It’s supposed to hurt to think about it! – Starts With A Bang

It’s supposed to hurt to think about it! – Starts With A Bang

One of the most fundamental questions about the Universe that anyone can ask is, “Why is there anything here at all?”

Explaining where all the matter in the Universe comes from is one thing. What you traditionally think of as something — that is, the plants, animals, elements, planets, stars, galaxies and galaxy clusters — that’s one question.

How and when all of that got here? That’s something we think we can answer.

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But there’s an even more fundamental question than that. In order to have our Universe, you need to start with what, as a physicist, I call nothing.

You need to start with empty spacetime.

And you can start with the emptiest spacetime imaginable: something flat, devoid of matter, devoid of radiation, of electric fields, of magnetic fields, of charges, etc. All you would have, in that case, is the intrinsic zero-point energy, or the ground state, of empty space.

From a physical point of view, that’s what nothing is. Only, perhaps perplexingly, that zero-point energy? It isn’t zero.

If it were, we wouldn’t have a Universe filled with dark energy, and yet we do. Instead, spacetime has a fundamental, intrinsic, non-zero amount of energy inherent to it; that’s what’s causing the Universe’s expansion to accelerate! What’s even more bizarre than that is the fact that all the matter and energy in the Universe today came from a drop, long ago, from an even higher zero-point-energy state. That process — reheating — is what comes at the end of an indeterminately long phase of exponential expansion of the Universe known as cosmic inflation.

The regions of space where this drop in zero-point energy occurred gave rise to regions of the Universe like ours, where matter and energy exist in abundance, and where the expansion of spacetime is relatively slow. But the regions where it hasn’t yet occurred continue to have an extremely rapid rate of expansion. This is why physicists state that inflation is eternal, and this is also the physical motivation for the existence of multiverses.

That’s the physical story of where all this comes from. Of where our planets, stars, and galaxies comes from, of where all the matter and energy in the Universe comes from, of where the entire 93-billion-light-year wide section of our observable Universe comes from.

From a scientific perspective, we think we understand not only where all of this comes from, but also the fundamental laws that govern it. So when a physicist writes a book called: A Universe from Nothing, I know that some version of this story — the scientific story of how we get our entire Universe from nothing — is the one you’re going to get told.

It’s a remarkable story, it’s perhaps my favorite story to tell, and it’s certainly been the greatest story I’ve ever learned. But in at least one way, it’s a dissatisfying story. Because the scientific definition of “nothing” that we use — empty, curvature-free spacetime at the zero-point energy of all its quantum fields — doesn’t resemble our ideal expectations of what “nothing” ought to be.

No one sufficiently versed in the science of physical cosmology (and being sufficiently honest with themselves about it) would argue against this: that the entire Universe that we know and exist in comes from a state like this, that existed some 13.7 billion years ago. But you may rightfully ask, “Is that truly nothing?”

This empty spacetime definition of what is physically nothing stands in contrast to what we can imagine as what I’ll call pure (or philosophical) nothingness, where there’s no space, no time, no laws of physics, no quantum fields to be in their zero state, etc. Just a total void.

This has been the source of much argument recently, as the answer to the physical question of where everything comes from does not necessarily answer the philosophical one. It certainly pushes it off for a while, but it still leaves unexplained the existence of spacetime and the laws of physics themselves. There has been bickering back-and-forth with a handful of physicists andphilosophers arguing as to whether this physical story really explains why there is something rather than nothing?

It is a remarkable story, of course, and it explains where every galaxy, every star, and every atom in the Universe comes from, an astouding feat.

But it doesn’t explain, existentially, why spacetime or the laws of nature themselves exist, or exist with the properties that they have. In short, understanding how something comes from nothing does not explain how this physical state of nothing comes from an existential nothingness. This question of why, as enunciated by Heidegger, is not addressed by our physical understanding of the Universe. But is it a fair question?

Like the oft-dismissive Wittgenstein, I’m not sure. We make this inherent assumption that both spacetime and the laws inherent to our Universe come from somewhere. Yet our classical notions and intuitions about causality are violated even within our known Universe; do we have good reason to expect that this non-universal form of logic applies to the very existence of the Universe itself? Furthermore, how can something, even figuratively, come from anything else if you remove time?

One can, of course, imagine answers to these questions: an entity of some sort that exists outside of time and thus has access to all times equally, a type of hidden-variable logic that exists as part of reality but requires the knowledge of things that are presently unobservable to us, a higher-dimensional being who sees our entire Universe no differently from how an animator sees the elements of a two-dimensional cartoon, etc.

None of these answers are convincing or compelling, mind you, and I am not sure that the questions do even make sense as far as reality is concerned. But just because we cannot yet know the answers, or whether the questions are sensible as far as reality is concerned, doesn’t mean there isn’t value to asking them and thinking about them. To me, that’s what philosophy is. I would encourage everyone to remember the words of my favorite philosopher, Alan Watts:

The reason for it is that most civilized people are out of touch with reality because they confuse the world as it is with the world as they think about it, talk about it, and describe it. On the one hand, there is the real world, and on the other, a whole system of symbols about that world that we have in our minds. These are very very useful symbols — all civilization depends on them — but like all good things, they have their disadvantages, and the principal disadvantage of symbols is that we confuse them with reality.

For whatever it’s worth, when I think of nothing, I think about empty spacetime and the physical Universe: that’s where my interests lie, and that’s where I believe the knowable lies. But that doesn’t mean there isn’t something wonderful to be gained from philosophizing. 

4 Trillion Degrees

Smash together two gold nuclei at nearly the speed of light, and that's the temperature of the explosion you get. Hottest temperature ever heads science to Big Bang.

...In comparison, "The predicted melting temperature of protons and neutrons is 2 trillion degrees. The temperatures at the core of a typical type-2 supernova is 2 billion degrees," he said.

The center of our sun is 50 million degrees, iron melts at 1,800 degrees and the average temperature of the universe is now 0.7 of a degree above absolute zero.

This research may shed light on why the early universe had more matter than antimatter, and may allow us to build devices that run off of particle spin, rather than only current flow.

The "spin" involved, is not the kind of spin that comes out of Washington DC, however. It's a property of most particles.

Do the Gods repeat themselves?

This is a question that's been floating around in cosmological circles.

For example:

If space goes on forever, then there must be other regions like ours — in fact, an infinite number of them. No matter how unlikely it is to have another planet just like Earth, we know that in an infinite universe it is bound to happen again.

Your hear that a lot from cosmologists, but it's shoddy thinking. An infinite space doesn't have to contain every possible combination of matter. It might just contain an infinity of Cabbage Patch Dolls arranged at the intersections of a cubic lattice. Or it might, beyond a certain point, just be empty. The positive odd integers 1, 3, 5, 7, 9, 11, … are an infinite set, but the set doesn't contain any even integers.

There are serious problems with this argument. First of all, we have a problem with the definition of "possible". While it's true that the set of positive odd integers is infinite, and while it's true no even integers appear in it, it also reeks of – well, design. If you pulled numbered balls out of a barrel, and all you ever found was even numbers, you might be tempted to conclude that the odd numbers had been excluded. By defining a set as "the positive odd integers", Derbyshire has defined a set which specifically excludes even numbers. Thus, under this definition, it's impossible for an odd integer to appear in the set.

Scientists work with a number of basic assumptions – axioms, if you will.

One of these is, if something exists, it's possible.

Since the Earth exists, it is, by definition, possible. (It happened.)

Since it's possible, the probability that it would actually happen in some volume of space is greater than zero. (In contrast to the probability of finding an even integer in the set of positive odd integers.)

Science also assumes no one or nothing is stacking the deck. There is no reason to assume that, because anything has appeared once, its chance of appearing in the next region of space is changed in any way. (That is, the "gambler's fallacy" doesn't apply to natural events.)

In particular, if the earth can arise in the universe once, it must have some chance of appearing in any other volume of space, however low that chance may be. And if you examine a large enough volume of space, you will hit the jackpot sooner or later.

The trick is to live long enough.

If the odds are sufficiently long, there may be no other Earths close enough to ever show up in our radar.

"Rare earths" -- maybe not

One of the stars of "Expelled" is an astronomer who argues that Earth is a rare beast -- a planet sufficiently fine-tuned for life as to be very improbable. Thus, more than chance is at work.

He says.

Another researcher thinks the sun, at least, is not that uncommon.

There's nothing special about the Sun that makes it more likely than other stars to host life, a new study shows. The finding adds weight to the idea that alien life should be common throughout the universe.

"The Sun's properties are consistent with it being pulled out at random from the bag of all stars," says Charles Lineweaver from the Australian National University (ANU) in Canberra. "Life does not seem to require anything special in its host star, other than it be close."

Some previous studies of the Sun's vital statistics have concluded that it is unusual among stars, for instance, by having a higher mass than average. Such atypical properties might somehow help explain why the Sun seems to be unique, as far as we know, in having an inhabited planet.

With his ANU colleague José Robles and others, Lineweaver has now analysed 11 features of the Sun that might affect its ability to have habitable planets. They included its mass, age, rotation speed and orbital distance from the centre of the Milky Way.

Then they compared these with well-measured statistics for other stars to answer the question – overall, does the Sun stand out from the crowd any more than some other randomly chosen star would?

The Sun did stand out in two ways: it is more massive than 95% of nearby stars and its orbit around the centre of our galaxy is more circular than those of 93% of nearby stars.

Very ordinary

But when all 11 properties were taken on board, the Sun looked very ordinary. Robles's team calculates that there would be only about one chance in three that a star selected at random would be "more typical" than the Sun.

They conclude that there are probably no special attributes that a star requires to have a habitable planet, other than the obvious one – the planet must be within the star's habitable "goldilocks" zone, orbiting at a distance where the temperature is not too hot for life, nor too cold, but just right.

Before the Big Bang

Did the universe come from nothing? Maybe not.

Maybe the universe, in some form, has always existed.

The new work suggests that time existed before the Big Bang, when a more ancient universe collapsed to give birth to the one we live in today.

Ours is the latest universe in a series that expanded, then collapsed, before another - slightly different cosmos - was born anew, though many details are obscure and, the theory concludes, will always remain that way.

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However, Dr Bojowald found a variant of a theme summed up by Heiseinberg's uncertainty principle, which puts fundamental limits on what we are able to know about the universe. "It is similar to the uncertainty relations in quantum physics, where there is complementarity between the position of an object and its velocity - if you measure one you cannot simultaneously measure the other."

Privileged planet arguments

Link to a discussion of whether Earth was "designed" to be optimally habitable for us.

Dont you know, gravity's only a theory!

Derek Gilbert points to a piece on the latest failure to detect dark matter. His take, as well as that of Tuesday Morning Quarterback and Vox Day is that this failure somehow discredits a) the dark matter hypothesis, b) the big bang, c) science in general.

Since I've complained many times about the dismal state of science education in this blog, I'll assume these comments are due to this same dismal state of science education. The assumption here is that science is supposed to be akin to Holy Writ, never admitting to flaw or error.

Science is actually a method for building models to explain how reality works. Over time, parts of models will turn out not to work, often because they are contradict by some event in reality. When that happens, that part is modified or discarded, and replaced with a part that works better. (If it didn't work better, it wouldn't be put in place of the old part.)

Another word for "model" is "theory".

That's right, gravity's just a theory.

This theory has worked pretty well, though. Since it was developed by Newton in the 18^th Century, it never needed any revision until the end of the 19^th Century. Only after careful observations of the orbit of Mercury showed that the gravitational pull of everything we knew about was insufficient to account for all the forces exerted on the planet was the theory revised. Even then, various adjustments to the model were being proposed. Among them, a planet inside the orbit of Mercury, which would have been lost in the glare of the sun. This planet would have been named Vulcan.

Eventually Einstein came up with a theory of gravitation which yielded predictions that were slightly different from those of Newton's theory, and the slight difference turned out to account for the discrepencies in Mercury's orbit.

Now, we have more powerful telescopes and we can observe how distant stars are moving through space. In general, everything we see is in orbit around something else. Stars tend to orbit, if nowhere else, around the center of mass of the galaxy they are in. And we know a lot about orbits. We know the path of an orbit is determined by the speed of an object and the amount of mass in the system. If we see a galaxy spinning at a certain speed, we know it has to have a particular amount of mass to hold together. Too little mass, and stars moving at the observed speed will fly out into space – indeed, would have already.

So we look for mass. A lot of mass is contained in stars, and a lot can be found in dust clouds. We can see dust clouds when they're illuminated by radiation from nearby stars, or when they block some of the light from stars behind them. When we add up this observable matter, we're finding that a lot of the matter that has to be there just can't be seen.

I could imagine that some dust escapes notice, but an amount at least six times the mass of all the stars in a galaxy? None of it gets in the way of any stars?

Rather than subject the theory of gravity to another major revision, astronomers prefer to believe the extra force exerted on stars comes from some undetectable form of matter. Once this form of matter is postulated, the question becomes, how does it behave? Does it interact with anything else in the universe, by any means except gravity? If so, how?

This would hardly be the first time science has attempted to introduce a new form of matter to avoid revising a theory. Two of the big theories in science are conservation of energy and conservation of momentum. These theories have been so robust they're called "laws".

Imagine the consternation when it appeared that neither energy nor momentum were conserved in some nuclear reactions. Either the laws didn't apply here, or ... maybe there was some form of matter that wasn't showing up in the detectors.

Imagine a small particle, very low in mass, possibly even massless, which carried varying amounts of energy and momentum away from certain types of nuclear reaction. It would balance the equations, and we wouldn't have to revise our theories. We even have a name for the particle. Since it's uncharged, or electrically neutral, and very small, let's call it the "neutrino".

It wasn't long before these particles were detected. Since they are emitted in certain types of nuclear reaction, they can be absorbed by atomic nuclei and force an inverse form of that same reaction. And when you put enough of the right kind of atoms next to a source that should emit lots of these neutrinos, guess what you find...

Now as it happens, the problem may be with our understanding of gravity. The jury's still out.

So far, all we know is that various guesses about how dark matter might react have been wrong. Those who are sceptical about dark matter might like to offer their guesses to account for why galaxies move the way they do. That would be doing some real science. Just be aware that any guesses offered up will be tested by people who have been studying this kind of thing for a long time. They will want to know if your guess is at least as compatible with what they've been watching as the current theory is.

What's the matter with gravity?

The two Pioneer spacecraft are not where they're supposed to be.

Big deal, you say? Well, yes it is. We're used to being able to calculate the exact magnitude of every force acting on anything we send out into the solar system. We rely on this ability. If our calculations are off, our space craft wind up missing their mark. And we don't load enough fuel to correct for very big mistakes.

John Anderson noticed a discrepancy in the positions of the two craft. It's not big – 8000 miles out of 219 million traveled every year. But it should be zero.

Anderson has spent ten years trying to rule out every possible source of error. He's invited other scientists to suggest anything he may have overlooked. So far, no one has.

Whatever the answer turns out to be, it's going to be interesting.

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If celestial mechanics had a contingent of opponents, the kind Creationists are to evolution, they would seize upon this story to claim we know nothing at all about gravity, and that Velikovsky's planetary billiards scenario is possible. Or maybe those Trancendental Meditators do levitate after all.