"Jeffery" wrote in message
m...
Interstellar travel is impossible since it would take centuries or
millennia to reach other stars. Aliens are not going to spend 1000
years traveling to our star,

That only means that they shouldn't travel slowly. The effects of time
dilation imply that an alien can make a trip across the Milky Way Galaxy
(~100,000 light years in diameter) in an an arbitrarily small amouint of
time according to their onboard clock (including their bioligical "clocks")
if they travel close enough to the speed of light.

Also there are things like wormholes (if its possible to create one) and
warp drives (which may be theortically possible) that are now appearing in
the mainstream physics literature.

One needs to "think out of the box" for such travel.

There are two relevent journal articles that pertain to this

"Wormholes in spacetime and their use for interstellar travel: A tool for
teaching general relativity," Michael S. Morris and Kip S. Thorne, Am. J.
Phys. 56, 395 (1988)
****************************
Rapid interstellar travel by means of spacetime wormholes is described in a
way that is useful for teaching elementary general relativity. The
description touches base with Carl Sagan's novel Contact, which, unlike most
science fiction novels, treats such travel in a manner that accords with the
best 1986 knowledge of the laws of physics. Many objections are given
against the use of black holes or Schwarzschild wormholes for rapid
interstellar travel. A new class of solutions of the Einstein field
equations is presented, which describe wormholes that, in principle, could
be traversed by human beings. It is essential in these solutions that the
wormhole possess a throat at which there is no horizon; and this property,
together with the Einstein field equations, places an extreme constraint on
the material that generates the wormhole's spacetime curvatu In the
wormhole's throat that material must possess a radial tension 0 with the
enormous magnitude 0 ~ (pressure at the center of the most massive of
neutron stars) × (20 km)2/(circumference of throat)2. Moreover, this tension
must exceed the material's density of mass-energy, rho_o*c^2. No known
material has this T_o rho_o*c^2 property, and such material would violate
all the ``energy conditions'' that underlie some deeply cherished theorems
in general relativity. However, it is not possible today to rule out firmly
the existence of such material; and quantum field theory gives tantalizing
hints that such material might, in fact, be possible.
****************************
(Note: Thorne now thinks that such wormhole travel seems impossible)

"The interstellar traveler," C. Lagoute and E. Davoust, Am. J. Phys. 63, 221
(1995)
****************************
Abstract - We investigate the physics of an interstellar journey on board a
spaceship with a constant acceleration, in the framework of special
relativity. It is in principle possible to cross the Galaxy within a human
lifetime. The aspect of the sky seen from the spaceship is severely
distorted by relativistic aberration; most of the visible sky shrinks to a
small region of strongly enhanced luminance in the direction of motion,
leaving the rest of the celestial sphere almost entirely dark. The invisible
universe becomes perceptible by the traveler, as the infrared and radio
radiations are Doppler-shifted to visible frequencies in the direction of
motion. Navigational problems posed by these relativistic effects are
examined.
****************************

This is the proof of the nonexistence of UFOs. To claim otherwise is the
same as believing
in UFOs.

I have no opinion on that at this moment. But if I did believe in it then it
doesn't make me a bad person does it? :-)

However ... there was one time in 1980 when I was driving through the desert
in New Mexico ... but I have no idea what that was. But it was weird!

No matter what our technology, we'll never travel to other
stars except maybe nearby stars like Alpha Centauri which you could
reach in a few decades. Otherwise the distances are just too vast. You
just have no comprehension of interstellar distances.

Gee. I always thought I did!

If you claim
that aliens can travel to other inhabited worlds, then why not say
that an alien space craft crashed in Roswell, New Mexico in 1947?

Because a thing is possible does not mean that it happened. Back in 1980 it
was possible to wipe out almost all life on Earth. That of course didn't
mean that it happened. Perhaps we're not interesting enough or that nobody
has seen us since we became smart monkey's. That is a very short period of
time in the grand scheme of things. Perhaps aliens thought they'd check out
Earth 100,000 years ago and found nothing of interesting beyond the typical
wildlife which they see on all life sustaining planets


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