Space Is Just a Little Bit Closer Than Expected

SpuriousLogic points out a BBC story which begins "The upper reaches of Earth's atmosphere are much lower than expected, a US Air Force satellite has found. Currently, the ionosphere — a layer of charged particles that envelopes the planet — is at an altitude of about 420km, some 200km lower than expected. The behaviour of the ionosphere is important because disturbances in its structure can upset satellite communications and radar."

how could we not have already known this?

[Anonymous Coward]

shouldn't we have already known this? this seems like really, really fundamental data.

below 30MHz

[FudRucker]

HF propagation is effected too...

Metric vs Imperial

[bangzilla]

Are we sure that they measured the distance in KM - what if it was miles, or furlongs, or rods, or perches....? I understand that this type of mistake has happened in the recent past.

Definition?

[Count_Froggy]

The distance to the edge of an atmospheric layer varies by definition, season, orbit, solar radiation conditions, and probably a variety of other conditions. If the edge measured was at 220km instead of 420km, is there agreement on the definition (as a start)? 220 km converts to about 137 miles. 420km converts to about 261 miles. (sorry, I'm in the US, I think in non-metric units.) The US requirement for astronaut wings is 50 miles. Since none of the people in orbit since 1960 (except for moonshots) went higher than the upper number, where they all in orbit within the ionosphere, according to the claimed 'old' definition? Unlikely.

Re:Erosion of the ionosphere?

[Reziac]

Actually, I had roughly that thought... "Did they measure its distance wrong the first time, or did it move closer to the surface??"

And if the latter... why? is it a temporary condition as the ionosphere flexes up and down, or a permanent trend? And if the latter, hasn't it moved awfully fast?? Unfortunately we don't have the longterm data to determine it either way... and I mean millions of years worth. A few tens of thousands may be meaningless on the scale of atmosophere/space interactions.

Stands as evidence that we don't understand the atmosphere well enough to purposefully fuck with it (as some stop-global-warming schemes propose to do).