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Comment: Re:Wormholes + a flat universe (Score 1) 358

by rotenberry (#47164563) Attached to: The Disappearing Universe

I do not believe that what you wrote is correct.

Empty space is globally flat, but because gravity is a force with unlimited range no universe with any mass in it is globally flat.

At small enough scale every spacetime is locally flat, although that scale may be very small near a black hole. Only at the location of the singularity is it impossible to find a locally flat reference frame.

Comment: And automobile alarms (Score 2) 114

by rotenberry (#46609603) Attached to: 5.1 Earthquake Hits California

During the 1987 Whittier Narrows earthquake every car alarm in the area was set off.

Although I now live in quake-free Texas the first thing I think of when a car alarm goes off is Earthquake! It must be the reptile part of the brain or something. Once my heart starts beating and the rest of my brain starts working I realize there is no earthquake.

Comment: Re:Or, stay low tech ... (Score 1) 133

by rotenberry (#45833093) Attached to: Ask Slashdot: Life Organization With Free Software?

Note taking on paper has a number of advantages, but one disadvantage is that the information is indexed only one way: by date. I prefer bound, numbered laboratory notebooks, but unless you have a pretty good idea when you wrote it down it is difficult to find the information you want.

Retrieving information is the reason you write it down, isn't it?

Of course, I learned in a lecture by Jack Kilby that the only reason he was granted the patent on the integrated circuit (and, later, his Nobel Prize) was because he had the bound notebooks he used periodically signed and dated by his manager and then notarized.

Comment: Re:Easy solution (Score 2) 120

by rotenberry (#45783595) Attached to: E-Books That Read You

I, too, have an e-book reader that does not have the hardware to go on the internet.

Isn't the Unix philosophy to have a single command that does only one job well? "cat", "head", "tail", "ls" are examples of the commands I have in mind. Extend this idea to the real world. I have an e-book reader, a music player, a (dumb) phone, and a wristwatch.

A smart phone is a bit like the Microsoft operating system: it does everything, but does not do any of them well.

Not much of a bargain. Mediocre performance AND the loss of privacy.

Comment: Re:The worst thing... (Score 2) 575

by rotenberry (#45691449) Attached to: GitHub Takes Down Satirical 'C Plus Equality' Language

I am old enough to remember seeing restrooms marked "white" and "colored". During the bad old days everyone understood that a sign that said "We reserve the right to refuse service to any person" was a code phrase for "whites only". It is sad to read that GitHub is so tone-deaf to the lessons of American history.

from http://www.legalmatch.com/law-library/article/restaurants-right-to-refuse-service.html

"Does a Restaurant Have the Unrestricted Right to Refuse Service to Specific Patrons?

No. The Civil Rights Act of 1964 explicitly prohibits restaurants from refusing service to patrons on the basis of race, color, religion, or natural origin. In addition, most courts don't allow restaurants to refuse service to patrons based on extremely arbitrary conditions. For example, a person likely can't be refused service due to having a lazy eye."

Comment: Contributing Adafruit Software (Score 5, Interesting) 139

by rotenberry (#45455697) Attached to: Interview: Ask Limor Fried About Open-Source Hardware and Adafruit

As a happy owner of the Adafruit Blue&White 16x2 LCD+Keypad Kit for Raspberry Pi I have used and modified the software that originally came with this kit.

There are some obvious uses for this kit. Two examples would be displaying its IP address and using the keypad to shutdown the Pi.

However, when I was modifying the software I could not find specific instructions on how to contribute software back to your site. I just checked again this morning (even the FAQ), and, if these instructions exist, I could not find them.

How does one contribute back?

Comment: "Flight" by Chris Kraft (Score 1) 262

by rotenberry (#44748911) Attached to: Chris Kraft Talks About The Decline of NASA

I watched on TV the Mercury capsules launch on TV as a boy, and as a young man I worked on the Galileo mission. Of all the books I have read about the space program none is better than Chris Karft's "Flight - My Life in Mission Control".

It is not an engineering book, but a book written by an engineer. For example, the description of the problems during Apollo 13 are described better here than anywhere. He never tries to make hemself or anyone else look better than they actually were. He often is quite critical of NASA's spin control.

Comment: Re:Micrometeorites (Score 3, Interesting) 193

by rotenberry (#44133857) Attached to: Scientists Work To Produce 'Star Trek' Deflector Shields

The velocity of the craft does matter, and I will explain why.

If the velocity of the craft is much greater than the particles (think of dust floating in the air), then the craft will indeed sweep out all the particles in its line of motion.

However, the the velocity of the craft is much less that the particles (think cosmic rays in interplanetary space), then there will be the same number of collisions per unit time during the trip. A five hundred day trip will have ten times the number of collisions as a fifty day trip. Consequently, the faster your craft travels, the fewer particles you encounter during your journey.

Comment: Nuclear Freeze Movement (Score 4, Interesting) 181

by rotenberry (#43484231) Attached to: Interviews: Ask Freeman Dyson What You Will

Professor Dyson

I had the pleasure of listening to you speak at Caltech in the 1980s about the Nuclear Freeze Movement. You were a supporter even though you indicated that since the number of nuclear weapons was decreasing (at that time), keeping the current number of nuclear weapons was not desirable.

Thirty years have passed. Do you think this movement accomplished any of their goals?

Thank you.

Comment: Re:Oral exams? (Score 2) 264

by rotenberry (#42772815) Attached to: Dozens Suspended In Harvard University Cheat Scandal

You wonder why oral exams are not more common?

There were 279 students enrolled in this class. Assuming a ten minute oral exam for each and two minutes to grade the answers it takes 55.8 hours to examine all the students. This oral exam would take at least two weeks in a 14 week semester, and ten minutes is really too little time to judge the work of an entire semester.

If anyone other than the professor grades the student, then they cry foul.

If the exams begin in the fifth week of the 14 week semester, the students examined last cry foul since they must study significantly more material.

There should be only twenty students in a class? Good luck with that. I suppose you could raise tuition and hire more professors or have the classes taught by lecturers.

Actually, in the USA most classes are taught by lecturers, and the classes are still huge.

Comment: Re:Krantz's book, "Failure is not an Option" (Score 2) 38

by rotenberry (#41857691) Attached to: Behind the Scenes At NASA's Mission Control Center

"Failure is not an Option" is a good book, but Christopher C. Kraft's book "Flight" covers many of the same events better. I closely followed the Mercury, Gemini, and Apollo missions at the time they occurred and find Kraft's discussion of the engineering problems and solutions clearer, and he is not afraid to be critical of men (like John Glenn) when he believes they were wrong.

Kraft also originated the concept of the Mission Control Center.

Comment: The Sand-Reckoner (Score 1) 278

by rotenberry (#41758541) Attached to: Ask Slashdot: Mathematical Fiction?

I enjoyed "The Sand Reckoner", Gillian Bradshaw's fictional account of Archimedes. (I also enjoyed the original "Sand Reckoner" by Archimedes, but that was not fiction.)

Gillian Bradshaw is a well regarded historical novelist, and there is mathematical content in the novel if you know what to look for. In the book Archimedes' father dies, and Archimedes distracts by working on his mathematics. The reader does not know what he is working on until he tells his sister "It's more than ten seventy-firsts and less than a seventh." Pi minus three, of course.

However, if you are familiar with his proof, the suggestion that he could work this out in a single evening suggests that this is a fantasy rather than a historical novel.

A good read, in either case.

There's no such thing as a free lunch. -- Milton Friendman

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