Re: Here's one for Bob (hope it makes your head spin)

In article <9356a$46e41375$cef8887a$19776@xxxxxxxxxxxx>, JF Mezei <jfmezei.spamnot@xxxxxxxxxxxxx> writes:
david20@xxxxxxxxxxxxxxxx wrote:

Travelling there faster than light is a physical law problem.


I see people breaking the law every day, they go faster than the speed
limits :-)

Seriously, I fully understand that a particle accelerator would not be
able to accelerate a particle to faster than speed of light. The
propulsion is based on a static item (the magnets or whatever) which
remain at speed 0 whilst they accelerate the particle. First, the energy
that is transfered from the static item to the particle may not be able
to travel faster than light, and second, there is the theory it will
require an infinite amount of energy.

HOWEVER, if you are on a self propelled ship, going 1km/h below the
speed of light, is there really something stopping you from increasing
throttle to go to 1 km/h above speed of light ?

You can add 1 km/h in the ship's frame of reference. No problem.
But that doesn't add 1 km/h in a frame of reference where the ship
is already moving near c.

There's a relativistic velocity addition formula that applies.

vf = (vi + vd)/(1 + vivd/c^2)

Where

vf is final ship velocity in some rest frame,
vi is initial ship velocity in that same rest frame
vd = delta v in the ship frame

In the case of a self propelled ship, The water you would eject from a
H2 O2 engine would be going at a slow speed relative to the ship, just
enough to accelerate the ship a little bit more. Furthermore, the water
would be at relatively the same energy level as the ship and thus, if it
takes a huge amount of energy to accelerate the ship by 1 km/h,
accelerating the water from the ship would also generate a huge amount
of energy.

From a hand-waving point of view, there are indeed huge quantities getting
thrown around in a rocket moving near the speed of light.

Hand waving does not substitute for calculations.
Huge does not substitute for infinite.
.

Relevant Pages

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