Starship Asterisk*

Steve F Craig wrote:
Coming off the big main ball of fire was a tail of yellow flame that fanned out leaving a monstrous boiling con trail. Inside the outwardly fanning flame was a very bright white flame which came to a sharp point behind the flaming meteor. The white flaming tail wasn't much longer than the diameter of the main fireball. My uncle wondered allowed if 'a satellite was dropping out of orbit'. I said, ' that is much to big for that', appearing much larger than the mid-day sun and moving so fast. The fire ball looked like it was on a trajectory to hit the earth at any moment. However the fireball headed off into the northeast disappearing behind it's billowing thick con trail. I thought a mushroom cloud would mark it's impact point and start a massive fire in the ripe wheat fields at any second. I could hardly believe it when I heard the meteor went back into space.>>

Bravo4707 wrote:Interesting picture and a good selection for APOD. Someone had to be pretty quick to catch it on film! (It's the 1970s.)

The comment in the caption describes the effect of the meteor passing through the earth's atmosphere and then returning to space as like a stone skipping off a lake. Perhaps a better description is the meteor punching through the atmosphere and departing, having missed the earth.

True, the atmosphere increases in density with decreasing altitude (let's say, distance toward the earth's center). However, the resultant outward force from differential drag on the top and bottom of the meteor should be extremely small, and should be overwhelmed by the force of gravity pulling the meteor toward the earth's center. The atmosphere goes from 1 ATM to zero in about 100,000 m (100 km), so the gradient of density across the leading face of a 3 meter crossection projectile is very small. Even with very turbulent drag, the differential outward force (away from earth's center) should be orders of magnitude less than the force of gravity.

If so, then the meteor will actually curve its path toward the earth's center (like a falling stone), rather than curve away from earth's center (like a skipping stone) while it is in transit through the atmosphere. BTW, the loss of speed from drag force has nothing to do with this effect. After all, the skipping stone is slowed by the surface of the water, but still manages to change direction upward.

I haven't gone through the calculations, so these comments amount to a thought experiment. I'd be interested to see someone actually calculate the difference in outward and inward forces from differential drag versus gravity. My guess is at least several orders of magnitude in favor of gravity!

ta152h0 wrote:I remember this and i think the meteor actually came back a year later and crashed somewhere on the planet. he was below the keyhole.

http://en.wikipedia.org/wiki/The_Great_Daylight_1972_Fireball wrote:
# 1972-08-10, US19720810 at 15 km/s above United States and Canada (first scientific observation)

<<The Great Daylight 1972 Fireball (or US19720810) is an Earth-grazing meteoroid which passed within 57 kilometres of the surface of the Earth at 20:29 UTC on August 10, 1972. It entered the Earth's atmosphere in daylight over Utah, United States (14:30 local time) and passed northwards leaving the atmosphere over Alberta, Canada. It was seen by many people and recorded on film and by space borne sensors.

Analysis of its appearance and trajectory showed it was a meteoroid about 3 metres (9.8 ft) (if a carbonaceous chondrite) to 14 metres (46 ft) (if made of cometary ices) in diameter in the Apollo asteroid class in an Earth-crossing orbit that would make a subsequent close approach to Earth in August 1997. In 1994, Czech astronomer Zdenek Ceplecha re-analysed the data and suggested the passage would have reduced the meteoroid's mass to about a third or half of its original mass.

The meteoroid's 100 second passage through the atmosphere reduced its velocity by about 800 metres per second (2,600 ft/s) and the whole encounter significantly changed its orbital inclination from 15 degrees to 8 degrees.>>

StACase wrote:Very interesting, we have photos like this, and nothing of "UFO"s. One would think that if such a rare thing as a daylight meteor can be caught with such a great photo, that by now there would be good photos of "UFO"s. There aren't. Perhaps the reason is that there aren't any to photograph.