Traditional view of a Dyson's sphere. Metamaterials could mask and alter the observable signature and alter the interaction with magnetism and the spectrum of space.
The theory of dark matter is that 85-90% of the mass in the universe is dark and does not interact with the electromagnetic force.
Recently there has been the design of metamaterials for magnetic shielding/invisibility Previously there has been work and designs for metamaterial to move microwaves, visible light and other wavelengths around a shielded region. There has also been recent progress on direct conversion of radiation into electricity and the highly efficient conversion of heat into electricity.
Scientists could use the metamaterial as a building block for a magnetic invisibility cloak. Such a cloak could hide magnetism by guiding an applied magnetic field around a cloaked region.
An advanced civilization could create a Dyson shell with metamaterials on the outside for guiding light, heat and magnetism around the shell [Dyson shell is converting all of the planets in a solar system into solar collecting satellites that orbit the star at about the distance of the earth. The structure lets you use all the solar energy of the star which would be over a trillion times more energy that our civilization uses]. Their shell would then have minimal interation with light and magnetism.
I had previous postings on the Fermi Paradox.
My speculation about technology and aliens is that we do not know what civilizations with technology able to explore the galaxy would be using. The Fermi paradox itself is based about speculations about aliens.
UPDATE: Centauri Dreams has an excellent follow up to this article on what aliens might do with Dyson spheres and current efforts to look for Dyson sphere building aliens.
Some the Fermi speculation is on dyson spheres and dyson shells (visible megastructures) or visitations to our world. The megastructures might not be the easiest things to spot. They might look like some large infrared source about the size of earth's orbit. Light would all be captured. Plus we are now learning how to convert heat to electricity in a very efficient way. A highly advanced civilization could be so efficient that they fade into the background of space.
We could be way off base trying to predict what a civilization hundreds, thousands or millions of years more technologically advanced than us would be doing.
Rolling back a few hundred years. An advanced civilization would be burning all of the forests for wood fuel or the new coal etc...
A bit before that an advanced civilization would be breeding and domesticating bigger animals and making sailing ships with 100 to 1000 sails.
Really advanced aliens could have some kind of controlled big bangs. Some high density pocket universes for power sources or they can leave this universe/dimension and travel to or make their own more productive places. People have talked about wormholes for possibly traveling within our universe but that kind of control of space and time means they could make their own dimensional places. I am not saying that this scenario is likely but we do not know that the dyson sphere/shell scenario or the Jupiter brain scenarios are the high probability end state technology version either.
So looking on planets and around stars could be like primitives looking into the best caves and wondering where the advanced people are. Cave and tree dwelling was common 100,000 years ago. Projecting out another 100,000 years in tech development is even more futile. Plus with accelerating tech even projecting out 50-200 years is very, very difficult.
Many people have an over-estimation of how much we have seen with astronomy.
Up until a decade or so ago humanity had not detected the wobbles in nearby stars caused by extrasolar planets. Up until that point planets around other stars was speculation. Up until the recent discoveries it was assumed that those planets would also have circular orbits like most of the planets in our system. Now the feeling is that non-circular orbits are more common.
If a dyson shell or sphere obscured a star then it is not like we would like in that area and say that a star was missing. There might be some difficult to detect infrared smudge. There are large voids in space without visible stars or galaxies. One is a billion light years across. We do not how that happened or if the stars and galaxies in there are just more sparse and difficult to see. Until now, optical surveys have found no voids larger than 80 megaparsecs wide – making the new hole 40 times larger in volume than the previous record holder. So there are plenty of gaps in our observations.
Our observations of other galaxies is pathetic. It was not until Edwin Hubble in the early 1920s using a new telescope that it was determined whether some nebula were galaxies. He was able to resolve the outer parts of some spiral nebulae as collections of individual stars and identified some Cepheid variables, thus allowing him to estimate the distance to the nebulae: they were far too distant to be part of the Milky Way. In 1936 Hubble produced a classification system for galaxies that is used to this day, the Hubble sequence.
Beginning in the 1990s, the Hubble Space Telescope yielded improved observations. Among other things, it established that the missing dark matter in our galaxy cannot solely consist of inherently faint and small stars. The Hubble Deep Field, an extremely long exposure of a relatively empty part of the sky, provided evidence that there are about 125 billion galaxies in the universe.
But those galaxies of billions and trillions of stars are smudges. We can say practically nothing about the composition of those smudges. We can now only determine what is or is not a galaxy based on redshift and pulsars to determine distance. If we now know whether some galaxies have a certain order of redshift, this tells us what about whether there is an advanced civilization inside. If an advanced civilization tore apart their own galaxy and remade it into something else, then how we would know that we should be seeing a galaxy where there is none now. If they did this in the two million years but are not in our galaxy then we would not have any light to observe from this event. If they did it within the last 100 million years but are not in our supercluster of galaxies then again we would have no light for those events.
Our own Milky way galaxy was recently found to be twice as fat as we thought. (12000 light years instead of 6000 light years.)
The Andromeda galaxy in 2007 was found to be five times bigger than previously thought.
From our observation, we can not tell what is or is not inhabited. We cannot tell what is or is not natural. We can make assumptions, but we do not know. If another civilization was to look at our solar system and all they could get was the light from our star and maybe if they were had good telescopes whether or not Jupiter passed in front of our star, what could they say about life on earth which they do not know is there ? What could they say if we had molecular nanotechnology and super AI and fusion power and one hundred times the population and terraformed Mars and Venus and have spaceships flying around the solar system. Looks the same still a star.
What if they were looking from a five thousand light years away at a shot of tens of millions of stars. If we had erected a dyson shell and now our star is obscured. Would there picture of ten million stars be different from ten million + 1 stars ? Would they be able to determine from gravitational tracking that there was an obscured star ?
How about if they were looking at the galaxy ? If they are inside the Milky Way and do not know whether there are 100 billion stars or 2 trillion stars then what can they say about life, even advanced life ? What if those aliens had only indirectly detected 200 planets and most that are 10 times the size of Jupiter or bigger ? What if there radio telescopes could not pickup radio signals from an equivalent civilization because the transmissions become attenuated and fade into the background. What if the civilization is just now still finding planets larger than Pluto in their own solar system and may not have spotted 100 objects of the size of the moon to the Pluto or bigger.
A d.c. magnetic metamaterial: Nature Materials
Electromagnetic metamaterials are a class of materials that have been artificially structured on a subwavelength scale. They are currently the focus of a great deal of interest because they allow access to previously unrealizable properties such as a negative refractive index. Most metamaterial designs have so far been based on resonant elements, such as split rings, and research has concentrated on microwave frequencies and above. Here, we present the first experimental realization of a non-resonant metamaterial designed to operate at zero frequency. Our samples are based on a recently proposed template for an anisotropic magnetic metamaterial consisting of an array of superconducting plates. Magnetometry experiments show a strong, adjustable diamagnetic response when a field is applied perpendicular to the plates. We have calculated the corresponding effective permeability, which agrees well with theoretical predictions. Applications for this metamaterial may include non-intrusive screening of weak d.c. magnetic fields.
A collection of links on Dyson shells
Discussion about aliens and Dyson shells and spheres with some excerpts below.
An energy balance calculation of the temperature inside a dyson sphere. Assuming that energy is lost only by blackbody radiation, and that inner (absorbing) and outer (emitting) surface areas are the same, a dyson sphere at 1 AU from the sun would equilibrate to a temperature of 396K = 123C. Clearly, this is unacceptable.
To achieve stable temperature of 33 C (still a bit warm if you ask this canadian), the sphere would have to be at about 1.7 AU or have an effective radiating area (fins?) about 3 times the inner absorbing area.
A Dyson shell has to radiate eventually because the thermodynamic gradients that power everything need a heat-sink. If we dump heat as microwaves just a bit shorter than the CMB, at a radiator temperature of 3.25 K, then the radiator surface has to be ~ 20,768 AU in radius to handle the Sun’s output. A lower output temperature means a much larger radiator. I seriously doubt anything can be made that big except for very tenuous gas.
So what’s to be done? A civilization needs thermodynamic gradients and so at some temperature it must radiate. Perhaps the old SF idea of “cooling lasers” might be feasible? By dumping heat as a coherent beam pointing into the intergalactic void, advertising one’s presence to the galaxy might be avoided. In that case I suspect a real Dyson sphere will be needed to manage the Sun’s light, instead of the Dyson Swarm that Dyson himself imagined.