The blind ghost

[Physics Guy]

Particles can be created or destroyed because they aren't really what you might think they are. They are not solid little specks. They are weird.

Tiny specks do exist; they're just not the things we recognize as particles. Even empty space is constantly full of electrically charged points, half of them positive and the other half negative, all appearing and disappearing (in opposite pairs) and zipping around. For any positive point, it's overwhelmingly probable that there will be a negative point within about 1% of an atom radius of the positive point (the so-called "Compton wavelength of the electron", around 10^{-12} meters). So unless you have deeply sub-atomic resolution, space just looks electrically neutral. Zoom in close enough, though, and it's full of this sea of charged points.

These points are not what we call particles, though. Particles are certain kinds of patterns in how the charged points are distributed in space. An electron, for example, is a pattern in which there is one extra negative point with no corresponding positive point very close to it. The pattern is more than just that one extra charge, though, because all the points around it, out to about that 1% atom-size radius, get redistributed in response to the presence of that one unbalanced charge. The pattern that we call an electron has a certain coherence. It sticks together pretty well, and can move around. If you don't have that sub-atomic resolution, the whole structure just looks like a single, well, particle, with a certain mass and total charge. Only if you zoom in close do you see that an electron has a lot going on under the hood.

Empty space is also full of noisy electromagnetic waves, a kind of ultimate microscopic static. A photon is a certain statistical pattern within this electromagnetic noise, like the signal in a modulated carrier wave. The electromagnetic noise and all the point charges interact and affect each other. So electrons are not purely composed of charged particles, because part of the pattern that makes up an electron is localised correlations in the electromagnetic noise. And photons are not purely composed of electromagnetic fields, because part of the photon pattern is a localised correlation pattern among the charged points.

Consider a tiny volume of empty space, 1% of an atom radius across. It's full of positive and negative points, but they are equal in number and their distribution pattern is just the default pair correlation of zero energy. The electromagnetic field is also just doing its empty-space thing. So there are no particles here. But then a couple of gamma ray photons happen to meet right in this little volume. The electromagnetic field suddenly has this enormous spike; strong electrical forces pull positive and negative points in opposite directions. Accelerating those charges drains away the electromagnetic field, so the gamma rays are absorbed, but the result is that we have a net positive charge on one side of our tiny volume, and a net negative charge on the other side. When everything shakes itself off, the new distribution of charged points in this region isn't the balanced pattern of empty space any more. Instead it's an electron sitting next to the negative mirror-twin of an electron—a positron. The gamma ray photons have been annihilated and a pair of oppositely charged massive particles has been created out of "nothing".

That's all pretty exotic, with gamma rays and anti-matter (the positron). A very similar process is likely happening before your very eyes right now, however. Light-emitting diodes (LEDs) like the ones in your computer screen work by a similar process in reverse. An LED is a hunk of semiconductor, not empty space, but it recapitulates the story of correlations among positive and negative charges, just on a larger scale now (several atom-widths, so about 1000 times larger). The role of the fundamental negative points is now played by the correlated patterns we call electrons, while the role of the fundamental positive points is played by the much heavier ions that make up the lattice of the semiconductor.

Within this balanced background of positive and negative charges there can again be coherent patterns of net positive and negative charge, which hold together as they move around. These coherent patterns get called "quasi-particles", because they are not the primary, fundamental particles; but they are qualitatively just the same kind of coherent-pattern thing as a "true" particle, just on a larger scale. Thinking about these quasi-particles as "just another kind of particle" is kind of like thinking of corporations as biological organisms, except that the analogy is less strained in physics. All particles really are "quasi". It's just a matter of scale.

If you apply an electrical field to an LED, the positive and negative charge patterns get pushed in opposite directions; they smack into each other. When they collide at close range, their patterns can merge into neutrality, exciting photons in the electromagnetic field. This is like the reverse of the process I mentioned above; this time a positive and a negative "particle" meet and annihilate each other, emitting photons. That's how LEDs glow. The LED analog of the other process, with photons getting converted into charged particles, is a photo-voltaic cell that generates current when it absorbs light.

[Physics Guy]

Why is the universe expanding? This isn't necessarily even a physics question, because it's like asking, "Why is that baseball rising?" The baseball is rising because a short while ago it had some upward momentum. No ongoing power source is needed to explain the baseball's current upward trajectory. That was the fallacy of Aristotelian physics, which Newton corrected by postulating inertia.

Gravity is slowing the baseball's rise, and will likely bring it back down again soon, but for a while the baseball will keep rising. In fact if the baseball's initial speed were above its escape velocity, due to one heck of an out-of-the-park slug, then the baseball would keep on rising forever, flying off into space.

In General Relativity the universe can expand just as that ball can fly upward. The universe doesn't need any ongoing push to keep it expanding. The mutual attraction of all the mass in the universe tends to slow the expansion, but if the expansion is initially fast enough, the universe may collectively escape its own gravity, such that it just keeps expanding forever.

In the baseball case we can continue to ask how the baseball got that upward momentum. We'll get into elasticity of the wood in baseball bats, the neurophysiology of hitting and pitching, and the economics of spectator sports. In the case of general relativistic cosmology, unfortunately, the beginning of the universe is currently beyond the reach of our understanding. Even if the explanations for the expansion are within the realm of some kind of physics, they are not within the realm of currently known physics.

There is a further story about so-called dark energy. The expansion of the universe does not seem to be slowing. Instead it seems to be accelerating. It's as if that rising baseball were gaining upward speed as it rose. That is not just inertia; it does require some kind of ongoing power. "Dark energy" is simply the label that has been attached to "whatever is powering the acceleration of the expansion". It's not clear (at least not to me) how much of the universe's expansion is due to dark energy and how much is due to initial momentum. At least in the simpler models for how dark energy works—models which do fit the observations well so far—the effect of dark energy gets larger the bigger the universe is. So if this is true, dark energy alone cannot have caused the expansion in the first place, because it would have been a negligible effect back when the universe was small.

It's also not clear how hard we should be trying to explain dark energy. There's a natural fudge factor in the basic equation of General Relativity (the "cosmological constant"). In vanilla GR this factor is taken to be zero, but once you recognize that it could in principle be non-zero, it's hard to say why it should be anything in particular whatever. We don't know any rules that would govern it, other than tuning it as a fudge factor to bring the theory into line with observations. To fit the observations about the accelerating expansion of the universe, the cosmological constant just has to be tuned to a certain small value.

Nobody likes just leaving it at that. But the problem of explaining dark energy isn't really about dark energy, but about finding some kind of more fundamental rule that tells us what the cosmological constant should be. Until we find that rule, explaining the expansion acceleration is a mug's game, because there's a big unknown fudge factor that could cancel out every other effect anyway.

[Rivendale]

So I guess Lawrence Krauss is guilty in some respect for redefining nothing. I would speculate that if nothing was a thing it would be something.

[dantana]

Well, as host of this thread, I feel like a - thanks guys for the posts, is seriously inadequate. But, I got nothing right now. Anyway, thank you Gadianton, Physics Guy and Rivendale!

[Rivendale]

Anyone up for a little science fiction? Or, as some would probably say, science fantasy.

Physicalism posits that particles rule. Particles and forces are all that really matter and the phenomenon of consciousness is just a result of the mindless interaction of particles. All quite maybe true, but - if particles are eternal, and how could they not be? I mean, I understand that particles have been shown to pop into existence in a vacuum, (maybe they are just coming from somewhere currently un-measurable). Anyway, it is just so hard to grasp the concept that particles/existence popped into existence from non-existence. (This doesn't mean I'm saying God did it)

So, if particles and forces just are. Are eternal and infinite, then the phenomenon of consciousness that they create is just as eternal. In an infinite system, how could there ever be a point or time when particles hadn't yet organized to the complexity to create the consciousness?

Yeah, so what, you say. This still doesn't mean that individual entities have a soul. The consciousness abates when the body dies and the particles disassemble.

What if though, a society of intelligent beings were able to survive long enough to learn everything there is to know about the ways of particles and forces. If they were able to figure a way to record the specific energy pattern of the individual, and encode it at a sub-atomic level, or whatever. A recording that could survive the big crunch and the big bang and be reconstituted with a transmogrifier machine... or whatever. Then for all intents, there is your eternal soul.

A billion years from now, Joe Montana is throwing passes again. And none the wiser. He didn't spend any time in some fuzzy spirit world but, he didn't think that place made any sense anyway.

https://en.wikipedia.org/wiki/IBM_(atoms)

https://calvinandhobbes.fandom.com/wiki/Transmogrifier

Here is something that is partially science fiction but I have always found fascinating. Our radio and tv signals have only been traveling a little over a 100 years. A civilization a 100 light years away is just receiving them. But If they had the technology to capture the photons that reflected from Earth, say from a person or the landscape. They could actually watch a movie of Earth's history. Or to restate it. Every second of your entire life is still out there at some position in space.

[dantana]

Here is something that is partially science fiction but I have always found fascinating. Our radio and tv signals have only been traveling a little over a 100 years. A civilization a 100 light years away is just receiving them. But If they had the technology to capture the photons that reflected from Earth, say from a person or the landscape. They could actually watch a movie of Earth's history. Or to restate it. Every second of your entire life is still out there at some position in space.

Keep em coming Rivendale. You're good at this!

[Physics Guy]

I don’t know how viewable the signal would be at great distance. Objects separated by a distance D are only resolvable from each other from ranges R less than around DA/L, where L is the light wavelength and A is the diameter of the lens or antenna being used to focus the light. If you want the aliens to be able to see you, you’ll want D no bigger than maybe 10cm, so they can at least roughly resolve the outline of your body. The wavelength had better be in the visible spectrum, or else there‘ll be too much attenuation in the atmosphere. So L can’t be too much less than a micrometer. So with D/L = 10^5, the aliens will need a lens 100 million kilometers wide per light-year of distance, if they want to resolve you. I doubt anyone will invest that kind of effort just to watch your life from great distance in the future.

Even to resolve the whole Earth as more than a point source needs an antenna about a kilometer wide per light-year of distance. This is our problem looking at exoplanets: we can’t just zoom in on them. Astronomy doesn’t really use light the way our brains use light, to resolve where things are in space. Instead it mostly uses light the way our brains use sound, recognizing signals by their frequency signatures. You can’t hear exactly where the first violin is sitting in the orchestra but you can definitely tell the strings from the brass. In the same way, we can’t resolve land and ocean on an exoplanet but we may be able to tell whether there is water there or only methane.

Even though there is no sound in space, and astronomy is all about trying to capture very faint light, you get a better idea of what astronomy is trying to do with that light by thinking of closing your eyes and listening hard.

[Rivendale]

I don’t know how viewable the signal would be at great distance. Objects separated by a distance D are only resolvable from each other from ranges R less than around DA/L, where L is the light wavelength and A is the diameter of the lens or antenna being used to focus the light. If you want the aliens to be able to see you, you’ll want D no bigger than maybe 10cm, so they can at least roughly resolve the outline of your body. The wavelength had better be in the visible spectrum, or else there‘ll be too much attenuation in the atmosphere. So L can’t be too much less than a micrometer. So with D/L = 10^5, the aliens will need a lens 100 million kilometers wide per light-year of distance, if they want to resolve you. I doubt anyone will invest that kind of effort just to watch your life from great distance in the future.

Even to resolve the whole Earth as more than a point source needs an antenna about a kilometer wide per light-year of distance. This is our problem looking at exoplanets: we can’t just zoom in on them. Astronomy doesn’t really use light the way our brains use light, to resolve where things are in space. Instead it mostly uses light the way our brains use sound, recognizing signals by their frequency signatures. You can’t hear exactly where the first violin is sitting in the orchestra but you can definitely tell the strings from the brass. In the same way, we can’t resolve land and ocean on an exoplanet but we may be able to tell whether there is water there or only methane.

Even though there is no sound in space, and astronomy is all about trying to capture very faint light, you get a better idea of what astronomy is trying to do with that light by thinking of closing your eyes and listening hard.

Completely agree with the engineering problems that a civilization would encounter if they tried to intercept that information. What I find fascinating is that the information , however limiting is there. Incidentally I was asked to provide a circumstance that is unprovable but true. This was during a debate about theism. The thought experiment I come up with was shining a light into the sky. With the expansion of the universe there is a point in a photons journey that a mirror could be placed to reflect it back and retrieve the photon. But anywhere past that point you can never retrieve the photon even though you know you pushed the button on the light source. A particle of light that is out there but as of now impossible to prove it is.

[dantana]

So I guess Lawrence Krauss is guilty in some respect for redefining nothing. I would speculate that if nothing was a thing it would be something.

Howbout, the definition of nothing - What a dead guy experiences when he's dead, as per physicalism.

[Rivendale]

So I guess Lawrence Krauss is guilty in some respect for redefining nothing. I would speculate that if nothing was a thing it would be something.

Howbout, the definition of nothing - What a dead guy experiences when he's dead, as per physicalism.

I think it was Aristotle that had the quote "nothing is what rocks dream about" and evangelicals quote this often. I don't think the lack of subjective experiences would classify as nothing. The physical matter that previously was a living organism is still something. Similar to a jpeg image stored on a computer. Is the image something? Is the image turned to nothing when the hard drive is wiped?