If you have ever been privy to the phenomenon of light pillars, then you know it is truly an amazing sight. They appear when the weather is extremely cold and form vertical columns of light beaming directly towards the sky. Here a compilation of pillars of light for December 2015.
They sometimes look like multiple fireballs heading to the sky:

© Alex JuliaThe mysterious pillars of light phenomenon over Yekaterinburg on December 20, 2015.
They are created when light from the sun, moon, streetlamps, or any terrestrial source, reflects on the surface of a flat piece of ice crystal as shown in the diagram below:

© Strange sounds
When the light source is close to the ground, the light pillar appears above the floating crystals.

© Stanislav GilyazovLight pillars in the night between 18 and 19 December 2015 at Sterlitamak.
When the light comes from the sun or moon, the light pillar can appear beneath them, too, as the light refracts through the crystals.

© Stanislaw GilyazovAgain this eerie sky phenomenon over Sterlitamak.
It is truly amazing!

They change color according to their source over Sterlitamak.
Light pillars typically scrape the night sky in polar regions.

© Konstantin LifanovIs there a big party going on in this arctic Russian city?
But sometimes the vertical columns of light appear along with frigid temperatures at lower latitudes.

© Konstantin LifanovThese light pillars look like dancing bodies in the night sky. Image shot on December 18, 2015.

© Yuri YaschenkoThese beams of light were captured with a green aurora on December 17, 2015.

© Egor ZagrebinLike a multicolor wall beaming to the sky over Izhevsk on December 18, 2015.
What an
awesome sky phenomenon!
Wouldn't they appear um,curved ?
Even rainbows are bent,in synchronicity with the eh,ball,aren't they ?
Interesting image the last one is.