Centripetal Force and Gravity

[PowerMacG5]

Thank you Agent004, at least you understand with the idea of sateliites is orbit, velocity is a function of gravity. And to answer your question in a different way, we can bend space (not gravity). Gravity bends space. Everything with mass bends space to a certain degree. Enerything in the known universe has a gravitational field that bends spacetime, from the smallest subatomic particle, to the largest star. The more that space is bent, the higher the force of gravity will be. If we were capable of producing gravitional fields without the use of something with mass, we could manipulate the universe. As the theory of relativity states, as the velcoity or gravity on an object increase, time begins to slow down for that object. The theory states that in a large gravitational field is present, time in that field is slower than the surrounding space. If we were able to master the manipulation of gravity, we could shorten the distance between two points in space, similar to an Einstein-Rosen bridge.

 

[Agent004]

Now suppose we could manipulate gravity, then it would require large gravitational field to shorten distance between the two point as you said, wouldn't we require some form of anti-gravitational (don't even know it exists or not)device to keep us from 'deforming'? Consider even the gravitation from the sun, it's had neligible effect on distance even though it's many many more time than Earth. The closest thing we known (but not been able to perform studies ) is black hole and we all know what that does to objects when it's sucked in.

 

[Armitage]

<< Thank you Agent004, at least you understand with the idea of sateliites is orbit, velocity is a function of gravity. >>



Nice twist, but saying that orbital velocity is a function of gravity is alot different from saying:

{q} When the velocity is decreased the force of gravity is stronger [/i] >>

 

[PowerMacG5]

Agent004, that is correct, you would need some sort of device to keep you and the ship from deforming under the manipulation of gravity. It would require you generate an antigravitational field equal to the force of the gravitaional field generated to keep you from being crushed under the folding of space. This is a common problem with faster than light travel proposals. Eisnteins theory onlt states that locally you cannot move faster than light. When you fold space, locally you are travelling at sub-light speeds, but when looked at from a distance you are moving faster than light. One such theory on faster than light travel is the Warp Theory by Miguel Alcubierre. He proposes that by creating a bubble around a ship, you could move faster than light. Their is no current theory on how fast space can move within space. We know that their is no limit because the universe is expanding at infinite velocity. Alcubierre propses that the bubble would encapsulate the ship from the outside space. Thsi would form two spaces, inside and outside. The bubble would then manipulate space to fold space in front of the bubble, and unfold in in back. Theoretically this bubble could move at infinite velocity. Now, the ship on the inside space is locally standing still, only the bubble is actually moving. The only problem with folding space, is that theoretically it would require more energy than is in the universe (Just one little problem).

 

[hul]

KraziKid,

Your comment on radiation (NTR):

If you were to use a fusion based reactor you do not need radiation shielding because there is no radiation. In a common fusion reaction 1 deuterium atom and one tritium atom combine to form a helium atom plus a neutron.

First of all, tritium is radioactive. It has a half-life of 12.32 years and emits a beta with mean energy of 6 keV. But tritium is not the problem (a 6 keV beta cannot even penetrate the human skin). The real problem lies with the neutrons!

There is another source of radiation, and it's called neutronic radiation (meaning radiation from neutrons). Fast neutrons (especially from fusion reactions) fall into the class of ionizing radiation, which can damage human tissue. Ionizing radiation consists of any radiation (electromagnetic or particulate) that is able to ionize a neutral atom. As a result, shielding inside a NTR fusion rocket will be required. This is done by using materials that have a small atomic number Z.

Z = atomic number = # of protons in nucleus.

Neutronic radiation can also "activate" other nuclides, causing them to become radioactive! This in turn creates another breed of radionuclides, which will then require a shielding of gamma radiation. Protect yourself from gammas by using a shield made of high Z material. Lead is often used because of its high Z and high density. To protect from neutrons, use water, wax, or some kind of polyethylene (low Z and high density).

 

[PowerMacG5]

Neutronic radiation is not harmful to lighter elements. When neutrons are placed withing the nucleus of a lighter element, it is either accpeted or rejected, it does not split as a heavier element would within a fission reactor.

 

[hul]

Neutronic radiation is not harmful to lighter elements.

That depends on what you mean by harmful. Neutronic radiation makes the strongest metallic alloys become brittle (a major problem in the nuclear industry).


When neutrons are placed withing the nucleus of a lighter element, it is either accpeted or rejected, it does not split as a heavier element would within a fission reactor.

That is true. In the case of a neutron being accepted, the newly created nucleus may be unstable, and thus will emit a gamma, beta, or alpha.


I just wanted to point out that shielding of both neutronic and gamma radiation will be required in a fusion NTR rocket (as well as the fission NTR rocket).

 

[Sahakiel]

Originally posted by: KraziKid
Eisnteins theory onlt states that locally you cannot move faster than light.

Hm.. I was pretty sure it was universal. It's been commonly phrased as "the cosmic speed limit is the speed of light." I've also heard tidbits concerning the speed of light being the only speed for anything in the universe, but that would imply quite a few variations in our understanding of velocity through time.

When you fold space, locally you are travelling at sub-light speeds, but when looked at from a distance you are moving faster than light.

That is a clear violation of Einstein's theory. The whole point of relativistic theory is you cannot observe a speed faster than light speed.
On the other hand, according to quantum mechanics, you could employ tunneling instead, which may or may not be an actual folding of spacetime.

One such theory on faster than light travel is the Warp Theory by Miguel Alcubierre. He proposes that by creating a bubble around a ship, you could move faster than light. Their is no current theory on how fast space can move within space.

I wouldn't know anything about that.

We know that their is no limit because the universe is expanding at infinite velocity.

That's still up for debate. Last I heard, there are strong arguements going three ways: universe expanding, universe static, universe contracting. However, I don't recall ever hearing about the infinite velocity thing.

Alcubierre propses that the bubble would encapsulate the ship from the outside space. Thsi would form two spaces, inside and outside. The bubble would then manipulate space to fold space in front of the bubble, and unfold in in back. Theoretically this bubble could move at infinite velocity. Now, the ship on the inside space is locally standing still, only the bubble is actually moving. The only problem with folding space, is that theoretically it would require more energy than is in the universe (Just one little problem).

First time I heard this idea put this way. Personally, I'm all for taking a chunk of space, shoving it along another dimension (there's, what, 8 more to choose from?) and then inserting it back in. However, I'm not a physics major, so I have no idea what of the implications.

As for the whole thing about shielding, you're going to have to shield the cockpit, anyway. Unless you find another way to avoid radiation from, say, the sun, van allen belts, white dwarfs(?), cbr, and just about everything in the universe that emits energy. Especially electronic circuits on satellites, they tend to fry easily without protection and sometimes they fry, anyway.

 

[PowerMacG5]

Originally posted by: Sahakiel

That is a clear violation of Einstein's theory. The whole point of relativistic theory is you cannot observe a speed faster than light speed.On the other hand, according to quantum mechanics, you could employ tunneling instead, which may or may not be an actual folding of spacetime.

This is not a violation of Einstein's theory. Einstein's special theory of relativity states that LOCALLY you cannot go faster than light. When traveling through an Einstein-Rosen brdge (wormhole) locally you travel faster than light, but in the large picture you are moving faster than light.

 

[Sahakiel]

Nope, it's universal. If you measure the speed of a starship in Andromeda, it ain't gonna be any faster than if it were near Earth.
If you measure speed through an Einstein-Rosen bridge, you'd be measuring it the same way anyone always does. The only difference is your entrance and exist happen to have two paths connecting them. One is your little tunnel of love. The other is what we would call "normal" space. Much like climbing a mountain or carving a tunnel through. Actually, it's exactly the same, only with less dimensions.

Oh, and as for larger picture, that's another part of Einstein's theory. There is no larger picture. There is only your perspective. That's why it's called RELATIVITY.
Then again, physics theories are always incomplete, so you're welcome to make up your own to make up for it. As long as no one can disprove it, no one can say it's wrong.

 

[PowerMacG5]

Sahakiel, I have researched the special theory of relativity, and the general theory of releativity for some time now. I know what I am saying is correct, so if you have your own opinion, go research these theories and then get back to me.

 

[PowerMacG5]

An Einstein-Rosen bridge brings to distant points in the universe closer. As you move through the bridge you travel at sub-light speeds but reach your point of destination faster than traditional space flight. If you use traditional space-flight at the same sub-light speed you used through the Einstein-Rosen bridge, it would take you a lot longer. This is because even though you are travelling at sub-light speeds through the Einstein-Rosen bridge locally, in the giant universal picture you are moving faster than light. Einstein's theory on the speed limit being the speed of light only applies to a ship or object moving through its local space.

 

[Haircut]

KraziKid, after you posted text copied from a web page in another thread I am going to call BS on your knowledge of physics.
Most of what you have posted could be copied from the web or books and from what you have said it appears that you do not have any great understanding of the subject.

If you can tell me what this equation is in the context of general relativity then you I will accept that you know what you are talking about.
Equation
It is a basic equation in GR, so anyone that has studied it should know what the equation means.