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Re: What?

Hello Julia and list,

>Hello list,
>
>The following is from a CNN report regarding the possibility of a real
>'Deep Impact'.    Does anyone understand the last sentence?
>
>Sound far-fetched? Not to astrophysicist Jack Hills, a real-life expert
>on killer rocks in space.
>Hills says the current million-dollar-per-year monitoring program has only
>succeeded in finding about 10 percent of the objects that might threaten
the >planet.
>
>"So the other 90 percent can hit at any time without any significant
warning," >he says. "They could be potentially impacting on the other side
of the Earth >right now, and we would be so far blissfully ignorant."
>
>Best Regards,
>Julia
>(If it ever stops raining here, I'll give the list a break.)

As you wrote in the later mail, itīs possible that he meant approaching
asteroid or comet but there can be a big impact on the other side of the
Earth right now and you can notice nothing for a while.

If there is an asteroid impact now. It will takes some times (several
minutes) for the effects (fastest shockwaves) of the impact on the other
side of the planet to reach you. If the impact is big enough, you might even
feel those shockwaves.

One of the first impact effects which can be observe on the other side of
the planet is the flash of the explosion which the moon reflects. But this
is the case only when the moon is in suitable position and when the impact
is big enough.

Because we are living in the world of direct broadcasting, there is a chance
that global tv-networks (CNN or some other) might be the fastest way to get
the first glue about the impact just before the first shockwaves arrives.

Can anybody tell how soon the fastest shockwaves from the impact will reach
the other side of the planet? And how big the impact has to be that one can
actually feel the shockwave from the other side of the Earth? 

I think that I have read somewhere that shockwaves (changes in the air
pressure) from the Tunguska-explosion went at least twice around the world
in 1908.

Best regards,

Jarmo
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