Interesting video. Well explained. With constant thrust, travel around the solar system is a matter of days.

 

 

I have constant thrust!  What else is new?

Going "fast" is only half of the equation. Deceleration will insist on taking the other half of the equation!  😄

1 hour ago, n4gix said:

Going "fast" is only half of the equation. Deceleration will insist on taking the other half of the equation!  😄

 

Yep. Thrust half way then flip and burn.

2 hours ago, charliearon said:

I have constant thrust!  What else is new?

 

Yes, Charlie. And we know from which orifice. 

5 hours ago, martin-w said:

we know from which orifice.

... We have ignition...

Hook

8 hours ago, LHookins said:

... We have ignition...

Hook

 

Nuclear thermal propulsion, nuclear electric, VASIMIR rockets, matter antimatter drives..... nothing can compare with Charlie's vindaloo curry powered fart drive. 

 

I saw a youtube video about time, in which if you travelled at an acceleration of 1G for 10 years (would feel just like gravity if facing the right way!), the slowed down for 10 years, then turned around and again accelerated at 1G, followed by another 10 years slowing down, you'd arrive back at earth 40 years later, but due to the different passage of time on your ship, and earth (Special relativity), 50,000 years will have passed on earth. Not sure how I could check it's true, but seemed a respectable source.

44 minutes ago, Overload said:

I saw a youtube video about time, in which if you travelled at an acceleration of 1G for 10 years (would feel just like gravity if facing the right way!), the slowed down for 10 years, then turned around and again accelerated at 1G, followed by another 10 years slowing down, you'd arrive back at earth 40 years later, but due to the different passage of time on your ship, and earth (Special relativity), 50,000 years will have passed on earth. Not sure how I could check it's true, but seemed a respectable source.

 

Yep. Correct Time dilation. Lorentz Contraction is another interesting phenomenon, in that distance contracts with velocity, so at close to light speed your destination is much closer. In fact you could cross the galaxy in very little time at close to light speed, but a colossal amount of time would have passed back on Earth. 

On 3/12/2025 at 9:24 AM, Overload said:

if you travelled at an acceleration of 1G for 10 years

But 1G for 10 years would not yield a peak velocity of 3 million km/sec, i.e., 10 times the speed of light? That's using classical mechanics. All I know of relativity (apart from E=mc²) is that speed of light is constant. Or did I miscalculate something?

38 minutes ago, Luis Hernandez said:

But 1G for 10 years would not yield a peak velocity of 3 million km/sec, i.e., 10 times the speed of light? That's using classical mechanics. All I know of relativity (apart from E=mc²) is that speed of light is constant. Or did I miscalculate something?

A mass can't travel through space at the speed of light.  It can get very close, but never attain that speed.  The reason, according to the equation, is that mass becomes infinite at the speed of light, which means that it simply cannot happen.

I still believe that faster than light travel is possible by manipulating space itself as opposed to accelerating through it.  How to do this, I don't know.

Dave

Thanks, Dave. I knew that mass could never go faster than light, but I never knew why...until your explanation.

From the point of view of the people on a spaceship travelling at near the speed of light, they are stationary and it's the universe moving past them at near the speed of light. You get to figure out what this would look like to them.

A trip to a likely inhabitable star system 20 light years away would still take 25-30 years (someone check my math) for an observer on Earth, but it would be somewhat less to the people on the ship. I don't have the math to calculate this properly. It would appear to the passengers of the ship as if they were operating under Newtonian physics and the rest of the universe was distorting in their favor.

I'm not going to try to estimate how much energy this would take to accelerate for years at 1 Gee.

If you think about it, a 30 year trip each way is quite doable.

Hook

 

 

Edited March 13, 20251 yr by LHookins

On 3/12/2025 at 8:13 AM, martin-w said:

 

Yep. Correct Time dilation. Lorentz Contraction is another interesting phenomenon, in that distance contracts with velocity, so at close to light speed your destination is much closer. In fact you could cross the galaxy in very little time at close to light speed, but a colossal amount of time would have passed back on Earth. 

I remember a sci-fi story about twins who were telepathic and were contracted by the government to act as communications during a long-distance exploration of star systems. One of the twins stayed on Earth while the other traveled on the exploration starship.

I don't remember the exact details since reading this novel some decades ago, but the end result was that while the twin on the starship only aged twenty or so years, the twin remaining on Earth was close to death by the time the starship returned to Earth. The younger twin got to meet his brother who lay dying in a hospice, but also his many adult nieces and nephews!

I believe that the late great Robert Heinlein was the author.

3 hours ago, Luis Hernandez said:

But 1G for 10 years would not yield a peak velocity of 3 million km/sec, i.e., 10 times the speed of light? That's using classical mechanics. All I know of relativity (apart from E=mc²) is that speed of light is constant. Or did I miscalculate something?

 

As Dave said, the faster you travel the more inertial mass you gain. You would have infinite mass at the speed of light, thus not possible to achieve light speed. Even driving down the motorway you would have more mass than if stationary.

Time would also slow to a standstill from an observers perspective.

If a train emits a beam of light forward while traveling at 30mph, the speed of the light beam still travels at lightspeed, not plus 30mph. The variable is time, time slows for the moving train and the speed of the light beam stays at lightspeed.

As I mentioned earlier, distance contracts and becomes zero at lightspeed, so in essence, a photon is at its destination the instant it's emitted in zero time.

 

 

Edited March 13, 20251 yr by martin-w