question on classical physics this time

[questionposter]

If I have a meteor of uranium, could it slam into the Earth with enough force to compress it and cause a nuclear explosion?

[MigL]

I believe regular uranium 238 is a neutron moderator and so any naturally occurring uranium on the earth or outer space ( meteorite ) would tend to suppress fission reactions. It is only enriched uranium 235 which supports and amplifies fission reactions. Weapons grade is, I believe 98% enriched, but that takes multiple stages of centrifuging and filtering uranium fluoride gas.

 

Haven't looked this up in a while so my numbers may be wrong.

Edited March 17, 2012 by MigL

[Janus]

To add to that, the natural ratio of U235 to U238 in a given sample of Uranium is roughly 0.7 to 99.3

[questionposter]

Could there perhaps be a large enough meteorite that the .7% enriched part is enough to cause a reaction, or is there no way it would ever work?

[swansont]

If I have a meteor of uranium, could it slam into the Earth with enough force to compress it and cause a nuclear explosion?

 

Possible? Yes. Your best odds would be if you had enough mass but the wrong geometry, e.g. a large aspect ratio, and the collision gave you a more spherical shape so you had a supercritical geometry.

 

To add to that, the natural ratio of U235 to U238 in a given sample of Uranium is roughly 0.7 to 99.3

 

That's for earth, many billions of years after the supernova that created the Uranium. U-235 has a shorter half-life. The abundance would have been much higher in the remote past, and would be different if it had a different origin.

[questionposter]

 

 

That's for earth, many billions of years after the supernova that created the Uranium. U-235 has a shorter half-life. The abundance would have been much higher in the remote past, and would be different if it had a different origin.

 

How about 12,000 years ago?

[mathematic]

How about 12,000 years ago?

12000 years is too short to make much difference. However there is geological evidence that millions of years ago there were concentrations of Uranium that acted like natural reactors.

[questionposter]

Hmm, ok.

Well this probably off topic, but I was just asking because the history channel was exploring the possibility that aliens visited Earth in the past, a strong piece of evidence they had was that it seemed as though an atomic bomb detonated in India around 12,000 years ago, and during that time, ancient texts of hieroglyphics (not written languages) also depicted some kind of large explosion that killed and injured many people. The surrounded ground was melted into a specific type of glass that is also found at nuclear bomb testing sites in the US such as in Arizona. But, I don't buy it, so I'm trying to find another explanation, but it seems as though this meteor idea is more on the improbable side.

[The Observer]

A meteor does not need to go nuclear to cause a very serious explosion.

[mathematic]

http://en.wikipedia.org/wiki/Tunguska_event

 

This a recent event like the one described (not nuclear).

[questionposter]

This... was a little different. When an atomic bomb explodes, it melts the local ground into a distinct glass. This same type of glass along with higher-than-normal radiation was found at the site in India covering a large area.

 

Also, how long does it take for exposure from natural uranium to cause tumors? Because the channel also said that there were ancient depictions of people dying from what appears exactly like radiation poisoning in people who were transporting the Ark. In the depictions it seemed rather instantaneous, but it would make more sense if people kept coming to it and getting exposure, and then after like the 20th exposure they finally noticed a bunch of tumors, but I don't know if natural uranium is that radioactive. Are there naturally occurring materials on Earth that could cause radiation poisoning quite rapidly?

Edited March 20, 2012 by questionposter

[swansont]

Natural Uranium is mostly U-238, with a 4.5 billion year half-life. So no, it's not all that radioactive. Further, it's an alpha emitter, which isn't really dangerous unless ingested/inhaled.