As we enter the 21st century, what scientists have long known and what science teachers have tried hard to convey to us ordinary folk may finally be getting through — matter and energy are always changing, yet it's all still there.  

Burn gasoline in most cars and what you get is a few miles of transportation and a few pounds of carbon dioxide and other pollutants in the atmosphere. Burn most fuels to make electricity and half the energy content goes to waste. Where energy is involved, most changes are downhill, converting high-grade sources to low-grade ones, or to waste.

Life is an exception, if only locally and temporarily. New insights into one of life's most basic and essential mechanisms, the ribosome that uses genetic information to build working proteins, reveal how these cellular organelles burn energy to renew and sustain organisms that can temporarily reverse the entropic slide.

Granted, some forms of matter aren't eager to change, but that's not always good news. If the stuff happens to be as toxic as mercury, our long-gone ancestors may have left us problems — like intractable levels of mercury in San Francisco Bay that trace back to the Gold Rush.

Other kinds of matter, like the actinide element neptunium, are born changing but go about it slowly — it takes 2.14 million years for half a lump of relatively stable neptunium-237 to change into the first of a series of other radioactive elements. Dealing with neptunium's reluctance to go away is a challenge in converting to relatively clean, efficient nuclear power.

On the nanoscale, surprising changes can happen when a single electron is added to a molecule: a change in the molecule's shape can lower its energy levels and change its electronic properties from an insulator to a metal or even to a superconductor, and back again. Controlling such changes will be vital to the new century's most promising technologies.  

Not even the vast universe stands still. Only 5 percent of what it contains can be confidently explained using the laws of thermodynamics and E=mc²; another 25 percent is probably subject to the same rules, if we only knew what dark matter is. But a good 70 percent of the universe plays by rules we haven't been able to figure out yet. And in the long run, dark energy will reduce the sparkling network of galaxies, and all the life forms they doubtless contain, to cold cinders in the void.  

Depending on the time scale, change can be good or bad. Either way, it's inevitable. All the stories in this issue of Science@Berkeley Lab address change. If you have comments or questions about any of them, just drop us an email.

— Paul Preuss, Editor, Science@Berkeley Lab