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Comment Re:"Laser Strikes" define? (Score 3, Informative) 161

I've been lasered when flying my plane. The beam is big at these long distances, so ti isn't a tiny beam going into your eye, it lights up the cockpit and looks like a very bright point of light. Since your eye focuses the light to a point, lasers can be dangerous at fairly low power levels.

In a plane even if the beam is not damaging it is very distracting, and distraction is a major cause of aircraft accidents. in my case they kept the beam on the plane for many seconds so it was clearly intentional.

Its pretty common - several pilots I've spoken to have been lasered. This is the second time its happened to me.

Comment Re:Yes, but they're not discriminating on race... (Score 1) 386

Imagine that members of a particular ethnicity are on average less likely to pay their debts. If a person is of that ethnicity, I do not believe that it is desirable (or legal) to deny them loans based on that ethnicity - that should only be done based on their individual ability / likelyhood of paying.

A fair system might still result in fewer loans to people of some ethnicity, but that would be due to the behavior or the individuals, not due to their group membership.

Comment Re: Problem with Artifical Stupidity: discriminati (Score 1) 386

I think it is a very general problem with machine decision-making. We have laws that prevent using certain protected characteristics (race, gender, etc) in hiring, loan, housing or other decisions). An automated decision making system could act on things that were proxies for these protected characteristics in a way that would not be immediately obvious. This provides a way for organizations to (intentionally or not) get around anti-discrimination laws.

Comment Problem with Artifical Stupidity: discrimination (Score 3, Interesting) 386

Its possible to come up with algorithms that are statistically valid, but discriminatory. For example, in the US African Americans are on average lower income than whites,so it it is likely that average they are less able to repay debts. Anything that correlates with race might statistically be valid, but is racist and if done explicitly would violate all sorts of laws. How do you prove that you are not using proxies for race, or other protected classes in an analysis like this.

Systems that analyze the behavior of friends have a similar problem: people from disadvantaged cultures will have a more difficult time receiving loans, getting jobs etc, not because of what they personally did, but because of what people of their culture did. This is the basis of racism.

Comment Re:Word limit not helping (Score 3, Informative) 160

For theoretical physics I think it is hopeless. There are just too man concepts that would take too long to introduce. I'm a PhD physicist and I can't read theoretical physics papers - not the jargon, but I'm just not comfortable with the concepts. Just try explaining a HIggs boson to a non-physicist - and that is a decades old concept. Strings are hopeless, but they are just the basics needed for modern physics.

Other subjects are probably similar.

Comment Re:Not so easy (Score 1) 52

They probably assume the same techniques will be used as for other accelerators. Shielding. Interlocked doors, Radiation detectors etc.

The sophistication of these systems depends on the accelerator power and energy. Some are no more dangerous than doctor's X-ray machines, others can get near (small) reactor like levels of risk.

Comment Re:Not so easy (Score 2) 52

You are absolutely right that this depends a lot on the application. I'm from a high energy physics accelerator background so I tend to see things in those terms. Trying to ignore that bias I see as typical accelerator applications:

1) High energy physics. This is designed for electrons so we are talking about a linear collider (look up ILC for example). Those need very high energy (TeV scale), since we've already done up to 200GeV with LEP. Very high beam powers (the cross sections are low). and very tiny focal spots (same reason). The best final focus designs for a TeV scale collider are multi-kilometer long. A LOT of work has gone into this, so while there might be a trick people have looked very hard. I don't think high frequency machines make sense for this.

2) X-ray lasers. ( see LCLS) These need several GeV beams with extremely high stability and high phase space density. It would be difficult to get the high electron density with high frequency accelerators. Also, a 5 GeV accelerator is only 50M of X-band structures, and the the FEL laser itself is ~100M. So you would win some space, but not dramatically.

3). Nuclear physics. I don't know anything about this field. I don't know if low current beams are interesting.

4). Medical: typically 20MeV. This is a promising application. There is competition from laser accelerators (direct and plasma) which are in a similar stage of development. I don't know who wins.

5). Industrial: usually also low energy, but high power then medical. Maybe an option, but they usually aren't size constrained so conventional accelerators can be used .

6). ADSR: here and efficiency are everything. Need multi-megawatt beams- and protons which aren't very good for a mm-wave accelerator. I think ADSR is great, but the big technological problems are efficiency and reliability.

There may be a lot of other applications that I'm not aware of.

Comment Not so easy (Score 4, Informative) 52

There have been designs for high frequency accelerators for a long time. These range from normal ~few GHz machines like SLAC, to 10s of GHz (CLIC - proposed), to THz to direct optical acceleration. There are also plasma based 2-beam accelerators which have extremely high gradients (10 GeV/M).

There are some general trade-offs:

Higher frequency -> more energy / length, but lower beam charge and tighter tolerances, and usually lower efficiency. Depending on the application this may or may not be a good trade, but very high frequency accelerators have so far found limited practical application. Most applications for high energy also require fairly high beam power and good beam quality.

In particular high energy physics accelerators require very high average beam power (megawatts), which require high wall-plug efficiency, (to keep operating costs down). So far none of the high frequency accelerator designs look practical for this application. In addition for a high energy physics machine the final focus system is kilometers long, so even if the accelerators could shrink, it in no way results in a tiny machine.

There is a lot of interest in high frequency accelerators for medical and other low energy low power applications. This is a case where there are a number of ways to solve the problem and we need to see which technology is ultimately the cheapest / easiest. Here mm-wave is competing with lasers and other types.

For comparison, a conventional (x-band) 20MeV accelerator is 20cm long. The shielding for a 20MeV beam (which can generate neutrons) could easily be a meter of concrete.

I'm not knocking this technology at all, it may be very useful for some applications. I just want to counter the idea that it will transform particle accelerators.

Joe Frisch

Comment extremely low probability but worth checking (Score 1) 339

It is exceedingly unlikely this is the result of the actions of an alien civilization, but the importance of such a discovery makes it worth some effort to investigate. In any case its a non-understood astrophysical phenomenon so its interesting to investigate in any case.

If you see something strange, studying more is a good plan in general

Comment Re:Academia is willing to protect total dicks (Score 1, Insightful) 345

But that doesn't matter.
The imbalance of power between an academic adviser and a student is too large for there to be any reasonable concept of consent. He can take years from her life, possibly ruin her academic future. It is his responsibility to avoid any sort of sexual contact. His only excuse for any sort of sexual interaction with her is if she raped him.

Comment Re:Academia is willing to protect total dicks (Score 1) 345

Yes this is a serious problem. A graduate adviser has a tremendous amount of power over their students and its easy for that to lead to abuse. It makes sense for universities to ban any sexual / romantic contact between students and professors for this reason.

I haven't personally seen this, but it doesn't surprise me at all that it happened. I have no practical advice to offer to someone in her situation either. Even with proof enough to get her professor fired, or even convicted - her career is badly damaged.

Abuse of students can take many forms, but sexual harassment is one of the worst.

Comment Footprint photo (Score 4, Insightful) 170

The footprint photo at the end of the brochure is 50 years old and we haven't been back. NASA has been talking about a manned mars mission 20 years in the future for the last 50 years. OK to be honest it was 10 years in the future 50 years ago.

The space age is over.

Eventually some civilization, mayl find the Apollo landers and and wonder why we gave up with the stars withing our grasp. We won't be around for them to ask.

The secret of success is sincerity. Once you can fake that, you've got it made. -- Jean Giraudoux