Tuesday, December 2, 2008


Hey, I'm Will. Thank you for participating in this program, it is very kind of you. I'm interested in doing some type of engineering and I'm interested in physics because of that. Do you think the machine your making could produce black holes and potentially destroy the world...a doomsday machine?

Hi Will,

No, I do not believe we have anything to worry about. This is an interesting question that has come up in the (sensationalized?) news media lately regarding the LHC accelerator coming on line in Europe. The earth is bombarded every second by particles that are emitted from the sun and other sources, particles with much higher energies than what we can make in our accelerators. These particles have been bombarding the earth for billions of years -- and the earth is still here.

But, perhaps in a later post, I can go into more detail about the black hole question. It is interesting to think about and discuss...


Thanks for clearing that up. I did not know about all those other particles hitting the earth. It was just something I had seen on the news and thought you would be the perfect person to ask. If it ever did produce black holes, what would they do and how big would they be?

Thanks again, Will

Hi Will,

First of all, let me point out that while Einstein's theory of General Relativity predicts that Black Holes can exist, and while there are several very good pieces of evidence that specific Black Holes do exist (like at the center of our galaxy), there has never been an absolute observation that says "this IS a Black Hole." (However, I personally think that the evidence for a Black Hole at the center of our galaxy is very convincing!)

Having said that, let me point out also that the way space and time behave in the vicinity of extremely massive objects, like stars and galaxies, does not necessarily mean that space and time behave exactly that way at very very small scales (like near "point particles" such as electrons and quarks). We call electrons "point particles" because, to our knowledge, they don't appear to have any real size. But to be honest, maybe we just haven't learned how to look at that small a scale yet.

The reason I bring this up is because the Black Holes that would be predicted to be created at, say, the LHC would be extremely small. Extremely small. There is a formula (which, again, we don't know if it is truly applicable at very small scales) for the size of a Black Hole. The formula is

where in the formula, R is the radius of the Black Hole, M is the mass inside, G is Newton's gravitational constant, and c is the speed of light.

So, I'll ask you to do the calculation -- if the LHC collides two protons, each with 7 TeV of energy, and all of that energy is turned into mass, and that mass just sits there as a Black Hole, what would its radius be?

Here's a hint: Mc^2 for our particle will have a value of 14 TeV; 1 TeV of energy = 1 x 10^12 eV; and, 1 eV = 1.6 x 10^-19 Joules.

Note that the "radius" of a proton is about 10^-15 m, and the mass of this particle that would be created in the LHC is about 14,000 times heavier than a single proton.

Let me know what answer you get!
-Mike Syphers

R= 3.69 x 10^-48

WOW, that is small, since 10^50 is statistically impossible.....yeah there is nothing to worry about. Thanks for showing me that, i love numbers they really help show the magnitude, or lack there of, of the "black holes". Thanks again, Will.

1 comment:

SyPhy said...

I got 3.69 x 10^-50 m; maybe Will was using cm...

Always specify your units! ;=)