would it take to blow up the earth?
The Earth's Mass
mass of Earth = 5.9742 × 1024 kilograms (pasted from Google)
So, half of that is 3 x 1024 kilograms
To accelerate that much mass to 25,000 miles per hour. Google Search (kilograms per mile) ... 1 mile = 1.609344 kilometers x 25,000 = 40,000 kilometers per hour ... x 1000 (to get meters) / 3600 (to get per second) = 11,111 meters per second.
So, energy equals one half times mass times velocity squared and the "second squared" remains just "one".
... to blow up the planet.
(a joule is related to the fundamental units in that a joule is 1 kg m2 /s2) - from Google search
Now what about that Uranium?
One kilogram (about 2.2 pounds) of matter converted to energy is equivalent to ~ 9 x 1016 joules
U-235 + n ==> U-236
from Google - 1 megaelectron volt = 1.60217646 × 10-13 Joules
So, one uranium atom releases 200 x 1.60217646 × 10-13 =
Now then, 3x10-11 Joules goes into 1.8 x 1032 Joules =
1 amu ˜ 1.6605387 × 10-27 kilograms times U-235 = ~3.90 x 10-25 Kg per U-235 atom
3.90 x 10-25 Kg x 6 x 1042 =
6 x 1024 / 2.3 x 1018 =
Uranium is at 18,700 kilograms per cubic meter ... so ...
2.3 x 1018 divided by 1.87 x 104 =
About 1.23 x 1014 cubic meters, which translates into a ball about ...
4/3 pi r3 = 1.23 x 1014 or ...
6.6 x 104 meters ... or ...
134 kilometers in diameter ... or ...
84 miles in diameter
This is a lot of Uranium
How can it be kept from exploding while it is forming? Simple ...
It must not reach critical mass, that's all. Then when the total is there in place ... after having drifted into position for millions of years ... some part of it goes to critical mass and that part blows up. Of course the rest will blow up as well in a second or two because it takes the critical density to start ... not continue. A big ball at near critical density will not blow up but it will all blow ... if ... some part of it starts the whole thing going, i.e. the non-critical density portion will not "damp out" the continuing explosion all through the entire 84 mile diameter ball.
So, I guess the Exploded Planet Hypothesis could be viable by uranium fission (unless I screwed up the math ;o). I can't think of any other viable candidate.