Where is everybody enrico fermi

Step outside on a clear night and gaze up at the night sky. Depending on the sky conditions where you live, you may see as many as 2, stars. So where are all the aliens? While SETI includes everything from listening for radio signals to examining odd fluctuations in starlight , theoretical work in the field has been dominated by two key concepts: the Fermi paradox and the Drake equation.

So where are they? Since the s, humans have walked on the moon, sent a probe beyond our solar system, and even sent an electric sports car into orbit around the sun for fun. If we can go from rudimentary wooden tools to these feats of engineering in under a million years, surely there would have been ample opportunity in our And then, surely there would be some lingering radio signals or visual clues of their expansion reaching our telescopes. The Drake equation was only intended as a rough tool to stimulate scientific discussion around the probability of extraterrestrial life.

Take L, the average lifespan of a detectable civilization. If the Romans, Incas, or Egyptians are anything to go by, it seems hard to make it past a few hundred years. On the flip-side, you could argue that once a civilization becomes technologically advanced enough to achieve interstellar travel, it could conceivably last many billions of years.

This enormous uncertainty leaves the Drake equation ultimately vulnerable to the optimism or pessimism of whoever wields it. And this is reflected in previous scientific papers whose results give values of N ranging anywhere from 10 to many billions. Sincere attempts to overcome this vulnerability have previously been made via selecting a handful of conservative, medium, and bullish best estimates for each parameter value and then taking an average across them.

This is because simply selecting a few point estimates and plugging them into the Drake Equation misrepresents the state of our knowledge.

As an example, imagine three scientists who have differing opinions on the value of L:. Therefore, the researchers represented the full range of possible values on a logarithmic scale and ran millions of simulations to obtain more statistically reliable estimates for N. They then applied a technique known as a Bayesian update to those results. That means mathematically incorporating the information that we have not discovered extraterrestrial intelligence yet because the absence of evidence of aliens is evidence itself!

This implies that life as we know it is incomprehensibly rare, and if other intelligences exist, they are probably far beyond the cosmological horizon and therefore forever invisible to us. As new information becomes available, they would update that likelihood accordingly.

Three: Intelligent life is abundant—but quiet. This possibility, known as the zoo hypothesis, invites some of the strangest speculation. Or maybe those other civilizations have learned that broadcasting their existence leads to extermination at the hands of violent, intergalactic colonizers.

Or maybe our solar system just happens to be located in a quiet, exurban cul-de-sac of the universe, an accident of cosmic geography. But none of these theories hold a candle to my favorite conjecture of all: slumbering digital aliens. But humankind may have a unique system of mathematics that ET cannot understand. Problem: then where are their incomprehensible signals? Catastrophes Civilizations only have a limited lifetime, They are all dead. Problem: Sun is average star, if other stars formed a million years ahead of us, then They would be a million years ahead of us in technology.

In other words, this is an important problem to solve in the hope that it is 1 and not 2. Very little experimental evidence for our current view of the structure of the Universe, so we depend on our sense of beauty. Where beauty here does not imply aesthetics, but rather conciseness, economy of concepts, brevity of mathematical expression, breadth of application. Central to the beauty of our theories of how the Universe works is symmetry as expressed by Neother's theorem, a statement that for every continuous symmetry there exists a conservation law.

Invariance of the laws of Nature to spatial translation, temporal translation and rotation means conservation of energy, mass and angular momentum. CP violation shows us that the Universe is chiral, a fancy word that means parity or handy-ness.

So the Universe does distinguish between left and right handed interactions, Nature looks different in a mirror. Finding symmetries in a theory is important. By finding symmetries that a theory does not possess, a broken symmetry, is even more important. When dealing with particles and their interactions, global symmetry makes no sense why should the behavior of particles here on Earth have any effect on observations of particles on distant stars.

Instead we restore symmetry through the use of a gauge field, a field that carries the information of symmetry around the Universe. For example, by demanding that electromagnetism obey local gauge symmetry we are forced to accept the existence of electromagnetic fields and the massless gauge boson is the photon. Similar requirements on all quantum fields produces quantum electrodynamics QED. Objects in uniform motion or acceleration must also obey the laws of Nature, thus imposing local symmetry on motion forces a new field, the gravitational field described by general relativity, to appear.

The Standard Model is incomplete as it does not specify the values of fundamental constants nor does it combine with gravity.