Whoa: The real Prometheus

[_Owen_]

Actually they have been considering a elevator. In theory it is not a difficult concept, and it would provide many options as well as more generalized space travel, more public space travel...

Owen Macri

[Avatar28]

Oh, I'm all ABOUT a space elevator. LOL. If I had the money, I'd build one myself. The amazing thing is that it could probably be done for only a few billion dollars, bureaucracy and red tape notwithstanding (I expect that would increase the cost substantially). Basically, you only need to launch enough materials to build a very small strand down to the surface. Once there, the filament can be expanded on to bring it to it's full size and strength.

And, yes, it would allow public access to space eventually, once more cables are strung to allow more simultaneous up/down trips, it should become much easier.

Your main building costs are just land and materials (and the initial launch of 20 tons to geosync orbit).

[_Owen_]

Yes, and the, I guess you could call it a space anchor, would need to be in such an orbit around the Earth so that the pull of the anchor away from the Earth is equal or greater to/than the force that will be pulling against it. The only problem is the location of this elevator would need to be carfully sighted out because no planes or arial vehicles would be permitted in the area. As well the orbit would have to calculated properly so that it would not accidentally hit any satelites, etc.

Technically the space elevator is a logical idea with our current technology, I would definetly make one if I had the money, who knows maybe someday I will...

Owen Macri

[Avatar28]

It would have to be located on the equator somewhere. A.C. Clarke propsed Sri Lanka in Foundations of Paradise. Other than that, any location right on the equator would be good, but something in the middle of the ocean would be ideal since you'd have less air traffic to contend with. Impacts by space junk in LEO would be the real threat though anyways.

[_Owen_]

I would have thought maybe a large desert, you wouldn't get much air traffic there, but where would here be a plausible location? I agree, get rid of the space junk, maybe they could put some weapons on it, nothing big just enough to blow up and nasty little rocks. lol.

Owen Macri

[Avatar28]

Problem with that is that you end up with lots of little junk which can be just as bad and is a LOT harder to clean up. At least the bigger stuff can be more easily deorbited. Nukes are no go because of the EMP effect would do a LOT of damage.

[_Owen_]

I guess that is true, how about some type of overload laser to melt the space junk? Then you would pretty much get rid of it.

Owen Macri

[Avatar28]

Hmm, maybe but high powered lasers aren't exactly common or efficient right now. And you still have to find it. Also the laser would still be more likely to cause it to explode or burn a hole through it than to melt the whole thing. Some of the really big stuff could possibly be collected and brought back down or even simply deorbited to burn up in the atmosphere. That's what they typically do with old satellites. Most stuff in LEO will do that anyways without periodic boosts due to atmospheric drag. That's why the space station has to be pushed back up every so often. Also most middle to larger sized stuff can be tracked by radar and possibly collected or diverted. It's the smaller stuff that will cause the problems.

[cobraR478]

There is no weight in space other than the very small amount when you are within a gravitational field, but it is only a miniscule amount of wieght. So weight would not matter in space either.

Owen Macri

Its not the weight he is actually talking about, its the mass. A rocket wold not propell the Earth, or the moon, as much as it would propell a pen.

[_Owen_]

The reason that I rocket would not propel the Earth or the moon is because they are strongly effected by other gravitational fields.

The only thing that will counteract momentum is gravity and friction, a ship is space would not be largley effected by any gravitational field unless in an orbit, and there is no constant friction in space except for contact with another spatial body.

If the Earth was placed somewhere so it would be uneffected largley by a gravitational field like in a void between galaxies, then a rocket would propel the Earth and the moon and a pen, the same distance.

Owen Macri

[Avatar28]

Sorry, Owen. That's where you're wrong. The more massive an object is, the more force it takes to move it. It has nothing to do with it being in a gravitational field. Also, even if an object were in the void between galaxies, it would still be affected by the gravity of said galaxies.

What counteracts momentum is a FORCE. And that's what thrust is, a force. The more massive it is, the more force it take to overcome it's inertia and effect a change. Say you've got two weights. One is 1 lb and one is 2 lbs. If you apply the same impulse to both objects (meaning each received the same amount of energy), the 1 lb object will be end up moving twice as fast as the 2 lb object due to conservation of momentum.

[_Owen_]

The reason that you are using this line of thinking is because you are using examples from Earth, correct me if this is incorrect and you are thinking diffrently.

The reason that two objects on Earth of diffrent size could not be propeld equal distance is because:

1) The mass of object one is larger than the mass of object two, so it will be pulled towards Earths' surface faster because it is heavier.

2) The greater the mass of the object the more friction is acting on it, friction from the air around it.

For the sake of argument let's say for example that the two objects are cubes, simply to not make things more complicated than they need to be by brining in aerodynamics as well.

On Earth the cubes will be propeled diffrent distances when the same amount of force is applied, however in space when not in a significant orbit around another spatial body the two objects will be propeled the same distance at the same speed.

The factor of gravity would not be working significantly on the objects, and the factor of the constant friction of air on the objects would not be acting on the experiment at all.

In space not orbiting a spatial body or being attracted at a siginificant rate by a spatial body, the objects will be virtually wieghtless, not completly, but very close.

Two cubes of diffrent sizes fired from the same position in space where friction and gravity are not forces that are significantly working on them would travel the same distance at the same speed when proppeld by the same force.

I agree with you, mass does have an impact on the amount of force required and the distance the object will travel but mass only has a large impact when it is being effected significantly by gravity. Thus the force effecting the objects siginificantly is actually gravity, and the property of the object that is causing it to effected by gravity is its' mass, when the amount of mass is effected by gravity it gives the objects weight.

Now I admit in our universe there is always gravity acting on objects, this comes from Netwonian Physics every object in the universe will attract every other.

I agree if there is a gravitational field in effect then the objects will not travel the same distance or travel at the same speed however the wieght diffrence of the two objects that we would be talking about would be incredibly miniscule.

If the Earth was placed in the galactic void, not in any orbit, simply "dead in space" its' weight would be incredibly minicule, and the pens' weight would be even less, but the diffrence between the two would be incredibly small, when a large objects' wieght is nearing 0 in whatever unit of measurment you want to use, having zero as the neutral point of the measurmeant system, a significantly smaller item like a pen would have a smaller weight but not a significant weight diffrence. Therfore the pen and the Earth would travel at close speeds, not exactly the same speeds but close.

The reason that you can't push a twenty billion pound weight on Earth is because of gravity its' weight is simply to great, but in space that same twenty billion pound weight would be incredibly easy to push if you had something to push against.

However I was not disputing the fact that in an unisolated system two units of matter will not travel at diffrent speeds when fired from the same point with the same amount of force.

Owen Macri

[cobraR478]

No, mass has a HUGE impact on a rocket's ability to move something, even in space. Especially when comparing a pen to a planet. A Saturn V rocket would easily move a pen, or a team of 3 astronauts, but would have a negligible effect on a planet, or any other large body.

[Avatar28]

The reason that you are using this line of thinking is because you are using examples from Earth, correct me if this is incorrect and you are thinking diffrently.

No. The information I'm giving you is basic physics and has nothing to do with it being on earth or not. The rules are the same regardless.

The reason that two objects on Earth of diffrent size could not be propeld equal distance is because:

1) The mass of object one is larger than the mass of object two, so it will be pulled towards Earths' surface faster because it is heavier.

Wrong. The mass of the object has absolutely nothing to do with the rate at which they fall. Other factors such as air resistance can affect it, but in a vacuum, all objects would fall at the same rate regardless of their mass. This was proven during the Apollo missions when an astronaut dropped a feather and a hammer and both hit the surface at the same time.

2) The greater the mass of the object the more friction is acting on it, friction from the air around it.

No, the mass of the object has nothing to do with the resistance of the air it's moving through. Surface area and aerodynamics is your primary factor here.

For the sake of argument let's say for example that the two objects are cubes, simply to not make things more complicated than they need to be by brining in aerodynamics as well.

On Earth the cubes will be propeled diffrent distances when the same amount of force is applied, however in space when not in a significant orbit around another spatial body the two objects will be propeled the same distance at the same speed.

Being in orbit or not really has no real affect on this. With no friction (say in orbit above the atmosphere), both objects would keep going forever until another force acts on them. This is Newton's first law and is also known as inertia. Basically that an object will resist a change in motion. We'll address the implications of this in a bit.

The factor of gravity would not be working significantly on the objects, and the factor of the constant friction of air on the objects would not be acting on the experiment at all.

In space not orbiting a spatial body or being attracted at a siginificant rate by a spatial body, the objects will be virtually wieghtless, not completly, but very close.

Gravity is irrelevant for this discussion. And you are correct that they would be virtually weightless. But NOT massless. Weight is not the same thing as mass. Weight is a result of mass under the influence of gravity but is not an inherent property of an object. Mass is. ALL matter has mass (and I believe that some current thinking is that even energy can have mass) regardless of the presence of gravity (which you can also never truly escape from).

Two cubes of diffrent sizes fired from the same position in space where friction and gravity are not forces that are significantly working on them would travel the same distance at the same speed when proppeld by the same force.

Actually, in the absence of an outside force, both objects would continue on forever. See Newton's first law again.

I agree with you, mass does have an impact on the amount of force required and the distance the object will travel but mass only has a large impact when it is being effected significantly by gravity. Thus the force effecting the objects siginificantly is actually gravity, and the property of the object that is causing it to effected by gravity is its' mass, when the amount of mass is effected by gravity it gives the objects weight.

Almost right. Except that mass has an effect whether you have significant gravity or not. It is actually mass that causes gravity, not the other way around.

Now I admit in our universe there is always gravity acting on objects, this comes from Netwonian Physics every object in the universe will attract every other.

I agree if there is a gravitational field in effect then the objects will not travel the same distance or travel at the same speed however the wieght diffrence of the two objects that we would be talking about would be incredibly miniscule.

If the Earth was placed in the galactic void, not in any orbit, simply "dead in space" its' weight would be incredibly minicule, and the pens' weight would be even less, but the diffrence between the two would be incredibly small, when a large objects' wieght is nearing 0 in whatever unit of measurment you want to use, having zero as the neutral point of the measurmeant system, a significantly smaller item like a pen would have a smaller weight but not a significant weight diffrence. Therfore the pen and the Earth would travel at close speeds, not exactly the same speeds but close.

Not even close I'm afraid. No object in space has any real weight. Weight is only meaningful on the surface of a body like a planet. Also figure, the earth is in orbit which technically means that it's in freefall and thus effectively has no weight. It still has it's 6 sextillion tons of mass, though.

The reason that you can't push a twenty billion pound weight on Earth is because of gravity its' weight is simply to great, but in space that same twenty billion pound weight would be incredibly easy to push if you had something to push against.

However I was not disputing the fact that in an unisolated system two units of matter will not travel at diffrent speeds when fired from the same point with the same amount of force.

Owen Macri

Actually, you could do it on earth too if something were suspending the mass so that it wasn't in contact with the surface. Well, probably not 20 billion lbs but you'd have a hard time with that in space too.

Let me see if I can get it across a different way.

As noted earlier, momentum is defined as mass times velocity. A rocket engine has a finite force that it can apply for a limited period of time. It's not possible to get more than that out of the rocket engine. That force gives you a certain amount of impulse (a change in momentum) that you can apply to an object.

That momentum that you've added to the object from the rocket would be the same, no matter if the object weighs 1 lb or if it weighs 1000 lbs. Let's try this thought experiment. Say that object 1 is made of styrofoam and weighs 1 kilogram. Object 2 is made of lead and weighs 1000 kilograms. Our rocket engine is capable of providing a total change in momentum of 2000 kg m/s (the unit of measurement for momentum. 1 kg m/s is energy of 1 kg moving at 1 m/s). We are in outer space in a perfect vacuum with NO external forces acting on us at all. Starting momentum is 0.

Object 1:
p(momentum) = m (mass) * v (velocity)
2000 kg m/s = 1 kg * v
rearranging gives us
v = 2000 kg m/s / 1 kg (note that here the kg on both sides of the / cancel)
v = 2000 m/s

Object 2:
p = m * v
2000 kg m/s = 1000 kg * v
v = 2000 kg m/s / 1000 kg
v = 2 m/s

So, by applying the same momentum to both objects, the heaver object must necessarily move slower.

By the same token, let's take your hypothetical pen.
Your pen weighs, let's say, 10 grams (.01 kg)
The earth weighs 5.98 x 10^24 kg.

Using the same calculations

Pen
2000 kg m/s = 0.01 kg * v
v = 2000 kg m/s / 0.01 kg
v = 200,000 m/s

Earth
2000 = 5,980,000,000,000,000,000,000,000 kg * v
v = 2000 kg m/s / 5,980,000,000,000,000,000,000,000 kg
v = 3.34 10^-22 m/s (0.000,000,000,000,000,000,000,334 m/s)

So with the same force your pen is moving at 200,000 meters per second and the earth (due to it's MUCH higher mass) is now moving at 334 septillionth of a meter per second.

I hope that makes a little more sense for you.

[_Owen_]

I appoligize, I seriously have no idea what I was thinking about when I typed those posts, I understand your point and... I am sorry I really have absolutly no idea what I was thinking about when I was typing those posts. I agree with you and I don't know what made me think otherwise. It is basic physics, I have no idea what I was thinking when I typed those posts. I appoligize...

Owen Macri