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== Saint Elmo's Fire == | |||
On 20 February 1817,[note 1] during a severe electrical storm James Braid, surgeon at Lord Hopetoun's mines at Leadhills, Lanarkshire, had an extraordinary experience whilst on horseback: | |||
On Thursday 20th, I was gratified for a few minutes with the luminous appearance described above [viz., "such flashes of lightning from the west, repeated every two or three minutes, sometimes at shorter intervals, as appeared to illumine the whole heavens"]. It was about nine o'clock, P.M. I had no sooner got on horseback than I observed the tips of both the horse's ears to be quite luminous: the edges of my hat had the same appearance. I was soon deprived of these luminaries by a shower of moist snow which immediately began to fall. The horse's ears soon became wet and lost their luminous appearance; but the edges of my hat, being longer of getting wet, continued to give the luminous appearance somewhat longer. | |||
I could observe an immense number of minute sparks darting towards the horse's ears and the margin of my hat, which produced a very beautiful appearance, and I was sorry to be so soon deprived of it. | |||
The atmosphere in this neighbourhood appeared to be very highly electrified for eight or ten days about this time. Thunder was heard occasionally from 15th to 23d, during which time the weather was very unsteady: frequent showers of hail, snow, rain, &c. | |||
I can find no person in this quarter who remembers to have ever seen the luminous appearance mentioned above, before this season,—or such a quantity of lightning darting across the heavens,—nor who have heard so much thunder at that season of the year. | |||
This country being all stocked with sheep, and the herds having frequent occasion to pay attention to the state of the weather, it is not to be thought that such an appearance can have been at all frequent, and none of them to have observed it.[note 2] | |||
— James Braid, 1817 | |||
Weeks earlier, reportedly on 17 January 1817, a luminous snowstorm occurred in Vermont and New Hampshire. Saint Elmo's fire appeared as static discharges on roof peaks, fence posts, and the hats and fingers of people. Thunderstorms prevailed over central New England. | |||
== Fictitious force == | == Fictitious force == | ||
Revision as of 07:08, 1 August 2018
Things to use or delete. See Snippets.
Saint Elmo's Fire
On 20 February 1817,[note 1] during a severe electrical storm James Braid, surgeon at Lord Hopetoun's mines at Leadhills, Lanarkshire, had an extraordinary experience whilst on horseback:
On Thursday 20th, I was gratified for a few minutes with the luminous appearance described above [viz., "such flashes of lightning from the west, repeated every two or three minutes, sometimes at shorter intervals, as appeared to illumine the whole heavens"]. It was about nine o'clock, P.M. I had no sooner got on horseback than I observed the tips of both the horse's ears to be quite luminous: the edges of my hat had the same appearance. I was soon deprived of these luminaries by a shower of moist snow which immediately began to fall. The horse's ears soon became wet and lost their luminous appearance; but the edges of my hat, being longer of getting wet, continued to give the luminous appearance somewhat longer. I could observe an immense number of minute sparks darting towards the horse's ears and the margin of my hat, which produced a very beautiful appearance, and I was sorry to be so soon deprived of it. The atmosphere in this neighbourhood appeared to be very highly electrified for eight or ten days about this time. Thunder was heard occasionally from 15th to 23d, during which time the weather was very unsteady: frequent showers of hail, snow, rain, &c. I can find no person in this quarter who remembers to have ever seen the luminous appearance mentioned above, before this season,—or such a quantity of lightning darting across the heavens,—nor who have heard so much thunder at that season of the year. This country being all stocked with sheep, and the herds having frequent occasion to pay attention to the state of the weather, it is not to be thought that such an appearance can have been at all frequent, and none of them to have observed it.[note 2]
— James Braid, 1817
Weeks earlier, reportedly on 17 January 1817, a luminous snowstorm occurred in Vermont and New Hampshire. Saint Elmo's fire appeared as static discharges on roof peaks, fence posts, and the hats and fingers of people. Thunderstorms prevailed over central New England.
Fictitious force
A fictitious force (also called a pseudo force, d'Alembert force, or inertial force) is an apparent force that acts on all masses whose motion is described using a non-inertial frame of reference, such as a rotating reference frame. Examples are the forces that act on passengers in an accelerating or braking automobile, and the force that pushes objects toward the rim of a centrifuge.