More than most people who do not understand a little bit about algebra would ever guess; so I am going to answer the above question in this blog.
Introduction and background
My degree is in Engineering Physics and I have always been fascinated by space and astronomy and communications. I was a licensed amateur radio operator at 17 and my amateur radio knowledge of the frequency spectrum coupled with my degree in physics guided me in my investigation into the possibilities of interstellar space communications using simple algebra!
So let start with the basic algebra (ten minutes at most).
x = distance units (meters, miles, kilometers it does not make any difference in algebra as long as one uses consistent units)
t = time (seconds, hours, days, years)
Velocity = x/t e.g. (x meters/t sec)
That is all the algebra you need to know!
Here is all the Physics needed:
The velocity of light has a special name c which replaces v; therefore c = x meters / t seconds
c = 300,000,000 meter/sec or 186,000 miles / sec is a universal constant
As large as the speed/velocity of light c is; due to the distance to stars and galaxies, we must know how far light travels in a year -not a second!
The reasons will become obvious later.
Here is the conversion:
One year (in seconds)=365days *24 hours/day *60 minutes/hour * 60 seconds/minute = 31,536,000 seconds
Question! What is the distance light travels in one year?
If you cannot calculate it based on the information given above here is the answer:
By definition x=v*t but for light, we use c instead of v by convention, and therefore x=c*t
Or in miles; distance light traveled in one year x=186,000 miles / sec*31,536,000 sec = 5,865,569,600,000 mile
Wikipedia ˜5878625 million miles˜63241.1 astronomical units (au)
1 au is distance from sun to earth; and is about 93,000,000 miles. OK! We know have all the basic information we need; let’s apply it to the practical matter of communication times to star.
The nearest known star (other than the Sun), Proxima Centauri, is about 4.22 light-years away.
The center of our galaxy, the Milky Way, is about 26, 000 light-years away.
The Milky Way is about 100000 light-years across.
The Andromeda Galaxy is approximately 2.5 000 000 light-years away.
If you are following me so far -note these are one way distances so you would have to double the times for round trips.
Since we earthlings have been transmitting g from about 1920 our signals have traveled at most 92 years in time and 92 light years in distance.
Conclusion: we are not even close to our radio/TV signals reaching stars in 99% our Milky Way; therefore if there are any other planets, in the Milky Way, with intelligent life; they can't possibly know we exist.