LinkBack URL
About LinkBacksHello, I have a question that has been bouncing around in my head for a while now. Is it possible to create a vacuum outside of a container? For example, can you use sound waves to push gases away from an object and thereby create a vacuum?
June 24th, 2009, 02:34 PM
Hello, I have a question that has been bouncing around in my head for a while now. Is it possible to create a vacuum outside of a container? For example, can you use sound waves to push gases away from an object and thereby create a vacuum?
In a word no, explosions create a partial vacuum but only briefly
like a white hole?
No, not an explosion. I'm talking about a continuous stream of energy in some form to hold back gases. The idea came for the express purpose of removing air from in front of high speed trains to reduce friction and increase top speed, and maybe acceleration. I'm aware that sound waves would probably not work because it requires air to travel. I say probably because you might be able to have a device that pushes air from the front of the train off to the side just before it reaches the train's surface. Such a system would drastically increase train speed.
The unconfirmed white hole is theorized as a reversal of a black hole, in very simplistic terms a black hole sucks stuff in, a white hole would spit things out.Originally Posted by marcusclayman
So I don't see how that could be something that the original poster is talking about.
as for the original question... I would say a temporary vacuums in noncontainers may be possible, but the one example that was mentioned is a explosion would evacuate a area of air for a time (a brief time). Well thats not totally true, in a explosion air doesn't rush to fuel the fire, oxygen does, so there would (at least I would think) still be nitrogen etc in the air; and even if not as long as there is air pressure it will fill near instantly.
I am interested in the answer to this tho!
the only thing I can think of that would work is magnetic waves, but that would only work on Ions in the air... a majority of the particles would be unaffected.
Arg. I can't remember that name of the technology, but there's something used (or maybe just theorized to be useful) on some jets that sprays plasma or something similar in front of the moving object. If I could remember the name, I'd look up more details, but maybe someone knows what I'm talking about at least... :P
Ignoring the issue of how the technology would actually work, it's important to remember that if your air-removing device is mounted on the train, it probably won't actually reduce the friction. You will basically still be pushing the air out of the way, which will still take energy. The only difference is that now instead of pushing the air out of the way with the front of the train, you're pushing it out of the way with a gadget mounted on the front of the train that projects a field or something. But you will still need to expend energy to make the air move out of the way.
June 25th, 2009, 05:51 PM
Sure. Deep space is a pretty good vacuum, and there is no container.
You cannot use sound waves to create a vacuum, since the existence of sound waves depends on a medium. No medium, no sound.
BTW, explosions do not create a vacuum. Rather they create an intense high pressure wave by generating a lot gas and a lot of heat.
LOOK up fuel air explosive FAE
BTW Jeez do a little rsearch
A fuel air explosive creates a HUGE overpressure, not a vacuum.
You might find a transient low pressure after the initial gas detonation reaction and the gasses cool, but not a very good one by laboratory standards, let alone anything comparable to the vacuum of deep space.
No, you need a container of some form or another
although vaccums are very easy to make, get a soft drink (un-carbonated so not a fizzy one) in a glass bottle, if you smack the top of the bottle with your palm the bottom falls off, this is because pressure generates minute pockets of vaccums at the base
oh and Space is not a vaccum, our very existance proves it, a vaccum is constantly seeking to stop being a vaccum, which is why strong glass containers are used, the larger the vaccum the stronger the force exerted on any stuff inside/around it, (so vaccums that are too big can shatter the container and suck air in, removing the vaccum) our atmosphere, the sun (and probably the earth) wouldn't stand up to a universe sized vaccum, everything would be ripped apart and distributed evenly throughout the universe, As a result space is known as a 'false vaccum' it is apparently empty, but doesn't display all the physical properties of equally empty areas like true vaccums
Edit, oh you can create low air pressure with sub-woofers, that's as close to a vaccum as your average house is likely to get
This notion is simply ridiculous. Of course space is quite a good vacuum, a much harder vacuum than can be manufactured in a laboratory.
Why can space maintain a vacuum despite your assertion to the contrary ? Ever hear of gravity ?
Don't be confused with the nature of the quantum vacuum being more sophisticated than just "nothing". Deep space is still a good vacuum.
First of all, that's not why the bottom breaks, its because of a massive pneumatic pressure you build up that converts to hydrolic pressure when it meets the liquid.
Second, a glass vacuum is LESS of a vacuum than open space. There are less particles in a given volume in Space than in your bottle (i.e. particle density is lower in space than in a lab vacuum.) I've never seen any report of a truly empty "space" ever being observed. I could always be wrong though.
This thread is going from wierd to absurd rapidly.
First of you are not going to generate a vacuum infront of a train by any practical means. Run another train in front of it . its called drafting in the race world.
as for the bottle breaing trick that is due to multiplication of the hydraulic force . You apply a pressure at the neck (small area), since the bottom has a much larger area the force is multiplied by thr ratio of the areas. Its simple hydraulics.
Similar is supercavitation, employed in modern torpedoes. This creates a running air bubble so large the torpedo literally flies in air, underwater. DARPA is working on a submerged military transport vehicle that would move troops at crazy speeds though supercavitation. Good luck with that.
I don't see how we'd apply this to trains, but maybe somebody will.
if you could generate an incredibly large amount of radiation, this could impart its momentum on the gas and create a vacuum... but you will not be able to create the amount of radiation necessary to do such a thing.
It sounds easier to make a vacuum tunnel train. Of course it should be tested on a small scale. A vacuum elevator maybe.
It sounds easier to make a vacuum tunnel train. Of course it should be tested on a small scale. A vacuum elevator maybe.
Edit
Now that I think about it. It would be dumb to get rid of air resistance in a tunnel or elevator, when you can use air as propulsion.
Mostly, and rightly so, people concentrate on trying to reduce drag through aerodynamic means.
There are instances in a design, such as the rear of the vehicle, where instabilities arise and are pretty much unavoidable. In response to this, people in recent years have found designs which channel small amounts of air through the body of the vehicle, and exhaust it out of the back. This does not act as a means of propulsion, instead the air ejection is strategically placed to reduce and delay the instabilities which result from the rear of the vehicle and thus further reduce drag.
This technique is making headway, and if you are interested in manipulating the airflow that envelops the vehicle i suggest that you research this as it is probably as close are you are going to get.
I'm reminded of ears popping when commuter train enters tunnel. It's pushing a tunnel-full of air, in front, and then dragging the same volume behind. Better tunnels are wider, or include pressure relief shafts.
Once a subway train is underway, and ears adjusted to the pressure, would ears pop again from walking down the length of the train?
| « pair creation/annihilation? | plz help to solve problem,not homework just curiosity » |
| Bookmarks |
Bookmarks |
