POD: Einstein gets a bit different idea about relation between 
gravity and time, and works out the greatest theory of his life, 
the Universal theory of chronogravity. As a consequence, there is 
now a theoretical possibility of time travel. And, as each 
theory, it needs to  be proved experimentally. 

1965, CERN: Group of physicists is preparing another 
chronogravity experiment. Poor Einstein died shortly 
before his theory has been proved for the first time. 

It is now becoming almost a routine, there were already six 
small, each of several grams, metal balls sent a minute or two 
into the past. It has been duly filmed, measured and archived how 
a ball suddenly appeared out of nothing on the experimental 
table, then it was carefully put aside, another(?) ball has been 
brought and put on the table and a  minute after the appearance 
of the _first_ ball the second one has been sent exactly one 
minute into the past. So, for one minute, there were two copies 
of the same ball, differing only in their age - but we leave the 
philosophical consequences of it to philosophers, and business 
consequences (see? we have these two balls of gold. This one is 
from the future. Originally, we had just one gold ball. Now we 
have too. Ugh.) to the businessmen. 
For now, the experiment is a bit different. Everyone is curious 
what happens if we change our mind and do NOT send the ball back 
to the past, so that we have now two balls forever. So, if the 
ball is not going to be sent back to the past, where does the 
other ball come from? Laws of causality and such. Not speaking 
about the laws of mass conservation. Einstein's equations do not 
seem to give answer to this. 

The experiment is prepared, as soon as the ball appears, a switch 
is flipped and the chronogenerator is turned off, thus disabling 
any possibility of sending the ball into the future. Curious 
experimentators wait one minute, closely observing the table. One 
minute passed, and nothing spectacular happens. As each 
experiment takes months to prepare, there will be some time to 
ponder over the result, and new experiments, hopefully clarifying 
the matter will follow. At least  the physicists think so. They 
do not know yet how wrong they are. 

It is not immediately visible, since the speed of light is 
not infinite, but the event hits suddenly when it comes. The second 
following night, many people just stare into the sky and do not 
believe their own eyes - the stars are gone. There is the Moon, 
the planets, the asteroids, an occasional comet, but nothing 
beyond that. 

During several following days, as most astronomers go crazy, at 
least some light is brought into the mystery. First of all, an 
unusually bright star appears just in the opposite direction of 
the Sun. Its spectral characteristics are exactly the same as of 
the Sun itself, and careful search reveals several orbiting 
bodies around the start, very embarrassingly reminding of Sun's 
planets. All in all, the puzzle seems to fit: the universe has 
now a diameter of just a light day or so, and is conveniently 
curved, so that what we are seeing is in fact the light from our 
Sun, as it travelled across the whole universe and returned back 
to its origin. 
Now as for the cause... data from several space probes suggest 
that a big sphere with Earth at its centre has been hit by this 
phenomenon, and radius of our mini universe is rather accurately 
measured. If we assume it all started on Earth, spread with the 
speed of light, until it stopped at the distance of one light 
day, where the light of stars was cut off, then we can pinpoint 
the origin of the Event with almost minute precision. Yes, it was 
the unfortunate time travel experiment. 

Of course, there is no explanation of the Event (as it is going 
to be called). Many different theories have been proposed, 
including - of course - crackpots speaking about a divine 
intervention, until several decades later one bright, 
wheel-chaired physicist named Hawking developed a theory that 
could (just could!) explain what happened. 
In short, removal of the cause from the effect left the universe 
with  disturbed law of causality. This made a big shakeup of the 
basic structure of timespace continuum, and as a result the local 
part of the universe folded up, creating our mini universe, thus 
effectively protecting the rest of universe from this ugly flaw 
in basic logic. It was all spreading along the gravitational 
field, causing chain reaction in Earth's  gravitational field, 
then jumping to Sun's one, and continuing while the gravity of 
the Sun was strong enough to support the reaction. As the energy 
released is proportional to the mass of object travelling through 
time and to the amount of time it travels through, we were really 
lucky we went with grams, not miligrams of matter. Otherwise 
mankind would be left on rapidly cooling Earth with no source of 
external energy. 

Incidentally, this rather nicely explains the Fermi paradox - 
each civilisation, after reaching certain technological level, 
discovers the chronogravity theory, conducts the experiment and 
locks itself out of our universe. Sometimes with their star, 
sometimes without. Often their space probes are left wandering 
through the interstellar space, sometimes their colonies on 
different planets of their star system survive a few years 
without a mother planet. But the theory is pretty simple, every 
civilisation is bound to discover it long before they can even 
dream of interstellar travel. 

Now what are going to be the effects on Earth? Mankind does not 
need the stars, except as a navigation aid, but there is already 
a compass for it, so direct effects are not so bad. 

However, the Event left a huge psychological impact on the 
attitude to science. It was clearly demonstrated that science has 
done something BAD, not just a puny nuclear device, but something 
that was directly capable of destroying the whole humanity. 
And no one dares to repeat any time travel experiments - rightly so, 
as Hawking predicted that repeat of the Even in such a small universe 
would most probably cause a vacuum phase transition back into 
energy dominated universe. 

And, while people do not need the rest of universe directly, it 
was a nice to know there are no frontiers - while we are not able 
to go to starts, and wouldn't be able to in many years (or even 
centuries), now there is a clearly defined limit for our 
expansion. We have just the Sun and the planets, nothing more. 
It is another think that we might never reach the stars anyway. Now 
we CANNOT, and we'll never be able to.