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Old June 12th 20, 02:04 PM posted to alt.astronomy
Sjouke Burry[_2_]
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Default No Confirmed UFOs Ever So Far - perhaps long lived

On 12.06.20 14:37, Porcospino wrote:
On 2020-06-11, casagiannoni optonline.net wrote:


Nothing in physics or engineering prevents it, more so for a spacefaring
civilizations which, you'd assume, can command enough energy to do this
at little relative expense (without any breakthrough in physics).



As i've stated, even at near light speed, which is extreemly unlikely, travel
times would be prohibitively long.

Do the simple math. Distance = Speed x Time !


It might be prohibitively long for an individual, but it doesn't have to
be for a /species/. With a laser sail design that's reasonable from the
point of view of a 'spacefaring' civilization (with settlements in its
own star system, an industrial presence, etc.) you could perhaps reach
Alpha Centauri within thirty years, and your civilization could slowly
hop from one nearby star to the next. At ~0.15c crossing the Galaxy
would take a bit more than one million years. Even if you assume that
these hops only happen once every century, that's 100 million years.

This might seem 'prohibitively long' to you, but there are stars that
have existed for /billions/ of years, and it's possible that
technological civilizations could be just as long-lived (jellyfish have
existed on Earth for half a billion years - I'm confident that an
intelligent species might do the same, especially if space colonization
enables it to overcome the limitations of its environment).

As a last point, you allowed for "near light speed". While that's
physically possible I'm less confident it would feasible from an
engineering point of view, even for an advanced spacefaring species. But
since you brought it up, I'll mention this.
The 'opposite side' of the galaxy, 200k light years away, would take at
least 200k years to reach in a single trip (the simple math that you
love). That, of course, is well beyond the endurance of any known living
being (and presumably of any automated ship you could build). However
you forgot about relativistic time dilation: even if we assume that the
craft has to slowly accelerate at 1 g until it reaches its peak speed,
and then has to decelerate until its destination, from the frame of
reference of its crew the whole trip would take less than 25 years.
Even if there's no going back and it's an absurd proposition (since a
slow expansion makes a lot more sense than cutting all ties with your
home planet and choosing to settle a star on the other side of the
galaxy), it shows that travel time is no obstacle.

At any reasonable speed, you will be barbecued slowly by alfa, beta and
gamma
radiation.
I dont think living beings can survive.
One SF book I read, used self-replicating space probes.
When they passed a star system, they started mining, and produced
replica-probes, sending those in all directions.
That grows exponentially, and after a few millennia, their corner of the
galaxy
was covered with probes.
If they detected life, send back probes loaded with that info.
For a longe-lived species, that works, and you dont have to leave home.