The article mentions a wind turbine as a mean for "harvesting' the energy from the air-currents. In principle it might even work. Sail-ships are fuelless vehicles capable of circumnavigating the globe (although conversion from wind-power to the vehicle's propulsion is much more straightforward). Practically? I am really skeptic. Gut-feeling tells me that the turbine-battery-compressor cycle is not efficient enough for self-sustained propulsion. Disclaimer: IAAEP (I am an experimental physicist)
Re:beats the hell outta sendmail...
on
Postfix
·
· Score: 3, Informative
I agree. There is a world of difference between the Postfix and Sendmail. Many years ago I was "vi/etc/whatever" kind of guy whenever a service needed to be configured or tweaked. As I've got older I've learned to appreciate good tools for the system administration. One of the best (IMHO) is the Webmin. It has an awesome Postfix configuration module and it takes 10 minutes to have (non-trivial) mail-server up and running. But even with the Webmin Sendmail is still a bitch to configure.
With all due respect, you are using your home account for business. You should get an appropriate connection (business DSL, T1,...) and make your employer pay for it. If they refuse, you can at least write off some business expenses from your taxes. The (somewhat crummy) analogy would be that professional auto-mechanic bitches about quality of his socket-wrenches but he keeps buying them from the Dollar Store.
..and that neglects the fact that electrons move slower
than light.
A little nitpick: Drift velocity of electrons is slower then
light by several orders of magnitude. In fact, even if the processor
were clocked at say 100 kHz, electrons starting from one opening gate never
reach adjacent gate during one cycle. On the other hand, voltage propagates at
the speed that corresponds to the group velocity of light for given medium.
This is just what it says: a nitpick. Your original analysis
is dead on center.
"The main theoretic limit is that particles cannot be expelled faster than light"
This is not an efficiency limit. The energy and momentum are conserved. As propellant particles (ions) approach relativistic velocities, their mass increases so momentum still builds if one imparts more energy.
Well I work with radioactive materials daily, yet I have no intention of dying any time soon. On the serious note, when you handle a "hot" source you obey three golden rules.
- Distance (e.g. use of long forceps), - Shielding (e.g. lead brick wall screening operator's torso), - Time, (obviously one wants to minimize the exposure.
When we want to perform something particularly complicated (for example: loading a 4 Ci Co-60 source into newly designed collimator) we spend considerable time practicing with the dummy source. Of course we all wear dosimeters, and obey NRC regulations.
The additional yearly dose I am receiving due to my occupation is less than one medical chest x-ray exam.
Yes I do have a physics PhD and I have done a lot of quantum mechanics in my time (low energy electron-molecule collisions). Yet, I don't have a clue about the string theory. Popular articles on the subject do not help at all (at least for me). I guess this is just an extreme example of the typical slashdot discussion. A lot of people are "insightful" and "informative" particularly if the topic is esoteric enough.
> Oh come on... are you calling into question the veracity of the famous MIT experiment?
What MIT experiment?
> How about some facts?
It is much harder to me to prove that no such experiment took place. How about YOU provide some facts?
> So no, it wouldn't sink
I stand corrected. It would not sink because of buoyancy. But the pour agonizing cat would certainly break the bromine surface and get wet (unlike strider on a water surface), which was the point of the parent troll.
Btw, I have handled pure bromine in a lab. It is a nasty stuff. A colleague of mine ended up in the emergency room for inhaling just a whiff from 1 ml vial. A large pool of Br and a cat thrown into it walks, give me a break!
Now this is a troll if I ever saw one. Bromine is the only liquid nonmetallic element. It is a heavy, mobile, reddish-brown liquid, volatilizing readily at room temperature. It is toxic comparable to chlorine. The surface tension of bromine is LESS then that of the water. Cat (or any other live being) in a large pool of bromine has a life expectancy of a few minutes. And yes it would sink.
One application that benefits from adding the nodes (with almost linear scaling in performance) is the Monte Carlo radiation transport. For example, in medical physics people try to calculate a dose distribution in a human body for the various configuration of treatment accelerators. Monte Carlo simulation software "generates" random initial particles (with appropriate probabilities for given accelerator) and than tracks each particle as it propagates and interacts with surrounding tissue. Interactions are randomly generated (hence: Monte Carlo) but again randomness is biased according to the appropriate physics. Each such "history" can be independently generated by a different node thus making parallelization trivial. In my lab I have assembled a 24-node cluster and it takes about 4-8 hr to calculate dose distributions for the most cases. With a 1000 node cluster it would be possible to do this sort of calculations routinely in clinics during the treatment planing and actual treatment. This will mean that the cancer patients will have improved survivability odds due to the more precise targeting of the tumors.
I have a pretty un-pronouncable name but that does not stop telemarketers for a minute. Only when I learned about Missouri "No Call" list I was able to have a peaceful diner.
The only spectrometry possible from the orbit is a passive one. The optical spectrum of the solid chunk of (dry)ice does not contain any characteristic lines or bands. Good luck with determining the "exact chemical composition".
Now if you had a probe LANDED on a pole than you could determine composition with almost arbitrary precision.
Those guys were obviously trying to guess composition from the orbit
Back in my old country (Eastern Europe) the software piracy was a way of living. Regular way to buy a software even for the government institutions was to go to your local (pirate) dealer. Those joints were public retail shops with a bunch of PC's in the backroom burning popular titles 24/7. Interestingly enough they were "legal" in a sense that they were registered businesses, paying taxes. Anyway, I had an opportunity to talk with several owners of these outfits and the general consensus among them was one word: "Plextor". Yamaha, according to them, was to be avoided like a plague. Typical lifetime of Yamaha burners was less than one day in that environment!
I see your point. It is like making a multi-cellular robotic organism.
However, it does not help if you want to make microscopic "less then a red blood cell" camera. I am still maintaining that even with the "sci-fi" nano-technology you cannot overcome physical limitations an produce MICROSCOPIC imager.
In his preview of the book Freeman J. Dyson points out the bad science, e.g. limitation of nanobots' speed due to the viscous forces.
There are however, numerous other limitations if "the camera is smaller than a red blood cell". Normal human erythrocyte is 6 - 8 um in diameter, about ten wavelengths of the visible light. Even if this is a diameter of the camera lens only, the camera would have a very poor resolution due to the diffraction limit. Such camera would also suffer from the poor light sensitivity and bad S/N ratio.
Even with the current incredible rate of nano-technology development some things will not be possible ever. Do not expect microscopic spying bugs anytime soon.
I am not trashing the novel, merely trying to point out some facts about nano-technology since it provokes some people to be paranoid.
While the Red Hat distribution update works relatively reliable, I would not be willing to try that on production system. I takes time and skill to fine tune the sever. What happens if you finish your update to the new major version only to find that your configuration files are incompatible? Your 2 hours announced outage suddenly becomes much longer. Update feature is nice for home system but for 24/7 shop you must came up with much more robust solution.
The very first computer i have ever played with was PDP-8/e. It was "loaded" machine with 16 k words of RAM (magnetic core of course). The front panel of the machine had a row of switches that enabled direct, true "machine language programming". You were able to manually deposit words, both in registers and memory. Since PDP-8 was 12 bit machine it was natural to represent the machine word in Octal. In order to boot system from scratch, you needed to deposit in memory ~20 word program called: "RIM" (Read In Mode). Once RIM is loaded it started punched tape reader in teletype in which you hopefully loaded "BIN" tape. Once The BIN program is started you had rudimentary OS for reading and running whatever programs you had on paper tapes. Most often we used "Focal", the interpreter very similar to BASIC. Later, we bought PDP-11 with 80 MB hard disk and multi user OS (note my user id), but "Eight" was the machine that hooked me for life.
Please enlighten me. IANAP (I AM a nuclear physicist) but I never heard of fusion reactor that needs "a very large 3-foot thick shield of lithium". Care to post some references?
Don't get me wrong, it is possible that some research group is actually working on controlled thermonuclear fusion project that involves mentioned shield, but I honestly cannot think of experimental setup where 1 m layer of lithium does anything useful.
The site seems to be/.-ted and no karma-whore posted a reprint yet. So i did not RTFA. However to "deflect incoming asteroids & comets" with photons is ridiculous idea. Photons carry momentum h*nu/c and energy h*nu. One way to treat the problem is to consider a simple mechanical collision of photon and target (asteroid). I did a "back of an envelope calculation" and derived a following results: For the visible photons of 550 nm, a beam of 1 GW produces a force of 6.7 N (~ 1.5 lb). Now that is really going to take care of that 1 000 000 t asteroid.
Now let's try another approach. Let's assume that the said 1 GW beam vaporizes surface of the asteroid and that "rocket effect" has 100% efficiency. 1 GW applied on the 1 000 000 t body for the duration of say 86400 s (1 day), changes the body's velocity for 415 m/s. This is much better, particularly if the target is irradiated far away from the Earth. However, with the current technology it is feasible as much as the "tractor beam".
Re:don't mean to be a pessimist, but...
on
Pipeline Mass Transit?
·
· Score: 2, Interesting
Right to the point! Maintaining the vacuum in high-volume vessels is extremely difficult. In addition to the parent post:
- Need for constant pumping takes energy. In our lab a vacuum pump consumes 3 kW in order to maintain pressure of 10 ^-6 Torr for a modest 30 l chamber.
-From the article: "Constructing a highway causes over twenty times the environmental damage as building ETT. ETT uses much less materials." Bull! Vacuum chamber of that volume must be made of metal (stainless steel probably) with massive walls. "tube capacity is high (can exceed 80 lanes of traffic)" Can you imagine amount of metal needed for say 100 miles of this miraculous transportation system? BTW, prior to the commission, Vacuum vessels must be cleaned with nasty chemicals in order to avoid degassing.
I am under the impression that et3.com is also offering the Brooklyn Bridge for sale.
It is called Monte Carlo simulation of the radiation transport. Basically one tracks propagation of the high-energy particles as they progress trough the matter (human tissue). e.g. if you simulate a brachytherapy source (radioactive "seed" implanted in tissue), the code "creates" photon with energy characteristic for a given isotope. The direction vector is chosen by a random number generator (RNG). The RNG also decides at what point along the photon's trajectory an interaction with surrounding matter should occur according to the physical probabilities. After the interaction, there is a bunch of scattered particles (photons, electrons and positrons) and the code continues to track them until the energy of the n-th generation particle drops below certain energy (10 keV for electrons) at which moment particle's energy is deposited as a dose. The object of the simulation is to obtain precise dose distribution. In order to achieve good statistics one needs to run millions and millions of histories. Beowulf clusters are ideal for this job because histories are independent and there is no need for the fast shared memory and a fancy interprocess communication. I had a pleasure to assemble 24-node 1.6 GHz AMD cluster and we achieved sub-minute simulation times, a result that makes this technique suitable for everyday clinical practice.
Re:Skin Cancer
on
Solar Surgery
·
· Score: 2, Interesting
The article mentions "concave dish" signifying that we are dealing with the reflective optics. Assuming that the mirror is Al coated (very reasonable assumption), we are talking about 90% or more of UV reflectivity. Some posts in this thread were referring to a "different focal lengths" which is non-applicable to the reflective objective (there is no chromatic aberration in the absence of dispersive media). Now the fiber light guide is a completely different proposition. It is probably not UV transparent though it might be. Anyway it is trivial to filter out UV if desired. That finally brings us to the cancer risks associated with the possible UV irradiation. The mechanism that triggers cancer growth involves cell mutation due to the photo-dissociation of the DNA. But it is also necessary that the mutated cell survives and produces a new generation of (now) tumor cells. With highly focused radiation of the "light knife" it is highly unlikely that any of the irradiated cells can survive.
Bose Einstein Condensates
on
Stopping Light
·
· Score: 2, Informative
The article mentions experiment from 1999 where light was slowed to the "bicycle speed". This was accomplished by shining light trough "Bose-Einstein" condensate. Bosons are particles with integer spin (e.g. photons). In 1924 it was predicted that an ensemble of bosons could, under certain conditions, undergo a phase transition. This is analogue to vapor condensation or crystallization of liquid. In order to create Bose-Einstein condensate it is necessary to achieve temperatures less than one millionth of a degree above absolute zero. First successful experiment was performed in 1995 utilizing laser cooling. One of the properties of BE condensate is that the light propagates trough it with speed that is 20-million-fold slower than a speed of light in vacuum. The article is not very informative about actual physics involved in the newest experiment. However there is a nice description at: http://www.aip.org/physnews/update/521-1.html. Also there is a an interesting site about Bose-Einstain condensation at
http://www.colorado.edu/physics/2000/bec/index.h tm l, with some nifty Java applets
If we apply Newton's law of gravitation: Strength of Sun's gravitational field = G*M/r^2 = 0.0059 m/s^2 (G = Newtonian gravity constant; M = Solar mass ; r = Sun - Earth distance)
That is only 0.006g. Since we are traveling from Sun towards Mars, field strength is only getting lower. Now let's do another exercise: Earth - Mars distance varies between 55 and 350 million kilometers. Let's assume that space vehicle has to cover 100 million km. For the first part of the voyage it accelerates with constant acceleration: a=0.01 g (+ 0.006 g to compensate for the Sun) and then spends the rest of the journey braking at -a. If you do the math (hint: s=at^2/2). it turns out that it takes 73 days to get to the Mars. It would take hundreds if not thousands of g at the liftoff and landing to do it conventional way (I am not volunteering for that mission!). Note that we are talking about 0.01 g. That is far less acceleration in comparison to say: eighteen-wheeler, loaded with lead bricks, powered by the Yugo's engine. Disclaimer: I haven't done the math if it is feasible to achieve 0.01 g. It is 1 AM and I don't feel up to it. Any colleagues willing to solve Meshchersky equation?
Slashdot Mirror
The article mentions a wind turbine as a mean for "harvesting' the energy from the air-currents. In principle it might even work. Sail-ships are fuelless vehicles capable of circumnavigating the globe (although conversion from wind-power to the vehicle's propulsion is much more straightforward).
Practically? I am really skeptic. Gut-feeling tells me that the turbine-battery-compressor cycle is not efficient enough for self-sustained propulsion.
Disclaimer: IAAEP (I am an experimental physicist)
I agree. There is a world of difference between the Postfix and Sendmail. /etc/whatever" kind of guy whenever a service needed to be configured or tweaked. As I've got older I've learned to appreciate good tools for the system administration. One of the best (IMHO) is the Webmin. It has an awesome Postfix configuration module and it takes 10 minutes to have (non-trivial) mail-server up and running. But even with the Webmin Sendmail is still a bitch to configure.
Many years ago I was "vi
With all due respect, you are using your home account for business. You should get an appropriate connection (business DSL, T1,...) and make your employer pay for it. If they refuse, you can at least write off some business expenses from your taxes.
The (somewhat crummy) analogy would be that professional auto-mechanic bitches about quality of his socket-wrenches but he keeps buying them from the Dollar Store.
A little nitpick: Drift velocity of electrons is slower then light by several orders of magnitude. In fact, even if the processor were clocked at say 100 kHz, electrons starting from one opening gate never reach adjacent gate during one cycle. On the other hand, voltage propagates at the speed that corresponds to the group velocity of light for given medium.
This is just what it says: a nitpick. Your original analysis is dead on center.
"The main theoretic limit is that particles cannot be expelled faster than light"
This is not an efficiency limit. The energy and momentum are conserved. As propellant particles (ions) approach relativistic velocities, their mass increases so momentum still builds if one imparts more energy.
However, your main point is valid.
Well I work with radioactive materials daily, yet I have no intention of dying any time soon.
On the serious note, when you handle a "hot" source you obey three golden rules.
- Distance (e.g. use of long forceps),
- Shielding (e.g. lead brick wall screening operator's torso),
- Time, (obviously one wants to minimize the exposure.
When we want to perform something particularly complicated (for example: loading a 4 Ci Co-60 source into newly designed collimator) we spend considerable time practicing with the dummy source. Of course we all wear dosimeters, and obey NRC regulations.
The additional yearly dose I am receiving due to my occupation is less than one medical chest x-ray exam.
Yes I do have a physics PhD and I have done a lot of quantum mechanics in my time (low energy electron-molecule collisions). Yet, I don't have a clue about the string theory. Popular articles on the subject do not help at all (at least for me).
I guess this is just an extreme example of the typical slashdot discussion. A lot of people are "insightful" and "informative" particularly if the topic is esoteric enough.
> Oh come on... are you calling into question the veracity of the famous MIT experiment?
What MIT experiment?
> How about some facts?
It is much harder to me to prove that no such experiment took place. How about YOU provide some facts?
> So no, it wouldn't sink
I stand corrected. It would not sink because of buoyancy. But the pour agonizing cat would certainly break the bromine surface and get wet (unlike strider on a water surface), which was the point of the parent troll.
Btw, I have handled pure bromine in a lab. It is a nasty stuff. A colleague of mine ended up in the emergency room for inhaling just a whiff from 1 ml vial. A large pool of Br and a cat thrown into it walks, give me a break!
Now this is a troll if I ever saw one. Bromine is the only liquid nonmetallic element. It is a heavy, mobile, reddish-brown liquid, volatilizing readily at room temperature. It is toxic comparable to chlorine. The surface tension of bromine is LESS then that of the water.
Cat (or any other live being) in a large pool of bromine has a life expectancy of a few minutes. And yes it would sink.
One application that benefits from adding the nodes (with almost linear scaling in performance) is the Monte Carlo radiation transport. For example, in medical physics people try to calculate a dose distribution in a human body for the various configuration of treatment accelerators. Monte Carlo simulation software "generates" random initial particles (with appropriate probabilities for given accelerator) and than tracks each particle as it propagates and interacts with surrounding tissue. Interactions are randomly generated (hence: Monte Carlo) but again randomness is biased according to the appropriate physics. Each such "history" can be independently generated by a different node thus making parallelization trivial.
In my lab I have assembled a 24-node cluster and it takes about 4-8 hr to calculate dose distributions for the most cases. With a 1000 node cluster it would be possible to do this sort of calculations routinely in clinics during the treatment planing and actual treatment. This will mean that the cancer patients will have improved survivability odds due to the more precise targeting of the tumors.
Cheers,
Beowulf's root
I have a pretty un-pronouncable name but that does not stop telemarketers for a minute.
Only when I learned about Missouri "No Call" list I was able to have a peaceful diner.
What kind of spectrometer?
...)
Mass?
Optical? (transmission, emission, raman, IR, UV...)
Nuclear? (alpha, beta, gamma, neutron activation,
The only spectrometry possible from the orbit is a passive one. The optical spectrum of the solid chunk of (dry)ice does not contain any characteristic lines or bands. Good luck with determining the "exact chemical composition".
Now if you had a probe LANDED on a pole than you could determine composition with almost arbitrary precision.
Those guys were obviously trying to guess composition from the orbit
Back in my old country (Eastern Europe) the software piracy was a way of living. Regular way to buy a software even for the government institutions was to go to your local (pirate) dealer. Those joints were public retail shops with a bunch of PC's in the backroom burning popular titles 24/7. Interestingly enough they were "legal" in a sense that they were registered businesses, paying taxes.
Anyway, I had an opportunity to talk with several owners of these outfits and the general consensus among them was one word: "Plextor".
Yamaha, according to them, was to be avoided like a plague. Typical lifetime of Yamaha burners was less than one day in that environment!
I see your point. It is like making a multi-cellular robotic organism.
However, it does not help if you want to make microscopic "less then a red blood cell" camera. I am still maintaining that even with the "sci-fi" nano-technology you cannot overcome physical limitations an produce MICROSCOPIC imager.
In his preview of the book Freeman J. Dyson points out the bad science, e.g. limitation of nanobots' speed due to the viscous forces.
There are however, numerous other limitations if "the camera is smaller than a red blood cell". Normal human erythrocyte is 6 - 8 um in diameter, about ten wavelengths of the visible light. Even if this is a diameter of the camera lens only, the camera would have a very poor resolution due to the diffraction limit. Such camera would also suffer from the poor light sensitivity and bad S/N ratio.
Even with the current incredible rate of nano-technology development some things will not be possible ever. Do not expect microscopic spying bugs anytime soon.
I am not trashing the novel, merely trying to point out some facts about nano-technology since it provokes some people to be paranoid.
While the Red Hat distribution update works relatively reliable, I would not be willing to try that on production system. I takes time and skill to fine tune the sever. What happens if you finish your update to the new major version only to find that your configuration files are incompatible? Your 2 hours announced outage suddenly becomes much longer.
Update feature is nice for home system but for 24/7 shop you must came up with much more robust solution.
The very first computer i have ever played with was PDP-8/e. It was "loaded" machine with 16 k words of RAM (magnetic core of course). The front panel of the machine had a row of switches that enabled direct, true "machine language programming". You were able to manually deposit words, both in registers and memory. Since PDP-8 was 12 bit machine it was natural to represent the machine word in Octal.
In order to boot system from scratch, you needed to deposit in memory ~20 word program called: "RIM" (Read In Mode). Once RIM is loaded it started punched tape reader in teletype in which you hopefully loaded "BIN" tape. Once The BIN program is started you had rudimentary OS for reading and running whatever programs you had on paper tapes. Most often we used "Focal", the interpreter very similar to BASIC. Later, we bought PDP-11 with 80 MB hard disk and multi user OS (note my user id), but "Eight" was the machine that hooked me for life.
You have a point (both with google and the lithium).
I stand corrected. It is the word "shield" that got me sidetracked.
Cheers.
Please enlighten me. IANAP (I AM a nuclear physicist) but I never heard of fusion reactor that needs "a very large 3-foot thick shield of lithium". Care to post some references?
Don't get me wrong, it is possible that some research group is actually working on controlled thermonuclear fusion project that involves mentioned shield, but I honestly cannot think of experimental setup where 1 m layer of lithium does anything useful.
The site seems to be /.-ted and no karma-whore posted a reprint yet.
So i did not RTFA. However to "deflect incoming asteroids & comets" with
photons is ridiculous idea. Photons carry momentum h*nu/c and
energy h*nu. One way to treat the problem is to consider a simple mechanical
collision of photon and target (asteroid). I did a "back of an envelope calculation"
and derived a following results:
For the visible photons of 550 nm, a beam of 1 GW produces a force of 6.7 N (~ 1.5 lb).
Now that is really going to take care of that 1 000 000 t asteroid.
Now let's try another approach. Let's assume that the said 1 GW beam vaporizes surface of
the asteroid and that "rocket effect" has 100% efficiency. 1 GW applied on the
1 000 000 t body for the duration of say 86400 s (1 day), changes the body's velocity
for 415 m/s. This is much better, particularly if the target is irradiated far away from the
Earth. However, with the current technology it is feasible as much as the "tractor beam".
Right to the point! Maintaining the vacuum in high-volume vessels is extremely difficult. In addition to the parent post:
- Need for constant pumping takes energy. In our lab a vacuum pump consumes 3 kW in order to maintain pressure of 10 ^-6 Torr for a modest 30 l chamber.
-From the article: "Constructing a highway causes over twenty times the environmental damage as building ETT. ETT uses much less materials."
Bull! Vacuum chamber of that volume must be made of metal (stainless steel probably) with massive walls.
"tube capacity is high (can exceed 80 lanes of traffic)"
Can you imagine amount of metal needed for say 100 miles of this miraculous transportation system? BTW, prior to the commission, Vacuum vessels must be cleaned with nasty chemicals in order to avoid degassing.
I am under the impression that et3.com is also offering the Brooklyn Bridge for sale.
It is called Monte Carlo simulation of the radiation transport. Basically one tracks propagation of the high-energy particles as they progress trough the matter (human tissue). e.g. if you simulate a brachytherapy source (radioactive "seed" implanted in tissue), the code "creates" photon with energy characteristic for a given isotope. The direction vector is chosen by a random number generator (RNG). The RNG also decides at what point along the photon's trajectory an interaction with surrounding matter should occur according to the physical probabilities.
After the interaction, there is a bunch of scattered particles (photons, electrons and positrons) and the code continues to track them until the energy of the n-th generation particle drops below certain energy (10 keV for electrons) at which moment particle's energy is deposited as a dose.
The object of the simulation is to obtain precise dose distribution. In order to achieve good statistics one needs to run millions and millions of histories.
Beowulf clusters are ideal for this job because histories are independent and there is no need
for the fast shared memory and a fancy interprocess communication.
I had a pleasure to assemble 24-node 1.6 GHz AMD cluster and we achieved sub-minute simulation times, a result that makes this technique suitable for everyday clinical practice.
The article mentions "concave dish" signifying that we are dealing with the reflective optics. Assuming that the mirror is Al coated (very reasonable assumption), we are talking about 90% or more of UV reflectivity. Some posts in this thread were referring to a "different focal lengths" which is non-applicable to the reflective objective (there is no chromatic aberration in the absence of dispersive media). Now the fiber light guide is a completely different proposition. It is probably not UV transparent though it might be. Anyway it is trivial to filter out UV if desired. That finally brings us to the cancer risks associated with the possible UV irradiation. The mechanism that triggers cancer growth involves cell mutation due to the photo-dissociation of the DNA. But it is also necessary that the mutated cell survives and produces a new generation of (now) tumor cells. With highly focused radiation of the "light knife" it is highly unlikely that any of the irradiated cells can survive.
The article mentions experiment from 1999 where light was slowed to the "bicycle speed". This was accomplished by shining light trough "Bose-Einstein" condensate. Bosons are particles with integer spin (e.g. photons). In 1924 it was predicted that an ensemble of bosons could, under certain conditions, undergo a phase transition. This is analogue to vapor condensation or crystallization of liquid. In order to create Bose-Einstein condensate it is necessary to achieve temperatures less than one millionth of a degree above absolute zero. First successful experiment was performed in 1995 utilizing laser cooling. One of the properties of BE condensate is that the light propagates trough it with speed that is 20-million-fold slower than a speed of light in vacuum.
h tm l,
The article is not very informative about actual physics involved in the newest experiment. However there is a nice description at: http://www.aip.org/physnews/update/521-1.html.
Also there is a an interesting site about Bose-Einstain condensation at
http://www.colorado.edu/physics/2000/bec/index.
with some nifty Java applets
>Don't forget about the pull of the Sun's gravity
If we apply Newton's law of gravitation:
Strength of Sun's gravitational field = G*M/r^2 = 0.0059 m/s^2
(G = Newtonian gravity constant; M = Solar mass ; r = Sun - Earth distance)
That is only 0.006g. Since we are traveling from Sun towards Mars, field strength is only getting lower.
Now let's do another exercise:
Earth - Mars distance varies between 55 and 350 million kilometers. Let's assume that space vehicle has to cover 100 million km. For the first part of the voyage it accelerates with constant acceleration:
a=0.01 g (+ 0.006 g to compensate for the Sun) and then spends the rest of the journey braking at -a. If you do the math (hint: s=at^2/2). it turns out that it takes 73 days to get to the Mars. It would take hundreds if not thousands of g at the liftoff and landing to do it conventional way (I am not volunteering for that mission!).
Note that we are talking about 0.01 g. That is far less acceleration in comparison to say: eighteen-wheeler, loaded with lead bricks, powered by the Yugo's engine.
Disclaimer: I haven't done the math if it is feasible to achieve 0.01 g. It is 1 AM and I don't feel up to it. Any colleagues willing to solve Meshchersky equation?