Expert: Steve Nelson - 4/19/2009

Question
QUESTION: Steve,
As I understand, brane theory includes an explanation for the big bang and "time" before.  If this theory continues to hold up under further scrutiny, will scientists be forced to consider that time was not created at the big band, must be more constant than anything created from the big bang, including light?  Will they have to look for other explanations for observed phenomena, such as that gravity can not only affect light's path, but also its velocity?
Thanks,
Paul

ANSWER: There are many theories which are currently untestable which will lead us to surprises in science.  The concepts you mention are a little malformed here, what do you mean that time is constant?  Something being constant means that it doesn't vary with time, so what are you measuring time against?  Gravity affects light's energy, but not its local velocity.

---------- FOLLOW-UP ----------

QUESTION: Steve,
Thanks for taking your time to answer a curious amateur.

I said "more" constant because I realize there are problems with measuring time, especially before or outside our universe.  Since we measure time in terms of mass and space (and I'm guessing that this is essentially true even for a cesium clock), and since mass and space were created from the big bang, then there is no way for us to measure time in that larger context.

But I guess that I'm suggesting that just because we can't measure it, doesn't mean that it might not be "unchanging" or "constant" in an informal sense, and at any rate beyond being affected by anything within our universe.

Yet I understand that current theory says that time is affected by velocity and gravity.
Might we find that it is more accurate to say that our (perhaps primitive) measurements of time are affected by such?

And it was my thinking along these lines that made me wonder if it's possible that even one of science's most basic premises, the constancy of the speed of light, could come into question if it's found that we have to accept that there was time before the big bang.

Thanks,
Paul  

Answer
A cesium clock measures time by the oscillation of quantum states of a cesium atom interacting with microwaves.  Our measurements of time are of course affected by the velocity of the measurement device and the gravitational potential that device is in.  Since scientific theories do not yet really extend to "time before the big bang," any theory that does so would of course have to adjust our current understanding of physics, but it's not necessary that a theory we don't even have yet would adjust the constancy of the speed of light.  There's no reason at all to believe that so far.  Until a really good theory suggests an actual reason for doing that or an experimental measurement suggests that the speed of light is changing now or has in the past, we'll stick with the foundation of special relativity being constant.  It's a direct result of Maxwell's equations, which are extremely well supported.