The remarkable emptiness of existence
nautil.us
nautil.us
That's actually not true. Space is actually expanding, meaning new space is coming into existence and no one really knows what that looks like at a quantum level. Then again, we don't know how gravity works at a quantum level either.
The quoted figure is 72km/s/MPsc (+/-5). That means if two objects are 1 megaparsec apart (3.26 million light years) then space itself is expanding between them at the rate of ~72km/s.
Dark energy is really the fudge for all this. The idea is that creating new space takes energy. That has to come from somewhere and dark energy is our fudge factor for that. No one really knows what dark energy is or looks like just like we don't know what creating new space looks like. It just solves a conservation problem.
This isn't gravitational repulsion. It's why the universe is ~13.8 billion years old but we can see the light of objects that we now estimate to be >40 billion light years away. Space itself has expanded. It's not gravitational repulsion.
> In our most advanced quantum theories, we can calculate the energy contained in the vacuum, and it’s infinite. As in, suffusing every cubic centimeter of space and time is an infinite amount of energy, the combined efforts of all those countless but effervescent particles.
That's not true either. The calculation of vacuum energy by QFT isn't infinite. It's just really, really large. This is one of the largest errors between theory and observation in all of physics because the measured energy of a vacuum is ~120 orders of magnitude less. This is a well-known (and open) problem known as the vacuum catastrophe [1].
Lastly, on empty space, it's well-known that atmos are mostly empty space (as the article notes). I mean this is why neutron stars can be so dense. But it's worse than that. The nucleus itself (already a tiny portion of an atom's volume) is mostly empty space. Nucleons are made up three quarks and those quarks are tiny compared to the nucleon's size.
[1]: https://en.wikipedia.org/wiki/Cosmological_constant_problem
That formulation strikes me as being a Rutherford model tier of wrong.
My layman’s understanding matches up with what you said, and my curiosity about this is what brought me to the comments. What I don’t get is that the author appears to be an astrophysicist who must surely understand the difference. Can someone shed more light on this? E.g. is there a version of the theory where these formulations are equivalent?
The most charitable interpretation is that the author has dumbed down the theory to make it digestible by the layman and in doing so has used a bad analogy. But I think you can correctly describe the core concepts in simpler terms that are a lot closer to taht theory.
Gravity works a bit different at the scales we are talking about, but generally we would expect an expanding universe filled with only matter and radiation to slow down and eventually collapse back into itself. Or at least it would slow down and approach some constant velocity. Not unlike a ball that you kick into the air with below or above the escape velocity. But what we actually observed in the late 90ies is that is indeed not slowing down, but accelerating, as if some force was pushing it apart. The cause of this - whatever it may be - has been dubbed "dark energy". At these scales we don't think of gravity as a "force" like we did in Newtonian physics, so I don't think it's wrong at all to say that dark energy has the opposite effect of matter and is pushing the universe apart, i.e. has an repelling effect.
To add:
Masses repelling and space expanding would have the same effect on the observable universe boundary: linear models break down.
However, light redshifting, where more distant objects are more redshifted, fits with expansion. That cannot be explained by gravity. (Whether it's expansion or some other mechanism is still unknown, AFAIU.)
Does it really make sense to even refer to the "size" of a point particle? In physics there's really no such thing as a "solid" object that has a "volume". It's just fields of a certain radius and the centers of those fields we refer to as the "location" of a zero-volume entity.
This is news to me. The story I was taught was that Einstein's equations predicted a universe that wasn't static, i.e. an expanding universe. Einstein didn't like that and introduced the cosmological constant to leave the possibility of a static universe. Then, it was found that it was indeed expanding. Einstein promptly regretted his decision ("biggest blunder") to introduce the cosmological constant. Then, it was found that the universe was not only expanding, but expanding in an accelerated fashion. That is at odds with Einstein's equations without the cosmological constant, so it was re-introduced, but with the opposite sign. If you interpret the cosmological constant as part of the already present energy-stress tensor, it could represent the energy density of vacuum itself. That is only one interpretation of "dark energy" though, as the term is an umbrella term for whatever is responsible for the acceleration.
Energy conservation never entered the discussion. In fact, energy conservation generally isn't even expected to hold in cosmology. Energy is not even well defined, as it is directly associated with time translation invariance as per Noether's theorem, which doesn't exist in an expanding universe. See: https://www.preposterousuniverse.com/blog/2010/02/22/energy-...
> The calculation of vacuum energy by QFT isn't infinite. It's just really, really large. This is one of the largest errors between theory and observation in all of physics because the measured energy of a vacuum is ~120 orders of magnitude less.
They are infinite if we sum up all frequencies naively. But just like with renormalization, we kinda say handwaveingly that we can probably cut off frequencies at the Planck scale, and then we arrive at this number 120.
That's simply not true. You don't need energy to create new space (and you wouldn't magically get energy from nowhere if the universe were contracting). General relativity gives you expanding (or contracting) space just fine if dark energy doesn't exist -- in fact, that was the most common cosmological model before the late 1990s discovery that the expansion was accelerating.
The fact that the simplest version of dark energy is the cosmological constant tells us your basic idea is wrong: if that energy was going into creating new space, then it would decrease over time, not remain constant.
In fact, it's worse than that, because the cosmological constant is a constant energy density. So if expansion doubles some volume of intergalactic space, then the total amount of dark energy also doubles (while the total energy in the form of ordinary or dark matter stays the same, and the energy in the form of photons decreases due to redshifting).
Conservation of energy in general relativity is messy and sometimes counter-intuitive; e.g. https://math.ucr.edu/home/baez/physics/Relativity/GR/energy_...
But that idea could be tested, the more flat the space becomes, the more "positional" push-back by the bubbling space a space faring object would experience.
1. There is variance in matter distribution. If fusion created or expanded space I would assume there'd be a measurable variance in the wavelength of the cosmic microwave background;
2. The initial phase of the Universe was a massive period of inflation. This was before atoms could exist (and thus fuse) so to be consistent this would have to be a different mechanism;
3. The energy released by fusing light nuclei comes the nuclear binding energy (ie the strong interaction). So the nuclear binding energy of a helium atom is less than twice the nuclear binding energy of two hydrogen atoms. As you note, this goes as far as iron because this pattern is no longer true (ie the heavier fused element has more binding energy than the two lighter elements combined). I believe this particular conservation is "solved" or at least consistent with established theory, specifically QCD.
4. Fusion in stars is highly localized. Think of the volume of the Sun compared to the volume of every point in space to which the Sun was the closest star (ie approximately 2 light years in radius). It is astronomically small. To may layman's intuition it seems like this would be measurable in some way.
We know spacetime curves (based on the energy and mass present). We have detected the compression of space (ie gravity waves). We also know there is a minimum distance between objects (ie the Planck length) but (AFAIK) space isn't discrete as that might suggest.
There are huge gaps in our understanding of any of this.
I have no idea what im doing, i just like to take a idea and run with it.
The linked paper -- https://arxiv.org/pdf/2212.11319.pdf -- isn't about measuring dark energy at all. (It's using data from a study meant to do that, but it's looking at something else.)
Also, > This phenomenon has various names: the quantum foam, the spacetime foam, vacuum fluctuations.
This confuses two different phenomena. The vacuum fluctuation of known quantum fields (electromagnetic, electron, Higgs, etc.) is what is thought to give rise to the cosmological constant/dark energy, and is what this article is about. (A limited version of it involving the electromagnetic field produces the Casimir effect, which has been measured.) "Spacetime/quantum foam" is the hypothetical fluctuation of spacetime itself, assuming a quantum theory of gravity. It has nothing to do with dark energy.
That might in handy, if only we could tap into it.
So when some wise guy tells you "well so what if we're 8 billion, Earth has plenty of land for more people" think about that. We're not in balance, and reality has a way of getting back to balance one way or another. If not through wisdom and intelligence, then through brute force.
Emptiness is an abundance of environment. It's all it is. Then you have the freedom to play. If your environment is scarce, your resources are scarce, then existence becomes an increasingly desperate play in which no one wins.
BTW when looking for "aether"... consider the stupidity of a water wave... looking for and not finding the water it's a wave of. It's all I'll say, if you need more, ask me.
This framing of "balance" and "reality" has some unsettling undertones imo, in a world where resources are plentiful enough in raw terms but there are other barriers to people accessing them. What's your suggested path back to "balance?"
https://upload.wikimedia.org/wikipedia/commons/thumb/1/17/Di...
The Earth is big, really big, but 8 billion humans and their livestock are also a really big number.
For example how much forest should there be between two cities, to produce the oxygen you're breathing right now? Many magnitudes higher than those 10m. I'm still barely scratching the surface.
As for suggestions... I don't even feel like going there today, I'm merely acknowledging my observations about realities that I believe are not up to our opinions. Reality is hugely empty, and when it's not, it's turbulent, vicious, and violent, like the center of our Sun. A neutron star. A black hole.
These are concepts of "density" and properties of the resulting system, which we can apply not only in physical context, but also biological, and social. All systems are alike in some basic fundamental ways.
But it's also weird to say that you'd need more forest then that, as though it's mutually exclusive. Our suburbs can be extremely green filled, as can our cities, but probably more notably is the simply wrong element of it: the Earth is at no risk of running out of oxygen due to "too many human beings".
PS:
Of note [1] it's not a super reliable source, but this eyeballs that you'd probably need about 10,000 leaves or 700 house plants[2] (keeping in mind a houseplant is very small, so a large tree probably does substantially better).
[1] https://gizmodo.com/how-many-plants-would-you-need-to-genera...
[2] https://medium.com/@candidegardening/how-many-plants-would-i...
Nothing contains all things. It is more precious than gold, without beginning and end, more joyous than the perception of bountiful light, more noble than the blood of kings, comparable to the heavens, higher than the stars, more powerful than a stroke of lightening, perfect and blessed in every way. - Otto von Guericke
I do enjoy some of the popular science articles from this source, but this headline begs a silly question.