Tag Archives: physics

Big Bang Bogosity

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One of my long-time mantras on this blog has been “The worst math is no math”. Today, I’m going to show you yet another example of that: a recent post on Boing-Boing called “The Big Bang is Going Down”, by a self-proclaimed genius named Rick Rosner.

First postulated in 1931, the Big Bang has been the standard theory of the origin and structure of the universe for 50 years. In my opinion, (the opinion of a TV comedy writer, stripper and bar bouncer who does physics on the side) the Big Bang is about to collapse catastrophically, and that’s a good thing.

According to Big Bang theory, the universe exploded into existence from basically nothing 13.7-something billion years ago. But we’re at the beginning of a wave of discoveries of stuff that’s older than 13.7 billion years.

We’re constantly learning more about our universe, how it works, and how it started. New information isn’t necessarily a catastrophe for our existing theories; it’s just more data. There’s constantly new data coming in – and as yet, none of it comes close to causing the big bang theory to catastrophically collapse.

The two specific examples cited in the article are:

  1. one quasar that appears to be younger than we might expect – it existed just 900 million years after the current estimate of when the big bang occurred. That’s very surprising, and very exciting. But even in existing models of the big bang, it’s surprising, but not impossible. (No link, because the link in the original article doesn’t work.)
  2. an ancient galaxy – a galaxy that existed only 700 million years after the big bang occurred – contains dust. Cosmic dust is made of atoms much larger than hydrogen – like carbon, silicon, and iron, which are (per current theories) the product of supernovas. Supernovas generally don’t happen to stars younger than a couple of billion years – so finding dust in a galaxy less than a billion years after the universe began is quite surprising. But again: impossible under the big bang? No.

The problem with both of these arguments against the big bang is: they’re vague. They’re both handwavy arguments made about crude statements about what “should” be possible or impossible according to the bing bang theory. But neither comes close to the kind of precision that an actual scientific argument requires.

Scientists don’t use math because they like to be obscure, or because they think all of the pretty symbols look cool. Math is a tool used by scientists, because it’s useful. Real theories in physics need to be precise. They need to make predictions, and those predictions need to match reality to the limits of our ability to measure them. Without that kind of precision, we can’t test theories – we can’t check how well they model reality. And precise modelling of reality is the whole point.

The big bang is an extremely successful theory. It makes a lot of predictions, which do a good job of matching observations. It’s evolved in significant ways over time – but it remains by far the best theory we have – and by “best”, I mean “most accurate and successfully predictive”. The catch to all of this is that when we talk about the big bang theory, we don’t mean “the universe started out as a dot, and blew up like a huge bomb, and everything we see is the remnants of that giant explosion”. That’s an informal description, but it’s not the theory. That informal description is so vague that a motivated person can interpret it in ways that are consistent, or inconsistent with almost any given piece of evidence. The real big bang theory isn’t a single english statement – it’s many different mathematical statements which, taken together, produce a description of an expansionary universe that looks like the one we live in. For a really, really small sample, you can take a look at a nice old post by Ethan Siegel over here.

If you really want to make an argument that it’s impossible according to the big bang theory, you need to show how it’s impossible. The argument by Mr. Rosner is that the atoms in the dust in that galaxy couldn’t exist according to the big bang, because there wasn’t time for supernovas to create it. To make that argument, he needs to show that that’s true: he needs to look at the math that describes how stars form and how they behave, and then using that math, show that the supernovas couldn’t have happened in that timeframe. He doesn’t do anything like that: he just asserts that it’s true.

In contrast, if you read the papers by the guys who discovered the dust-filled galaxy, you’ll notice that they don’t come anywhere close to saying that this is impossible, or inconsistent with the big bang. All they say is that it’s surprising, and that we made need to revise our understanding of the behavior of matter in the early stages of the universe. The reason that they say that is because there’s nothing there that fundamentally conflicts with our current understanding of the big bang.

But Mr. Rosner can get away with the argument, because he’s being vague where the scientists are being precise. A scientist isn’t going to say “Yes, we know that it’s possible according to the big bang theory”, because the scientist doesn’t have the math to show it’s possible. At the moment, we don’t have sufficient precise math either way to come to a conclusion; we don’t know. But what we do know is that millions of other observations in different contexts, different locations, observed by different methods by different people, are all consistent with the predictions of the big bang. Given that we don’t have any evidence to support the idea that this couldn’t happen under the big bang, we continue to say that the big bang is the theory most consistent with our observations, that it makes better predictions than anything else, and so we assume (until we have evidence to the contrary) that this isn’t inconsistent. We don’t have any reason to discard the big bang theory on the basis of this!

Mr. Rosner, though, goes even further, proposing what he believes will be the replacement for the big bang.

The theory which replaces the Big Bang will treat the universe as an information processor. The universe is made of information and uses that information to define itself. Quantum mechanics and relativity pertain to the interactions of information, and the theory which finally unifies them will be information-based.

The Big Bang doesn’t describe an information-processing universe. Information processors don’t blow up after one calculation. You don’t toss your smart phone after just one text. The real universe – a non-Big Bang universe – recycles itself in a series of little bangs, lighting up old, burned-out galaxies which function as memory as needed.

In rolling cycles of universal computation, old, collapsed, neutron-rich galaxies are lit up again, being hosed down by neutrinos (which have probably been channeled along cosmic filaments), turning some of their neutrons to protons, which provides fuel for stellar fusion. Each calculation takes a few tens of billions of years as newly lit-up galaxies burn their proton fuel in stars, sharing information and forming new associations in the active center of the universe before burning out again. This is ultra-deep time, with what looks like a Big Bang universe being only a long moment in a vast string of such moments across trillions or quadrillions of giga-years.

This is not a novel idea. There are a ton of variations of the “universe as computation” that have been proposed over the years. Just off the top of my head, I can rattle off variations that I’ve read (in decreasing order of interest) by Minsky (can’t find the paper at the moment; I read it back when I was in grad school), by Fredkin, by Wolfram, and by Langan.

All of these theories assert in one form or another that our universe is either a massive computer or a massive computation, and that everything we can observe is part of a computational process. It’s a fascinating idea, and there are aspects of it that are really compelling.

For example, the Minsky model has an interesting explanation for the speed of light as an absolute limit, and for time dilation. Minksy’s model says that the universe is a giant cellular automaton. Each minimum quanta of space is a cell in the automaton. When a particle is located in a particular cell, that cell is “running” the computation that describes that particle. For a particle to move, the data describing it needs to get moved from its current location to its new location at the next time quanta. That takes some amount of computation, and the cell can only perform a finite amount of computation per quanta. The faster the particle moves, the more of its time quantum are dedicated to motion, and the less it has for anything else. The speed of light, in this theory, is the speed where the full quanta for computing a particle’s behavior is dedicated to nothing but moving it to its next location.

It’s very pretty. Intuitively, it works. That makes it an interesting idea. But the problem is, no one has come up with an actual working model. We’ve got real observations of the behavior of the physical universe that no one has been able to describe using the cellular automaton model.

That’s the problem with all of the computational hypotheses so far. They look really good in the abstract, but none of them come close to actually working in practice.

A lot of people nowadays like to mock string theory, because it’s a theory that looks really ogood, but has no testable predictions. String theory can describe the behavior of the universe that we see. The problem with it isn’t that there’s things we observe in the universe that it can’t predict, but because it can predict just about anything. There are a ton of parameters in the theory that can be shifted, and depending on their values, almost anything that we could observe can be fit by string theory. The problem with it is twofold: we don’t have any way (yet) of figuring out what values those parameters need to have to fit our universe, and we don’t have any way (yet) of performing an experiment that tests a prediction of string theory that’s different from the predictions of other theories.

As much as we enjoy mocking string theory for its lack of predictive value, the computational hypotheses are far worse! So far, no one has been able to come up with one that can come close to explaining all of the things that we’ve already observed, much less to making predictions that are better than our current theories.

But just like he did with his “criticism” of the big bang, Mr. Rosner makes predictions, but doesn’t bother to make them precise. There’s no math to his prediction, because there’s no content to his prediction. It doesn’t mean anything. It’s empty prose, proclaiming victory for an ill-defined idea on the basis of hand-waving and hype.

Boing-Boing should be ashamed for giving this bozo a platform.

Big Science News! Inflation, Gravity, and Gravitational Waves

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gwaves

So, big announcement yesterday. Lots of people have asked if I could try to explain it! People have been asking since yesterday morning, but folks, I’ve got a job! I’ve been writing when I have time while running slow tests in another window, so it’s taken more than a day to get to it.

The announcement is really, really fascinating. A group has been able to observe gravity wave fluctuations in the cosmic microwave background. This is a huge deal! For example, Sean Carroll (no relation) wrote:

other than finding life on other planets or directly detecting dark matter, I can’t think of any other plausible near-term astrophysical discovery more important than this one for improving our understanding of the universe.

Why is this such a big deal?

This is not an easy thing to explain, but I’ll do my best.

We believe that the universe started with the big bang – all of the matter and energy, all of the space in the universe, expanding outwards from a point. There’s all sorts of amazing evidence for the big bang – not least the cosmic microwave background.

But the big-bang theory has some problems. In particular, why is everything the same everywhere?

That sounds like a strange question. Why wouldn’t it be the same everywhere?

Here’s why: because for changes to occur at the same time in different places, we expect there to be some causal connection between those places. If there is no plausible causal connection, then there’s a problem: how could things happen at the same time, in the same way?

That causal connection is a problem. To explain why, first I need to explain the idea of the observable universe.

Right now, there is some part of the universe that we can observe – because light from it has reached us. There’s also some part of the universe that we can’t observe, because light from it hasn’t reached us yet. Every day, every moment, the observable universe gets larger – not because the universe is expanding (it is, but we’re not talking about the size of the universe, but rather of the part of the universe that we can observe). It’s literally getting larger, because there are parts of the universe that are so far away from us, that the first light they emitted after the universe started didn’t reach us until right now. That threshold, of the stuff that couldn’t possible have gotten here yet, is constantly expanding, getting farther and farther away.

There are parts of the universe that are so far away, that the light from them couldn’t reach us until now. But when we look at that light, and use it to see what’s there, it looks exactly like what we see around us.

The problem is, it shouldn’t. If you just take the big bang, and you don’t have a period of inflation, what you would expect is a highly non-uniform universe with a very high spatial curvurature. Places very far away shouldn’t be exactly the same as here, because there is no mechanism which can make them evolve in exactly the same way that they did here! As energy levels from the big bang decrease, local fluctuations should have produced very different outcomes. They shouldn’t have ended up the same as here – because there’s many different ways things could have turned out, and they can’t be causally connected, because there’s no way that information could have gotten from there to here in time for it to have any effect.

Light is the fastest thing in the universe – but light from these places just got here. That means that until now, there couldn’t possibly be any connection between here and there. How could all of the fundamental properties of space – its curvature, the density of matter and energy – be exactly the same as here, if there was never any possible causal contact between us?

The answer to that is an idea called inflation. At some time in the earliest part of the universe – during a tiny fraction of the first second – the universe itself expanded at a speed faster than light. (Note: this doesn’t mean that stuff moved faster than light – it means that space itself expanded, creating space between things so that the distance between them expanded faster than light. Subtle distinction, but important!) So the matter and energy all got “stretched” out, at the same time, in the same way, giving the universe the basic shape and structure that it has now.

Inflation is the process that created the uniform universe. This process, which happened to the entire universe, had tiny but uniform fluctuations because of the basic quantum structure of the universe. Those fluctuations were the same everywhere – because when they happened, they were causally connected! Inflation expanded space, but those fluctuations provided the basic structure on which the stuff we observe in the universe developed. Since that basic underlying structure is the same everywhere, everything built on top it is the same as well.

We’ve seen lots of evidence for inflation, but it hasn’t quite been a universally accepted idea.

The next piece of the puzzle is gravity. Gravity at least appears to be very strange. All of the other forces in our universe behave in a consistent way. In fact, we’ve been able to show that they’re ultimately different aspects of the same underlying phenomena. All of the other forces can be described quantum mechanically, and they operate through exchange particles that transmit force/energy – for example, electromagnetic forces are transmitted by photons. But not gravity: we have no working quantum theory for how gravity works! We strongly suspect that it must, but we don’t know how, and up to now, we never found any actual proof that it does behave quantumly. But if it did, and if inflation happened, that means that those quantum fluctations during expansion, the things that provided the basic lattice on which matter and energy hang, should have created an echo in gravity!

Unfortunately, we can’t see gravity. The combination of inflation and quantum mechanics means that there should be gravitational fluctuations in the universe – waves in the basic field of gravity. We’ve predicted those waves for a long time. But we haven’t been able to actually test that prediction, because we didn’t have a way to see gravitational waves.

So now, I can finally get to this new result.

They believe that they found gravity waves in the cosmic microwave background. They used a brilliant scheme to observe them: if we look at the cosmic microwave background – not at any specific celestial object, but just at the background – gravitational waves would created a very subtle tensor polarization effect. So they created a system that could observe polarization. Then they removed all of the kinds of polarization that could be explained by anything other than gravitational waves. What they were left with was a very clear wave pattern in the polarization – exactly what was predicted by quantum inflation! You can see one of their images of this wave pattern at the top of this post.

If these new observations are confirmed, that means that we have new evidence for two things:

  1. Inflation happened. These gravity waves are an expected residue of inflation. They’re exactly what we would have expected if inflation happened, and we don’t have any other explanation that’s compatible with them.
  2. Gravity is quantum! If gravity wasn’t quantum, then expansion would have completely smoothed out the gravitational effects, and we wouldn’t see gravitational waves. Since we do see waves, it’s strong evidence that gravity really does have a quantum aspect. We still don’t know how it works, but now we have some really compelling evidence that it must!

The Meaning of the Higgs

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This isn’t exactly my area of expertise, but I’ve gotten requests by both email and twitter to try to explain yesterday’s news about the Higgs’ boson.

The questions.

  • What is this Higgs’ boson thing?
  • How did they find it?

  • What does the five sigma stuff mean?
  • Why do they talk about it as a “Higgs’-like particle”?

So, first things first. What is a Higgs’ boson?

When things in the universe interact, they usually don’t actually interacts by touching each other directly. They interact through forces and fields. What that means is a bit tricky. I can define it mathematically, but it won’t do a bit of good for intuition. But the basic idea is that space itself has some properties. A point in space, even when it’s completely empty, it has some properties.

Outside of empty space, we have particles of various types. Those particles interact with each other, and with space itself. Those interactions are what end up producing the universe we see and live in.

Fields are, essentially, a property of space. A field is, at its simplest, a kind of property of space that is defined at every point in space.

When particles interact with fields, they can end up exchanging energy. They do that through a particular kind of particle, called an exchange particle. For example, think about an electromagnetic field. An electron orbits an atomic nucleus, due to forces created by the electromagnetic fields of the electrons and protons. When an electron moves to a lower-energy orbital, it produces a photon; when it absorbs a photon, it can jump to a higher orbital. The photon is the exchange particle for the electromagnetic field. Exchange particles are instances of a kind of particle called a boson.

So.. one of the really big mysteries of physics is: why do some particles have mass, and other particles don’t? That is, some particles, like protons, have masses. Others, like photons, don’t. Why is that?

It’s quite a big mystery. Based on our best model – called the standard model – we can predict all of the basic kinds of particles, and what their masses should be. But we didn’t have a clue about why there’s mass at all!

So, following the usual pattern in particle physics, we predict that there’s a field. Particles moving through that field, if they interact with the field, experience a sort of drag. That drag is mass. So – just like particles like neutrinos aren’t affected by electromagnetic fields, some particles like photons won’t have mass because they don’t interact with the field that produces mass. We call that field the Higgs’ field.

(The previous paragraph formerly contained an error. The higgs field produces mass, not gravity. Just a stupid typo; my fingers got ahead of my brain.)

So physicists proposed the existence of the Higgs’ field. But how could they test it?

It’s a field. Fields have exchange particles. What would the exchange particles of the Higgs’ field be? Exchange particles are bosons, so this one is, naturally, called a Higgs’ boson. So if the Higgs’ field exists, then it will have an exchange particle. If the standard model of physics is right, then we can use it to predict the mass that that boson must have.

So – if we can find a particle whose mass matches what we predict, and it has the correct properties for a mass-field exchange particle, then we can infer that the Higgs’ field is real, and is the cause of mass.

How did they find the Higgs’ boson?

We have a pretty good idea of what the mass of the Higgs’ boson must be. We can describe that mass in terms of a quantity of energy. (See the infamous Einstein equation!) If we can take particles that we can easily see and manipulate, and we can accelerate them up to super-super high speed, and collide them together. If the energy of a collision matches the mass of a particle, it can create that kind of particle. So we slam together, say, two protons at high enough energy, we’ll get a Higgs’ boson.

But things are never quite that easy. There are a bunch of problems. First, the kind of collision that can produce a Higgs’ doesn’t always produce one. It can produce a variety of results, depending on the specifics of the collision as well as purely random factors. Second, it produces a lot more than just a Higgs’. We’re talking about an extremely complex, extremely high energy collision, with a ton of complex results. And third, the Higgs’ boson isn’t particularly stable. It doesn’t really like to exist. So like many unstable things in particle physics, it decays, producing other particles. And many of those particles are themselves unstable, and decay into other particles. What we can observe is the last products of the collision, several steps back from the Higgs’. But we know what kind of things the Higgs’ can decay into, and what they can decay into, etc.

So, we slam these things together a couple of thousand, or a couple of million times. And we look at the results. We look at all of the results of all of the collisions. And we specifically look for a bump: if there’s really a specific collision energy level at which Higgs’ bosons are produced, then we’ll see a bump in the number of Higgs’ decay products that are produced by collisions at that energy. And what the announcement yesterday showed is that that’s exactly what they saw: a bump in the observations inside the expected range of values of the mass of a Higgs’ boson.

The bump

What does five sigmas mean?

Whenever we’re making observations of a complex phenomenon, there are all sorts of things that can confound our observations. There are measurement errors, calculation errors, random noise, among many other things. So we can’t just look at one, or two, or ten data points. We need to look at a lot of data. And when you’ve got a lot of data, there’s always a chance that you’ll see what appears to be a pattern in the data, which is really just the product of random noise

For example, there are some people who’ve won the lottery multiple times. That seems crazy – it’s so unlikely to win once! To win multiple times seems crazy. But probabilistically, if you keep observing lotteries, you’ll find repeat winners. Or you’ll find apparent patterns in the winning numbers, even though they’re being drawn randomly.

We don’t want to be fooled by statistics. So we create standards. We can compute how unlikely a given pattern would be, if it were occuring do to pure randomness. We can’t even absolutely rule out randomness, but for any degree of certainty, we can determine just how unlikely a given observation is to be due to randomness.

We describe that in terms of standard deviations. An observation of a phenomenon has a roughly 68% chance of being measured within one standard deviation (one sigma) of the actual value, or a roughly 32% chance of being observed outside of one sigma. At two sigmas, there’s only a roughly 5% chance of being outside. At three sigmas out, you’re down to a roughly 0.3% chance of randomly observing an event outside. The odds continue that way.

So, the Higgs’ hunters computed probabilities of observing the data that they found if they assumed that there was no Higgs’. The amount of data that they found exceeded 5 sigmas away from what you would expect by random chance if there was no Higgs’. That translates as damned unlikely. The ultimate choice of 5 sigmas is arbitrary, but it’s accepted as a threshold for certainty in particle physics. At five sigmas, we realistically rule out random chance.

Why do they keep saying Higgs’-like particle?

Remember up above, I said: “So – if we can find a particle whose mass matches what we predict, and it has the correct properties for a mass-field exchange particle, then we can infer that the Higgs’ field is real, and is the cause of mass”? There are two thing we need to show to conclude that we’ve found the mediator of the Higgs’ field. There needs to be a particle with the right mass, and it needs to have the properties of a mass-mediator. What we’ve got right now is an observation that yes, there is a particle at the mass we’d expect for a Higgs’. But we don’t have observations yet of any properties of the particle other than its mass. Assuming the standard model is right, the odds of finding another particle with that mass is damned unlikely, but the standard model could be wrong. It’s not likely at this point, but people like to be careful. So at this point, to be precise, we’ve observed a Higgs’-like particle – a particle that according to all of the observations we’ve made so far appears to be a Higgs’; but until we observe some properties other than mass, we can’t be absolutely certain that it’s a Higgs’.

Return of a Classic: The Electromagnetic Gravity Revolution!

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Between work, trying to finish my AppEngine book, and doing all of the technical work getting Scientopia running smoothly on the new hosting service, I haven’t had a lot of time for writing new blog posts. So, once again, I’m recycling some old stuff.

It’s that time again – yes, we have yet another wacko reinvention of physics that pretends to have math on its side. This time, it’s “The Electro-Magnetic Radiation Pressure Gravity Theory”, by “Engineer Xavier Borg”. (Yes, he signs all of his papers that way – it’s always with the title “Engineer”.) This one is as wacky as Neal Adams and his PMPs, except that the author seems to be less clueless.

At first I wondered if this were a hoax – I mean, “Engineer Borg”? It seems like a deliberately goofy name for someone with a crackpot theory of physics… But on reading through his web-pages, the quantity and depth of his writing has me leaning towards believing that this stuff is legit. (And as several commenters pointed out the first time I posted this, in Germany, you need a special license to be an engineer, and as a result, “Engineer” is actually really used as a title. Still seems pompous to me – I mean, technically, I’m entitled to go around calling myself Dr. Mark Chu-Carroll, PhD., but I don’t generally do that.)

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