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Νόμπελ Φυσικής 2011

Three scientists share Nobel Prize in Physics for research
showing the universe is expanding at an ever-increasing rate

Επιμέλεια: Νίκου Τσούλια

[Τελευταία ενημέρωση 5.10.11, 2 μ.μ.]

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Η σκοτεινή ενέργεια «χάρισε» το Νόμπελ Φυσικής σε τρεις επιστήμονες

Εύη Ελευθεριάδου, ΤΑ ΝΕΑ 4.10.11

Σε τρεις επιστήμονες, δύο Αμερικανούς και έναν Αμερικανο-Αυστραλό, απονεμήθηκε το Νόμπελ Φυσικής επειδή ανακάλυψαν «προς μεγάλη τους έκπληξη» ότι το σύμπαν επεκτείνεται με ολοένα και μεγαλύτερη επιτάχυνση όταν παρατήρησαν απομακρυσμένα σούπερ νόβα.

Πρόκειται για τους Σαούλ Περλμιούτερ από το Εθνικό Εργαστήριο Λόρενς στο Πανεπιστήμιο του Μπέρκλεϊ της Καλιφόρνια, τον Άνταμ Ρις από το Πανεπιστήμιο Τζονς Χόπκινς στη Βαλτιμόρη και τον Μπράιαν Σμιντ από το Εθνικό Πανεπιστήμιο της Αυστραλίας.
Ο Περλμιούτερ κέρδισε το μισό βραβείο, ενώ το υπόλοιπο το μοιράστηκαν οι άλλοι δύο επιστήμονες.

Το 1998, οι επιστήμονες ηγούνταν δύο ομάδων, που παρατηρούσαν μακρυνές εκρήξεις αστέρων (σούπερ νόβα). Έπειτα από παρατηρήσεις χρόνων, οι επιστήμονες κατέληξαν στο συμπέρασμα ότι το σύμπαν διαστέλλεται με ταχύτητα που αυξάνεται συνεχώς. Ήταν ένα δεδομένο που δεν περίμεναν να βρουν και το οποίο άλλαξε το μοντέλο για το σύμπαν πάνω στο οποίο βασίζονται οι θεωρίες της επιστημονικής κοινότητας.

«Εδώ και έναν αιώνα ήταν γνωστό ότι το σύμπαν επεκτείνεται ως αποτέλεσμα του Μπιγκ Μπανγκ πριν από 14 δισεκατομμύρια χρόνια. Η ανακάλυψη όμως, ότι αυτή η επέκταση γίνεται με ολοένα και επιταχυνόμενο ρυθμό, είναι εκπληκτική. Αν συνεχίσει η αύξηση της ταχύτητας της επέκτασης, τότε το σύμπαν θα γίνει κάποια στιγμή πάγος», αναφέρει σε ανακοίνωσή της η Βασιλική Ακαδημία Επιστημών της Σουηδίας.
Όταν οι επιστήμονες έκαναν αυτή την ανακάλυψη, έμειναν και οι ίδιοι έκπληκτοι. «Ανακοινώσαμε τελικά με φόβο στον κόσμο ότι φτάσαμε σε αυτό το τρελλό συμπέρασμα, ότι το σύμπαν ανεβάζει ταχύτητα», δήλωσε ο Σμιντ μετά την ανακοίνωση του Νόμπελ.

Οι ειδικοί παρατήρησαν μακρυνούς αστέρες που εκρήγνυνται, σούπερ νόβα. Αντί να γίνονται πιο φωτεινά, έχαναν τη λάμψη τους. «Το απρόσμενο συμπέρασμα ήταν ότι, όχι μόνο δε μειώνεται ο ρυθμός επέκτασης του σύμπαντος, αλλά επιταχύνεται», αναφέρει η ανακοίνωση της Επιτροπής Νόμπελ.
Η αιτία αυτής της επιτάχυνσης είναι ένα μεγάλο μυστήριο που απασχολεί τους κοσμολόγους. Οι ειδικοί φαίνεται να καταλήγουν στη λεγόμενη σκοτεινή ενέργεια, ένα είδος αντίστροφης βαρύτητας, η οποία υπολογίζουν πως αποτελεί το 75% του σύμπαντος.

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Στους μελετητές των σουπερνόβα το Νόμπελ Φυσικής

ΕΛΕΥΘΕΡΟΤΥΠΙΑ 4.11.10

Τρεις επιστήμονες που μελετούν τις εκρήξεις των αστεριών σε σουπερνόβα και την επιταχυνόμενη επέκταση του σύμπαντος, θα μοιραστούν το βραβείο Νόμπελ Φυσικής του 2011.

Από το χρηματικό έπαθλο των 10 εκατομυρίων κορωνών Σουηδίας (1,1 εκατ. Ευρώ), τα μισά θα πάρει ο Αμερικανός Σολ Περλμούτερ και το άλλο μισό ο Αμερικανοαυστραλός πολίτης Μπράιαν Σμιτ με τον  Αμερικανό Άνταμ Ρις.

Ο Σολ Περλμούτερ γεννήθηκε το 1959 στο Σαμπέιν-Ουρμπάνα (Ιλινόι, ΗΠΑ) και είναι καθηγητής της αστροφυσικής στο Πανεπιστήμιο της Καλιφόρνιας στο Μπέρκλεϊ. Ο Άνταμ Ρις γεννήθηκε το 1969 στην Ουάσινγκτον και διδάσκει αστρονομία και φυσική στο Πανεπιστήμιο Τζονς Χόπκινς στη Βαλτιμόρη (ΗΠΑ). Ο Μπράιαν Σμιτ γεννήθηκε το 1967 στο Μισούλα (Μοντάνα, ΗΠΑ) και διευθύνει την ομάδα έρευνας για τα σουπερνόβα στο Εθνικό Αυστραλιανό Πανεπιστήμιο του Ουέστον Κρικ.

Όπως ανακοίνωσε η Επιτροπή Νόμπελ Φυσικής της Βασιλικής Σουηδικής Ακαδημίας Επιστημών οι επιστήμονες βραβεύονται γιατί "μελέτησαν αρκετές δεκάδες αστέρες που εκρήγυντο, οι οποίοι αποκαλούνται σουπερνόβα, και ανακάλυψαν πως το σύμπαν επεκτείνεται με διαρκώς επιταχυνόμενο ρυθμό. Η ανακάλυψη αιφνιδίασε ακόμη και τους ίδιους τους βραβευθέντες".

"Καταλήξαμε να πούμε στον κόσμο ότι έχουμε αυτό το τρελό αποτέλεσμα, ότι το σύμπαν επιταχύνει", δήλωσε τηλεφωνικά ο Σμιτ, μετά την ανακοίνωση στη Στοκχόλμη πως είναι ένας από τους τρεις νικητές του βραβείου, προσθέτωντας ότι  "έμοιαζε πολύ τρελό να έχουμε δίκιο και πιστεύω ότι φοβόμασταν λίγο".

Ο 44χρονος Σμιτ ομολόγησε ακόμα ότι "λύγισαν τα γόνατά" του όταν τον ειδοποίησαν για τη βράβευσή του και αισθάνθηκε “λίγο όπως όταν γεννήθηκαν τα παιδιά μου, αισθάνομαι να έχουν λυθεί τα γόνατά μου, πολύ ενθουσιασμένος".

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Τρεις μοιράζονται το Νόμπελ Φυσικής 

 www.kathimerini.gr με πληροφορίες από AP, 4.10.11

Ο Σολ Περλμιούτερ, ο Μπράιαν Σμιντ και ο Άνταμ Ρις βραβεύτηκαν για τις έρευνές τους πάνω στη διαστολή του σύμπαντος.

Τρεις επιστήμονες από τις ΗΠΑ κέρδισαν το Νόμπελ Φυσικής, για τις μελέτες τους πάνω στη διαστολή του σύμπαντος, μέσω της παρατήρησης σουπερνόβα.

Η Βασιλική Σουηδική Ακαδημία Επιστημών ανακοίνωσε ότι ο Αμερικανός Σολ Περλμιούτερ θα μοιραστεί το βραβείο, ύψους 1,5 εκατομμυρίων δολαρίων, με τον Αμερικανοαυστραλό Μπράιαν Σμιντ και τον Αμερικανό Άνταμ Ρις. Εργαζόμενοι σε δύο διαφορετικές ερευνητικές ομάδες κατά τη δεκαετία του 1990 (οι Περλμιούτερ και Σμιντ ήταν στη μία και ο Ρις στην άλλη), οι τρεις επιστήμονες σημείωσαν σημαντική επιτυχία στην καταγραφή της διαστολής του σύμπαντος μέσω της ανάλυσης και μελέτης των σουπερνόβα.

Αυτό που ανακάλυψαν, πιο συγκεκριμένα, ήταν ότι το φως που εκπέμπεται από πάνω από 50 απομακρυσμένα σουπερνόβα ήταν πιο αδύναμο από ό,τι αναμενόταν- κάτι που αποτελεί απόδειξη ότι το σύμπαν διαστέλλεται με ολοένα και πιο επιταχυνόμενους ρυθμούς.

Το ότι το σύμπαν διαστέλλεται, ως αποτέλεσμα του Big Bang πριν από 14 δισεκατομμύρια χρόνια, είναι γνωστό εδώ και περίπου έναν αιώνα, ωστόσο δεν ήταν γνωστό ότι η διαστολή λαμβάνει χώρα με τόσο μεγάλες ταχύτητες.

Ο Περλμιούτερ, 52 ετών, είναι επικεφαλής του Supernova Cosmology Project του πανεπιστημίου της Καλιφόρνια (Μπέρκλεϊ). Ο Σμιντ, 44, είναι ο επικεφαλής της High-z Supernova Search Team του Εθνικού Πανεπιστημίου της Αυστραλίας. Ο Ρις, 42, είναι καθηγητής αστρονομίας στο πανεπιστήμιο Τζονς Χόπκινς και στο Ινστιτούτο Επιστημών Διαστημικών Τηλεσκοπίων στη Βαλτιμόρη.

Το περσινό Νόμπελ Φυσικής δόθηκε στους Αντρέ Γκάιμ και Κωνσταντίν Νοβοσέλοφ για τα πειράματά τους με το γραφένιο, το πιο ανθεκτικό και λεπτό υλικό στον κόσμο.

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Τα σύνορα του Σύμπαντος τους χάρισαν το Νομπέλ

Τρεις επιστήμονες μοιράζονται το βραβείο Φυσικής για το 2011

ΣΤΕΦΑΝΟΣ ΚΡΙΚΚΗΣ, ΤΑ ΝΕΑ 5.10.11

Σε τρεις επιστήμονες που ανακάλυψαν ότι το Σύμπαν διαστέλλεται με επιταχυνόμενο ρυθμό απονεμήθηκε χθες το μεσημέρι στη Στοκχόλμη το Νομπέλ Φυσικής για το 2011.

Η ανώτερη επιστημονική διάκριση, που αντιστοιχεί σε 1,45 εκατομμύρια δολάρια, επιμερίστηκε ανάμεσα στον Αμερικανό Σαούλ Πέρλμουτερ και στους Μπράιαν Σμιντ με αμερικανοαυστραλιανή καταγωγή και Ανταμ Ράιες, επίσης από τις ΗΠΑ.

Οι τρεις ερευνητές, που εργάζονταν ανεξάρτητα σε δύο διαφορετικές επιστημονικές ομάδες, παρουσίασαν το 1998 τα αποτελέσματα των ερευνών τους που κατεδείκνυαν ότι το Σύμπαν είχε πολύ διαφορετική συμπεριφορά από ό,τι πιστευόταν μέχρι τότε.

Οι επιστήμονες διενεργούσαν μακροχρόνιες παρατηρήσεις πάνω στους υπερκαινοφανείς αστέρες (σουπερνόβα) και ειδικότερα σε εκείνους που είναι γνωστοί ως Τύπου Ia. Οι αστέρες αυτοί είναι λευκοί νάνοι, δηλαδή παγωμένοι αστέρες που απορροφούν τη μάζα από ένα κοντινό τους αστέρι.

Οταν ένα σουπερνόβα απορροφήσει μάζα μεγαλύτερη από ένα καθορισμένο όριο, τότε ο υπερκαινοφανής αστέρας θα υποστεί μια θερμοπυρηνική έκρηξη καθώς θα καταρρεύσει κάτω από το βάρος της ίδιας του της βαρύτητας.

Η έκρηξη επομένως που ακολουθεί είναι τόσο μεγάλη και το αστρικό υλικό εκτοξεύεται προς κάθε κατεύθυνση με αποτέλεσμα το εκπεμπόμενο φως να είναι δυνατότερο ακόμη και από το φως που εκπέμπει ένας ολόκληρος γαλαξίας.

Οι ερευνητές μελέτησαν περισσότερους από 50 υπερκαινοφανείς αστέρες και διαπίστωσαν ότι το φως που εξέπεμπαν ήταν πιο αδύνατο απ’ όσο ανέμεναν να είναι.

Περίμεναν ότι το φως θα γινόταν όλο και πιο έντονο αλλά προς μεγάλη τους έκπληξη, εκείνο γινόταν όλο και πιο θαμπό. Ηταν σαν να αφήναμε πίσω μας τη λάμψη, σαν να απομακρυνόμαστε όλο και πιο γρήγορα από εκείνες τις εκρήξεις.

Η διαπίστωση αυτή, συνοδευόμενη από πληθώρα στοιχείων και δεδομένων, οδήγησε στο συμπέρασμα ότι το Σύμπαν μας δεν διαστέλλεται απλώς αλλά επεκτείνεται με πολύ ταχύ ρυθμό. Στην ανακοίνωση της Επιτροπής Νομπέλ Φυσικής της Βασιλικής Σουηδικής Ακαδημίας επισημάνθηκε ότι για σχεδόν ένα αιώνα ήταν γνωστό ότι το Σύμπαν διαστέλλεται ως συνέπεια της Μεγάλης Εκρηξης που συνέβη πριν από περίπου 14 δισεκατομμύρια χρόνια.

Ωστόσο, ανέφερε η ανακοίνωση, «η ανακάλυψη ότι αυτή η διαστολή είναι επιταχυνόμενη αποτελεί εκπληκτικό γεγονός. Αν η διαστολή του συνεχίσει να συμβαίνει με επιταχυνόμενο ρυθμό, τότε το Σύμπαν θα παγώσει».

Η επιτάχυνση διαστολής του Σύμπαντος, αποδίδεται στην αινιγματική σκοτεινή ενέργεια. Η φύση της σκοτεινής ενέργειας έχει κατανοηθεί ελάχιστα έως καθόλου και αποτελεί ένα από τα μεγαλύτερα μυστήρια της Φυσικής σήμερα.

Αυτό που γνωρίζουμε προς το παρόν είναι ότι η σκοτεινή ενέργεια αποτελεί περίπου τα του Σύμπαντος. Οι τρεις επιστήμονες βοήθησαν να κατανοήσουμε πόσα πράγματα δεν ξέραμε για το Σύμπαν και «κάθε ανακάλυψη από εδώ και πέρα είναι πιθανή».

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Nobel prize for discovery
that the universe is accelerating into the void
Nobel Prize in Physics 
 

Three scientists share Nobel Prize in Physics for research showing the universe is expanding at an ever-increasing rate

Ian Sample, science correspondent , guardian.co.uk, 4 October 2011

The Nobel Prize in Physics 2011 has been awarded to Saul Perlmutter, Brian P Schmidt and Adam G Riess for discovering the accelerating expansion of the universe

Adam Riess 2011 Nobel Physics Prize with Saul Perlmutter (R) and Brian Schmidt

From left to right, Adam Riess, Brian Schmidt and Saul Perlmutter, who have won the 2011 Nobel Prize in Physics. Photograph: Agencies

Scientists who watched stars explode in faraway galaxies and deduced that the universe was expanding at an ever-faster rate have won the Nobel Prize in Physics.

The discovery in the late 1990s meant textbooks had to be rewritten and forced researchers to consider a universe of stars and planets that is being torn apart by a mysterious force that counteracts gravity.

The nature of the force that drives the growth of the cosmos is so mysterious that scientists named it "dark energy". It is thought to make up more than 70% of the universe.

Half of the 10 million Swedish kronor (£934,000) prize money went to the US physicist Saul Perlmutter, 52, and the other half to two members of a competing team that conducted similar work, the US-born researcher Brian Schmidt, 44, who is based in Australia, and another US scientist, Adam Riess, aged 42.

The award was greeted with widespread approval from scientists, though some argued that by recognising only three physicists, the prize distorted how the research was done.

Two teams, headed by Perlmutter and Schmidt, raced each other to make exquisitely precise observations of distant supernovae – or exploding stars – and announced their controversial results within weeks of each other in 1998. Both found that instead of the light from 50 dying stars becoming brighter, it was fading.

This suggested that the expansion of the universe was not slowing down as expected, but accelerating. The result was a shock to the physics community because, overwhelmingly, cosmologists expected gravity to slow the expansion of the cosmos and even orchestrate its demise in a cosmic crunch at the end of time.

"We expected to find that the universe was slowing down, because gravity would attract everything to everything else, but instead we found it was speeding up. But this is what scientists look for: you discover something new and it opens up a whole new world of opportunities and mystery that we can then try to explore," Perlmutter told the Guardian.

"When we first presented the results, we really had to think hard, are we ready to show people something that is so counterintuitive? We finally came to the conclusion that we had done all the right crosschecks and we had to go ahead and show people," Perlmutter added.

Perlmutter, who is based at the University of California, Berkeley, heard he had won the Nobel prize at around 2.45am on Tuesday morning when a Swedish journalist called. The Nobel committee had failed to contact him because they had an old mobile phone number.

Brian Schmidt at the Australian National University in Weston Creek told the Guardian that he wrote to his team when the result held up under intense scrutiny. "I said that’s the way science is. We are not being good scientists if we prejudge the universe. The universe does what it wants, not what we want it to do," Schmidt said.

"Scientists must stand up and tell people what they find and we suffer the consequences if we make a mistake. We are seeing this in action right now with faster-than-light neutrinos. People are very sceptical of that, but those guys have done what they can to make it go away."

Lord Rees, the astronomer royal, said the prize recognised an "important and surprising discovery", that empty space contains energy that causes cosmic expansion to accelerate. "It will be a long time before theorists understand this force – it is part of the bedrock nature of space and time," he said.

But Rees said the award failed to acknowledge work done by others in the two teams: "This is one of the increasingly frequent instances when the Nobel committee is damagingly constrained by its tradition that a prize can’t be shared between more than three individuals. The key papers recognised by this award were authored by two groups, each containing a dozen or so scientists. It would have been fairer, and would send a less distorted message about how this kind of science is actually done, if the award had been made collectively to all members of the two groups."

Schmidt said he and the other prize recipients saw the prize as a celebration of the work done by all of the team members. "The Nobel prize is the Nobel prize and it has a great impact because of the way it is done. In this case I would love to share it with my colleagues and I will be inviting my colleagues to Stockholm to celebrate it with me even if they are not officially on the award," he said.

Pedro Ferreira, a cosmologist at Oxford University, said the prize was "wonderful" news. "You have to put this into perspective. Only a few decades ago, cosmology was exciting, but quite esoteric. People could make stuff up and get away with it. Now, because of endeavours such as the supernovae observations, we can make hard, accurate statements about the cosmos, we can really say precise things about the state of the universe. And it is only going to get better. It is a truly great time to be working in the field," he said.

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Studies of Universe’s Expansion Win Physics Nobel
By DENNIS OVERBYE
The New York Times, October 4, 2011

Three astronomers won the Nobel Prize on Tuesday for discovering that the universe is apparently being blown apart by a mysterious force that cosmologists now call dark energy, a finding that has thrown the fate of the universe and indeed the nature of physics into doubt.

NASA, via Agence France-Presse — Getty Images

An exploding star known as Type 1a supernova. The Nobel prize winners used them to measure the expansion of the universe.

They are Saul Perlmutter, 52, of the Lawrence Berkeley National Laboratory in Berkeley, Calif.; Brian P. Schmidt, 44, of the Australian National University in Weston Creek, Australia, and Adam G. Riess, 41, of the Space Telescope Science Institute and Johns Hopkins University in Baltimore.

“I’m stunned,” Dr. Riess said by e-mail, after learning of his prize by reading about it on The New York Times’s Web site.

The three men led two competing teams of astronomers who were trying to use the exploding stars known as Type 1a supernovas as cosmic lighthouses to limn the expansion of the universe. The goal of both groups was to measure how fast the cosmos, which has been expanding since its fiery birth in the Big Bang 13.7 billion years ago, was slowing down, and thus to find out if its ultimate fate was to fall back together in what is called a Big Crunch or to drift apart into the darkness.

Instead, the two groups found in 1998 that the expansion of the universe was actually speeding up, a conclusion that nobody would have believed if not for the fact that both sets of scientists wound up with the same answer. It was as if, when you tossed your car keys in the air, instead of coming down, they flew faster and faster to the ceiling. Subsequent cosmological measurements have confirmed that roughly 70 percent of the universe by mass or energy consists of this antigravitational dark energy, though astronomers and physicists have no conclusive evidence of what it is.

The most likely explanation for this bizarre behavior is a fudge factor that Albert Einstein introduced into his equations in 1917 to stabilize the universe against collapse and then abandoned as his greatest blunder.

Quantum theory predicts that empty space should exert a repulsive force, like dark energy, but one that is 10 to the 120th power times stronger than what the astronomers have measured, leaving some physicists mumbling about multiple universes. Abandoning the Einsteinian dream of a single final theory of nature, they speculate that there are a multitude of universes with different properties. We live in one, the argument goes, that is suitable for life.

“Every test we have made has come out perfectly in line with Einstein’s original cosmological constant in 1917,” Dr. Schmidt said.

If the universe continues accelerating, astronomers say, rather than coasting gently into the night, distant galaxies will eventually be moving apart so quickly that they cannot communicate with one another and all the energy would be sucked out of the universe.

Edward Witten, a theorist at the Institute for Advanced Study, Einstein’s old stomping grounds, called dark energy “the most startling discovery in physics since I have been in the field. It was so startling, in fact, that I personally took quite a while to become convinced that it was right.”

He went on, “This discovery definitely changed the way physicists look at the universe, and we probably still haven’t fully come to grips with the implications.”

Dr. Perlmutter, who led the Supernova Cosmology Project out of Berkeley, will get half of the prize of 10 million Swedish kronor ($1.4 million). The other half will go to Dr. Schmidt, leader of the rival High-Z Supernova Search Team, and Dr. Riess, who was the lead author of the 1998 paper in The Astronomical Journal, in which the dark energy result was first published. All three were born and raised in the United States; Dr. Schmidt is also a citizen of Australia. They will get their prizes in Stockholm on Dec. 10.

Since the fate of the universe is in question, astronomers would love to do more detailed tests using supernovas and other observations. So they were dispirited last year when NASA announced that cost overruns and delays on the James Webb Space Telescope had left no room in the budget until the next decade for a satellite mission to investigate dark energy that Dr. Perlmutter and others had been promoting for almost a decade.

Cosmic expansion was discovered by Edwin Hubble, an astronomer at the Mount Wilson Observatory in Pasadena, Calif., in 1929, but the quest for precision measurements of the universe has been hindered by a lack of reliable standard candles, objects whose distance can be inferred by their brightness of some other observable characteristic. Type 1a supernovas, which are thought to result from explosions of small stars known as white dwarfs, have long been considered uniform enough to fill the bill, as well as bright enough to be seen across the universe.

In the late 1980s Dr. Perlmutter, who had just gotten a Ph.D. in physics, devised an elaborate scheme involving networks of telescopes tied together by the Internet to detect and study such supernovas and use them to measure the presumed deceleration of the universe. The Supernova Cosmology Project endured criticism from other astronomers, particularly supernova experts, who doubted that particle physicists could do it right.

Indeed, it took seven years before Dr. Perlmutter’s team began harvesting supernovas in the numbers they needed. Meanwhile, the other astronomers had formed their own team, the High-Z team, to do the same work.

“Hey, what’s the strongest force in the universe?” asked Robert Kirshner, of the Harvard-Smithsonian Center for Astrophysics, and a mentor to many of the astronomers on the new team, told a reporter from this newspaper once, “It’s not gravity, it’s jealousy.”

In an interview with the Associated Press, Dr. Perlmutter described the subsequent work of the teams as “a long aha.” The presence of dark energy showed up in an expected faintness on the part of some distant supernovas: the universe had sped up and carried them farther away from us than conventional cosmology suggested.

As recounted by the science writer Richard Panek in his recent book, “The 4% Universe, Dark Matter, Dark Energy, and the Race to Discover the Rest of Reality,” neither team was eager to report such a strange result.

In January 1998, Dr. Riess took time off from his honeymoon to go over the results one more time and then e-mailed his comrades, “Approach these results not with your heart or head but with your eyes. We are observers after all!”

In the years since, the three astronomers have shared a number of awards, sometimes giving lectures in which they completed each other’s sentences. A Nobel was expected eventually.

“No more waiting!” Dr. Kirshner said Tuesday.

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Stellar performance nets physics prize

Nobel for supernovae signals of accelerating Universe.

Geoff Brumfiel, Nature, 4.10.11

Three astrophysicists have been awarded a Nobel prize for planting a perplexing puzzle at the heart of cosmology.

Half of the Nobel Prize in Physics goes to Saul Perlmutter of Lawrence Berkeley National Laboratory in California for leading a team that discovered that the Universe is expanding at an ever-increasing rate (S. Perlmutter et al. Astrophys. J. 517, 565–586; 1999). Brian Schmidt of the Australian National University in Weston Creek and Adam Riess of the Space Telescope Science Institute in Baltimore, Maryland, share the other half of the prize for independent measurements of the cosmic acceleration (A. G. Riess et al. Astron. J. 116, 1009–1038; 1998), which researchers have struggled to explain ever since.

"I feel kind of weak in the knees," Schmidt told reporters in Sweden via telephone. "It sort of feels like when my children were born."

All three scientists reached their conclusions on the basis of measurements of distant Type Ia supernovae. These occur in very specific types of binary star system, in which a white dwarf star tears matter away from its partner until it gains enough mass to explode. At their peak, Type Ia supernovae always emit roughly the same amount of light, making them useful as ‘standard candles’ by which to measure vast distances across the cosmos.

In the late 1980s and early 1990s, the prizewinners precisely measured the brightness of these supernovae using newly developed digital sensors. They then compared the brightness to the redshift — the change in colour of the light that results from the motion of the supernovae away from us. Both teams found that the supernovae were dimmer than expected at the measured redshift. The inescapable conclusion was that the Universe was not only expanding — which astronomers first realized in the 1920s — but expanding faster and faster.

Schmidt says that the finding was initially "pretty perplexing". Most astronomers had expected that the Universe’s rapid growth following the Big Bang would gradually slow down as gravity pulled distant galaxies towards each other. Yet the discovery was accepted almost immediately by the astronomical community — in part because the idea of a cosmic pressure pushing the Universe outwards had already been mooted by Albert Einstein.

When Einstein applied his general theory of relativity to the Universe as a whole in 1917, his equations included a ‘cosmological constant’ which described just such an outward force. Over the past decade, observations of the large-scale structure of the Universe, together with the cosmic microwave background radiation — the faint afterglow of the Big Bang — have also indicated that the majority of the Universe’s energy remains undetected. Today, the astronomical community accepts that about 73% of the Universe’s energy is invested in this cosmic acceleration. Known as dark energy, it remains a largely mysterious force. "Nobody really knows what it is that has been discovered," says Peter Coles, an astrophysicist at Cardiff University, UK.

The predominant view is that dark energy results from quantum fluctuations in the vacuum of space, but efforts to use quantum theory to describe it have so far failed. Other theories, including modifications of gravity, have gained little acceptance.

"It could be none of the above," Coles says. But "we wouldn’t be on the trail of this ‘none-of-the-above’ if it hadn’t been for these experiments".

 

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Still-mysterious dark energy takes physics Nobel

04 October 2011 by Anil Ananthaswamy, New Scientist

Three cosmologists have shared a Nobel prize in physics for their discovery that the expansion of the universe is accelerating.

"The observation has changed our understanding of the universe," said physicist Olga Botner for the Nobel prize committee at a press conference in Stockholm, Sweden. "This discovery is fundamental and a milestone for cosmology."

The accelerated expansion has been attributed to the energy of space-time itself, dubbed dark energy. Dark energy creates a repulsive force that counters gravity and is now tearing apart space-time. It’s "dark" because physicists don’t know its exact nature.

Half of this year’s prize goes to Saul Perlmutter of the Lawrence Berkeley National Laboratory in California, and the other half will be shared by Brian Schmidt of the Australian National University in Weston Creek, Australian Capital Territory, and Adam Riess of Johns Hopkins University in Baltimore, Maryland.

Too crazy to be right

In the late 1990s, Perlmutter’s team and another team led by Schmidt and Riess were independently studying distant exploding stars known as type-Ia supernovae. They were using these supernovae to measure how the universe’s expansion is changing with time. The expectation was that, billions of years after the big bang, it would be slowing down – but they found the opposite.

"It seemed too crazy to be right," said Schmidt, speaking to the Nobel committee press conference from his home in Canberra, Australia.

But it was right. The presence of dark energy has been independently backed up by measurements of the cosmic microwave background, the radiation left over from the big bang.

Dark choices

When asked about how it felt to receive a Nobel prize, Schmidt said, "It sort of feels like [when] my children were born, weak at the knees, amazed."

Given that the Nobel committee have awarded a prize for an observation concerning something we still don’t quite understand, they were asked by the press why they didn’t consider awarding the prize for the equally mysterious dark matter, the substance needed to explain why spinning galaxies don’t fly apart.

In the early 1970s, Vera Rubin made observations of the velocities of stars that imply dark matter exists.

"With regards to Vera Rubin," said Botner, "yes, she was one of the people who is said to have discovered dark matter. She’s not the only one. And there’s a history behind it which still has to be investigated. It’s not as clear-cut as today’s prize."

Martin Rees, a cosmologist at the University of Cambridge, commended the choice of dark energy for the Nobel. "This award recognises an important and surprising discovery," he says. "Even empty space contains energy and exerts a kind of ‘antigravity’ which causes cosmic expansion to accelerate. It will be a long time before theorists understand this force – it is part of the bedrock nature of space and time."

He did lament, however, that the prize can’t be shared between more than three individuals.

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Dark-energy pioneers scoop Nobel prize

Physics World, Oct 4, 2011,

Nobel prize medal
The 2011 Nobel Prize for Physics has been awarded to Saul Perlmutter from the Lawrence Berkeley National Laboratory, US, Adam Riess at Johns Hopkins University, in Baltimore, and Brian Schmidt from the Australian National University, Weston Creek, "for the discovery of the accelerating expansion of the universe through observations of distant supernovae".

Perlmutter has been awarded a half of the SEK10m (£934,000) prize, with Riess and Schmidt sharing the other half. In a statement, the Royal Swedish Academy of Sciences said "For almost a century, the universe has been known to be expanding as a consequence of the Big Bang about 14 billion years ago. However, the discovery that this expansion is accelerating is astounding. If the expansion will continue to speed up the universe will end in ice."

Going against gravity

Only 25 years ago most scientists believed that the universe could be described by Albert Einstein and Willem de Sitter’s simple and elegant model from 1932 in which gravity is gradually slowing down the expansion of space.

From the mid-1980s, however, a remarkable series of observations was made that did not seem to fit the standard theory, leading some people to suggest that an old and discredited term from Einstein’s general theory of relativity – the "cosmological constant" or "lambda" – should be brought back to explain the data.

This constant had originally been introduced by Einstein in 1917 to counteract the attractive pull of gravity, because he believed the universe to be static. He considered it a property of space itself, but it can also be interpreted as a form of energy that uniformly fills all of space; if lambda is greater than zero, the uniform energy has negative pressure and creates a bizarre, repulsive form of gravity. However, Einstein grew disillusioned with the term and finally abandoned it in 1931 after Edwin Hubble and Milton Humason discovered that the universe is expanding.

In 1987 physicists at the Lawrence Berkeley National Laboratory and the University of California at Berkeley initiated the Supernova Cosmology Project (SCP) to hunt for certain distant exploding stars, known as type Ia supernovae. They hoped to use these stars to calculate, among other things, the rate at which the expansion of the universe was slowing down.

Deceleration was expected because in the absence of lambda, many people thought that "ΩM", which is the amount of observable matter in the universe today as a fraction of the critical density, was sufficient to slow the universe’s expansion forever, if not to bring it to an eventual halt.

In 1998, after years of observations, two rival groups of supernova hunters – the High-Z Supernovae Search Team led by Schmidt and Riess and the SCP led by Perlmutter – came to the conclusion that the cosmic expansion is actually accelerating and not slowing under the influence of gravity as might be expected.

The two teams came to this conclusion by studying type Ia supernova where they found that the light from over 50 distant supernovae was weaker than expected. This was a sign that the expansion of the universe was accelerating.

In order to account for the acceleration, about 75% of the mass-energy content of the universe had to be made up of some gravitationally repulsive substance that nobody had ever seen before. This substance, which would determine the fate of the universe, was dubbed dark energy.

It is now thought that dark energy constitutes around 75% of the current universe, with around 21% being dark matter and the rest ordinary matter and energy making up the Earth, planets and stars.

"The findings of the 2011 Nobel Laureates in Physics have helped to unveil a universe that to a large extent is unknown to science," stated the Academy. "And everything is possible again."

"My involvement in the discovery of the accelerating universe and its implications for the presence of dark energy has been an incredibly exciting adventure," says Riess. "I have also been fortunate to work with tremendous colleagues and powerful facilities. I am deeply honored that this work has been recognized."

New problems

Cosmologist Michael Turner from the University of Chicago says that the award to Perlmutter, Riess and Schmidt is "well deserved". "The two competing teams is a wonderful story in science – the physicists vs the astronomers," says Turner. "The biggest surprise to both teams was that the other team got the same answer. Each team believed the other didn’t know what they were doing."

Turner adds that before the discovery, cosmology was in some disarray with astronomers having a model of the universe based on cold dark matter and inflation, but with not enough matter to make the universe flat – a key prediction of inflation.

"Dark energy and cosmic acceleration was the missing piece of the puzzle," says Turner. "Moreover, in solving one problem, it gave us a new problem – what is dark energy? I think that is the most profound mystery in all of science."

Robert Kirshner from Harvard University who supervised both Schmidt and Riess when they were PhD students says the decision by the Nobel committee is "great" as it will mean "no more waiting". "We did a lot of foundational work at Harvard and my postdocs and students made up a hefty chunk of the High-Z Team," says Kirshner. "[Riess] did a lot after the initial result to show that there was no sneaky effect due to dust absorption and that, if you look far enough into the past, you could see that the universe was slowing down before the dark energy got the upper hand, about five billion years ago."

Kirshner adds that Perlmutter is also "very deserving" of the prize. "[Perlmutter] was persistent even when his programme was moving slowly and, despite getting a contrary result in 1997, was convinced of cosmic acceleration during 1998 by comparing his own extensive data set of distant supernovae with the nearby supernovae measured by the group in Chile."

Peter Knight, president of the Institute of Physics, which publishes physicsworld.com says the work has "triggered an enormous amount of research" on the nature of dark energy. "These researchers have opened our eyes to the true nature of our universe. They are very well-deserved recipients," says Knight.

Leading lights

Born in Champaign-Urbana, Illinois, in 1959, Perlmutter graduated from Harvard University in 1981 receiving his PhD from the University of California, Berkeley in 1986 where he worked on robotic methods of searching nearby supernovae. He then moved to the Lawrence Berkeley National Laboratory and the University of California, Berkeley. Perlmutter now heads the SCP based at Lawrence Berkeley National Laboratory.

Schmidt was born in Missoula, Montana, in 1967. He graduated from the University of Arizona in 1989 and received his PhD from Harvard University in 1993 on using type II Supernovae to measure the Hubble Constant. During postdocs at Harvard, Schmidt, together with Nicholas Suntzeff from the Cerro Tololo Inter-American Observatory in Chile, formed the High-Z Supernovae Search Team. In 1993 Schmidt then went to the Harvard-Smithsonian Center for Astrophysics for a year before moving to the Australian National University where he is currently based.

Riess is also a former member of the High-Z Supernovae Search Team where he lead the 1998 study that reported evidence that the universe’s expansion rate is now accelerating. He was born in Washington, D.C in 1969 and graduated from The Massachusetts Institute of Technology in 1992. Riess received his PhD from Harvard University in 1996 researching ways to make type Ia supernovae into accurate distance indicators. In 1999 he moved to the Space Telescope Science Institute at Johns Hopkins University.

About the author

Michael Banks is news editor of Physics World

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Alfred Nobel – His Life and Work

by Nils Ringertz*

Alfred Nobel was born in Stockholm on October 21, 1833. His father Immanuel Nobel was an engineer and inventor who built bridges and buildings in Stockholm. In connection with his construction work Immanuel Nobel also experimented with different techniques for blasting rocks.

Alfred Nobel

Alfred Nobel

Alfred’s mother, born Andriette Ahlsell, came from a wealthy family. Due to misfortunes in his construction work caused by the loss of some barges of building material, Immanuel Nobel was forced into bankruptcy the same year Alfred Nobel was born. In 1837 Immanuel Nobel left Stockholm and his family to start a new career in Finland and in Russia. To support the family, Andriette Nobel started a grocery store which provided a modest income. Meanwhile Immanuel Nobel was successful in his new enterprise in St. Petersburg, Russia. He started a mechanical workshop which provided equipment for the Russian army and he also convinced the Tsar and his generals that naval mines could be used to block enemy naval ships from threatening the city.

The naval mines designed by Immanuel Nobel were simple devices consisting of submerged wooden casks filled with gunpowder. Anchored below the surface of the Gulf of Finland, they effectively deterred the British Royal Navy from moving into firing range of St. Petersburg during the Crimean war (1853-1856). Immanuel Nobel was also a pioneer in arms manufacture and in designing steam engines

 naval mines

Painting by Immanuel Nobel demonstrating his sea or naval mines to the Tsar of Russia.

Successful in his industrial and business ventures, Immanuel Nobel was able, in 1842, to bring his family to St. Petersburg. There, his sons were given a first class education by private teachers. The training included natural sciences, languages and literature. By the age of 17 Alfred Nobel was fluent in Swedish, Russian, French, English and German. His primary interests were in English literature and poetry as well as in chemistry and physics. Alfred’s father, who wanted his sons to join his enterprise as engineers, disliked Alfred’s interest in poetry and found his son rather introverted. In order to widen Alfred’s horizons his father sent him abroad for further training in chemical engineering. During a two year period Alfred Nobel visited Sweden, Germany, France and the United States. In Paris, the city he came to like best, he worked in the private laboratory of Professor T. J. Pelouze, a famous chemist.

There he met the young Italian chemist Ascanio Sobrero who, three years earlier, had invented nitroglycerine, a highly explosive liquid. Nitroglycerine was produced by mixing glycerine with sulfuric and nitric acid. It was considered too dangerous to be of any practical use. Although its explosive power greatly exceeded that of gunpowder, the liquid would explode in a very unpredictable manner if subjected to heat and pressure. Alfred Nobel became very interested in nitroglycerine and how it could be put to practical use in construction work. He also realized that the safety problems had to be solved and a method had to be developed for the controlled detonation of nitroglycerine.

In the United States he visited John Ericsson, the Swedish-American engineer who had developed the screw propeller for ships. In 1852 Alfred Nobel was asked to come back and work in the family enterprise which was booming because of its deliveries to the Russian army. Together with his father he performed experiments to develop nitroglycerine as a commercially and technically useful explosive. As the war ended and conditions changed, Immanuel Nobel was again forced into bankruptcy. Immanuel and two of his sons, Alfred and Emil, left St. Petersburg together and returned to Stockholm. His other two sons, Robert and Ludvig, remained in St. Petersburg. With some difficulties they managed to salvage the family enterprise and then went on to develop the oil industry in the southern part of the Russian empire. They were very successful and became some of the wealthiest persons of their time.

Explosion in the laboratory in Stockholm.

After his return to Sweden in 1863, Alfred Nobel concentrated on developing nitroglycerine as an explosive. Several explosions, including one (1864) in which his brother Emil and several other persons were killed, convinced the authorities that nitroglycerine production was exceedingly dangerous. They forbade further experimentation with nitroglycerine within the Stockholm city limits and Alfred Nobel had to move his experimentation to a barge anchored on Lake Mälaren. Alfred was not discouraged and in 1864 he was able to start mass production of nitroglycerine. To make the handling of nitroglycerine safer Alfred Nobel experimented with different additives.

He soon found that mixing nitroglycerine with kieselguhr would turn the liquid into a paste which could be shaped into rods of a size and form suitable for insertion into drilling holes. In 1867 he patented this material under the name of dynamite. To be able to detonate the dynamite rods he also invented a detonator (blasting cap) which could be ignited by lighting a fuse. These inventions were made at the same time as the diamond drilling crown and the pneumatic drill came into general use. Together these inventions drastically reduced the cost of blasting rock, drilling tunnels, building canals and many other forms of construction work.

 laboratory

Alfred Nobel’s laboratory in Bofors, Sweden.

The market for dynamite and detonating caps grew very rapidly and Alfred Nobel also proved himself to be a very skillful entrepreneur and businessman. By 1865 his factory in Krümmel near Hamburg, Germany, was exporting nitroglycerine explosives to other countries in Europe, America and Australia. Over the years he founded factories and laboratories in some 90 different places in more than 20 countries. Although he lived in Paris much of his life he was constantly traveling. Victor Hugo at one time described him as "Europe’s richest vagabond". When he was not traveling or engaging in business activities Nobel himself worked intensively in his various laboratories, first in Stockholm and later in Hamburg (Germany), Ardeer (Scotland), Paris and Sevran (France), Karlskoga (Sweden) and San Remo (Italy). He focused on the development of explosives technology as well as other chemical inventions, including such materials as synthetic rubber and leather, artificial silk, etc. By the time of his death in 1896 he had 355 patents.

Intensive work and travel did not leave much time for a private life. At the age of 43 he was feeling like an old man. At this time he advertised in a newspaper "Wealthy, highly-educated elderly gentleman seeks lady of mature age, versed in languages, as secretary and supervisor of household." The most qualified applicant turned out to be an Austrian woman, Countess Bertha Kinsky. After working a very short time for Nobel she decided to return to Austria to marry Count Arthur von Suttner. In spite of this Alfred Nobel and Bertha von Suttner remained friends and kept writing letters to each other for decades. Over the years Bertha von Suttner became increasingly critical of the arms race. She wrote a famous book, Lay Down Your Arms and became a prominent figure in the peace movement. No doubt this influenced Alfred Nobel when he wrote his final will which was to include a Prize for persons or organizations who promoted peace. Several years after the death of Alfred Nobel, the Norwegian Storting (Parliament) decided to award the 1905 Nobel Peace Prize to Bertha von Suttner.

Alfred Nobel’s greatness lay in his ability to combine the penetrating mind of the scientist and inventor with the forward-looking dynamism of the industrialist. Nobel was very interested in social and peace-related issues and held what were considered radical views in his era. He had a great interest in literature and wrote his own poetry and dramatic works. The Nobel Prizes became an extension and a fulfillment of his lifetime interests.

Many of the companies founded by Nobel have developed into industrial enterprises that still play a prominent role in the world economy, for example Imperial Chemical Industries (ICI), Great Britain; Société Centrale de Dynamite, France; and Dyno Industries in Norway. Toward the end of his life, he acquired the company AB Bofors in Karlskoga, where Björkborn Manor became his Swedish home. Alfred Nobel died in San Remo, Italy, on December 10, 1896.

When his will was opened it came as a surprise that his fortune was to be used for Prizes in Physics, Chemistry, Physiology or Medicine, Literature and Peace. The executors of his will were two young engineers, Ragnar Sohlman and Rudolf Lilljequist. They set about forming the Nobel Foundation as an organization to take care of the financial assets left by Nobel for this purpose and to coordinate the work of the Prize-Awarding Institutions. This was not without its difficulties since the will was contested by relatives and questioned by authorities in various countries.

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