Antimatter could fuel rockets, heal patients

CNN.com ^ | 1/10/02 | Fred Katayama

[Brett66]

HUNTSVILLE, Alabama (CNN) --Scientists are looking into a futuristic technology that could lead to interplanetary missions and significantly improve cancer treatments to boot.

Astronauts have gone to the moon, but not other planets in large part because such a trip would require much more propulsion power and time. NASA researchers, however, are investigating antimatter for its propulsion potential.

[freefly]

I've got 2 books at the house that talk about AM and how it can be produced.
One actually has numbers based on systems designed (but obviously not built).
That one came up with figures showing that the AM produced in a dedicated facility
would cost less to put a payload into orbit than current hydrox systems...and it would allow
a lot of the exploration/exploitation of our solar system that is currently pie-in-the-sky to
actually be accomplished (with the corresponding economic benefits).
Do I think it will be done? Not anytime soon.
Even if it is, the fed would be using it for bombs long before anything that might actually pay.
But the potential does exist.
I honestly wouldn't want the fed spending a dime of my tax money on something like this
(or anything else...as soon as the fed is involved the price skyrockets, the efficiancy drops,
and the results -if any- get used as a "bigger stick"), but I wouldn't mind investing a bit of change in such a project.
My kids might actually get a good payoff.;-)
I suspect that there are other alternatives that can be done for far less at this time, (NERVA, robotic factories, etc)
but even at enormous manufacturing inefficiancies, AM will be the best way to go to get to the stars.
Letting the government do it through taxes is the best way to make it take an extra century or 3.

[SuperLuminal]

"Antimatter propulsion is only ten years away. Just as it has been for the last 40 years. "

Unfortunately, AP possibilities died with the death of science in the U.S. 20 years ago.

Technology rules.

Thank you, Mike Mansfield (you commie scumbag!)

[StriperSniper]

Matter Busters!

[Brett66]

I think antimatter propulsion faces two significant problems;
One; Production of the antimatter.
Two; Storage of the antimatter.

The production problem could be eventually overcome, but it's going to take scientific innovations on a scale greater than the Manhattan project and the Apollo program combined.
The storage problem could be more challenging than the production problem. I would have no problem living next to a nuclear plant but I don't think I would want an antimatter storage facility within 100 miles of where I live. The stuff makes thermonuclear weapons seem like firecrackers.

[spunkets]

conservation of energy, momentum and charge apply, so:

e⁺ + e^- -> 2gamma rays heading away from each other, each at m_ec².

[from occupied ga]

Electron and positron do not have equal mass (which is why the universe consists of matter rather than pure radiation) I think that there are some sort of light weight particles produced too, but I just don't remember.

[spunkets]

All particles annihilate the same way, following the conservation laws. If the particles are not of equal mass , but have opposite charge opposite charge, other conservation laws would have to be considered to know the products.

[spunkets]

An positron is a hole in the vacuum left after an electron is raised out of it. The total energy of the electron is equal to the absolute value of the positrons total E. The positron is a negative energy electron moving backwards in time. That is equivalent to a positively charged particle of the same energy, moving forward in time.

[from occupied ga]

An positron is a hole in the vacuum left after an electron is raised out of it. The total energy of the electron is equal to the absolute value of the positrons total E

I don't think that this is the accepted view, but take a look at the www.slac.stanford.edu site and do a search on "electron-positron collision" This will give a whole list of all sorts of things that happen at various collision energies

[AFreeBird]

I guess we need to bring FR's resident physicist into this.

[spunkets]

Here's a page from your link. Electrons and positrons are leptons. They are fundamental particles, that were first realized and described as real by a guy named P. Dirac. Others had dismissed the idea of negative energy solutions from wave descriptions of matter, but Dirac gave the interpretation I gave above, and it still holds.

[freefly]

Actually, we DO have antimatter storage in several areas around the country.
It's only in the trillions of atoms, but they lose NONE of them over multi-month periods of time.
A few trillions atoms doesn't sound like much, but if the magnetic fields were shutdown, you could SEE the flash.
They would have to put some REAL effort into storage of multi-gram amounts!!!

[Brett66]

In the Star Trek chronology they discovered antimatter in the interstellar medium between the stars. They were able to mine substantial quantities of it and use it for reactors on Earth and their spaceships. It's fun to speculate on the ramifications of antimatter technology.
I wonder how much antimatter would be neccessary to run an energy production facility? It would probably be a gram or two. Considering the public's ignorance of nuclear energy, how would the general public view an antimatter power facility? It's likely they would view it negatively, but they might see it as just another Three-Mile Island. Little would they know that if just a tiny amount escaped storage, it would be the biggest nuclear explosion in the history of mankind. I'm sure the greens would let everyone know what it's capable of doing. It might be a hopeless cause to move the politics of this technology.

[wattsmag2]

Quantum mechanical tunneling is the accepted explanation of this as I understand it.

Exactly. Quantum tunneling is what makes faster than light speeds possible.

[from occupied ga]

I didn't see anything on the page that could be interpreted as this:

An positron is a hole in the vacuum left after an electron is raised out of it.

[spunkets]

Dirac's idea that an antiparticle is a hole, out of which a matter particle has been raised rests on the energy levels of the 2 particles. The matter particle has an energy of m_ec² and the antiparticle -m_ec². That makes 2 energy levels, one above the vacuum level of 0, and one an equal magnitude below the vacuum level. The idea of holes is also used in solid state physics. They are lower energy levels a particle can occupy.

When solving wave equations for a free particle one finds 2 solutions for energy. One is positive and the other is the same magnitude, but negative. One can't just dismiss this as a physical impossibility, because further calcs. will give more occurences of neg. E. Dirac accepted the negative Es for an electron going backward in time and interpreted them as positive electrons going forward in time. The mass is the same as the electron, but the energy is negative, hence the term antimatter.

To create an electron/positron pair a gamma ray of >2m_ec² is aimed near a nucleus. The nucleus is required to conserve momentum. The energy is enough to create an electron(m_ec²), and notice now there is an extra m_ec², that is enough to raise the newly created electron out of its hole. That leaves behind what is essentially a hole in the vacuum where electrons can fall into.

" How would you otherwise explain emissions from black holes where the gravitational field creates an escape velocity greater than the speed of light."

The speed of light in the vacuum is an absolute upper limit. The term tunneling does not infer supraluminal velocities. What appears as matter escaping from a black hole is actually matter escaping from the vacuum at the event horizon. That is the surface defined by some radial distance from the center of a black hole, where anything on one side is captured by gravity, and anything on the otherside escapes.

Here is how matter apparently escapes. Heisenberg's uncertainty priciple, in one form say's delta time(t)<= hbar/mc², or hbar devided by the particles E. There is also conservation of energy, that says yall can't create stuff out of nothing. The vacuum's not nothing though, it's something, as Dirac showed it's a sea of particles contained in their holes.

The uncertainty principle say's you can't know the time very well, below a certain limit, if you know the energy well. If you know the energy of a particle and then double it enough to raise it out of it's hole, you know the energy very well. Conservation of E says you can't have this E pop out of the vacuum, for anything longer than hbar/m_ec², but for a time less than that you can. This poping of particles in and out of their holes in the vacuum, for a time less than the uncertainty principle says conservation of E will hold is called vacuum fluctuations. The vacuum is always fluctuating like this and precise calcs involving stuff in this world always require consideration of interaction with the vacuum. R. Feynman did this for the hydrogen atom with quantum electrodynamics and came up with an exact solution, within' the experimental error of the comparison to reality.

Now when folks look at the vacuum fluctuations at the event horizon of a big sucker like a black hole, they find that during the time a particle pops out of the hole, the hole might be sucked away. Then the particle, photon, electron, or whatever, flys off into space and it looks as if it came out of the black hole, due to conservation of momentum. The black hole though sucked what is equivalent to a hole in the vacuum where matter fall into. The black hole IS matter, so an eqivalent amount of the black hole's energy is cancelled out. That makes the black hole look like it's evaporating into space. It will eventually disappear from this process. I think it will fade 'till it explodes, from and increase in the rate of holes captured from the vacuum. This process also gives rise to the appearance of a black body temperature for the black hole. The bigger it is, the hotter it is.

[from occupied ga]

I'm with you up until this one

The bigger it is, the hotter it is.

It would appear that the bigger it is the cooler, since the evaporation rate increase as the hole gets smaller.

[Redcloak]

But because no one knows where to find the antimatter, it has to be created.

That's not the problem. The problem is finding decent dilithium crystals; not that cheap Klingon crap you find on eBay!

[spunkets]

It's not a rate that creates the temperature, but the energy of the largest number of particles that are coming out. It looks like a black body radiator if it's hot most of the particles are high frequency, cold gives a lot of low frequency particles. If two particles, one high and one low frequency, fly of at a low angle from an event horizon, the one with the higher frequency/momentum is more likely to escape. As the curvature of the horizon rises, the more low monentum particles will escape and the the black body temp appears to be going down.

There's a particle density vs frequency distribution for vacuum fluctuations, but I don't have that eq. handy. To determine temp vs size, the above needs to be considered to plot temp vs size. The Chicago Tribune published a colorized x-ray pic of the center of the Milky Way yesterday. There's said to be a couple of black holes there and one great big one. Since nothing was labeled, I took the big bright structure as the biggest black hole. I could be wrong here, so I'll try to find something published, or Physicist will comment.

[P8riot]

Dammit Jim! Thats a helluva way to travel, spreading a man's molecules all over the universe!