Pi Day and Einstein

Einstein biographer Walter Isaacson celebrates Pi Day with a podcast about the genius of Einstein.

His main point is that Einstein's 1905 papers on light and relativity were each a revolutionary quantum leap that was independent of previous work and not properly understood or appreciated by experts at the time. The truth is more nearly the opposite.

The podcast credits Einstein with the original notion that light is both a wave and a particle. [at 6:07] No, it was Planck in 1900 who proposed that light was a wave, but emitted and absorbed discretely, and that is much closer to the modern view in quantum mechanics. Einstein opposed that modern view at every opportunity.

Then it says Planck, Lorentz, and Poincare were all working on physics related to relativity, and Einstein makes the big disconnected leap. Furthermore he says the other guys read the paper, and still don't quite get it.

Nonsense. Planck understood Einstein's paper, and immediately wrote a paper on it. Lorentz lectured on relativity in 1906, and correctly explained how Einstein's paper was just a minor embellishment on his own ideas.

What we know as special relativity today comes mainly from Lorentz's 1895-1904 work and Poincare's 1905 paper. Poincare had the spacetime geometry and Einstein did not. Einstein did not understand Poincare's paper until at least 1908.

These points are all detailed in How Einstein Ruined Physics, and on this blog.

The present is real, the past is gone

Brian Greene has released his World Science U special relativity course, with and without the math. It is slick, free, and appears to be well explained.

He falsely credits and idolizes Einstein, but probably has not read my book, How Einstein Ruined Physics.

In the module on "The Reality of Past, Present, and Future", he makes some faulty philosophical comments about time, that I recently attacked. After explaining some of the difficulty with relativistic simultaneity, he concludes:

So what this collectively tells us is that the traditional way we think about reality -- the present is real, the past is gone, the future is yet to be -- that is without any real basis in physics. What we are really learning from these ideas is that the past, the present, the future, are all equally real.

So does relativity really require us to give up this basic intuition about time? I say no.

The essence of Greene's problem can be understood with pre-relativistic causality. Suppose I am on Earth, an alien is on another planet, and we somehow come to agreement about time. For me, "now" means that I can affect events in the immediate future, and likewise for the alien. But I cannot affect things in the immediate future on the other planet, because anything I cause on Earth will take some time to get to the other planet. So while the alien and I may agree about the meaning of "now" as it relates to our local clocks and our notion of local causality, it will still be the case that I can affect my environment before the alien can, and the alien can affect his before I can.

Relativity makes this more precise by saying that causality is limited by the speed of light, and by giving formulas for how motion can de-synchronize clocks.

The essential point is that the present now makes sense for me, and I can cause changes in the future, but only nearby, because there is no action-at-a-distance. Technically, I can affect my future light cone.

The alien might agree on what now means, and he can affect his future light cone, but my future light cone is different from his.

Thus Greene's conclusion above is entirely wrong. Our traditional notion of time, with its distinction between past, present, and future, does have a real basis in science. I explain this below in terms of time counterfactuals.

While Greene's explanation of relativity is mathematically correct, and his paradoxes might be confusing, the world would be more confusing without relativity. Suppose that my present now was dependent on the whole universe in the immediate past, and my actions affect the entire universe in the immediate future, without any time lag. That alien on another planet could do something to affect me a second later, and I could respond, to affect him in another second. That alien would never make sense of his world because some capricious intelligence in another galaxy could be interfering with his experiments. Relativity puts a lid on that, and ensures that local causes have only local effects.

Relativity gives us more reason to believe that we live in the present, not less. Time is more intuitive when causality has relativistic limits.

Others disappointed with the Bruno multiverse

I am still annoyed at the Cosmos TV show. Neil deGrasse Tyson had previously refused to join the atheist anti-religion cause, so I am surprised that he got conned into the Bruno multiverse nonsense.

One review says:

I re-watched the original Cosmos a few years ago, some of the episodes with my kids. They are still fun to watch, but I realized something in seeing them again. Sagan made mistakes. Big mistakes, as with Hypatia and the burning of Library of Alexandria ...

I was looking forward to the new Cosmos.  But I saw the trailer and Bruno getting burned, so I knew it was just going to be more of the same. but I didn’t know how much more of the same it would be. ...

I think they chose Bruno because somebody said Galileo was getting a bit old, let’s find another scientist that religious people persecuted. Then they hit a problem. There really are not that many besides Galileo. In fact, there aren’t really any more good examples, at least not in Catholic Europe, where the Church over the ages was stuffed full of scientists and scientists-wannabes, ...

Problem was, Bruno was not much of a scientist, he was a weird mystic hermeticist who liked to insult people.

That's right. If the Catholic Church were really so anti-science and anti-knowledge, couldn't they find a another example?

Salon explains:

And, of course, it is no accident that Giordano Bruno appeared in the first episode of “Cosmos.” Because whether or not Bruno himself was a scientist, there’s not a whole lot, besides their relative lack of access to killer barbeque tools, that differentiates the current crop of intelligent design advocates and Texas textbook revisionists and inheritors of the Moral Majority mantle from the shame and terror of the Holy Inquisition.

A "longtime Giordano Bruno fangirl" writes:

His belief in an infinite universe, reflecting the infinite glory of God, got Bruno shunned and exiled from country after country. He grew impoverished and largely friendless, but refused to recant. Eventually Bruno was imprisoned by the Church, and burned at the stake in 1600–10 years before Galileo announced his first observations that confirmed Copernicus was right.

It’s a powerful, tragic, and cautionary tale, right?

Meet the Real Giordano Bruno

That depiction in the new Cosmos matches the standard textbook story of Bruno, but it is misleading and in some ways downright wrong.

Hank Campbell points out that Sean M. Carroll is a fan of the Bruno multiverse, and writes:

Then suddenly we get a claim that Giordano Bruno is responsible for the concept of the universe - because he read 'banned' books. Lucretious wasn't science - there was no scientific evidence for his claim that wind caused earthquakes or worms spontaneously generated - it was philosophy, and his book was not rare in 1600 AD, people were also not martyred for reading it, and yet we get told a philosophical belief in infinity was what got Bruno into trouble.

It's an immediate disconnect for people who know science history because it smacks of an agenda. I instead object because it is flat-out incorrect. To claim that Bruno promoted the concept of the universe, a "soaring vision", despite persecution, while simultaneously being hired over and over by the institutions we are told were oppressing him, makes no sense. That segment of the show makes it sound like he was a devout Christian tormented by reason rather than what he was - a cultist who engaged in confirmation bias to pick and choose anything that matched his beliefs.(1)

Bruno's "science" was never mentioned during his trial, he was on trial for being a cult worshiper. He only took up the cause of Copernicus because he believed in the Egyptian god Thoth and Hermetism and their belief that the Earth revolved around the Sun, not because he had perceived anything radical. Galileo rightly dismissed most of Bruno's teachings as philosophical mumbo-jumbo. Bruno was only revived as a 'scientist' and a martyr for science by anti-religious humanists in the 19th century.The church didn't even bother to ban his writing until well after he was dead.

Bruno was not a martyr for science, the way the cartoon in Cosmos: A Spacetime Odyssey alleges, he was a martyr for magic. He actually was a heretic.

Salmons writes:

Two reactions: 1) That’s not the real story. 2) With no evidence either way, how does holding to one superstition over another make Bruno an example for science?

On the first reaction, the Church didn’t overly care that Bruno believed in a heliocentric model of the solar system (link). They didn’t overly care in his belief of Copernicus’ views (many people did…even the Gregorian Calendar, adopted years earlier in 1582, was based on Copernicus’ observations).

A Catholic site writes:

The ignorance is appalling. “The Catholic Church as an institution had almost nothing to do with [the Inquisition],” writes Dayton historian Thomas Madden. “One of the most enduring myths of the Inquisition,” he says, “is that it was a tool of oppression imposed on unwilling Europeans by a power-hungry Church. Nothing could be more wrong.” Because the Inquisition brought order and justice where there was none, it actually “saved uncounted thousands of innocent (and even not-so-innocent) people who would otherwise have been roasted by secular lords or mob rule.” (His emphasis.)

As for Bruno, he was a renegade monk who dabbled in astronomy; he was not a scientist. There is much dispute about what really happened to him. As sociologist Rodney Strong puts it, he got into trouble not for his “scientific” views, but because of his “heretical theology involving the existence of an infinite number of worlds—a work based entirely on imagination and speculation.”

Thomas L. McDonald writes:

Before we begin, just who was Bruno?

He was a Dominican friar who lived from 1548 to 1600. He was not a scientist, conducted no experiments, looked through no telescopes, and wrote no scientific works. He was a mystic, a radical heretic, and an occultist. He abandoned Christianity in favor of Hermeticism (believed to be derived from ancient Egyptian wisdom) and magic.

Giordano Bruno, who enjoyed the patronage of King Henry III after abandoning his monastery, is shown as a poor and wretched drifter.

His place in a documentary ostensibly about science is inexplicable. Actual scientists worked on similar ideas, but only Bruno is called out in a ten-minute long segment.

The question is: why?

The narration begins by telling us that in “1599 everyone knew the sun, planets and stars were just lights in sky revolving around the earth.” It was “a universe made for us.” And “there was only one man who envisioned an infinitely grand cosmos.”

We’re barely seconds into this farrago and we have our first lie.

“Everyone” knew the earth was the center of the universe?

Wow, who’s going to tell Copernicus? Kepler? Stigliola? Diggs? Maestlin? Rothmann? Brahe? All of them believed in models of the cosmos that were not considered orthodox, and lived at the time of Bruno. All of them escaped the fire, and indeed weren’t even pursued by the Inquisition. Right here we have the major lie at the heart of modern anti-religious scientific propaganda: the war between faith and science.

We’re supposed to just assume this ignorant backwards world of the past hates smart people. Tyson himself says it matter-of-factly: “How was [Bruno] spending New Year’s Eve [in 1599]? In prison, of course.”

Of course! Because that’s what the Church does to smart people! Bad church! Bad!

Next: “This was a time when there was no freedom of thought in Italy.”

God, I really hate it when historical illiterates try to read church history through a modernist lens.

Casey Luskin attacks the Cosmos materialist agenda, and gives examples of modern scientists who are supposedly persecuted.

I don't really mind the atheist materialist agenda, if the scientists would stick to legitimate facts and science. But this is an attempt to promote completely unscientific reasoning in favor of a foolish multiverse belief system, both by Bruno in 1600 and by silly publicity seekers like Sean M. Carroll today.

Even the New York magazine review sees the show as left-wing anti-religion propaganda:

This new Cosmos is not so easygoing. The post-1980s rise of the Evangelical right wing created a hostile environment for ­science and science teachers. Recently, Louisi­ana governor Bobby Jindal became the latest conservative politician to ominously warn of a war on religion, even as certain public-school districts allow the discussion of creationism to undermine evolution in classrooms — a development that would have been unthinkable 30 years ago. Bill Nye, the former host of Bill Nye, the Science Guy, recently took part in an evolution debate with Ken Ham, ...

The new Cosmos feels like a pushback against faith’s encroachments on the intellectual terrain of science.

No, the Louisiana schools are not teaching creationism, and debates over evolution have gone on for over a century. Faith or religion is not interfering with science in any significant way. Not in the Western world, anyway. Has religion ever censored a scientific publication? Gotten an atheist fired? The mainstream Christian and Jewish religions have no quarrel with science at all. I realize that some religious folks have some beliefs contrary to modern science, but they have no power over the scientific community whatsoever.

I don't see why it is any better to teach unscientific multiverse ideas than to teach unscientific theological ideas.

I wrote a book on how physics has lost its way, and idolizing the Bruno multiverse is an excellent example.

Update: A reader complains that I have quoted an intelligent design advocate, and that a Discovery Institute official has admitted that there is anti-religious opposition to intelligent design.

I quoted a Catholic and an atheist also. I credit them all for pointing out historical and scientific errors in a popular TV show. I understand that some people are motivated to defend religion, while others are motivated to attack it. One thing I have liked about Tyson is that he is a science enthusiast, without getting bogged down into political or religious battles. I am happy to credit someone with a different view if he is correct about something.

Update: Leftist-atheist-evolutionist Jerry Coyne organized a campaign to censor a class that mentioned intelligent design and praised the Ball State U. president for saying "Intelligent design is overwhelmingly deemed by the scientific community as a religious belief and not a scientific theory." Then he attacks Casey Luskin for saying that religion had something to do with the issue. I don't mind criticism of religion, but the new Cosmos and Coyne's blog are just weirdo religious hatred. And my quoting Luskin is not an endorsement of his religious views, as I don't even know what they are.

Update: Also unhappy with the Cosmos treatment of Bruno is the pro-evolution anti-intelligent-design site NCSE, saying:

As our own Peter Hess observed, the first episode took a long detour from its history of the cosmos to tell a cartoonish history of Giordano Bruno. The intent seems to have been to revive the long-debunked and historically-discredited metaphor of warfare between science and religion.

The site is very happy with the "somewhat spiritual defense of evolution" in the second episode.

Strings compared to quantum computation

Now that Scott Aaronson has banned the leading defender of string theory from his blog, he gets the embarrassing question:

A layman question: Regarding string theory, is it really true that there’s a total dearth of any testable empirical predictions? At least for the foreseeable future of our experimental reach?

Aaronson answers:

What I think is uncontroversial is this: there are various phenomena that, if they were observed (either at the LHC or in cosmology), would provide an enormous boost to string theory. The most important and plausible of those is supersymmetric particles; but there are also more exotic possibilities, like large extra dimensions and cosmic strings. The central problem is that, if those phenomena are not observed (as indeed they haven’t been, despite searches for them), that doesn’t falsify string theory at all. For it’s perfectly compatible with string theory that these phenomena would only show up at much higher energies than are currently accessible to us.

This is like saying that there are experimental findings that would support telekinesis, and they are never seen, but that's no reason to doubt telekinesis.

Mathematician Greg Kuperberg tries to answer:

There is a “dearth” of *directly* testable empirical predictions in string theory, but it’s misleading to use the word “dearth”. It’s been acknowledged from the beginning that it’s difficult to make any new predictions from any reasonable model of quantum gravity. What theorists can do, however, is offer a better explanation of the evidence that already exists. That is the main driving force of string theory: How to keep quantum mechanics and general relativity from contradicting each other; and how to keep the Standard Model of particle theory from contradicting itself. String theory is an incomplete effort to do that, but it is also “the only game in town”. It is the only known attempt at quantum gravity that isn’t in the hospital and close to flatlined. And, resolving the Standard Model of particle physics would be extra icing on the cake.

Of course, any kibbutzer can talk about the problems of “theory without experiment”. But the truth is that the best theorists can get pretty far with just parsimony and logical consistency. Both general relativity and cosmological inflation — both of which are cousins of quantum gravity and string theory — were correctly developed before any help came from experiment. In the case of inflation, 20 years before good experimental confirmation.

Indeed, quantum computation has the same intellectual feature. Theoretical quantum computation gets a little help from experiment, but really hardly any. It is for the most part a compelling extrapolation of existing physics.

That is, string theory needs no experimental evidence because there is no known observational conflict between quantum mechanics and general relativity. And while string theory is not consistent with any known physics, the competitors are not either, and are not as fashionable. Just like theoretical quantum computation, which also has very little known relevance to experiment.

As a historical argument, it is not true that general relativity was "correctly developed before any help came from experiment." First, special relativity arose directly from experiment, as expressed at the time:

The views of space and time which I wish to lay before you have sprung from the soil of experimental physics, and therein lies their strength. They are radical. Henceforth space by itself, and time by itself, are doomed to fade away into mere shadows, and only a kind of union of the two will preserve an independent reality. – Hermann Minkowski, 1908

Second, general relativity also follows from those same experiments, in spite of the mathematical difficulty. Lubos Motl explains:

While it's true that special relativity is a limit of general relativity obtained for gravitational fields going to zero, the actual "hierarchy of power" is the opposite: general relativity is just one application of special relativity – the incorporation of the gravitational field in a special-relativity-invariant way. While general relativity is arguably the prettiest (and geometrically most non-trivial) classical application of the rules of special relativity, in principle it is on par with Yang-Mills theory or any other (special) relativistic field theory.

Third, Einstein was driven to explain Mercury's orbit anomaly, following Poincare's relativistic partial explanation. So the development of general relativity was driven by experimental evidence, just like all the other great scientific theories.

Cosmological inflation has not really been confirmed, and remains just a loose collection of ideas for how the early universe might have expanded. There has been no Nobel prize for it.

I am a stickler for the history of relativity because it is always being misrepresented to justify bad science.

The clutches of the thought police

The first episode of the much-hyped TV series Cosmos: A Spacetime Odyssey was broadcast last night, and it made a big deal out of Giordano Bruno being a "martyr" in 1600 for expressing his expansive view of the cosmos. It did admit that he was not a scientist, and just made a "lucky guess" because he had no evidence.

His lucky guess was that the universe had an infinity of worlds like Earth. The show gives the impression that his guess was true, even if he lacked the evidence. But it is not. The overwhelming view of cosmologists today is that there are only a finite number of worlds in the universe.

He [Bruno] could not keep his soaring vision of the cosmos to himself, despite the fact that the penalty for doing so in his world was the most vicious form of cruel and unusual punishment. ... It wasn't long before Bruno fell into the clutches of the thought police.

No. Bruno's heresy was that he was a Catholic monk who denied the divinity of Jesus Christ.

Our entire universe emerged from a point smaller than a single atom. Space itself exploded fire launching the expansion of the universe, and giving birth to all the matter and all the energy we know today.

This is not helpful. I accept the Big Bang theory, but there is no real scientific evidence that the start was a point smaller than an atom. A naive extrapolation leads to that model, but the universe could have started with something the size of the Earth, for all anyone knows.

Anyway, we did not get an infinite number of worlds from a point smaller than an atom.

There is a lively debate between Scott Aaronson and Lubos Motl over whether P=NP. Aaronson eventually goes into a name-calling rant, and bans Motl from commenting on the blog for 3 years.

Aaronson has also banned me from his blog, because he was irritated about my skepticism of the possibility of quantum computers. Motl is his usually obnoxious and over-opinionated self, and he has called me names as well. Aaronson is like the Roman Inquisition, while Motl is like Bruno.

At the core of the dispute is the difference between math and science. P=NP is an open mathematical question, and until it is proved true or false, both outcomes must be considered possible. Aaronson's point is that the question should be considered settled under the lower standards of science, by analogy to the evidence for how green and yellow frogs might be separate species. Both Aaronson and Motl have weak arguments.

Aaronson is a typical academic knee-jerk liberal, and people like that usually despise political conservatives like Motl who can back up their opinions.

I once credited Aaronson with a plausible argument against P=NP, but I am doubtful about his frog argument:

He also argues that P != NP because verifying a proof ought to be much easier than finding an original proof. That is a reasonable argument. If it turns out that P = NP, then we would have to revise a lot of what we think about complexity, so we should be very skeptical of any such claim. Likewise we should be skeptical about quantum computing.

While my intuition says that there can be no efficient algorithm to solve NP complete problems, there could be a very inefficient polynomial-time algorithm, thereby allowing P=NP.

Maybe I should have expressed my objections to quantum computing as a parable about frogs. Instead of the evidence and arguments, I could have told about a naked emperor who gave grants to find a purple frog, and everyone always reported great progress even tho no one ever found a purple frog.

Update: Jennifer Ouellette, wife of cosmologist Sean M. Carroll, reviews Cosmos in the LA Times:

And Tyson adds a 21st century twist by invoking the multiverse: the notion that our universe might be just a bubble among bubbles in a vast infinite sea of universes. That’s the kind of notion that used to fall firmly into crackpot territory – or make for bestselling science fiction novels -- but is now taken quite seriously by many cosmologists, even if it’s not (yet, if ever) a testable hypothesis. And it’s the perfect set-up to a charming animated sequence relating one of my favorite stories from the history of astronomy.

Maybe taken serious by popularizers who promote fringe ideas like her husband. If an idea is never testable, then real scientists do not take is seriously as scientific.

Giordano Bruno was an Italian mystic who was among the first to adopt the Copernican cosmology at a time when doing so could prove hazardous to your health. In fact, he went one step further and suggested – based on a vision when he was 30, perhaps because he read the forbidden text of Lucretius, "On The Nature of Things" – that the sun and its planets were just one of millions of other solar systems in an infinite universe. It made sense to Bruno. God was infinite, he reasoned, so why shouldn’t the universe he created be infinite too?

The Catholic Church begged to differ and excommunicated him. So did the Protestant church. ...

But as Tyson points out, the dude was right. Sure, it was a lucky guess, and he wasn’t really a scientist, but “It gave others a target to aim at, if only to disprove it.”

No, the dude was wrong. Where is the Inquisition when we need it?

This show could have told the story of any of 1000s of great scientists who made observations, formulated a hypothesis, did an experiment, and then correctly analyzed the data to come to a valid conclusion. Bruno did none of that. It is crazy for this first Cosmos episode to focus on idolizing someone who was so contrary to the scientific method.

Supersymmetry is dead

Ethan Siegel writes:

Have you ever wondered why the masses of the fundamental particles have the small values that they do, compared to, say, the Planck scale? Whether the fundamental forces all unify at some high energy? And whether there's a natural, compelling particle candidate for dark matter? Well, in theory supersymmetry (or SUSY, for short) could have solve all three of these problems. In fact, if it solves the first one alone, there will be definitive experimental signatures for it at the Large Hadron Collider. Well, the LHC has completed its first run, and found nothing. What does this mean for theoretical physics, for SUSY in particular, and what are the implications for string theory?

Supersymmetry started around 1970, along with various grand unified field theories. Theoretical physics started to diverge from what was observed, to how theorists thought that the universe ought to be. String theory followed, and it was almost entirely dependent on SUSY.

Physicists praised SUSY as correct in the same way that they say the Copernican model should have been accepted in the 16th century. It solved several independent theoretical conundrums, and just seemed more natural.

The trouble with SUSY is that it predicts new particles pairs with the known quarks, leptons, and bosons. None of these has been found. It is possible that they are all of such high energy that we will never find them, but then they are not so natural. To really solve the problems, we should have seen them. A lot of physicists have invested their whole careers on a wrong idea.

The above story is from May 2013, but is is only more true today:

For some insight into the current concerns of particle theorists, you can watch some of the videos at last week’s KITP conference. In particular, there’s Matt Strassler’s talk, where he got all Peter Woit and argued that “one could make the argument” that not seeing SUSY (or anything else stringy) at the LHC “would be significant circumstantial evidence against string theory as a description of nature” and that just seeing the SM at the LHC would be “circumstantial evidence against effective quantum field theory as a complete description of known particle physics”. This got him an argument from Gross about his insufficient enthusiasm for a 100 TeV collider. Gross then also got all Peter Woit, arguing that the failure of the “naturalness” argument for new physics was no big deal since it wasn’t a very good argument to begin with (I get all sorts of grief when I do this..).

You can be sure that physicists will find arguments for building a 100 TeV collider, at a cost of $20B or more.

Counterfactuals: Time

Time is what distinguishes the past from the future. The chief intuitive difference is that we remember the past, and we cause the future. Time marches forward, and as we cause events, they become the history that we remember.

While this view of time seems obvious to a small child, there is an opposite view that the present flow of time is just an illusion. That view is sometimes called block time, and its roots go call the way back to the ancient Greek philosopher Parmenides. Albert Einstein and other smart people have subscribed to such a view, and even claimed that relativity theory requires it. A 2010 SciAm article says that many physicists argue that there is no such thing as time, and explains:

As you read this sentence, you probably think that this moment — right now — is what is happening. The present moment feels special. It is real. However much you may remember the past or anticipate the future, you live in the present. Of course, the moment during which you read that sentence is no longer happening. This one is. In other words, it feels as though time flows, in the sense that the present is constantly updating itself. We have a deep intuition that the future is open until it becomes present and that the past is fixed. As time flows, this structure of fixed past, immediate present and open future gets carried forward in time. This structure is built into our language, thought and behavior. How we live our lives hangs on it.

Yet as natural as this way of thinking is, you will not find it reflected in science. The equations of physics do not tell us which events are occurring right now — they are like a map without the “you are here” symbol. The present moment does not exist in them, and therefore neither does the flow of time.

That view of time certainly is reflected in science, and in my opinion, adopted by all sensible people. There is not a shred of scientific evidence against it. Most of the fundamental equations of dynamics are expressed directly in terms of the flow of time. I quote the article to point out that more than one view of time is possible.

The scientists who deny the flow of time will typically argue that the fundamental laws of nature are deterministic and reversible, and so the progress of time is an illusion and we have no free will to affect the future. Many argue for retrocausality, as they say the future determines the past as much as the past determines the future. Some people also deny that we can speak definitely about the past, as they say that quantum mechanics allows for multiple histories.

Some argue that relativity is contrary to the flow of time, because time is just another dimension like the three spatial dimensions. That is even the consensus among philosophers. But the flow of time is essential to relativity, as every object travels along its world line into its future light cone. The dynamics of relativity, as well as other physics theories, use the flow of time.

Einstein was unhappy about the flow of time:

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. That this experience cannot be grasped by science seemed to him a matter of painful but inevitable resignation.

And also:

Three weeks before his death, in 1955, Einstein wrote, “People like us, who believe in physics, know that the distinction between past, present, and future is only a stubbornly persistent illusion.”

Hermann Weyl wrote in 1949:

The objective world simply is, it does not happen. Only to the gaze of my consciousness, crawling upward along the life line of my body, does a section of this world come to life as a fleeting image in space which continuously changes in time.

A recent paper on The flow of time in the theory of relativity demonstrates the confusion over alternate ideas of time:

When we consider any experiment related to the theory of [special] relativity, like the Michelson-Morley experiment (see, e.g., Møller 1955, 26-8), we can always describe it in terms of an intuitive notion of passage or flow of time: light is send through the two arms of the interferometer at a particular moment – the now of the experimenter –, and the process of light propagation takes time to occur, as can be measured by a clock calibrated to the adopted time scale.

However when we consider the theory, in particular focusing on its development in terms of the Minkowski space-time and its application using the Minkowski diagrams, we immediately became puzzled by the implications of the theory regarding our intuitive notion of time, and the passage or flow of time seems difficult or even impossible to ‘find’ in the conceptual-mathematical structure of the theory (see, e.g., Dorato 2010, 1-2).

Of course it is not really difficult to find the flow of time. If you understand how those experiments follow from the theory, then you have the flow of time.

The supposed problem is with "probabilism", which has been defined as the doctrine that "the universe is such that, at any instant, there is only one past but many alternative possible futures". There is also a technical problem that what one person perceives to be the present might differ from what another perceives. But that does not really affect the philosophical issue of time.

Without getting into the subtleties of relativity and quantum mechanics, I am adopting the commonplace view that time flows from the past (that we remember and is certain) to the future (that we cause and is uncertain). In philosophy jargon, I am following the A-theory of time and maybe presentism, instead of the B-theory and eternalism. As the ancient Greek Heraclitus said, it is impossible to step into the same river twice. As the above SciAm article says, how we live our lives hangs on this structure. I want to explain how this view relates to counterfactuals.

Past events are definite, and cannot be changed. Hypothetical events are in the future, and may depend on our free will to choose courses of action. Counterfactual events are in the past, and did not happen. We cannot make them happen. What we can do is to discuss the causal effect of the counterfactual events.

Counterfactual events are always earlier in time than the hypothetical consequences. For example, the counterfactual might be that you jump off a cliff. The consequence is that you fall to your death. Because you understand this causal reasoning, you don't jump off the cliff.

Free will is the idea that you can voluntarily eliminate counterfactuals from your life. At any given time, there could be several counterfactuals in addition to whatever you actually do at that time. If you have the free will to choose what you do, then you are making the decisions that prevent those counterfactuals from happening.

Thus counterfactual thinking is how people imagine alternatives to reality, and make decisions. As such, psychologists and others have attributed poor decision-making to a faulty assessment of counterfactuals. For example, someone might refuse to fly in an airplane because of an exaggerated opinion of the risk of a plane crash.

Again, the Einsteinian physicists and B-theory philosophers reject all of this. Their reasons are more religious than scientific. There are no experiments contrary to the intuitive flow of time, and no generally accepted theory that is inconsistent with it. Their view is deficient, because they cannot grasp counterfactuals.

Update: N. David Mermin recently wrote a paper on trying to escape the B-theory of time:

Rudolf Carnap succinctly stated the problem of the Now in his report of a conversation with Albert Einstein:7 “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. That this experience cannot be grasped by science seemed to him a matter of painful but inevitable resignation.”

Mermin says that this is "a longstanding puzzle in classical physics." The problem disappears with a suitable positivistic philosophy, altho Mermin does not exactly express it that way. You just have to rid yourself of warped Einsteinian thinking.