2 hours ago, n4gix said:

Thanks to Einstein, we know that the faster you go, the slower time passes--so a very fast spaceship is a time machine to the future. Five years on a ship traveling at 99 percent the speed of light (2.5 years out and 2.5 years back) corresponds to roughly 36 years on Earth.

That sounds backwards. The faster you go, the slower your time passes so 1 second in your spaceship at 99.99999999% the speed of light would be 19.6 hours on Earth.

3 hours ago, n4gix said:

I've often wondered how the folks in Star Trek, Star Wars, et cetera magically avoid time dilation during their journey

 

In terms of Star Trek, it's a warp drive, so there would be no time dilation. The space ship itself doesn't move faster than light. It's the fabric of space time that does.

In terms of Star Wars, it's a hyper drive. So the ship slips into a higher dimensional realm where FTL is possible. 

The sad part... I thought the topic said Plan 9 or Black Hole.

Was going to go in depth about how bad Plan 9 was as a film, let alone a sci-fi film... and then point out that Black Hole was better, only because it was in color and didn't use three different actors for a main character... but... well, wrong topic.

 

Never mind!

1 hour ago, dmwalker said:

That sounds backwards. The faster you go, the slower your time passes so 1 second in your spaceship at 99.99999999% the speed of light would be 19.6 hours on Earth.

Not backwards at all.  You have to keep in mind what is relative to what.

The faster the spaceship (you) goes relative to Earth, the slower time  passes relative to Earth.

Just 1 day at that speed would equal 193.32 years back on Earth!

Nota Bene: Somehow I don't think the American Museum of Natural History would get their maths wrong!  

15 minutes ago, WarpD said:

The sad part... I thought the topic said Plan 9 or Black Hole.

I can't say I've watched either one of 'em, so I'll just take your opinion for my own. 

1 hour ago, martin-w said:

In terms of Star Trek, it's a warp drive, so there would be no time dilation. The space ship itself doesn't move faster than light. It's the fabric of space time that does.

In terms of Star Wars, it's a hyper drive. So the ship slips into a higher dimensional realm where FTL is possible. 

The ST method is similar then mechanically to what the Navigators did mentally in Dune: folding space. Except the Navigator's method was nearly instantaneous. Much more efficient!

SW's 'hyper drive' is similar to the method used in the Star Kingdom of Manticore (Honor Harrington) by entering successively higher dimensional bands. Whenever they didn't have a handy wormhole gate handy that is.

36 minutes ago, n4gix said:

Just 1 day at that speed would equal 193.32 years back on Earth!

My mistake was that I didn't see that Einstein was on the spaceship. I suppose I couldn't imagine a newborn baby being put on a spaceship.

Anyway I apologise to the American Museum of Natural History.

 

8 hours ago, n4gix said:

The ST method is similar then mechanically to what the Navigators did mentally in Dune: folding space. Except the Navigator's method was nearly instantaneous. Much more efficient!

 

Frank Herbert didn't really explain how his drive functioned, but as its folding space and instantaneous travel, it seems to have features of worm hole travel to me. Like a flat piece of paper with two points drawn on it. Fold the paper and you can connect the two points, and the connection between the two would be a worm hole. Herbert's drive isn't going to make sense really, as I say, he just conjured it up without any real scientific explanation behind it. 

Warp Drive, or the Alcubierre drive, is about creating a warp bubble around the space ship. Its based on Einstein's field equations. Its an energy field around the spaceship that has lower density than that of the vacuum. It requires negative energy and unfortunately we have no idea if such a thing exists. The Casmir effect is sometimes said to be an example of negative energy but then others say its akin to but not really negative energy. The other issue is the amount of energy required, its quite frankly huge, although new calculations have reduced it. Then there are issues like needing to seed the path to our destination first with negative energy, so at sub light speeds, thus making the entire concept pointless. Not being able to control the warp bubble from inside, you would need to do so from outside the warp bubble. The huge amount of energy released when you dropped out of warp which would destroy your destination planet. Intense radiation the crew would be subjected to. The requirement for a force filed to prevent minuscule clumps of space dust obliteration your warp ship.  So yes, don't expect a warp drive any time soon. 🙂 

 

8 hours ago, n4gix said:

SW's 'hyper drive' is similar to the method used in the Star Kingdom of Manticore (Honor Harrington) by entering successively higher dimensional bands. Whenever they didn't have a handy wormhole gate handy that is.

 

Yep, the fictional idea of crossing space via an alternate dimension called hyperspace. There is a more scientific version of hyperspace though, as in the higher dimensional space of M-Theory.

Edited April 9, 20215 yr by martin-w

8 hours ago, dmwalker said:

My mistake was that I didn't see that Einstein was on the spaceship. I suppose I couldn't imagine a newborn baby being put on a spaceship.

Anyway I apologise to the American Museum of Natural History.

 

 

Tricky thing time dilation. The point to remember is that its relative to the observer. You on your spaceship at relativistic velocities would experience time passing at the normal rate. Its the guys observing you from Earth that would see you at almost a standstill. 

Lorentz contraction is another mind twister. At relativistic velocities distances contract. Travel at just under the speed of light to a nearby galaxy and despite the fact it may be 25.000 light years way, you would get there much faster than in 25,000 years. In fact you could arrive in just a few years, dependant on your velocity. Good luck trying though, you would gain inertial mass and require almost infinite energy. And at light speed you would have infinite mass and require infinite energy. Such things are reserved for massless particles. 

5 hours ago, martin-w said:

you would gain inertial mass and require almost infinite energy.

So, if you could travel at speeds approaching light speed and looked out of the window, would the entire universe appear proportionally smaller? 

Also, to travel at close to light speed,  how much time would be required to accelerate to light speed and to decelerate at the other end?

It seems that space travel at any fraction of light speed is not practical because, at lower speeds, it would take decades to reach the nearest star and, at higher speeds, tens of thousands of years would elapse on Earth.

3 hours ago, dmwalker said:

So, if you could travel at speeds approaching light speed and looked out of the window, would the entire universe appear proportionally smaller? 

 

No. Gaining inertial mass is nothing to do with size. Even a car traveling down the highway at 70 MPH gains inertial mass. Its minuscule and you couldn't measure it but gain in mass it surely does. Any particle with mass gains inertial mass as it accelerates to any speed and at the speed of light the mass is so great it would be infinite. Thus, its impossible for an object with mass to travel at the speed of light. It would also require an infinite amount of energy to accelerate to that speed, so again, its impossible.

 

3 hours ago, dmwalker said:

Also, to travel at close to light speed,  how much time would be required to accelerate to light speed and to decelerate at the other end?

 

Well its not possible so not really a valid question. But accelerating to any speed is dependant on the net force acting on that object. As the force increases so does the acceleration. So the answer, if it were possible, is its depends on the force you apply to the object. 

Only massless particles can travel at the speed of light. And when they do, some pretty bizarre things happen. For example, because photons travel at light speed, time and distance do not exist for them. As soon as they are emitted they are at their destination. 

 

3 hours ago, dmwalker said:

It seems that space travel at any fraction of light speed is not practical because, at lower speeds, it would take decades to reach the nearest star and, at higher speeds, tens of thousands of years would elapse on Earth.

 

Well no, not true for any fraction of light speed, we can certainly travel at fractions of light speed. But the closer we get to light speed the more energy is required. If it were possible for something with mass to travel at light speed, then Lorentz contraction comes into play and it doesn't take as long to get there as you might think. 

45 minutes ago, martin-w said:

But accelerating to any speed is dependant on the net force acting on that object

In this case, the object of concern would be humans so I imagined an acceleration of 2g might be the limit while seated and less than 2g if they have to move around. Also, I should specify a more feasible speed than light speed, so perhaps 90% or 50%, for example.

After posting this, I found a reference which stated that to accelerate at 3 g's to half the speed of light would take two and a half months. 

Edited April 9, 20215 yr by dmwalker

22 minutes ago, dmwalker said:

I should specify a more feasible speed than light speed

 

A plasma rocket (Vasimr Rocket) could reach 123,000 mph. A Thermo-Nuclear rocket could get us to mars in 100 days. A solar sail should be able to reach a maximum speed of 10% of the speed of light. 

1 hour ago, martin-w said:

we can certainly travel at fractions of light speed.

I should have said that I am still referring to travel to the nearest star. So, however fast the spaceship is, by the time it reaches the nearest star, hundreds or thousands of years will have elapsed on Earth, so any information sent back would be much too late to be of any use, assuming it were possible to send information over such a distance.