I watched another YouTube video last night. This one was about the search for E.T., i.e. extraterrestrial life. One organization heavily involved in this research is SETI, which stands for Search for Extra Terrestrial Intelligence. SETI does this with huge dish antennae aimed at the stars. What they are looking for are radio wave patterns that might indicate a transmitter somewhere up there in the blue. This isn't easy, because space is already very noisy with radio waves, a virtual cacophony of background noise.
The universe is incredibly vast, huge beyond human comprehension. Many of the stars and constellations we see in the night sky are millions of light years away. What we are seeing is not how they look today, but how they looked millions of years ago. We are looking at the past.
If SETI detects transmissions from an intelligent presence somewhere in space, the transmission it receives may have been traveling through space for thousands or even millions of years. We may prove that "they" (E.T.) are out there, but due to the vast distances between us, we will never have a two-way conversation with them.
This brings up the question of E.T. visitations to earth -- the so-called UFO phenomenon. If aliens from space have been visiting earth, they would have had to come from far away, traveling hundreds or thousands of light years, to get here. If our understanding of the laws of physics are accurate, visitors from other star systems would be impossible, due to the distances involved.
This assumption, of course, is based on our current understanding of physics. Civilizations that are thousands of years more advanced than we may disagree. Their advanced technology may have found a way to traverse those incredible distances in a much faster way.
By the way, a light year is a measurement of distance. It is the distance that light travels in one year. Since light travels at 186,000 miles per second, a light year is 365.25 days x 24 hrs x 60 minutes x 60 seconds = 31,557,600 seconds in a year x 186,000 miles per second = 5,869,713,600,000 miles.
So a light year is a distance of 5.87 trillion miles, rounded off. Betty and Barney Hill reported that their alien abductors hailed from the star system called Zeta Reticuli, which is 39.17 light years from Earth. That's only a short hop by universe standards, but still an incomprehensible distance for human beings. It's 230 trillion miles.
How fast is the speed of light in miles per hour? It would be calculated as 186,000 x 60 x 60, or 669,600,000 miles per hour. Even so, if a radio signal were sent out from one side of our galaxy to the other, it would take around 100,000 years to make the trip.
(Damn, I love what you can do with Excel.)