11 ms·

So, we can detect - see, dammit - something perhaps only 300km across at twice the distance to Pluto, and by reflected light alone. Every now and again, my int

So, we can detect - see, dammit - something perhaps only 300km across at twice the distance to Pluto, and by reflected light alone. Every now and again, my intuition breaks utterly down.

etatoby 8y ago
And through the atmosphere, no less. (The telescope used is in Hawaii)
- okket 8y ago
  Adaptive optics [0] takes care of atmospheric distortions. Combined with the huge telescopes that are possible on earth and impossible to ferry to space in the foreseeable future, advancements in sensors and data processing, which is also much, much easier on earth and at best possible with constraints / a long delay in space, I think earth based telescopes are still the future. Special cases like the infrared spectrum (JWT) exist. But the delays show how extremely difficult space based observation is. [0] https://en.wikipedia.org/wiki/Adaptive_optics https://en.wikipedia.org/wiki/Adaptive_optics [Edit: wrong link]
  - kroltan 8y ago
    "Active optics is not to be confused with adaptive optics, which operates at a shorter timescale and corrects atmospheric distortions." ~ "Active optics", Wikipedia https://en.wikipedia.org/wiki/Adaptive_optics https://en.wikipedia.org/wiki/Adaptive_optics
    - okket 8y ago
      Correct, sorry. I updated my comment.
rrmm 8y ago
Yeah, I have no intuition with this. The telescope they used was 8.2m and they used 300-400 second exposures (with spectral filters). I guess it comes down to space being really really dark and cyrogenically-cooled CCDs having pretty good noise floors. The authors had this to say about it: Surprisingly, like 2012 VP113, 2015 TG387 is relatively bright compared to the limiting magnitude of most of the survey fields. The Subaru observations generally go deeper than 25.5 mags, making 2015 TG387 about 1.5 mags brighter than the limiting magnitude of the disocovery survey fields it was found in.
lifeisstillgood 8y ago
So, silly question, can we see / photograph the Apollo lander? It always struck me as a really nice response to anyone being silly about fake landings.
- interfixus 8y ago
  Been done. Doesn't seem to faze the loonies. https://www.nasa.gov/mission_pages/LRO/news/apollo-sites.html https://www.nasa.gov/mission_pages/LRO/news/apollo-sites.htm...
  - LyndsySimon 8y ago
    > Doesn't seem to faze the loonies. Given the etymology of that word, that's a deliciously ironic sentence :)
  - api 8y ago
    That's because they don't believe this stuff for rational reasons but to fit into a group or in some cases as a "fuck you belief" directed at "the establishment." "Fuck you beliefs" are a personal theory of mine. People sometimes assume ridiculous and deliberately provocative "beliefs" as a means of explicit rejection of a social order. The canonical example would be Satanism as a rejection of Christian culture/society. Believing Apollo is a hoax or that the Earth is flat is an explicit rejection of the industrial/scientific/corporate/university complex and its culture. The absurdity of these beliefs adds to their value as acts of protest. The phenomenon can also take the form of refusal to believe something taught by the hated authority. If the belief being refused is actually true and demonstrably so, it becomes a more potent act of protest. Talk to the people that hold beliefs like the Apollo hoax and scratch the surface and you'll usually find someone who is under-employed in a dead-end job with no future and too much student loan debt. They are adopting an absurdist epistemology in protest of a society that they see as having failed them. When I see conspiracy theories becoming popular I see a metaphysical and epistemological version of people throwing Molotov cocktails in the street at cops in riot gear under clouds of tear gas. Maybe this is what mass protests and "riots in the street" look like in the Information Age.
jcims 8y ago
If you trace the path of individual photons it seems implausible. That somehow a photon leaves the sun, travels possibly weeks until it strikes some nanoscopic face of a crystal on the surface of this object, which is rotating and travelling tangentially at several km/sec, and departs at such a resolved and precise an angle that it makes it almost all the way back to the sun, passes through the atmosphere of an orbiting body travelling 30km/sec, lands on a finely curated layer of aluminum where it is reflected yet again and lands on a square likely smaller than an index card.
- kgilpin 8y ago
  There may be more photons than you think. 10^^17 per cm^^2 per second at the surface of the earth. https://www.reddit.com/r/askscience/comments/2n6zo0/comment/cmax1uj https://www.reddit.com/r/askscience/comments/2n6zo0/comment/...
  - drdeca 8y ago
    What do you mean by the double caret (cm^^2) ?
    - zimpenfish 8y ago
      I think that's a plain text way of saying "square centimetres" - `^` often means `xor` thus `^^` to mean exponentiation (and is less obtuse than `cm2`)
      - drdeca 8y ago
        Ah, I didn't think of it being to disambiguate from xor. I would usually expect 2^3 to mean 8, and 2^^3 to mean 16 Perhaps too much time reading people talk about 3^^^^3 dust specs
      - EForEndeavour 8y ago
        I've never seen '^^' to mean exponentiation. In Python (and probably other languages), exponentiation is denoted with '', so 23 = 8.

So, we can detect - see, dammit - something perhaps only 300km across at twice the distance to Pluto, and by reflected light alone. Every now and again, my intuition breaks utterly down.

etatoby 8y ago

And through the atmosphere, no less. (The telescope used is in Hawaii)

okket 8y ago
Adaptive optics [0] takes care of atmospheric distortions. Combined with the huge telescopes that are possible on earth and impossible to ferry to space in the foreseeable future, advancements in sensors and data processing, which is also much, much easier on earth and at best possible with constraints / a long delay in space, I think earth based telescopes are still the future. Special cases like the infrared spectrum (JWT) exist. But the delays show how extremely difficult space based observation is. [0] https://en.wikipedia.org/wiki/Adaptive_optics https://en.wikipedia.org/wiki/Adaptive_optics [Edit: wrong link]
- kroltan 8y ago
  "Active optics is not to be confused with adaptive optics, which operates at a shorter timescale and corrects atmospheric distortions." ~ "Active optics", Wikipedia https://en.wikipedia.org/wiki/Adaptive_optics https://en.wikipedia.org/wiki/Adaptive_optics
  - okket 8y ago
    Correct, sorry. I updated my comment.

rrmm 8y ago

Yeah, I have no intuition with this. The telescope they used was 8.2m and they used 300-400 second exposures (with spectral filters). I guess it comes down to space being really really dark and cyrogenically-cooled CCDs having pretty good noise floors. The authors had this to say about it: Surprisingly, like 2012 VP113, 2015 TG387 is relatively bright compared to the limiting magnitude of most of the survey fields. The Subaru observations generally go deeper than 25.5 mags, making 2015 TG387 about 1.5 mags brighter than the limiting magnitude of the disocovery survey fields it was found in.

lifeisstillgood 8y ago

So, silly question, can we see / photograph the Apollo lander? It always struck me as a really nice response to anyone being silly about fake landings.

interfixus 8y ago
Been done. Doesn't seem to faze the loonies. https://www.nasa.gov/mission_pages/LRO/news/apollo-sites.html https://www.nasa.gov/mission_pages/LRO/news/apollo-sites.htm...
- LyndsySimon 8y ago
  > Doesn't seem to faze the loonies. Given the etymology of that word, that's a deliciously ironic sentence :)
- api 8y ago
  That's because they don't believe this stuff for rational reasons but to fit into a group or in some cases as a "fuck you belief" directed at "the establishment." "Fuck you beliefs" are a personal theory of mine. People sometimes assume ridiculous and deliberately provocative "beliefs" as a means of explicit rejection of a social order. The canonical example would be Satanism as a rejection of Christian culture/society. Believing Apollo is a hoax or that the Earth is flat is an explicit rejection of the industrial/scientific/corporate/university complex and its culture. The absurdity of these beliefs adds to their value as acts of protest. The phenomenon can also take the form of refusal to believe something taught by the hated authority. If the belief being refused is actually true and demonstrably so, it becomes a more potent act of protest. Talk to the people that hold beliefs like the Apollo hoax and scratch the surface and you'll usually find someone who is under-employed in a dead-end job with no future and too much student loan debt. They are adopting an absurdist epistemology in protest of a society that they see as having failed them. When I see conspiracy theories becoming popular I see a metaphysical and epistemological version of people throwing Molotov cocktails in the street at cops in riot gear under clouds of tear gas. Maybe this is what mass protests and "riots in the street" look like in the Information Age.

jcims 8y ago

If you trace the path of individual photons it seems implausible. That somehow a photon leaves the sun, travels possibly weeks until it strikes some nanoscopic face of a crystal on the surface of this object, which is rotating and travelling tangentially at several km/sec, and departs at such a resolved and precise an angle that it makes it almost all the way back to the sun, passes through the atmosphere of an orbiting body travelling 30km/sec, lands on a finely curated layer of aluminum where it is reflected yet again and lands on a square likely smaller than an index card.

kgilpin 8y ago
There may be more photons than you think. 10^^17 per cm^^2 per second at the surface of the earth. https://www.reddit.com/r/askscience/comments/2n6zo0/comment/cmax1uj https://www.reddit.com/r/askscience/comments/2n6zo0/comment/...
- drdeca 8y ago
  What do you mean by the double caret (cm^^2) ?
  - zimpenfish 8y ago
    I think that's a plain text way of saying "square centimetres" - `^` often means `xor` thus `^^` to mean exponentiation (and is less obtuse than `cm2`)
    - drdeca 8y ago
      Ah, I didn't think of it being to disambiguate from xor. I would usually expect 2^3 to mean 8, and 2^^3 to mean 16 Perhaps too much time reading people talk about 3^^^^3 dust specs
    - EForEndeavour 8y ago
      I've never seen '^^' to mean exponentiation. In Python (and probably other languages), exponentiation is denoted with '', so 23 = 8.