The best conditions for large dendritic snow crystals are a high amount of supersaturation of the air and temperatures between about -10 and -20 Celsius (these conditions being within the cloud where they are forming, not the conditions on the ground which could be very different).



Dr. Libbrecht who was featured in Veritasium's video also has a nice webpage all about snow crystal science and photography here: http://www.snowcrystals.com/

Do not forget no wind.  Wind will rip the crystals apart, both in the air and on the ground, where sastrugi will form.  This is very hard snow in which you leave no tracks, it's challenging to cross on skis when there are tall ridges, and on foot you might need crampons to get a footing even in moderate slopes.  The water content quickly becomes 1 to 3, even though the temperature is good for fluffy snow between -10 and -20C.

You're right, even when we have perfect conditions in snow growth regions, here at the coast we get high winds oftentimes which prevent the kind of accumulation we could otherwise get....for example JFK often comes in with lower totals than inland locations even with temps in the lower 20s, because the high winds rip the crystals apart at the coast.

Wat, Mid, is there any way to find out in post analysis what kinds of conditions were present for a given storm?  Specifically, I'm talking about the January 2016 blizzard which was the biggest snowstorm on record here during a super el nino (which is when our biggest ones usually are), JFK airport measured 30.7 inches of snow which is the first 30" snowstorm of record in the NYC area (it's only 4 miles from me so I use their numbers for my totals.)  The liquid equivalent was also right at 3.00"  The ironic thing about this storm is.....these incredibly high totals happened WITH very high winds..... there were 12 straight hours of blizzard conditions at JFK, something I've never experienced before.  This means 12 straight hours of wind gusts above 35 mph and visibility below 1/4 mile! The area of highest snowfall totals for near sea level locations ran west-east from Allentown, PA to JFK, NY.   The following January we had a snowstorm like this again, but it lasted half as long (6 straight hours of blizzard conditions) and with about half the snowfall totals.  But it was also very photogenic as nothing could be seen outside all day long it was like a huge wall of white!

https://en.wikipedia.org/wiki/January_2 ... s_blizzard


The storm ranked as a Category 5 "extreme" event for the Northeast on the Regional Snowfall Index, and a Category 4 event for the Southeast.^[4][5] It is the most recent winter storm to rank as a Category 5 winter storm, and the first to do so since the 2011 Groundhog Day Blizzard. 
Snowfall across New York City and Long Island was more intense than initially forecast, falling at rates of 3 in (7.6 cm) per hour at times. Before the travel ban was implemented, buses struggled to make their routes and long delays were common.^[137] At Central Park, a storm-total accumulation of 27.5 in (69.8 cm) was observed, the highest total on record for the city since observations began in 1869. This surpassed the previous record of 26.9 in (68.3 cm) measured during the February 2006 blizzard.^[138][139] Accumulations reached an all-time record high of 30.5 in (77 cm) at John F. Kennedy International Airport.^[118][139]

these incredibly high totals happened WITH very high winds

Measuring snow depth in windy conditions is difficult, since the snow doesn't settle evenly.  Where I live we can sometimes get around 40 cm fresh snow in a day.  Not every winter, but sometimes several times a winter.  That's enough for me in such a short time, which I can usually shove away in an hour, and not faster than what plow trucks can handle to keep traffic going.
The last snowy winter was in 2018 (tour around my house).  Right now we have just 6 cm of snow and nothing but cold, dry weather in sight, but at least something to light up the long nights.

these incredibly high totals happened WITH very high winds

Measuring snow depth in windy conditions is difficult, since the snow doesn't settle evenly.  Where I live we can sometimes get around 40 cm fresh snow in a day.  Not every winter, but sometimes several times a winter.  That's enough for me in such a short time, which I can usually shove away in an hour, and not faster than what plow trucks can handle to keep traffic going.
The last snowy winter was in 2018 (tour around my house).  Right now we have just 6 cm of snow and nothing but cold, dry weather in sight, but at least something to light up the long nights.

Wow that's beautiful!  I had heard that Norway had recently gotten a major snowfall (around 20-30cm) but I guess that was in a different part of the country?

I had heard that Norway had recently gotten a major snowfall (around 20-30cm) but I guess that was in a different part of the country?

Since when did November snow in Norway become international news?    Maybe it was about Bodø, where up to 40-50 cm fell in a day recently, which will cause delays in a major city.  Here in Oslo we got our first snow 19th October, but October snow almost always melts again.  Looks like proper winter snow here began 30th November this winter.

I had heard that Norway had recently gotten a major snowfall (around 20-30cm) but I guess that was in a different part of the country?

Since when did November snow in Norway become international news?    Maybe it was about Bodø, where up to 40-50 cm fell in a day recently, which will cause delays in a major city.  Here in Oslo we got our first snow 19th October, but October snow almost always melts again.  Looks like proper winter snow here began 30th November this winter.

Haha well technically it was early December snow (I think....because it was only mentioned this morning.)  I think the one you mentioned was the one, it caused major delays and stoppages.  Don't know why it was mentioned to be honest, I think maybe because the weather is super boring here, 10% snow coverage across the entire country which is historically low and this is the latest  TWC has ever gone without naming a snowstorm.  Even highly elevated cities like Denver have not seen any measurable snow this season, and along the east coast it is the warmest fall on record.
October snow is surreal, especially with the leaves still on the trees.  I've only seen that once here....in 2012.  It actually snowed a few inches here but much heavier not too far inland (as in close to a meter of snow in the mountains).  With thunder and lightning too-- the kind of wet snow that can cause a lot of tree damage.  A year after that we had Sandy in late October and a 25 hour power outage with 100 mph winds and then a 20-30cm snowstorm a week after that in the first week of November here.

The earliest snow in the Oslo region that I know about, because I remember it in 1985, was 5th September.  Flurries even at sea level, but settling on the ground only above 400 m.  Pretty large amounts, even.  The latest I've experienced was 1st June, but not settling on the ground.  I've experienced snow settling on the ground in all months, but for July and August only at high elevations or very far north.  But this really belongs to the unusual weather thread...

A little inspired by the video I tried to photograph some snowflakes today.  I don't have any macro lenses, so my best option was my mobile phone, which has its limitations.  Anyway, there's some very light snow today, no wind and -8C, so this should mean idea conditions for some good snow crystals (around -15C at the cloud base seems reasonable).  I put a piece of cardboard outside and let it cool down, and then let some snowflakes settle.  Still, many snowflakes have been "damaged".  I suppose they can sublimate or get torn.  Had I had a proper macro lens, I think some nice photos would be possible.

A little inspired by the video I tried to photograph some snowflakes today.  I don't have any macro lenses, so my best option was my mobile phone, which has its limitations.  Anyway, there's some very light snow today, no wind and -8C, so this should mean idea conditions for some good snow crystals (around -15C at the cloud base seems reasonable).  I put a piece of cardboard outside and let it cool down, and then let some snowflakes settle.  Still, many snowflakes have been "damaged".  I suppose they can sublimate or get torn.  Had I had a proper macro lens, I think some nice photos would be possible.
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These are still very good!  You don't actually need a macro lens, you can get a close up filter kit, I find these very useful and quite inexpensive and you can put them on any camera or lens that has filter threads.  The depth of focus is shallow but you can use focus stacking software which is fairly common (and some of them are free).

Another fun black hole and general relativity video from ScienceClic. What does it mean for space and time to switch roles inside a black hole, and how can we visualize it?

Time / Space inversion inside a Black hole.

Recently Derek Muller made a video about a fascinating topic that blew some minds apparently:


[youtube]bHIhgxav9LY[/youtube]

The video has become a bit controversial between fellow physicists. This time Veritasium seems to be just partially correct and he might have introduced a new missconception trying to overcome others. I find this discussion fascinating. My favorite "debunk" of Derek's video is here (spoiler: Veritasium is more correct than most though but still his point is not fully correct):

[youtube]2Vrhk5OjBP8[/youtube]

Embedding videos doesn't seem to work anymore (at least, not for me), so here's a direct link for the "debunk" video.

Whether correct or not is a matter of being clear about the assumptions.  A 300,000 km long copper wire would of course never work for a number of reasons.

My favorite "debunk" of Derek's video is here (spoiler: Veritasium is more correct than most though but still his point is not fully correct):

I enjoyed that video as well as this one, which approaches it from the theoretical/simulation side. It shows the propagation of electric field along the wires and throughout space, and the current through the bulb over time. The agreement between this approach and the experimental data from the other video is wonderful. 

Response To Veritasium - Electricity Propagation Time Problem (Ben Watson)

Veritasium is making a number of important and correct points about how electricity travels, but I agree with many others that the way he describes it is confusing and potentially misleading as well. 

It takes a few times the light travel time through the circuit for the full current to flow through the bulb (steady state behavior), but it only takes the light travel time directly from the switch to the bulb for the initial current to begin to flow, the magnitude of which depends on the geometry and elements of the circuit. The transient behavior between the first burst of current and the steady state behavior is complicated and interesting as well, and a lot of video responses explore that in great detail, though I feel it isn't what Veritasium wanted to dwell on too much. His main point is that the immediate response is faster than most intuitions might suggest, because it is not forced to only flow through the wires.

His point about the Poynting vector and showing that the energy flows more directly from the battery to the bulb through space is also potentially misleading. Yes, the arrows are oriented like that, but the energy density is greatest close to the wires (since magnetic field strength around a long straight wire goes as 1/r.) And when claiming that the energy is carried through the fields and not the electrons in the wires... well, that's more of a philosophical interpretation. Again, the energy density is greatest near the wires, and the fields are generated by the movement of electrons in the wires. So... ¯\_(ツ)_/¯

Perhaps the simplest distillation of Veritasium's video is that electricity involves the movement of charges, but the movement of charges can induce other charges far away to move, even if there is nothing but vacuum between them, and that influence goes at the speed of light.

How does movement of charges induce other charges far away to move, Wat?  Even if there is nothing but vacuum between them?  Are there some quantum factors involved here?