This is from Varactacap:
>There's enough matter in interstellar space to power a starship to more than
>1.0c.
Nope. In principle, one could use various forms of ram acceleration to
asymptotically approach c, but one would never quite reach c. This is
demonstrated every day at every large accelerator in the world. If you want to
revoke special relativity, you have to come up with something a lot more clever
than simple acceleration.
>accelerate the resulting neutrons to near 1.0c using the energy of
>the ahnialated electrons and positrons, and you can theoritically exceed 1.0c.
Again, nope. You cannot "theoritically" exceed c in this (or any other)
manner. "Theoritically", you cannot exceed c. All attempts to construct a
self-consistent theory that does so have failed to date.
Andy Steinberg (aka dracula) wrote this bit:
>Nuclear power as used in Voyager and Cassini is very safe, especially when
>compared to a theoretical starship design called Orion, which could reach 0.3c
>by jettisoning nuclear bombs a distance behind itself and riding the shock
>waves. This would leave long trails of highly radioactive material everywhere
>Orion goes, in essence causing massive pollution of outer space.
I don't know anything about the details of this particular idea. But that last
sentance is a *real* howler! Space is BIG. There is absolutely NOTHING we can
do to cause "massive pollution of outer space." As an example, suppose the
entire Earth was pure uranium. Now let's suppose we take that 1 Earth mass of
uranium, and distribute it evenly in a column of one Earth radius, that goes
from the Sun to alpha Centauri. The mass of the earth is
M_e = 6 x 10^27 grams (more or less).
Where the 10^27 means 10 to the 27th power. The radius of the earth is
R_e = 6 x 10^8 cm (again, more or less)
The distance to alpha Centauri is ~4.2 light-years. Given c = 3 x 10^10 cm/sec
that give a distance of
D = 4 x 10^18 cm (from here to alpha Cen)
The volume of a cylinder is V = pi * r^2 * L, where pi=3.14159...., r is the
radius of the cylinder, and L is it's length. So for a cylinder with the
Earth's radius, and a length equal to the distance from here to alpha Cen, the
volume is
V = 5 x 10^36 cubic cm.
So if we took our Earth mass of uranium, and spread it out uniformely over such
a volume, that would create a volume density of
Density = 1.2 x 10^-9 grams/cc
Of course, since this stuff would be spewed out of an engine, it would quickly
disperse to much lower densities. And the earth is hardly pure uranium.
Whether or not the Orion idea makes any sense is another issue. But let's keep
a little perspective here. The entire Earth is a flyspeck when you start
talking about the scale of interstellar space.
Andy also made the following comment:
>3. There is nothing that says we can't go faster than light, we just
>can't go at the speed of light. . . .
I beg to differ. There is a HUGE scientific literature that says we can't go
faster than the speed of light. That may not be correct, but it is simply
false to say that there is no work on the topic. Again, there has been NO
self-consistent theory proposed that allows faster than light travel. And it's
not for lack of effort either.
-Your friendly neighborhood rainbow astronomer,
Paul