Explanation: Have you ever watched a lightning storm in awe? Join the crowd. Oddly, nobody knows exactly how lightning is produced. What is known is that charges slowly separate in some clouds causing rapid electrical discharges (lightning), but how electrical charges get separated in clouds remains a topic of much research. Lightning usually takes a jagged course, rapidly heating a thin column of air to about three times the surface temperature of the Sun. The resulting shock wave starts supersonically and decays into the loud sound known as thunder. Lightning bolts are common in clouds during rainstorms, and on average 6,000 lightning bolts occur between clouds and the Earth every minute. Pictured above, an active lightning storm was recorded over Athens, Greece earlier this month.
Wow did that all happen at once or is that a time lapse photo? If it all happend in one shot that is one cool dude.
Re: APOD: Lightning Over Athens (2010 Jul 20)
Posted: Tue Jul 20, 2010 6:32 am
by Beyond
WOW!!! i've never seen so much lightning in such a small area. The photographer was fortunate indeed to be at the right spot(under cover)at the right time.
Was this image altered? Because I don't see a shadow from the man, pointing away from the main lightning bolt. It could be that the street light overpowers it, but I think there should at least be some shadow.
Re: APOD: Lightning Over Athens (2010 Jul 20)
Posted: Tue Jul 20, 2010 7:52 am
by vger
I wish the caption had mentioned some recent speculation that suggests that for lightning to form, it requires an initial ionization event of the atmosphere and that this ionization is often caused by a cosmic ray. This would mean that the location of the lightning is determined by extraterrestrial events. Here is a link to a nice little article that discusses it. http://www.scientificamerican.com/artic ... -lightning
Re: APOD: Lightning Over Athens (2010 Jul 20)
Posted: Tue Jul 20, 2010 12:03 pm
by stargazerjim
Looks like this is a classic time exposure with the individual standing dead still for several minutes, all other moving objects, stars, people, critters, etc. not shown because of high f/number and their movement... that would also eliminate shadow of the individual standing... Alone in a whole bunch of invisible action, leaving us to focus on the lightning instead!
Re: APOD: Lightning Over Athens (2010 Jul 20)
Posted: Tue Jul 20, 2010 12:04 pm
by orin stepanek
inertnet wrote:Was this image altered? Because I don't see a shadow from the man, pointing away from the main lightning bolt. It could be that the street light overpowers it, but I think there should at least be some shadow.
Look again; there is a shadow behind the man. A little over toward the right. I wonder if he is under the arch. What are the dark spots in the photo? Maybe some dirt specks on the lens?
Re: APOD: Lightning Over Athens (2010 Jul 20)
Posted: Tue Jul 20, 2010 1:13 pm
by owlice
From the link a few posts above:
The photo above shows just a snippet of an amazing electrical storm that lashed Athens, Greece on June 28, 2010. It’s actually a sequence of 42 stacked shots, caught in Olympic Stadium, during a severe early afternoon thunderstorm. It took me about 30 minutes to capture 51 lightning shots; nine shots were ruined because of excess brightness. These awesome cloud-to-ground bolts were striking the surface approximately five hundred feet in front of the camera.
Water droplets show it's not a time exposure
Posted: Tue Jul 20, 2010 1:41 pm
by gar37bic
I see individual droplets of water falling off the bridge, so this can't be a normal time exposure. If it were, the droplets would be streaks if they were visible at all. So I suppose it could be either a rapid series of multiple exposures (and the multiple droplets are the same drops in different points of their fall) either on the same film frame or combined afterwards additively, or a short exposure with fast film. Looking at the droplets there is a very slight elongation, so working out the gravitational acceleration and the degree of elongation, you might be able to get an idea of the shutter speed. But the process of falling also distorts the droplets, so it's not simple.
... and now I see the explanation just above me, that confirms my first supposition! I don't know whether to be happy that I was right, or embarrassed that I didn't read it!
gar37bic wrote:I see individual droplets of water falling off the bridge, so this can't be a normal time exposure. If it were, the droplets would be streaks if they were visible at all.
Note that the image is just a stack of "normal time exposures". The exposure time of each subframe was 3.2 seconds. It is normal in shots like this to see the raindrop motion frozen. That's because the drops are only captured while the lightning is illuminating them. The exposure time isn't the relevant factor, but the lightning duration. You'd get the same thing if you opened the shutter, triggered a flash, and then closed the shutter.
Re: APOD: Lightning Over Athens (2010 Jul 20)
Posted: Tue Jul 20, 2010 3:59 pm
by zbvhs
If they get cumulus cloud buildups that produce lightning, why do they not also have tornados? I have never heard of a tornado occuring anywhere but the central plains of North America. The Mediterranean would be a great place for waterspouts. Do they just not make the news?
Re: APOD: Lightning Over Athens (2010 Jul 20)
Posted: Tue Jul 20, 2010 4:15 pm
by moonstruck
After watching peterbradford's video it looks like the "cool dude" might have been vaporized. After his body disappears you can still faintly see his ghost still standing there for a little while.
Re: APOD: Lightning Over Athens (2010 Jul 20)
Posted: Tue Jul 20, 2010 5:32 pm
by neufer
owlice wrote:From the link a few posts above:
The photo above shows just a snippet of an amazing electrical storm that lashed Athens, Greece on June 28, 2010. It’s actually a sequence of 42 stacked shots, caught in Olympic Stadium, during a sEVERE early afternoon thunderstorm.
Click to play embedded YouTube video.
Re: APOD: Lightning Over Athens (2010 Jul 20)
Posted: Tue Jul 20, 2010 8:44 pm
by RedTussock
Gosh do you humans not know what lightning is ... it is a tear in the temporal barrier between this dimension and a neighboring dimension. It is caused by an anomaly in the temporal void, caused by mis-use of the 7th sense, which humans have yet to discover, aural awareness. But it is an impressive photo, I wonder is it a time lapse, and if so how did the gentlemen playing with Gods patience stand still for so long ...
Re: APOD: Lightning Over Athens (2010 Jul 20)
Posted: Tue Jul 20, 2010 8:59 pm
by bystander
RedTussock wrote:But it is an impressive photo, I wonder is it a time lapse, and if so how did the gentlemen playing with Gods patience stand still for so long ...
Q: You are cooking dinner on the camp stove when you hear distant rumbles of thunder.
Your tent and a large open sided picnic shelter are nearby.
Your vehicle is about ¼ of a mile away parked at the trail head. What should you do?
A: Go to your vehicle! The tent and picnic shelter are NOT a safe places.
Wait 30 minutes until after the last rumble of thunder before going back to the campsite.
Dead cows lined up along a metallic fence. Lightning struck the fence,
and the electrical current traveled along the fence killing the cows.
Photo Courtesy Ruth Lyon-Bateman
Re: APOD: Lightning Over Athens (2010 Jul 20)
Posted: Wed Jul 21, 2010 3:50 pm
by zbvhs
The guy is relatively safe given the light standards and railings above him or if the core of the storm is more than five miles away. (Although lightning bolts have been known to reach out as many as ten miles from the storm.) If ever caught out in the open and your hair starts standing in end and your skin starts tingling, lie flat on the ground to avoid forming a point source.
Re: APOD: Lightning Over Athens (2010 Jul 20)
Posted: Wed Jul 21, 2010 5:06 pm
by neufer
zbvhs wrote:
The guy is relatively safe given the light standards and railings above him or if the core of the storm is more than five miles away. (Although lightning bolts have been known to reach out as many as ten miles from the storm.) If ever caught out in the open and your hair starts standing in end and your skin starts tingling, lie flat on the ground to avoid forming a point source.
Do *NOT* lie flat on the ground!!!
Lightning that hits the ground has been known to kill cows while leaving farmers
standing nearby completely unharmed due to a strong HORIZONTAL electrical potential.
Crouch down and put feet together! Place hands over ears to minimize hearing damage from thunder.
Re: APOD: Lightning Over Athens (2010 Jul 20)
Posted: Wed Jul 21, 2010 5:23 pm
by Chris Peterson
neufer wrote:Do *NOT* lie flat on the ground!!! Crouch down and put feet together! Place hands over ears to minimize hearing damage from thunder.
Also, if you are with other people, separate. The most common thing that happens when you are hit by lightning is that your respiration is shut down. Lightning victims generally die of asphyxiation. If somebody is present to give artificial respiration, most lightning victims survive. But if you're all together in a group, a strike may knock everybody out at once.
Re: APOD: Lightning Over Athens (2010 Jul 20)
Posted: Wed Jul 21, 2010 10:14 pm
by ChrisKotsiopoulos
Hi.
Thank you all for your comments. I'm glad you like it!
I think that I was relativelly safe because I stood there for about 5 seconds when the storm was far. Then i went under a big bridge (the one at the right) and enjoyed the light show.
Also many thanks to Drs Nemiroff and Bonnell for publishing my photo.
Chris.
Re: APOD: Lightning Over Athens (2010 Jul 20)
Posted: Wed Jul 21, 2010 10:23 pm
by Beyond
How come this Apod was posted twice today?? Lack of communication???
Lightning Over Athens
I'll wait until the storm is over. 
It does make a nice photo though! 