Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Time gives rays a break

07.03.2002


Like a photo, space and time probably look grainy at close quarters.
© GettyImages/NSU


Jumps in space-time might explain the curious survival of energetic particles.

Space and time must be grainy, not smooth. Otherwise high-energy particles produced in astrophysical processes would not be detectable on Earth.

So says Richard Lieu of the University of Alabama in Huntsville. Many agree that jumps in space-time occur on scales that are far too small to measure, but the idea has not yet been proved. Lieu now shows that using this hypothesis can explain how highly energetic particles can travel through space and avoid annihilating collisions1.



Physicists suspect that at distances trillions of times smaller than the width of an atom space is not like a smooth sheet. At this scale, they think it is more like a chessboard, with objects disappearing from one square and reappearing in another.

Ditto time. For durations of about 5x10-44 seconds, events are thought to happen in a series of freeze-frames.

These short intervals of space and time are called the Planck distance and the Planck time. They are named after the German physicist Max Planck who initiated quantum theory, which posited that the energies of atoms and molecules are quantized, or discretely divided.

Atomic quantum theory is firmly established, but the notion that space-time itself is quantized is much harder to test because the Planck time and distance are so small.

Grain bar

Quantization implies that close up, space-time is like a photograph: the apparent smoothness breaks up into grainy patches. Normally we would never notice the grains. Lieu reckons their effects become important at very high energies.

According to Einstein’s general theory of relativity, events involving very fast-moving objects look different to an observer moving at the same speed as the object compared with an observer who is stationary relative to the object. Time seems to move more slowly for the stationary observer. To relate the two frames of reference, one must perform a mathematical adjustment called a Lorentz transformation.

If space-time is grainy, the particles’ positions can’t be pinned down any more accurately than the grain size: there is an unavoidable uncertainty equal to the Planck distance. Similarly, times can’t be specified any more accurately than the Planck time.

Point of view

Lieu shows that at high energies, where relativity has appreciable effects, the Lorentz transformation effectively magnifies these uncertainties. This means that, although they are still tiny in the moving frame of reference, the uncertainties are appreciable to the stationary observer.

So even if particles seem to have enough energy to destroy themselves in collisions with the low-energy microwave photons pervading the Universe, creating showers of new particles in the process, they don’t. From the microwave photons’ point of view, many of the particles aren’t energetic enough to induce such a fate, thanks to space-time graininess.

This might explain why very-high-energy gamma rays have been detected from a distant galaxy-like object called a blazar, suggests Lieu. Astrophysicists expected most of these rays to be wiped out by collisions with intervening microwave photons in space.

The same goes for cosmic rays, the high-energy subatomic particles that stream through space. Predictions say that these should thin out abruptly above a certain energy level because of photon collisions. But no such energy cut-off has been found experimentally, perhaps because of the inflated Planck-scale uncertainties in the particles’ energies.

References

  1. Lieu, R. The effect of Planck scale space time fluctuations on Lorentz invariance at extreme speeds. Astrophysical Journal Letters, in press (2002).

PHILIP BALL | © Nature News Service

More articles from Physics and Astronomy:

nachricht Explosion on Jupiter-sized star 10 times more powerful than ever seen on our sun
18.04.2019 | University of Warwick

nachricht In vivo super-resolution photoacoustic computed tomography by localization of single dyed droplets
18.04.2019 | Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Explosion on Jupiter-sized star 10 times more powerful than ever seen on our sun

A stellar flare 10 times more powerful than anything seen on our sun has burst from an ultracool star almost the same size as Jupiter

  • Coolest and smallest star to produce a superflare found
  • Star is a tenth of the radius of our Sun
  • Researchers led by University of Warwick could only see...

Im Focus: Quantum simulation more stable than expected

A localization phenomenon boosts the accuracy of solving quantum many-body problems with quantum computers which are otherwise challenging for conventional computers. This brings such digital quantum simulation within reach on quantum devices available today.

Quantum computers promise to solve certain computational problems exponentially faster than any classical machine. “A particularly promising application is the...

Im Focus: Largest, fastest array of microscopic 'traffic cops' for optical communications

The technology could revolutionize how information travels through data centers and artificial intelligence networks

Engineers at the University of California, Berkeley have built a new photonic switch that can control the direction of light passing through optical fibers...

Im Focus: A long-distance relationship in femtoseconds

Physicists observe how electron-hole pairs drift apart at ultrafast speed, but still remain strongly bound.

Modern electronics relies on ultrafast charge motion on ever shorter length scales. Physicists from Regensburg and Gothenburg have now succeeded in resolving a...

Im Focus: Researchers 3D print metamaterials with novel optical properties

Engineers create novel optical devices, including a moth eye-inspired omnidirectional microwave antenna

A team of engineers at Tufts University has developed a series of 3D printed metamaterials with unique microwave or optical properties that go beyond what is...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

Revered mathematicians and computer scientists converge with 200 young researchers in Heidelberg!

17.04.2019 | Event News

First dust conference in the Central Asian part of the earth’s dust belt

15.04.2019 | Event News

Fraunhofer FHR at the IEEE Radar Conference 2019 in Boston, USA

09.04.2019 | Event News

 
Latest News

New automated biological-sample analysis systems to accelerate disease detection

18.04.2019 | Life Sciences

Explosion on Jupiter-sized star 10 times more powerful than ever seen on our sun

18.04.2019 | Physics and Astronomy

New eDNA technology used to quickly assess coral reefs

18.04.2019 | Life Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>