In this illustration, one photon (purple) carries a million times the energy of another (yellow). Some theorists predict travel delays for higher-energy photons, which interact more strongly with the proposed frothy nature of space-time. Yet Fermi data on two photons from a gamma-ray burst fail to show this effect. The animation below shows the delay scientists had expected to observe. Credit: NASA/Sonoma State University/Aurore Simonnet

Einstein Still Rules, Says Fermi Telescope Team

28 Oct , 2009 by

[/caption]

While the Fermi Space Telescope has mapped the gamma ray sky with unprecedented resolution and sensitivity, it now has been able to take a measurement that has provided rare experimental evidence about the very structure of space and time, unified as space-time. Einstein’s theory of relativity states that all electromagnetic radiation travels through a vacuum at the same speed. Fermi detected two gamma ray photons which varied widely in energy; yet even after traveling 7 billion years, the two different photons arrived almost simultaneously.

On May 10, 2009, Fermi and other satellites detected a so-called short gamma ray burst, designated GRB 090510. Astronomers think this type of explosion happens when neutron stars collide. Ground-based studies show the event took place in a galaxy 7.3 billion light-years away. Of the many gamma ray photons Fermi’s LAT detected from the 2.1-second burst, two possessed energies differing by a million times. Yet after traveling some seven billion years, the pair arrived just nine-tenths of a second apart.

“This measurement eliminates any approach to a new theory of gravity that predicts a strong energy dependent change in the speed of light,” Michelson said. “To one part in 100 million billion, these two photons traveled at the same speed. Einstein still rules.”

“Physicists would like to replace Einstein’s vision of gravity — as expressed in his relativity theories — with something that handles all fundamental forces,” said Peter Michelson, principal investigator of Fermi’s Large Area Telescope, or LAT, at Stanford University in Palo Alto, Calif. “There are many ideas, but few ways to test them.”

Artist concept of Fermi in space. Credit: NASA

Artist concept of Fermi in space. Credit: NASA


Many approaches to new theories of gravity picture space-time as having a shifting, frothy structure at physical scales trillions of times smaller than an electron. Some models predict that the foamy aspect of space-time will cause higher-energy gamma rays to move slightly more slowly than photons at lower energy.

GRB 090510 displayed the fastest observed motions, with ejected matter moving at 99.99995 percent of light speed. The highest energy gamma ray yet seen from a burst — 33.4 billion electron volts or about 13 billion times the energy of visible light — came from September’s GRB 090902B. Last year’s GRB 080916C produced the greatest total energy, equivalent to 9,000 typical supernovae.

More images and videos about the Fermi Space Telescope.

Lead image caption: In this illustration, one photon (purple) carries a million times the energy of another (yellow). Some theorists predict travel delays for higher-energy photons, which interact more strongly with the proposed frothy nature of space-time. Yet Fermi data on two photons from a gamma-ray burst fail to show this effect. The animation below shows the delay scientists had expected to observe. Credit: NASA/Sonoma State University/Aurore Simonnet

Source: NASA

,



Sort by:   newest | oldest | most voted
The Eclectic Exterminator of Stupid Electricians
Member
The Eclectic Exterminator of Stupid Electricians
October 28, 2009 12:28 PM

“Physicists would like to replace Einstein’s vision of gravity — as expressed in his relativity theories — with something that handles all fundamental forces,” said Peter Michelson.

Take that on the chin AnaCONda!!

Considering you don’t believe in most of the four forces nor of the importance of their interactions, this must be another fatal nail in that coffin of EU.
Of course, you will come up with an excuse or another nitwit argument, but it shows much of everyday physics is close to reality.

Science and Einstein and left us a wonderful legacy. Pity you just can’t see it! sad

Jon Hanford
Member
Jon Hanford
October 28, 2009 1:52 PM

Greatt news, Nancy, on results from the first year-long study of the VHE Gamma-ray all sky flux from the Fermi satellite. As longer exposures are undertaken in The VHE/UHE portion of the EM spectrum, surely the it presents an opportunity to study and speculate as to the astrophysical origins, evolution and formation these highly energetic objects.

Navneeth
Member
Navneeth
October 28, 2009 2:48 PM

Nancy, did you mean to say [i]simultaneously[/i] at the end of the first paragraph, instead of [i]at instantaneously[/i]. Or was it, perhaps, [i]at the same time[/i]?

Navneeth
Member
Navneeth
October 28, 2009 2:49 PM

I’m still in BB mode and forgot all about HTML tags. oops

DrFlimmer
Member
DrFlimmer
October 28, 2009 2:57 PM

NewScientist also included in this story that this measurement contradicts an earlier experiment by the MAGIC collaboration. They had a time delay of 4 minutes! But their object was much closer than this one here, so Fermi is probably a little more right than MAGIC.

At least, I hope so – because a difference of 4 minutes between two light rays to arrive that should have been sent instantanously is quite a time, even on cosmological scales!

Nancy Atkinson
Guest
October 28, 2009 3:09 PM

Navneeth – yes, thank you for figuring out what I meant!

Lawrence B. Crowell
Member
Lawrence B. Crowell
October 28, 2009 3:47 PM

Great! This will send Smolin and Amelino-Camelia back to their offices and white boards. String theory makes a beautiful prediction that this chaotic foam is valenced from measurable physics, or in a sense renormalized out. This is really good news.

LC

Lawrence B. Crowell
Member
Lawrence B. Crowell
October 28, 2009 4:08 PM

The research paper is at:

http://arxiv.org/ftp/arxiv/papers/0908/0908.1832.pdf

I have been having long hard arm wrestling sessions over this. This makes me absolutely giddy! Bye bye loop quantum gravity breaking of the Lorentz group at small scales — YIPEEE!!! There are litterally thousands of theory papers now which are worth less than toilet paper. God it feels good. smile

And to think I delayed reading this blog post and spent so much time on the global warming kerfuffle. Hon. Salacious B. Crumb should sharpen his rapier against the deniers over there. Anaconda is just a minor voice of nonsense. Anti-AGW people are more serious.

LC

Astrofiend
Member
Astrofiend
October 28, 2009 5:09 PM

Lawrence B. Crowell Says:
October 28th, 2009 at 4:08 pm

Don’t be too humble in victory or anything Lawrence!

…but I was about to say the same thing. There will be a lot of crest-fallen physicists out there at the moment, realising that they’ve just spent a fat wad of their career on a whole bunch of wrong.

Lawrence B. Crowell
Member
Lawrence B. Crowell
October 28, 2009 5:36 PM
Oh for sure. I think I heard a number of big thuds of bodies falling. I put Smolin on that list, but that guy is smart enough and did not put all his eggs in this basket. He dropped a couple of eggs though. The person who I hope really hurts is … , well that would get personal. Loop Quantum Gravity is not dead though. In fact I have been working, rather unsuccessfully to be honest, on how LQG could be a system of constraints which exist in a map from the string/M-theory AdS_5 spacetime to the physical (the real universe) de Sitter spacetime. String theory works on the anti-de Sitter spacetime, but that is not the… Read more »
Astrofiend
Member
Astrofiend
October 28, 2009 9:14 PM
“I keep up with this and some other sites so I can keep abreast of these developments without having to golpher through the observational papers, which I find more difficult to read (to be honest) than theory/math papers.” Yeah – I wish my math were that good. Unfortunately for me, I have very limited natural ability or intuition in maths. All of my math ability has been hard won, and even then I think I’m pretty much reaching the limits of what I can understand mathematically without an order of magnitude increase in the amount of time I spend trying to get my head around it.! So I guess I’ll let you guys take care of the ultimate… Read more »
Black WiD/Oe H/Oe
Member
October 29, 2009 2:38 AM

I must ask this question and hopefully won’t be crucified for my ignorance. Be gentle people, for I am a very curious soul.

The short version if you can,
what is theTwistor (twister) theory? M-Theory?

Lawrence B. Crowell
Member
Lawrence B. Crowell
October 29, 2009 5:43 AM
A twistor is a pair of spinors (well what’s a spinor?, you might ask) where if one represents a flagged coordinate, the other is a momentum value. As such the position spinor x is related to the momentum spinor p by a “motion,” similar to x = x(0) + vt. Position and momentum are conjugate variables in Hamiltonian classical mechanics and quantum mechanics. The pair of spinors or the twistor constructs a manifold according to its projective structure, which defines light cones and so forth. As spinor is a variable which has algebraic properties identical to that of angular momentum or spin. M-theory is something Ed Witten advanced back in 1996. The M stands for a range of… Read more »
Astrofiend
Member
Astrofiend
October 29, 2009 5:50 AM
rudeyd Says: October 29th, 2009 at 2:38 am “hopefully won’t be crucified for my ignorance” Jeez – it’s not that scary in here, is it?! No one gets crucified for ignorance here, or for just asking questions… And speaking of which, It’s a pretty advanced question – certainly not something I’m too knowledgeable about, though I’m sure there are a couple of people in here that could help in far more detail than I (and probably more accurately). I’m not quite sure what the question was – were you asking if Twistor theory IS M-theory, or were you asking what both Twistor theory and M-theory are? Anyway, from what little I think I know about this, twistor theory… Read more »
Astrofiend
Member
Astrofiend
October 29, 2009 5:53 AM

Ahh – I see Mr. LBC has beat me to the punch.

Lawrence B. Crowell
Member
Lawrence B. Crowell
October 29, 2009 7:39 AM
Astrofried wrote a reasonable description of things. Twistors were proposed by Roger Penrose back in 1967, the same date that Weinberg and Salaam propsed the electroweak theory. It is on C^4 or in real dimensions M^8 and it has a structure which gives rise to projective systems that correspond to light cones. There are types I and II strings of subtype A and B and the closed heterotic string. An open string is attached to a D-brane, think of the loops of thread in shag-carpet attached to the rug. The dynamics of the string is such that it can pinch off and release a closed string. So the membrane is a sort of anchor for the open string… Read more »
Torbjorn Larsson OM
Member
Torbjorn Larsson OM
October 29, 2009 2:19 PM
But this is old (and good!) news, why the late or absent reaction from the LQG people? [Scratches head] The first piece of good news is, as I understood the paper at the time, that it is a Planck scale test! And people said such bests didn’t exist. The second piece of good news is that Lorentz invariance goes well into the Planck scale. Rather modestly with the significant observations, but hinting at possibly orders of magnitude; love to get a repeat of that. So spacetime is an emergent property, at least in GR, but despite numerous dimensions relative positions are behaving nicely. No froth or “spacetime quantization”, as far as I understand. The third piece of good… Read more »
Manu
Member
Manu
October 29, 2009 3:27 PM

@ Torbjorn:

“it is a Planck scale test”

I’d like to understand this!

Lawrence B. Crowell
Member
Lawrence B. Crowell
October 29, 2009 8:06 PM
Torbjorn, The biggest problem LQG has is gauge ambiguity and the Barbero-Immirzi parameter problem. The breaking of Lorentz symmetry is another problem, which I think has just been killed. In the end LQG is basically a system of constraints. The Wheeler DeWitt equation gives us that NH = 0, N^iH_i = 0 which are not dynamics! These are just constraint equations or Lagrange multipliers. These can be canonically quantized. Most of what LQG does is to impose a constraint on sources which obtain from Gauss law on Sen connections, and a conformal constraint. LQG has a problem with bounding quantum states. The reason is there is no fundamental concept of time. The reason there is no time operator… Read more »
Jon Hanford
Member
Jon Hanford
October 30, 2009 12:25 PM

Another informative, illuminating, thought provoking discussion on a topic. Hopefully this rational discourse catches on here at UT for the sake of interested readers and long-time UT followers. Thanks to all who took the time to elucidate for others as to the real significance of this finding.

Special thanks to LBC for pointing me to the less technical , more accessible books on this subject from Susskind and Randall.

wpDiscuz