Is It Wise To Mess About With Daylight?

[ToraToraTora]

https://www.bbc.co.uk/news/world-asia-china-45910479

[Zacs-Master]

But it's meant for night time.

[spathiphyllum]

Well the artificial moon would be a mirror, so in theory, it's messing with daylight.

Reminds me of the walkie talkie building in London. Best not, ay.

[spathiphyllum]

Anyhow, they have no idea how it will affect the local wildlife

[Zacs-Master]

Maybe Pandas will mate more frequently!

[retrocop]

//Anyhow, they have no idea how it will affect the local wildlife//

Could deter burglars.

[jno]

shouldn't think it will disrupt human activity more than the introduction of street lighting did (which did make changes to city living - safer streets, fewer accidents - but didn't change humanity)

[Zacs-Master]

Could encourage dogging.

[retrocop]

I hope they have a mechanism to deflect the mirrors in the sunshine hours or they will have a load of frazzled black skinned Chinese people.

[ToraToraTora]

ok for ZM who apparently needs every detail spelt out, is it wise to mess about with the normal hours of daylight? Is that OK, or are we nailing jelly again? I asked this in science because I'd hoped to get a reasonable discussion going about the effects, for example, on wildlife. If I'd wanted the usual pedantic cobras I'd have used one of the other categories.

[New Judge]

I’m sure the scientists have thought of the practical problems, but….

“It would orbit 500km about Earth - roughly the same height as the International Space Station”

It’s a little higher than the ISS (which orbits at roughly 400km) but no matter. At 500km altitude the mirror would have an orbit period of (very roughly) 110minutes. That is, it would complete an orbit around the Earth in a bit under two hours. In doing so any reflection it provides would travel across the Earth’s surface at roughly 22,000kmh (or about 14,000 mph). So I fail to see how the project will provide any useful “daylight” for China (or anybody else) as the reflected light will traverse the entire country from East to West in under ten minutes.

Unless the scientists know something about satellite orbiting theory that I don’t, as mentioned in the report, for the reflection to remain stationary the mirror will have to be in a “geostationary” orbit (that is, orbiting the Earth every 24 hours). To achieve that it must be at an altitude (perhaps "distance" is more appropriate) of 37,000km. Perhaps a bit more problematic than that (as if it wasn’t problem enough) and although I haven’t worked it out, my intuition tells me that at an altitude of just 500km above the Earth, for most of the night the mirror would be completely hidden from the Sun in the Earth’s shadow and would be unable to reflect any light from it at all.

I think this is “Pie in the Sky” (pun intended) and a good candidate for April 1st.

[hereIam]

Just because we can do it (probably) doesn't mean we should. I hate nature being messed about with like this and it WILL affect wildlife, whenever mankind in his infinite wisdom decides to do something like this, it's usually nature and wildlife that pay the price !

[New Judge]

"Just because we can do it (probably)..."

As above, I don't believe we can.

"...and it WILL affect wildlife,"

But only for ten minutes (across the whole of China).

[Togo]

I did read about this some weeks ago TTT and it would appear that the science and capabilities to launch and deploy such a satellite are indeed in place. As indeed are the funds. No doubt partly due to our generous aid packages providing funds that allow the Chinese Government to swerve the onerous task of looking after their own unfortunates. However there did appear to be one flea in the ointment. The City that it is proposed to illuminate during the hours of darkness is the Chinese equivalent of our very own Manchester from the 50s and as a consequence spends most of the time under thick cloud cover or pollution and smog.

[Cloverjo]

An object in geo-stationary orbit remains fixed in the sky relative to an observer on Earth, NJ.

[ToraToraTora]

yes judge, so it's flawed at the moment. Yes Togo but as the judge points out their orbital mechanics are miles off so it looks like a non starter.

[Cloverjo]

So the reflection from this fake moon wouldn't traverse the surface of Earth in the way you mention.

https://en.m.wikipedia.org/wiki/Geostationary_orbit

[New Judge]

"An object in geo-stationary orbit remains fixed in the sky relative to an observer on Earth, NJ."

Yes I'm fully aware of that, jo.

The difficulty here is that the report suggests the mirror will orbit the Earth at a distance of 500km. At that distance it will orbit the Earth in around two hours and will thus not be geostationary. To be geostationary, as your link points out, the object must orbit the Earth at a distance of around 36,000km (and thus take 24 hours to complete one orbit) as I pointed out in my first post.

[Zacs-Master]

And directly above the equator (at that height).