1 For automobiles a taxpayer uses for business purposes, the portion of the business standard mileage rate treated as depreciation is 23 cents per mile for 2013, the same as in 2012. 2  The IRS also publishes a standard mileage rate for the use of a vehicle for medical or moving purposes.
What causes continuous rolling thunder when no lightning visible? Thunder is caused by the rapid expansion of super-heated air as electrical spark passes through. What causes the long (ie some several seconds) of rumbling when no lightning is visible even at night during tropical downpours?
It makes an uneven, jumbled sound, because the lightning that created it is jagged and uneven (see image at right) Thunder also sounds different depending on how far away you are from the lightning, what type of discharge it is (intracloud, cloud-to-ground), and which part of the lightning you hear first. You see a bright flash, followed seconds later by a soft, crackling sound, then a loud, startling crash.