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 New quantum phenomena in graphene superlattices
19.09.2017 | Graphene Flagship

nachricht Solar wind impacts on giant 'space hurricanes' may affect satellite safety
19.09.2017 | Embry-Riddle Aeronautical University

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: Ultrafast snapshots of relaxing electrons in solids

Using ultrafast flashes of laser and x-ray radiation, scientists at the Max Planck Institute of Quantum Optics (Garching, Germany) took snapshots of the briefest electron motion inside a solid material to date. The electron motion lasted only 750 billionths of the billionth of a second before it fainted, setting a new record of human capability to capture ultrafast processes inside solids!

When x-rays shine onto solid materials or large molecules, an electron is pushed away from its original place near the nucleus of the atom, leaving a hole...

Im Focus: Quantum Sensors Decipher Magnetic Ordering in a New Semiconducting Material

For the first time, physicists have successfully imaged spiral magnetic ordering in a multiferroic material. These materials are considered highly promising candidates for future data storage media. The researchers were able to prove their findings using unique quantum sensors that were developed at Basel University and that can analyze electromagnetic fields on the nanometer scale. The results – obtained by scientists from the University of Basel’s Department of Physics, the Swiss Nanoscience Institute, the University of Montpellier and several laboratories from University Paris-Saclay – were recently published in the journal Nature.

Multiferroics are materials that simultaneously react to electric and magnetic fields. These two properties are rarely found together, and their combined...

Im Focus: Fast, convenient & standardized: New lab innovation for automated tissue engineering & drug

MBM ScienceBridge GmbH successfully negotiated a license agreement between University Medical Center Göttingen (UMG) and the biotech company Tissue Systems Holding GmbH about commercial use of a multi-well tissue plate for automated and reliable tissue engineering & drug testing.

MBM ScienceBridge GmbH successfully negotiated a license agreement between University Medical Center Göttingen (UMG) and the biotech company Tissue Systems...

Im Focus: Silencing bacteria

HZI researchers pave the way for new agents that render hospital pathogens mute

Pathogenic bacteria are becoming resistant to common antibiotics to an ever increasing degree. One of the most difficult germs is Pseudomonas aeruginosa, a...

Im Focus: Artificial Enzymes for Hydrogen Conversion

Scientists from the MPI for Chemical Energy Conversion report in the first issue of the new journal JOULE.

Cell Press has just released the first issue of Joule, a new journal dedicated to sustainable energy research. In this issue James Birrell, Olaf Rüdiger,...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

“Lasers in Composites Symposium” in Aachen – from Science to Application

19.09.2017 | Event News

I-ESA 2018 – Call for Papers

12.09.2017 | Event News

EMBO at Basel Life, a new conference on current and emerging life science research

06.09.2017 | Event News

 
Latest News

“Lasers in Composites Symposium” in Aachen – from Science to Application

19.09.2017 | Event News

New quantum phenomena in graphene superlattices

19.09.2017 | Physics and Astronomy

A simple additive to improve film quality

19.09.2017 | Power and Electrical Engineering

VideoLinks
B2B-VideoLinks
More VideoLinks >>>