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Voyager 1 stops communicating with Earth

cnn.com

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Re: Voyager 1 stops communicating with Earth

#631

Post by lazide »

pdonis wrote: post #558
lazide wrote: post #300

Earlier quoted context omitted.

They are still, indeed, orbiting the sun. In the same way the earths atmosphere is orbiting the earth.

The earth's atmosphere is not orbiting the Earth. It is in hydrostatic equilibrium in the earth's gravitational field. Big difference.

and yet, atmospheric particles that have a mean free path that doesn’t intersect with other atmospheric particles, or when they do the average velocity delta and direction reach escape velocity, escape and are lost.

You might want to rethink that. It’s a useful model in bulk in the lower atmosphere, but it’s far from true in the upper atmosphere.

Re: Voyager 1 stops communicating with Earth

#632

Post by lazide »

pdonis wrote: post #561
lazide wrote: post #493

Earlier quoted context omitted.

The particles don’t meaningfully interact, they aren’t dense enough.

They are plenty dense enough to interact given that it's plasma.

You might want to re-read that graph. And conservation of momentum means the particles leaving the sun don’t stop rotating when they leave the sun - the sun is rotating.

Re: Voyager 1 stops communicating with Earth

#634

Post by lazide »

pdonis wrote: post #560
lazide wrote: post #317

Earlier quoted context omitted.

Except they aren’t, which is why they are there and there is a heliopause instead of them being in interstellar space and there not being a heliopause. If they had greater than escape velocity, they’d be escaping and we’d not see the graph we see.

> If they had greater than escape velocity, they’d be escaping Only if the space they were escaping into were vacuum. Which it isn't. What stops them is not the Sun's gravity but the plasma in the interstellar medium.

If the intersteller medium is not a vacuum, what is? Last I checked, it was literally billions of times lower density than the hardest vacuum we’ve been able to produce on earth.

Re: Voyager 1 stops communicating with Earth

#635

Post by ant6n »

cafeinux wrote: post #629
soylentcola wrote: post #552

Earlier quoted context omitted.

I thought 6 was the one that became V'Ger.

It is, and afaik no Voyager probe has been destroyed by the Klingons.

Oh true. It was pioneer 10 that will get destroyed by Klingons. It’s easy to get them mixed up.

https://en.wikipedia.org/wiki/Pioneer_10#Pioneer_10_in_popul...

Re: Voyager 1 stops communicating with Earth

#636

Post by jacquesm »

kortilla wrote: post #609
jacquesm wrote: post #460

Earlier quoted context omitted.

No, indeed, I'm not a believer. When I see someone that lies with abandon and who regularly behaves in absolutely horrible ways towards others and that person happens to want to establish a colony on another planet my first thought is 'nutcase' not 'savior of humanity'. I marked Musk very early (long before his name became a household item) as someone with a ton of potential and he has definitely realized some of it.…

>In the meantime I'll just take what I see and extrapolate from there and it doesn't look good. What of spacex’s performance are you extrapolating from?

Sorry, not responding to obtuse comments.

Re: Voyager 1 stops communicating with Earth

#637

Post by gergo_b »

JKCalhoun wrote: post #504
londons_explore wrote: post #384

Earlier quoted context omitted.

If the contents of your computer is anything like the contents of most old people's attics, there is a good chance your descendants really don't want to go through all of it. They'll just chuck it in the trash without even opening it. Turns out the next generation has their own life to worry about, and doesn't care much for their ancestors' stuff (unless it's money... they love money...).

Because I have been interested in my dead relatives, and because I suspect somewhere down the line someone will be interested in my living ones, I have been trying to capture their lives in books I have created (real books — printed at Lulu.com).

That seems nice! Thank you for the idea.

Re: Voyager 1 stops communicating with Earth

#638

Post by GTP »

galeaspablo wrote: post #612
GTP wrote: post #512

Earlier quoted context omitted.

They can be used outside symmetric encryption, e.g. in signature schemes, but the hashing primitives are part of symmetric cryptography.

Again, I didn’t say symmetric cryptography :)

You talked about symmetric encryption.

Re: Voyager 1 stops communicating with Earth

#639

Post by pdonis »

lazide wrote: post #634
pdonis wrote: post #560

Earlier quoted context omitted.

> If they had greater than escape velocity, they’d be escaping Only if the space they were escaping into were vacuum. Which it isn't. What stops them is not the Sun's gravity but the plasma in the interstellar medium.

If the intersteller medium is not a vacuum, what is? Last I checked, it was literally billions of times lower density than the hardest vacuum we’ve been able to produce on earth.

> If the intersteller medium is not a vacuum, what is?

There is no threshold of low enough density at which there is suddenly "vacuum". If there are particles present, there are particles present, and they can have effects.

> Last I checked, it was literally billions of times lower density than the hardest vacuum we’ve been able to produce on earth.

[Edit--these numbers are off--see my post downthread]

And the solar wind is much, much less dense than that. Interstellar medium density is about a trillion particles per cubic meter. Solar wind density is about 5 thousand particles per cubic meter. So the interstellar medium is more than dense enough to stop the solar wind.

Re: Voyager 1 stops communicating with Earth

#640

Post by pdonis »

lazide wrote: post #631
pdonis wrote: post #558

Earlier quoted context omitted.

The earth's atmosphere is not orbiting the Earth. It is in hydrostatic equilibrium in the earth's gravitational field. Big difference.

and yet, atmospheric particles that have a mean free path that doesn’t intersect with other atmospheric particles, or when they do the average velocity delta and direction reach escape velocity, escape and are lost. You might want to rethink that. It’s a useful model in bulk in the lower atmosphere, but it’s far from true in the upper atmosphere.

> You might want to rethink that.

You might want to rethink your claim.

First, while the upper atmosphere is much less dense than the lower, and the fluid approximation becomes less and less useful as you gain altitude, that still doesn't mean that "a bunch of particles in free-fall orbits" becomes a useful model. The average thermal velocity of a molecule in the upper atmosphere is still well short of orbital velocity at that altitude. Some molecules acquire sufficient velocity to escape, sure, but that doesn't mean the others are in orbit.

Second, the Earth's atmosphere is not a good analogy for what is happening at the heliopause anyway.

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