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posted by martyb on Saturday April 11 2015, @02:38PM   Printer-friendly
from the 'contrails'-in-space! dept.

In an article published on arXiv.org [Full article available] California-based Raytheon engineers Ulvi Yurtsever and Steven Wilkinson say that any interstellar spacecraft traveling at near-light speed would leave distinct light signatures in its wake.

While special relativity imposes an absolute speed limit at the speed of light, our Universe is not empty Minkowski spacetime. The constituents that fill the interstellar/intergalactic vacuum, including the cosmic microwave background photons, impose a lower speed limit on any object traveling at relativistic velocities. Scattering of cosmic microwave photons from an ultra-relativistic object may create radiation with a characteristic signature allowing the detection of such objects at large distances.

 
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  • (Score: 2) by MichaelDavidCrawford on Saturday April 11 2015, @04:06PM

    by MichaelDavidCrawford (2339) Subscriber Badge <mdcrawford@gmail.com> on Saturday April 11 2015, @04:06PM (#168975) Homepage Journal

    I'm surprised this is even news.

    Astronomers are readily able to detect the spectral signature of gas in interstellar, even intergalactic space. It's mostly hydrogen atoms but at times more complex molecules.

    The problem this poses for space flight is that if you are traveling at even a substantial fraction of light velocity, this stuff will be hitting you with very high energy. It would be light gargling with the Large Hadron Collider.

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  • (Score: 1, Interesting) by Anonymous Coward on Saturday April 11 2015, @05:54PM

    by Anonymous Coward on Saturday April 11 2015, @05:54PM (#169001)

    I suppose it is because maybe nobody really talks about it in terms of macroscopic objects? At least within the cosmic ray field, for decades these issues have been at the heart of the mystery of where the highest energy cosmic rays come from. The momenta of the highest energy cosmic rays leads to blue shifting the cosmic ray background photons to high enough energies that the cosmic rays would lose their energy fast via processes like Compton scattering, which means that those particles should not be able to travel very far. However, there do not appear to be mechanisms close by that are capable of generating these cosmic rays.

    • (Score: 2) by MichaelDavidCrawford on Saturday April 11 2015, @06:14PM

      by MichaelDavidCrawford (2339) Subscriber Badge <mdcrawford@gmail.com> on Saturday April 11 2015, @06:14PM (#169014) Homepage Journal

      I should have know that - I did two different compton scattering labs during my physics degree.

      I commonly tell people that cosmic rays come from supernovae, even in other galaxies however I readily agree that could not possibly be the case.

      Dark matter decay? :-D

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      • (Score: 0) by Anonymous Coward on Monday April 13 2015, @01:11AM

        by Anonymous Coward on Monday April 13 2015, @01:11AM (#169488)

        Most cosmic rays probably do come from supernovae, but to get the Ultra High Energy regime, you need something like an active galaxy [arxiv.org].