chistev

I know it's a joke but it's because there's no clearly defined end of the solar system.

Just re-reading Pale Blue Dot by Carl Sagan and he talks about this. If we define the end of the solar system as the point where the suns gravity no longer holds, then it's going to be a very long time for it to escape the solar system.

I'm going to go find that passage in the book. Hopefully I can find it before the edit window closes for this comment.

Edit:

OK, I found it. This excerpt is from the book "Pale Blue Dot" by Carl Sagan, in the Chapter - AN AMERICAN SHIP AT THE FRONTIERS OF THE SOLAR SYSTEM .

THE VOYAGER SPACECRAFT are bound for the stars. They are on escape trajectories from the Solar System, barreling along at almost a million miles a day. The gravitational fields of Jupiter, Saturn, Uranus, and Neptune have flung them at such high speeds that they have broken the bonds that once tied them to the Sun.

Have they left the Solar System yet? The answer depends very much on how you define the boundary of the Sun's realm. If it's the orbit of the outermost good-sized planet, then the Voyager spacecraft are already long gone; there are probably no undiscovered Neptunes. If you mean the outermost planet, it may be that there are other—perhaps Triton-like—planets far beyond Neptune and Pluto; if so, Voyager 1 and Voyager 2 are still within the Solar System. If you define the outer limits of the Solar System as the heliopause—where the interplanetary particles and magnetic fields are replaced by their interstellar counterparts—then neither Voyager has yet left the Solar System, although they may do so in the next few decades.* But if your definition of the edge of the Solar System is the distance at which our star can no longer hold worlds in orbit about it, then the Voyagers will not leave the Solar System for hundreds of centuries.

Weakly grasped by the Sun's gravity, in every direction in the sky, is that immense horde of a trillion comets or more, the Oort Cloud. The two spacecraft will finish passage through the Oort Cloud in another 20,000 years or so. Then, at last, completely gone long good-bye to the Solar System, broken free of the gravitational shackles that once bound them to the Sun, the Voyagers will make for the open sea of interstellar space. Only then will Phase Two of their mission begin.

Their radio transmitters long dead, the spacecraft will wander for ages in the calm, cold interstellar blackness—where there is almost nothing to erode them. Once out of the Solar System, they will remain intact for a billion years or more, as they circumnavigate the center of the Milky Way galaxy.

We do not know whether there are other spacefaring civilizations in the Milky Way. If they do exist, we do not know how abundant they are, much less where they are. But there is at least a chance that sometime in the remote future one of the Voyagers will be intercepted and examined by an alien craft.

*Radio signals that both Voyagers detected in 1992 are thought to arise from the collision of powerful gusts of solar wind with the thin gas that lies between the stars. From the immense power of the signal (over 10 trillion watts), the distance to the heliopause can be estimated: about 100 times the Earth's distance from the Sun. At the speed it's leaving the Solar System, Voyager 1 might pierce the heliopause and enter interstellar space around the year 2010. If its radioactive power source is still working, news of the crossing will be radioed back to the stay-at-homes on Earth. The energy released by the collision of this shock wave with the heliopause makes it the most powerful source of radio emission in the Solar System. It makes you wonder whether even stronger shocks in other planetary systems might be detectable by our radio telescopes.

End of quotation.

If you're interested, I highly recommend the book and everything by Carl Sagan. He was incapable of writing a dull sentence.

Voyager 2 actually launched first, on August 20, 1977, followed by Voyager 1 on September 5, 1977. Because Voyager 1 was on a faster, shorter trajectory (it used a rare alignment to slingshot past both Jupiter and Saturn quicker), it overtook its twin and became the farther, faster probe. As of 2025, Voyager 1 is the most distant human-made object ever, more than 24 billion kilometers away, still whispering data home at 160 bits per second.

Each spacecraft carries an identical 12-inch gold-plated copper phonograph record.

The contents:

- Greetings in 55 human languages.

- A message from UN Secretary-General at the time and one from U.S. President Jimmy Carter.

- 115 analog images encoded in the record’s grooves: how to build the stylus and play the record, the solar system’s location using 14 pulsars as galactic GPS, diagrams of human DNA, photos of a supermarket, a sunset, a fetus, people eating, licking ice cream, and dancing

The record is encased in an aluminum jacket with instructions etched on the cover: a map of the pulsars, the hydrogen atom diagram so aliens can decode the time units, and a tiny sample of uranium-238 so they can carbon-date how old the record is when they find it.

Sagan wanted the record to be a message in a bottle for a billion years. The spacecraft themselves are expected to outlive Earth. In a billion years, when the Sun swells into a red giant and maybe swallows Earth, the Voyagers will still be cruising the Milky Way, silent gold disks carrying blind, naked humans waving hello to a universe that may never wave back.

And it was Sagan who, in 1989, when Voyager 1 was already beyond Neptune and its cameras were scheduled to be turned off forever to save power, begged NASA for one last maneuver. On Valentine’s Day 1990, the spacecraft turned around, took 60 final images, and captured Earth as a single pale blue pixel floating in a scattered beam of sunlight — the photograph that gives the book its name and its soul.

It was the photograph that inspired this famous quote -

"Look again at that dot. That's here. That's home. That's us. On it everyone you love, everyone you know, everyone you ever heard of, every human being who ever was, lived out their lives. The aggregate of our joy and suffering, thousands of confident religions, ideologies, and economic doctrines, every hunter and forager, every hero and coward, every creator and destroyer of civilization, every king and peasant, every young couple in love, every mother and father, hopeful child, inventor and explorer, every teacher of morals, every corrupt politician, every "superstar," every "supreme leader," every saint and sinner in the history of our species lived there-on a mote of dust suspended in a sunbeam.

The Earth is a very small stage in a vast cosmic arena. Think of the endless cruelties visited by the inhabitants of one corner of this pixel on the scarcely distinguishable inhabitants of some other corner, how frequent their misunderstandings, how eager they are to kill one another, how fervent their hatreds. Think of the rivers of blood spilled by all those generals and emperors so that, in glory and triumph, they could become the momentary masters of a fraction of a dot.

Our posturings, our imagined self-importance, the delusion that we have some privileged position in the Universe, are challenged by this point of pale light. Our planet is a lonely speck in the great enveloping cosmic dark. In our obscurity, in all this vastness, there is no hint that help will come from elsewhere to save us from ourselves.

The Earth is the only world known so far to harbor life. There is nowhere else, at least in the near future, to which our species could migrate. Visit, yes. Settle, not yet. Like it or not, for the moment the Earth is where we make our stand.

It has been said that astronomy is a humbling and character-building experience. There is perhaps no better demonstration of the folly of human conceits than this distant image of our tiny world. To me, it underscores our responsibility to deal more kindly with one another, and to preserve and cherish the pale blue dot, the only home we've ever known. "

That picture almost didn’t happen. NASA said it was pointless, the cameras were old, the images would be useless. Sagan argued it would be the first time any human ever saw our world from outside the solar system. He won. The cameras were powered up one last time, the portrait was taken, and then they were shut down forever.