Re:UFOs spotted off Irish coast under investigation
by smaili on Monday November 12, 2018 @08:56PM
(#18437778)
I know meteors seems to be a common theory, but do they normally travel that fast?
[ Parent
| on HN ]
Re:UFOs spotted off Irish coast under investigation
by mikeash on Tuesday November 13, 2018 @12:44PM
(#18442936)
I don’t think you can trust their assessment of its speed. There’s no way to reliably determine the speed of an unknown object of unknown size and distance.
Re:UFOs spotted off Irish coast under investigation
by SubiculumCode on Tuesday November 13, 2018 @02:42AM
(#18439360)
I was watching a meteor shower once, and after a few hours, the angle seemed to change. Instead of streaking across the sky, they appeared as a circle that got brighter and bigger before winking out....they were coming right at me.
This could explain the light in this video if it were a fairly large meteorite, maybe.
Re:UFOs spotted off Irish coast under investigation
by ceejayoz on Monday November 12, 2018 @09:40PM
(#18437992)
Mach 2? Yes. Far in excess of it.
Re:UFOs spotted off Irish coast under investigation
by garmaine on Tuesday November 13, 2018 @12:18AM
(#18438785)
They enter at orbital velocity or higher, so yes. Mach 20 or 30 would be on the low end. Of course depending on their shape and mass they lose a lot of it on the way down...
Re:UFOs spotted off Irish coast under investigation
by rbanffy on Tuesday November 13, 2018 @07:18AM
(#18440391)
And all the light the aircrews reported was kinetic energy before hitting the atmosphere.
Re:UFOs spotted off Irish coast under investigation
by Balgair on Tuesday November 13, 2018 @03:31PM
(#18444612)
https://en.wikipedia.org/wiki/Hypersonic_speed
The relevant regime for astronomical entities is in above the 'high-hypersonic' and into 're-entry speeds' (uber-sonic?). These are above Mach 25.
At these speeds, not only is the air no-longer considered an ideal gas, nor a two-temperature ideal gas, nor a dissociated gas (O2 and N2 become O and N along the wings), nor an ionized gas (electron temperature must now be considered), but rather a radiation dominated gas. Modeling these radiation dominant gases is very hard. As you increase the number of volumes to model, the computation load grows exponentially.
Re:UFOs spotted off Irish coast under investigation
by eof on Tuesday November 13, 2018 @01:39AM
(#18439115)
What I want to know is, do they tend to "bank and climb away"
Re:UFOs spotted off Irish coast under investigation
by walkingolof on Tuesday November 13, 2018 @03:50AM
(#18439602)
Far more likely that the observer interpreted it the wrong way, happens all the time.
Re:UFOs spotted off Irish coast under investigation
by infradig on Wednesday November 14, 2018 @01:55AM
(#18448080)
If they go straight thru the atmosphere and out then yes, that is exactly as they would appear.
Re:UFOs spotted off Irish coast under investigation
by Gustomaximus on Tuesday November 13, 2018 @07:02AM
(#18440340)
Do meteors ever dip into the atmosphere, light up, and skip away? Like a skipping stone?
Re:UFOs spotted off Irish coast under investigation
by philipkglass on Tuesday November 13, 2018 @07:24PM
(#18446208)
Basically, yes. Here's one famous example:
https://en.wikipedia.org/wiki/1972_Great_Daylight_Fireball
http://www.phys.ncku.edu.tw/~astrolab/mirrors/apod_e/image/0...
Re:UFOs spotted off Irish coast under investigation
by gnulinux on Tuesday November 13, 2018 @09:33AM
(#18441186)
It's very unlikely but definitely possible. If the meteor is fast enough and targets outer earth atmosphere, it an enter outer atmosphere, slow down, light up due to friction, then escape earth atmosphere vertically. The only problem with this scenario is that meteor has to be much faster than Mach 2, unlike what pilots reported. But it's easily possible they saw a Mach 12 meteor and thought it's Mach 2.