Imagine an advanced civilization somewhere in the universe, which has developed a particle accelerator that strikes electrons at the Planck Energy, the scale where gravity is to be described mechanically quantum. This energy scale is not an easy task for a collider, because it corresponds to ten quintillions (1019) times the resting mass of the proton. To achieve this energy with our existing acceleration technology would require a linear collider 10,000 light years in length.
But various concepts of plasma laser accelerators, on which I worked for my doctorate, can potentially shorten the required acceleration distance by a factor of 10,000, reducing the size of such a collider to the size of the Oort cloud that surrounds the solar system. And so, one could optimistically imagine that a very advanced civilization could generate collisions of electrons at Planck energies within its original planetary system.
It turns out that the hypothetical feasibility of such an experiment is a cause for concern for all civilizations in the universe. Let me explain.
Based on acceleration of expansion of the universe, we know that the void is not empty but has dark energy density. Planck energy particle collisions can trigger a local tunnel from vacuum to a lower energy state. The quantum transition between the two states may require high energies to overcome the barrier between the two states, as well as to produce a bubble large enough that the energy drawn from the increase in its volume exceeds the energy invested in the bubble. tension of its surface. This surface is reminiscent of the skin of a soap bubble, here blown by burning the âfuelâ of black energy inside.
Triggering the decay of the vacuum in a sufficiently large bubble at the collider location would produce an expanding combustion front, known as “domain wallBehind which the energy density of a vacuum will be converted into heat – much like a detonation wave burns through explosive material. This spherical hot front will move outward at the speed of light and release an unprecedented amount of energy into space, heating along its path. If all the dark energy is converted into heat, it would bring an unlimited volume swept by the scorching front to a temperature of 30 degrees above absolute zero, 10 times hotter and 10,000 times more energy dense than the radiation of the cosmic microwave background, left by the hot big bang.
Would such a heat wave be cause for concern? The bad news is that we wouldn’t be getting any warning until this cosmic catastrophe hits us in the face because no warning signal can travel faster than light to alert us to risk. But that might also be good news, as it implies that any resulting devastation would happen instantly and be as surprising as the Chicxulub impactor was to the dinosaurs. We would never know what hit us.
One way to avoid such a cosmic catastrophe is to establish an interstellar treaty, similar to the Nuclear Test Ban Treaty, first signed in 1963 by the governments of the Soviet Union, the United Kingdom and the United States. The objective of the “Planck Collider Treaty” would be to protect our cosmic environment from artificially produced domain walls. Without such a treaty, we would not want all civilizations to behave responsibly when they have acquired the technological maturity to build a Planck-energy collider. Hopefully our neighbors would show cosmic responsibility.
In the long run, the need to sign a treaty only squeezes our galaxy, the Milky Way, and its closest neighbor, Andromeda; it does not extend beyond the Local group galaxies. Even without a treaty signed or honored on extended intergalactic scales, the accelerated expansion of the universe will ultimately save us from the risk of a Planck collider disaster. All galaxies beyond “Milkomeda(The result of a possible merger between Milky Way and Andromeda, which my colleague TJ Cox and I named in a 2007 article) will eventually move back of us faster than light. As I showed in an article from 2002, once all the other galaxies leave our horizon of cosmic events, nothing that happens in them can affect us because all the causal signals propagate at most at the speed of light. Once the universe ages by another factor of ten, Milkomeda will only be surrounded by dark space.
The accelerated cosmic expansion will sweep away all of Planck’s risky colliders in distant galaxies far from us, ultimately protecting us from any accidents. This is another example of Mother Nature’s kindness to us. We are blessed with unmistakable social distancing on a cosmic scale. After all, a cosmic domain wall could be much more dangerous than COVID-19 because fundamental physics offers no escape from its scorching light-speed sweep.