Berkeley v. Cambridge: Battle over the Laws of Physics
"We are claiming something extraordinary here," acknowledged astrophysicist Michael Murphy of Cambridge University in England, one of the scientists who reported possible evidence of a change in the fine structure constant at a scientific conference earlier this year. "And the evidence, though strong, is not yet extraordinary enough."
At another science conference, a group of Berkeley scientists reported that alpha is not changing, based on their independent analysis of light from galaxies.
Recent study forces scientists to rethink basic law of physics
'Fine structure constant' is indeed a constant -- right?
Keay Davidson, Chronicle Science Writer
Legislators change laws from time to time, but Mother Nature's laws are eternal -- or so it has seemed.
Now, though, scientists are debating clues that suggest the laws of physics change over time. University of California scientists are among the major players on both sides of the debate, which threatens to shake up our basic notions of reality.
At stake is one of the fundamental values in physics: the arcane-sounding "fine structure constant," which measures how subatomic particles interact with light and with each other.
Some astrophysicists have proposed that the value of the fine structure constant, a.k.a. "alpha," has changed subtly over billions of years. They base this proposal on their work -- using telescopes like the giant Keck telescope, which sits atop a dormant Hawaiian volcano -- analyzing light from interstellar gas and galaxy-gobbling super-furnaces called quasars on the outskirts of the universe.
If they're right, then our theories of the cosmos might be due for an overhaul. One speculation is that alpha is changing over time because of now- unknown alternate dimensions. As these hidden dimensions change shape, they change the fine structure constant.
But skeptics, citing observations that contradict the claim that alpha is changing, are plentiful -- and even the pro-change claimants are being cautious, partly because there's so much at risk. The notion that the laws of physics are eternal and unchanging is one of the ground-floor assumptions of everyday life -- when you drop a ball, for example, you expect it to fall, not to rise -- and no one wants to abandon that assumption unless they've got compelling reasons.
"We are claiming something extraordinary here," acknowledged astrophysicist Michael Murphy of Cambridge University in England, one of the scientists who reported possible evidence of a change in the fine structure constant at a scientific conference earlier this year. "And the evidence, though strong, is not yet extraordinary enough."
At another science conference, a group of Berkeley scientists reported that alpha is not changing, based on their independent analysis of light from galaxies.
Observational techniques
Murphy defends his observational technique as more precise than that of critics. As he reported recently, his latest observations have "a precision of 1 in a million. So it's about a factor of 30 better" than the technique deployed by critics, he told The Chronicle.
The critics disagree. They say that their observational technique is relatively simple and, thus, yields pretty unambiguous results, whereas Murphy's technique is an especially complex one that is vulnerable to all kinds of "systematic errors," in scientific lingo.
In short, what's brewing is a dandy little scientific controversy. It's one in which, paradoxically, very much depends on very little -- that is, in which unimaginably slight variations in measurements could alter our understanding of the whole universe.
The idea that nature's laws change over time was proposed in the 1930s by one of the titans in the history of physics, Paul Dirac of England. According to Dirac's large numbers hypothesis, the force of gravity changed over time. Others modified his thesis to argue that the fine structure constant is, in fact, inconstant.
Twenty-one years after Dirac's death, his theory still hasn't been proved.
"These are very adventurous ideas -- and it's always healthy to challenge the things that 'everybody knows,' " says one of the nation's most distinguished astronomers, Robert Kirshner of Harvard. "I would be very surprised if there are measurable changes in the fine structure constant."
Skeptics keep open minds
But, referring to the 1990s discovery of dark energy, a mysterious cosmic force that counteracts the force of gravity and causes the universe to expand faster over time, he added: "I was also very surprised that the 'cosmological constant' isn't zero! In any case, the burden of proof is on the person making an extraordinary claim. The rest of us are skeptical, but our minds are open to convincing evidence."
In mid-April, noted physicist-author Lee Smolin of the Perimeter Institute in Waterloo, Ontario, heard Murphy present his latest findings.
It is too soon to tell if the fine structure constant is changing, Smolin said in an e-mail. "It is a very hard measurement, and there are many possible sources of error." At the same time, he wrote, "I would not be surprised if the measurement is right. ... (I have) a nervous feeling that we have become too complacent (in cosmology), having gone too long without a shocking new experimental discovery."
Murphy, who has since moved to England, was part of an Australian scientific team led by astronomer John K. Webb that started the debate rolling again in 2001 with a report in the journal Physical Review Letters. Using the Keck telescope, they said, they had observed subtle anomalies in light from quasars.
Specifically, they reported puzzling shifts in the position of thin dark lines in the quasars' spectra, the rainbow-like bands of light produced when the light passes through a prism; just as the keys on a piano produce different frequencies of sound, the colors in the spectra correspond to different frequencies of light.
The dark spectral lines are absorption lines, which reveal how light is absorbed by different types of atoms in outer space, while thin bright emission lines reveal light emitted by atoms.
Here was the surprise: The faraway quasars' dark spectral lines occupied slightly different positions from those occupied by related lines in the spectra of light from laboratory instruments. It was, very roughly speaking, like discovering a new alphabet in which X comes before W.
The quasars are 12 billion light years away; the Australian scientists were literally looking back in time and seeing what the cosmos looked like 12 billion years ago.
They proposed an explanation for the anomaly in the position of the quasars' absorption lines: namely, the fine structure constant was very slightly weaker 12 billion years ago. Since the fine structure constant controls the strength of electromagnetism -- of which light is the visible manifestation -- it "therefore controls the way light and matter interact," Murphy says. Hence the anomalous absorption lines are signatures of a weaker constant long, long ago -- just after the Big Bang and more than 7 billion years before the formation of Earth.
Others conduct studies
Since then, scientists around the world have jumped into the debate. Some support the idea of long-term change in alpha, others contradict it, and yet others say it's too soon to decide. For example:
-- Astronomer Jeffrey Newman of Lawrence Berkeley National Laboratory reported at the American Physical Society meeting in Tampa in April that he had analyzed emission lines of light from galaxies up to 7 billion light years away. He detected no evidence of a long-term change in alpha, he said. Newman's results are pretty definitive, says his associate, astronomer Marc Davis of UC Berkeley.
-- Physicist Steve Lamoreaux of Los Alamos National Laboratory and his colleagues have analyzed data from a so-called natural nuclear reactor near Oklo in Gabon, Africa, where a large geological deposit of uranium has radioactively decayed over the last 2 billion years. In theory, a long-term variation in the fine structure constant should modify the concentration of radioactive waste products from the natural reactor -- and indeed, the Lamoreaux team has calculated that the fine structure constant has varied slightly.
"No one's published a counter-calculation to what we did, and I think it's pretty unlikely that (our claim is) going to change," Lamoreaux said in a phone interview last week.
-- UC Berkeley physicist Dmitry Budker and colleagues are using sensitive lab instruments to check for changes in alpha over a period of a few years. So far, they have collected four months of measurements of the fine structure constant -- too little to suggest any conclusions one way or another, Budker said last week.
Until more decisive evidence comes in, most astronomers are playing it safe. For now, they're assuming that Mother Nature is what she has always seemed to be: constant, not fickle.
"Until we have independent studies that converge on a single answer," says astronomer Stephen P. Maran, press officer for the American Astronomical Society and author of "Astronomy for Dummies," "the doubters will prevail, and the fine structure constant will continue to be regarded as well, constant."
E-mail Keay Davidson at kdavidson@sfchronicle.com.
URL: http://sfgate.com/cgi-bin/article.cgi?file=/c/a/2005/05/09/MNG5LCLEU41.DTL
Monday, May 9, 2005
©2005 San Francisco Chronicle
Whose correct? Who which university will prove to be the one with the better observations and conclusions?
At another science conference, a group of Berkeley scientists reported that alpha is not changing, based on their independent analysis of light from galaxies.
Recent study forces scientists to rethink basic law of physics
'Fine structure constant' is indeed a constant -- right?
Keay Davidson, Chronicle Science Writer
Legislators change laws from time to time, but Mother Nature's laws are eternal -- or so it has seemed.
Now, though, scientists are debating clues that suggest the laws of physics change over time. University of California scientists are among the major players on both sides of the debate, which threatens to shake up our basic notions of reality.
At stake is one of the fundamental values in physics: the arcane-sounding "fine structure constant," which measures how subatomic particles interact with light and with each other.
Some astrophysicists have proposed that the value of the fine structure constant, a.k.a. "alpha," has changed subtly over billions of years. They base this proposal on their work -- using telescopes like the giant Keck telescope, which sits atop a dormant Hawaiian volcano -- analyzing light from interstellar gas and galaxy-gobbling super-furnaces called quasars on the outskirts of the universe.
If they're right, then our theories of the cosmos might be due for an overhaul. One speculation is that alpha is changing over time because of now- unknown alternate dimensions. As these hidden dimensions change shape, they change the fine structure constant.
But skeptics, citing observations that contradict the claim that alpha is changing, are plentiful -- and even the pro-change claimants are being cautious, partly because there's so much at risk. The notion that the laws of physics are eternal and unchanging is one of the ground-floor assumptions of everyday life -- when you drop a ball, for example, you expect it to fall, not to rise -- and no one wants to abandon that assumption unless they've got compelling reasons.
"We are claiming something extraordinary here," acknowledged astrophysicist Michael Murphy of Cambridge University in England, one of the scientists who reported possible evidence of a change in the fine structure constant at a scientific conference earlier this year. "And the evidence, though strong, is not yet extraordinary enough."
At another science conference, a group of Berkeley scientists reported that alpha is not changing, based on their independent analysis of light from galaxies.
Observational techniques
Murphy defends his observational technique as more precise than that of critics. As he reported recently, his latest observations have "a precision of 1 in a million. So it's about a factor of 30 better" than the technique deployed by critics, he told The Chronicle.
The critics disagree. They say that their observational technique is relatively simple and, thus, yields pretty unambiguous results, whereas Murphy's technique is an especially complex one that is vulnerable to all kinds of "systematic errors," in scientific lingo.
In short, what's brewing is a dandy little scientific controversy. It's one in which, paradoxically, very much depends on very little -- that is, in which unimaginably slight variations in measurements could alter our understanding of the whole universe.
The idea that nature's laws change over time was proposed in the 1930s by one of the titans in the history of physics, Paul Dirac of England. According to Dirac's large numbers hypothesis, the force of gravity changed over time. Others modified his thesis to argue that the fine structure constant is, in fact, inconstant.
Twenty-one years after Dirac's death, his theory still hasn't been proved.
"These are very adventurous ideas -- and it's always healthy to challenge the things that 'everybody knows,' " says one of the nation's most distinguished astronomers, Robert Kirshner of Harvard. "I would be very surprised if there are measurable changes in the fine structure constant."
Skeptics keep open minds
But, referring to the 1990s discovery of dark energy, a mysterious cosmic force that counteracts the force of gravity and causes the universe to expand faster over time, he added: "I was also very surprised that the 'cosmological constant' isn't zero! In any case, the burden of proof is on the person making an extraordinary claim. The rest of us are skeptical, but our minds are open to convincing evidence."
In mid-April, noted physicist-author Lee Smolin of the Perimeter Institute in Waterloo, Ontario, heard Murphy present his latest findings.
It is too soon to tell if the fine structure constant is changing, Smolin said in an e-mail. "It is a very hard measurement, and there are many possible sources of error." At the same time, he wrote, "I would not be surprised if the measurement is right. ... (I have) a nervous feeling that we have become too complacent (in cosmology), having gone too long without a shocking new experimental discovery."
Murphy, who has since moved to England, was part of an Australian scientific team led by astronomer John K. Webb that started the debate rolling again in 2001 with a report in the journal Physical Review Letters. Using the Keck telescope, they said, they had observed subtle anomalies in light from quasars.
Specifically, they reported puzzling shifts in the position of thin dark lines in the quasars' spectra, the rainbow-like bands of light produced when the light passes through a prism; just as the keys on a piano produce different frequencies of sound, the colors in the spectra correspond to different frequencies of light.
The dark spectral lines are absorption lines, which reveal how light is absorbed by different types of atoms in outer space, while thin bright emission lines reveal light emitted by atoms.
Here was the surprise: The faraway quasars' dark spectral lines occupied slightly different positions from those occupied by related lines in the spectra of light from laboratory instruments. It was, very roughly speaking, like discovering a new alphabet in which X comes before W.
The quasars are 12 billion light years away; the Australian scientists were literally looking back in time and seeing what the cosmos looked like 12 billion years ago.
They proposed an explanation for the anomaly in the position of the quasars' absorption lines: namely, the fine structure constant was very slightly weaker 12 billion years ago. Since the fine structure constant controls the strength of electromagnetism -- of which light is the visible manifestation -- it "therefore controls the way light and matter interact," Murphy says. Hence the anomalous absorption lines are signatures of a weaker constant long, long ago -- just after the Big Bang and more than 7 billion years before the formation of Earth.
Others conduct studies
Since then, scientists around the world have jumped into the debate. Some support the idea of long-term change in alpha, others contradict it, and yet others say it's too soon to decide. For example:
-- Astronomer Jeffrey Newman of Lawrence Berkeley National Laboratory reported at the American Physical Society meeting in Tampa in April that he had analyzed emission lines of light from galaxies up to 7 billion light years away. He detected no evidence of a long-term change in alpha, he said. Newman's results are pretty definitive, says his associate, astronomer Marc Davis of UC Berkeley.
-- Physicist Steve Lamoreaux of Los Alamos National Laboratory and his colleagues have analyzed data from a so-called natural nuclear reactor near Oklo in Gabon, Africa, where a large geological deposit of uranium has radioactively decayed over the last 2 billion years. In theory, a long-term variation in the fine structure constant should modify the concentration of radioactive waste products from the natural reactor -- and indeed, the Lamoreaux team has calculated that the fine structure constant has varied slightly.
"No one's published a counter-calculation to what we did, and I think it's pretty unlikely that (our claim is) going to change," Lamoreaux said in a phone interview last week.
-- UC Berkeley physicist Dmitry Budker and colleagues are using sensitive lab instruments to check for changes in alpha over a period of a few years. So far, they have collected four months of measurements of the fine structure constant -- too little to suggest any conclusions one way or another, Budker said last week.
Until more decisive evidence comes in, most astronomers are playing it safe. For now, they're assuming that Mother Nature is what she has always seemed to be: constant, not fickle.
"Until we have independent studies that converge on a single answer," says astronomer Stephen P. Maran, press officer for the American Astronomical Society and author of "Astronomy for Dummies," "the doubters will prevail, and the fine structure constant will continue to be regarded as well, constant."
E-mail Keay Davidson at kdavidson@sfchronicle.com.
URL: http://sfgate.com/cgi-bin/article.cgi?file=/c/a/2005/05/09/MNG5LCLEU41.DTL
Monday, May 9, 2005
©2005 San Francisco Chronicle
Whose correct? Who which university will prove to be the one with the better observations and conclusions?