3 ms·

Cloud cover doesn't affect microwaves?

by notum 4y ago

JumpCrisscross 4y ago
> Cloud cover doesn't affect microwaves? It does. (Ozone and water absorb microwaves. This is how your microwave oven works.)
- Nomentatus 4y ago
  Microwaves are highly tuned to the particular frequency that causes water molecules to resonate. But this is just one microwave frequency. You don't have to use that one. https://www.gi.alaska.edu/news/using-microwaves-see-through-clouds https://www.gi.alaska.edu/news/using-microwaves-see-through-...
  - notum 4y ago
    To expand on my semi-sarcasm with a proper question: so there's a microwave frequency that is completely unaffected by atmospherics? In which water, ozone, the rest of the gas mixure and particulates are mostly transparent? What frequency spectrum is that? And for bonus points: can this project fry commercial planes?
    - Nomentatus 4y ago
      First sentence: not what was said. But note that microwave towers have been in use for mission-critical long-range all-weather point-to-point communication on earth for many, many decades. My late father helped design some of them. What would the minimum power loss be for thick cloud/hurricane? Dunno.
      - notum 4y ago
        As synonymous comms and power delivery may look, they are a different ball game. This also seems to be the last nail in the coffin for terrestrial radio astronomy, now that you mention it.
      - zaroth 4y ago
        Those microwave towers are transmitting some number of milliwatts of power though, with super high gain antennas. Not kilowatts.
    - Tade0 4y ago
      > so there's a microwave frequency that is completely unaffected by atmospherics? In which water, ozone, the rest of the gas mixure and particulates are mostly transparent? Nope. The transparent bands are in the visible spectrum and far infrared(8-14um). Microwaves are mostly uniformly absorbed by water molecules: https://en.m.wikipedia.org/wiki/Atmospheric_window https://en.m.wikipedia.org/wiki/Atmospheric_window
  - JumpCrisscross 4y ago
    > this is just one microwave frequency. You don't have to use that one The atmosphere is almost transparent to long-wavelength microwave [1]. The tradeoff is in power density. [1] https://earthobservatory.nasa.gov/features/RemoteSensing/remote_04.php https://earthobservatory.nasa.gov/features/RemoteSensing/rem...
  - ben_w 4y ago
    > Microwaves are highly tuned to the particular frequency that causes water molecules to resonate. That's an urban legend. If it was true, they'd be great rather than "meh" at melting ice, and (I appreciate most don't do this anyway) we wouldn't be able use domestic ovens for glass-working or melting alumina to make synthetic sapphires and rubies. • https://youtu.be/XojnG2IFfTo https://youtu.be/XojnG2IFfTo • https://youtu.be/xwEQZw3KPWg https://youtu.be/xwEQZw3KPWg • https://youtu.be/ybcdRQmQcHQ https://youtu.be/ybcdRQmQcHQ
    - Nomentatus 4y ago
      Good points, but careful of the logic; yes there's a lot of energy being produced and plenty of harmonics etc. None of which says that every material heats equally well, with no passthrough, or that microwave ovens with different frequencies wouldn't be more efficient for other specific materials. If a material is dense enough (metal being the prime example) it'll block. I've nowhere argued that you could send microwave power through solid walls - whether brick or sapphire economically.

Cloud cover doesn't affect microwaves?

by notum 4y ago

Cloud cover doesn't affect microwaves?

> Cloud cover doesn't affect microwaves? It does. (Ozone and water absorb microwaves. This is how your microwave oven works.)

Nomentatus 4y ago
Microwaves are highly tuned to the particular frequency that causes water molecules to resonate. But this is just one microwave frequency. You don't have to use that one. https://www.gi.alaska.edu/news/using-microwaves-see-through-clouds https://www.gi.alaska.edu/news/using-microwaves-see-through-...
- notum 4y ago
  To expand on my semi-sarcasm with a proper question: so there's a microwave frequency that is completely unaffected by atmospherics? In which water, ozone, the rest of the gas mixure and particulates are mostly transparent? What frequency spectrum is that? And for bonus points: can this project fry commercial planes?
  - Nomentatus 4y ago
    First sentence: not what was said. But note that microwave towers have been in use for mission-critical long-range all-weather point-to-point communication on earth for many, many decades. My late father helped design some of them. What would the minimum power loss be for thick cloud/hurricane? Dunno.
    - notum 4y ago
      As synonymous comms and power delivery may look, they are a different ball game. This also seems to be the last nail in the coffin for terrestrial radio astronomy, now that you mention it.
    - zaroth 4y ago
      Those microwave towers are transmitting some number of milliwatts of power though, with super high gain antennas. Not kilowatts.
  - Tade0 4y ago
    > so there's a microwave frequency that is completely unaffected by atmospherics? In which water, ozone, the rest of the gas mixure and particulates are mostly transparent? Nope. The transparent bands are in the visible spectrum and far infrared(8-14um). Microwaves are mostly uniformly absorbed by water molecules: https://en.m.wikipedia.org/wiki/Atmospheric_window https://en.m.wikipedia.org/wiki/Atmospheric_window
- JumpCrisscross 4y ago
  > this is just one microwave frequency. You don't have to use that one The atmosphere is almost transparent to long-wavelength microwave [1]. The tradeoff is in power density. [1] https://earthobservatory.nasa.gov/features/RemoteSensing/remote_04.php https://earthobservatory.nasa.gov/features/RemoteSensing/rem...
- ben_w 4y ago
  > Microwaves are highly tuned to the particular frequency that causes water molecules to resonate. That's an urban legend. If it was true, they'd be great rather than "meh" at melting ice, and (I appreciate most don't do this anyway) we wouldn't be able use domestic ovens for glass-working or melting alumina to make synthetic sapphires and rubies. • https://youtu.be/XojnG2IFfTo https://youtu.be/XojnG2IFfTo • https://youtu.be/xwEQZw3KPWg https://youtu.be/xwEQZw3KPWg • https://youtu.be/ybcdRQmQcHQ https://youtu.be/ybcdRQmQcHQ
  - Nomentatus 4y ago
    Good points, but careful of the logic; yes there's a lot of energy being produced and plenty of harmonics etc. None of which says that every material heats equally well, with no passthrough, or that microwave ovens with different frequencies wouldn't be more efficient for other specific materials. If a material is dense enough (metal being the prime example) it'll block. I've nowhere argued that you could send microwave power through solid walls - whether brick or sapphire economically.