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Quick, How Might the Alien Spacecraft Work?

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Re: Quick, How Might the Alien Spacecraft Work?

#21

Post by avar »

ansible wrote: post #15

The problem with interstellar travel in general is that it is so expensive, in terms of energy usage. I speculate that even for Kardashev type 3 civilizations, shipping matter around will be impractical. The future is software. For entities that live purely as software, and aren't so picky as us meatbags are about continuity of consciousness, "traveling" from place to place by sending data is the most practical metho…

There's no need to do faster than light, or even all that fast. The diameter of the Milky Way is at most 200k light years, with technology we could develop today we could populate the entirety of it with generation ships in the span of less than 100 million years, which isn't all that big in the scale of the universe.

Re: Quick, How Might the Alien Spacecraft Work?

#22

Post by avar »

jandrese wrote: post #14
dghughes wrote: post #7

It always seems to involve mastering gravity yet gravity is so incredibly weak compared to magnetism. Plus "alien spacecraft" aka UFOs always seem to output a huge amount of light so maybe gravity and light are linked in the process or mechanism for whatever makes the thing operate. I like the article how it mentions getting the science believable or at least not terrible wrong. But what I dislike as much as that is…

Using gravity as a propulsive force may be silly given its relative strength, but having a way of blocking gravity would make a tremendous difference in getting out of our gravity well. It's not so much help for achieving orbit, but if you want to go beyond the Earth or even beyond the Solar System it would be a whole new game.

If you can block gravity you can achieve orbit at walking speeds if you turn of your anti-gravity machine some tiny fraction of the time you're spending in orbit.

Similarly with going outside the solar system, you could just jump on the planet Earth and press the "anti-grav" button, and in a few hundred thousand years you'd be outside the solar system.

Re: Quick, How Might the Alien Spacecraft Work?

#23

Post by jws »

avar wrote: post #22
jandrese wrote: post #14

Earlier quoted context omitted.

Using gravity as a propulsive force may be silly given its relative strength, but having a way of blocking gravity would make a tremendous difference in getting out of our gravity well. It's not so much help for achieving orbit, but if you want to go beyond the Earth or even beyond the Solar System it would be a whole new game.

If you can block gravity you can achieve orbit at walking speeds if you turn of your anti-gravity machine some tiny fraction of the time you're spending in orbit. Similarly with going outside the solar system, you could just jump on the planet Earth and press the "anti-grav" button, and in a few hundred thousand years you'd be outside the solar system.

I think you can dispense with the "jump". Just press the "gravity off" switch at midnight. You will be on the far side of the earth from the sun, as the earth is pulled to the sun in its orbit, you will drift away on a tangent line at 30km/s relative to the sun.

Google says "9 billion miles divided by 30km/s" is a little over 15 years and you are out of the solar system.

(I'm ignoring the milky way here, The sun is whizzing around the milky way at 230km/s, but it isn't very near the center so the "chord near the center is simplified to radius" which I snuck by you in the previous paragraph isn't valid. But you should definitely work this out before flicking the switch. Depending on the relative gravity/velocity magnitudes and the time of year, you could drive yourself through the sun on your way out of the solar system, which voids your warrantee.)

Re: Quick, How Might the Alien Spacecraft Work?

#26

Post by avar »

jws wrote: post #23
avar wrote: post #22

Earlier quoted context omitted.

If you can block gravity you can achieve orbit at walking speeds if you turn of your anti-gravity machine some tiny fraction of the time you're spending in orbit. Similarly with going outside the solar system, you could just jump on the planet Earth and press the "anti-grav" button, and in a few hundred thousand years you'd be outside the solar system.

I think you can dispense with the "jump". Just press the "gravity off" switch at midnight. You will be on the far side of the earth from the sun, as the earth is pulled to the sun in its orbit, you will drift away on a tangent line at 30km/s relative to the sun. Google says "9 billion miles divided by 30km/s" is a little over 15 years and you are out of the solar system. (I'm ignoring the milky way here, The sun is w…

Thanks, I didn't do any of the math, but I should have remembered better from this counteractive fact: You're already at 30km/s, it takes more energy to fall into the Sun than escape the Solar System.

Even if you press the "gravity off" button at some random time during the day the odds of you hitting anything are tiny, even if you fly towards the sun most of the time you'll just fly right past it and be no worse off. Except for the part where there's no oxygen and you can't breathe of course.

Re: Quick, How Might the Alien Spacecraft Work?

#27

Post by nerfhammer »

jandrese wrote: post #14
dghughes wrote: post #7

It always seems to involve mastering gravity yet gravity is so incredibly weak compared to magnetism. Plus "alien spacecraft" aka UFOs always seem to output a huge amount of light so maybe gravity and light are linked in the process or mechanism for whatever makes the thing operate. I like the article how it mentions getting the science believable or at least not terrible wrong. But what I dislike as much as that is…

Using gravity as a propulsive force may be silly given its relative strength, but having a way of blocking gravity would make a tremendous difference in getting out of our gravity well. It's not so much help for achieving orbit, but if you want to go beyond the Earth or even beyond the Solar System it would be a whole new game.

Gravity is just spacetime curvature. You can "turn off" gravity by just accelerating in the opposite direction at 1g.

Re: Quick, How Might the Alien Spacecraft Work?

#28

Post by spynxic »

avar wrote: post #26
jws wrote: post #23

Earlier quoted context omitted.

I think you can dispense with the "jump". Just press the "gravity off" switch at midnight. You will be on the far side of the earth from the sun, as the earth is pulled to the sun in its orbit, you will drift away on a tangent line at 30km/s relative to the sun. Google says "9 billion miles divided by 30km/s" is a little over 15 years and you are out of the solar system. (I'm ignoring the milky way here, The sun is w…

Thanks, I didn't do any of the math, but I should have remembered better from this counteractive fact: You're already at 30km/s, it takes more energy to fall into the Sun than escape the Solar System. Even if you press the "gravity off" button at some random time during the day the odds of you hitting anything are tiny , even if you fly towards the sun most of the time you'll just fly right past it and be no worse of…

"gravity off" is a lofty term to toss around so freely. Consider an omnipresent force or curvature vanishing one spot. I can't imagine gravity but the effects in an ocean would obviously be to fill the hole with massive force.

Re: Quick, How Might the Alien Spacecraft Work?

#29

Post by booleandilemma »

dghughes wrote: post #7

It always seems to involve mastering gravity yet gravity is so incredibly weak compared to magnetism. Plus "alien spacecraft" aka UFOs always seem to output a huge amount of light so maybe gravity and light are linked in the process or mechanism for whatever makes the thing operate. I like the article how it mentions getting the science believable or at least not terrible wrong. But what I dislike as much as that is…

There's a short story by Harry Turtledove about aliens that have mastered gravity (because, as it turns out, it isn't that difficult to do) but all of their other technology is pre-industrial revolution level. They try to invade Earth in 2039 - I won't spoil what happens next. It's a fun read.

https://en.m.wikipedia.org/wiki/The_Road_Not_Taken_(short_st...

Re: Quick, How Might the Alien Spacecraft Work?

#30

Post by mustacheemperor »

avar wrote: post #21
ansible wrote: post #15

The problem with interstellar travel in general is that it is so expensive, in terms of energy usage. I speculate that even for Kardashev type 3 civilizations, shipping matter around will be impractical. The future is software. For entities that live purely as software, and aren't so picky as us meatbags are about continuity of consciousness, "traveling" from place to place by sending data is the most practical metho…

There's no need to do faster than light, or even all that fast. The diameter of the Milky Way is at most 200k light years, with technology we could develop today we could populate the entirety of it with generation ships in the span of less than 100 million years, which isn't all that big in the scale of the universe.

I read this, and about ideas like the Von Neumann probe[0] all the time, and it really fills my head with concrete to try and reconcile those ideas with the fact that we haven't found any signs of extraterrestrial life yet. If it's so feasible in a "short" time relative to the age of the universe, where are all the probes?

[0]https://en.wikipedia.org/wiki/Self-replicating_spacecraft#Vo...

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