Underwater power cables affects crabs biology at a cellular level
hw.ac.uk
hw.ac.uk
For reference, this is the magnitude of Earth's magnetic field.
What's the strength of magnetic fields around undersea cables?
https://www.mdpi.com/2077-1312/9/7/776/htm#B15-jmse-09-00776
From the paper: >EMF strengths predicted around subsea power cables, as reported in the literature, vary from 140–8000 µT [15,17,18]. A commonly utilised cable operating at 1600 A is expected to produce an EMF of 3200 µT in a perfect wire, at the cable surface [17]. As with all EMF, the values will decrease with distance from the source, resulting in a field strength of 320 µT and 110 µT at 1 m and 4 m respectively [17].
15: https://dspace.lib.cranfield.ac.uk/bitstream/handle/1826/778...
426 pages sheesh. Page 25 (37 in the pdf) discusses the magnetic field strength model. No math but references. I'm getting more nervous because the references are all related to modeling power lines in air.
Table B-1 shows a list of submarine power lines and Table B-2 contains their simulated magnetic field strengths.
Medium does affect magnetic field geometry. It'd be nice if someone took some actual measurements if they're not going to use a decent model.
So much effort has been spent studying the effects but presumably no one has actually checked the magnitude of the magnetic fields around submarine power lines.
I'm no expert though, only have some high level undergraduate fields and waves course work.
Maybe that's a reasonable assumption, but is it? It at least warrants discussion in one of these papers.
All I expect is a "yes we thought about it" in the form of measurements of ocean floor salt water magnetic permeability.
If the models prove too much they could always drop a magnetometer off a boat.
By that measure, an eighty-times stronger argument against the researchers' due diligence would be "how do they know the cable isn't actually carrying 1599 amps? Did they measure the current?"
https://www.revk.uk/2017/12/its-official-adsl-works-over-wet...
Two thoughts come to mind.
More cables in parallel carrying less current, which gives the added advantage of redundancy.
Short breaks in the flow, like a railway crossing for crabs, for 5 minutes or however it takes them to get unstuck and go along their crabby business.
AC loses due to reactive impedance and skin effect should always be higher than DC transmission. DC might make sense if the generation is solar based, as it naturally generates DC, although converting it to higher voltages must have an AC step.
I think it's only efficient for the largest capacity lines tho
If I remember correctly that actually makes things much worse if you've operated at one potential for a considerable amount of time.
You could operate the cable at AC ~ 0.1Hz but your ability to actually transmit MWH would suck.
Whatever, the ground currents penetrate very deep into the earths crust thus equally effecting buried cables.
Its the difference between just shifting the frequency or phase on your local control clock at the substation, and trying to coordinate with another state/territory/nation's entire AC generation infrastructure to keep everything in phase.
Every time we have a problem with tech the answer always is "just add more", idk how to feel about that
Another example: Microcontrollers that have loads of pins (e.g. 100) and support many different peripherals (i.e. protocols like I2C) are expensive (say, $10-20). Little ones with a medium amount of pins (e.g. 56) and support for limitless protocols are cheap ($1). So if your PCB needs just a few more GPIO pins to accomplish something it makes more economic sense to just "add another" little MCU rather than "go big". Even if it makes programming the thing slightly more complicated.
I understand we can actually run DC at higher voltages than AC, though I'm not enough of an EE to explain why. IF this is true, then DC losses would be less than AC.
It's interesting because the reasons why we built everything using AC in the past don't really apply anymore (well, most of the time). DC is more efficient for most domestic and industrial electricity utilization. Things like lighting, air conditioning/heating, refrigerators, etc are all more efficient if fed from DC. Think about it: How many "wall warts" have we got in our homes these days? All our LED light bulbs have built-in inverters and that decreases their efficiency. Our PCs use DC for literally everything internally. The list goes on and on.
I had also read a while back that grid-scale DC power transmission could be more resilient because the power transformers aren't as expensive. It's like $8 million for one of those giant high voltage AC transformers they have at power stations whereas with high voltage DC the equipment is cheaper but you have more of it (or something like that; I wish I could remember the details but this was an explanation given to me from a DC fanboy lineman over 10 years ago). The idea being: If bad weather breaks your giant $8 million AC transformer that's a real expensive pain in the ass but if it breaks a handful of small DC transformer components that's a quick (and cheap) fix.
Think you meant rectifiers here.
Perhaps you learned it differently, but according to any source I can find, they're defined as I said.
Rectifier: AC -> DC
Edit: whoops I'm late to the party
More complicated bulbs use an active rectifier / switching power supply instead.
There's also the electrolytic-smoothed bridge rectifier variant. BigClive has a lot of teardowns of such light bulbs (and non-bulb-shaped alternatives) with circuit diagrams and explanations. They're really good for learning about the various "cheap LED bulb" designs.
And yeah, a DC grid needs active converters at connections points anyways, and the small voltage changes needed for steering power flow across redundant paths is also relatively cheap.
A big issue is just that a constant-power SMPS with an input voltage range/tolerance inherently offers a negative differential (aka incremental) resistance: within the supported input voltage range, reducing the input voltage causes the current consumption to increase inverse-proportionally (typically even a tiny bit worse because internal losses in the SMPS increase with current, requiring even more current to make up for the slight drop in efficiency (think 98% to 97%, for a sense of scale)).
In AC grids phase is comparatively easy to stabilize, and constant-power loads already need PFC that (for single-phase rectifiers) has to emulate a normal resistor who's resistance slowly drifts to accommodate changes in output power consumption. The only real issue is that this method requires an intermediate stage with large capacitors to feed the output stage while the input stage stops feeding near the zero crossing (the capacitors get smaller if you do away with the zero crossing (DC grid using the emulated resistance for stabilizing the grid), but the stages remain, along with their ~1% inefficiency per stage).
The main issue with LEDs is that you need electrolytic capacitors to buffer the zero crossing of single-phase AC, and electrolytic capacitors dry out/corrode when operated at high temperatures. So unless you want the LED PSU to have a fan, those capacitors will severely affect how tightly integrated you can build a non-low-power LED light bulb.
And yeah, especially at a local scale DC grids are very useful, because you can skip expensive inverters and conversion losses for both battery(-backup) sources and solar panels/fuel cells. You would typically still want an MPPT for a string of solar cells, but that's a compact and rather inexpensive DC/DC converter. Batteries only need a way to accurately limit the charge voltage/current per-pack, to prevent the voltage drop along the grid cables from affecting the maximum charge voltage/state of the pack's cells. Also a deep-discharge protection, but beyond those, a (mostly) solar-fed local DC grid can just let the MPPTs feed as much as they can up to a target voltage, from where they start to gradually throttle output current to only produce as much as is being used (once the batteries are full). If the batteries start to reach sufficiently low charge state, load shedding or alternative power has to be used (say, via telling PCs to reduce/disable Turbo Boost and similar, or lights/screens to limit brightness).
>Dr Alastair Lyndon, from Heriot-Watt University, said: “Underwater cables emit an electromagnetic field. When it’s at a strength of 500 microTeslas and above, which is about five percent of the strength of a fridge door magnet, the crabs seem to be attracted to it and just sit still.
>“That’s not a problem in itself. But if they’re not moving they’re not foraging for food or seeking a mate.
>“The change in activity levels also leads to changes in sugar metabolism - they store more sugar and produce less lactate, just like humans.”
There's a comment above in which some guy observes that the strength of the EM field emitted by these cables is similar in strength to the Earth's EM field.
The article also mentions that these crabs migrate. Presumably they migrate using some organ that is sensitive to the earth's magnetic pull.
We know what happens when moths--who use light to navigate--encounter artificial lights. Their navigation hardware can't handle it, and they end up circling the light. This seems like the same kind of thing.
https://www.sciencealert.com/birds-see-magnetic-fields-crypt...
One last random association "I want to see Gamma Rays!" https://youtu.be/mPnx3zO3SDc?t=70
Sounds like someone has just discovered a way to farm tastier brown crabs.
As far as I'm aware, nearly all modern high capacity cables are built this way already.
It's only old stuff (which tries to use the earth as a conductor) or low capacity stuff (which is sometimes AC and not well balanced) where this isn't true.
This makes all electrical fields zero... but in the ocean there may be other natural electrical fields that don't appreciate being zeroed out...
But it's not visible to the surface directly.
https://www.jstor.org/stable/25085325
> Ants are strongly attracted to both AC and DC electric fields (Fig. 2). The numbers that accumulated increased with an increase in the voltage for both DC and AC voltages, and for all species. Some species (P. comanche, Ph. hyatti) show little or no response to voltages lower than 50 volts. Other species showed slight responses to lower voltages, although the response greatly increased at voltages above 60 volts. No difference in ants' responses was detected between AC and DC generated fields (Fig. 2), although ants leave AC powered points at a slower rate due to a possible residual effect of AC (MacKay et al., 1989). Ants of all three subfamilies responded in a similar manner.
I am not saying there isn't any link but I am saying that 'volt' is surely the wrong connection, so this should be taken with utmost caution.
The unit of electric field strength is V/m. They put ants inside a test apparatus, so the "per meter" part is fixed (by its design) and the voltage is experimentally manipulated. They do use the right units elsewhere in the paper.
I imagine this was done to avoid measuring the electric field in the electrode/air/floor/ant medium, which is not exactly homogeneous.
Regardless, at a more practical level, sea creatures can't wear hats, tinfoil or otherwise.
The thing is, there is no scientifically validated evidence of that effect; also, there is no proof of humans being able to sense (electro-)magnetic fields.
Besides, for science you need to provide evidence for an affect to prove it exists.
For people you need to provide the “negative” of evidence to prove it doesn’t exist. People and science are not the same.
Heat and nerve stimulation is also possible according to https://en.m.wikipedia.org/wiki/Safety_of_magnetic_resonance...
The effect is widely used.
https://en.wikipedia.org/wiki/Transcranial_magnetic_stimulat...
You can if you implant magnets in your fingertips. Not joking.
That said, this report / study does show evidence of electro magnetic influence on living organisms. So perhaps it's worth asking "Have we missed something in humans?" That's a legit question, especially in the context of science.
Thankfully that prediction can be verified easily before we jump to solutions such as burying underwater power cables.
Which is great, as such a falsifiable prediction is a welcome part of a scientific paper.
Maybe we just need more point of load solar.
TFA doesn't mention copper at all, the high-tension wires running above my street are composed of stranded tubes of aluminum.
Yeah sounds like a Darwinian problem to me.
This should be treated with utmost caution without statistical and physical proof.
It's not at all physically implausible that crabs sense some electric or magnetic character in the surrounding water through their antennae or some other organ. Electroreception is known in bees, why not crabs? This could easily be the first evidence of that.
I'm replying, no, there's nothing dubious about it. Which doesn't mean it's accurate. Biology has always prominently featured observation from life, and this is, in general, how the field first starts to suspect that, say, bees can sense electric fields.
Experiments on crabs might and should follow, but your skepticism isn't grounded in anything here.
Yes, exactly, because at least counting the crabs and comparing the count with other clusters of crabs would show whether there 'is something'. Missing accuracy is not my problem, it's missing 'there is something' vs. 'there is nothing'. Without any statistical data, there is nothing to talk about, not in biology either, which is also science.
Skepticism is very important. I challenge them to count crabs on cables and compare with crab counts not on cables, and then make a case. That's all.
This is the follow-up experiment.
https://www.mdpi.com/2077-1312/9/7/776
As usual with modern science journalism, it's necessary to click through and read the actual research paper. Otherwise, one will be totally lost.
As for samatman's concerns, the paper uses standard experimental controls and statistical analysis, as expected.
Transcranial magnetic stimulation uses pulsed magnetic fields produced by a strong electromagnet. It's currently an FDA-approved treatment for depression and a pretty common research tool. The fact that it has (some) biological effect is pretty clear: aim it at motor cortex and you can make someone's finger (leg, etc) twitch!
Transcranial electrical stimulation (tES) is a family of techniques that apply weak electric current to the scalp to affect brain activity. These include tDCS (with Direct Current) and tACS (Alternating Current). While their effectiveness has been debated, my group has collected data demonstrating robust effects on the activity of neurons, even deep in the brain. Check out Figure 1 of this paper: https://www.pnas.org/doi/10.1073/pnas.1815958116 It's not always that simple, and it interacts in complicated ways with ongoing brain activity, but it does do something too.
You can get much strong effects if the electrodes are inserted directly into the brain (or muscle) too but it's not all the case that EMFs are biologically "inert".
They're not magnetically active, but moving conductors in a magnetic field produce current, so it's not wildly implausible. Indeed, if you were a crab getting unexpectedly stimulated, sitting still would be one way to make it stop!
So it is clear that changes in the magnetic field inducing voltages cannot be the mechanism of action in this case.
Weaker stimulation can't do that, but subthreshold stimulation can "nudge" the timing of spikes. In a living brain, neurons are constantly bombarded with synaptic input, and therefore sit closer to spike threshold and occasionally spike. Weak stimulation can therefore cause them to fire a bit sooner or later than they otherwise would. Since information is carried not just by the overall amount of firing, but also the spatiotemporal structure of that activity, these subthreshold changes can lead to overt changes in behavior. The recurrent nature of the brain can also amplify these effects.
I know this because I've literally measured it in macaques and found that fields well below 1 V/m (produced by ±2 mA 5-40 Hz AC on the scalp) are enough to reorganize spike trains. Here's one of our papers: http://packlab.mcgill.ca/Krause%20et%20al%202019.pdf
FWIW, I was surprised by these results--and deeply relieved when they replicated!
Cool paper and impressive but the direct contact, part of the circuit, tES results don't translate to this context. The induced voltages (for the power cable) would be so far below the noise floor that not even arguments for stochastic resonance boosting above threshold make sense.