When a person experiences acceleration in an everyday object, such as a car, the actual “perception of acceleration” is being pushed in the direction of the acceleration by something, such as the car seat. However, the car seat itself is only in contact with your back. The force must be transmitted through your body (by electromagnetic forces on the molecular level).
Pilots can undergo a small number of g’s like this before blacking out. What if the accelerating force was transmitted to your entire body at once or, at least, to a greater area? Wouldn’t the stress felt be reduced, leading to a reduction in “perceived acceleration”?
A charged object in an electric field experiences a uniform force throughout if the field has a negligible gradient. What if a person wore a charged suit? Could an electric field be set up in a vehicle to negate the perception of acceleration as we are used to it? Could charged implants be used to improve the effect?
If the idea is sound, has it been tried, and what sort of accelerations could be undergone comfortably this way? And would such a field be biologically safe?
I seem to remember a mention of this concept in a sci-fi story where every molecule in your body was accelerated equally by some force rather than having a mechanical force push on your back while the rest of your body squashes under the pressure. Therefore you experienced no feeling of acceleration. But I think it’s still pure sci fi, AFAIK.
No, this wouldn’t work at all. Instead of being pressed against by your seat, you would be pressed agains by the electric field. The feeling of acceleration is in the sense of pressure on your body only. But the effects of acceleration act throughout your body.
Spreading force out over a larger area is a tried and tested method for reducing stress at a given point. This is how snowshoes work for instance (you are being accelerated down by gravity…the snowshoe spreads the force over a greater area so you don’t sink in the snow).
Remeber the energy of the equation is always the same. Do a push-up on one finger, five fingers, ten fingers and your entire hand. You always weigh the same but that weight on one finger might break it while spread across your entire hand is no problem.
In any case where you wish to reduce damage spreading the forces experienced over a larger area is useful. Still, the human body is only capable of so much. If you don’t care about moving and just want to resist acceleration than 9-12 positive G’s are all we’re good for before blacking out (or 3-4 negative G’s before a redout). Part of what determines all of this is how long the force is applied. A constant 9 G’s or 20 G’s for a split second?
Here’s a link about ejection seats that illustrates the problem:
Most military pilots, especially fighter pilots, wear what is called a “G” suit. Basically, the reason you black out from too many G’s is because the blood flow to the brain becomes limited by the apparent gravitational forces. The heart cannot pump efficiently against force of 4 or 5 Gs and thus the brain loses its oxygen supply.
A G-suit is designed to apply pressure in strategic areas of the body to force your blood to circulate properly. Pilots under high G stresses also use an exercise I can only describe as a massive grunt accompanied by tensing all of the lower body and abdominal muscles, somewhat akin to what happens when you’re trying really hard to take a dump (sorry for the graphic image). Anyway, this combined with the G suit usually allow a pilot to remain conscious in the 6-7 G range as opposed to blacking out in the 4-5 G range without. (I think those numbers are right, but I could be mistaken).
To address the OP directly, I doubt that an electrical field would be of use in such a situation. While techically it may be accurate to say that forces are transmitted by electric fields at the microscopic level, physicists rarely use that description. I’ll allow someone better versed in physics to help with the why of that.
Star Trek is one sci-fi source of this idea although there may well be others. In Star Trek they call them Inertial Dampeners and as they work in Star Trek expect to probably never see one actually work (along with transporters).
You haven’t convinced me yet. For instance, when in free-fall, you are being accelerated by a near uniform gravitational field, yet you do not feel the press of acceleration as in a car. The feeling of acceleration is due to a pressure being distributed through tissue. Reduce the pressure by increasing the surface area the force acts over and the feeling should decrease.
Whack-a-Mole:
I’m looking to reduce pressure, not force. But your Star Trek argument’s good
El Marko:
Sorry I didn’t make it clear that I was not relating electromagnetic forces on a molecular level and the electric field I was suggesting. I realise the scales are highly different and that the magnitude required could be dangerous, hence my further question about biological implications.
To cut down on acceleration effects,
why not fill the spaceship with an oxygen- bearing liquid? Hydraulic effects will mean that the pressure of acceleration is distributed more gently.
Stand on my size 6.5 feet, my ears feel 9.8m/s/s. Lay on my back in a water bed, my ears still feel 9.8m/s/s. Step on a nail, my ears feel 9.8m/s/s, my foot feels much pain. You’re talking about two different things. Pressure is force per area. The sensation of gravity has nothing to do with pressure, only accleration. Put me in outer space, put me in a big cosmic vice, I’ll feel lots of pressure, no acceleration.
In free fall, you don’t feel your self accelerating because each little part of your body is accelerating on it’s own, just like in the Sci-Phy show.
If you are moving and put your finger out against a wall then the entire force of your body mass will focus on the tip of your finger to stop you (there’s some pressure). Given the small surface area of your finger vs. your entire mass it won’t take much to crush your finger…eventually your entire body will smack against teh wall and it will do a much better job at stopping you.
I think what it is that you’d like to see is something that would apply a force to me back, front and everything in-between simultaneously. Neat idea and fantastic if it would work but what you are suggesting is the Inertial Dampeners from Star Trek and that is a falt-out non-starter. I seriously doubt it is even possible but even if it were it is certainly WAY beyond or current technology to effect.
I suspect much of the problem with your theoretical field is distance. You don’t feel a repulsive force from the chair you are sitting on till you touch it. We’re talking atomic scale distances that change how you feel force. To apply a force throughout your entire body…front to back…is today unthinkable.
Pressure is force per unit area. You can reduce pressure by increasing area while maintaining the same force.
As for the actual field itself, I don’t think distance or magnitude is a problem. To compare it with something a bit more intuitive, it’s quite possible to make a magnet attract metal with a force strong enough to affect a person from a distance of a metre or so, and this application requires less distance than that. The electric and magnetic forces that we can generate are of the same order or magnitude as their physics is closely related.
Note: My idea could not be performed with a magnetic field as it requires a monopole, and magnetic monopoles do not appear to exist. Electric monopoles are fine though.
Billy:
Yup. That’s pretty much my point. Pressure and gravity are very different things. Pressure is a force acting on a surface. Gravity is an inverse square field acting on mass to produce a force. A point charge produces an inverse square electric field. Two parallel charged plates attracting each other produce a constant field. Non-parallel charged plates have a more complex field, but I would expect near constancy could be engineered. The field will act on any charge in the volume it affects.
Though I am suggesting using charged surfaces for the field to act upon, there is no restriction to how much surface area can be fitted inside a volume and, in the limit, it is infinite. If a body as a whole is charged, it’s whole volume experiences the same electric force and there is no pressure gradient to be dispersed internally.
eburacum45:
Using liquid to buffer acceleration is another way of dispersing a pressure gradient more effectively. I expect the fluid would disperse the pressure acting on its boundary as a force acting on the whole more efficiently throughout it than a human body as it would be more or less incompressible.
Let’s say you’ve got a charged suit, and there’s a charged panel in front of you that attracts the suit. The attraction between the suit and the panel exactly offsets the acceleration of the ship.
All this does is relieve the pressure of your body weight on the seat you’re sitting in. You still feel the force. The only difference is that it comes directly from the back of your suit, rather than from the seat into your suit into you.
You could achieve exactly the same result by attatching ropes to the front of your suit, and tying the ropes to the front of the ship.
If you wanted to go all out, instead of attaching the ropes to your suit, you could surgically attach them to your skeleton, which would give the same effect as the “charged implants” idea.
As you have described the situation, I agree with you. Only the back of the suit would be in contact with your body on acceleration. The area the force is acting over would be the same.
However, what if the front of the suit is also attached to your body and rigid? The forward accelerating force would act all across your body’s surface. Nevertheless, you would still black out eventually.
The insides of your body would still be displaced backwards relative to their normal positions, even though your skin would maintain its shape. I would expect you to last longer as the actual shape of your body would be maintaine rather than the whole lot being crushed. Your front would not be deformed as much.
But can I move away from that now and start with a simpler situation before building the argument up again. I was trying to suggest scientifically plausible ideas before, but the following is just to help the explanation:
Imagine, hypothetically, that your body is uniformly charged throughout - no suit is required. An electric field is again applied to offset the accleration of the vehicle.
Is it not true that the contents of your body remain stationary with respect to each other - you accelerate as one particle? In that case, wouldn’t there be no reason to black out?
Also, isn’t that case the limit of adding more and more charged implants inside your body? If so, does it not follow logically that some implants would have a partial effect?
You’d be better off with the skeletal attachment thingy.
There are still problems here.
The skull, for example, is rigid. The front and back won’t compress toward each other very much. The contents of the skull will. How to overcome that? One way might be to put a “bone foam” inside the skull to minimise relative movement. Another way is as you suggest, to charge the brain. Either one will thouroughly disrupt brain function.
Lovely! So are we in agreement that the problems with this are biological rather than physical?
What I was trying to establish initially is that the physics of the idea were sound. My biological knowledge probably isn’t adequate to contribute much further, but I’d be interested to hear what biologists have to say.
E.g.
What acceleration can the brain withstand by itself?
Has there been any research into the behaviour of existing implants (such as artificial joints) in magnetic fields (to get an idea of the body’s response to similar forces)?
Has there been any research into charged implants?
As eburacum45 said, and as has previously been suggested in our household, perhaps the best solution would be to have a vat of water (or more ideally a fluid that matches the density of the human body) in which the pilot or passenger is submerged. In my head I envision a pilot wearing an oxygen mask, etc, but would the pilot require guides to keep him/her suspended in the liquid? What would the effect be if the pilot were standing on the bottom of the vat, surrounded by liquid, and the vat were accelerated upward? How much water/fluid would be required to achieve the desired effect? Would special equipment be required, or can we start outfitting our fighters right now?
Well, there is a way to impart a force distributed equally over all parts of your body – it’s called gravity.
If you had some technology that could shape gravitational fields any way you wanted (which is not possible in our current understanding of physics), then you could accelerate someone by creating a gravity field to pull them forward. All they would feel would be a falling sensation.
The problem with adding an electrical charge to an object is that all the charges would repel each other as well as be attracted to the opposite charge you’re using to tow the object. So the object would tend to tear itself apart as well as be towed.
