Why Time?

I've spent a good deal of time thinking about time.  It is a mystery.  We know it passes, the more quickly it seems as we get older.  Since Einstein, we know it is part of spacetime, baked into the fabric of the universe.  But that simply deepens the mysteries.  Why can we travel in all directions in space but only one in time?  And how can it be that there is no absolute time the same everywhere?  The "now" that  I see all around me is punctured during the day by photons from the sun that show me how that looked nine minutes ago and at night by stars showing me how they existed many thousands of years ago?  When we see those stars, we are looking into the past. Our experience of the "now" of those stars is likewise thousand of years in our future.

 

So time varies by distance in space.  The speed of light -- 186,000 miles per second -- connects these.  Contemplation of the speed of light leads to pondering how light can possibly have a speed.  Objects with mass, when not at rest, have speed.  (Actually, nothing is ever at rest except relatively.)  As an object with mass increases speed, time runs slower as it appears to observers not so moving.  Relative motion, in effect, eats relative time; the quicker something moves, the less time remains that seems to pass for the object moving relative to the observer at rest where "normal" time passes.  Mass-less particles, such as photons, do not experience time.  Mass-less particles are everywhere they will ever be at the same moment and are, in this sense, eternal.  Only objects with mass -- including us -- experience light as traveling in time.  A photon that left Proxima Centauri, traveled 4.25 years and just reached our eyes here on earth, took that photon no time at all. 

 

By capturing some of the particles spewing from the Big Bang and giving them mass, the Higgs Boson may in effect have also created time.  But as there is no universal and simultaneous "now," how can we think about time. As noted, under Einsteinian relativity, time is the fourth dimension and relative to location and motion in the other three.  Yet clearly there is also "now."  We live in it.  Is there not a single "now" that exists for all the photons that fill the universe in their one timeless, eternal moment?  Does that create a universal framework of now?  Perhaps each and every particle of matter exists in its own "now" tied to every other such moment within the crystalline universal now established by light?  Light seems to have a speed because it ties together the universe of separate, individual "nows."   Perhaps mass is simply the way everything is kept from happening at once?  Mass separates us from eternity, immersing us in spacetime where our consciousness has space and time to manifest.  Perhaps time exists to provide a way for the universe to experience itself.

Gravity, Mass and Time

Recently finished physicist Kip Thorne's The Science of Interstellar about his work to make the movie as scientifically grounded as possible. While written for the interested layperson, some of it was hard to follow. But it provided a lot of food for ruminating about the deep connections between gravity, mass, time and the speed of light.

At the speed of light, time stops. Anything with mass that reached the speed of light also achieves infinite mass. (This is one good reason to believe that nothing with mass can go that fast. Anything of infinite mass would need a great deal of thrust to keep going, indeed, an infinite amount.) Photons have no mass and thus they gain no mass. Anything – some ghost without a machine – traveling with that photon at 186,000 MPS would also be timeless and thus everywhere that photon will ever be all at once.

Time also stops with an infinite mass that is not going anywhere, at a black hole. Gravity slows time. At the event horizon of a black hole, spacetime is so warped that nothing can escape upwards – not time, not space, not matter, not light – but falls down into the black hole until it reaches the singularity at the “bottom.” While the black hole may have a certain mass – the mass left over from the collapse of the star that formed it – the singularity itself has the equivalent of infinite mass. Anyone watching a friend drop into a black hole would never see him or her actually fall all the way past the event horizon. From the outside, the friend would be seen moving ever slower. At some point, a second to the falling friend might be, for example, a billion years to the outside observer.

Not just black holes slow time. Anything with mass does, including earth. Einstein's theory of relativity predicts this. And indeed, time on the GPS satellites (orbiting over 16 thousand miles up) run some 45,900 nano seconds slower per day than clocks on earth. The stronger the gravity, the slower time goes compared to places of less gravity.

Mass warps spacetime and achieves that effect through gravity. We don't understand where gravity comes from and it does not fit into the Standard Theory of quantum physics. Relativity seems to describe the effects of gravity but neither meshes with the Standard Theory nor explains from whence gravity comes. String theory has been the Standard Model's framework to incorporate relativity as quantum gravity. To do so, it would require extra dimensions beyond the four we observe (three space and time). But recent experiments have found no supporting evidence for the simplest forms of such theories.

It may be that mass, gravity, and time are just givens. Gravity is something that slows time. At the speed of light, time stops. Our experience of time – our consciousness – seems related to the speed of light. Mass keeps us from exceeding the speed of light. Random?