Dream a little dream of me

One of the more terrifying concepts to arise out of physics is the idea of the Boltzmann brain.

The Boltzmann brain was first postulated by, and is named after, the Austrian physicist Ludwig Boltzmann, who also discovered the mathematical laws governing entropy.  He was one of several scientists who contributed to the idea of the "heat death of the universe" -- that because of the Second Law of Thermodynamics, eventually the universe will reach a state of zero free energy and maximum entropy.  After that -- quantum fluctuations and random motion aside (more on that in a moment) -- the universe will be a thin, more-or-less uniform, cold fog of particles, in which nothing else will happen.  Forever.

Boltzmann committed suicide at age 62.  I'm almost sure his research had nothing to do with it.

In any case, the Boltzmann brain idea came up when he was pondering the state of the universe following the heat death, which (by current models) isn't going to happen for another 10^100 years, so don't fret if you have unused vacation time.  The question that puzzled Boltzmann most was what got the universe into a low-entropy state to begin with; after all, if you see a ball rolling down a hill, its behavior isn't at all strange, but it leaves unanswered the question of how the ball got to the top of the hill in the first place.  He came to the conclusion that random movement of the particles in the fog could, given long enough, create low entropy regions just by chance.  In fact, given the infinitely long time he postulated the heat death stage would last, any possible configuration of particles would show up eventually.

Interestingly, in the hundred-plus years since Boltzmann came up with all this, scientists are still trying to work out all the implications of this.  A 2004 paper by Sean Carroll and Jennifer Chen looked at the question of how long it would take for a random, uniform, maximum-entropy universe to spontaneously generate a second Big Bang -- and thus a new, low-entropy universe -- through quantum fluctuations and quantum tunneling, and came up with a figure of 10^10^10^56 years.

Boltzmann, though, was more interested in smaller stuff.  He asked an unsettling question: was it possible, through random movement of particles, for them to come together in such a way as to form an exact copy of himself, with all of his thoughts and memories and so on?

His conclusion: once again, given enough time, it's not just possible, it's inevitable.  In fact, calculations have shown that we should expect such "Boltzmann brains" to outnumber all other sentient beings by a vast margin.

[Nota bene: keep in mind that Boltzmann died prior to the discovery of quantum physics; as Carroll and Chen discussed, adding in quantum effects actually increases the likelihood of these kinds of weird, accidental rearrangements.]

Now comes the kicker.  Suppose you yourself aren't an "ordinary" observer, but a "Boltzmann brain" -- a disembodied, and presumably temporary, sentient arrangement of particles, that happened to have the correct configuration to contain all the thoughts, perceptions, and memories you currently have.  Would there be any way for you to know?

The answer is almost certainly "no."  "I am confident that I am not a Boltzmann brain," physicist Brian Greene said.  "However, we want our theories to similarly concur that we are not Boltzmann brains, but so far it has proved surprisingly difficult for them to do so."

It bears mention that there could be some caveats here that might save us from this rather terrifying possibility.  Current studies of dark energy and the cosmological constant have a significant bearing on the ultimate fate of the universe.  If, as some recent research suggests, the strength of dark energy is decreasing over time, we might be in a universe destined not for heat death, but for a collapse that could reset the entropy content -- and, possibly, a subsequent rebirth.  But that is still very much uncertain, and the majority of physicists are still of the opinion that the expansion is going to continue indefinitely.

Boltzmann Brain World, here we come.

The topic comes up because scientists are still debating the implications of this -- and many of them trying to rule out the Boltzmann brain concept because it's so damned unsettling.  Just last week, there was a paper in the journal Entropy by David Wolpert, Carlo Rovelli, and Jordan Scharnhorst, called "Disentangling Boltzmann Brains, the Time-Asymmetry of Memory, and the Second Law," which considered the fact that just about all physical laws are time-reversible, yet our memories seem not to be.  This is, however, exactly what we would expect if we were Boltzmann brains, because if that were true, memory itself would just be an illusion, a present-moment effect caused by the random configuration of particles that give the ephemeral sense of a past.  Here's the passage from the paper that rocked me back on my heels:

Reasonable as the arguments just presented might be, in the abstract, how, concretely, can they hold?  How could we have all of our human memories concerning the past be fallacious?  How could entropy increase into our past rather than decrease, as required by the time-symmetric nature of all derivations of the Second Law that are consistent with the microscopic laws of physics?  How could it be that our memories are wrong? 

Such flaws in our memory would require some exquisite fine-tuning, that all the neurons in our brains happen to be in the state corresponding to particular memories, when in fact nothing of the sort is true.  Amazingly though, standard arguments of statistical physics tell us that it is almost infinitely more likely for this to be the case, rather than for entropy to continue to decrease into our past, as demanded by the Second Law.

I read this three times and I shuddered every time.

Thanks bunches, Boltzmann.  I'm sure I'll sleep just fine tonight.  If I actually exist, that is.  [Image is in the Public Domain]

So it can't be rigorously ruled out that we're disembodied brains in an entropic sea, dreaming a little dream of being people.  In this formulation, the Second Law of Thermodynamics is, in fact, time-reversible; entropy increases both into the past and into the future, even if our illusory memories make it seem like that isn't true.  We arose from random fluctuations, and flutter about for a while thinking we're real, then after a few moments subside back into the fog again.

And on that wonderful note, I'll leave you.  If you need me, I'll be hiding under my blankie, hugging my teddy bear.

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Life in the middle

I first ran into the fine-tuning argument around twenty-five years ago when I read astrophysicist Martin Rees's wonderful book Just Six Numbers, in which he looks at how a handful of fundamental constants -- the gravitational flatness of the universe, the strength of the strong nuclear force, the ratio between the strength of the electromagnetic force and the gravitational force, the number of spatial dimensions, the ratio between the rest mass energy of matter and the gravitational field energy, and the cosmological constant -- have combined to produce the universe around us.  One by one, he goes through each of them, and shows that if you changed them -- some by as little as one percent in either direction -- you would have a universe profoundly hostile to life, and (in come cases) one in which matter itself wouldn't be stable.

To a lot of people, this looks very much like someone superpowerful tweaked the dials to just the right settings, so that these constants have values that allow for stable, long-lived stars, complex chemistry, and -- ultimately -- life.  We don't yet know any underlying physics from which any of these could be derived; they seem to be, essentially, arbitrary.  For some people, this line of reasoning ends with, "ergo... God."

Well, I have two objections, and if you're a long-time reader of Skeptophilia, you probably know what they are.  First, there's that awkward little word "yet."  We don't yet know if these constants are constrained -- i.e., if their values are required to be what they are by some overarching principle.  There may be such a principle that we just haven't discovered, just as the properties of the elements seemed arbitrary until Mendeleev (and Bohr, de Broglie, Pauli, and others) came along and showed that there was an organizing scheme and an underlying set of physical mechanisms that made sense of it all.

My second objection is that of course we live in a universe that has properties that allow life.  If the universe didn't have properties that allowed life, we wouldn't be here to ask the question.  This formulation, called the Weak Anthropic Principle, more or less devolves into a tautology, a little like being puzzled about why organisms that require oxygenated air to breathe are found only in places that have oxygenated air.

The question, though, is not as facile as I'm perhaps making it sound.  There are a great many seemingly arbitrary constants in physics (physicists prefer the term free parameters), such why the fundamental particles in the Standard Model of Particle Physics have the masses they do.  

[Image is in the Public Domain]

Also unknown is why there are three "generations" of fermions and only one of bosons, why there are four fundamental forces, and why gravitation has (again, thus far) resisted all attempts to incorporate it into a Grand Unified Theory.

Some physicists have attempted to explain this messiness by saying that this is only one universe in a multiverse, and all the other universes have different properties -- in fact, all the possible combinations of parameters exist in a universe somewhere.  The problem with this is that it's an explanation that doesn't really explain anything.  We have no way of detecting those other universes, so what does it even mean to say they "exist?"  In my mind, this is no better than the "God-as-dial-twiddler" model.  In fact, it's worse; at least in the latter, there's an entity who cares enough about us to create a relatively hospitable universe for us poor slobs who are stuck inside it.

The reason this comes up is a new paper from physicist McCullen Sandora, that I found out about from Sabine Hossenfelder's physics news YouTube channel.  Called "Multiverse Predictions for Habitability: Fundamental Physics and Galactic Habitability," Sandora turns the entire discussion upside-down; instead of looking at the physical free parameters and asking why they are what they are, he asks the question, "What does the presence of life tell us about how the universe had to be?"

Sandora's intriguing conclusion is that "neat" universes -- ones with unified forces, few free parameters, and simple interactions -- are incapable of generating the complexity required for life.  Hossenfelder says:

The surprising result is that the idea that the fundamental forces are unified do badly. Well, at least I found that surprising, but the more I thought about it the more sense it made.  You see, a unified theory will in one way or another tie different parameters to each other.  Then, if you vary one parameter, you break several others at the same time.  

As a consequence, the more strongly different interactions are tied together, the more difficult it becomes to create life.  Most universes end up either short lived, empty, or chemically boring.  More flexible theories do better.  Theories where parameters can vary more independently produce a larger fraction of observer-friendly universes.  In other words, once you include the multiverse and selection effects, physics that is slightly messy beats physics that is mathematically elegant.

Hossenfelder herself has argued vehemently against using the criteria of "beauty" or "elegance" as the driver to find theoretical frameworks in physics; her excellent book Lost in Math: How Beauty Leads Physics Astray is one long plea to go back to an empirical basis for physics research.  (An especially egregious example is the long, expensive, and fruitless quest for supersymmetry, a postulated system that argues the existence of a "supersymmetric partner" for every particle in the Standard Model; a decades-long search has turned up exactly zero of these hypothesized partners.)

We humans like things neat and tidy, though, don't we?  Look at the biologists' concerted efforts -- only recently abandoned -- to pretend that the concept of species has any actual relevance.  The biological world doesn't fit into neat little cubbyholes; maybe the physical world doesn't, either.

Perhaps we do just live in an untidy universe, caught somewhere between sterile simplicity and complete chaos.  Being here in the middle allows for complexity, interconnectedness, and its own kind of messy-haired beauty.  But maybe that's what we should expect, you know?  It reminds me of the quote from the brilliant musician and electronic music pioneer Wendy Carlos: "What is full of redundancy or formula is predictable and boring.  What is free of all structure or discipline is random and boring.  In between lies art."

Maybe it's more than than just art, though.  Maybe in between lies... everything.

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A twist in the fabric

I hope y'all will indulge me one more astronomical post, because just this week in the journal Science Advances there was a very cool paper about an observational verification of the phenomenon of frame-dragging.

The whole thing depends on the the concept of "the fabric of space-time," something that got ripped so often on Star Trek that you'd swear the universe was made of cheap pantyhose.  To be fair, the idea isn't easy to wrap your brain around, something that becomes obvious when you hear some laypeople talking about the Big Bang.

I mean, I try to be tolerant, but if I hear one more person say, "It's a stupid idea -- that nothing exploded and became everything," I swear, I'm going to hurl a heavy object at 'em.

The problem hinges on trying to draw an analogy between the Big Bang (or in general, the expansion of the Universe) with a conventional explosion, where something blows up and spreads out into space that was already there.  With the Big Bang, it was space itself that was stretching -- if the idea of cosmic inflation turns out to be correct, at first it was at a rate that I can't even begin to comprehend -- so the matter in the Universe moved, and is still moving, not because something was physically pushing on it (as in the explosion of a stick of dynamite), but because the space it was embedded in was expanding.

(For what it's worth -- no, at this point we don't understand why this happened, what initiated it, or why the rate changed so suddenly after the "inflationary era" was over.  There is a lot still to figure out about this.  But one thing that's nearly certain is that it did happen, and the evidence still left behind of the Big Bang is incontrovertible.)

In any case, it's useful to change the comparison.  The Big Bang, and the expansion that followed, is much less like a conventional explosion than it is like blowing up a balloon.  Astronomer Edwin Hubble realized this when he first observed red shift, and found that everywhere he looked in the universe, objects seemed to be flying away from us -- the farther away, the faster they were moving.  It looked very much like we were the center of the Universe, the middle of the explosion, as if you were at the very point where a bomb exploded and were watching the bits and pieces rush away from you.

The truth, Hubble realized, was more subtle, but also way more interesting.  The fabric of space itself was stretching.  Picture a deflated balloon covered with dots.  You're a tiny person standing on one of the dots.  The balloon inflates -- and all the other dots appear to be rushing away from you.  But the weird thing is that it doesn't matter which dot you're standing on.  You could be on any dot, and still all the others would appear to be moving away, because the surface itself is expanding.  So an alien in a distant galaxy would also think everything was moving away from him, and he and Hubble would both be right.

There is no center of the Universe.  Or everywhere is the center.

Which amounts to the same thing.

So it's much more accurate, if you're trying to picture the whole thing, to think of space as being some kind of "stuff" capable of being deformed or stretched.

Which leads us to this week's mind-blowing discovery in astronomy.

One of the stranger predictions of the General Theory of Relativity -- and there's a lot of competition in that regard -- is that a massive spinning object would drag space-time along with it, twisting it out of shape in a phenomenon called Lense-Thirring frame dragging after the Austrian physicists who predicted it based on Einstein's theories, Josef Lense and Hans Thirring.  The problem is, like most of the phenomena associated with Relativity, the Lense-Thirring effect would only be observed in extreme conditions -- in this case a very high-mass object spinning really fast.

To give you an idea of what kind of extremes I'm talking about, here: with the Earth's mass and spin, the Lense-Thirring effect would cause an angular shift of about one degree every 100,000 years.

Not exactly something that jumps out at you.

[Image licensed under the Creative Commons ALMA (ESO/NAOJ/NRAO)/H. Kim et al., Celestial spiral with a twist, CC BY 4.0]

Now some scientists led by Cosimo Inserra of Cardiff University have found a remarkable pair of stellar remnants that provide the perfect laboratory for observing frame-dragging -- a star undergoing a "tidal disruption event" from a supermassive black hole (i.e. it's being messily devoured).  This is an ideal pairing to study because the star is orbiting the black hole once every twenty days, and the lighthouse-like beam of x-rays and radio waves produced as the material gets swallowed appears from our perspective to flicker on and off.  Conservation of Angular Momentum makes the flicker rate extremely constant.

But because of the Lense-Thirring effect, both the jets and the accretion disk of material swirling around the black hole have developed a wobble, which makes the entire system precess like a spinning top.  And the rate of precession...

... is exactly what is predicted from the General Theory of Relativity.

"Our study shows the most compelling evidence yet of Lense-Thirring precession -- a black hole dragging space time along with it in much the same way that a spinning top might drag the water around it in a whirlpool," Inserra said.  "This is a real gift for physicists as we confirm predictions made more than a century ago.  Not only that, but these observations also tell us more about the nature of TDEs -- when a star is shredded by the immense gravitational forces exerted by a black hole.  Unlike previous TDEs studied, which have steady radio signals, the signal for AT2020afhd showed short-term changes, which we were unable to attribute to the energy release from the black hole and its surrounding components.  This is further confirmed the dragging effect in our minds and offers scientists a new method for probing black holes."

The whole thing is staggering when you think about it.  Even the fact that we can detect such a small effect from this distance is a testimony to how far science has come.

"By showing that a black hole can drag space time and create this frame-dragging effect, we are also beginning to understand the mechanics of the process," Inserra said.  "It's a reminder to us, especially during the festive season as we gaze up at the night sky in wonder, that we have within our grasp the opportunity to identify ever more extraordinary objects in all the variations and flavors that nature has produced."

So Einstein wins again.  Pretty impressive for a guy who once said to a friend struggling in a math class, "Do not worry too much about your difficulties in mathematics.  I can assure you that mine are still greater."

So that's our mindblowing science of the day.  Spinning stars, twisting space-time, and tilted black holes.  I don't know how anyone can read about this stuff and not be both fascinated at how weird our universe is, and astonished that we've progressed to the point where we can understand at least a bit of it.  Here, several hundred quadrillion kilometers away, we've detected minuscule tilts in a whirling stellar remnant, and used it to support a theory that describes how matter and energy work throughout the Universe.

If that's not an impressive accomplishment, I don't know what is.

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Boldly going nowhere

To start out with the tl:dr -- no, despite what you may have heard, physicists do not have a working model of a warp drive.

Look, no one would love it more than me if we did.  I grew up on Star Trek and Star Wars, and the whole going-so-fast-the-stars-are-streaks thing is burned into my imagination.  (So, of course, is the weird trope from Lost in Space that if you go faster than light, time runs backwards.  I didn't say this stuff was all plausible.)

The reason we stargazers so desperately want a warp drive is because the distances involved in space travel are, well, astronomical.  Here's an analogy that will give you a feeling for it: imagine that the Sun (which is about 1.4 million kilometers in diameter) is shrunk down to the size of a marble, with a diameter of about 1.5 centimeters.

The Earth would be about the size of a grain of fine sand, and would be roughly a meter and a half away.  Jupiter would be eleven times larger in diameter, and over five times farther away.

You ready?  The closest star to the Sun, Proxima Centauri, would be a somewhat smaller marble, over four hundred kilometers away.  So if the marble-Sun was located in my living room, here in upstate New York, the marble-Proxima-Centauri would be somewhere around Baltimore, Maryland.

Everything in between is empty space.

Here's another way to think about it.  Voyager 1 -- the fastest human-made spacecraft ever created -- is traveling at about seventeen kilometers per second.  Which seems really fast, until you find out that at that speed, to get to Proxima Centauri would take seventy thousand years, if it was heading that way, which it's not.

So you can see why a warp drive would be nice.  How are we supposed to have a nice chat with the aliens when they're impossibly far away?

Well, if there's one thing I've learned, it's that the universe is under no compulsion to make me happy.  And at the moment, the current research -- led by Harold White of the Advanced Propulsion Laboratory -- doesn't make me happy at all.

The dozens of headlines in popular media I've seen claiming that the new paper has proposed an actual schematic for building a working warp drive aren't just exaggerations, they're outright fabrications.  Sabine Hossenfelder had a look at the paper, and for the first time I can ever recall, she (1) said the paper should never have been published in the first place, and (2) gave it a ten out of ten on her Bullshit Meter.  (She did not, however, do what I once saw her do, which is to print out the paper and then set fire to it, so I guess it could be worse.)  What all the hype is failing to tell you about is that White et al. have not actually created a "blueprint."  Here's Hossenfelder's take on it:

The way that they construct their so-called warp drive is that they postulate some curvature of spacetime and then postulate that it moves at a certain speed.  They then calculate the required energy from that.  That's their "engineering."  They postulate a shape, which they then plot.  The problem with this procedure is that it makes it entirely meaningless to say the warped space is a solution to Einstein's equations.  You see, you can take any, and I mean literally any, spacetime with any curvature, moving or not, and put it into the equations, and then just read off the source and call that a "solution."  The problem is that in general, there is no physically possible distribution of energies that gives you that source.  And of course, their so-called warp drive still needs negative energies.  Worse, they don't even mention the biggest problem with warp drives, which is that they still need to fulfill momentum conservation.  If you accelerate something going that way, you need to throw out stuff the other way.  This means that even with a warp drive, you still need a propulsion system.  

So, much as I hate to say it, this paper doesn't even get us incrementally closer to solving the faster-than-light travel problem.  We haven't discovered dilithium crystals or built warp field generators, or better still, seen any research by Zefram Cochrane.

I hate to throw cold water on anyone's excitement, but let's keep in mind that in this case, reality would have stepped in and done it sooner or later anyhow.

So that's today's rather short and disappointing foray into space.  Like I said, it's not that I'm happy about any of this.  At the moment, if there was a warp drive invented that could take us to distant star systems, I'd be the first in line.  For one thing, it'd be thrilling to see another planetary system close up.  For another, I'd finally be far enough away from Donald Trump.  But I'm afraid for now, we're stuck here on Earth, and probably will be for the foreseeable future.

Of course, I'm the same guy who told his students "adult tissue cloning is at least ten years in the future" exactly two weeks before Dolly the Sheep made headlines.  And in this case, if I'm wrong, I'd be somewhere beyond delighted to eat my words.

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Time lapse

Some days, being a skeptic is a losing proposition.

Only days after I posted a desperate plea for people to please check sources before posting/reposting/sharing/forwarding/whatever, I start seeing this popping up all over the place:

My first question was, "If they didn't detect it, how the fuck did they know it happened?"  But the image was followed by the following text, which should be accompanied with atmospheric, scary-sounding music:

What if, for a second, reality itself took a breath?

Somewhere between seconds, something strange happened.  Instruments across multiple observatories briefly froze—exactly 1.3 seconds of missing data, gone without error, glitch, or interference.  The world kept moving.  Clocks ticked.  But deep-space monitors, atomic timers, and gravitational wave sensors all recorded the same silence.  For a moment, time itself may have stopped.

Scientists are calling it a temporal anomaly, a mysterious blip that doesn’t fit any known pattern.  There was no solar flare, no magnetic disturbance, no hardware fault.  Everything just paused, then resumed as if nothing had happened.

While skeptics label it a data artifact, others suspect something deeper—perhaps a micro disruption in spacetime, or a ripple caused by massive gravitational shifts somewhere far across the cosmos.  If true, it means time isn’t as constant as we believe—it can tremble, stutter, or even halt briefly before stitching itself back together.

No one felt it.  No one saw it.  But machines built to measure eternity noticed—and that’s what makes it haunting.

If time can stop for 1.3 seconds… how many times has it already done so without us ever knowing?

Well, of all the things that never happened, this is the one that never happened the most.

We're told that this was reported as a huge mystery in Scientific American (it wasn't), and that physicists at MIT are hard at work trying to figure out what caused it (they aren't).  But the thing is, it doesn't take a Ph.D. in physics to see that there's something very off with this claim.

The problem here is that we always have to measure time relative to something (Cf. Einstein), so if every time-measuring device stopped simultaneously, there'd be no way to tell -- especially if (their words) "No one felt it... no one saw it."  If your watch is wrong, the only way you find out is by comparing it to an accurate clock, right?  If there was no accurate clock available, you'd continue thinking your own time measurement was the correct one, and show up to your doctor's appointment an hour late.

Even Star Trek: The Next Generation, which kind of made a name for itself playing fast and loose with the laws of physics, got that much right.  In "Timescape," Captain Picard, Deanna Troi, Geordi LaForge, and Data are on a shuttlecraft, and it passes through patches of distorted spacetime, in each of which time runs at a different speed; they figure it out because the patches are small, so they can actually see the effects of time passing at different rates in different parts of the shuttlecraft's interior (in one scene, Deanna sees everyone else seem to freeze in place, while she herself is still moving).  Likewise, in the extremely creepy episode "Schisms," Data figures out he was abducted from the ship (and from ordinary spacetime) for ninety minutes and seventeen seconds, but only because his internal chronometer is out of sync by that amount, by comparison to the ship's clocks.

That's not the only problen, though.  If time itself stopped, how would you measure how long it stopped?  Once "time stops" (whatever that actually means), there's no time passing by which to measure how long it stopped for.  "1.3 seconds" ceases to have any meaning at all.

But none of these objections seemed to occur to the people who posted this, nor (especially) to the vast majority of the people who responded to it.  Here's a sampler of the comments from just one instance of this showing up on Facebook.  Spelling and grammar are as written, because you can only write [sic] so many times:

• Time is determined by “light years” we are legitimately less than 1 second of life in the overall existence of what “time” truly is.
• Fuck yeah we did it, enough people are accessing the eternal now it’s starting to bring the rest of us over.
• It is possible that what happened in 1991 is beginning to come true.  I not only saw a UFO, but also met with Aliens on their spaceship.
• Time didn’t stop because time is made up by humans, everything exists all at once
• Its why my microwave keeps shifting backwards each week!!!!  I swear I set it to the right time, and within days, its back to being off by minutes.
• i actually experienced this but found it challenging to explain to others without sounding crazy or even dylusuonal so thank you for this post
• Probably due to the "asteriod" 3i/Atlas.
• Time is a human creation.  Ofcourse it has a flaw
• The moon is 1.3 light-seconds away.  Coincidence?

*brief pause to stop crying softly and banging my head on my desk*

I was somewhat heartened to run across a few comments stating that this is bullshit, and even one brave soul who waded in, guns blazing, making many of the same objections that I've made.  But the people who thought this all made sense far outnumbered the ones who recognized that it couldn't be true.

Look, on one level, I get it.  The world is kind of an awful place right now, and worse, it's so... banal.  Here we are in 2025, when we were told we'd have a sleek, shiny, high-tech world like The Jetsons, and instead we're still surrounded by the same old tawdry shoddiness as always, where the billionaires are trying to become trillionaires and the president of the United States spends millions of dollars tearing down half of the White House and turning the rest into what looks like a branch office of Cheesecake Factory, while the rest of us are trying to figure out how we can afford to buy groceries and pay for our health insurance.  I understand why anything that is enigmatic or exciting would be attractive.

Hell, at this point if the aliens did try to abduct me, I'll look upon it as a rescue mission.

But let's not let our attraction toward mysteries switch our brains off, okay?  In short: there was no temporal anomaly.  As described, if it did happen it would be at best undetectable, and at worst completely meaningless.  Time is not measured in light years, your microwave clock running slow is not an indication of a glitch in spacetime, we haven't "accessed the eternal," and none of this has anything to do with "asteriods."

Thank you. 

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The constancy of constants

One of the most enduring mysteries of physics is why the fundamental constants have the values they do.

I remember first thinking about this when I was a freshman in college, and we were looking at the Special Theory of Relativity in my intro-to-physics class.  The speed of light in a vacuum -- the ultimate speed limit, whatever Star Trek would have you believe -- is 299,792,458 meters per second.

What occurred to me was why it was exactly that number and not something else.  What if the speed of light was, say, twenty miles per hour?  Automobile travel would be a different game, and we'd have serious relativistic effects even riding a bicycle.  (Races would be an interesting affair; faster runners' clocks would move more slowly than slower runners' would, so by the end of the race, it'd be hard to get anyone to agree on what everyone's time was.)

All of which was delightfully silly stuff but didn't really get at the original question, which is why the speed of light has the value it does.  And it's not just the speed of light; in Martin Rees's wonderful book Just Six Numbers, he looks at how a handful of fundamental constants -- the gravitational flatness of the universe, the strength of the strong nuclear force, the ratio between the strength of the electromagnetic force and the gravitational force, the number of spatial dimensions, the ratio between the rest mass energy of matter and the gravitational field energy, and the cosmological constant -- have combined to produce the universe around us.  Alter any of these, even by a little bit, and you have a universe that would be profoundly hostile to life, if not to stable matter in general.

This has led some of the more religious-minded folks to what is called the Strong Anthropic Principle, sometimes called the "fine-tuning argument" -- that the universe has been fine-tuned for life, presumably by a Higher Power tweaking the dials on those constants to make them juuuuuuust right for us.  Which runs into two unfortunate counterarguments: (1) the vast majority of the universe is completely hostile to life regardless, including much of our home planet; and (2) the fact that we live in a universe where the important constants have those particular values isn't that surprising, because if they didn't, we wouldn't be around to remark upon it.

The latter is something known as the Weak Anthropic Principle, a stance that doesn't tell you much except for the unremarkable fact that the only kind of universe we could live in is one that has the conditions in which we could live.

[Image is in the Public Domain]

What I find intriguing is that none of these universal constants is derivable -- none come out of calculations based upon known physical laws... yet.  It might be that some of them are derivable and we just haven't figured out how.  Thus far, though, they seem completely arbitrary (except, as noted, that they have to have the values that they do in order for us to be here to consider the question).

A subtler question, and one that (unlike the fine-tuning argument) is actually testable, is whether those constants are the same everywhere in the universe, and whether they're constant over time.  Because if not -- if they vary either in time or space -- that strongly implies that they're not arbitrary, but derive from some underlying characteristic of matter, energy, and space/time that we have yet to uncover, and therefore in altered conditions could have a different value.  So a lot of time is being spent to determine whether any of these constants might be not so constant after all.

We at least have results for one of them, one that is not on Rees's List of Six but is nonetheless pretty damn important; the fine-structure constant, usually written as the Greek letter alpha.  The fine-structure constant is a measure of the strength of interaction between electrons and photons, and is equal to 1/137 (it's a dimensionless number, so it doesn't matter what units you use).

The fine-structure constant is one of the numbers whose value is instrumental in the formation of atoms, so (like Rees's numbers) if it were much different, the universe would be a very different place.  It's one that can be studied at a distance, because one outcome of the fine-structure constant having the value it does is that it creates the spread between the spectral lines of hydrogen.

So a team of physicists looked at the spectrum of hydrogen emitted in the vicinity of a supermassive black hole -- a place where the fabric of space/time is highly contorted because of the enormous gravitational field.  In a paper in Physical Review Letters, we find out that the fine-structure constant in that extremely different and hostile region of space is...

... 1/137.

The authors write:

Searching for space-time variations of the constants of Nature is a promising way to search for new physics beyond General Relativity and the standard model motivated by unification theories and models of dark matter and dark energy.  We propose a new way to search for a variation of the fine-structure constant using measurements of late-type evolved giant stars from the S-star cluster orbiting the supermassive black hole in our Galactic Center.  A measurement of the difference between distinct absorption lines (with different sensitivity to the fine structure constant) from a star leads to a direct estimate of a variation of the fine structure constant between the star’s location and Earth.  Using spectroscopic measurements of 5 stars, we obtain a constraint on the relative variation of the fine structure constant below 10^−5.

So the variation between the fine-structure constant and the fine-structure constant near a humongous black hole is less than a factor of 0.00001.

Note that this still doesn't tell us anything about why the fundamental constants have the values they do, all it does is suggest pretty strongly that they are constant regardless of the conditions pertaining in the region of space where they're measured.  So I guess we're still in the same boat as physicist Wolfgang Pauli, who said, "When I die, the first question I'm going to ask the Devil is, 'What is the meaning of the fine-structure constant?'"

The universe is a strange and mysterious place, and we're only beginning to figure out how it all works.  I mean, think about it; while I don't want to denigrate the scientific accomplishments of our forebears, we've really only begun to parse how the fundamental laws of nature work in the last 150 years.  It's an exciting time -- even if we don't yet have answers to a lot of the most basic questions in physics, at least we're figuring out which questions to ask.

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Thunderbolts and lightning (very very frightening)

The cause of lightning has been strangely elusive.

Oh, in the broadest-brush terms, we've understood it for a while.  The rapidly-rising column of air in a cumulonimbus cloud induces charge separation, resulting in an electric potential difference between the ground and the air.  At a potential of about three megavolts per meter, the dielectric strength of damp air is exceeded -- the maximum voltage it can withstand without the molecules ionizing, and becoming conductive to electrical current.  This creates a moving channel of ionized air called a stepped leader.  When the leader reaches the ground, the overall resistance between the ground and the cloud drops dramatically, and discharge occurs, called the return stroke.  This releases between two hundred megajoules and seven gigajoules of energy in a fraction of a second, heating the air column to around thirty thousand degrees Celsius -- five times hotter than the surface of the Sun.

That's the origin of both the flash of light and the shock wave in the air that we hear as thunder.

[Image licensed under the Creative Commons Maxime Raynal from France, Port and lighthouse overnight storm with lightning in Port-la-Nouvelle, CC BY 2.0]

The problem is, there was no consensus on what exactly caused the very first step -- the charge separation in the cloud that triggers the voltage difference.  Some scientists believed that it was friction between the air and the updrafting raindrops (and hail) characteristic of a thundercloud, similar to the way you can induce a static charge on a balloon by rubbing it against your shirt.  But experiments weren't able to confirm that, and most places you look, you'll see words like "still being investigated" and "uncertain at best" and "poorly understood process."

Until now.

A team of scientists led by Victor Pasko of Pennsylvania State University have shown that the initiation of lightning is caused by a literal perfect storm of conditions.  They found that free "seed" electrons, knocked loose by cosmic rays, are accelerating into the rapidly-rising air column at "relativistic" speeds -- i.e., a significant fraction of the speed of light -- and then ram into nitrogen and oxygen atoms.  These collisions trigger a shower of additional electrons, causing an avalanche, which is then swept upward into the upper parts of the cloud.

This is what causes the charge separation, the voltage difference between top and bottom, and the eventual discharge we see as lightning.

It also produces electromagnetic radiation across the spectrum from radio waves to gamma rays, something that had been observed but never explained.

"By simulating conditions with our model that replicated the conditions observed in the field, we offered a complete explanation for the X-rays and radio emissions that are present within thunderclouds," Pasko said.  "We demonstrated how electrons, accelerated by strong electric fields in thunderclouds, produce X-rays as they collide with air molecules like nitrogen and oxygen, and create an avalanche of electrons that produce high-energy photons that initiate lightning...  [T]he high-energy X-rays produced by relativistic electron avalanches generate new seed electrons driven by the photoelectric effect in air, rapidly amplifying these avalanches.  In addition to being produced in very compact volumes, this runaway chain reaction can occur with highly variable strength, often leading to detectable levels of X-rays, while accompanied by very weak optical and radio emissions.  This explains why these gamma-ray flashes can emerge from source regions that appear optically dim and radio silent."

There's still a lot left to explain, however.  Also this week, a paper came out of Arizona State University about the astonishing "megaflash" that occurred in October 2017, where a single lightning bolt traveled over eight hundred kilometers -- from eastern Texas all the way to Kansas City.  Even though the megaflash dropped some cloud-to-ground leaders along the way, it didn't discharge completely until the very end.  Megaflashes are rare, but what conditions could lead to a main stepped leader (and the corresponding return stroke) extending that far before grounding are unknown.

So like with all good science, the new research answers some questions and raises others.  Here in upstate New York we're in thunderstorm season, and while we don't get the crazy storms they see in the southeast and midwest, we've had some powerful ones this summer.  I've always liked a good storm, as long as the lightning stays away from my house.  A friend of ours had his house struck by lightning a few years ago and it fried his electrical system (including his computer) -- something that leads me to unplug my laptop and router as soon as I hear rumbling.

Even if the mechanisms of lightning are now less mysterious, it's still just as dangerous.  Very very frightening, as Freddie Mercury observed.

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Time and tide

I don't know if you've had the experience of running into a relatively straightforward concept that your brain just doesn't seem to be able to wrap itself around.

One such idea for me is the explanation for tides.  I've gone through it over and over, starting in high school physics, and I keep having to go back and revisit it because I think I've got it and then my brain goes, "...wait, what?" and I have to look it up again.

The sticking point has always been why there are two high tides on opposite sides of the Earth.  I get that the water on the side of the Earth facing the Moon experiences the Moon's extra gravitational attraction and is pulled away from the Earth's surface, creating a bulge.  But why is there a bulge on the side facing away from the Moon?

Now that I'm 64 and have gone over it approximately 482 times, I think I've finally got it.  Which is more than I can say for Bill O'Reilly:

So, let's see if I can prove Mr. O'Reilly wrong.

Consider three points on the Earth: A (on the surface, facing the Moon), B (at the center of the Earth), and C (on the surface, opposite the Moon).  Then ask yourself what the difference is in the pull of the Moon on those three points.

Isaac Newton showed that the force of gravity is proportional to two things -- the masses of the objects involved, and the inverse square of the distance between them.  The second part is what's important here.  Because A, B, and C are all different distances from the Moon, they experience a difference in the gravitational attraction they experience.  A is pulled hardest and C the least, with B in the middle.

This means that the Earth is stretched.  Everything experiences these tidal forces, but water, which is freer to move, responds far more than land does.  At point A, the water is pulled toward the Moon, and experiences a high tide.  (That's the obvious part.)  The less obvious part is that because points B and C are subject to a difference in the gravitational attraction, the net effect is to pull them apart -- so from our perspective on the Earth's surface, the water at C pulls away and upward, so there's a high tide there, as well.

There's practically no limit to how big these forces can get.  On the Earth, they're fairly small, although sometimes phenomena like a seiche (a standing wave in a partially-enclosed body of water) can amplify the effect and create situations like what happens in the Bay of Fundy, Nova Scotia, where the difference in the water level between high and low tide can be as much as sixteen meters.

But out in space, you can find systems where the masses and distances combine to create tidal forces that are, to put it in scientific terms, abso-fucking-lutely enormous.  This, in fact, is why the whole subject comes up today; the discovery of a binary system in the Large Magellanic Cloud made up of a supergiant with a mass thirty-five times that of the Sun, and a smaller (but still giant) companion ten times the mass of the Sun.  They're close enough that they orbit their common center of gravity about once a month.  And the combination of the huge masses and close proximity creates tidal bulges about three million kilometers tall.

That's over three times the diameter of the Sun.

You think the people living along the Bay of Fundy have it bad.

Artist's conception of the system in the Large Magellanic Cloud [Illustration by Melissa Weiss of NASA/Chandra X-Ray Observatory/Center for Astrophysics]

And that's not even as extreme as tidal forces can get.  If you were unfortunate enough to fall feet-first into a black hole, you would undergo what physicists call -- I'm not making this up -- spaghettification.  The tidal forces are so huge that they're even significant across a small distance like that between your head and your feet, so you'd be stretched along your vertical axis and compressed along your horizontal one.  Put more bluntly, you'd be squished like a tube of toothpaste, ultimately comprising the same volume as before but a much greater length.

It would not be pleasant.

Be that as it may, I think I've finally got the explanation for tides locked down.  We'll see how long it lasts.

At least I'm pretty sure I'm still ahead of Bill O'Reilly.

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Djinn and paradox

In the very peculiar Doctor Who episode "Joy to the World," the character of Joy Almondo is being controlled by a device inside a briefcase that -- if activated -- will release as much energy as a supernova, destroying the Earth (and the rest of the Solar System).  But just at the nick of time, a future version of the Doctor (from exactly one year later) arrives and gives the current Doctor the override code, saving the day.

The question comes up, though, of how the future Doctor knew what the code was.  The current Doctor, after all, hadn't known it until he was told.  He reasons that during that year, he must have learned the code from somewhere or someone -- but the year passes without anyone contacting him about the briefcase and its contents.  Right before the year ends (at which point he has to jump back to complete the loop) he realizes that his surmise wasn't true.  Because, of course, he already knew the code.  He'd learned it from his other self.  So armed with that knowledge, he jumps back and saves the day.

Well, he saves the moment, at least.  As it turns out, their troubles are just beginning, but that's a discussion for another time.

A similar trope occurred in the 1980 movie Somewhere in Time, but with an actual physical object rather than just a piece of information.  Playwright Richard Collier (played by Christopher Reeve) is at a party celebrating the debut of his most recent play, and is approached by an elderly woman who hands him an ornate pocket watch and says, in a desperate voice, "Come back to me."  Collier soon goes back in time by six decades, finds her as a young woman, and they fall desperately in love -- and he gives her the pocket watch.  Ultimately, he's pulled back into the present, and his girlfriend grows old without him, but right before she dies she finds him and gives him back the watch, closing the loop.

All of this makes for a fun twist; such temporal paradoxes are common fare in fiction, after all.  And the whole thing seems to make sense until you ask the question of, respectively (1) where did the override code originally come from? and (2) who made the pocket watch?

Because when you think about it -- and don't think too hard, because these kinds of things are a little boggling -- neither one has any origin.  They're self-creating and self-destroying, looped like the famous Ouroboros of ancient myth, the snake swallowing its own tail. 

[Image is in the Public Domain]

The pocket watch is especially mystifying, because after all, it's an actual object.  If Collier brought it back with him into the past, then it didn't exist prior to the moment he arrived in 1920, nor after the moment he left in 1980 -- which seems to violate the Law of Conservation of Matter and Energy.

Physicists Andrei Lossev and Igor Novikov called such originless entities "djinn particles," because (like the djinn, or "genies," of Arabian mythology) they seem to appear out of nowhere.  Lossev and Novikov realized that although "closed timelike curves" are, theoretically at least, allowed by the Theory of General Relativity, they all too easily engender paradoxes.  So they proposed something they call the self-consistency principle -- that time travel into the past is possible if and only if it does not generate a paradox.

So let's say you wanted to do something to change history.  Say, for example, that you wanted to go back in time and give Arthur Tudor, Prince of Wales some medication to save his life from the fever that otherwise killed him at age fifteen.  This would have made him king of England seven years later instead of his younger brother, who would have become the infamous King Henry VIII, thus dramatically changing the course of history.  In the process, of course, it also generates a paradox; because if Henry VIII never became king, you would have no motivation to go back into the past and prevent him from becoming king, right?  Your own memories would be consistent with the timeline of history that led to your present moment.  Thus, you wouldn't go back in time and save Arthur's life.  But this would mean Arthur would die at fifteen, Henry VIII becomes king instead, and... well, you see the difficulty.

Lossev and Novikov's self-consistency principle fixes this problem.  It tells us that your attempt to save Prince Arthur must have failed -- because we know that didn't happen.  If you did go back in time, you were simply incorporated into whatever actually did happen.

Timeline of history saved.  Nothing changed.  Ergo, no paradox.

You'd think that physicists would kind of go "whew, dodged that bullet," but interestingly, most of them look at the self-consistency principle as a bandaid, an unwarranted and artificial constraint that doesn't arise from the models themselves.  Joseph Polchinski came up with another paradoxical situation -- a billiard ball fired into a wormhole at exactly the right angle that when it comes out of the other end, it runs into (and deflects) itself, preventing it from entering the wormhole in the first place -- and analysis by Nobel Prize-winning physicist Kip Thorne found there's nothing inherent in the models that prevents this sort of thing.

Some have argued that the ease with which time travel into the past engenders paradox is an indication that it's simply an impossibility; eventually, they say, we'll find that there's something in the models that rules out reversing the clock entirely.  In fact, in 2009, Stephen Hawking famously hosted a time-travelers' party at Cambridge University, complete with fancy food, champagne, and balloons -- but only sent out invitations the following day.  He waited several hours, and no one showed up.

That, he said, was that.  Because what time traveler could resist a party?

But there's still a lingering issue, because it seems like if it really is impossible, there should be some way to prove it rigorously, and thus far, that hasn't happened.  Last week we looked at the recent paper by Gavassino et al. that implied a partial loophole from the Second Law of Thermodynamics -- if you could travel into the past, entropy would run backwards during part of the loop and erase your memory of what had happened -- but it still leaves the question of djinn particles and self-deflecting billiard balls unsolved.

Seems like we're stuck with closed timelike curves, paradoxes notwithstanding.

Me, I think my mind is blown sufficiently for one day.  Time to go play with my puppy, who only worries about paradoxes like "when is breakfast?" and the baffling question of why he is not currently getting a belly rub.  All in all, probably a less stressful approach to life.

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