Variables of nature

September 5, 2014 by Brian Koberlein, One Universe At A Time
Diagram illustrating quasar observations. Credit: J. C. Berengut

Within physics there are certain physical quantities that play a central role. These are things such as the mass of an electron, or the speed of light, or the universal constant of gravity. We aren't sure why these constants have the values they do, but their values uniquely determine the way our universe works. For example, if the mass of electrons were smaller, atoms would be smaller. If the gravitational constant were larger, you'd need less mass to create a black hole, and neutron stars might not exist.

There are some who like to play "what if" scenarios about what the universe would be like if various fundamental constants had different values. There are others who make anthropic arguments that the constants must have the values they have in order for us to exist. But those are discussions for another time. Regardless of any speculation, we do know the values of these fundamental quantities very well. The and charge of an electron are known to about one part in a billion. The , perhaps the least well measured, is known to about one part in ten thousand.

These quantities are often referred to as , because it is generally thought that these quantities never change. Whatever the mechanism (or random chance) that gives them their values, once the universe began they became "locked in" as it were. There are several theoretical arguments as to why this is, but broadly it stems from the fact that the laws of physics appear to be the same everywhere in the universe. Gravity works the same way in distant galaxies as they do in our own. So if the laws of physics are the same everywhere in space, it's reasonable to assume they are the same everywhen in time.

But how could we tell if they weren't constant. After all, we do all of our observations in our corner of the , and in the present day. How can we test fundamental quantities in the past? One way it to look at what are known as unitless quantities. Fundamental quantities like electron mass have units (kilograms and the like), but you can multiply and divide certain fundamental quantities to create a number where the units cancel out. One of these quantities is known as alpha (α), which is a product of the charge of an electron, the , and a constant from quantum theory known as Planck's constant.

Since alpha has no units, its value is always the same, regardless of what units you use. The only way its value could change is if , light speed, or Planck's constant changed in relation to each other (or if there is some exotic physics we don't yet understand). The nice thing about alpha is that its value is central to the line spectra of atoms and molecules. If alpha had a different value, the wavelengths of light emitted or absorbed would shift slightly. So we can observe light from distant objects to test the constancy of alpha.

In 2010, a research team looked at light from distant quasars that had passed through large intergalactic clouds of gas. They found evidence of some slight variation of alpha depending on the direction we looked in the sky, which would imply a spatial variation of the physical constants. This made lots of news in the press, but the findings were not strong enough to be conclusive.

Then in 2012, a different team looked at the spectra of distant alcohol clouds (yes, there are clouds of alcohol in space), and measured another unitless constant, this time the ratio of the electron mass to the proton mass. What they found was that the mass ratio has changed no more than one part in a billion over the course of seven billion years. In other words, they are constant to the limits of our observation.

So it seems some things really do never change.

Explore further: Variations in fine-structure constant suggest laws of physics not the same everywhere

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17 comments

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vanhees71
not rated yet Sep 05, 2014
If the electron mass were smaller, the atoms were larger: The Bohr radius is

r=hbar/(m c alpha).

So, if m gets smaller, and the other fundamental constants (Planck constant, speed of light, and Sommerfeld fine structure constant) stay the same, the Bohr radius becomes larger, and this is the typical atomic length scale!
Aligo
Sep 05, 2014
This comment has been removed by a moderator.
MrVibrating
1 / 5 (2) Sep 05, 2014
One intruiging, if likely specious, reason for the apparent constancy might tie in with a possible answer to the Fermi paradox - what if intelligent intervention (ie. inadvertent meddling) is required to kick-start such a shift? Perhaps it can't happen 'in nature', by itself, but maybe the last time such a phase change was engineered the results precipitated our big bang?

http://phys.org/n...ser.html
Aligo
Sep 05, 2014
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arom
1 / 5 (5) Sep 05, 2014
Within physics there are certain physical quantities that play a central role. These are things such as the mass of an electron, or the speed of light, or the universal constant of gravity. We aren't sure why these constants have the values they do, but their values uniquely determine the way our universe works. For example, if the mass of electrons were smaller, atoms would be smaller. If the gravitational constant were larger, you'd need less mass to create a black hole, and neutron stars might not exist….


Unfortunately there is no explanation why the fundamental constants, such as speed of light is constant according to Einstein relativity assumption; maybe it is good to know its mechanism here ….
http://www.vacuum...24〈=en
msadesign
not rated yet Sep 06, 2014
"Why" isn't strictly the realm of science, although it's fun to speculate.

and @Aligo: what?
Aligo
Sep 06, 2014
This comment has been removed by a moderator.
swordsman
not rated yet Sep 06, 2014
These "constants" do not change. They are indeed constants. However, the observation from far distant signals in space can change. One factor commonly overlooked is "second Doppler", which can account for many of these difficulties in observing outer space.
Aligo
Sep 06, 2014
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Graeme
5 / 5 (1) Sep 07, 2014
If one of the "constants" actually did change at other places in the universe, what is stopping it from changing here on earth? Such changes have not been measured. The change in alpha measured could easily be explained by a changed in the shape of the spectral line due to different isotope ratios. But a variation in isotope ratio does then need an explanation. But at least this could easily be within existing physics.
Returners
1.8 / 5 (5) Sep 07, 2014
What they found was that the mass ratio has changed no more than one part in a billion over the course of seven billion years. In other words, they are constant to the limits of our observation.


No good. If both numbers are changing at about the same rate, then the RATIO would appear to not change anyway, and YOU the author, would draw the wrong conclusion, which is to say they are unchanged.

The Hubble Constant for space-time expansion would cause the local angular momenta of orbiting objects to change, since the amount of "space" between them is changing. This means that either conservation of angular momenta is wrong, or there is a universal "fudge factor" to fix the discrepancy, which implies at least one "universal constant", or else some other unknown variable, is actually changing.

Returners
1.8 / 5 (5) Sep 07, 2014
These "constants" do not change
Only if http://www.scient...nstants/


The location of Jupiter with respect to Earth (near or far side of the Sun) could change the length of the Meter or the apparent "weight" of a kilogram in the amount of significant digits mentioned here.
Aligo
Sep 07, 2014
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Aligo
Sep 07, 2014
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TheGhostofOtto1923
2.3 / 5 (3) Sep 08, 2014
No good. If both numbers are changing at about the same rate, then the RATIO would appear to not change anyway, and YOU the author, would draw the wrong conclusion, which is to say they are unchanged
Well of course because the author is

"an astrophysicist with a background in general relativity and computational astrophysics. Most recently I've written a textbook on the subject with David Meisel, which is available through Amazon and Cambridge University Press"... also a physics professor at Rochester Institute of Technology, where in addition to research I spend much of my time teaching undergraduate physics."

-who knows all about things like RATIOS and momenta and constants and such, while you are a drugged up, delusional amateur who never heard of alpha until you read the article.

Who the hell do you think you are? Seriously your attitude is sickening sometimes.
Jixo
Sep 08, 2014
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Jixo
Sep 08, 2014
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