Consider a pendulum clock with a pendulum whose length is made of aluminum. If the average temperature around the clock is
ΔT=5 C° (=5 K) warmer in the summer than in the winter, then how much faster or slower does the clock run in the summer than in the winter?
Solution:

Los microcuásares son sistemas binarios en los que una estrella de neutrones o un agujero negro acreta materia de su compañera y que presentan un chorro relativista transversal al disco de acreción. Por primera vez el telescopio espacial Fermi de rayos gamma ha sido capaz de localizar sin ambigüedad uno de estos chorros de alta energía en un microcuásar, Cygnus X-3, una poderosa fuente binaria de rayos-X. Se trata de una emisión variable cuyo análisis detallado permitirá conocer mejor la dinámica y formación de estos chorros relativistas en discos de acreción. El artículo técnico es A. A. Abdo et al. (The Fermi LAT Collaboration), “Modulated High-Energy Gamma-Ray Emission from the Microquasar Cygnus X-3,” Science Express, Published Online November 26, 2009. Este artículo coincide esta semana con otro que proclama prácticamente el mismo descubrimiento pero realizado por el satélite de la Agencia Espacial Italiana AGILE (Astro-rivelatore Gamma ad Immagini Leggero) que estudia con detalle las emisiones de rayos X de la región Cygnus. M. Tavani et al., “Extreme particle acceleration in the microquasar Cygnus X-3,” Nature, Advance online publication 22 November 2009 [disponible gratis en ArXiv].

Cygnus X-3 (Cyg X-3) es una poderosa fuente binaria de rayos X en la que un objeto compacto entre 10 y 20 masas solares orbita una estrella de tipo Wolf–Rayet. El objeto compacto podría ser una estrella de neutrones con un disco de acreción extremadamente masivo o un agujero negro. El espectro de rayos X de Cyg X-3 es inusualmente complejo y muestra hasta 5 estados claramente diferenciados de emisión. Este espectro es mucho más complejo que el del microcuásar más famoso, Cygnus X-1, que no presenta emisión de rayos gamma de alta energía (GeV). El artículo en Nature afirma que la diferencia entre ambos es la existencia de un mecanismo de aceleración de partículas  que periódicamente produce emisiones miles de veces más energéticas que las emisiones que se observan en su estado de reposo.

Los dos estudios publicados esta semana en Nature y Science se complementan mutuamente. El trabajo de la colaboración Fermi demostrando unívocamente que la emisión de rayos X de alta energía tiene a Cyg X-3 como fuente es importante porque está separado sólo por 30 arcmin. de un púlsar muy brillante PSR J2032+4127. Los investigadores han evitado el efecto de dicho púlsar tomando datos de Cyg X-3 sólo cuando su emisión es mínima, lo que reduce a sólo el 20% el tiempo de exposición del Telescopio de Gran Apertura (LAT) de Fermi. Además, se ha requerido de un análisis estadístico de los datos muy cuidadoso pero evitar toda posible ambigüedad.

En resumen, dos trabajos que nos permitirán confrontar mejor los resultados de los modelos de simulación de microcuásares con los resultados experimentales que tanto Fermi como AGILE están obteniendo de Cygnus X-3.

Interesting.
Story:
The universe is full of weird substances like liquid metal and whatever preservative keeps Larry King alive. But mankind isn’t happy to accept the weirdness of nature when we can create our own abominations of science that, due to the miracle of technology, spit in nature’s face and call it retarded.

That’s why we came up with…
http://www.cracked.com/article_17476_7-man-made-substances-that-laugh-in-face-physics theory.html

Watch this awesome cellphone UI developed by The Astonishing Tribe (TAT).

Read the rest of this entry »

by Hydro033

I’ve been grappling with this idea that I cannot deny, but that I wish was not true. This my startle you, but I don’t believe in free will. I just don’t think it exists, I just don’t see how it can exist. Free will, to me, seems like we have the power to change chemical and physical reactions and bend their outcomes based on our “will.” It doesn’t work like that. You have reactants and products. You have forces and results. We can’t influence these things. Read the rest of this entry »

Example 1: How fast is a trolley moving if it has 180.5J of kinetic energy?

Example 2: A ball rolls off a table and hits the floor at 5m/s. What is the height of the table?

Work, Energy and Power Questions Sheet (with answers)

It so happened that I encountered another group of people advising me on the incorrectness of my beliefs. The conversation began with my assertion that an indoctrination of children was unacceptable. And what follows is as such.

Ali: Children should be allowed to explore all the possible options, and be free to choose what they want to believe.

Mr. X: So do you think knowledge is more important or belief?

Ali: Knowledge. It is entirely possible to believe in completely incorrect things.

Mr. X: But human knowledge is limited and can be corrupted.

Ali: Granted, but knowledge does not make the kind of absolutist claims that belief does.

This was the precursor to a conversation that was to take place a week later. People in my religion classes refer to me as “The Troublemaker”, owing to that title being bestowed upon me by a certain Professor. (He was generally very amused with me in his classes. Only sometimes irritated). So the conversation, this time with two more gentlemen, Mr. Y and Mr. Z, was a little more entertaining.

Mr. Z: I have to ask you this. Do you know about Stephen Hawking?

Ali: Yes. I do.

Mr. Z: Do you know he believes in God?

This is generally very aggravating. When imminent scientists, thinkers, philosophers, have their words and ideas misconstrued by ignorant people. Hawking, Einstein, Kant, their conception of a God is NOTHING like the kind that most religious people believe in. I proceeded to shatter Mr. Z’s misconceptions about Hawking’s beliefs (To my great fortune, I am at this time reading A Brief History of Time and The Greatest Show on Earth – available at fine bookstores everywhere). It was followed later by the incredibly ignorant statement

Mr. Y: Do you know that many scientists don’t agree with the Theory of Evolution. And it has been disproven.

Once again, I proceeded to shatter that misconception. And let me make it clear here as well.

THERE IS ALMOST UNANIMOUS AGREEMENT AMONG SCIENTISTS THAT THE THEORY OF EVOLUTION IS THE CORRECT MODEL FOR ALL BIOLOGICAL DEVELOPMENT.

There may be disagreement between various specifics (is it gradual, or step-wise, the relative importance of random mutation to natural selection, etc.) but almost all agree that the theory of evolution is supported by all the evidence and is the correct model. I really don’t understand why people think it isn’t so. And then they say “oh but its not as certain as the Theory of Gravity”. Actually, thats an even more uninformed statement. There is no one Theory of Gravity. Simply because gravity is one of the most difficult concepts to understand; Newtonian force, or in General Relativity a result of the warping of space-time, or the various interpretations from gravitons to multi-dimensional vector, etc. There are numerous interpretations, each one applicable to certain models, unlike evolution which is a single theory applied to every natural model.

And then followed what I consider to be possibly the worst argument of belief:

Mr. Z: Suppose something terrible happens to you ….

Ali: Stop right there. Do not play the “if something awful happens, ergo belief” argument. It is a worthless argument. Just because terrible things happen does not mean I should believe anything at all. Except that they happen. Do you not agree, Mr. Y?

Mr. Y: Well, no I don’t agree with you. But yes, it is a rather weak argument.

If you’ll notice, this is how the religious agree with you. They state that they disagree, because any sign of agreement would imply defeat. I must be completely wrong, that is what they perceive. (Or I could be jumping to conclusions. This is speculative. But not really, because I was once like that.)

Mr. Y: You’re the Troublemaker, aren’t you. I recognized your voice.

Ali: (laughs) Yes, that is what they call me.

Mr. Z: Yes, but you were a nice guy before.

Ali: (turns to face Mr. Z) What is THAT supposed to mean?

Mr. X and Mr. Y laugh as Mr. Z stumbles to reply.

Now, I must admit, I toy with my opponents when I debate them. I lead them into traps, and use their own statements to do some crit. damage. Quite like Philo, and the Demea and the Cleanthes that I face have little idea that that is what I am doing. Often, they also presume that I have not read the authors that they have, and often they are disappointed. I was recommended to read Frithjof Schuon, a Sufi, because I was from South Asia (I had NO idea what that meant. But I let it slide). However, I have read Schuon, and I find that he merely leads you into a confusing interpretation of reality, which is basically what religious gnosis is.

Now, an interesting bit about gnosis is that as you progress into its argument, the gnostic will generally express something like “all religious are just a way of expressing the Truth of the Reality”, and that one can only find God in that way. Further inquiry will lead to the tanzih or transcendence of God, that God is something beyond any human mind can ever comprehend. We can never know because of the limitations of our mind, of our reason (which for the gnostic is a lower form of knowing). At this point, I bring in Wittgenstein’s hammer

“Whereof one cannot speak, thereof one must be silent.” – Wittgenstein

If the entity is beyond comprehension, or any expression we possess, than there is nothing to say. So anyone who claims any kind of awareness and knowing of any kind about this unimaginable, incomprehensible, entity is either a liar or deluded. And the gnostic is trapped, because it is he who has so arduously established this Absoluteness and now he is bound to either admit that the Absolute is knowable (ergo no longer absolute) or is truly unknowable (ergo we cannot say or do anything about it). Q.E.D

The reason I demolish gnostics in this manner is that they tend to be the most effective at confusing people. They are quite adept at leading you into metaphysical arguments, at the end of which you may find yourself tempted by the romanticism of their beliefs. I assure you that these elegant arguments are very persuasive, but ultimately conceal the more bizarre and irrational practices. The gnostics, the saints, the sufis, the pirs, the fakirs, they all have the most ludicrous stories about them. I was at a time informed that they were absolutely true: that once someone brought the sun closer to the earth to cook some meat, brought back the dead to life, healed entire congregations after which they all became believers, etc.

By the end of it, in my experiences, one of us ends up very aggravated. And it’s never me. Maybe thats why they call me the Troublemaker. I brew trouble in their minds.

Port security, worldwide, has been compromised by a forseeable, and avoidable, mistake.

That humans make mistakes is obvious. Sometimes those mistakes carry little, if any consequences. Sometimes errors can be overwhelming. If there is one current theme in our efforts to achieve nuclear security, it is that we are ”mistake prone.” What comes of these blunders…only time will tell.

Take the example of nuclear material and bomb detectors intended for use at world-wide cargo ports.

Clearly it is wise to develop technology for detecting nuclear devices which can be secreted into the country in shipping containers. It is a colossal mistake, however, to run out of a key ingredient, a raw material essential to the development of such technology, because someone forgot to make sure there was enough helium-3 to make functional the 1,300 to 1,400 machines planned to spot uranium or plutonium.

According to the New York Times on November 23, helium-3 is derived from decayed tritium, which comes from hydrogen bombs. The last time we made tritium was in 1989, when the Berlin Wall fell.  Since then, the available supply of helium-3, which detects neutrons which are given off by plutonium bombs, has diminished. While there are substitutes for the scarce ingredient, none are reported to be as effective or as discriminatory when discerning between nuclear weapons and ordinary things cargo like kitty litter and bananas.

According to the Times report, “The helium-3 problem is another symptom of the decline of nuclear technology.” Why the Department of Homeland Security did not seem to know it could not deploy all of the detection machines because of a limited amount of helium-3 is a mystery. It signals a serious mistake in planning.  According to Representative Brad Miller (D-North Carolina), “I have not heard any explanation of why this was not entirely foreseeable.”

The problem of bombs and nuclear components being ushered in with cargo containers is not new or limited to the U.S. It is a real and present danger across the globe. (See video).

The helium problem is particularly troubling. The miscalculation about how much was available could be catastrophic if a smuggled weapon or nuclear material is actually used because of the lack of detection equipment at American and foreign shipping ports. While there are other technologies to try to prevent a shipping container disaster, this was to be one of the most promising.

Such nuclear negligence takes other forms.

Back in 1998 and again in 2000, the United States and Russia agreed to open up a joint early warning center on formerly Soviet soil to detect and analyze missile launches in an effort to avoid accidental warfare. Delayed by 11 years, the center has still not opened.  However, since the agreement was made, nuclear brinksmanship has morphed into a state of complexity, and continues to do so. There are still old warheads for which there is no accounting, and more terrorist organizations and rouge governments seek nuclear capability.  The Times reported on November 14 that legal issues (like who is responsible for the construction of the center) have held up opening the facility.

Amazing. We are living in the time of North Korean nuclear weapons, Iranian development of nuclear technology and an unstable Pakistani warhead arsenal. Even Myanmar is suspected of wanting “the bomb.”  Al Qaeda seeks the bomb. It is ironic that Russians and Americans can cooperate with the complex International Space Station, but jointly we can’t open a building which might help prevent World War III.

The importance of such an early warning center is crystalized by recalling recent history. According to the International Relations Center in October, 2001, ”U.S. nuclear attack warning systems generated more than 1,150 serious false alarms between 1977 and 1984.” On January 25, 1995, the Russians thought an American missile was headed their way. In the minutes before a retaliation launch was being contemplated, the path of the missile was determined to be non-hostile. Even though told of the launch (designed to probe the Northern Lights), someone forgot to tell Russian rocket commanders. We came close…very close, to the end…because of nuclear negligence.

Yes. We are being too lax…too trusting that things will not go wrong.  What’s most troubling is the fact that both of these examples of malfeasance fit into the “completely avoidable” category. They are examples of  how accidents and incidents are allowed happen, and by then, of course, it is too late. We cannot rely on good luck to avoid nuclear devastation.  Quality control in our efforts to avoid nuclear winter needs to be job one.

The legal definition of  negligence is clear. It is ”the failure to use reasonable care.”  U.S. Courts explain ”Reasonable care is that degree of care which a reasonably careful person would use under like circumstances.  Negligence may consist either in doing something that a reasonably careful person would not do under like circumstances or in failing to do something that a reasonably careful person would do under like circumstances.” Applying these definitions, the helium-3 and early warning center examples shout NEGLIGENCE.

No reasonably careful individual would plan for and develop vital equipment to safeguard our ports that cannot ultimately be widely deployed because of a scarce ingredient. No reasonably prudent person would agree that early warning center is crucial and should be opened, and then just argue about legalities while our enemies seek access to technology, which if used or even threatened, make our other disputes trivial. We don’t just need one joint early warning center. The world could benefit several, jointly hosted by rivals.

Too many Americans think that since the fall of the Soviet Union in 1989, that we are safer, in terms of nuclear security, than during the days of the Cold War.  In fact, we are in a much more perilous situation thanks to the likes of proliferation profiteers and power hungry extremist regimes.

It is telling that the “Doomsday Clock” devised by the Board of Directors of the Bulletin of Atomic Scientists has been just 5 minutes from midnight since 2007, closer than it was during the cold war.  (In 1990 the clock was 10 minutes to midnight). We add to our peril and risk a closer proximity to the fateful midnight hour by the excercise of a culture of nuclear negligence in an era of enhanced risk. Since ICBM’s are no longer the only delivery vehicle, cooperation and planning cannot get caught up in details and tunnel vision.

We cannot afford to get sloppy when it comes to averting present-day nuclear threats, and yet, with the examples of helium-3 and the joint warning center, ”mistake prone“ is our reality.  To err is human, but to commit too much error in these hyper nuclear times may ultimately be inhumane. We must do better.

All countries are at risk with cargo container trucks. Above, China inspects a North Korean freight carrier.