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Fraser
2005-Jul-15, 05:00 PM
SUMMARY: An international team of scientists have embarked on a new project that will use cosmic rays from distant supernovae to help measure time here on Earth. The project is called CRONUS, for cosmic-ray produced nuclide systematics. When a star explodes as a supernova, it generates torrents of high-energy particles called cosmic rays. These penetrate earth and rock, and make minute changes to the elements that they're made of. Scientists will study the elements in these rocks to detect these altered elements, and use this as a way to the time for geological events, like glaciation and river erosion.

View full article (http://www.universetoday.com/am/publish/geologists_use_particles_earth_surface.html)

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dave_f
2005-Jul-15, 06:06 PM
So from what I understand, these measurements will help scientists determine the timeline of events in our Universe? Supernovae events are particularly important to understanding our recent (and distant) past. Just what were the Trilibytes killed off by anyways?

Opinions are welcome.

suitti
2005-Jul-17, 06:42 PM
Despite the xray image of sn1987a, which is the kind of
thing thought to generate cosmic rays, they are kind of
constant, and from every direction. Since they seem
constant, and morph the top layer of ground, they should
have something to tell us about the ground.

It would seem that you first need to be able to detect
cosmic ray induced changes in objects. Then, you need
to be able to calibrate that data against other time
measurements, like radioactive decay ratios, etc.

One would think that if something were exposed to cosmic
rays for only a part of the time since formation, that
the 'cosmic clock' would stop and start. That alone could give
you interesting information. For example, let's say you find
a shaped rock in a cave known to have had humans.
You might be able to get an absolute age of the rock
via radioactive decay, then find out how long it was
exposed to cosmic rays. If you subtract one from the
other, you might be able to find out how long it was in
the cave.

As an aside. I hear astronauts have an interesting way of
detecting cosmic rays. They close their eyes. Some
fraction of the events they detect have come through
the back of their heads.

Still want to be an astronaut? :rolleyes:

The trilobites may have been killed by your ancestors. Like
you, they were survivors. And, they were in competition
with the trilobites at the time. You are a magnificent specimen
at the top of the food chain, after all. In fact, your species has
invented a new spot at the top - unchallengeable.

Nereid
2005-Jul-22, 06:11 PM
Originally posted by dave_f@Jul 15 2005, 06:06 PM
So from what I understand, these measurements will help scientists determine the timeline of events in our Universe? Supernovae events are particularly important to understanding our recent (and distant) past. Just what were the Trilibytes killed off by anyways?

Opinions are welcome.
It's more about how to get better dates for earthly samples, and do more accurate geology - the cosmic rays signatures in rocks will - hopefully - tell more than the ages; environmental conditions at the time of formation (e.g. deposition of sediments).

To get a better handle on just what the sigs are, we need to understand more about how they form ... the incoming CRs are fairly well characterised (I think), but the inputs are mediated by a wide range of factors to produce rock sigs - the Earth's magnetic field, atmosphere (e.g. what's the time from CR-caused creation of an unusual nuclide in the atmosphere to its deposition?), etc - and these aren't so well understood.

This may be related to the work that goes into narrowing C14 age estimates - the historic rate of production isn't constant, with a range of factors now known to affect uptake in living critters.