Could special relativity be caused by aliens jamming the Solar System?

The Copernican principle

As L.Dutch pointed out, this would violate the Copernican principle, which essentially states that there's nothing special about observing the universe from any one place. Granted, this is not easy to test, as we humans only sit in one tiny portion of the cosmos. However, it's possible that the Copernican principle is incorrect, and tests have been devised and, in some cases, carried out:

• Observing distant supernovae can tell us whether we live in a large underdensity (Clifton et al. 2008)
• That same underdensity would influence our observations of the cosmic neutrino background (Jia & Zhang 2008)
• Unexpected changes in the Hubble constant at different redshifts would indicate that we on Earth are privileged observers (Uzan et al. 2008)
• Future radio telescopes could test our assumptions of cosmological homogeneity and isotropy (Schwarz et al. 2015)

. . . and so on and so forth. Most of these are not related to the problem at hand, but any positive result would indicate that the Copernican principle may be wrong. It's still quite possible that this is the case. I don't think many astronomers subscribe to that view, but it's not yet out of the question.

Consequences

I'm going to stick to the cosmological effects of this sort of change, and what we'd see on Earth. The immediate consequence is that the night sky would, for a short while, turn mostly black.

Consider two photons from a distant star, traveling towards Earth. One is emitted just before the jamming begins, and therefore reaches Earth instantaneously. The other is emitted just after the jamming begins; it travels instantaneously to the edge of the Solar System, but then takes a time $\tau=r/c$ to reach Earth, where $r$ is the radius of the jamming region. The Solar System is large (the Oort Cloud is arguably a light-year or two in radius), so it would take about a year or two for the second photon - or any other photons emitted just after the jamming began - to reach Earth. But in that intervening time, there would be no stars in the night sky on Earth.

We would also notice that light from all sources outside the Solar System would arrive at the same time. That is, light from a source 10 parsecs away would arrive at the same time as light from a source 100 parsecs away. This is because it only takes them a time $\tau=r/c$ to reach Earth; outside the Solar System, the light travels infinitely fast. We'd have many of the astronomical consequences we would get in a universe where there's no speed limit:

• No redshift of sources beyond the Solar System, as $z=0$ when $c\to\infty$.
• As a consequence of the above Olber's paradox would no longer hold: the sky would be bright, as it would hold light from all of the objects in the (presumably infinite) universe.
• We would see distant galaxies as they are, not as they used to be.
• Gravitational waves would travel instantaneously fast, as they travel at the same speed as light - which is now, outside the Solar System, infinity.

• Spectroscopy is either out the window or severely modified. I'm not sure if you could build a self-consistent model of electromagnetism, let alone electronic or molecular transitions, so spectral lines are likely right out.

• Even in the event that lines are produced, most broadening mechanisms (e.g. pressure broadening, thermal broadening) and line diagnostics wouldn't exist because of the aforementioned lack of redshift and therefore the Doppler effect.

What this means for science, from an observational perspective:

• We can no longer use distant supernovae to measure the expansion of space.
• We can't use the radial velocity method to detect exoplanets.
• Determining galactic rotation curves would be exceedingly difficult, if not impossible.

• Early-universe cosmology is suddenly almost impossible, as we can't see protogalaxies in the earliest stages of formation.

• Without spectroscopy as we know it, determining the composition of celestial objects is extraordinarily difficult, if not impossible.

All of this is just the tip of the tip of the tip of the iceberg. In other words, you can throw the majority of astronomy and cosmology right out the window - that is, if the infinite speed of light doesn't make things like stars and fusion impossible, and there's still an outside universe to observe.

posted almost 4 years ago

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