Dark secrets of the Universe

Dark secrets of the Universe

It’s perhaps natural that we don’t know much about how the Universe was created – after all, we were never there ourselves. But it’s surprising to realise that when it comes to the Universe today, we don’t necessarily have a much better knowledge of what is out there. In fact, astronomers and physicists have found that all we see in the Universe – planets, stars, galaxies – accounts for only a tiny 4% of it! In a way, it is not so much the visible things that define the Universe, but rather the void around them.

Cosmological and astrophysical observations indicate that most of the Universe is made up of invisible substances that do not emit electromagnetic radiation – that is, we cannot detect them directly through telescopes or similar instruments. We detect them only through their gravitational effects, which makes them very difficult to study. These mysterious substances are known as ‘dark matter’ and ‘dark energy’. What they are and what role they played in the evolution of the Universe are a mystery, but within this darkness lie intriguing possibilities of hitherto undiscovered physics beyond the established Standard Model.

Dark matter

Dark matter makes up about 26% of the Universe. The first hint of its existence came in 1933, when astronomical observations and calculations of gravitational effects revealed that there must be more 'stuff' present in the Universe than telescopes could see.

Researchers now believe that the gravitational effect of dark matter makes galaxies spin faster than expected, and that its gravitational field deviates the light of objects behind it. Measurements of these effects show that dark matter exists, and they can be used to estimate the density of dark matter even though we cannot directly observe it.

But what is dark matter? One idea is that it could contain ‘supersymmetric particles’ - hypothesized particles that are partners to those already known in the Standard Model. Experiments at the Large Hadron Collider may be able to find them.

Dark energy

Dark energy makes up approximately 70% of the Universe and appears to be associated with the vacuum in space. It is homogenously distributed throughout the Universe, not only in space but also in time - in other words, its effect is not diluted as the Universe expands.

The even distribution means that dark energy does not have any local gravitational effects, but rather a global effect on the Universe as a whole. This leads to a repulsive force, which tends to accelerate the expansion of the Universe. The rate of expansion and its acceleration can be measured by observations based on the Hubble law. These measurements, together with other scientific data, have confirmed the existence of dark energy and provide an estimate of just how much of this mysterious substance exists.

Recipe for a Universe

Μια ματιά στην κατασκευή του κόσμου.

European Organization for Nuclear Science

Recipe for a Universe

Take a massive explosion to create plenty of stardust and a raging heat. Simmer for an eternity in a background of cosmic microwaves. Let the ingredients congeal and leave to cool and serve cold with cultures of tiny organisms 13.7 billion years later.

To understand the basic ingredients and the ‘cooking conditions’ of the cosmos, from the beginning of time to the present day, particle physicists have to try and reverse-engineer the ‘dish’ of the Universe. Within the complex concoction, cryptic clues hide the instructions for the cosmic recipe.

Slowly simmer

Space, time, matter... everything originated in the Big Bang, an incommensurably huge explosion that happened 13.7 billion years ago. The Universe was then incredibly hot and dense but only a few moments after, as it started to cool down, the conditions were just right to give rise to the building blocks of matter – in particular, the quarks and electrons of which we are all made. A few millionths of a second later, quarks aggregated to produce protons and neutrons, which in turn were bundled into nuclei three minutes later.

Then, as the Universe continued to expand and cool, things began to happen more slowly. It took 380,000 years for the electrons to be trapped in orbits around nuclei, forming the first atoms. These were mainly helium and hydrogen, which are still by far the most abundant elements in the Universe.

Another 1.6 million years later, gravity began to take control as clouds of gas began to form stars and galaxies. Since then heavier atoms, such as carbon, oxygen and iron, of which we are all made, have been continuously ‘cooked’ in the hearts of the stars and stirred in with the rest of the Universe each time a star comes to a spectacular end as a supernova.

The mystery ingredient

So far so good but there is one small detail left out: cosmological and astrophysical observations have now shown that all of the above accounts for only a tiny 4% of the entire Universe. In a way, it is not so much the visible things, such as planets and galaxies, that define the Universe, but rather the void around them!

Most of the Universe is made up of invisible substances known as 'dark matter' (26%) and 'dark energy' (70%). These do not emit electromagnetic radiation, and we detect them only through their gravitational effects. What they are and what role they played in the evolution of the Universe is a mystery, but within this darkness lie intriguing possibilities of hitherto undiscovered physics beyond the established Standard Model.

Link:public.web.cern.ch/Public/en/Science/Recipe-en.html

Site found: www.cern.com

Александр Солженицын (+3 Августа 2008 г.)

Σαν χωρίς να το θυμάμαι πια, ο Αλεξάντρ Σολζενίτσιν έφτιαξε μέρος της ζωής μου στην ηλικία που άρχισα να σπουδάζω και να ψάχνω (απελπισμένα πολλές φορές) να καταλάβω πού βρίσκομαι και αν πουθενά με περιμένει κάτι.

Ο άνθρωπος αυτός στράφηκε και κοίταξε κατάματα ολόκληρο τον ολοκληρωτισμό της Σοβιετικής Ένωσης, και "έπαιξε σημαντικό ρόλο για να τελειώσει ο κομμουνισμός", ένας μόνος απέναντι στην ιστορία μέσα στον 20o αιώνα. Φαντάσου: ένα καγιάκ στη μέση του Ατλαντικού. Δέος ...

Κάπως σα να πέθανε παπούς μου, είμαι ήσυχος και λυπημένος.

Η νεκρολογία είναι του BBC.

A look at the life of Alexander Solzhenitsyn

Alexander Solzhenitsyn, who has died at the age of 89, played a significant role in ending communism. His novels were beautifully crafted, damning indictments of the repressive Soviet regime.

Born into a family of Cossack intellectuals, Alexander Solzhenitsyn graduated in mathematics and physics, but within weeks the Soviet Union was fighting Hitler for its survival.

Solzhenitsyn served as an artillery officer and was decorated for his courage, but in 1945 was denounced for criticising Stalin in a letter.

He spent the next eight years as one of the countless men enduring the gulags. He was one of the lucky ones to survive.

There followed a period of internal exile in Kazakhstan during which Solzhenitsyn was successfully treated for stomach cancer.

Instant celebrity

On his return to European Russia, he was allowed, following Khrushchev's denunciation of Stalin, to publish his largely autobiographical One Day in the Life of Ivan Denisovich, in 1962.

Solzhenitsyn spent eight years in labour camps

This made him an instant celebrity. But with the subsequent fall from power of the reformist Khrushchev, the KGB stepped up its harassment of Solzhenitsyn, forcing him to publish his work abroad.

His novels The First Circle and Cancer Ward were further damning allegories of the Soviet system.

In 1970, he was awarded the Nobel Prize for Literature. But he refused to attend the award ceremony in Stockholm for fear of not being allowed back home.

In 1973, the first of the three volumes of The Gulag Archipelago was published in the West. He had been hiding the novel from the authorities, fearful that people mentioned in it would suffer reprisals.

Branded a traitor

But his former assistant, Elizaveta Voronyanskaya, revealed its location after being interrogated by the KGB after which she hanged herself.

So Solzhenitsyn decided to publish it. The Gulag Archipelago offered a detailed account of the systematic Soviet abuses from 1918 to 1956 in the vast network of prison and labour camps.

He exposed Stalin's tyranny

Its publication led to a violent campaign against Solzhenitsyn in the Soviet press which denounced him as a traitor.

In early 1974, even Solzhenitsyn's world reputation could not prevent his arrest. But rather than put him on trial, the Soviet authorities stripped him of his citizenship and expelled him from the country.

In exile, he continued to be a source of controversy, notably when he issued a series of documents which cast serious doubt on Mikhail Sholokov's authorship of the novel And Quiet Flows the Don.

Many of his utterances were discursive and even baffling, and the admiration for him was not entirely uncritical.

Eventually, he settled in Vermont in the USA with his second wife and their three sons. Here, he completed the other two volumes of The Gulag Archipelago.

Return to Russia

Prussian Nights, a long narrative poem about the Red Army's vengeful advance into East Prussia in 1945, was published in 1977. He was said to have composed the poem and committed it to memory 25 years before, during his years in prison.

But Solzhenitsyn also rejected liberalism, dismissing the notion of democracy introduced by Gorbachev and Yeltsin as a myth. He was equally scathing of Western liberalism.

He returned to Russia in 1994 and told the Russian parliament, the Duma, that post-communist Russians were not living in a democracy.

He denounced politicians as being corrupt, and appeared regularly on television to voice his disapproval of the country which had first reviled and then embraced him.

In 2000, his book, Two Hundred Years Together, again covered sensitive ground in exploring the position of Jews in Soviet society.

He denied some charges of anti-Semitism. Gradually, his own people no longer had quite the desire to listen so carefully to his criticisms.

But former President Vladimir Putin courted his approval towards the end of the author's life, personally visiting his home in 2007 to award him the State Prize of the Russian Federation for his humanitarian work.

In 2006, the first Russian film based on one of his novels - The First Circle (V Kruge Pervom) - was shown on Russian state television, four decades after it was published.

The 10-part TV film depicted the terror of Stalin's regime, describing the Soviet Union as a huge prison camp.

Also in 2006, Solzhenitsyn, then 87, castigated Nato, accusing it of trying to bring Russia under its control.

He accused the organisation of "preparing to completely encircle Russia and deprive if of its sovereignty".

By then, Alexander Solzhenitsyn had already secured his place in history as one of the greatest Russian writers of the 20th Century.