Sea level exists as a concept for us. No measurement can define a “global” sea level. Such a thing does not exist. In reality it can only be what we define it to be at a given time. Read more
Today is the shortest day of the year in the northern hemisphere, but the longest day in the southern hemisphere. Read more
The hottest lights on the market today are cool light-emitting diodes, or LEDs. Read more
In 1898, Friedrich Loeffler and Paul Frosch discovered that the cause of foot-and-mouth disease in livestock was an infectious particle smaller than any bacteria. This was the first clue to the nature of viruses. Read more
Ozone is a devious chemical. High in the sky it protects us from UV light, while low in the atmosphere it is a pollutant and a health hazard. Read more
‘Liquid crystal” ought to be an oxymoron, but technology has rendered it sensible instead. A crystal is by definition a solid with a repeating, orderly, three-dimensional l attice. Read more
Sunlight is the primary illuminator. Its spectrum is a familiar rainbow with maximum emittance in a color that most of us would call yellow-green — light of wavelength around 550 nanometers. Read more
Aristotle famously claimed that nature abhors a vacuum. True, air does rush into the space from which air has been evacuated, but not because nature has feelings of any kind about the vacuum. Read more
Where is ET? After nearly 50 years of searching for intelligent signals from space, astronomers have yet to receive a single verifiable signal of intelligent origin. Read more
Water vapor is the gaseous form of water that exists in the atmosphere along with nitrogen, oxygen and other minor gases such as argon and carbon dioxide. Read more
Equilibrium is a state of balance of opposing actions which is central in virtually everything that happens, from basic physics to dance and the arts, economics and social ideologies. Read more
Helium is No. 2. It is the second-lightest element on the periodic table with atomic number of two. Read more
Since the development of MRI scans from the first crude machines in the 1970s, the technology has become more efficient. Read more
The Standard Model is what physicists call the current theory of fundamental particles and their interactions. Read more
Feeling tired today? Most of us grow more weary as the day goes on and as the years pass. We say we are out of energy or getting low on energy, which is a fact. Read more
What is it that gives numbers their power? Read more
Clouds come in all shapes and sizes, but they are usually flat on the bottom. Read more
The aurora borealis, or northern lights, is a common sight at north polar latitudes. The name aurora borealis comes from Latin and Greek. Read more
Outside the window, 7 miles up, the wings of the jet airliner slice through the invisible air that seems magically to keep it aloft. It reminds me that we are immersed in Earth’s invisible atmosphere all of the time. Read more
The names of the 12 months that make up our Western calendar are so familiar that we do not think much about where they came from. Read more
All paint inside a can is black until the can is opened. Strange as it might seem, it is true. What we see as color is a matter of perception, intrinsic properties of an object and the light that illuminates it. Read more
83