Generally speaking however, when talking about "generations" as a generic measure of time, a benchmark of 20 years equals 1 generation seems to be a common consensus.
SWS
What people have wondered is how traits are inherited from one generation to the next.
Most probably quarks, since everything in the universe except light is made of it.
Radioactivity is since creation of universe.
Well, since the end of the Universe is constantly expanding, and since it would depend on how fast you are going, it could take 1 year to 10000000000000000000000 years or more. There is also very little evidence that the Universe actually has an ending.
The following statement seems to have been true about the Universe since Man became aware of it: "It's larger than was previously thought."
since the beginning of the universe/earth.
Helium is has been in existence since the beginning of the universe.
there are the energy that mostly makes up this universe and its had been here since the beginning of the universe and also they are invisible.
I don't think anybody proposed the laws of gravity. The laws of gravity have existed since the beginning of time and the beginning of the universe.
21 generations
"Earthling", or, since it would amazingly impossible for an identical human species to form somewhere else in the universe, "Human"
People feel the need to explain the beginning of the universe because understanding our origins can provide a sense of purpose, meaning, and direction in our lives. Additionally, it helps us make sense of our existence and the world around us.
No. He discovered hydrogen and oxygen, but those elements have been around since pretty much the beginning of the universe.
No, because time is a function of the Universe and is subject to mass, location, velocity and other physical phenomena. Time began with the Universe and when the Universe as we know it ends (and it will end since it had a beginning) time will cease.
What people have wondered is how traits are inherited from one generation to the next.
The universe is expanding.
What people have wondered is how traits are inherited from one generation to the next.