life as a physicist : time-reversal

today it rained so heavily, that i've no other choice but to stay at home. i don't have much of the luxury staying, relaxing on sundays this year..work at office demand my constant attention every now and then.. but then again, it's nice to stay and tell you a story today..

i want to tell you sth about physics that really revolutionise the world as you and i see today.. please be warned that if the word "physics" scares you away, i still want to challenge you to stay focus and listen to what i want to say. so here comes...

the subtopic is "time reversal". yes.. you heard me right: time going backward! now, in our days of reckoning, we've never encountered this. some of us have and had wished that we go back to the past and mend some of the mistakes that could have had make a difference in our life today. some, being stubborn and adamant as they always had, swore to their allegiance that even if they've given chances like this once in a lifetime, they'll never resort to changing an iota of their paths (some even add that they'll do the same things again like they've done before). i want to digress a little, and pardon my boldness, what will you want to change in the past, if such oppurtunity given to you? you may or may not want to answer me now, but i'll leave it to your ponder--to me, if i could go back and change my path, i'd change my attitude towards other, especially those who i've been careless and quarrel with. i guess back then i was too "kebudak-budakan" (childish is too mild for my then attitude) to not to appreciate the gap between us. if you think you're one of these people that i've been neglecting at, my sincere apologies.

okay, back to track..where were we? ah yes! the backward time..in quantum physics, we've several operators( a thing that act on our tiny systems) that can be sub-group into two : linear, and anti-linear. when we say linear operator, we mean if it acted on a system it'll yield a linear result. i.e. observables that can be flipped/mirrored but nothing changed. for instance, when we want to measure a rope's length, it doesn't matter which end we start with, both ends give same number. an anti-linear operator like time reversal, is none like this. it's not possible to construct its analogy from our daily encounters, but to weave our imaginations alone on how it should "look like". enough to say that time goes back to the past, and let you imagine..

while you're imagining this, let me take you futher into the topic. i've cheated on you just now by saying that it's not possible to reverse time. it can be done, but only with external forces (man-made) acting on our system. and hence you've heard of "colliders", "particle detectors" etc. so i was right partially because it cannot be done by forces of nature alone. now if you're an astute reader, this is the point you'll raise your hand, and yell at me WE SEE ANTI PARTICLES FROM THESE COLLIDERS!!.. yes! you're right..an anti-particle is the result of this backward time operator acting on our particle (system). a more mature scientist among you, will showers all of us with details : antiparticles are exactly the mirror image of their respective particles, unchanging mass of course. it is said that for every particle that u can name on this Earth, there's its corresponding antiparticle that we cannot see or feel, but the particle itself can see and feel it. Spooky isn't it? Say we take electron as our particle (this is observable everyday..the reason why you've lightning, why you can read me on your petite LCDs, etc), and we call its anti-particle positron (you may have had heard of this somewhat somehow. it's quite a popular particle to talk about). they've same mass, and spin states. but they've opposite charges, and of course time direction.

a more profound effect that these anti particles possessed is that they've negative energy, and hence we cannot see them in nature. to be able to peek through this little particle, we've got to supply energy to them so that they gain more energy, above their energy thresholds, and made themselves visible to us. in a way, you can say that they're very shy, and we've to coerce them to let us take their pictures. so now, have you got their pictures?

on a big scale this very simple idea of reversing time and hence producing anti-particles brought forward many both unfold and fold mysteries. our universe ingredients, black holes, structure of our Sun, some galaxies from afar and so forth. many, if not all, had revolutionise our understanding and appreciations on how complexity of our universe being masked by its beauty. if we concentrate on smaller industries, we find that production of antiparticles, manipulating them yield so much more new particles (and anti-particles of course), some even more exotic that keep us busy adding new rules and theorems into our "particles and antiparticles book keeping". in physics dept at auckland uni, i've a friend who works with "time-reversal of photons" and we often chat and visit each other labs for social activity. i shall tell you about this when he's gotten better results and came to tell me about it, as for now his annoyance is only he couldn't get it working. it's very exciting, especially when they tell you what they've tweaked and the results!! as for my part of research, i deal with much larger length than his, and yet still can fascinate each other! what my research program is, i'm tempted to let you know sooner, but not in this article. i hope you find solace and peace in between until i write again.

so now you see the world slightly different from what it is few minutes ago. that antiparticles travel backward in time. perhaps it's not too much to allude you that you may have your "antiparticle" somewhere, and his/her future is what you called "your past". if your past is tarnished with mistakes that could be avoidable, it may be a good start now to fix it and work for a better future. an easy anology of this is..if we're too laid-back in the past, we should've gotten rid of it by any minute now and work for better future! we shall not want our "antiparticle" to curse us at our backs, yelling "what a wasted FUTURE i've!!!". i can actually hear my spooky "anti particle" throw nasty words at me for having many friends and family uncared for, and now she is left alone with no one to care for. i shall make haste and start working on broken bridge of communication. if you, dear readers, had already resolute aim in minds to amend your mistakes in the past, then this could be the start of it! and for those, whose adamant enough, ponder again..it's never too late to change, how little even, path of our lives.