stop an object moving in a vacuum instantaneously

**flopsies** · July 23, 2012, 06:46 PM

Is there some way, even a theory, that would allow an object in space, ie a starship, traveling incredibly fast, and then reach its destination, and stop?

**~~removeduser_4536284751384~~** · July 23, 2012, 08:26 PM

The ship could thrust in the direction it is travelling with enough force to stop it almost instantly. There are plenty of external means that could be set up in orbit around the destination planet to stop the ships. However, coming to a stop instantaneously is not advisable, that's called crashing. Through momentum everything inside the ship would carry on at close the speed the ship was travelling initially and slam into the front of ship. Decelerating from interstellar speeds to 0 in a few seconds would kill everyone on board and probably destroy the ship, or at least everything inside it. Think of what happens when you brake suddenly in a car, you fell like you are being thrown forward and stuff can go flying forward.

It would be safer to slow down over a long time period. The most efficient method of travel would be the ship accelerating for the first half of the journey and decelerating at the same rate for the second half. Although if one of those can be done faster than the other, it needn't be half and half.

**Aanker** · July 24, 2012, 02:17 AM

Put a massive planet of solid diamond at the end of the trajectory. The starship will guaranteedely stop.

**Magicman2051** · July 24, 2012, 02:41 AM

Assuming that "incredibly fast" is a speed measured using light years as a reference point then the answer is no.

Moving away from theory and into speculation however there are some ideas knocking around. For instance, if you could create a region of extremely concentrated particle bombardment (preferably all going in the direction of the approaching vessel

) and then design the ship itself to have these particles act upon it and then reflect back to the origin point only to be reflected back again and again then correct calibration would mean that while the ship would eventually reach a point whereby the stream of particles acting upon it and (hopefully) slowing it down becomes constant and sufficient to slow it down very fast.

But as Deb correctly pointed out, you'd get thrashed. Now if you could bend the laws of physics to your will then maybe, otherwise you're better off with the method previously described.

**Sphere** · July 24, 2012, 06:07 PM

First off, the people inside the ship are Welsh, so screw them. Nobody cares.

Second ... anti-gravity

Third, profit.

**Gaidin** · July 24, 2012, 08:01 PM

Originally Posted by Sphere

First off, the people inside the ship are Welsh, so screw them. Nobody cares.

Second ... anti-gravity

Third, profit.

Fourth, ????

Fifth, Society changes!

**Timefool** · July 24, 2012, 06:35 PM

I heard of a theory awhile ago that to avoid the problem of dying from the momentum of deceleration, you could move the entire universe while you stay stationary. But then the problems of your deceleration shift from you to the entire universe.

**Sphere** · July 24, 2012, 06:47 PM

Inertial dampers.

Problem solved.

**Magicman2051** · July 24, 2012, 07:26 PM

Magic.

Problem solved.

**Phier** · July 24, 2012, 08:35 PM

Originally Posted by flopsies

Is there some way, even a theory, that would allow an object in space, ie a starship, traveling incredibly fast, and then reach its destination, and stop?

Just set that ship as the point of reference. Therefore it has stopped but its the Universe that is in fact moving.

I heard of a theory awhile ago that to avoid the problem of dying from the momentum of deceleration, you could move the entire universe while you stay stationary. But then the problems of your deceleration shift from you to the entire universe.

Ok I just read this and someone was actually serious about this?

**~~removeduser_4536284751384~~** · July 24, 2012, 09:36 PM

Originally Posted by Phier

Just set that ship as the point of reference. Therefore it has stopped but its the Universe that is in fact moving.

I think it's obvious he meant relative to its destination.

Originally Posted by Phier

Ok I just read this and someone was actually serious about this?

I'm pretty sure he wasn't being too serious.

**Phier** · July 24, 2012, 09:49 PM

Originally Posted by irelandeb

I think it's obvious he meant relative to its destination.

**Aanker** · July 25, 2012, 02:32 AM

For what purpose, though?

If you want to be a lawful citizen of our universe and stay below the speed limit, you will have to make the same acceleration and deceleration as everybody else, meaning a longer journey than if just travelling with constant velocity at, say, 99% of the speed of light between two points. That is the price we pay for realism.

However, if it is at all possible to arrive at a point in the universe before light does, that would be through wormholes or some other fanciful explanation that has no evidence and is in fact entirely speculative, but nonetheless stays marginally within science. In which case the spaceship could simply move through the entrance of the wormhole at low speed and come out at low speed (relative to the wormhole, which in turn, of course, could be moving relative to your destination). In such a case, a device to rapidly reduce the speed of the spaceship would be unnecessary.

**Nikitn** · July 25, 2012, 03:55 PM

OP: Not according 2 classical physics, but perhaps according to that fancy modern einstein stuff which I haven't (properly) learned yet.

Just set that ship as the point of reference. Therefore it has stopped but its the Universe that is in fact moving.

If you're starting to play that game, it would be technically incorrect to say the universe is just "moving". More like the universe's position is moving in comparison to the spaceship.

**Elfdude** · July 25, 2012, 04:59 PM

Hmm... maybe?

The ways I can imagine to do it would be via wormholes, if you simply alter space time around you then there's no need to worry about the momentum because you never had any to begin with. On the other hand an inertial dampener which alters the effects of mass/gravity at will we could similarly ignore the momentum. Hypothetically if you distrubted the force evenly upon stoping across the atoms of the object and the vehicle you could still impart the force but not destroy the object that it's impacting. Classically there's no way because to accomplish that with 0 time would require infinite energy but that's in a closed system and does not take into account the ability to control the laws, alter them, or distribute them in a controlled manner.

**~~removeduser_4536284751384~~** · July 25, 2012, 06:37 PM

Originally Posted by elfdude

On the other hand an inertial dampener which alters the effects of mass/gravity at will we could similarly ignore the momentum. Hypothetically if you distrubted the force evenly upon stoping across the atoms of the object and the vehicle you could still impart the force but not destroy the object that it's impacting.

Ok, that could probably work on some kind of unmanned bulk cargo space ship, but what abouta human body?

Originally Posted by elfdude

Classically there's no way because to accomplish that with 0 time would require infinite energy but that's in a closed system and does not take into account the ability to control the laws, alter them, or distribute them in a controlled manner.

Well I assume "instantly" is "a very short time" rather than "0 time".

**Elfdude** · July 25, 2012, 07:59 PM

Ireland if it was distributed atomically it wouldn't matter what the substance was. If it was distrubted along the same vector at the same rate it wouldn't cause any damage at all.