5 ms·

20 years?! — A nearest star in a lifetime. I hope to see this project launch soon.

account-5 5y ago
I'm left wondering if that 20 years was from earth of the probe seeing as we're talking about relativistic times. If it's 20 years on earth how much time would have passed for the probe, and visa versa?
- pklausler 5y ago
  This is nowhere near "relativistic" in velocity.
  - prpl 5y ago
    We generally regard things above .1c to be relativistically significant, but maybe not all that interesting for thought experiments
  - Stevvo 5y ago
    Actually it is, but not dramatically; for 20 years at 0.1c an extra 5 weeks will have passed for the probe.
    - thaumasiotes 5y ago
      > an extra 5 weeks will have passed for the probe. What does this mean? The only quantity I can see with an obvious meaning is that the probe will arrive somewhere after experiencing a certain amount of time since leaving Earth. But the time of the probe's arrival is not easily matched to any time on Earth. Suppose the probe arrives and dispatches a message which travels back to Earth at the speed of light. For simplicity, the distance is exactly 4 light years. - How much time did the probe experience between leaving Earth and sending the "I made it" message? - How much time did Earth experience between the probe leaving and the "I made it" message arriving? It's kind of unsatisfying that these two questions don't share both their endpoints, but at least they both have well-defined answers.
      - fennecfoxen 5y ago
        Spacetime intervals are always relatable and very well defined. There’s never one right reference frame that is better than another in some way, such that when you interpret the spacetime interval as space and time it is More Right than another interpretation, but all the interpretations are predictable. In this case it means that if the probe arrives at Mission Year 20 Week 0 according to a reliable onboard clock, and broadcasts it 4 light years back to Earth, then Earth will get this signal on Year 24 Week 5.
  - ben_w 5y ago
    The Lorenz factor is 1.021, which sounds like it’s just enough to make it engineering the mirror to not instantly vaporise even harder without being enough to help with anything.
- lmilcin 5y ago
  Lorentz factor at that speed is very small. https://en.wikipedia.org/wiki/Lorentz_factor https://en.wikipedia.org/wiki/Lorentz_factor
jillesvangurp 5y ago
It would be another 20 years before we hear back from it. If at all.
- jeeeb 5y ago
  Wouldn’t it be more like another 4.5 years to hear back? The probe itself doesn’t need to turn around and come back.
  - nine_k 5y ago
    I'd say 24.5 years then. 20 years to come close enough, and 4.5 for the signal to come back at the speed of light.

I'm left wondering if that 20 years was from earth of the probe seeing as we're talking about relativistic times. If it's 20 years on earth how much time would have passed for the probe, and visa versa?

pklausler 5y ago
This is nowhere near "relativistic" in velocity.
- prpl 5y ago
  We generally regard things above .1c to be relativistically significant, but maybe not all that interesting for thought experiments
- Stevvo 5y ago
  Actually it is, but not dramatically; for 20 years at 0.1c an extra 5 weeks will have passed for the probe.
  - thaumasiotes 5y ago
    > an extra 5 weeks will have passed for the probe. What does this mean? The only quantity I can see with an obvious meaning is that the probe will arrive somewhere after experiencing a certain amount of time since leaving Earth. But the time of the probe's arrival is not easily matched to any time on Earth. Suppose the probe arrives and dispatches a message which travels back to Earth at the speed of light. For simplicity, the distance is exactly 4 light years. - How much time did the probe experience between leaving Earth and sending the "I made it" message? - How much time did Earth experience between the probe leaving and the "I made it" message arriving? It's kind of unsatisfying that these two questions don't share both their endpoints, but at least they both have well-defined answers.
    - fennecfoxen 5y ago
      Spacetime intervals are always relatable and very well defined. There’s never one right reference frame that is better than another in some way, such that when you interpret the spacetime interval as space and time it is More Right than another interpretation, but all the interpretations are predictable. In this case it means that if the probe arrives at Mission Year 20 Week 0 according to a reliable onboard clock, and broadcasts it 4 light years back to Earth, then Earth will get this signal on Year 24 Week 5.
- ben_w 5y ago
  The Lorenz factor is 1.021, which sounds like it’s just enough to make it engineering the mirror to not instantly vaporise even harder without being enough to help with anything.
lmilcin 5y ago
Lorentz factor at that speed is very small. https://en.wikipedia.org/wiki/Lorentz_factor https://en.wikipedia.org/wiki/Lorentz_factor

jillesvangurp 5y ago

It would be another 20 years before we hear back from it. If at all.

jeeeb 5y ago
Wouldn’t it be more like another 4.5 years to hear back? The probe itself doesn’t need to turn around and come back.
- nine_k 5y ago
  I'd say 24.5 years then. 20 years to come close enough, and 4.5 for the signal to come back at the speed of light.