# Re: [humanism-174] Space travel according to Victor Stenger

 From: Tim C. Sent on: Friday, April 26, 2013 4:09 PM
Well, if this artificial gravity is based on "g" forces, the ship is always accelerating (or decelerating). Therefore, the gravitational "push" is coming from the direction in which the ship is heading (like the g forces you feel when your car is accelerating.  But remember that in your car, you also have the counter force of Earth's gravity so that you feel the acceleration, but also feel oriented toward the surface of Earth.  That gravity is not present in space, so the only force you would feel is that acceleration force.  And it has to be constant or your body will catch up to the speed and you would feel no gravity at all!.   They would always feel the direction in which they were heading as "up", and the direction from which they were coming as "down".  So you would want to design your ship so that your travellers would always have their gear and chairs and tables and all that stuff oriented to match the up/down orientation we have here on earth!  In other words, the ship would need to be designed like an elevator!  Only outside of the ship, the "top" of the elevator would be the bow of the ship! See?

T

In a message dated 4/26/2013 4:02:37 P.M. Eastern Daylight Time, [address removed] writes:
Tim, I don't get why it would have to be built aiming up?  I am trying to picture this...

On Fri, Apr 26, 2013 at 3:30 PM, Tim Campbell wrote:
Yes, and worse, under this idea of constant acceleration, the ship would have to be built in such a way that it was always aiming "up".  This sort of orientation might become tiresome after a while!  Like being in an eternal elevator!

Tim

In a message dated 4/26/2013 2:41:26 P.M. Eastern Daylight Time, [address removed] writes:
N
ow that is cool, Rick.  I see what you are saying there, but if they are talking about slowing down, how is it that it takes 7 years to get to the half way point, BUT it will still be 7 years to reach the destination if you slowed down at the halfway point?

I hope I worded that right.

Eeeek!  I think I actually understand my own question! ha

On Fri, Apr 26, 2013 at 2:36 PM, Rick wrote:

It's the acceleration.  He's saying that the force of the acceleration would make "down" the direction of the engines as a consequence of the whole equal and opposite reaction business.
You accelerate at 32 feet per second squared (1g) until you hit the halfway point.  Then you have to spend the rest of the trip slowing back down.  So, you turn the ship around and decelerate at 32' per sec sq, and it will continue to feel like 1 gravity.
The only time you're weightless is at the turn around because that's the only point when your velocity is constant.  Easy.

In a message dated 4/26/2013 1:27:44 P.M. Eastern Daylight Time, [address removed] writes:
I'll jump on someone's shoulders to see ya Tim! ha

Again, my head is spinning without layman terms, but what does this mean:

Of course, the ship can't continue to accelerate, since it needs to be moving at the same speed as the planet when it arrives. When it reaches the halfway mark at 600 light-years from Earth, the crew turns the ship around so it then decelerates at one g for the remainder of the trip. Those onboard notice no change. They continue to experience the equivalent of gravity on Earth.

I don't get it....

To be honest, I am not certain what he is talking about here either!  "One g" is basically the gravitational force that we feel here on Earth.  We use our "g" as the reference point for gravity anywhere else in the universe! If you weigh 100 pounds on earth, then on a planet with a gravity of 2g you would weigh 200 pounds, and so on.

But g forces have nothing to do with speed or acceleration once you are in space.  Once you have escaped earth's gravitational force, you would be essentially weightless unless your ship did something to give you an artificial gravity.  We see science fiction concepts of space stations being wheels for this reason. It is guessed that the wheel shape would be spun so that the centrifugal force would create a kind of gravity for the inhabitants.

I understand that he is positng a speed high enough to utilize the relativistic effects on time, but in order for a 2400 year trip to take 14 years in astronaut time, the ship must be coming very close to the speed of light.

The orientation of the ship would have nothing to do with the acceleration or deceleration or on-board gravity. however, if the speed is changing, then that change WILL have an effect on the relativistic effect as well.

Until a speed of appr 670 MILLION MILES PER HOUR is technically feasible, any journey to another solar system will involve either multiple generations or some form of suspended animation/hybernation for the crew.

Of course, I will be discussing this in detail in July!

Tim

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