eufisica

Reasons for the seasons - Rebecca Kaplan

noreply@blogger.com (José Gonçalves) — Thu, 23 May 2013 13:13:00 PDT

Elliptical Earth orbit

Compared to axial tilt, other factors contribute little to seasonal temperature changes. The seasons are not the result of the variation in Earth’s distance to the sun because of its elliptical orbit. Orbital eccentricity can influence temperatures, but on Earth, this effect is small and is more than counteracted by other factors; research shows that the Earth as a whole is actually slightly warmer when farther from the sun. This is because the northern hemisphere has more land than the southern, and land warms more readily than sea.

Seasonal weather differences between hemispheres are further caused by the elliptical orbit of Earth. Earth reaches perihelion (the point in its orbit closest to the Sun) in January, and it reaches aphelion (farthest point from the Sun) in July. The effect this has on Earth's seasons is minor (there is only about a 7% increase/decrease in sunlight received). Any noticeably intensification of the southern hemisphere's winters and summers due to Earth's elliptical orbit is mitigated by the abundance of water in the southern hemisphere.

font: wikipedia

How tornadoes are formed

noreply@blogger.com (José Gonçalves) — Tue, 21 May 2013 05:38:00 PDT

Infographic of a tornado. Credit: infothread.info

A tornado is a meteorological phenomenon which is formed by an air column that it turns around at high speed, it is violent and potentially dangerous. The tornadoes can occurs in any place of Earth, with exception to the polar region. However, in the USA, particularly in a region called Tornado Alley, this kind of nature's force has a higher number of events.

Apparently tornadoes are attached to a strong interaction between the mass flow of air upward and downward and cause an intense movement in the center of clouds of super-charged storm cells. These cells usually formed due to the contrast between two large air masses at different pressures and temperatures.

After touch down, a tornado can reach a range between 100 to 1200 meters, moving a length of approximately 30 km.

Formatio of a tornado. Credit: wikimedia

1 - Prior to the development of the storm, a change in wind direction and speed with an increase in the height tendency to create a horizontal rotation in the lower atmosphere. This change in direction and wind speed is called wind shear.
2 - Air ascending from the lower atmosphere enters the storm and the air rotating inclined from the horizontal position to the vertical position change.
3 - Then there is the formation of a rotation area with a length of 4.6 km, which corresponds to nearly entire length of the storm. Most strong and violent storms are formed in these areas of extensive rotation.
4 - The cloud base and its area of rotation are known as wall cloud. This area is generally no rain.
Reference: wikipedia

As I said before, it is in the US were the number of this event s are higher. Despite a decrease in the number of victims, the number of tornadoes has been increasing over the years.

Number of tornados in USA, between 1918 and 2008. Credit: Chuck Doswell

Air cold from North and Warm from South. Font: Oklahoma Climatological Survey. Adaptation: José Gonçalves

This phenomenon occurs in large numbers in the United States due to large cold air masses coming from the north and warm air masses coming from the Gulf of Mexico. As this aisle there are no major natural barriers such as exists in the West, we have a great area where these masses can collide and form the super storm cells and that will become responsible for the emergence of tornadoes.

However, despite the increased number of tornadoes, the number of tornadoes with great destructive power has decreased compared to previous decades.

Tornadoes can be classified regarding their destructive power. This scale is known by the Fujita scale.

In the table we have the scale and its relationship to wind speed, track width, track length and damage.

The maximum value defined so far is F5, where the wind velocity may reach values between the 420 and the 530 km / h. (260 to 329 mph)

Classification	Velocity of winds (km/h)	Base of the tornado (meters)	Track (km)	Damage
F0	65-115	3-20	0-2	Light
F1	115-180	10-100	1-5	Moderated
F2	180-250	50-500	2-20	Strong
F3	250-330	500-1000	5-60	Severe
F4	330-420	1000-2000	10-150	Devastating
F5	420-530	2000-5000	10-500	Massive destruction

Table: Fujita's scale, correlation with another characteristics of the tornados.

In this graph we have the classification of the tornadoes and the number of events since 1950's.

Number of tornadoes and its classification since 1950's. Credit: Harpers-Ferry Weather

The phenomenon in the United States have been monitored in recent years with some concern. This seems to come from the fact that these phenomena are occurring earlier than normal for its season and a very large number.

In the graph there is the anomalous 2008 and 2011. This year could set a new record for the number of tornadoes that occurred in the United States.

Versão portuguesa aqui.

The Higgs Boson and Our Life

noreply@blogger.com (José Gonçalves) — Mon, 13 May 2013 06:02:00 PDT

On July 4th, 2012, the ATLAS and CMS experiments operating at the CERN Large Hadron Collider (LHC) announced the discovery of a new particle compatible with the Higgs boson (hunted for almost 50 years), which is a crucial piece for our understanding of fundamental physics and thus the structure and evolution of the universe. This lecture describes the unprecedented instruments and challenges that have allowed such an accomplishment, the meaning and relevance of this discovery to physics, and the implications to our day to day lives.

Speaker: Dr. Fabiola Gianotti - CERN
Date: April 30, 2013

What happened to antimatter? - Rolf Landua

noreply@blogger.com (José Gonçalves) — Fri, 03 May 2013 13:45:00 PDT

Me and Rolf Landua holding the antimatter container of DaVinci's Code

Do you remember the antimatter bomb in the DaVinci's Code movie?

In my journey at CERN, Rolf Landua gave a lecture about antimatter. Basically the topics in the lecture was this questions: What is it? Where is it create? How can be created? What is the mystery behind it? How can we study it? Can we use it as a energy font or a bomb? Is any antimatter in our daylife?

In particle physics, antimatter is material composed of antiparticles, which have the same mass as particles of ordinary matter but have opposite charge and quantum spin. Antiparticles bind with each other to form antimatter in the same way that normal particles bind to form normal matter. For example, a positron (the antiparticle of the electron, with symbol e+) and an antiproton (symbol p) can form an antihydrogen atom. Furthermore, mixing matter and antimatter can lead to the annihilation of both, in the same way that mixing antiparticles and particles does, thus giving rise to high-energy photons (gamma rays) or other particle–antiparticle pairs. The end result of antimatter meeting matter is a release of energy proportional to the mass as the mass-energy equivalence equation, E=mc² shows.

At this time, the apparent asymmetry of matter and antimatter in the visible universe is one of the greatest unsolved problems in physics.

Antimatter is created in the LHC, and the LHCb is the detector responsible to detect particles in the antiprotons' collisions. The antiprotons' production is achieved with the collisions between protons and nucleus of Iridium, Cupper, and others. The antiprotons are decelerated and keep trapped with a combination of electric and magnetic fields (so it doesn't touch matter). In this way, the resultant material is detected by the detector before the annihilation. That event is one of the biggest mysteries of the Big Bang, and scientist are trying to answer it: the domination of the matter over the antimatter.

FDG is a glucose molecule, with fluorine-18 attached

This antimatter cannot be used as energy or weapon because we need energy to create it. Imagine that we want to produce 0.5 g of antimatter. Well, we need 22 kton (22,000 ton) of TNT (almost the same value of the Hiroshima's bomb), to produce 0.5 g of matter and antimatter. The energy in this process is about 4.5 x 10¹³J. The total energy that we need (because the efficiency is 10^-9 %) will be 4,5 x 10²²J. Even with CERN's discount made by French Electric Company [1 kwh = 3,6 x 10⁶J= 0,1 €], the total cost will be 1 x 10⁸€ and it will be take a billion years to produce and supply this production to CERN.

But, antimatter is used in our body for PET scan detection. The glucose has a fluorine-18 attached that will emit positrons when that molecule travels in our body, and the scanner detects where the positrons go.

The next step that scientist at CERN are trying to develop is to use positrons and antiprotons as therapy in some deceases.

References:

Antimatter - Wikipedia
Having a Pet Scan
Antimatter presentation - Rolf Landua, CERN

TEDxCERN

noreply@blogger.com (José Gonçalves) — Fri, 03 May 2013 07:58:00 PDT

Credit: CERN

Going beyond particle physics, TEDxCERN will provide a stage for the expression of science in multiple dimensions and disciplines, unveiling a world in which physics intersects with other multi-dimensional disciplines and thought. TEDxCERN will take place on 3 May 2013 at CERN, near Geneva, Switzerland, and will be webcast live throughout many of CERN's member institutes.
Go here to watch: http://tedxcern.web.cern.ch/

NASA | SDO: Three Years of Sun in Three Minutes

noreply@blogger.com (José Gonçalves) — Wed, 24 Apr 2013 08:37:00 PDT

Three years of Sun in three minutes

In the three years since it first provided images of the sun in the spring of 2010, NASA's Solar Dynamics Observatory (SDO) has had virtually unbroken coverage of the sun's rise toward solar maximum, the peak of solar activity in its regular 11-year cycle. This video shows those three years of the sun at a pace of two images per day.

SDO's Atmospheric Imaging Assembly (AIA) captures a shot of the sun every 12 seconds in 10 different wavelengths. The images shown here are based on a wavelength of 171 Angstroms, which is in the extreme ultraviolet range and shows solar material at around 600,000 Kelvin. In this wavelength it is easy to see the sun's 25-day rotation as well as how solar activity has increased over three years.

During the course of the video, the sun subtly increases and decreases in apparent size. This is because the distance between the SDO spacecraft and the sun varies over time. The image is, however, remarkably consistent and stable despite the fact that SDO orbits the Earth at 6,876 miles per hour and the Earth orbits the sun at 67,062 miles per hour.

Such stability is crucial for scientists, who use SDO to learn more about our closest star. These images have regularly caught solar flares and coronal mass ejections in the act, types of space weather that can send radiation and solar material toward Earth and interfere with satellites in space. SDO's glimpses into the violent dance on the sun help scientists understand what causes these giant explosions -- with the hopes of some day improving our ability to predict this space weather.

There are several noteworthy events that appear briefly in this video. They include the two partial eclipses of the sun by the moon, two roll maneuvers, the largest flare of this solar cycle, comet Lovejoy, and the transit of Venus. The specific time for each event is listed below, but a sharp-eyed observer may see some while the video is playing.

00:30;24 Partial eclipse by the moon

00:31;16 Roll maneuver

01:11;02 August 9, 2011 X6.9 Flare, currently the largest of this solar cycle

01:28;07 Comet Lovejoy, December 15, 2011

01:42;29 Roll Maneuver

01:51;07 Transit of Venus, June 5, 2012

02:28;13 Partial eclipse by the moon

More information about this video, as well as full HD version of all four wavelengths and print-resolution stills are public domain and can be viewed and downloaded at: http://svs.gsfc.nasa.gov/vis/a010000/...

This video is public domain and can be downloaded.

CREDIT: NASAexplorer channel in Youtube

Max Planck - Born in April 23, 1858

noreply@blogger.com (José Gonçalves) — Tue, 23 Apr 2013 11:22:00 PDT

Max Karl Ernst Ludwig Planck, (April 23, 1858 – October 4, 1947) was a German theoretical physicist who originated quantum theory, which won him the Nobel Prize in Physics in 1918.

Max Planck. Credit: Wikipedia

Planck made many contributions to theoretical physics, but his fame rests primarily on his role as originator of the quantum theory. This theory revolutionized human understanding of atomic and subatomic processes, just as Albert Einstein’s theory of relativity revolutionized the understanding of space and time. Together they constitute the fundamental theories of 20th-century physics. Both have led humanity to revise some of its most cherished philosophical beliefs, and have brought about industrial and military applications that affect many aspects of modern life.

His work on Black Body Radiation was the begging of Quantum Mechanics.

The Planck constant (denoted h, also called Planck's constant) is a physical constant that is the quantum of action in quantum mechanics. The Planck constant was first described as the proportionality constant between the energy (E) of a photon and thefrequency (f) of its associated electromagnetic wave. This relation between the energy and frequency is called the Planck relation: E = h f.

"Blackbody radiation" or "cavity radiation" refers to an object or system which absorbs all radiation incident upon it and re-radiates energy which is characteristic of this radiating system only, not dependent upon the type of radiation which is incident upon it. The radiated energy can be considered to be produced by standing wave or resonant modes of the cavity which is radiating.
From the assumption that the electromagnetic modes in a cavity were quantized in energy with the quantum energy equal to Planck's constant times the frequency, Planck derived a radiation formula. The average energy per "mode" or "quantum" is the energy of the quantum times the probability that it will be occupied:
This average energy times the density of such states, expressed in terms of either frequency or wavelength
gives the energy density , the Planck radiation formula.

Font: HyperPhysics, Wikipedia

Here is a simulation of the Blacbody radiation (PhET)

You can also try this cool simulation from Open Source Physics.

Finally watch this video with a brief History of Quantum Mechanics:

A whole new view of the Horsehead Nebula

noreply@blogger.com (José Gonçalves) — Fri, 19 Apr 2013 07:52:00 PDT

In this episode of the Hubblecast celebrates 23 years of the NASA/ESA Hubble Space Telescope, by unveiling a beautiful and striking new image of the Horsehead nebula.

Dr Joe Liske (aka Dr J) explains the secrets of nebulae, cosmic clouds of gas and dust that have been the subjects of some of Hubble's most striking astronomical images. The Horsehead nebula is one of the most distinctive, and is now shown in a whole new light thanks to a stunning new infrared image — revealing the delicate wisps of gas that are normally hidden by the thick dust that makes up the Horsehead's famous and familiar shape.

More information and download-options:

http://www.spacetelescope.org/videos/...

Credit: ESA/Hubble

How does an atom-smashing particle accelerator work? - Don Lincoln

noreply@blogger.com (José Gonçalves) — Fri, 19 Apr 2013 03:39:00 PDT

Science School, Issue 26

noreply@blogger.com (José Gonçalves) — Tue, 16 Apr 2013 10:45:00 PDT

Science School

Issue 26

Download Issue 26 as PDF [5.3 MB]

Editorial

News from the EIROs

Events

Feature article: how to rescue a leaning tower

Cutting-edge science

Teaching activity

Science education project

Science topics

Editorial

Welcome to the twenty-sixth issue of Science in School

News from the EIROs

Science in space, society and synchrotrons

EIROforum, the publisher of Science in School, reports on the latest news from its eight European inter-governmental research organisations.

Events

Meeting the next generation of scientists: the European Union Contest for Young Scientists

As young scientists from across Europe gathered in Bratislava to exhibit their projects, find out what impressed the jury most.

Forthcoming events

Feature article

Propping up the wall: how to rescue a leaning tower

Civil engineer John Burland talks about the perils and practicalities of supporting some of the world’s most iconic buildings.

Cutting-edge science

Cracking the mystery of how our planet formed

Studying the chemical composition of some of the planet’s oldest rocks has revolutionised our understanding of how our continents formed.

Laying bare our genetic blueprint

What does the majority of our DNA do? Hundreds of scientists have spent years examining these ‘junk’ sequences, which may hold the key to serious diseases – and much more.

Teaching activity

The genetics of obesity: a lab activity

Around 1.5 billion people worldwide are overweight or obese. Are we just eating too much or can we blame our genes? Here’s how to investigate the genetics of obesity in the classroom.

Science education project

Casting light on solar wind: simulating aurorae at school

The aurorae are one of the wonders of the natural world. Using some simple apparatus, they and related phenomena can easily be reproduced in the classroom.

Science topics

Spinal cord injury: do stem cells have the answer?

Spinal cord injury typically causes permanent paralysis and is currently a condition without a cure. Could stem cell therapy provide hope?

A thermometer that goes to 200 million degrees

Measuring the temperature inside a fusion reactor is no easy task. Find out how it’s done – and even simulate it in the classroom.

Life without the Moon: a scientific speculation

Soaring temperatures, a flooded landscape, violent winds…. What would our planet be like without the Moon?

Printer-friendly version

Send by email

via scienceinschool.org

ScienceCasts: A Whiff of Dark Matter on the ISS

noreply@blogger.com (José Gonçalves) — Sat, 13 Apr 2013 09:32:00 PDT

In astronomy and cosmology, dark matter is a type of matter hypothesized to account for a large part of the total mass in the universe. Dark matter cannot be seen directly with telescopes; evidently it neither emits nor absorbs light or other electromagnetic radiation at any significant level. Instead, its existence and properties are inferred from its gravitational effects on visible matter, radiation, and the large-scale structure of the universe. According to the Planck mission team, and based on the standard model of cosmology, the total mass–energy of the universe contains 4.9% ordinary matter, 26.8% dark matter and 68.3% dark energy. Thus, dark matter is estimated to constitute 84.5% of the total matter in the universe.

On 3 April 2013, NASA scientists reported that hints of dark matter may have been detected by the Alpha Magnetic Spectrometer on the International Space Station. According to the scientists, "The first results from the space-borne Alpha Magnetic Spectrometer confirm an unexplained excess of high-energy positrons in Earth-bound cosmic rays."

font: wikipedia

To know more about dark matter and dark energy follow this link: http://home.web.cern.ch/about/physics/dark-matter

CERN press release:

Geneva 3 April 2013. The international team running the Alpha Magnetic Spectrometer (AMS) today announced the first results in its search for dark matter. The results, presented by AMS spokesperson Professor Samuel Ting (...). They report the observation of an excess of positrons in the cosmic ray flux.

The AMS results are based on some 25 billion recorded events, including 400,000 positrons with energies between 0.5 GeV and 350 GeV, recorded over a year and a half. This represents the largest collection of antimatter particles recorded in space. The positron fraction increases from 10 GeV to 250 GeV, with the data showing the slope of the increase reducing by an order of magnitude over the range 20-250 GeV. The data also show no significant variation over time, or any preferred incoming direction. These results are consistent with the positrons originating from the annihilation of dark matter particles in space, but not yet sufficiently conclusive to rule out other explanations. [...]

Curiosity Rover Report (April 12, 2013): Mars' Bygone Atmosphere

noreply@blogger.com (José Gonçalves) — Sat, 13 Apr 2013 09:17:00 PDT

Credit: NASA

Here is the latest news about the Curiosity Rover:

Remaining Martian Atmosphere Still Dynamic

Mars has lost much of its original atmosphere, but what's left remains quite active, recent findings from NASA's Mars rover Curiosity indicate. Rover ...

› Read More

Curiosity Resumes Science Investigations

NASA's Mars rover Curiosity has resumed science investigations after recovery from a computer glitch that prompted the engineers to switch the rover ...

› Read More

Curiosity Mars Rover Sees Trend in Water Presence

NASA's Mars rover Curiosity has seen evidence of water-bearing minerals in rocks near where it had already found clay minerals inside a drilled rock.

› Read More

Physics and Economy in Europe

noreply@blogger.com (José Gonçalves) — Fri, 29 Mar 2013 12:06:00 PDT

Image from: www.robertgraboyes.com

In 2012, the EPS commissioned an independent economic analysis to the CEBR about the importance of physics to the economies of Europe. The report, using statistical data available in the public domain through Eurostat, covers 29 European countries - the EU27 countries plus Norway and Switzerland. The analysis covers the period of 4 years from 2007 to 2010, where 2010 is the latest year for which official data are available simultaneously to all these countries.

Basically the results point to the following conclusions:

- In 2010, the physics-based industries have generated a return of 3.8 trillion euros in turnover, representing over 15% of turnover. The return per person employed has a turnover substantially higher than the construction and retail.

- The European physics-based sector is highly intensive in terms of research and development (R & D). The spending on R & D sector exceeded 47 billion euros each year during the period 2007-2010. The levels of investment in R & D in 2010 exceeded those of the year 2007.

- In 2010, the physics-based industries employed 15.4 million people. This figure represents 13% of total employment in the business economy of Europe. Moreover, for every job created in industries directly related to the basic physics, a total of 2.73 jobs were created as a support, throughout the economy, by these industries (secondary market).

- Another study in detail was the Gross Value Added (GVA). This GAV measures the value produced by a sector of the economy. Based on physics, the GVA is diverse, where 44.9% are from manufacturing, over 50% is spread between information and communication, professional, scientific and technical activities of oil and gas, and power generation.

In resume, physics has contributed to the development of Europe, this sector is one of the major in the exportation area. Physics develops multiple areas, ranging from electrical repair, through the development of electronic components, until the nuclear fuel processing (among others).

Physics is not only important in the development of the personal welfare of citizens, but as well as in the development of their own industrial and economic of any country.

You can read all the report: here.

Egg Collider

noreply@blogger.com (José Gonçalves) — Fri, 29 Mar 2013 09:10:00 PDT

Happy Easter to all.
See you Monday with more Physics.

LHC Consolidations

noreply@blogger.com (José Gonçalves) — Thu, 28 Mar 2013 09:16:00 PDT

LHC had stopped its work to made an updated to operate a higher energy.
Here is the main consolidations (credit CERN).

Universe by Planck's satellite

noreply@blogger.com (José Gonçalves) — Thu, 28 Mar 2013 09:06:00 PDT

ESA's Planck satellite has delivered its first all-sky image of the Cosmic Microwave Background (CMB), bringing with it new challenges about our understanding of the origin and evolution of the cosmos. The image has provided the most precise picture of the early Universe so far. Read more.

World's Roundest Object! Redefining The Kilogram

noreply@blogger.com (José Gonçalves) — Mon, 25 Mar 2013 08:36:00 PDT

Difference between mass and weight. Font: eschooltoday

The kilogram (SI symbol: kg), is the base unit of mass in the International System of Units and is defined as being equal to the mass of the International Prototype of the Kilogram (IPK).

The gram was originally defined in 1795 as the mass of one cubic centimeter of water at 4°C, making the kilogram equal to the mass of one liter of water. The prototype kilogram, manufactured in 1799 and from which the current kilogram is based has a mass equal to the mass of 1.000025 liters of water.

The kilogram is the only SI base unit with an SI prefix ("kilo", symbol "k") as part of its name. It is also the only SI unit that is still directly defined by an artifact rather than a fundamental physical property that can be reproduced in different laboratories. Four of the seven base units in the SI system are defined relative to the kilogram so its stability is important.

The International Prototype Kilogram was commissioned by the General Conference on Weights and Measures (CGPM) under the authority of the Metre Convention (1875), and is in the custody of the International Bureau for Weights and Measures (BIPM) who hold it on behalf of the CGPM. After the International Prototype Kilogram had been found to vary in mass over time, the International Committee for Weights and Measures (CIPM) recommended in 2005 that the kilogram be redefined in terms of a fundamental constant of nature. At its 2011 meeting, the General Conference on Weights and Measures (CGPM) agreed in principle that the kilogram should be redefined in terms of the Planck constant, but deferred a final decision until its next meeting, scheduled for 2014.

The International Prototype Kilogram (IPK) is rarely used or handled. Copies of the IPK kept by national metrology laboratories around the world were compared with the IPK in 1889, 1948, and 1989 to provide traceability of measurements of mass anywhere in the world back to the IPK.

font: wikipedia

You can read this interesting post about mass.

Build an Electric Buzzer

noreply@blogger.com (José Gonçalves) — Thu, 07 Mar 2013 01:28:00 PST

In my previous post, I write about how to make an electric motor. Today it's time to build an electric buzzer:

"An electronic buzzer is one of the first electronic projects that you'll typically build. The simplest variation consists of a circuit with a battery, buzzer and switch. The buzzer sounds when you close the circuit and stops when you open the circuit. This is an ideal first project because it's simple, produces a verifiable result and is safe because it doesn't require a large current. It can be completed primarily with common household items and requires only a few special purchases."

Read more: How to Build a Buzzer for a Science Project | eHow.com http://www.ehow.com/how_5305594_build-buzzer-science-project.html#ixzz2MqMQ6Jln

In miniscience.com website you can find the description to create this project.
This is a photo of the project:

Follow this steps:

Prepare the materials. Scotch tape, 3v cell battery, 5v electric buzzer, scissors, and wire snips.

Remove the shrink wrap from the buzzer. The shrink wrap is made of polymer plastic film. It shrinks tightly over the buzzer when the shrink wrap is heated. You need to remove this from the buzzer.

Use the wire snips. You need to use the wire snips when snipping the wires from the buzzer. Snip the wires about an inch from outside the base of the buzzer.Position the buzzer. After you are done snipping the wires and removing all the excess wires from the buzzer, you need to set the buzzer upside down. This is the correct position for the buzzer.

Put the battery in place. The battery needs to be placed where the wires were previously located. You need to make sure that the positive and negative ends of your battery are in line with the positive and negative sides of your buzzer.

Hold the materials in place. You can use the scotch tape to hold everything. This is to secure it in place and make sure that none of what you just assembled will move.

By following these simple steps, you can experiment at home and make your own loud electric buzzer. You can in fact use old used materials that may be available in your house. This way, you don’t need to spend much on the materials.

Adapted from: howtodothings.com

How Big is the Universe?

noreply@blogger.com (José Gonçalves) — Mon, 25 Feb 2013 13:07:00 PST

"No one knows if the universe is infinitely large, or even if ours is the only universe there is."
Read the document from Harvard website.

Throughout history, humans have used a variety of techniques and methods to help them answer the questions 'How far?' and 'How big?' Generations of explorers have looked deeper and deeper into the vast expanse of the universe. And the journey continues today, as new methods are used, and new discoveries are made.

It was knowing this fundamental distance from the Earth to the Sun that helped us find the true scale of the entire Solar system for the first time.

When we leave the solar system, we find our star and its planets are just one small part of the Milky Way galaxy. The Milky Way is a huge city of stars, so big that even at the speed of light, it would take 100,000 years to travel across it.

The further away a star is, the fainter it looks. Astronomers use this as a clue to figure out the distance to stars that are very far away.

Beyond our own galaxy lies a vast expanse of galaxies. The deeper we see into space, the more galaxies we discover. We see them not as they are today, but as they looked long before there was any life on Earth.

Finding the distance to these very distant galaxies is challenging, but astronomers can do so by watching for incredibly bright exploding stars called supernovae. Some types of exploding stars have a known brightness so we can figure out how far they are by measuring how bright they appear to us, and therefore how far away it is to their home galaxy.

Adapted from NASA website

Solar cell efficiency goal

noreply@blogger.com (José Gonçalves) — Fri, 22 Feb 2013 11:04:00 PST

Image from: http://www.observatorynano.eu/project/document/2016/

The efficiency of solar cells with multijunction concentrators is increasing since 1988. In the image we can see a great development of the Three-junction solar cell.

Now, scientist has designed a new multijunction solar cell, with am efficiency of 51.8 %.

(Phys.org)—Scientists have designed a new multijunction solar cell that, in simulations, can achieve an efficiency of 51.8%. This high performance exceeds the current goal of 50% efficiency in multijunction solar cell research as well as the current world record of 43.5% for a 3-junction solar cell.

AC vs DC

noreply@blogger.com (José Gonçalves) — Tue, 05 Feb 2013 02:54:00 PST

In alternating current (AC, also ac), the flow of electric charge periodically reverses direction. In direct current (DC, also dc), the flow of electric charge is only in one direction.

The abbreviations AC and DC are often used to mean simply alternating and direct, as when they modify current or voltage.

AC is the form in which electric power is delivered to businesses and residences. The usual waveform of an AC power circuit is a sine wave. In certain applications, different waveforms are used, such as triangular or square waves. Audio and radio signals carried on electrical wires are also examples of alternating current. In these applications, an important goal is often the recovery of information encoded (or modulated) onto the AC signal.

Direct Current (DC) and Alternating Current (AC).
Credit: Physics4Kids

Direct current (DC) is the unidirectional flow of electric charge. Direct current is produced by sources such as batteries,thermocouples, solar cells, and commutator-type electric machines of the dynamo type. Direct current may flow in a conductor such as a wire, but can also flow through semiconductors, insulators, or even through a vacuum as in electron or ion beams. The electric current flows in a constant direction, distinguishing it from alternating current (AC).

Direct current may be obtained from an alternating current supply by use of a current-switching arrangement called a rectifier, which contains electronic elements (usually) or electromechanical elements (historically) that allow current to flow only in one direction. Direct current may be made into alternating current with an inverter or a motor-generator set.

The first commercial electric power transmission (developed by Thomas Edison in the late nineteenth century) used direct current. Because of the significant advantages of alternating current over direct current in transforming and transmission, electric power distribution is nearly all alternating current today. In the mid 1950s, HVDC transmission was developed, and is now an option instead of long-distance high voltage alternating current systems. For applications requiring direct current, such as third rail power systems, alternating current is distributed to a substation, which utilizes a rectifier to convert the power to direct current. See War of Currents.

Direct current is used to charge batteries, and in nearly all electronic systems, as the power supply. Very large quantities of direct-current power are used in production of aluminum and other electrochemical processes. Direct current is used for some railway propulsion, especially in urban areas. High-voltage direct current is used to transmit large amounts of power from remote generation sites or to interconnect alternating current power grids.

from Wikipedia (AC and DC)

Another interesting page: Electric Current in Physics4Kids

Immovable Object vs. Unstoppable Force - Which Wins?

noreply@blogger.com (José Gonçalves) — Thu, 31 Jan 2013 11:00:00 PST

How to Make a Simplest Motor

noreply@blogger.com (José Gonçalves) — Wed, 30 Jan 2013 05:07:00 PST

An electric motor is an electromechanical device that converts electrical energy into mechanical energy.

Most electric motors operate through the interaction of magnetic fields and current-carrying conductors to generate force. The reverse process, producing electrical energy from mechanical energy, is done by generators such as an alternator or a dynamo; some electric motors can also be used as generators, for example, a traction motor on a vehicle may perform both tasks. Electric motors and generators are commonly referred to as electric machines. (Wikipedia)

Do you want to build one? You can learn how to. Just read this paper.
You can find more information about electric motors here.

How to Win a Bike Race: Using Gears

noreply@blogger.com (José Gonçalves) — Wed, 09 Jan 2013 04:41:00 PST

If you want to read more about the Physics of Bikes, follow this links:

Physics of Bicycles

Bicycle and motorcycle dynamics is the science of the motion of bicycles and motorcycles and their components, due to the forces acting on them. Dynamics is a branch of classical mechanics, which in turn is a branch of physics. Bike motions of interest include balancing, steering, braking, accelerating, suspension activation, and vibration. The study of these motions began in the late 19th century and continues today.

Physics and Bicycling, with papers and calculus made with MathCad.

Berkeley University paper.

Links for 2013-01-07 [del.icio.us]

Tue, 08 Jan 2013 00:00:00 PST

Flying, Rolling Robot Might Make a Great Titan Explorer
researchers have been dreaming up ways to explore further Read more: http://www.universetoday.com/99290/flying-rolling-robot-might-make-a-great-titan-explorer/#ixzz2HIcvSy8j
Negative Absolute Temperature for Motional Degrees of Freedom
Absolute temperature, the fundamental temperature scale in thermodynamics, is usually bound to be positive. Under special conditions, however, negative temperatures - where high-energy states are more occupied than low-energy states - are also possible. So far, such states have been demonstrated in localized systems with finite, discrete spectra. Here, we were able to prepare a negative temperature state for motional degrees of freedom. By tailoring the Bose-Hubbard Hamiltonian we created an attractively interacting ensemble of ultracold bosons at negative temperature that is stable against collapse for arbitrary atom numbers. The quasi-momentum distribution develops sharp peaks at the upper band edge, revealing thermal equilibrium and bosonic coherence over several lattice sites. Negative temperatures imply negative pressures and open up new parameter regimes for cold atoms, enabling fundamentally new many-body states and counterintuitive effects such as Carnot engines above unity eff
[1212.6265] Holographic Constraints on a Vector Boson
RT @BlackPhysicists: Holographic Constraints on a Vector Boson. (arXiv:1212.6265v1 [hep-th]) http://t.co/ffjos9lZ #physics

Down of absolute zero!

noreply@blogger.com (José Gonçalves) — Mon, 07 Jan 2013 12:48:00 PST

My friend Andrew Jones wrote a great article about the recent publication of going down absolute zero:

"Temperature has long been understood as a measurement of the average energy of a set of atoms, with the absolute zero temperature representing a system in which the particles no longer have any kinetic energy at all, having ceased all movement. For this reason, while we frequently talk about negative temperatures in the Celsius and Fahrenheit scales, the idea of a negative temperature on the Kelvin temperature scale was believed to be a nonsensical concept. After all, you can't have less motion than none, can you?

Well, new research may have found a way around that."

Read entire article and papers here.

According with the NewScientist:

Credit: NewScientist

"Negative-temperature systems have the opposite behaviour. Adding energy reduces their disorder. But they are not cold in the conventional sense that heat will flow into them from systems at positive temperatures. In fact, systems with negative absolute temperatures contain more atoms in high-energy states than is possible even at the hottest positive temperatures, so heat should always flow from them to systems above zero kelvin."

and

"This has already been done in experiments in which atomic nuclei were placed in a magnetic field, where they act like tiny bar magnets and line up with the field. The field was then suddenly reversed, leaving the nuclei briefly aligned opposite to the direction in which they would have the lowest energy. While they were in this state they fleetingly behaved in a way consistent with them having negative absolute temperatures, before they too flipped over to line up with the field."

Read entire article here.

It seems a new rise for technology:

"Moving into the sub-absolute zero realm, matter begins to display odd properties. Clouds of atoms drift upwards instead of down, while the atomic matrix’s ability to resist collapsing in on itself echoes the forces causing the universe to expand outwards rather than contracting under the influence of gravity.

The ability to produce a relatively stable substance at several billionths of a Kelvin below absolute zero will allow physicists to better study and understand this curious state, possibly leading to other innovations."

Read entire article here.

Links for 2013-01-04 [del.icio.us]

Sat, 05 Jan 2013 00:00:00 PST

Are you tweeting from space? MBB
@Cmdr_Hadfield Are you tweeting from space? MBB
Yes, Standard Orbit, Captain. And we're detecting
@WilliamShatner Yes, Standard Orbit, Captain. And we're detecting signs of life on the surface.

Links for 2012-12-03 [del.icio.us]

Tue, 04 Dec 2012 00:00:00 PST

STUDENTS
Ow.ly - image uploaded by @eufisica (José Gonçalves)
This is not Photoshop. It's Physics: http://t.co/CdaopzlO

Links for 2012-12-01 [del.icio.us]

Sun, 02 Dec 2012 00:00:00 PST

Hemispheric Countersense - YouTube
@eufisica Contrasentido Hemisférico: Timelapse: http://t.co/QyJ3RKUz Imagen: http://t.co/fw8vTUfo Saludos!

Links for 2012-11-18 [del.icio.us]

Mon, 19 Nov 2012 00:00:00 PST

High-Res Images of Cities at Night (from ISS) - Yo
High-Res Images of Cities at Night (from ISS) - YouTube http://t.co/uysjmwqC

Links for 2012-11-17 [del.icio.us]

Sun, 18 Nov 2012 00:00:00 PST

NASA - NASA Great Observatories Find Candidate for Most Distant Object in the Universe to Date
Time Machine - Hubble

Links for 2012-11-04 [del.icio.us]

Sun, 04 Nov 2012 23:00:00 PST

Einstein's special relativity beyond the speed of light -- Hill and Cox -- RSPA
We propose here two new transformations between inertial frames that apply for relative velocities greater than the speed of light, and that are complementary to the Lorentz transformation, giving rise to the Einstein special theory of relativity that applies to relative velocities less than the speed of light.
The Nobel Prize in Physics 2012 - Prize Announcement
RT @astroparticle: #Nobel day! Watch it live here... http://t.co/VSgtmv9I - RT @jdgillies - #physics
Bosemon Game | Discover the COSMOS
We need some #Physics #teachers to test our game with their students and give us feedback: http://t.co/vOwJCmig Thanks :)