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Far off in universe, the same laws found

June 21, 2008
Courtesy Max Planck Institute 
for Radio Astronomy
and World Science staff

Na­ture’s laws ap­pear to be the same in the dis­tant uni­ver­se as they are he­re, a study has found.

As­tro­no­mers de­ter­mined that one of the key num­bers in phys­ics is about the same in a gal­axy six bil­lion light years away as it is on Earth. A light-year is the dis­tance light trav­els in a year.

As light from the qua­sar trav­els to Earth, the uni­verse con­tin­ues its usual expansion. This ef­fect­ive­ly "stretches" the light, caus­ing it to get red­der the long­er it trav­els. The light is al­so grav­i­ta­tion­ally "lensed" (its path is bent) as it passes through an in­ter­ven­ing gal­ax­y; when a ra­di­o map of the field is made, two qua­sar im­ages ap­pear. How­ev­er, the mo­lec­u­lar ab­sorp­tion clouds are on­ly along the line of sight to one im­age. Fur­ther­more, when very high res­o­lu­tion im­ages are made of that qua­sar im­age, some struc­ture is ev­i­dent - a co­re (the bright­est part of the im­age) and a knot­ty je­t ex­tend­ing away from the qua­sar co­re. It's on­ly to­wards the qua­sar co­re that mo­lec­u­lar ab­sorp­tion is thought to oc­cur. (Im­age credits: Tel­e­scope: N. Junkes; Ra­di­o in­sets: A. Biggs; In­ter­ven­ing gal­ax­y: NA­SA, ESA, STScI & W. Keel; Qua­sar: NA­SA, ESA, STScI & E. Beck­with).

Sci­en­tists have de­bat­ed wheth­er the laws of phys­ics may change at dif­fer­ent cos­mic times and places. 

The study sug­gests these rules “are the same in this gal­axy half way across the vis­i­ble uni­ver­se as they are he­re,” said as­t­ro­phys­i­cist Mi­chael Mur­phy of Swin­burne Uni­ver­s­ity in Aus­tral­ia, lead au­thor of a pa­per on the find­ings. 

The work ap­pears in the June 20 is­sue of the re­search jour­nal Sci­ence.

The num­ber stud­ied was the weight or mass ra­tio be­tween the pro­ton and elec­tron, parts of the at­om. The ra­tio is found to be about 1836.15. 

The as­tro­no­mers ex­am­ined the is­sue by ef­fec­tively look­ing back in time at a qua­sar, the lu­mi­nous co­re of a dis­tant gal­axy, whose light took 7.5 bil­lion years to reach us. Along the way, it was partly ab­sorbed by am­mo­nia gas in an­oth­er gal­axy.

Not only is am­mo­nia use­ful in bath­room clean­ing, it’s a good mol­e­cule to test our un­der­stand­ing of phys­ics, Mur­phy said. Am­mo­nia ab­sorbs the qua­sar’s ra­dio waves, a form of light. But only waves with cer­tain en­er­gies are ab­sorbed. 

These pre­cise ab­sorp­tion char­ac­ter­is­tics are sen­si­tive to the pro­ton-e­lec­tron mass ra­tio, and can be meas­ured from Earth us­ing de­vices known as spec­tro­scopes.

The re­search­ers used a spec­tro­scope on the Ef­fels­berg 100m ra­dio tel­e­scope near Bonn, Ger­ma­ny. “By com­par­ing the am­mo­nia ab­sorp­tion with that of oth­er mol­e­cules, we were able to de­ter­mine the val­ue of the pro­ton-e­lec­tron mass ra­tio in this gal­axy,” said study co-au­thor Chris­tian Henkel of the Max Planck In­sti­tute for Ra­dio As­tron­o­my in Bonn.

The as­tro­no­mers said they plan to con­tin­ue test­ing na­ture’s laws in dif­fer­ent cos­mic places and times, but they need to find more ab­sorb­ing ga­lax­ies. The stud­ied gal­axy, des­ig­nat­ed B0218+367, is the only tar­get for this kind of re­search so far. There must be many more tar­get ga­lax­ies out the­re, as soon as the right tel­e­scopes to find them are availa­ble, the re­search­ers said.

Mur­phy said the prob­lem could be solved with the pro­posed Square Kil­o­me­tre Ar­ray, or SKA, tel­e­scope, which sci­en­tists al­so be­lieve could pick up dis­tant civ­il­iz­a­tions’ tel­e­vi­sion sig­nals.

“The SKA is the larg­est, most am­bi­tious in­terna­t­ional tel­e­scope proj­ect ev­er con­ceived,” Mur­phy said. The tel­e­scope’s loca­t­ion, which has been short-listed to West­ern Aus­tral­ia or South­ern Af­ri­ca, is to be an­nounced with­in two years. By con­tin­u­ing their re­search in­to na­ture’s forc­es, the as­tro­no­mers al­so hope to find a win­dow in­to the ex­tra di­men­sions of space that many the­o­ret­i­cal phys­i­cists think may ex­ist.

* * *

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Nature’s laws appear to be the same in the distant universe as they are here, a study has found. Astronomers determined that one of the key numbers in physics is about the same in a galaxy six billion light years away as it is on Earth. A light-year is the distance light travels in a year. Scientists have debated whether the laws of physics may change at different cosmic times and places. The study suggests these laws “are the same in this galaxy half way across the visible Universe as they are here,” said astrophysicist Michael Murphy of Swinburne University in Australia, lead author of a paper on the findings. The work appears in the June 20 issue of the research journal Science. The number studied was the weight or mass ratio between the proton and electron, parts of the atom. The ratio is found to be about 1836.15. The astronomers examined the issue by effectively looking back in time at a quasar, the luminous core of a distant galaxy, whose light took 7.5 billion years to reach us. Along the way, it was partly absorbed by ammonia gas in another galaxy. Not only is ammonia useful in bathroom cleaning, it’s a good molecule to test our understanding of physics, Murphy said. Ammonia absorbs the quasar’s radio waves, a form of light, but only waves with certain energies. These precise absorption characteristics are sensitive to the proton-electron mass ratio, and can be measured from Earth using devices known as spectroscopes. The researchers used a spectroscope on the Effelsberg 100m radio telescope near Bonn, Germany. “By comparing the ammonia absorption with that of other molecules, we were able to determine the value of the proton-electron mass ratio in this galaxy, and confirm that it is the same as it is on Earth,” said Christian Henkel of the Max Planck Institute for Radio Astronomy in Bonn, a co-author of the study. The astronomers said they plan to continue testing nature’s laws in different cosmic places and times, but they need to find more absorbing galaxies. The studied galaxy, designated B0218+367, is the only target for this kind of research so far. There must be many more target galaxies out there, as soon as the right telescopes to find them are available. Murphy said this problem could be overcome with the proposed Square Kilometre Array, or SKA, telescope, which scientists also believe could pick up distant civilizations’ television signals. “The SKA is the largest, most ambitious international telescope project ever conceived. When completed it will have an enormous collecting area, and will allow us to search for more absorbing galaxies,” Murphy said. The telescope’s location, which has been short-listed to Western Australia or Southern Africa, is to be announced within two years. By continuing their research into nature’s forces, the astronomers also hope to find a window into the extra dimensions of space that many theoretical physicists think may exist.