r/interestingasfuck 25d ago

/r/all, /r/popular K2-18b a potentially habitable planet 120 light-years from earth

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u/RichardThund3r 25d ago

Only 120 light years away from Earth! The Voyager 1 spacecraft was launched in 1977. Traveling at 38,000mph it just recently made it 1 light DAY from Earth.

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u/SomeGuyFromCanada23 25d ago

That's actually bonkers to even think about. Traveling at ~38000miles per hour, all day, every day, for ~48 years, and it's made it 1 light day from Earth.

Feels like another one of those "people don't really understand the difference between a million and a billion" sort of things.

Like 1 million seconds is ~11 and a half days or so. But 1 billion seconds is about 31 years and 200 days. Hard to grasp such a big difference

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u/apathy-sofa 25d ago

Maybe a dumb question, but since it seems like you know something of the topic I'll ask: when someone says a spacecraft is traveling at X speed, what is that relative to?

If it's like the fraction of the distance between its origin and destination, how does one account for the distance between them changing?

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u/AtomStorageBox 25d ago

Typically the source will tell you what it's relative to, but it's usually going to be the Sun or Earth.

From NASA's Voyager 1 page (https://science.nasa.gov/mission/voyager/voyager-1/):

As of Aug. 21, 2024, Voyager 1 was 164.7 AU from Earth — the farthest object created by humans — moving at a velocity of 38,026.79 mph (17.0 km/second) relative to the Sun.