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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 HiThere on Saturday April 11 2015, @07:08PM

    by HiThere (866) Subscriber Badge on Saturday April 11 2015, @07:08PM (#169037) Journal

    I don't think a wormhole would leave a detectable signal in the middle. There is the problem that it takes a lot of negative mass to stabilize it, though. (Or is that mass with negative energy?) And I'm not sure what you mean by "space bending" singe I don't think you mean "artificial gravity" which if used to propel the spaceship would leave an identical trail to any other propulsion method...though granted each propulsion method has a few special characteristics of its own.

    FWIW, my idea of the best way to do interstellar space is a generation ship...except that thinking of it as a ship is wrong. Instead think of it as a mobile habitat. That way you don't need any huge amount of power (anything that gets you into the region of time dilation is horribly expensive) and you don't need to reach any particular destination at any particular time. You live by browsing off of free planets, asteroids, etc. You *do* need controlled fusion and a well regulated nearly closed ecosystem. (You *might* be able to do this with fission, but it's iffy.)

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  • (Score: 2) by kaszz on Saturday April 11 2015, @07:30PM

    by kaszz (4211) on Saturday April 11 2015, @07:30PM (#169043) Journal

    Space bending is that you contract space ahead of your ship and expand it behind you. And the ship itself remains static inside a bubble.

    Your are probably right about the wormhole. No detection signature in mid path.

    Overall there might be signs of intelligent activities however which in itself would be interesting. If the scientific community wouldn't limit themselves to radio waves only.

    • (Score: 2) by boristhespider on Saturday April 11 2015, @10:18PM

      by boristhespider (4048) on Saturday April 11 2015, @10:18PM (#169111)

      No-one limits to themselves to radio waves! I'm not sure where that idea comes from. Any astronomer wants to cover as much of the spectrum as we possibly can! Gamma ray bursts are a nice example of an intriguing problem that comes up because telescopes (initially spy telescopes, entertainingly, but followed up with astronomical telescopes once the Americans and Russians were convinced they weren't trying to kill each other) observe in gamma rays. Vast amounts of astronomy is even now done in optical, galactic physics relies to a large extent on infra-red (since it can see past the typical dust grains, whose size is such that they fuck up optical observations), then obviously we also need radio wave astronomy even though without massive interferometers the resolution is diabolical, and my own field in cosmology relies to a vast degree on microwave observations.

      Frankly what we want is all-sky surveys in every single wavelength. Realistically, we're never getting that. But mass surveys in the microwave (such as Planck), along with mass surveys in radio (such as SKA will bring) and mass surveys in the IR/optical (such as SDSS) along with whatever we can glean in the X/gamma ray regime, gives us good leverage, especially as in these broad fields we can also observe in narrower frequency bands.

      • (Score: 2) by kaszz on Saturday April 11 2015, @10:29PM

        by kaszz (4211) on Saturday April 11 2015, @10:29PM (#169117) Journal

        I meant searching for high energy particles (perhaps low ones too?) and other types of energy forms not ordinarily thought of as a means of radiation from objects in the universe. Perhaps there a fields that warps the properties of atoms in other ways. Neutrinos are also interesting from this point of view but also notoriously hard to catch.
        (gravity is monitored by LIGO so it's covered)

        • (Score: 2) by boristhespider on Saturday April 11 2015, @10:38PM

          by boristhespider (4048) on Saturday April 11 2015, @10:38PM (#169119)

          The X and gamma ray observatories are meant to catch the high-energy events, and the microwave and radio surveys should catch practically all the low-energy ones. It's quite hard to come up with something that will emit in these ranges that doesn't have some signal on the CMB, and the CMB is extremely well observed...

          But yes, we can always do with more observations, ideally from space so we don't drown ourselves in interference from Jersey Shore and The Only Way is Essex (and the Sun, of course), and across as many frequency ranges as we can hit.

          We'd also love to see the cosmic neutrino background. Alas, as you point out, the chances of doing so are extremely slender.