Re: What is the Planck energy and how does it relate to the warping of spacetim

Hello Paul,

The fundamental constants of physics can be put together in various different ways to yield numbers with partciular dimensions. Here's an example: we think that the speed of light is a universal constant. Think of another universal constant, say the "size" of a proton (I put size in quotes since it's a slippery concept on the elementary particle level). If you take the size (given in meters) and divide by the speed of light (in meters/second), then you have a time (in seconds), which is how long it takes light to cross a distance the size of a photon.

You can make other combinations of other universal constants to get other numbers. If the constants c (speed of light), h ("Planck's constant"), and G (the graviational constant) are used, you can combine them in various ways, sometimes squaring or cubing one or more of them, to get numbers including "Planck length", "Planck time", and "Planck energy". Here is a webpage that gives a little more detail. For reference, the Planck energy is 10^28 electron volts, or about 10^9 Joules ("^" means "raised to the power", so 10^9=1000000000). On the everyday scale this is a respectable amount of energy (it's roughly the amount of energy on my electric bill last month), but on the quantum level, the Planck energy is really enormous.

Ok, what does this have to do with spacetime? Here's what's happening: there are four fundamental forces in nature, the weak, electromagentic, strong nuclear, and gravitational forces. As you deal with particles at higher and higher energies, these forces start to "unify", that is, they act like different aspects of the same force. The lowest-energy unification is for the weak and electromagnetic forces, at an energy of about 10^11 electron volts. Gravity is the last force to unify with the others, and this unification is supposed to happen at the Planck energy. I say "supposed to" because physicists are still trying to figure out the details of how this works.

Because the Planck energy is the energy at which gravity unifies with the other forces, and gravity is what's involved in warping spacetime, this may have been what you read about. Actually, all mass warps spacetime, but to get to the point where it's noticeable, you need to go to very high densities, which are equivalent to very high energies.

I hope this answers your question. If you are interested in more detail, here is an article about superstrings which might be of interest.

Pauline