NLC discussion

Update (2013/06/11): I noticed that one of the tweets was out of order. I've put it back in the correct chronology.

This post comes about due to noctilucent cloud (NLC) images from last night. It is a conversation I had on Twitter today. A few people re-tweeted (RT) my NLC images and, out of curiosity, I looked at a couple of profiles to see if they were people I might want to follow. @ClimateRealists caught my eye because their next tweet was directed at my local weatherman (Paul Hudson) and included an astronomical connection:

I hadn't heard of a link between meteorites and noctilucent clouds so I responded.

The meteorite and moon reference turns out to be this interesting story that I missed when I was away travelling. The asteroid mentioned may have been one of the few that have gone by in the past few months or so.

I wanted to quickly clear up that my mention of "human history" was certainly not meant to imply that humans are the cause for NLCs (I was unaware of evidence one way or the other on that so was staying agnostic):

I read the Science@NASA article and was interested to find out that they said that observations showed that "meteor smoke" was the nucleation point for the water vapour that freezes and causes NLCs. There isn't much water vapour at the altitude of NLCs (80 km) as the scale height of water vapour is about 2 km. The Science@NASA article says that an increase in methane in the atmosphere is providing the extra water vapour that enhances NLCs so that we see them more now.

NLCs are not a local phenomenon like normal clouds. They are at very high altitudes - about 8 times higher than passenger planes - so can be seen over very wide areas. In fact, @mars_stu and @yodatheoak's images of the NLCs seemed to be exactly the same clouds I was looking at last night.

In Tweetdeck I saw that they were using two different operating systems to send tweets.

This was true. My next door neighbours had turned up at the door saying they thought a squirrel was stuck and would I help. We couldn't see up the drain pipe (it wasn't straight) so we couldn't tell if it was still there or not. I suggested we use a hosepipe to put a little bit of water on the roof and check if the water emerged at the bottom. I didn't want to drown the squirrel, just test if it was still there. It turned out that it was and a slightly damp squirrel darted out of the drain pipe and scampered off.

The meteor connection is an interesting idea. I'm not convinced that meteors alone can be the cause of NLCs as I don't really buy @ClimateRealists's argument that people had just referred to them as "strange clouds" before 1885 so they were there, they were seen, but unreported. It is possible that this assertion is true but I'd like to see something describing NLC-like phenomena from earlier dates before I'll take it seriously. Perhaps a historian of astronomy would be helpful here.

If they weren't seen before 1885, there is something different between before and after the late 19th century. The Science@NASA story that @ClimateRealists pointed me to suggested it was due to increasing methane. @ClimateRealists seem to object to that idea although @ClimateRealists's website does state that there has been climate change so perhaps they don't object. Perhaps they were just against the idea of a man-made cause and kept missing me telling them that I wasn't saying anything about that. I was only challenging their assertion that NLCs have been this bright and regular for astronomical timescales.

I can't help but worry that it is all my fault when someone seems to be at crossed-purposes with me for so long in a discussion especially when I've worried about that from the beginning. I get frustrated because I ask if there has been a misunderstanding and am told there isn't despite it increasingly seeming to be the case. This seems to happen semi-regularly for me. My frustration is largely at myself for not knowing what I'm doing wrong. Is it my use of language? Do I initially come across as aggressive? Am I mis-reading what the other person is saying? Am I losing the ability to understand other people? What can I do to improve? Ideas welcome.

Anyway, it would be pretty awesome if @ClimateRealist's suggestion, that "fall out" from the Moon/meteor incident had escaped the Moon and had contributed to this season's NLCs, turned out to be correct.

Posted in astro blog by Stuart on Sunday 09th Jun 2013 (23:19 BST) | Permalink

Noctilucent Clouds

Over the past week or so, the UK has been getting some pretty good views of noctilucent clouds. These are amongst the highest clouds in Earth's atmosphere and are apparently at a height of about 80 km. They are usually too faint to be seen and so we see them when the Sun is below the horizon.

Stuart Atkinson of Cumbrian Sky has been providing great Twitter alerts to the noctilucent cloud (NLC) displays over the past week and has some great photos of the displays on his blog.

I'd never seen noctilucent clouds before so, the other night I wasn't entirely sure if the bright clouds in the north were NLC or not. I don't think they were although I may have caught some in the bottom right corner of a photo behind some low level cloud. Tonight, after seeing an ISS pass with my dad, I headed up our street to get a view to the north just in case. I was so glad I made the short walk as I saw the start of a really amazing display that was unmistakably NLC. I jumped in the car and headed north of the city to get less light-polluted views. I took photos from a couple of places and I've included them below. Click on the pictures for the bigger versions on Flickr.


Noctilucent clouds

Noctilucent clouds

Noctilucent clouds

I've included a video I created using ninety 10 second exposure photos. I had to stop because my camera lens started to fog up.

Mark Shaw has a really great panorama of the NLC activity taken from the edge of the Peak District near Glossop.

Posted in astro blog by Stuart on Sunday 09th Jun 2013 (03:10 BST) | Permalink

Travels in time and space

A few weeks ago I found myself on an interesting journey in space and time. I set off on a Friday, travelled through Thursday, Friday, Saturday, Friday, Saturday and finally arrived about 14 hours later on the Friday before I'd set off. I did all of this without a DeLorean DMC-12 or a little blue box. All it took was an international flight and a series of complicated time zone boundaries.

My flight was from Auckland, New Zealand to Vancouver, Canada and it set off around 8pm local time on a Friday. As you can imagine, this flight goes from the southern to northern hemisphere across the Pacific Ocean and so crosses the International Date Line. Actually, because various island nations have chosen to redefine which time zone they are in, my flight crossed the International Date Line five times! Before I go any further I had better provide a diagram showing the middle of the flight. It will help.

Flight path
My journey in space and time CREDIT: Stuart
My flight is the black line and the International Date Line is shown in red. I've labelled the five crossings of the date line (B, C, D, E, F) as well as one other point (A). It is as accurate as I could be making sketches on a scrap of paper in the middle of the night whilst sandwiched between two people and illuminated only by the map on the seat-back screen. Let's start at point A which marks the boundary of the UT+12 and UT+13 time zones. I reached this point at roughly 10:00 UT Friday so I instantly went from 22:00 to 23:00 local time Friday.

Point B - my first crossing of the date line - occurred at about 10:50 UT Friday. That meant I went from 23:50 local time (UT+13) Friday to 23:50 local time (UT-11) Thursday. Ten minutes later the local time clock rolled over into Friday. I reached point C at 13:17 UT Friday which was now 03:17 local time (UT-10) Friday and crossed the date line again so went to 02:17 local time (UT+13) Saturday.

At around 15:00 UT Friday I reached point D - the date line - so went from 04:00 local time (UT+13) Saturday to 04:00 local time (UT-11) Friday. After crossing the equator I fell asleep for a while as I was tired and the in-flight map isn't the best thing to keep you awake even if you are time travelling. Despite being asleep, a little later I crossed the date line at point E going forward to Saturday again and then back to Friday when I crossed the date line at point F.

After 11000 km, I eventually landed in Vancouver sometime around 2pm local time on the Friday. That meant I arrived roughly 6 hours before my departure time. This sort of time travel is no good though as it left me seriously jet-lagged. Still, I recovered and no grandfathers were harmed.

Posted in astro blog by Stuart on Thursday 06th Jun 2013 (02:47 BST) | Permalink
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