Collecting my ideas here.

Assuming 50% conversion of potential energy to kinetic energy.

Controlled space warp for faster than light – no.
Wormholes for faster than light – no.
Quantum tunnelling for faster than light – possible but don’t do it.
High relativistic speed – need a trillion-fold decrease in antimatter price.
Relativistic speed with black hole rather than antimatter – no.
Breakthrough-starshot at 20% of the speed of light – no.
3% of the speed of light – needs H to He fusion technology, which has a big problem
2% of the speed of light – possible but needs He3 + D fusion technology, which is technically feasible

Stopping. These speeds assume no fuel is required to stop at destination.
You can use fuel to stop the spacecraft at it its destination. I don’t know which is better.
If not using fuel to stop, jettison unwanted parts of spacecraft & slow down by running through a star.

mollwollfumble said:

Collecting my ideas here.

Assuming 50% conversion of potential energy to kinetic energy.

Controlled space warp for faster than light – no.
Wormholes for faster than light – no.
Quantum tunnelling for faster than light – possible but don’t do it.
High relativistic speed – need a trillion-fold decrease in antimatter price.
Relativistic speed with black hole rather than antimatter – no.
Breakthrough-starshot at 20% of the speed of light – no.
3% of the speed of light – needs H to He fusion technology, which has a big problem
2% of the speed of light – possible but needs He3 + D fusion technology, which is technically feasible

Stopping. These speeds assume no fuel is required to stop at destination.
You can use fuel to stop the spacecraft at it its destination. I don’t know which is better.
If not using fuel to stop, jettison unwanted parts of spacecraft & slow down by running through a star.

High relativistic speed is great if you can achieve it, because of length contraction.
The 4.376 light year trip to alpha Centauri takes just six months at 99% of the speed of light and 2.4 months at 99.9% of the speed of light.

mollwollfumble said:

Collecting my ideas here.

Assuming 50% conversion of potential energy to kinetic energy.

Controlled space warp for faster than light – no.
Wormholes for faster than light – no.
Quantum tunnelling for faster than light – possible but don’t do it.
High relativistic speed – need a trillion-fold decrease in antimatter price.
Relativistic speed with black hole rather than antimatter – no.
Breakthrough-starshot at 20% of the speed of light – no.
3% of the speed of light – needs H to He fusion technology, which has a big problem
2% of the speed of light – possible but needs He3 + D fusion technology, which is technically feasible

Stopping. These speeds assume no fuel is required to stop at destination.
You can use fuel to stop the spacecraft at it its destination. I don’t know which is better.
If not using fuel to stop, jettison unwanted parts of spacecraft & slow down by running through a star.

If cost wasn’t the deciding factor in antimatter production could it be scaled up to be useful as energy source

Stopping.. looxury.. worry about that when you get there :)

Cymek said:

mollwollfumble said:

Collecting my ideas here.

Assuming 50% conversion of potential energy to kinetic energy.

Controlled space warp for faster than light – no.
Wormholes for faster than light – no.
Quantum tunnelling for faster than light – possible but don’t do it.
High relativistic speed – need a trillion-fold decrease in antimatter price.
Relativistic speed with black hole rather than antimatter – no.
Breakthrough-starshot at 20% of the speed of light – no.
3% of the speed of light – needs H to He fusion technology, which has a big problem
2% of the speed of light – possible but needs He3 + D fusion technology, which is technically feasible

Stopping. These speeds assume no fuel is required to stop at destination.
You can use fuel to stop the spacecraft at it its destination. I don’t know which is better.
If not using fuel to stop, jettison unwanted parts of spacecraft & slow down by running through a star.

If cost wasn’t the deciding factor in antimatter production could it be scaled up to be useful as energy source

I think so.

First be aware of the different types of antimatter. Positrons and antiprotons are the two main ones. Making and storing positrons is a snap, but they’re not very heavy and take up a lot of room. Making and storing antiprotons is not easy, but I’d be very interested in how much the price can drop for mass production. One possibility is storing antiprotons in a sea of positrons.

Now, for using it, there has to be some sort of gamma ray reflector or absorber in use to get propulsive power out of it. There are good X ray reflectors but I don’t know of gamma ray reflectors, so you want a gamma ray absorber and an electromagnetic recoil damper around the intersection point of matter and antimatter.

Both the absorption and recoil damper drive the spacecraft.

mollwollfumble said:

High relativistic speed is great if you can achieve it, because of length contraction.
The 4.376 light year trip to alpha Centauri takes just six months at 99% of the speed of light and 2.4 months at 99.9% of the speed of light.

I don’t understand how this could be.

Could you please explain this in a simple manner to this dumb geologist?

If possible, please use words of one syllable or less.

Michael V said:

mollwollfumble said:

High relativistic speed is great if you can achieve it, because of length contraction.
The 4.376 light year trip to alpha Centauri takes just six months at 99% of the speed of light and 2.4 months at 99.9% of the speed of light.

I don’t understand how this could be.

Could you please explain this in a simple manner to this dumb geologist?

If possible, please use words of one syllable or less.

MV, surely you’ve heard of time dilation and length contraction under relativistic speeds? The Lorentz equations?

sibeen said:

Michael V said:

mollwollfumble said:

High relativistic speed is great if you can achieve it, because of length contraction.
The 4.376 light year trip to alpha Centauri takes just six months at 99% of the speed of light and 2.4 months at 99.9% of the speed of light.

I don’t understand how this could be.

Could you please explain this in a simple manner to this dumb geologist?

If possible, please use words of one syllable or less.

MV, surely you’ve heard of time dilation and length contraction under relativistic speeds? The Lorentz equations?

Sure, I’ve read of that stuff, but I can’t say I understand.

Michael V said:

mollwollfumble said:

High relativistic speed is great if you can achieve it, because of length contraction.
The 4.376 light year trip to alpha Centauri takes just six months at 99% of the speed of light and 2.4 months at 99.9% of the speed of light.

I don’t understand how this could be.

Could you please explain this in a simple manner to this dumb geologist?

If possible, please use words of one syllable or less.

I don’t think I can do better than the WP article, with particular focus on the Velocity effects section.

https://en.m.wikipedia.org/wiki/Time_dilation

And this article is about various experiments, using atomic clocks aboard aircraft, that confirmed the kinematic and gravitational time dilation effects.

https://en.m.wikipedia.org/wiki/Hafele%E2%80%93Keating_experiment

dv said:

Michael V said:

mollwollfumble said:

High relativistic speed is great if you can achieve it, because of length contraction.
The 4.376 light year trip to alpha Centauri takes just six months at 99% of the speed of light and 2.4 months at 99.9% of the speed of light.

I don’t understand how this could be.

Could you please explain this in a simple manner to this dumb geologist?

If possible, please use words of one syllable or less.

I don’t think I can do better than the WP article, with particular focus on the Velocity effects section.

https://en.m.wikipedia.org/wiki/Time_dilation

And this article is about various experiments, using atomic clocks aboard aircraft, that confirmed the kinematic and gravitational time dilation effects.

https://en.m.wikipedia.org/wiki/Hafele%E2%80%93Keating_experiment

Thanks. I’m reading and glazing over. I’ll read more soon.

I think the bit I don’t get is:

If it takes light 4 years to get somewhere,

How it can be done in 2 months, travelling under the speed of light?

Michael V said:

dv said:

Michael V said:

I don’t understand how this could be.

Could you please explain this in a simple manner to this dumb geologist?

If possible, please use words of one syllable or less.

I don’t think I can do better than the WP article, with particular focus on the Velocity effects section.

https://en.m.wikipedia.org/wiki/Time_dilation

And this article is about various experiments, using atomic clocks aboard aircraft, that confirmed the kinematic and gravitational time dilation effects.

https://en.m.wikipedia.org/wiki/Hafele%E2%80%93Keating_experiment

Thanks. I’m reading and glazing over. I’ll read more soon.

I think the bit I don’t get is:

If it takes light 4 years to get somewhere,

How it can be done in 2 months, travelling under the speed of light?

Only for the people on board the craft isn’t it, outside its four years, it weird that’s for sure

Michael V said:

dv said:

Michael V said:

I don’t understand how this could be.

Could you please explain this in a simple manner to this dumb geologist?

If possible, please use words of one syllable or less.

I don’t think I can do better than the WP article, with particular focus on the Velocity effects section.

https://en.m.wikipedia.org/wiki/Time_dilation

And this article is about various experiments, using atomic clocks aboard aircraft, that confirmed the kinematic and gravitational time dilation effects.

https://en.m.wikipedia.org/wiki/Hafele%E2%80%93Keating_experiment

Thanks. I’m reading and glazing over. I’ll read more soon.

I think the bit I don’t get is:

If it takes light 4 years to get somewhere,

How it can be done in 2 months, travelling under the speed of light?

Key point is that distance, time elapse, speed are relative.

For us here on earth, the journey of the ship will appear slower than the speed of light: it will take more years than light would.

For those aboard, the distance is contracted, and the time elapsed is less.

dv said:

Michael V said:

dv said:

I don’t think I can do better than the WP article, with particular focus on the Velocity effects section.

https://en.m.wikipedia.org/wiki/Time_dilation

And this article is about various experiments, using atomic clocks aboard aircraft, that confirmed the kinematic and gravitational time dilation effects.

https://en.m.wikipedia.org/wiki/Hafele%E2%80%93Keating_experiment

Thanks. I’m reading and glazing over. I’ll read more soon.

I think the bit I don’t get is:

If it takes light 4 years to get somewhere,

How it can be done in 2 months, travelling under the speed of light?

Key point is that distance, time elapse, speed are relative.

For us here on earth, the journey of the ship will appear slower than the speed of light: it will take more years than light would.

For those aboard, the distance is contracted, and the time elapsed is less.

So, taking that to the (impossible) n’th degree does this mean:

If we could travel at the speed of light, the distance would be zero and the travel would be instantaneous?

Michael V said:

dv said:

Michael V said:

Thanks. I’m reading and glazing over. I’ll read more soon.

I think the bit I don’t get is:

If it takes light 4 years to get somewhere,

How it can be done in 2 months, travelling under the speed of light?

Key point is that distance, time elapse, speed are relative.

For us here on earth, the journey of the ship will appear slower than the speed of light: it will take more years than light would.

For those aboard, the distance is contracted, and the time elapsed is less.

So, taking that to the (impossible) n’th degree does this mean:

If we could travel at the speed of light, the distance would be zero and the travel would be instantaneous?

In the limit yes

Michael V said:

dv said:

Michael V said:

Thanks. I’m reading and glazing over. I’ll read more soon.

I think the bit I don’t get is:

If it takes light 4 years to get somewhere,

How it can be done in 2 months, travelling under the speed of light?

Key point is that distance, time elapse, speed are relative.

For us here on earth, the journey of the ship will appear slower than the speed of light: it will take more years than light would.

For those aboard, the distance is contracted, and the time elapsed is less.

So, taking that to the (impossible) n’th degree does this mean:

If we could travel at the speed of light, the distance would be zero and the travel would be instantaneous?

Yes, for the person doing the travelling. Their mass would also be infinite, so you’d be called a real fay fuck.

If you had a spacecraft moving at a decent fraction of the speed if light communicating with the Earth at the speed of light and you showed actual clocks from both locations how would each see the others.

As you approach light speed your mass also comes under the Lorentz equations so your mass tends towards infinity as you approach c. This makes it a bit harder to accelerate as the force also has to approach infinity. :)

sibeen said:

As you approach light speed your mass also comes under the Lorentz equations so your mass tends towards infinity as you approach c. This makes it a bit harder to accelerate as the force also has to approach infinity. :)

Almost infinite.

dv said:

Michael V said:

dv said:

Key point is that distance, time elapse, speed are relative.

For us here on earth, the journey of the ship will appear slower than the speed of light: it will take more years than light would.

For those aboard, the distance is contracted, and the time elapsed is less.

So, taking that to the (impossible) n’th degree does this mean:

If we could travel at the speed of light, the distance would be zero and the travel would be instantaneous?

In the limit yes

Thanks.

sibeen said:

As you approach light speed your mass also comes under the Lorentz equations so your mass tends towards infinity as you approach c. This makes it a bit harder to accelerate as the force also has to approach infinity. :)

And I guess, that means there isn’t enough energy in the universe to provide that acceleration.

Michael V said:

sibeen said:

As you approach light speed your mass also comes under the Lorentz equations so your mass tends towards infinity as you approach c. This makes it a bit harder to accelerate as the force also has to approach infinity. :)

And I guess, that means there isn’t enough energy in the universe to provide that acceleration.

Yeppers :)

sibeen said:

Michael V said:

sibeen said:

As you approach light speed your mass also comes under the Lorentz equations so your mass tends towards infinity as you approach c. This makes it a bit harder to accelerate as the force also has to approach infinity. :)

And I guess, that means there isn’t enough energy in the universe to provide that acceleration.

Yeppers :)

I think what I was missing was that from the point of view of the people in the spacecraft at those speeds it would take that time.

It may have been implied, but moll wasn’t explicit about that.

sibeen said:

Michael V said:

dv said:

Key point is that distance, time elapse, speed are relative.

For us here on earth, the journey of the ship will appear slower than the speed of light: it will take more years than light would.

For those aboard, the distance is contracted, and the time elapsed is less.

So, taking that to the (impossible) n’th degree does this mean:

If we could travel at the speed of light, the distance would be zero and the travel would be instantaneous?

Yes, for the person doing the travelling. Their mass would also be infinite, so you’d be called a real fay fuck.

No, relativistic mass is old school. momentum increases not rest mass.

https://www.youtube.com/watch?v=LTJauaefTZM

Michael V said:

sibeen said:

Michael V said:

And I guess, that means there isn’t enough energy in the universe to provide that acceleration.

Yeppers :)

I think what I was missing was that from the point of view of the people in the spacecraft at those speeds it would take that time.

It may have been implied, but moll wasn’t explicit about that.

Surely you’ve heard of the relativistic twins problem?

One twin travels really, really fast; the other doesn’t. The one that hasn’t travelled is much older than the travelling twin.

sibeen said:

Michael V said:

sibeen said:

Yeppers :)

I think what I was missing was that from the point of view of the people in the spacecraft at those speeds it would take that time.

It may have been implied, but moll wasn’t explicit about that.

Surely you’ve heard of the relativistic twins problem?

One twin travels really, really fast; the other doesn’t. The one that hasn’t travelled is much older than the travelling twin.

It explains that movie, Danny Devito aged more

sibeen said:

Michael V said:

sibeen said:

Yeppers :)

I think what I was missing was that from the point of view of the people in the spacecraft at those speeds it would take that time.

It may have been implied, but moll wasn’t explicit about that.

Surely you’ve heard of the relativistic twins problem?

One twin travels really, really fast; the other doesn’t. The one that hasn’t travelled is much older than the travelling twin.

Yes, I have.

Michael V said:

sibeen said:

Michael V said:

I think what I was missing was that from the point of view of the people in the spacecraft at those speeds it would take that time.

It may have been implied, but moll wasn’t explicit about that.

Surely you’ve heard of the relativistic twins problem?

One twin travels really, really fast; the other doesn’t. The one that hasn’t travelled is much older than the travelling twin.

Yes, I have.

https://www.youtube.com/watch?v=noaGNuQCW8A

twin paradox by the same guy as the other video on “relativistic” mass

There is a precedent of a federal official (Secretary of War) being impeached after leaving office, and the provisions in the constitution covering the two offices are similar, so it might be hard to mount a defence that a president can’t be impeached after leaving office.

dv said:

There is a precedent of a federal official (Secretary of War) being impeached after leaving office, and the provisions in the constitution covering the two offices are similar, so it might be hard to mount a defence that a president can’t be impeached after leaving office.

i think you have mixed your FoR.

JudgeMental said:

dv said:

There is a precedent of a federal official (Secretary of War) being impeached after leaving office, and the provisions in the constitution covering the two offices are similar, so it might be hard to mount a defence that a president can’t be impeached after leaving office.

i think you have mixed your FoR.

It’s all relative.

sibeen said:

JudgeMental said:

dv said:

There is a precedent of a federal official (Secretary of War) being impeached after leaving office, and the provisions in the constitution covering the two offices are similar, so it might be hard to mount a defence that a president can’t be impeached after leaving office.

i think you have mixed your FoR.

It’s all relative.

only if you say uncle.

JudgeMental said:

dv said:

There is a precedent of a federal official (Secretary of War) being impeached after leaving office, and the provisions in the constitution covering the two offices are similar, so it might be hard to mount a defence that a president can’t be impeached after leaving office.

i think you have mixed your FoR.

So you see, the US voting public were travelling at 0.9c and got over Trump much faster than Congressional Republicans did.

JudgeMental said:

dv said:

There is a precedent of a federal official (Secretary of War) being impeached after leaving office, and the provisions in the constitution covering the two offices are similar, so it might be hard to mount a defence that a president can’t be impeached after leaving office.

i think you have mixed your FoR.

LOLOL

Nice one!

:)

Special Relativity and the Twin Paradox

Cymek said:

Michael V said:

dv said:

I don’t think I can do better than the WP article, with particular focus on the Velocity effects section.

https://en.m.wikipedia.org/wiki/Time_dilation

And this article is about various experiments, using atomic clocks aboard aircraft, that confirmed the kinematic and gravitational time dilation effects.

https://en.m.wikipedia.org/wiki/Hafele%E2%80%93Keating_experiment

Thanks. I’m reading and glazing over. I’ll read more soon.

I think the bit I don’t get is:

If it takes light 4 years to get somewhere,

How it can be done in 2 months, travelling under the speed of light?

Only for the people on board the craft isn’t it, outside its four years, it weird that’s for sure

Hi MV. It’s amazing how many SciFi authors don’t get this either. And futurists.

It’s officially called the twin paradox. If one twin stays on Earth and the other takes a spaceship to the stars and back, when they arrive back together, the twin who’s taken the trip to the stars arrives back younger than the twin who stayed on Earth.

Perhaps you can think of it this way. Light doesn’t age (ie. photons don’t age). According to someone sitting on a beam of light, they can travel as far as they like and never age. That means that according to someone sitting on a beam of light, it takes no time at all to fly across the whole universe. It also means that, to someone sitting on a beam of light, the universe is as flat as a pancake – distances to everything are negligible along the line of flight. In special relativity, it’s not just time that depends on how fast you’re going, it’s also distance. To a person on Earth, the distance to alpha Centauri is 4.367 light years. To a person travelling at 99% of the speed of light, that distance is 0.623 light years. To a person travelling towards alpha Centauri at 99.9% of the speed of light, the distance to alpha Centauri is 0.198 light years. That’s Fitzgerald contraction and is part of the Lorentz equations.

From the point of travel to stars, what matters is shipboard time. Shipboard time is how long the missions need to be stocked with food for. Shipboard time is how long the recycling has to run for. Shipboard time is how long the instruments degrade for. Shipboard time is how long the crew members get on each others nerves.

So shipboard time at 99.9% of the speed of light to alpha Centauri is shipboard time for a distance of 0.198 light years, which is only 0.198 years = 2.37 months.

There once was a young man named Fisk,
With fencing exceedingly brisk,
So fast was his action,
Fitzgerald contraction,
Foreshortened his foil to a disk.
(and tunneled with flicks of the wrist).

Please don’t ask me to explain the twin paradox in terms of general relativity.

I just did a calculation for how much acceleration/deceleration a large frozen cell (eg. human zygote/embryo) could take before fracturing.

Ballpark estimate 3 trillion times the acceleration due to gravity = 3*10^13 m/s^2.

Calculation details – indirect tension, tensile strength of ice assumed 1 MPa.
Compressive force at 1.5*10^-2 Newtons.
Mass of cell is only 0.5*10^-15 kg.
Acceleration = force over mass.

Stop from 2% of the speed of light = 0.02*3*10^5 km/s = 6e3 km/s
Sun diameter 1.39*10^6 km. Grazing impact so say passes through 1.39*10^5 km of gas.

A = v^2/2x = (6e3)^2/(2*1.38e5) km/s^2 = 13 thousand times the acceleration due to gravity.
Easy.

mollwollfumble said:

I just did a calculation for how much acceleration/deceleration a large frozen cell (eg. human zygote/embryo) could take before fracturing.

Ballpark estimate 3 trillion times the acceleration due to gravity = 3*10^13 m/s^2.

Calculation details – indirect tension, tensile strength of ice assumed 1 MPa.
Compressive force at 1.5*10^-2 Newtons.
Mass of cell is only 0.5*10^-15 kg.
Acceleration = force over mass.

Stop from 2% of the speed of light = 0.02*3*10^5 km/s = 6e3 km/s
Sun diameter 1.39*10^6 km. Grazing impact so say passes through 1.39*10^5 km of gas.

A = v^2/2x = (6e3)^2/(2*1.38e5) km/s^2 = 13 thousand times the acceleration due to gravity.
Easy.

Sending them might be the easy part, turning them into a human being and raising them would be the hard part