Leader Bee

You mean something a bit like one of these?

http://en.wikipedia.org/wiki/Mass_driver

Also from wikipedia:

[edit] Spacecraft-based mass drivers

A spacecraft could carry a mass driver as its primary engine. With a suitable source of electrical power (probably a nuclear reactor) the spaceship could then use the mass driver to accelerate pieces of matter of almost any sort, boosting itself in the opposite direction. At the smallest scale of reaction mass, this type of drive is called an ion drive.

No theoretical limit is known for the size, acceleration or muzzle energy of linear motors. However, at higher muzzle velocities, energetic efficiency is inevitably very poor. While linear motors can, with current technology, convert up to about 50% of the electrical energy into kinetic energy of the projectile, the energy of interest is the kinetic energy of the vehicle, and as the muzzle velocity increases, this is a smaller and smaller percentage of the generated power.[citation needed]

Since kinetic energy of the projectile is ½mv², the energy requirements vary with the square of the specific impulse, so in a design one must choose a tradeoff between energy consumption and consumption of reaction mass. In addition, since momentum of a particle of mass m has momentum mv- proportional to velocity, but energy is a square law, so the average thrust for a given energy is inversely proportional to the velocity of the particles. In other words, heavier projectile masses give lower specific impulse but proportionately higher thrust. (See propulsive efficiency for more details).[citation needed]

Since a mass driver could use any type of mass for reaction mass to move the spacecraft, this, or some variation, seems ideal for deep-space vehicles that scavenge reaction mass from found resources.

One possible drawback of the mass driver is that it has the potential to send solid reaction mass travelling at dangerously high relative speeds into useful orbits and traffic lanes. To overcome this problem, most schemes plan to throw finely-divided dust. Alternately, liquid oxygen could be used as reaction mass, which upon release would boil down to its molecular state. Propelling the reaction mass to solar escape velocity is another way to ensure that it will not remain a hazard.

Space is almost completely empty, so propellant sources are only to be found at asteroids, comets, moons and planets.

By that logic does it mean that Earth will not continue in its orbit and will eventually fall into the sun? (provided we assume the sun will remain a main sequence star and not expand)

I understand that in science you try to find answers that make sense to questions about the world around us. So far science has answered almost every question except those classified as "Supernatural."

How do we make interstellar travel possible?

Can we create a time travel device?

Can we bring the dinosaurs back to life?

Along with many many other questions, scientists have all sorts of things they have yet to discover and perfect. "Perfect" being the important word here as scientific discoveries are rarely eureka moments where you have nothing then suddenly you have all the answers, research is incrimental.

Basically, answering questions about how the universe works just isn't easy and if you don't hear of any groundbreaking developments for some time it isn't because there are none left to answer, it's more likely that they're too busy running experiments & researching the subject so they can produce one.

Great topic, but I have to digress. I remembered reading about an artificial gill that was like a box with membrane wrapped around it to allow oxygen to flow into the chamber containing the human. So the real advantage was that humans would not need sophisticated diving equipment to stay underwater but could meet their oxygen needs from the surrounding water. I found it fascinating that the guy who was interested in this equipment put his dog at the bottom of his pond in such a device - and it survived happily - if a bit bemused.

 

I thought I would never find a scientific paper actually reflecting this story yet here we are:

 

 

Link to article

I believe i've seen a documentary on this before, the designer had plans for it to supply oxygen to a marine lab somewhere on the coast.

I've found a link to this companies website explaining the technology: http://likeafish.biz/

OK it's a dumb question... because they have gills!

But aren't those gills just extracting oxygen from the water already? I would have personally thought that even though water may be more oxygen rich (being hydrogen and 2 oxygen atoms after all) that air would have been easier to extract the oxygen from as it's already freely floating around and therfore no need to seperate the 02 from something

I'm no biology expert so I thought i'd better ask this burning question on SFN before I forgot I was curious about it.

I'm sure breathing pure oxygen, at least for extended periods of time is actualy bad for you...

Quick and simple:

Is the hubble constant the rate at which galaxies are moving away from us or the rate of "cosmic expansion" and the speed at which the distance of space increases between us?

 

Let's say object A was travelling at 1m/s and Object B was travelling at 1m/s. They collided after that object A travelled at -1m/s. So the change of momentum of object A is -1-1= -2 .

How can an object move at a speed less than nothing?

I believe they should be told for medical reasons.

Yes there is an argument for moral reasons where they would have the possibility of feeling ostricised from the family but to me this is insignificant if the family treats them no differently.

If the adopted were to fall ill, and say requires a bone marrow transplant or similar then the likelyhood of a family member being a donor is incredibly slim and they'd likley find out then.

Better to tell them at a young age so that if anything does crop up they will know where they stand.

I play a lot of online games and I generally tend to need to select a unique name. I thought this one sounded quite cool and is ALWAYS available.

Now I use this name everywhere for consistency reasons.

Yes, with no knowledge of what is going on outside it would appear as though the gun has a standard muzzle velocity WRT the trains occupants; If there was another reference frame where people outside the train could see inside the muzzle velocity would be Muzzle velocity + Train speed.

Merged post follows:

But as the bullet moves in one direction, then the person is moving in the opposite direction.So to the velocity of the bullet as seen by the person is the velocity of the bullet+the velocity of the train, right?

No, this is incorrect because the bullet is still moving, as with our elevator and football scenario, relative to the stationary gun up until the point it is fired ( not being a physics bod it probably still is moving relative to the gun once fired but I cant explain the reason ) therefore the inertia of the bullet(correct?) is moving towards the shooter and this would appear to have a negative effect in velocity on the projectile with respect to the person firing the bullet -- I think.

My understanding is that because they share the same (Or very similar) reference frame they act just as they would in any other situation.

Isn't this thought experiment similar to the one where you fire a bullet inside a perfectly stable train with no windows or knowledge of the outside world it will move just as fast as you would expect when firing it in a normal situation on the ground rather than expecting it to travel at the bullets muzzle velocity plus the speed of the train?

I am aware you can purchase glycerin easily but for the purpose of curiosity I was wondering if it is at all possible to refine what is already in a multitude of everyday products into a usable volume, in this case from cough mixture.

There is no application I have in mind for it, just merely asking to see if it is possible??

By the time we need to escape the expansion of the sun do you not think we would have already colonised other bodies in the solar system? It seems far more likely than actually moving an entire planet from it's regular orbit.

 

if time is a medium, how come that we cannot go in every directions in this medium?

 

Because I hypothesised that time only exists in the current reference frame (it is a one dimensional point). There is no past other than what man has recorded of it, there is no future because it has not yet happened and could happen in a great many ways hence there is no direction with which to travel, only the current point in time in which you exist.

I think people need to untangle the concept of past and future as "places" that can be visited and look at them as concepts man has constructed to make recording events easier to explain.

I think time is indeed a manmade concept and there are two seperate definitions (That i've come up with myself admittedly)

1) Actual/Fundemental Time - which is the here and now, the present in which all things happen and that time does not exist outside of the present.

2) Perceived time, which is our measurement of 1 second per second. Clocks are a device that measure time but they do not require a force called time to function; They are pre-set to record what we think the passage of time should be and not outputting what time really is.

Time does not push us along, it does not move, it is only a medium which allows us to interact with the universe. Without time interaction is not possible.

Our concept of percieved time is only an idea and not a force that affects the world, it is our concept thought up to make the recording of events in Fundemental time easy, a reference frame that we can all relate to, a co-ordinate of an event for example.

IIRC the 38 mph is right, but the rest is varying degrees of wrong. Laser cooling reduced the temperature of the atomic vapor; the light was slowed because there was a sharp transition nearby which caused a rapid change in the refractive index and group velocity depends on the slope.

Didn't we conclude in this thread that photons always travel at C?

http://www.scienceforums.net/forum/showthread.php?t=51142

How is it possible to slow down?

Edit: sorry, just sat and re read your last post and realise it is due to photons taking a longer path.

I believe there is a thread somewhere on the board where somone has electronic copies of hundreds of textbooks.

Other than that I guess I can't help, sorry.

I'd go with the Tungsten mesh please, not only does it remove makeup, grease and stubborn stains it will also remove the top layer of your face.

"Tungsten mesh, have you tried it wet yet?"

Without a multispectral education system though it would probably limit the amount of industries a country could produce employees for. Say out of 100% of a population 70% want to go into animal care, another 20% wants to go into scientific research/engineering applications and the last 10% wants to do something like financial services then the economy for the country is going to be severely compromised when they don't have the individuals to competently work in those fields.

It might mean contracting those jobs out to foreign workers but you can see that people will want to learn all the "nice" subjects like arts, film & television, music etc ( some will have an inherant interest in other subjects) but as a child you don't realise how that could be detrimental and an education system that focuses on the wants of a nation might be setting future generations up for a messed up economy - if nobody wanted to get into the health system then we'd be desperately messed up for example.

After a certain level of education -possibly a year or two into secondary school, when more advanced subjects have been taught and the student has had time to get a feel or not for whether it will interest them, then the student should be given the chance to either drop or continue in a subject.

Until that point, all subjects should be compulsary.

once the above is met I believe the student should be given the opportunity to focus on the subjects which they enjoy and excel at.

Learning maths when you have proved for years that you are no good at it and certainly don't enjoy it certainly seems like a waste of time when say the student enjoys and actually does well in areas like geography or science, dropping other subjects will give more time and focus to the subjects someone might actually be good at.

Certainly there will be individuals who will take advantage of this system only to get "a free period" and this should be monitored carefully.

A system like that would benefit some more than others, while for the ones who take advantage it would only be detrimental. The ones who actually want to learn it would allow them to excel in their chosen subject instead of wasting time with whatever their brain just doesn't comprehend.

I really wish this thing had been built because it seems so "alternate dimension Command & Conquer Red alert" cool.

It just seems incredibly impractical at the same time - Considering plans were drawn up to build one, would it have actually been possible to make it move if it ever had seen the light of day?

http://en.wikipedia.org/wiki/Landkreuzer_P._1000_Ratte

it originally came about when playing a space based MMORPG had an influence on it.

EVE Online by any chance?

I'd go with something relatively boring and common, you would certainly have a lot less problems during your school years. Maybe Dave, John, Joe or somethign like that.

I guess Sven isn't as much of a problem now i'm in the working world but every now and then you get some idiot who has to make a remark about it or just plain gets it wrong no-matter how many times you repeat it.

I'm so used to being called it now that I couldn't imagine it changing.