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Re: Dino Extinctions & Space Debris



>Now, if we could find Pluto (a tiny little thing--and I hope I'm 
>remembering correctly that it is the planet that was found this way)
>because of its effect on the orbits of the other planets...and it 
>seems to me we've discovered a double star or two where the one twin 
>is dark in distant parts of our galaxy by watching the perturbations 
>of the orbit of the lighted twin...then why wouldn't we KNOW where 
>Nemesis was, and if it existed at all?

Pluto was discovered in 1930 due to perturbations in the orbits of Uranus
and Neptune. It has a sidereal period (year) of 247.7 years. Uranus and
Neptune have sideral periods of 81.01 and 164.8 respectively (Neptune was
found in a similar way). This means that measurments taken over years or
tens of years are sufficient to calculate their positions.

Nemesis, however, is thought to have a period of 26 million years. Many
times longer than either Pluto or many binary star systems. It would have
last reached it's closest point to the Sun between 5 and 13 million years
ago. We're going to have to hang around a lot longer (probably 13-21 million
years) before we notice any gravitational effects on the solar system.

On the point about spotting companion stars in distant parts of the galaxy,
it is often easier to spot these things from an outside reference point then
when you are spinning around in the system. Would we know anything like as
much about the Milkey Way if we weren't able to look at distant galaxies?

Finally, in science we can never KNOW anything for certain, only form
theories to explain observed phenomen and disprove them. The Nemesis theory
explains an observed phenomen, the apparent regularity of extinction events,
and has not yet sufficiently been disproved.

Now I accept that it is a bit unlikely. I'm not even sure that the mass
extinctions are even related. But there does appear to be a certain
regularity to them, and the Nemesis theory does offer an explanation.

On a positive note, if Nemesis does exist, we don't have to worry about it
for a long time. As long as we don't create our own mass extinction event,
that is. Not so positive, now I think about it.

Changing the subject a little, I was watching "Howard The Duck" tonight. It
has made me realise two things: 1. this is a very stupid film, and 2. if we
keep making films like this we should be grateful for any impending
extinction events. There was one bit which peaked my interest. There was a
scene where a bunch of scientists were sitting around a large skull. It
looked mammalean, or at least therapsid. Anyone know what it was?

James Shields