Have aliens ever visited Earth? Perhaps not scientist explain

by M.P. Pellicer | Stranger Than Fiction Stories
Has there ever been definite, incontrovertible proof that an alien race has visited earth? The answer is no, and researchers have a disturbing but plausible explanation why they haven't. 

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Fermi is said to have come up with the idea of the Fermi Paradox in a throwaway remark over lunch with colleagues in 1950 when he asked "Where is everybody?"

No doubt a civilization that could reach our planet would be advanced, but this very trait could have doomed them due to stagnation, or their collective death before they reached us.

The hypothesis suggests that a civilization with the technological advancement necessary to reach our solar system would reach an extinction event crisis, when the demand for energy outstripped its technological innovations. The choice would be simple, either end growth, which would include interstellar exploration in order to maintain equilibrium, or death.

The Fermi Paradox posed by Nobel Prize-winning physicist Enrico Fermi compares the immense age and size of the universe, which should have produced multiple life forms that would have visited us by now, or at least provided undeniable proof of their existence. However the reality is all the opposite, which points to a different version of alien visitation to Earth.

This paradox was described by the late British science-fiction author, Sir Arthur C. Clarke, who said: "Two possibilities exist: Either we are alone in the universe or we are not. Both are equally terrifying."

A new study arguing this point was published in the journal Royal Society Open Science. Michael Wong with the Carnegie Institution for Science and Stuart Bartlett of the California Institute of Technology wrote:

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​Civilizations either collapse from burnout or redirect themselves to prioritizing homeostasis, a state where cosmic expansion is no longer a goal, making them difficult to detect remotely. Either outcome — homeostatic awakening or civilization collapse — would be consistent with the observed absence of [galactic-wide] civilizations. We hypothesize that once a planetary civilization transitions into a state that can be described as one virtually connected global city, it will face an 'asymptotic burnout,' an ultimate crisis where the singularity-interval time scale becomes smaller than the time scale of innovation. This presents the possibility that a good many of humanity's initial detections of extraterrestrial life may be of the intelligent, though not yet wise, kind.

Maybe there's a reason why it's been so quiet at SETI

These scientists composed their hypothesis based on studies of the "superlinear" growth of cities. The study describes where cities increase in size, and thereby more energy consumption at an exponential rate in order to accommodate their growing population. This brings them to the crisis point where there is a crash, followed by an precipitous civilization-ending collapse if changes are not made.

If these alien races had any hope of surviving they would redirect their efforts away from unbounded growth, to one where they could be in harmony with its existing world(s) until the point where it ran into trouble. The researchers suggest that even though these space explorers would not abandon all efforts to visit other worlds, chances are they would not reach our planet. Their proposal also takes into consideration the challenge of interstellar travel, that aliens have kept their presence a secret or that ET arrived too early in the life of the universe for direct contact with humans.

Another hypothesis published in the Astrophysics Journal posits that the sheer size of the universe could take as long as 400,000 years for a signal to be received between advanced civilizations, and we haven't been around that long in order to receive the message.

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Despite different theories, no indisputable proof of alien existence or visitation has been provided

Different hypothesis about alien existence and visitation:

• Radio Silence: We might not be listening at the right frequencies or in the right way. 
• The Cosmic Timescale: Humanity has only been scanning the skies for a few decades — an eye blink in cosmic history.
• The Zoo Hypothesis: Aliens could be observing us like we observe animals in a nature reserve, choosing not to interfere.
• The Dark Forest Theory: Intelligent species stay silent to avoid detection by potentially hostile civilizations.
• The Great Filter: There is a nearly insurmountable barrier preventing civilizations from advancing. This could be at the stage of life’s emergence, intelligent life’s development, or a self-destructive phase like nuclear war or environmental collapse.
• Self-Limiting Civilizations: Advanced societies may become so technologically sophisticated that they lose interest in space expansion, opting for virtual realities or inward development.

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