geckzilla wrote: ↑
Thu May 10, 2018 6:38 pm
tomatoherd wrote: ↑
Thu May 10, 2018 4:40 pm
bystander wrote: ↑
Thu May 10, 2018 4:00 pm
Space-time is 4D. 3D Space plus time.
No bystander, that's not what is meant by 4D. Not the way Chris and others are herein using it. They mean 4D space alone, with or without time. "hyperspheres and tesseracts" and all that.
Space is time. Just stop trying to separate them, and it'll make more sense. Or less.
This is how I visualize it. It may be right, it may be wrong.
This is Ötzi, the iceman.
He was found in the Ötzal Alps on the border between Austria and Italy in 1991. He is Europe's oldest natural mummy, and he was alive some 5,000 years ago.
I think of Ötzi as a man who has been traveling on "spaceship Earth" for about 5,000 years. He was alive for only about 45 of those years, but his death didn't prevent his body from continuing his journey on spaceship Earth.
The Earth is "dragged along" in space by the Sun, which is moving at 72,000 kilometers per hour
(45,000 miles per hour). Let's see. There are 24 hours in a day, which means that the Sun moves 1,728,000 kilometers in a day. Then there are 365 days in a year, which means that the Sun moves 630,720,000 kilometers per year, or almost 631 million kilometers per year, if I did the math right. Allow the Sun to travel at that speed for five thousand years, and it will have moved some three trillion, one hundred and fifty-three billion, six hundred million kilometers through space. And dragged the Earth along with it.
My figures may be correct, or not. But it is true without a shadow of a doubt that the Sun has dragged the Earth along a vast distance since Ötzi was alive on the Earth.
Here is my point. We can't travel back in time and meet Ötzi when he was alive, or visit the Earth at the time when Ötzi was alive. But crucially, we also can't travel back in spacetime
and visit the 4D region in the Universe in which Ötzi was alive. Theoretically at least, we could indeed travel to the general region of space through which the Earth was moving when Ötzi was alive. But if we managed to locate that region in space and travel there, we would find that the Earth would not be there. It would have moved more than a trillion kilometers away from the 4D location in spacetime where Ötzi was alive.
Ötzi's mummified body exists in the same geographic location and time frame as we do, but he was alive in a 4D spacetime that is inaccessible to us. The spacetime coordinates of the Earth that he lived on are out of reach for us forever.