I am an observer moving at the speed of light. Time does not exist for
me.  What happens if I apply all the mass/energy for our entire universe
to the equation e=mc2?
Say you balance it perfectly so that E=M.
We assume that "c" is not a constant for this thought experiment.
Solve for "c".  Make any other assumptions to fit this if you must.
Davetheslave. Goddoesexist.

Hi Davetheslave, 

First of all, it would appear you have a great sense of humour and an
uncontrollable imagination...lol.

In answer to your question however....

You start by saying that "I am an observer moving at the speed of
light. Time does not exist for me".

We have to clear that one up from the start I am afraid. Time would
exist for you regardless of the premise that you would be travelling
at the speed of light.

Einstein only theorised that someone travelling at the speed of light
would not be "aware" of any time passing - he didn't say that time
didn't pass.

For example, suppose you were travelling to a planet which was for the
sake of argument exactly 7 light years from earth. If you travelled
there at the speed of light it would still take you seven years to get
there. Ergo seven years would have passed for you, therefore time
would certainly exist for you.

Einsteins Special Relativity
http://www2.slac.stanford.edu/vvc/theory/relativity.html

Part Deux
*********
For the second part of your question, you say lets assume that all the
energy and mass in the universe is entered into the equation E=MC2,
and let us further assume that Energy and Mass are equal values.

You also wish to assume that light (a fundamental constant of the
universe) is not constant.

If that were the case then E=MC2 with E & M being equal could be
rewritten

C2(C Squared) = E/M. If E and M are Equal then; 

C2(C Squared) = 1

Since the only number that is equal to 1 when you multiply it by
itself is 1, the speed of light would therefore have to be 1.

The answer would therefore be c=1

An Interesting Thought
**********************

Due to your very interesting question, it set me off thinking along a
different tangent.

Lets suppose for a second that you were able to defy the laws of
physics and travel at the speed of light. You set off to a planet five
light years away to
shine a big torch. 

Whilst we are in the realms of fantasy, lets say you had a telescope
on Earth capable of seeing that far away, since the light would take
five years to get to the telescope, If you had set off to go to this
planet it would take you five years to get there. It would then take a
further five years for the light of the torch to reach earth.

If you had set off, after flashing the torch and travelled back at the
speed of light, theoretically you would be able to see yourself
flashing the torch through the telescope five years ago.

This would create the illusion that you were in two places at once. 

I hope this helps.....somehow.

Johnny Phoenix

Note to Researchers -- The original "God does exist" question is found at:

https://answers.google.com/answers/main?cmd=threadview&id=109968

c= 20+fl+oz+5%+spec/grav

Homer Simpson proved god doesn't exist through a mathematical equation
during the episode in which there is a crayon lodged in Homer's brain.

Johnny Phoenix's answer is incorrect. It takes 7 years from the point
of view of someone on the planet you are travelling to. From the point
of view of a near-light-speed traveller, it takes a much smaller
amount of time. The amount of time it takes is 7 sqrt(1-v^2/c^2)
years, where v is the velocity the traveller has with respect to his
destination, and c is the speed of light.

Pausanias, thanks for the comment but as you say in your comment you
are discussing someone travelling at NEAR light speed, whilst the
question master asked about AT light speed.

It amuses me no end when people try overcomplicating simple things. 

Q: Why is a light year called a light year?
A: Because it is the distance light travels in one year. 

Q: So if something is seven light years away, how long will it take
light to get there?
A: ermmmmmm...seven years.

Q: What would happen if someone did the same distance in six years
A: They would be travelling faster than the speed of light

Q: What would happen if someone did the same distance in eight years
A: Well by crikey, they'd be travelling slower than the speed of
light.

Therefore, my answer is correct. 

"the point of view" of the traveller is immaterial in the context of
the question.

Cheers anyhow pausanias lol.

I'm sorry Johnny, but pausanias-ga is right, as his formula suggest,
the time is subject to a dilation. It means that, inside the ship, the
speed seems to be infinite. But it's a question of point of view, an
observer, traveling at another speed, would see that person completely
immobile.
So, time spend for the traveler to reach the 7 Ly planet : 0 sec...