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Comment by irrational | Hacker News Reader

What about the voyager probes? How far has the farthest one travelled in your analogy?

Using the moon for the farthest distance humans have traveled… Voyager has traveled 60,000 times further (14 billion miles).

1 cm x 60,000 = 600 meters

Which is less than 0.5% of the distance to Alpha Centauri (“200 km” in the analogy, 25 trillion miles in real units)

Edit: a neighboring comment pointed out that on this scale of distance to moon ~= 1 cm, the Alpha Centauri system is more like 1000 km away. So voyager is less than 0.1% of the way.

And voyager is going so fast because it used a clever gravitational slingshot technique, for which such a good opportunity hasn't yet arisen again.

Without that natural assistance, humans don't have the ability to leave the solar system - we just can't build a rocket powerful enough.

Those gravitational slingshots are easy. It all comes from Jupiter, that's all you need. Saturn has 30% of the mass and two-thirds the orbital velocity, so that's a marginal gain on top of Jupiter, and the ice giants are smaller and slower yet.

The Jupiter launch window opportunity comes every 13 months so we can do that whenever we want. And we can launch rockets directly out of the solar system if we want; New Horizons had a backup plan of launching direct to Pluto if it had been delayed and missed the Jupiter-Pluto alignment.

That all said, the planetary slingshots aren't nearly enough to cross interstellar distances in a timespan measurable in human generations. We want something like 5% of the speed of light for that, where Voyager is going 0.005%.

Thanks for mentioning this. I did a bit of reading about the special alignment - very interesting stuff!

It seems like the alignment you refer to inspired the launch of Voyager 1 and 2 because they could visit so many planets at one time, and indeed it did slingshot them at quite some speed. However newer launches have reached similar speeds, and will escape the solar system due to improvements in launch technology.

Pioneer 10, Pioneer 11, Voyager I and II, and New Horizons are all on solar escape trajectories. If you just want to get out of the solar system, existing tech plus a Jupiter gravity assist gets you there easily.

We probably could assemble some giant space hulk and put so much fuel into it that the rocket equation starts blushing. It would be insanely expensive and not at all too constructive, but we should be able to beat the speed record at least.

We could if we really wanted to: https://en.wikipedia.org/wiki/Project_Orion_(nuclear_propuls...

Of course we can, we just choose not to. We've had designs for nuclear rockets for many decades now.

Well, to make his analogy more rigourous, because his 200 km is laughably too small.

Moon: 238,900 miles --> 1.3 cm or 0.00 km

(This defines the scale as 0.0000054416073670992 cm / mile.)

Voyager 2: 12,000,000,000 miles --> 65,299.0 cm or 0.65 km

Proxima: 25,000,000,000,000 miles --> 136,040,184.2 cm or 1,360.40 km

Not far if I recall a few documentaries properly.

The kuiper belt is outside the solar system and then there is the shell of the Oort Cloud that Voyager won't pass through for ages. So it's been decades and we haven't even truly sent anything outside the solar system.

This is all assuming I remembered the terms correctly. Maybe someone who knows this field can comment. Point being getting to another star would take a lot of time :)

About 120 meters.

Interstellar space is big.

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