Stellarator wrote:Source of the post Ignoring for the moment the viability of that technology, and assuming that the Einstein-Rosen Bridge interpretation of that possible phenomena is correct, how visible would such a spatial structure be?
Let me first get out of the way that current thinking is that wormholes probably cannot exist even artificially, because of exotic energy requirements or that they may lead to causal paradoxes. That being said, in the realm of mathematical solutions to general relativity they are very interesting objects and we may like to study their properties and appearance. That leads to ways they could be found in observations, which seems to be what you're most interested in, and we'll cover how that works in some detail.
So the short answer is that a wormhole would be detectable due to how it bends light around it. From close by, the gravitational lensing effects would be very obvious (the visuals for the wormhole in Interstellar come to mind). But even from a very great (interstellar or even intergalactic) distance, the effect could still be visible as gravitational microlensing, which shows up in photometry for the light curve of a bright source passing behind the lens. This works because a lens can magnify or demagnify an image and change its brightness. Gravitational microlensing is also a method we use for detecting exoplanets, and potentially even rogue planets.
The biggest issue with microlensing events is that because they depend on a chance alignment of the Earth, lens, and a background source, they are generally one-time-only observations unless the lens lies in a sufficiently tight orbit in a bound system. Otherwise, we may know where the lensing object is on the sky, but not necessarily how far away it is with great precision, or which direction it is moving, and it may be completely invisible unless it happens to pass in front of another bright object again.
The upshot is that the microlensing signature of a wormhole should be very unique, as we'll see shortly.
Stellarator wrote:Source of the post at what distance from Earth would it be invisible to our observations using radio telescopes or other detective instruments?
This depends on the size/mass of the wormhole and the particular type (metric) it obeys. We could imagine a "supermassive" wormhole with a lensing power equivalent to a supermassive black hole, for which the strong lensing effects could be directly imaged with a network of telescopes like EHT from many kiloparsecs away. But a "more reasonable" sized wormhole 100s of kilometers across could be detected through microlensing.
As it turns out, there are numerous studies on how different types of wormholes would appear by microlensing, and even a survey to look for evidence of (natural, intergalactic) wormholes in gravitational microlensing events of gamma ray bursts. Obviously, they didn't find any conclusive evidence for them (or we'd all have heard of it already), but instead this serves to place observationally-derived limits on their numbers and masses. But more importantly for our purposes, it serves to show that the technique to look for them exists in a functional way with our current technology!
What wavelengths of electromagnetism would the presence of the wormhole be apparent on? And how would it's size (in terms of the physical aperture from which matter and energy comes in and out of) effect visibility?
These are intimately related. Any wavelength that is much smaller (say by at least a factor of 10 or so) than the diameter of the wormhole's mouth will be useful for observing it by gravitational lensing or microlensing. This is because those photons will simply trace geodesics through the curved spacetime around the wormhole.
Wavelengths that are comparable to the diameter will instead be strongly diffracted, and wavelengths much larger than the diameter would basically ignore it, like infrared light passing through dust.)
What would the light curve of a microlensing event by a wormhole look like?
It depends on a number of things, but in most cases it is very different from the lensing behavior of a typical mass (the Schwarzschild lens such as by a planet or black hole).
The classical wormhole has two mouths that each have an effective negative mass, which causes light rays to be bent away from it rather than toward it. Therefore if we image an object far behind the wormhole, the image of that object will be displaced toward the wormhole (whereas lensing by a positive mass like the Sun displaces images away from it). Here are some simulations of how a background object gets lensed by a wormhole, from Safanova et al. (2001):
Stellarator wrote:Source of the post How could an advanced civilization hide this technology, if it is readily visible at a reasonable (~1000lys) distance?
The solution here would be to screen the negative mass lens of the wormhole's mouth. A simple way to do that would be to surround it with a spherical shell made of an equal or greater positive mass, so that there is no net negative gravitational lensing around it. The light curve we see would then not betray anything unusual.
I also recommend this paper's introduction which has a pretty good review of the previous literature on wormholes and their detectability, including a lot of the above material.
Stellarator wrote:Source of the post Aside from transporting matter or energy, what other effects might the wormhole have on the immediate environment in which it is situated?
besides the lensing of light just covered, and the presence of gravitational tidal forces, I think the best I can say is... "I'm not sure"! Wormholes are quite exotic, and if they exist there may be much more to them than we currently know about. But hopefully this has been helpful material to feed your curiosity.