Sci-fi Primers: Remote Sensing - Part 3
Common barriers, tropes and errors on remote sensing in sci-fi
Common Mistakes in Remote Sensing
In part 2, we covered the science around remote sensing (“ship sensors”) in science fiction. Now, we’re going to cover how the science often gets misinterpreted, or how long-standing tropes propagate mistakes. I advise reading the No Finger Wagging policy first.
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A Closer Look: Long-Range Scanners
According to the Star Trek Freedom Wiki, in Star Trek Land long-range sensors consist of the following:
· Wide-angle active EM scanner
· Narrow-angle active EM scanner
· 2 meter diameter gamma ray telescope
· Variable frequency EM flux sensor
· Lifeform analysis instrument cluster
· Parametric subspace field stress sensor
· Gravimetric distortion scanner
· Passive neutrino imaging scanner
· Thermal imaging array
Perhaps not an official list, but good enough for our discussion.
An array of 9 instruments that presumably give the crew all the intel they need to study a planet, explore astrophysical phenomena, and communicate with and battle enemy ships.
The elephant in the room here is how fast these instruments gather that information. In Star Trek Land, all of these operate at Warp Speed (i.e., faster than light). According to our current understanding, that is not possible in our universe.
5 of these instruments are explicitly based on electromagnetic (EM) radiation: wide-angle active EM scanner, narrow-angle active EM scanner, variable frequency EM flux sensor, 2 meter gamma ray telescope, and thermal imaging array. These are the most realistic of the lot, and resemble instruments that exist on contemporary space probes. For example, the active scanners presumably scan the interior of a spaceship by looking how much EM energy aimed at a target gets reflected (much like body-scanners at the airport). However, these are not practical with modern technology (to study any large object over astronomical distances would require truly enormous amounts of energy to be directed at the target).
The gamma ray telescope would allow for detecting high-energy events such as cosmic rays, supernovae, nuclear explosions and perhaps advanced alien technology. However, this wouldn’t allow good detection of things on the surface of a planet, as planetary atmospheres are opaque to gamma rays (see part 2).
The other 4 instruments are more mysterious. Let’s look at them separately:
Lifeform analysis instrument cluster
I assume that these pair with the thermal imaging array sensitive to infrared, for detecting heat signatures or other signs of life on the surfaces of planets or in other spacecraft.
Thermal imaging is a mature technology in the real world, so there’s no fundamental issue with this. Satellites can and do measure things like wildfires in rainforests and heat blooms around cities. However, using thermal radiation for studying individual lifeforms from space is probably not possible.
There are lots of reasons for this, but I think the most relevant are:
Hot-blooded organisms (at least on Earth) do not maintain a body temperature so much higher than the environment that they’d be easily detectable from a great distance. You’ve seen night-vision goggles in movies, which operate on infrared, but this is blurry at long distances, and (as anyone who’s seen Predator can tell you) things like volcanic plumes, sunbaked rocks or other sources of heat will be indistinguishable from something living.
Cold-blooded life (like amphibians and reptiles) will adopt the same temperature as their environment, so won’t show up in the infrared at all.
However, using infrared for general astronomical purposes, such as measuring the composition of a planet’s atmosphere, is very possible (the James Webb Space Telescope is doing exactly this at the time of writing). In principle, this might be used to detect biosignatures of alien life, though the science on this is far from settled.
Parametric subspace field stress sensor
There’s not much to say about this one, other than that subspace/hyperspace isn’t a thing in the observable universe, at least not in the glowy-other-space way that appears in sci-fi. There’s nothing wrong with positing something like this and making up your own physics, but just to clarify: we have not discovered anything resembling this thus far.
Passive neutrino imaging scanner
Some kind of neutrino detector would be very interesting when exploring deep space. Neutrinos are a family of elementary particles (the basic building blocks of the universe that, as far as we know, aren’t themselves built out of even smaller things). They seldom interact with solid matter and can pass through a light-year of solid lead without interacting with it once—in fact, neutrinos were first discovered because of an accounting error (some stuff went missing and we couldn’t find it), not because somebody saw one.
Neutrinos also appear in sci-fi as a means of communication, presumably because they aren’t absorbed by anything and so can pass easily from source to receiver. I most recently saw it feature as the means of sending a deep-space distress call in Alien: Covenant. This tendency not to interact with anything, however, would also preclude them from interacting from anything you might want to make your neutrino detector out of—and so you wouldn’t be able to receive a signal. In reality, neutrino detectors have to be truly enormous and built in some of the most isolated environments on Earth (for example, the Super-Kamiokande neutrino detector [pictured below] in Japan is housed under a mountain).
![Super-Kamiokande Neutrino Detector Helps Scientists Find Dying Stars Super-Kamiokande Neutrino Detector Helps Scientists Find Dying Stars](https://substackcdn.com/image/fetch/w_1456,c_limit,f_auto,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2Fe1d0760d-84bf-4f99-8850-5752f7e8f1b9_700x525.png)
So, neutrino detector in a spaceship: good idea, probably impossible to build one small enough to fit on a ship of a reasonable size.
Gravimetric distortion scanner
The idea here is to produce a gravity map of the environment. Sounds great—we don’t want to be sucked into any pesky black holes!
Gravity maps exist in real life, and real space missions do have gravimeters aboard to perform these experiments. However, building a gravity map of, say, a planet, requires orbiting the planet many times. The instrument is basically ‘feeling’ the gravity in different places to get an idea of the shape of the gravity well.
Unfortunately, there’s no way to get a an idea of what planetary-scale gravity wells might be in the neighbourhood just by sitting still and sending good vibes into the void.
Now that we’ve covered long-range sensors as presented in popular sci-fi, let’s explore some more general misconceptions.
Instantaneous Communication
As discussed in part 2, any real form of communication requires some finite time to travel from A to B, and so there is always some form of delay.
Instant communication between planets or stars is convenient for storytelling but is one of the most egregious errors (and a sure-fire way to boot people who know their fundamental science out of the story).
Faster-than-light (FTL) communications are a staple of sci-fi, the same bending of the rules as FTL travel. There’s nothing wrong with making something up to achieve this, but I advise staying away from vague allusions to quantum entanglement—it has been well established that entanglement cannot enable FTL communication.
4K Interplanetary Zoom Calls With Crappy Tech
High-fidelity holograms or audio-visual feeds transmitted across vast distances are common in sci-fi. This isn’t impossible in principle, but it’s certainly difficult.
This is because the rate at which data can be transmitted is fixed by several factors:
The size of the antenna
The power of the transmitter
The bandwidth (the range of frequencies) available to transmit
Whether transmissions/receivers are directed or omnidirectional
Unless the speaker and receiver are relatively close together (between the ground and orbit), high-quality transmissions are very difficult to achieve. It is possible to accomplish this by using very large antennas, lots of power, and beaming your transmissions using lasers, but all of these have their limitations.
Using AI To “Upgrade” Signals
The idea that AI can be used to get around the laws of optics (such as the diffraction limit) is spreading, and indeed AI is being used in real astronomical observations.
But it’s important to distinguish what’s actually happening: in most cases, AI is being used to do the grunt work of sifting through vast amounts of data and throwing away all the stuff that isn’t interesting. Or, it’s being used to automate time-intensive but repetitive tasks.
In cases where AI is being used to directly tamper with images and remove certain features or upgrade the resolution, it’s important to understand that the algorithm is inferring what was probably there, based on statistical properties of the image compared to the properties of lots of examples the algorithm has seen before. It’s informed guesswork. It’s very likely to get it right almost all of the time, but it can at any moment be dead wrong.
Seeing Across the Solar System With Tiny Instruments
Also covered in part 2 was the diffraction limit, which sets the maximum resolution of an image that can be achieved with an instrument with an aperture of a given size (see part 6 for details).
That basically means it’s physically impossible to get high-quality images of things really far away in a short observation time, using small equipment.
The calculation isn’t easy to run without a decent knowledge of mathematics, but space telescopes such as the Hubble Space Telescope are a good example of the kind of sizes required. The main mirror on Hubble is 2.4 metres across, and can produce images of Jupiter (about four times as far from Earth as Earth is from the Sun) of this quality:
![Hubble's New Portrait of Jupiter Hubble's New Portrait of Jupiter](https://substackcdn.com/image/fetch/w_1456,c_limit,f_auto,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2Ff0e9477c-0da1-47c8-8d26-cf91b5b7c0d9_1999x2000.png)
Very pretty, but it can’t really zoom in much more than that. So, if your spaceship has an imaging aperture smaller than 2 metres or so, it couldn’t possibly produce pictures much more detailed than the one above.
Of course, your instrument could be bigger than that and you could get great images, but that also sets the minimum size of your spaceship.
That concludes part 3. In part 4, we’ll explore some ways to avoid pitfalls and perform convincing handwaving.