5 ms·

Earth Detecting Earth

74 points by nabla9 2y ago

00N8 2y ago
It seems like they're calculating the farthest distances where it would be theoretically possible for aliens with Earth level tech to detect us, for various different ways of detection. I'm curious about a related question: At what distance would we likely have been able to detect 'ourselves' with current technology? Ie. if there was another Earth 100 or 1000 light years away, would we have seen it by now? (Assume they are x years ahead so the signals have had time to propagate). I think it may be a relatively short distance, which could have implications for resolving the Fermi paradox, but I haven't seen any definitive estimates & I'm curious to learn more.
- falcor84 2y ago
  My understanding based on their use of "technology similar to ours" is that this is exactly what they're doing: >If an extraterrestrial civilization existed with technology similar to ours, would they be able to detect Earth and evidence of humanity? If so, what signals would they detect, and from how far away?
  - 00N8 2y ago
    I was thinking we probably can't watch the whole sky in maximum detail all at once, so in practice we'll miss most possible detections.
  - InDubioProRubio 2y ago
    They could get a 25km high-resolution picture of the planet? https://en.wikipedia.org/wiki/Solar_gravitational_lens https://en.wikipedia.org/wiki/Solar_gravitational_lens
    - ben_w 2y ago
      The caveat "with technology similar to ours" precludes that, I think. We know how to do that, but we also know how to build an O'Neill cylinder, a phased array optical telescope covering the surface of the moon, or an orbital ring — but practical considerations mean we actually can't.
A_D_E_P_T 2y ago
The actual paper is here, in PDF form: https://iopscience.iop.org/article/10.3847/1538-3881/ada3c7/pdf https://iopscience.iop.org/article/10.3847/1538-3881/ada3c7/... The authors write that Earth could detect an Earthlike planet from 12000 light-years away via Earth's strong radio emissions -- specifically, the intermittent, celestially targeted radar beams (for example, those originally from Arecibo’s planetary radar). But we'd need to be laser-focused on the planet, and we'd need to catch them when they're emitting. Earth has only been emitting powerful radio waves for ~50 years, so our detection radius is ~50 LY. Besides radio, most other means have a very low range.
- vintagedave 2y ago
  I've read of occasional strange radio signals we detect that are intermittent or not repeated. Is it possible that, to an external observer, our 'strong radio emissions' that are 'intermittent, celestially targeted' could appear similar? With the natural question, could we have already observed something like what we're producing? I understand without a reproducible signal, no-one knows, but do any of those once-off signals work as a potential similar match?
  - ben_w 2y ago
    Several of them could have been, but without any repetitions, and given the lack of obvious signal in we actually recorded, and given the known natural processes that can cause transient radio bursts, the best bet is they're probably not aliens.
    - roughly 2y ago
      > the lack of obvious signal in we actually recorded This is something I’m curious about - I’m led to understand that modern digital signaling is almost impossible to tell from noise, unless you know what you’re looking for (encryption and compression both conspire against obvious structure), is that not the case? Would it be obvious from a signal construction level that we were looking at, well, signal, and not noise?
spuz 2y ago
I'm so glad that someone has finally tried to answer this question as it's something I've been wondering for years. It's interesting that atmospheric indicators are only detectable to around 5ly as that is I believe one of the primary methods we are using to look for technosignatures on other planets.
singularity2001 2y ago
Does seti look for π encoded in base 2? https://x.com/i/status/1886833653801738734 https://x.com/i/status/1886833653801738734
patrickhogan1 2y ago
Knowing what we know about the potential bad outcome of meeting aliens (yes I get that this would be cool - but it may not be safe). It’s probably smart to shutoff the signal that is broadcasting, where it can be detected up to 12,000 light years (50ly as of now). It seems much smarter to attempt to detect aliens than allow them to detect us.

74 points by nabla9 2y ago

00N8 2y ago

It seems like they're calculating the farthest distances where it would be theoretically possible for aliens with Earth level tech to detect us, for various different ways of detection. I'm curious about a related question: At what distance would we likely have been able to detect 'ourselves' with current technology? Ie. if there was another Earth 100 or 1000 light years away, would we have seen it by now? (Assume they are x years ahead so the signals have had time to propagate). I think it may be a relatively short distance, which could have implications for resolving the Fermi paradox, but I haven't seen any definitive estimates & I'm curious to learn more.

falcor84 2y ago
My understanding based on their use of "technology similar to ours" is that this is exactly what they're doing: >If an extraterrestrial civilization existed with technology similar to ours, would they be able to detect Earth and evidence of humanity? If so, what signals would they detect, and from how far away?
- 00N8 2y ago
  I was thinking we probably can't watch the whole sky in maximum detail all at once, so in practice we'll miss most possible detections.
- InDubioProRubio 2y ago
  They could get a 25km high-resolution picture of the planet? https://en.wikipedia.org/wiki/Solar_gravitational_lens https://en.wikipedia.org/wiki/Solar_gravitational_lens
  - ben_w 2y ago
    The caveat "with technology similar to ours" precludes that, I think. We know how to do that, but we also know how to build an O'Neill cylinder, a phased array optical telescope covering the surface of the moon, or an orbital ring — but practical considerations mean we actually can't.

A_D_E_P_T 2y ago

The actual paper is here, in PDF form: https://iopscience.iop.org/article/10.3847/1538-3881/ada3c7/pdf https://iopscience.iop.org/article/10.3847/1538-3881/ada3c7/... The authors write that Earth could detect an Earthlike planet from 12000 light-years away via Earth's strong radio emissions -- specifically, the intermittent, celestially targeted radar beams (for example, those originally from Arecibo’s planetary radar). But we'd need to be laser-focused on the planet, and we'd need to catch them when they're emitting. Earth has only been emitting powerful radio waves for ~50 years, so our detection radius is ~50 LY. Besides radio, most other means have a very low range.

vintagedave 2y ago
I've read of occasional strange radio signals we detect that are intermittent or not repeated. Is it possible that, to an external observer, our 'strong radio emissions' that are 'intermittent, celestially targeted' could appear similar? With the natural question, could we have already observed something like what we're producing? I understand without a reproducible signal, no-one knows, but do any of those once-off signals work as a potential similar match?
- ben_w 2y ago
  Several of them could have been, but without any repetitions, and given the lack of obvious signal in we actually recorded, and given the known natural processes that can cause transient radio bursts, the best bet is they're probably not aliens.
  - roughly 2y ago
    > the lack of obvious signal in we actually recorded This is something I’m curious about - I’m led to understand that modern digital signaling is almost impossible to tell from noise, unless you know what you’re looking for (encryption and compression both conspire against obvious structure), is that not the case? Would it be obvious from a signal construction level that we were looking at, well, signal, and not noise?

spuz 2y ago

I'm so glad that someone has finally tried to answer this question as it's something I've been wondering for years. It's interesting that atmospheric indicators are only detectable to around 5ly as that is I believe one of the primary methods we are using to look for technosignatures on other planets.

singularity2001 2y ago

Does seti look for π encoded in base 2? https://x.com/i/status/1886833653801738734 https://x.com/i/status/1886833653801738734

patrickhogan1 2y ago

Knowing what we know about the potential bad outcome of meeting aliens (yes I get that this would be cool - but it may not be safe). It’s probably smart to shutoff the signal that is broadcasting, where it can be detected up to 12,000 light years (50ly as of now). It seems much smarter to attempt to detect aliens than allow them to detect us.