Pepe Blog

5 "must-see at least once in a lifetime" Celestial events

noreply@blogger.com (Giulio Pepe) — Mon, 30 Aug 2010 13:08:00 +0000

1. Aurora

noreply@blogger.com (Giulio Pepe) — Sun, 29 Aug 2010 23:00:00 +0000

Aurorae are one of the most impressive views of a night sky and they are very famous to be an event that not all the skies can host.
They happen in fact around the polar regions, both in the northern and southern hemisphere taking respectively the more common name of northern and southern lights.
The curvy movements and the lightness in which they fly across the sky is a really hypnotizing and fascinating sight that cannot leave even the most heartless apathetic man without a "wow" on his lips.

Physical background:

To be precise, aurorae happen near the magnetic earth poles, that are pretty near (~810km far apart) to the geographic respective poles that we all know. The difference isn't only in the position, but also their effect on our planet, since the geographic poles determine the rotational axis of Earth, while the magnetic poles determine the polarity of the Earth, if viewed as a giant massive magnet. Earth's magnetic field indeed is the cause of these wonderful phenomena.

Apart from helping navigators from getting lost into oceans for centuries and centuries, and nullifying the purpose of doing the "charge-to-mass ratio of electron" experiment, Earth's magnetic field has done and is still doing much more relevant things: saving life from certain death.
What brought life on this planet some time ago, in fact, could destroy life without hesitation using just wind... well a kind of special wind, made of ionized particles. The so-called solar wind is a stream of this highly energetic particles that continually hits the Earth's magnetic field, which, even if deformed by this powerful attack, succeed in protecting the Earth by this harmful radiation... almost.

The only Achilles' heel is found near the magnetic poles, where the charged particles coming from the sun can be trapped between the field lines and fall inevitably towards the Earth.
That particles will have a strange fate encountering the Earth's atmosphere: they will combine with atoms and "form light".
If the unlucky particle encounters nitrogen, this atom will go into an excited "energetic" state emitting blue light and re-emitting red light when unexcited. If it encounters oxygen, it will emit green or brown-red light depending on the amount of energy absorbed and re-emitted.

Result:

The result is pretty famous to everyone and these curtains of light moving through a soft wind amaze a lot of lucky people every night somewhere. Thanks, Nature (not the journal).

Locations:

Around the poles, but can extend also for much wider region. It usually depends on how strong the solar wind is; on some very rare occasions aurorae have been reported in Europe, USA or Australia. Polar lights are common in countries such as Alaska, Canada, Iceland, Lapland (Norway, Sweden, Finland), Russia, Greenland, Antarctic and rarely in New Zealand, Punta Arenas/Tierra del Fuego (Chile, Argentina).

Interesting Links:

Northern Lights seen from the International Space Station
Aurorae on Jupiter

2. Solar Eclipse

noreply@blogger.com (Giulio Pepe) — Sun, 22 Aug 2010 23:00:00 +0000

Solar eclipses are natural phenomenons that occurs when the moon passes between the Earth and the Sun, obscuring the latter.
This event is so strange and unnatural in everyday life so that it can only astonish or amaze all living creatures. Studies have shown that also animals react strangely to solar eclipses. Most of their behavior is driven by the absence of light, in fact, depending on the animal, usually they prepare to sleep.

Physical background:

The word Eclipse refers to an event in witch a body is occulted by another body. Eclipses can happen with any astronomical object, but those more relevant, visible to naked eyes, are the lunar and solar eclipses. In the first one, the Moon is eclipsed by Earth's shadow and in the second the Sun is eclipsed by the Moon's shadow.
The eclipses, then happen when 3 bodies are aligned, perfectly aligned for total eclipses.

Solar Eclipses are divided in different types; the main ones are:

- Partial Solar Eclipse: the most frequent (yearly or more) and the most common, the Sun is not totally obscured by the Moon, because not in line with it.
- Annular Solar Eclipse: similar to the partial one, but the Sun is in line with Moon and Earth. It isn't totally obscured because the shadow created by the moon is smaller and then a "ring of sun" around the moon can be seen.
- Total Solar Eclipse: a very rare event in witch the Sun is totally obscured by the Moon.
So called Hybrid solar eclipses can also happen, where both an annular and a total solar eclipse occur on the same alignment but on different timings.

Thinking about the dynamics of the Moon's motion around the Earth, one could assume that solar eclipses must happen every new moon and must be located somewhere on the equator.
We see different kinds of eclipses all around the world, anyway, and not SO frequently! What's missing, then?
An important fact is missing in this way of thinking: the rotational axis of the Earth is inclined and it revolves around the sun with it axis (almost) unchanged, if not for some millennial motions. Furthermore, the plane of revolution of the Moon around the Earth is not the same as the plane of revolution of the Earth around the Sun, but it is inclined by ~5°. The combination of these factors lead to the formation of different kinds of eclipses in very different places of the Earth, but they can be predicted very accurately, since we know this model.
Partial solar eclipses are seen in the penumbra region and total solar eclipses or annular eclipses in the umbra region. The first (total) occurs when the apparent sizes of the Moon and the Sun are about the same, while the second (annular) when the apparent sizes of the Moon is slightly smaller than the one of the Sun.
The apparent size of a body is the size of astronomical objects as seen from Earth. A very curios and mysterious fact is that Moon's apparent size as seen from Earth is almost equal to that of the Sun (apart from the fact that it slightly changes, because of our satellite's elliptical motion, that constantly changes its distance from Earth) even if their distance is significantly different and also their volume. They pretty much match in our skies though, and I find that seriously amazing. Because of this, during total solar eclipses, we can see our Sun's corona, its outer region formed by very hot gas constantly expelled to form solar winds (important in next blog).

Result:

Eclipses at sunsets are my favorite and the most beautiful. The sky darkens, some stars appears (especially Mercury, during total eclipses) and an unreal atmosphere falls on the Earth for some minutes, with the sun still in the sky. Enjoy the mystic atmosphere.

Locations:

Everywhere on Earth, you just need some luck (a lot, actually since they occur in the same place once every 370 years, on average! 18 months on average, everywhere).
The second link below list the upcoming solar and lunar eclipses, with their location and length. Often trips are organized to go and see them. Don't be patient and think of waiting one in your country, if you have the occasion to catch a trip. Just to inform you, there is only one total eclipse in central Europe for the present century, and it's in 2081!

Interesting Links:

All the types of solar eclipses explained using animations
Past and Future eclipses dates including locations
Ancient Greeks' ingenious machine to predict eclipses
Abstract about the effect of solar eclipses on animals

3. Midnight Sunset

noreply@blogger.com (Giulio Pepe) — Sun, 15 Aug 2010 23:00:00 +0000

The midnight sun is a quite surreal phenomenon that happens in the northern or southern latitudes near the polar region. It is nothing more than having sunlight, with the unusual thing that it is midnight.
What is stunning, though, is that (it depends on the latitude and the season) the sun does not set, but remains still on the horizon before rising again and giving sleepless "nights" to visitors.

Physical background:

The only reason for this phenomenon is found in the geometry of the Earth's orbit around the sun. I'll try to let you visualize what happens since an image could be better than a thousand words.

The Earth has an almost-circular elliptic orbit around the sun.
The Earth rotates about its axis with a period much smaller than the orbital period.
The Earth's axis is tilted from the normal to the ecliptic plane.

These, apart from being the main ingredients that drive our climate, are the cause of the midnight sunset.
Because of the rotation of the Earth, we can make distinction between day and night. Who travels a lot, certainly knows that depending on the latitude the sunrise and the sunset times are really different in different places (and also with changing season in the same place).
This is because the rotational axis of the Earth is tilted: in the summer a bigger portion of the northern hemisphere is enlightened by the sun and there are more hours of daylight. In the particular case of the summer solstice, on 21 June the maximum number of hour of daylight is achieved (it depends on the latitude).
As you can see in the image on the left, in this situation, there is a zone in which the Earth, even if it rotates, is always enlightened from sunlight: the arctic circle zone. This means that the sun never sets, but approaches more or less (again, depending on the latitude) the horizon and then rise up again.
For the unlucky arctic circle zone in the southern hemisphere, on 21 June the sun never rise.

Result:

The result is impressive. Three simple ingredients and some geometry cause a number of different cool effects. I'll list what I think are the best here, all derived just by the geometry of our orbit:

- At the equator, the sun always rise at east and set at west, which is not true for the other latitudes (they oscillate around east on the sunrise and west on the sunset during the year) and there are 12h of sunlight and 12h of night throughout the year.
- At the equator there are no shadows on the equinox (this happens also at other latitudes in the tropical zone with the extremes at the tropics on the solstices)
- On the equinox (equa nox : equal night) the sun rises at east and sets at west for all the latitudes. Furthermore, there are 12h of sunlight and 12h of night and the sun rise and set at the same time for all the latitudes (apart from the poles). Pretty cool day.
- The solstices are the only days when the sun reaches the lowest inclination in its apparent motion.
- The arctic circles are a strange place. Depending on the latitude (the more near the poles, the weirder) the day/night will lose their significance, since the hours of light are very disproportionate. 24h of sunlight at the summer solstice and 24h of night at the winter solstice.
- The poles, anyway, are the weirdest place: day and night will last half-a-year respectively. The sun will rotate in concentric circles toward the horizon, when on the equinox it will rotate in a full circle while setting for a full day. Stunning.

In addition to these events, a huge number of climate phenomena are driven by the three ingredients.

The midnight sunset is one of the most famous and fascinating events caused by Earth's orbit, for its strangeness and because it is seen in many civilized locations around the north arctic circles.

Locations:

In the arctic circle, particularly: Canada, Alaska, Denmark (Greenland), Norway, Sweden, Finland, Russia, and extremities of Iceland.
The dates can vary and strongly depend on the latitude, the more near the pole, the wider the range of dates.

Interesting Links:

Midnight sun in Norway: dates and guide to visit
Very touching photos of the midnight sunset
In case you just need a drink now: the midnight sun cocktail

4. Milky Way

noreply@blogger.com (Giulio Pepe) — Sun, 08 Aug 2010 23:00:00 +0000

A starry sky is always a very relaxing and touching view, and often, if we spend some time to contemplate it, when our eyes are well adapted to darkness, we could spot some steady "white clouds" between the stars.
Fortunately that is no premonition of rain, because those clouds are well beyond the Earth's atmosphere. That is the Milky Way, no less than our galaxy!

Physical background:

Why do we see the galaxy we are in, on our skies?
The answer is in the structure of our galaxy and the position in which we are.

The Milky Way is a barred spiral galaxy, that shows a shape of a flat disk with a bulky galactic center. If you think we are in the center of the galaxy, you're quite wrong, since that is a very dense and active region - basically something you want to stay away from.
Our position in the galaxy is about 26000 light years apart from the center, that is quite reassuring, but also allow us to have some fantastic views of the galactic center including the arms.

What do we see of the Milky Way is also a problem that involves the knowledge of the motion of the solar system through the galaxy.
The Sun is supposed to orbit around the galactic center with a period of revolution of 225-250 million years - then this does not affect the milky way position in few (even thousands) years. The inclination of the ecliptic plane (Earth's orbital plane around the sun) with respect of the galactic plane is supposed to be around 60°, with the Northern hemisphere facing relatively away from the galactic center. This is why the center of the Milky Way (that corresponds to Sagittarius alpha) is best seen from the Southern hemisphere, since in the Northern hemisphere it will be near the horizon on the best times of the year. The other parameter that affects the Milky Way visibility is of course the sun. It is in conjunction with Sagittarius in spring, but this won't stop you to see the outer arm of the galaxy: the Perseus Arm.

Basically the random position and inclination of the solar system with respect to the galactic plane let us see at least part of the Milky Way on every season of the year, but the best ones are Summer (for the galactic center in the Northern hemisphere) or Winter (for the Perseus arm).

Unfortunately there is another problem that increases the difficulty to spot the Milky Way.
Our eyes can only catch the bright light from stars; "gassy" objects like the stunningly colored nebulae, galaxies and our Milky Way as well, require a more sensitive equipment since the light that they emit is dim enough to seem black as pitch to human eyes. On the left it is an image of how the Milky Way may appear to human eyes in excellent conditions.
That is still a quite stunning result: the dark patches are evident in the photo and they correspond to the dense gases that shield the light from the brightest regions of the galaxy. On the other side, the details in the image are quite poor. What if you could improve your brightness sensitivity? What if you could sum up the dim light received from the galaxy? Grab a camera, increase the exposure time and get ready to obtain this:

Result:

...WOW...

... It's worth it, isn't it?

Locations:

In order to have good sights of the Milky Way the first requirement you need is a very dark sky. The city-light is the first enemy: you need to get away from cities as far as possible; trust me it will do only good (in every sense). Moonlight is also to avoid at all costs.
Do not bring with you any telescope (unless you want to have some other observations). You don't need any to see the Milky Way, since it is a diffuse object and spreads over the sky.
Choose a suitable time (night obviously) and season. As explained before, summer and winter are the best choices, even better in the Southern hemisphere if you want to spot the galactic center.

Interesting Links:

Time Lapse video of the rising Milky Way's Galactic Center
Time Lapse video of the Milky Way in the Southern Hemisphere
Stellarium: Great program to emulate night sky

5. Meteor Shower

noreply@blogger.com (Giulio Pepe) — Sun, 01 Aug 2010 23:00:00 +0000

Seeing a falling star is a peculiar event, which rarity let it gain the popular conception of expressing a desire when seeing one. This habit founds more solid roots in the fact that people nowadays spend a very little time looking at a night sky, than on the rarity of the event itself.
Millions of meteoroids are in orbital collision with the Earth every day and we should thank our atmosphere that only a tiny percentage reach the ground with much smaller sizes than the original object. On certain seasons the frequency of falling meteors is so high that the event is called meteor shower. But why the Earth is tormented by these intruders?

Physical background:

As matter of facts, Earth is not a contended target for meteoroids, but the solar system contains a lot of debris, including asteroids, comets and meteoroids. The gravitational field of our planet attracts these object as much as it attracts us. Usually, anyway, the interplanetary debris is just in orbit of collision with the Earth. Meteorites and craters found on other planets confirm the fact that they are all hit by meteoroids as much as Earth, or even more. Basically we live in a dangerous place and our atmosphere help us to survive in it.

Why do shooting stars are bright while the object itself is inactive?
That's part of the reason why most of the meteors don't reach the ground. When they enter the atmosphere, they encounter layers of denser and denser air. A shock-wave from the condensed air in front of the path of the meteor produces a great amount of heat that start disintegrating the falling object; friction finish the job started by the shock wave. The meteor practically burns because of its high velocity contact with air; for the fastest meteors, it is about 40 km/s (we are talking of 144,000 kilometers per hour). That is why it "lights up" until it is destroyed or reaches the ground, producing the well known trail of light.
Meteors typically occur in the high layers of the atmosphere such as the mesosphere (75-100 km) and disintegrate at about 50-75 km, showing their presence for a short time because of their speed.

A meteor shower is usually a predicted phenomenon, since it is caused yearly by debris in orbit around the sun like us. When the orbit is in collision with us, they cause a spectacular afflux of meteors, so dense that it may produce over 1,000 meteors per hour.
It is thought that most of the meteor showers are caused by the debris left from comets in orbit around the sun.

Result:

Since the flux of meteor is parallel, from the Earth perspective, they seem to come from the same point on the sky. Obviously that point moves in the sky with the stars as time passes.

The atmosphere created by a meteor shower is surely one of the most dreaming.

Locations:

The chance of catching a meteor is about 50/50 on day and night, since they start becaming more frequent at noon, when we see the part of the sky the Earth is moving toward and become less frequent after midnight, when the Earth looks away from the travelling region.

Scattered meteors can be observed everywhere, but meteor showers are periodical and can be observed only in specific regions and times . There are many of them, but one of the most famous ones is the Leonids, known for its intense shower, best visible in the Southern hemisphere around the middle of November. The Perseids is a very famous meteor shower in the Northern hemisphere that occur throughout late July and August with an intensity peak around the 13th of August.

Interesting Links:

Calendar with the most important meteor showers
Nice pictures of meteor showers

Semplice metodo per aggirare la censura di Pirate Bay

noreply@blogger.com (Giulio Pepe) — Wed, 31 Mar 2010 12:40:00 +0000

Se usate costantemente client torrent per il condividere files in una p2p, sarete venuti a conoscenza del recente blocco del sito The Pirate Bay in Italia, uno dei più grandi distributori di torrent a livello mondiale.
Quando tentate di accedere a thepiratebay.org vi dovrebbe uscire un "Connessione fallita" o una irritante schermata della Polizia di Bergamo che informa del blocco del sito. Blocco? Io la chiamo censura.

Il sito, anche se ha subito centinaia di accuse riguardo la violazione di copyright da molti paesi, è sempre uscito vincitore dal tribunale, poiché i file .torrent sono solo dei link a file che circolano nelle reti peer to peer. In quanto link, non è illegale distribuirli, ma scaricare il file in questione, se protetto da copyright, lo è.
Non è da nascondere il fatto che la maggior parte dei torrent riguardano files protetti da copyright, ma non per questo tutto il sito deve essere bloccato, dove circolano anche files molto interessanti, soprattutto per utenti come me che usano sistemi operativi UNIX.
Tra questi si possono trovare diverse distribuzioni di Linux, programmi open source, album musicali non protetti da diritti (tipo "In Rainbows" dei Radiohead) o di piccole band che cercano popolarità, film di più di 70 anni fa (sui quali c'è diritto di copia) e soprattutto il più recente scandaloso "ACTA Agreement".
Un prezzo sacrificabile, secondo lo stato italiano. Con questo gesto ci è stato sottratto un piccolo pezzo di libertà di espressione. Possiamo riprendercelo? Sì, e anche legalmente.

Il primo blocco sul sito è stato effettuato a livello di filtro sui DNS. Niente di più semplice di aggirare, basta digitare l'indirizzo IP di thepiratebay invece del link, ed il gioco è fatto.
Tuttavia, recentemente tutti gli IP del sito sono stati bloccati, quindi questo trucco non è più applicabile. Aspettare che il sito cambi IP o ne prenda di nuovi non è conveniente, anche perché non costa niente mettere un IP in più nella censura.
Un trucco è quello di usare un' intermediario, che si trova in un altro paese dal quale si può accedere, e fargli fare il compito di connettersi al sito, inviandoci i dati al nostro pc. Questo intermediario si chiama proxy.
Un'altra soluzione è quella di criptare i pacchetti, nascondendo i siti ai quali ci stiamo connettendo, quindi non facendo sapere che stiamo accedendo a thepiratebay: una rete vpn.

In questo post vi consiglierò un programmino tanto semplice quanto efficace che vi provvederà gratuitamente una rete vpn a tutti gli effetti: AnchorFree Hotspot Shield.
Scaricando e installando il programma, vedrete apparire un'icona di uno scudo in rosso nella taskbar. Cliccando col destro e scegliendo "connect", vi connetterete alla rete vpn. Ora vi basta solo accedere a thepiratebay.org e vedrete la rassicurante nave pirata invece del mandato della polizia tributaria di bergamo.
Per disconnettersi dalla vpn basta cliccare di nuovo col tasto destro del mouse sullo scudo (verde stavolta) e scegliere "disconnect".

*UPDATE*
Se non volete installare programmi sul vostro computer e volete un metodo più veloce per accedere senza problemi a thepiratebay, eccovi un ottimo sito proxy gratuito: Anonymouse. Ed eccovi il link diretto per thepiratebay.

Per saperne di più:
The Pirate Bay sarà di nuovo censurata in Italia
Sigillo IP per The Pirate Bay

I haven't been writing for a long time

noreply@blogger.com (Giulio Pepe) — Sat, 27 Mar 2010 11:35:00 +0000

Is that true? Well, no.
It's true that I haven't been writing here, though, but the uni kept me busy with A LOT of writing. Just in case you don't believe it or you want to have a laugh or two reading what the hell I write, here are some things that kept be busy in the last week; you are welcome (but not suggested) to read them:

Mini-Project Summary Report: "Crystal Structure studies using X-rays"
Environmental Physics Essay: "Fusion power: A new hope?"

Enjoy!

Problem with the avahi daemon during the boot

noreply@blogger.com (Giulio Pepe) — Tue, 24 Nov 2009 00:23:00 +0000

A small reminder that I'm still alive plus a problem that almost scared me today (technologically speaking).

My Fedora 11 did me a trick and after an "apparently normal" shutdown yesterday, the avahi daemon failed during the boot hanging it on the login page (background image missing and plenty of error messages about the fail installing the daemon).
There were no ways to log in since after entering the password the laptop would have got stuck in an infinite loading machine. The other terminals (Ctrl+Alt+F2...) worked well, but they were almost useless (if not to backup) to me since I am a beginner.

What I did was then load the live cd and search for help over the internet being prepared to backup and re-install Fedora.
There weren't almost any hint on the web on how to solve this problem, if not for some issues with wireless cards, but nothing similar to my problem that completely blocked me from opening my GUI. I was lost.

Looking at these problems, anyway, enlightened me on how effective is the log system in Linux and the common suggestion to solve problems was, first of all and always, looking at the log in /var/log/messages, that is a record of everything Linux does in background or not.
That's how, after few minutes of searching and reading, that I stumbled upon this line:

Nov 23 09:49:01 acer avahi-daemon[1290]: write(): No space left on device

Nov 23 09:49:01 acer avahi-daemon[1290]: Failed to create PID file: No space left on device

That's even too clear. What seemed a serious problem on some damaged part of my distro was, instead, a problem of carelessly leaving the hard-disk with few bytes not even sufficient to start Gnome.

This is just to prove that sometimes problems that seem too complicate, can be solved just looking at a description of what is going on in the machine, given in detail by the machine itself.
Such an elegant service must not be wasted googleing the problem without mercy but, in most of the cases, "problems" can be solved locally using logs, man pages and your brain.

Hope I've learned the lesson!

Edit: thread found on fedoraforum.org (that is an excellent support forum, anyway) about a similar issue.

Problem with Grsync and (partial) remedy

noreply@blogger.com (Giulio Pepe) — Fri, 02 Oct 2009 00:01:00 +0000

I seize the opportunity of a recent problem with Grsync to talk about it.

Grsync is an useful GUI for the command rsync.
This command is very powerful, since it synchronizes two folders that can be on two different machines, or the same machine. Usually, if on the same machine, rsync is used for backup purposes.
Grsync provides a lot of options to make synchronizations and backups and is really user friendly: it only needs source and destination folders and some options to be set.

The synchronization consists in making the destination folder equal to the source folder.
This is a very common task, since it is common that a folder on a usb stick is used on other PCs and then we want to copy this folder on the PC at home. Copying the entire folder every time will be a slow method, especially if we are handling with gigabytes of data! Copying the files one by one requires a lot of memory and patience. Grsync requires just one click to identify (there are different methods that I will not list, for now) the differences between the two folders and copy only the files different, saving time, memory (human in this case) and cpu.

The usage is very simple: source and destination paths in the relative space and a few options; I'll explain the main ones, but a mouse roll-over the option gives a sufficient explanation of the option:
- Preserve time/owner/permissions/group: the destination files will have respectively the same modification time, the same owner (be careful, this is only a super-user option... in doubt un-tick it), the same permissions on the files (read-write-execute) and the same group.
- Delete on destination: makes a perfect synchronization, since file deleted in the source folder will be deleted also in the destination folder. Essential to have a faithful copy of the source, but to un-tick for incremental backups.
- Verbose: every deleted and copied file, error or message in general will be reported.

The next step is installing it! You can use yum from a terminal:

sudo yum install grsync

or download and compile it from the official website.

---

Now let's focus on the problem: I'll be prompt, Grsync is not working now.
Why?
A conflict (maybe) with the gtk+ update (you don't need to know what gtk+ is, but if you really want... here).
Apparently, the new version of gtk: gtk+2.0-2.16.6 is not letting work grsync 0.9.1. The symptoms are different:
- Grsync window that won't open, but will be silently running in the processes.
- Message error, if grsync is run from terminal:

(grsync:#####): Gtk-CRITICAL **: gtk_combo_box_append_text: assertion `GTK_IS_LIST_STORE (combo_box->priv->model)' failed

repeated for how many grsync sessions are defined.
The problem has been discussed and there isn't still solution as reported here.
I absolutely don't have the solutions for this problem, since my beginner abilities could only help someone to explain or discover new cool programs as in this post.
Anyway, I've got two remedies, until someone find a radical solution to the problem.

The first remedy is pretty lame... but necessary if you want to stick to the program: a downgrade.

If you installed grsync with yum, that's very easy to do:

yum downgrade grsync

and it will downgrade grsync to the older version (0.6.3-2) that is working with the gtk+ update.

The second remedy is much more cool: using directly the rsync command in a terminal.
Rsync has a very easy syntax:

rsync [options] [source] [destination]

and it features a huge number of options. Check out the man pages to know more about this splendid command.
To automatize backups, you can also create a script. This is a BASH example that I use (I'm a BASH beginner too :D):

#!/bin/bash

#

# Syncronize using rsync "src" folder on the PC (source) with the "dest" folder

# on the stick (destination).

#



echo "Starting..."

rsync -vrlpEogth --delete --progress /home/user/src /media/usbstick/dest

exit

I'll introduce BASH and scripts in another post if you're not familiar with that.

That's all for now.

See you soon!

*** UPDATE ***
Thanks to the developer Piero Orsoni, the new version of the program, Grsync 0.9.2, is now full-working.
The version will be soon available also in the repositories.

The Linux Glossary

noreply@blogger.com (Giulio Pepe) — Wed, 30 Sep 2009 00:39:00 +0000

BASH:---
Distribution: ---
Downgrade: the contrary of an upgrade. It is less common than the upgrade, in fact, it could seem silly to go back to an older version of a software, often with more bugs and less features. Yet, in the Linux world, downgrades are often indispensable, if you try new unstable versions of software and you want to pass to older but stable versions or if a new version have conflicts with other programs.
GUI: Graphical User Interface - is a tool that bring a command-based program into the graphic mode, allowing to use the mouse and other visual facilities. Basically, everything we see and click is a GUI that allow the user to interact easily with the core of the program. Easy example: file movements can be made using the terminal (with the mv command) or using a GUI (such as Nautilus file browser) with the easy drag and drop.
Man: it stands for manual, and it is a command that shows the manual page for a specific command including syntax, explanations, options and examples. You will be surprised by how often it will help you understanding some commands!
Open Source: is a software with its source code published and free to be modified, and then, improved. There are a lot of advantages using open source software, since it can be modified and debugged by anyone. This term ought not to be confused with "free". A program can be free (of costs) but closed source and viceversa. Yet, an open source program is often free.
Operative System (OS): ---
Upgrade: an upgrade is the action of updating a program (or even a hardware) to a newer version. This will happen a lot with Linux, since it is in continuous development, especially regarding the software open-source.
Yum: yum is a easy-to-use software packet manager for the terminal (there are some GUIs, though) that allows the user to directly and automatically download, install, and keep up to date programs. The list of programs is kept and updated in the repositories. The convenience of this program consists in having all the programs installed and updated under one manager. Some distributions (such as Fedora) have it installed by default.

*** Post in continuous development ***

Summer Inactivity and possible upcoming project

noreply@blogger.com (Giulio Pepe) — Tue, 29 Sep 2009 17:13:00 +0000

I confess that I haven't quite kept up to date this blog recently, and with recently I refer to the past 2 months.
I've been quite busy in a lot of stuff that can be mainly summed up in:
- Relaxing, swimming, sleeping in Campomarino (Italy)
- Installing, configuring, exploring Linux (Fedora 11)
- Coming in London, settle down here and enjoy the short and sweet last days of unconsciousness before the start-up of that machine that has been almost completely off during the entire summer.

Regarding the second point, I've been thinking about sharing what I've learned (since anything is much educative in the other two points).
I don't want to write the usual annoying posts full of commands that are of no use unless you're particularly searching for them (I'll also write that, sorry, but only when inspired, so I'll try to make them more digestible).
I was thinking about writing a "Linux Beginner Guide" as seen from a complete beginner in Linux but not necessary beginner in the IT world (that is me). That could seem weird at first look, everybody prefers expert teachers, but there are some positive aspects: only a real beginner can understand what are the most common problems for beginners swapping from Windows to Linux. After one full month on this laptop studying, reading and trying over and over, I still consider myself a beginner, but with some knowledge, and this is good, since I can still understand the most difficult parts for a beginner to change an operative system.

My experience from a month of self-learning could be useful particularly to those people that were fluently using Windows and had a discrete experience using a computer except for using programming languages and stuff.
I've never found, indeed, a complete guide for that kind of users, and I know how much is frustrating and difficult to consult thousands of websites about starting using Linux and finding that one is too much technical and the other treats you as a complete newbie. You are surely constraint to use a lot of sources and mix different notions to learn something.
Finding someone with the same level of experience and knowledge as you is very difficult to find, as well as finding someone that like to present a topic in the same way you present it and focusing on the same parts that interest you.
It is obvious that a Linux guru would underline different arguments, compared to a newbie, as well as an intermediate will notice other things and almost everyone of us have a different knowledge of our machine.

I don't want to write a complete beginner guide since the web is full of those guides and they are really satisfying, if you have enough determination (and often time to "lose", that honestly I can guarantee is not lost) to proceed in such a decision.
Don't believe that using Linux is impossible because that's only a "expert only" operative system. There are also a lot of user-friendly versions (called distributions) that made automatic and easy to do a lot of difficult stuff.
My father is using Ubuntu and we all know that more or less our fathers are not the masters using PCs, but still he's quite going good through it.
Then, with this guide, another purpose will be encouraging people (the more, the better) using Linux.

Most of people think: why Linux when I already have Windows and I'm pretty satisfy with it?

Unsurprisingly, that kind of people mostly coincide with that that haven't payed for a Windows License... and are lucky enough to avoid BSODs (maximize to full-display to enjoy).
The short answer is: you'll understand it when you will be using Linux. However, I'll go through this topic, too, in my small guide, and I won't underestimate this argument and the whole preliminary part.

First thing, I will create a post with a kind of glossary. That's because I will not stop on every word used and I think that some self-work at least regarding terminology is useful too. I don't want to make things too easy and I won't surely write all about this world. I believe that the most important part in exploring a new operative systems is when you start reading manual pages and learn things by yourself.

When I will start doing this? That's the major problem.
Nobody's paying me to do this, so I prefer focusing on study now.
Maybe I won't have time until next summer or I will write very slowly... who knows?

In the meantime I'll write general post about news in the Linux world (and obviously not only Linux & PCs in general) when I've got time.

(Aww... Finally I finished this post, bye bye)

Progresso

noreply@blogger.com (Giulio Pepe) — Sun, 23 Aug 2009 13:05:00 +0000

La mente è uno degli strumenti più sofisticati di cui disponiamo, ma non lo prendiamo in considerazione e, con un atteggiamento tipico dei nostri tempi "moderni", facciamo fare alla chimica quel che invece potremmo, almeno in parte, far fare alla mente. La chimica è sempre di più la soluzione di tutto. Si è depressi, si è stanchi, si è sterili, si è magri, si è grassi? C'è sempre una pillola inventata - e messa appunto in vendita - per risolvere il problema. Un bambino è agitato? Non serve andare a capire perché. Il Prozac lo calma sia che all'origine della sua irrequietezza ci siano i genitori divorziati che lo trattano come un pacco postale continuamente rimandato al mittente, sia che la scuola cerchi di far di lui quel che lui non è. Il Prozac viene oggigiorno prodotto in confezioni per l'infanzia e negli Stati Uniti decine di migliaia di bambini dipendono ormai dalla somministrazione quotidiana di questo tranquillante per poter funzionare "normalmente".
Lo stesso avviene col dolore. La sconfitta del dolore è considerata una delle grandi vittorie dell'uomo moderno. Eppure anche questa vittoria non è necessariamente tutta positiva. Innanzitutto il dolore ha una sua importante funzione naturale: quella di allarme. Il dolore segnala che qualcosa non va e in certe situazioni il non avere dolore può essere ancor più penoso dell'averlo. Un orribile aspetto della lebbra è che distrugge i nervi capillari dell'ammalato e quello, non sentendo più alcun dolore, non si accorge quando le sue dita sbattono e si spezzano contro qualcosa o ancora peggio, come avveniva nei lebbrosari dei paesi più poveri, quando le dita gli venivano mangiate dai topi, di notte, mentre dormiva.
E poi: eliminando la sofferenza al suo primo insorgere, l'uomo moderno si nega la possibilità di prendere coscienza del dolore e della straordinaria bellezza del suo contrario: il non-dolore. Perché in tutte le grandi tradizioni religiose il dolore è visto come una cosa naturale, come una parte della vita? C'è forse nel dolore un qualche significato che ci sfugge? che abbiamo dimenticato? Se anche ci fosse, non vogliamo saperne. Siamo condizionati a pensare che il bene deve eliminare il male, che nel mondo deve regnare il positivo, e che l'esistenza non è l'armonia degli opposti.
In questa visione non c'è posto né per la morte, né tanto meno per il dolore. La morte la neghiamo non pensandoci, togliendola dalla nostra quotidianità, relegandola, anche fisicamente, là dove è meno visibile. Col dolore abbiamo fatto anche di meglio: lo abbiamo sconfitto. Abbiamo trovato rimedi per ogni male e abbiamo eliminato dall'esperienza umana anche il più naturale, il più antico dei dolori: quello del parto, sul quale da che mondo è mondo si è fondato l'orgoglio della maternità e l'unicità di quel rapporto forse saldato proprio dalla sofferenza. Ma questa è la nostra civiltà. Ci abituiamo sempre più a risolvere con mezzi esterni i nostri problemi e con ciò perdiamo sempre più i nostri poteri naturali. Ricorriamo alla memoria del computer e perdiamo la nostra. Ingurgitiamo sempre più medicine e con ciò riduciamo la capacità del corpo a produrre le sue.

Tiziano Terzani - Un altro giro di giostra (One More Ride on the Merry-go-round, 2004)

Shower

noreply@blogger.com (Giulio Pepe) — Thu, 20 Aug 2009 14:38:00 +0000

Having a shower is a relaxing moment of the day. Some people sing, others just imagine, but whatever you do, the mind is surely free to think about anything and fly (freely) over a lot of disparate topics, often non-related between each other.

I don't know how, but when I was showering, today, it happened to think about an awesome quotation from Tanenbaum (besides, a Physics doctorate and one of the man that "triggered" Linus Torvalds to write his famous UNIX operative system):

Never underestimate the bandwidth of a station wagon full of tapes hurtling down the highway.

What's so interesting about this expression?
Even if it has been used in 1981 on a different context, its irony could still be up to date, since Sneakernet is a still very common practice and couldn't (still) be easily substituted by virtual data transfers (p2p, ftp...).
I've heard new versions of this quote with "hard disks" instead of "tapes", indeed.

The next step on my train of thoughts - during the shampoo - was the realization that I can calculate the actual bandwidth, a kind of average in kb/s, of a car bringing an hard disk.
How? Dimension analysis, obviously!

The dimensions of velocity are: [Length] / [Time] , so to obtain the dimensions of bandwidth [Data] / [Time] it is just necessary to multiply by the data carried and divide by the distance covered.
The result is a formula for the bandwidth depending on velocity of the car v, the distance travelled l, and the data carried d.
$\usepackage{white}$
$\textcolor{white}{b = \frac{v \cdot d}{l}}$
(if you see incomprehensible signs enveloped by $, Latex script is not working good)

If we pick a car travelling a distance of 1000 km at 130 km/h carrying a Terabyte:

$\textcolor{white}{b = \frac{130}{1000}\,TB/h \sim 133\,GB/h \sim 38\,MB/s}$

Quite satisfying.

This is useful (maybe not) but it's not finished.
If you can calculate the bandwidth of a bunch of data travelling in a car, why don't we calculate the velocity of a bunch of data travelling through the wires knowing the bandwidth?
In this case data should be considered like a solid packet, and d is the distance between the host and the server. After some easy math:

$\textcolor{white}{v = \frac{b \cdot l}{d}}$

Wow, you're still reading... crazy. Anyway, that's not all, not yet:
if you pick a value for d (data) smaller than b (bandwidth), it almost doesn't make any sense and the result could be a velocity higher than the speed of light, indeed.
Since the speed of light is an upper limit:

$\textcolor{white}{v = \frac{b \cdot l}{d} \leq c}$

and so:

$\textcolor{white}{b \leq \frac{d \cdot c}{l}}$

that is the absolute upper limit in bandwidth.
If we put numbers, the result still doesn't make any sense.
For example, since the net works in small packets, for a 64 byte packet from a server 7000 km far, the upper limit speed is about 2.7 kb/s.
This result could be useful if we make a small modification to find the time required to transfer that packet at c (dimension analysis again):

$\textcolor{white}{t = \frac{d}{b} = \frac{64\,byte}{2.7\,kb/s} \sim 0.02\,s}$

That is 20 milliseconds: the lowest time physically possible needed to receive something from a distance of 7000 km.
Real timings are about 150ms for good servers, to send and receive, so about 75ms one way, that is in the limits...

Now I ended the shower and then also this small trip around physics and the internet. The result of this brainstorming thoughts? I really don't know, but I still like it.

100 points for the first who analyse relativistic effects on the packets and find how much kilobytes the file loses travelling at that speeds.

5 Ways 'Common Sense" Lie to You Everyday

noreply@blogger.com (Giulio Pepe) — Wed, 19 Aug 2009 12:00:00 +0000

http://www.cracked.com/article_17142_5-ways-common-sense-lies-you-everyday.html

I find this article quite interesting, because its strange mix of a funny language and an interesting topic make it straightforward to follow, but it doesn't reduce the relevance of the subject discussed.
And it makes think a bit about how can we be weird sometimes, more than we can even realize.

Mankind

noreply@blogger.com (Giulio Pepe) — Sun, 02 Aug 2009 14:20:00 +0000

The very beginning of Genesis tells us that God created man in order to give him dominion over fish and fowl and all creatures. Of course, Genesis was written by a man, not a horse. There is no certainty that God actually did grant man dominion over other creatures. What seems more likely, in fact, is that man invented God to sanctify the dominion that had usurped for himself over the cow and the horse. Yes, the right to kill a deer or a cow is the only thing all of mankind can agree upon, even during the bloodiest of wars.

Milan Kundera - The Unbearable Lightness of Being

Moonset and Jupiter again

noreply@blogger.com (Giulio Pepe) — Fri, 31 Jul 2009 02:00:00 +0000

Same telescope, different situation: waxing moon.
After some time wasted (the temptation to point the telescope to the ground and spy innocent people from the top of my house is unimaginable) I convinced myself to watch the orange setting moon a little nearer (20mm eyepiece):

And after I proved that the gravitational laws are true, thanks to Jupiter's moons, because they have been moved in elliptical motion since the last observation (20mm eyepiece)(mouse rollover to circle the moons):

Stellarium (mouse rollover to name the moons):

I've seen what Galileo saw

noreply@blogger.com (Giulio Pepe) — Wed, 29 Jul 2009 17:33:00 +0000

Clear sky, Tramontana (a Northern wind known to be very dry), new moon, neighbourhood lights off: perfect occasion to dust off my brother's telescope and do some "observations".

A refracting telescope, 10cm objective lens and two 34mm and 20mm eyepieces; not so bad for the Moon and planets.

I tried to spot some stars but they were too faint because of that damn light pollution, so I decided to see one of the most luminous astral bodies in the Northern Sky: Jupiter.
After some focusing, I spotted Jupiter with its prominent lighter-hued zones.
But I also noticed what at first sight I thought were some refractions/reflections. There were smaller dots aligned near Jupiter, with different brightness. They were too strange to be some optical effect, so the second assumption was: the Jupiter's moons!
That dots were quite far from Jupiter, in my opinion, to be its moons so I wasn't so sure about that, but they were four (as the Galilean moons), aligned and with different sizes.
I took a picture with my phone (one of the most difficult things in my life, but I was determined to take it) and the result is a very fuzzy and dirty image. Unfortunately the view through the telescope was much clearer and defined, but it can get the idea across (click on the image to enlarge):

After reversing and some photoshopping (or better "gimping"):

Then I immediately checked with Stellarium what kind of bodies they could be, whether Jovian moons or stars. This is the screenshot:

Fascinating.

Stellarium

noreply@blogger.com (Giulio Pepe) — Tue, 28 Jul 2009 23:30:00 +0000

Exploring the educational section of softwares for Gnome, I stumbled upon this incredible program: Stellarium.

You just enter your location and it simulates the sky over you at that moment. Very useful for amateur astronomers or night sky passionate.

There are also a lot of cool features to make the sky similar to the real sky: you can regulate the magnitude and the light pollution, or you can accelerate or choose the time, you can label costellations, stars or nebulae (so you can learn star's names or costellations), make zooms and a lot more.

Practical, easy to use and interesting.
It is also available for Windows.

Incremental Backup using BATCH commands

noreply@blogger.com (Giulio Pepe) — Sun, 26 Jul 2009 23:10:00 +0000

There is an easy and geek way to make incremental backups in Windows using just the bloc notes and the command-line. There are just a few steps, easy to follow:

Copy this string into a new text file with bloc note or your favourite text editor:

    @echo off

xcopy “C:\Folder 1” “D:\Backup Folder 1” /E /H /R /Y /I /D

xcopy “C:\Folder 2” “D:\Backup Folder 2” /E /H /R /Y /I /D

xcopy “C:\Folder 3” “D:\Backup Folder 3” /E /H /R /Y /I /D


pause

Save it with the .bat extension (it can be done in the bloc notes selecting "All Files" as extension and naming the file such as backup.bat).

It's done!

If you run the file just created, a command-line will open and it will make an incremental backup of Folder 1,2 and 3 (the source folders) into Backup Folder 1,2 and 3 respectively (the destination folders).
You can remove or add more folders to make simultaneous backups.

New files in the source folder will be written in the destination folder, existing files will be kept, updated files will be overwritten, deleted files wont be deleted in the destination folder (from this the name "incremental").

Mozilla Backup

noreply@blogger.com (Giulio Pepe) — Sat, 25 Jul 2009 09:41:00 +0000

Making backups periodically is a very good habit.

Personally I've lost a lot of data thanks to thunderstorms, super-heated HDDs or just random broken hardware, enough to make backup of every single bit of data on my notebook.
Sometimes it's like a curse: if you don't make backups, some thunder will burn your hard-disk... and it happens... regularly.

I find very useful to save settings, especially those on my web and mail browser, that is full of themes, add-ons, feeds, bookmarks and other preferences that I wouldn't really like to lose.
I use Firefox and Thunderbird as internet browser and mail platform and I find them the most customizable and fluent software in that field.

So I'd just like to remind you to make a backup of your settings (yes, don't be lazy, make it now!). The profile folders (that contain almost everything) are located in:

Firefox

Windows XP: %APPDATA%\Mozilla\Firefox\Profiles\xxxxxxxx.default\ (note: %APPDATA% is equivalent to C:\Documents and Settings\[User Name]\Application Data)
Linux: ~/.mozilla/firefox/xxxxxxxx.default/

Thunderbird

Windows XP: %APPDATA%\Thunderbird\Profiles\xxxxxxxx.default\
Linux: ~/.thunderbird/xxxxxxxx.default/

A very good tool to make automatic and scheduled backups in Firefox is the FEBE add-on.

Tunatic (Windows/Mac)

noreply@blogger.com (Giulio Pepe) — Fri, 24 Jul 2009 14:35:00 +0000

Do you hum a tune but don't remember what song is it? You listen every time to some music at TV but don't know the title or it is on the tip of your tongue?

Tunatic is the program that suits you for this kind of problem.
It is a free music identification software and you need just a microphone and an internet connection.

Let Tunatic hear the song from the microphone and it'll identify the title in a matter of seconds (at the best hypotesis).

The program is very light, it just identify music and it isn't weighted with other (often useless) options.

Swap

noreply@blogger.com (Giulio Pepe) — Thu, 23 Jul 2009 01:01:00 +0000

I haven't been writing for a while here, since I've been busy particularly with installing, using (and enjoying) Linux.

I decided to install during the summer the Fedora distribution (a free Red-Hat product) in a dual boot with the intention of using Linux sometimes and keeping Windows as the main OS. I also decided to try Windows 7 RC, so I built 3 partitions and installed each operative systems:

The reaction to Windows 7 was not so exciting as I thought. The user interface is very similar (if not the same) to Vista. It was of course much better than Vista under a lot of aspects, so I was almost convinced to swap from XP to Seven (even if I didn't see so many interesting improvements).
What have really deluded me was the compatibility with hardware and software. A lot of programs were not working under Seven, and this is quite acceptable since it is still a RC. But what made me upset were the ATI drivers for Seven, made only for the newest graphic cards (and not for my ancient but still working Radeon X600).
Without the drivers, the "powerful" Windows 7 didn't even recognize the resolution of my display (1440x900) so I was constrained to use a crappy 800x600.
I deleted the partition with Seven and I decided to try it after some time.

Then I installed Fedora 11. In less than 20 minutes the OS was on the hard drive ready to be used, with all the components installed automatically (and the right display resolution).
There are no accurate words to describe it: flexible, light, fast, user-friendly...
I'm not using Windows from that day.
Maybe one of the few drawbacks is the lack of programs, so I decided to keep Windows for that, but often there are good, if not better, alternatives and there are a lot of more interesting applications.
I can't list the benefits of using Linux here, it is seriously difficult to list them all!

Anyway, I'm not using Windows any more, so I'll write quickly some post about some Windows programs that I planned to write and then I think I'll begin to write IT posts exclusively about the Linux world.

Are you right or left brained?

noreply@blogger.com (Giulio Pepe) — Sun, 21 Jun 2009 10:08:00 +0000

Interesting... After 2.30 the video is modified in order to help changing direction of rotation.
Surprisingly the first time I saw this video, the dancer was rotating clockwise and it took me a bit to let her rotate anti-clockwise.
According to the video description I am supposed to be right brained and then imaginative, religious, impetuous, risk taking and so on..... is that me?

Ok, there are no information about who created this test and that's why I read some material about the sides of the brain and what do real neuroscientists think about the asymmetry of the brain.
The result is that now I am even more confused.

What I have understood is that also scientists are not sure if someone can have a dominant part of the brain. There are a lot of contrasting opinions because human brain is not so simple as it might be thought.

What is sure, is that brain is not merely divided in creative side (right-side) and logic side (left-side). Both sides cooperate when someone is thinking, but one can be used more when doing some specific tasks.
Experiments have been done on people who have damages on one side of the brain or on people who have the corpus callosum surgically cut off (such as to alleviate epilepsy). The corpus callosum is the structure that links right and left side of the brain, so without it, it's like having two separate brains.
It has been discovered that, in general, left brain hosts (for most of right-handed people) most of linguistic skills, and the ability to see details. The general view and the "emotional" side of language are host by the right brain. It is unclear (for me, at least) if someone can have a remarkably dominant side of the brain.

However, even if it is true or not, that is not linked to how much you are creative or logical.
An individual with a certain dominant side of the brain is not necessary inclined to have innate skills in what the dominant side hosts.
We know that there are people more "emotional" and people more "analytic", but it is wrong to consider that the more emotional individual has a right dominant side of the brain and viceversa.
If you are doing maths you are not only using your left brain and if you are doing arts you are not only using your right brain.
Of course, if your right brain disappears you do not become Einstein and if your left one disappears you do not become Picasso.

Hence, it is really stupid to consider smarter who "uses left brain more". You are smart if you are flexible to "change side of you brain" and to use both of them correctly and take the best from both of them.

The question, then, is: is this test really valid?
If I didn't misunderstood anything, I guess that the answer is no.

Maybe the idea of the test is right, but not the result. I'll explain:
we see the dancer rotating but it isn't, actually. The image shown is a 2D image, then if you see it as a plane image changing shape, all the parts of the figure are just oscillating.
If we take legs and arms in a 3D space they can rotate towards us and away from us, but since it is a 2D image, they are just oscillating.
Since our brain recognize the image as a human, it is seen as a 3D object, so our brain gives her a rotation that could be clockwise or anti-clockwise because the original image is not making any rotation. Up to this point the dancer could be considered as a cool optical illusion, and it is true that the way it rotates depends on our brain.

I don't know how, but it could be even true that if you see it rotating clockwise you are "right brained" and if you see it rotating anti-clockwise you are "left brained".
What is surely wrong is to suppose that a "right brained" is a creative person and a "left brained" is a logical person.

Please comment if you know more, or if I made some shameful mistakes!

Main source: New Scientist

Space Geeks

noreply@blogger.com (Giulio Pepe) — Sat, 20 Jun 2009 13:29:00 +0000

Did you know that actor Tom Hanks and director Ron Howard have a deep interest in space missions (especially Apollo) and science?

Then read this interesting interview made by New Scientist.