particle Physics 1: Basic Concepts course.
  • About this unity thing: he starts with Classical Mechanics. Why? Because there you introduce Lagrangians and Hamiltonians… which prove useful all the way to String Theory.
  • More about this unity thing: When treating the harmonic oscillator in Quantum Mechanics, he does NOT even analytically solve the Schrödinger equation. His emphasis is purely algebraic. For example, he shows you how such and such operators add or take 1 level of excitation to the system. There, he has already in mind Quantum Field Theory with its creation and annihilation operators. Indeed, the harmonic oscillator is found useful all the way to String Theory (again).
  • In fact, after listening to him, I now find that one of the deepest laws of physics is this Lagrangian formalism. From Classical Mechanics to String Theory, the same pattern pops up everywhere: you find the Lagrangian and the rest follows.
  • Students ask many questions and he always replies with kindness. I don’t remember him ever even suggesting a question was dumb.
  • In fact, most questions are profound. He has smart students. Questions and answers are worth listening too. I remember one student asking if the Covariant Derivative in General Relativity has common points with the Material Derivative in Fluid Dynamics. Susskind’s answer was “well, never thought about it but yes, I think you’re right”. Asking such a question means you really understand what you’re being taught.
  • When introducing you to new stuff, he always starts from known ground. Even String Theory starts with the harmonic oscillator.

A few minor negative points:

  • I would have loved something on Loop Quantum Gravity, but no. I guess Carlo Rovelli does a great job at teaching it (probably my next journey).
  • On his own admission, he really doesn’t like Supersymmetry (SUSY) nor its math. I found his course on SUSY very confuse. For example, I may have missed something but I don’t remember he ever explained why Grassmann Numbers were needed for SUSY.
  • He likes to eat a snack while teaching and then speaks with his mouth full, which tends to be quite unpleasant. Yet, he does it only once in each lecture.

What is a theory ? Forget about the dictionary

The Science & Faith debate is often the scene of a sub-debate around the meaning of the word “theory”. For example, someone will claim, “evolution is just a theory”, intending to lower it to the level of a simple hypothesis. The opponent will then be quick to point out that a “theory” is more than a hypothesis. Usually follows a boring semantic ping-pong where dictionaries act as rackets.

The problem is that when it comes to using the word “theory”, scientists don’t really care what dictionaries actually say. The same “theory” sticker can be put on highly speculative ideas, as well as on knowledge thoroughly verified by experience and/or observation. Let’s see an example of each.


String Theory is currently one of the best candidates for the unification of quantum mechanics and general relativity. Whether in French, English or Spanish, it is always called this way: String Theory. Yet, this is a highly speculative theory that has not yet received any experimental or observational support. Not that we don’t want to do it. It’s just terribly difficult. As a result, here’s chapter 7 of string theorist Joseph Conlon’s book, Why String Theory ?, probably the shortest chapter in the history of scientific literature,

Now let’s move on to another theory. Quantum field theory is the most successful version of quantum mechanics, a scientific adventure that began almost 100 years ago. Whether in French, English or Spanish, it’s always called this way: quantum field theory. But here, we’re talking about the theory best confirmed by experience or observation. The record in this respect is held by the measurement of the “abnormal magnetic moment of the electron”, where the theory/experiment agreement reaches the equivalent of a 3 cm accuracy over the Paris-Madrid distance. Much of today’s industrial world relies on quantum mechanics. In short, it’s far more than just a guess.


So we are dealing here with 2 theories that are completely different from each other as to their speculative character. The first, string theory, is so far completely speculative. The second, quantum field theory, is experimentally confirmed with an incredible degree of precision, and you use it every day. However, both are designated by the same word “theory”.


What is a theory? I’m afraid a dictionary may not replace a genuine understanding of what we are talking about.


Parable of modern times (among others)

Any resemblance to actual situations may not be purely coincidental.


The sacred texts of this religion included the book of the prophet Nhyno Ferrher. One of his Psalms had the following verses,

We call it the south

Cause time is so long there

That life sure will take us

More than a million years

And we like to stay there

In lieu of “And we like to stay there”, some manuscripts had “and always in summer”.

Debate raged between some factions.

Some atheists were adamant: this religion was flat stupid. How can one claim to live a million years? And then what is this business of time “so long”? And on the top of it, “always in summer”? Just how can time last if seasons don’t change? And how could seasons don’t change anyway?  Do these guys think they live on something like the Ursa Minor Beta planet of The Restaurant at the End of the Universe, where it is nearly always Saturday afternoon just before the beach bars close? Without a doubt, these believers were completely numb.

Others, fervent believers, thought on the contrary that this Psalm showed that there was a time when indeed people lived a million years. There was no room for doubt since, moreover, the text said “sure”. And “sure” means it’s sure, right? In addition, for these faithful, “time is so long there” prefigured, as clearly as precociously, Einstein’s Relativity and its stretchy time, irrefutable proof that the text was inspired.

Between these 2, a crowd of music lovers, believers or not, were just happy to listen to this wonderful Psalm, wondering what was wrong with the others.

Fortunately, nowadays, nobody would fall into such pitfalls, isn’t?

No, energy is not always conserved

Energy conservation: what is at stake

The law of conservation of energy comes up from time to time in the science and faith debate. In various ways. Let me just bring up 2.

  • Some will invoke it to argue that the universe must be eternal, since if there is energy in it, and if this energy is conserved, then it has always been there. Indeed, if I have 1 Joule (unit of energy) in my pocket and if this Joule is indestructible, then it must have been there always. Logical, isn’t?
  • Others want a universe with a supernatural beginning, which would be a proof of the existence of God. They will therefore claim that if the Big Bang was the beginning [1], then it could not have been natural. Otherwise, the energy the universe contains today would have suddenly pop up at the Big Bang, violating the conservation of energy. Therefore, the beginning must have been supernatural. Logical, isn’t?

The problem is that the law of conservation of energy, sometimes called “the first law of thermodynamics”, does not always hold.

Picture a photon undergoing redshift as it travels through space. Its wavelength goes down, together with its energy. Question: where does this energy goes? Answer: nowhere. It is lost. Let’s see what happens.

Energy conservation: when it fails

What I am about to tell is not revolutionary at all. It’s about 200 years old. If it’s surprising, it’s simply because it takes a few years of college to hear about it. If doubt persists, you can always watch Leonard Susskind, Stanford big shot, telling the exact same thing to his students.

All known laws of physics have their limits. That is, circumstances where they will stop making predictions that fit reality. Fluid mechanics doesn’t like it when it’s too small. Newton’s laws don’t like it when it’s too fast or too small. Etc.

And the law of conservation of energy, what is its limit? Well, energy conservation doesn’t like change. What does it mean? Simply put, it means that if an experiment done yesterday gives the same result as if done today, then energy is conserved [2]. It’s called “time invariance”.

So yes, energy conservation relies on an assumption, too.

Obviously, the time invariance assumption is almost always met. Your cellphone, 24/7 experiment, works the same today than a month ago. Yet there is an “almost”. To understand it, we just have to imagine a situation, or a time, where doing an experiment yesterday cannot give the same result than today.

An example? The moments that followed the Big Bang, precisely. At this time, the universe is expanding rapidly. Try to reproduce today an experiment made yesterday, when all the dimensions of your lab are doubling every day! If space itself does not hold in place, goodbye time invariance… and goodbye energy conservation. If energy is conserved in the experiments conducted nowadays, it is because on their scale, the expansion of the universe, which indeed keeps on going, is completely undetectable [3].

The law of energy conservation is capricious. I’m afraid it slips away when some need it most.


[1] I won’t even discuss the fact that the Big Bang may not have been the beginning.

[2] Less simply put, it means that if the Lagrangian of your system does not explicitly depend on time, then energy is conserved. On this topic, and many others, I strongly recommend the discovery of the marvelous Noether’s theorem.

[3] And in fact, inexistent, as proved by Einstein and Strauss in 1945.

A collapse is possible

Translated from “Un colapso es posible”, published in the Spanish journal Acontecimiento n. 138, 2021, pp. 10-12.

I don’t know what André Malraux meant by “The 21st century will be spiritual, or it won’t be”. What I do think is that the 21st century could be the one of the collapse of our civilization, which of course does not prevent it from being spiritual.

I am used to explaining this in a four-months college course. Summarizing it in some 1000+ words without looking like a lunatic announcer of the apocalypse, is an interesting challenge. I will be as synthetic as possible, perhaps to the detriment of style.

What is the problem?

80% of the world’s energy comes from fossil fuels (oil, gas, coal). A stable percentage for decades. When we burn them, these fuels emit greenhouse gases like carbon dioxide (CO2). In the atmosphere, they act like a blanket: they heat up. As a result, the global temperature has increased by about 1 degree (Celsius) in the last 100 years. Under a business-as-usual scenario, it could increase 2 or 3 degrees more during the 21st century. Minus 4, it’s an ice age. So plus 2 or 3 would mean a planet where billions of people would just have a hard time to live. The challenge of the 21st century is to bring this 80% of fossil fuels down to 0% in the next 50 years.

Why is it very difficult to solve?

Clothes, food, computer, car, chair, desk… everything I use requires energy for its production, its transport, its operation. The heart of our civilization beats with oil, gas, coal… and their emissions. According to the International Energy Agency, they fell 5.8% in 2020, due to COVID-19. And we all saw what it cost. Well, achieving zero emissions in 50 years means such a reduction every year, for the next 5 decades. Here are a few reasons why achieving this is a considerable challenge.

  • Replacing fossil fuels with “green” sources is not easy, even materially. To supply the world’s energy consumption, it would be necessary to cover two Spains with solar panels. Or fill up twenty Spains with wind turbines. This is why we started with fossil fuels. They are more practical. The other sources are much less so, be it for the room they require. We did what children do when they eat: starting with the cool dishes. Broccoli always come last.
  • If there is too much CO2 in the atmosphere, why not extract it? There is a technology that achieves just that from solar energy. It is called a tree. How many do we need? A forest as large as Spain contains around 1 year of global CO2 emissions. So, to suck up a year of global emissions, you need to plant 1 Spain of trees, and of course wait for it to grow. Since it’ll take a few decades to do so, it will take just as long to absorb your single year of emissions.
  • The energy transition has only just begun. Worldwide, sources such as solar, wind or geothermal, generate less than 2% of production.
  • Clean energy production is growing. But production from fossil sources has grown 4 times more since 2000. The world is like a patient on diet who eats 100 more grams of vegetables… and 400 more grams of Nutella.
  • Speaking of diet, I wish there were few fossil fuels left. Thus, we would be obliged to reduce their exploitation. But no. There is a lot of coal left, for example. Regarding its need to cut fossil fuels, the world is like a patient who must go on a diet in a delicatessen.
  • When looking at how global energy consumption is shared, a bad surprise comes up. There is no dominant activity. Hopefully, for example, transport used 80% of our energy. We would then know that we can cut emissions by 80% by decarbonizing transportation. But no. Transportation represents only 14%. In other words: if all the planes, cars, trucks, motorcycles in the world turned green tomorrow, we would only gain 14% of emissions. The whole industry set green? Minus 21%. All green electricity production? Minus 25%. All buildings energetically carbon neutral? Minus 7%. There is no public enemy number 1. There are several.
  • An energy transition takes about 50 years, even when stimulated by the market.
  • It is not the western countries that are raising emissions. These ones have not increased in the last 30 years. It is the developing countries that push emissions up. An Indian, for example, uses 4 times less energy than a Spaniard. But he/she wants to reach the Spaniard’ standard of living. And achieving it is a matter of energy, that is, for now, a matter of emissions.
  • Some climate science to finish. So far, we were in the “easy” part. Even Exxon got it right… in 1982. More CO2, more temperature, and that’s it. We are now entering a climate zone where anything can happen. For example, the permafrost, the permanently frozen layer of soil in northern Russia or Canada, is thawing. Doing so, it releases methane, another greenhouse gas. These emissions then generate more warming, which in turn generates more thawing, generating more emissions, etc. Passed a certain threshold of heating, the vicious circle can be activated. If that happens, permafrost emissions will skyrocket, regardless of what we’re doing, until it has released all the methane it contains. Now, eight more vicious circles have been identified. They are interconnected, so that triggering one can trigger others. Their activation thresholds are difficult to pin down, but several scientists believe that we are getting closer.

So, “Foutu pour foutu?” [1]

This doesn’t look good. In fact, one just has to read authors like Joseph Tainter or Jared Diamond to see that the collapse of a civilization has nothing exceptional historically.

Some say that if Spain were to bring its emissions down to 0 tomorrow, the world’s emissions would drop by only 0.6%. They are right. The possibility then arises to conclude, “Why should I do anything at all if everything depends on the Chinese or the Indians? “Foutu pour Foutu”, give me my SUV!”.

Although I understand such an attitude, I think it is deeply flawed. It loses sight of the fact that global warming is only a symptom. A symptom of a deeply unethical attitude towards nature.

Nobody, when looking at a forest, thinks, “I would cut this all and put a huge parking there”, or when discovering a seabed, “I wish there were plastic bags here” [2]. However, this is what humanity has been doing for millennia in its understandable desire to live better and better; that’s why the problem is complicated.

Global warming is only a symptom of a deeper evil: the use and abuse of the earth as if it were a tissue. When we were 100 million, it was not so perceptible. With almost 80 times more people, the consequences are catching up with us.

“Foutu pour Foutu”, give me my SUV! “, comes to say that I can be a jerk on the Titanic. Quite the opposite. It is about deciding to be an angel, even on the Titanic, regardless of the consequences, in the same way that no one says “I love you” to a loved one to put an end to the Israeli-Palestinian conflict.

What’s that you say? Hopeless? -Why, very well!-
But a man does not fight merely to win!
No-no-better to know one fights in vain!

Edmond Rostand, Cyrano de Bergerac, Act 5, Scene 6


[1] “Foutu pour foutu” is a colloquial French expression. It means something like “ruined for ruined.” It is also the title of a remarkable documentary made by 2 young French people that can be viewed for free here (in French).

[2] There are plastic debris in the deepest trench in the world, the Mariana trench. Human footprint in the abyss: 30 year records of deep-sea plastic debris, Marine Policy, 96, 204, 2018.

Science always questions itself? Well, no.

  • Do you think the sun might not rise tomorrow?
  • Do you think your GPS might not work tomorrow because of a change in the laws of nature (and not because of a breakdown) ?
  • Do you shun surgery for fear that the laws of physics that govern the electronic devices in the operating room, might change during it?
  • Do you avoid airplanes only for fear that the laws of fluid mechanics may change during the flight?

If you answered “no” four times, then you trust the laws of nature enough to entrust your life to them. So do I. And so do all the people I know.

Indeed, the sun will rise tomorrow “because” of Newton’s laws (conservation of angular momentum). The same Newton’s laws dictate the equations of fluid mechanics ruling the flight of your airplane, and in the absence of damage here or there in a satellite, your GPS will keep guiding guide you tomorrow if electromagnetism, quantum mechanics and general relativity are still the same.

What do we mean then when we say “science always questions itself”?

It seems to me that we are eventually only talking about scientific issues that are not yet solved. We are certainly far from the last word on the mysteries of dark matter, dark energy, the origin of the universe, high temperature superconductivity, quantum gravity, etc. So many areas where, for sure, “science can completely question itself”. For example, it is quite possible that in 100 years we will no longer talk about dark matter. Here is, for example a list of more than 2,000 articles that mention an alternative.

As for electromagnetism, quantum mechanics or general relativity, it is precisely because science no longer questions them within their respective range of validity (the nuance is paramount), that industry seized them to make technological toys… that we would not buy if their operating principles could be “questioned”!

Can you imagine buying a device with a sticker on the box that would say

Warning, for unknown reasons, this device may not work tomorrow

Me neither… Seems we both admit “settled science ” definitely exists.

So, “science always questions itself”? No, not necessarily. For the contrary, read Barjavel.