Sunday 11 October 2020

The Same Old Face

"Flight to Forever."

The big surprise comes when Saunders recognizes the Moon:

 "Luna. The same old face - Luna!" (p. 286)

Before this, we knew only that the universe had reformed and that he was on an evolving planetary surface. He had traveled through the time when the Moon had fallen to Earth, then after the death of Earth, Sun and universe. Now we realize that he really is coming home despite his endless forward motion.

"The universe was mortal, but it was a phoenix which would never really die." (p. 285)

The old myth, later re-expressed in Tau Zero.

Newtonian: In each cycle, every particle starts with the same position and velocity.
Einsteinian: The continuum is spherical in four dimensions.
 
"...if you traveled long enough, through space or time, you get back to your starting point." (p. 287)
 
That sounds intuitively right. (I must look up a relevant passage in James Blish's Midsummer Century.) (Later: see here.) If the Earth were a perfect sphere, if light were refracted all the way around it and if we had a sufficiently powerful telescope, then we would see the backs of our own heads. If the continuum were a sphere, then we would need something other than light to see by. 

10 comments:

Sean M. Brooks said...

Kaor, Paul!

But I don't really believe that if I somehow traveled a billion years into the future I would somehow go backwards in time to the year AD 2020.

Ad astra! Sean

S.M. Stirling said...

It all depends on whether the universe is open or closed. The jury’s out — the most recent new evidence indicates it’s closed, but that isn’t conclusive.

Sean M. Brooks said...

Kaor, Mr. Stirling!

But I'm not sure it logically follows that if I went a billion years into the future that would somehow enable me to go backwards in time to my starting point.

Ad astra! Sean

paulshackley2017@gmail.com said...

Sean,

Of course that does not logically follow but the question is whether it can be theoretically and empirically established that space-time is spherical. It would not logically follow that traveling along a line of latitude would return you to your starting point if the Earth were not spherical.

Paul.

S.M. Stirling said...

Technically he hasn’t returned to his own time; he’s gone forward into another cycle of the universe which is identical to the last.

Sean M. Brooks said...

Kaor, Paul and Mr. Stirling!

Paul: Two different issues, then.

Mr. Stirling: But that's even less plausible than Saunders "circling time" to get back to "when" he started out from. He started out from Cycle A of the universe and then he should be thought of as ending up in Cycle B, a DIFFERENT universe from the one he left.

Ad astra! Sean

paulshackley2017@gmail.com said...

But I thought that, in this scenario, time was a literal circle. Hence, the Einsteinian description of the continuum as a 4D sphere.

Sean M. Brooks said...

Kaor, Paul!

And that was how I understood "Flight to Forever" when I read it and from your own comments.

Ad astra! Sean

S.M. Stirling said...

From the story I got the impression that the universe was fully symmetrical in all 4 dimensions; it expands, collapses, and re-expands indefinitely, with each cycle being an exact duplicate of the one before.

Sean M. Brooks said...

Kaor, Mr. Stirling!

And I can't buy such a notion. I would expect each cycle of such a collapsing and expanding universe to be different from predecessor cycles. I certainly don't expect US, and everybody else now live or dead, to be infinitely repeated.

Ad astra! Sean