Seeing Enterprise...

Relativistic spacecraft must interact with the cosmic microwave background in a way that produces a unique light signature.

Topics: CMB, Einstein, NASA, Relativity, SETI, Quantum Cosmology, Spaceflight, Spacetime

TECHNOLOGY REVIEW: Interstellar travel may be the stuff of science fiction but it’s straightforward to calculate that it should be possible given the ability to travel at a significant fraction of the speed of light. These kinds of speeds may even be achievable with near future technologies and the tax dollars to make them work.

There are significant challenges, of course. And today, Ulvi Yurtsever and Steven Wilkinson at the defense contractor Raytheon in El Segundo, California, outline another that seems to have been overlooked until now.

These guys point out that any object traveling at relativistic speeds will interact with photons in the cosmic microwave background. This interaction should create a drag that imposes specific limits on how fast spacecraft can travel, they say.

The movement of a relativistic spacecraft will have another effect. It should scatter the cosmic microwave background in a way that produces a unique signature. “As a baryonic spacecraft travels at relativistic speeds it will interact with the CMB through scattering to cause a frequency shift that could be detectable on Earth with current technology,” say Yurtsever and Wilkinson.

They go on to calculate the properties of this signature. They say the scattering should generate radiation in the terahertz to infrared regions of the spectrum and that this signal should move relative to the background. “The salient features of the signal are a rapid drop in temperature accompanied by a rapid rise in intensity, along with the motion of the source with respect to a reference frame fixed to distant quasars, which should be observable,” say Yurtsever and Wilkinson.

In other words, if relativistic spacecraft are zipping across interstellar space, this kind of signature should be visible using the current generation of astrophysical observatories.

That’s an interesting piece of work that takes the analysis of relativistic space travel to a new level. Other researchers have explored the possibility of observing relativistic spacecraft using the optical emissions that their engines must generate. But Yurtsever and Wilkinson go further.

Physics arXiv: Limits and Signatures of Relativistic Spaceflight
Ulvi Yurtsever, Steven Wilkinson