Do you have the sense that life is speeding up the older you get? If so, you're not alone. Can there be a reason for this perception? I've discovered three scientific theories that shine a little light on this mysterious experience.

The first is a phenomenon called "telescopy." Telescopy is simply the underestimation of time. It's as though you're looking through a telescope where the details of what you see give you the impression that an object in the distance is much closer than it actually is. Because of telescopy, our brains recall distant events as if they occurred only yesterday.

For example, at 67, I can't believe 43 years have passed since the Beatles broke up. Every time I see Sir Paul McCartney on TV performing old Beatles tunes like "Hey Jude," I'm amazed. Why? To me it seems as if 1970 was not that long ago.

Similarly, a 50-year-old woman I know said after the recent Boston Marathon bombing that it was hard to believe 9/11 happened almost 12 years ago. "Wow! Time really flies," she said.

We are inclined, it seems, to perceive events more recently than they actually occurred. Hence we say wistfully, "Why, it seems like only yesterday."

The second reason time seems to be going faster as you get older is called the reminiscence effect. You can think of it as a series of memory bumps in your life. Emotionally charged events—your first kiss, going to college, getting married, having your children, having a grandchild or losing someone dear—are recorded in more vivid detail than what we might call regular events, which just pass by in a blur.

As time marches on, life may become more routine, more mundane. Hence, you create fewer memory bumps, which give you the feeling that time is moving very quickly.

Neither telescopy nor the reminiscence effect provide all the answers to understanding why life goes faster as you get older, and perhaps more importantly, how you can slow time down. That falls to the third theory, which I believe is the most astute explanation of why time flies. Interestingly, this third theory is also the best-kept secret in anti-aging medicine.

The third theory is the aging of your brain's biological clock. Named the SCN (for suprachiasmatic nucleus), it's found in a special gland called the hypothalamus located behind the middle of your forehead. The hypothalamus is also known as your brain's brain and controls the release of a number of important, youth-maintaining hormones.

Moreover, this little spot (about the size of a pencil point) sends signals to each and every one of your 30 trillion cells, telling them either that all is well, or conversely, that you're stressed. Stress has an aging effect throughout your body, including your genes.

These signals influence the length of your telomeres at the end of your chromosomes. Telomeres are the caps of your DNA and are exquisitely sensitive to stress. Think of them as like the tips of a shoelace. As the lace ages, it becomes frayed, damaged and shortened. For you, stress equals shorter telomeres and accelerated aging. Conversely, less stress equals increased telomere size and a longer life.

As we have seen, as your inner time meter slows down, the outside world seems to speed up. This feeling can make you age too fast. But I'm happy to report that there is good news. There are three ways you can change time perception, affect your biological aging clock and lengthen your telomeres.