Recall your knowledge
. Two thousand years ago, new things were occuring. But they were not occuring on the scale
that they were one thousand years later. And another 500 years later, and things were happening even faster. And so on.
Consider all that has happened in the last 50 years. Television changed the way that information and news was delivered to people - instantenously. Computers allowed faster information processing, faster computation, more efficient data storage, and data retrieval. The internet offered more data at the average person's fingertips, and more varied communication. And that's just a small piece - think about medicine, and curing diseases and understanding the body more completely. Heck, they've even sequenced the entirety of human DNA.
In comparison to before then, the last 50 years have yielded an amazing amount of change - much of it unprecendented in human history. And it's all occured at a rate much higher than before - compare the major changes in the lifetime of a person living in 1000 BCE, or 1000 CE to someone today. Back then, the world might change very little in one lifetime. Today, there have been multiple discoveries and inventions that have had huge effects on people and society.
So it would appear that not only are there changes that haven't ever occured before, but that the rate of change has also increased, to a rate much faster than it's ever been. There are no signs that this rate of change is slowing, either. In fact, it is probably still continuing to increase. The next 50 years are likely to contain even more changes than the previous 50.
For what might happen if this rate never slows, read about the technology singularity.