Monthly Archives: April 2013

Happy Earth Day!

Elsa asks: Is the Earth alive?

That kind of depends upon what you mean by “alive”!

Our planet is not itself an organism like a plant or an animal. But it had a beginning (about 4..5 billion years ago by our best estimate), and since then it has been active and changing, both inside and on the surface. Earth’s core generates its own heat, and the motion of the boiling rock in the mantle (the middle layer of the Earth) is what causes the continents to shift and move across the surface of the planet. Landmasses rise above the ocean and sink again; mountain ranges are thrust towards the sky and worn slowly down by the weathering effects of wind and water. Glaciers advance and retreat, and the balance of gases in the atmosphere responds to the changes in plant and animal life. Planet Earth is a complex and dynamic system that changes over time, which certainly sounds more like life than otherwise.

One characteristic of living things is that they reproduce. What would you call it if we sent a colony of humans with Earth plants, animals, fungi, and bacteria to other worlds, to grow and live like we do on Earth? There will be such a colony on Mars within a few decades at most; more distant worlds will be harder to reach, but consider: only seventy years ago, most respected scientists believed it was impossible to send people to the moon. They were not only wrong, they themselves lived to see it happen. “Hard to reach” only makes humans jump higher. When Earth organisms have spread to other planets, is that not a kind of reproduction for our own planet Earth?

Someday there will be an end for Earth. In about 5 billion years, the Sun will grow into a red giant star and swallow up the inner planets (including Earth). So you could say that Earth has a lifespan, like other living things. That brings us to the reason I wanted to answer Elsa’s question on Earth Day.

Some people say that we are destroying our planet with the pollution from our factories, vehicles, and power plants. This is not really true. We can pollute the Earth so badly that it will become toxic and unable to sustain human life. That would be the end of us humans. But it would not be the end of Earth – some form of life would survive, just like it always has. When we care for the Earth, we are caring for ourselves first!

The first Earth Day was on April 22, 1970; today is the 44th Earth Day! Since 1970, we have been celebrating Earth as something that we should respect and treat with care. As a result, our air is cleaner than it was 44 years ago. We have passed laws that make individuals and corporations more responsible than before. There is still much to be done; many people still do not understand that keeping the environment healthy and clean is more than just the right thing to do: it is a matter of our own survival.

We can make a difference every day, not only once a year. By conserving resources, recycling, and always trying to find ways to work smarter and cleaner, we can help return our Planet Earth to the beautiful place it was before we started to change it. Future generations will thank us.

Happy Earth Day!

How Does Our Sense Of Smell Work?

Andrés asks: Why can I see things far away, but only smell things up close; and why does the smell get stronger the closer I am to whatever I am smelling?

Good question! The reason you can see anything at all is because your eyes sense the light reflected off the objects in the world around you. Since light travels at about 300 000 kilometers per second, and keeps going pretty much forever (which is why we can see distant stars and galaxies), you can see everything clearly as far as the horizon (usually about five kilometers away). The optical nerves at the back of your eyeballs send the signals to your brain, which is where the senses are turned into perceptions. The important thing here is that there is no actual contact between your eyes and the objects you see; you are only perceiving reflected light.

Your sense of smell is very different. The nose is not really an organ like the eye; it is more like an eyelid – a protective covering for the organ inside. Behind your nose is a space called the nasal cavity, through which the air passes when you breathe. The top of this space is directly beneath your brain, only separated from the brain by a very thin slab of bone. The nerves from the olfactory (or “smelling”) part of the brain go right through this thin bone and stick out into the nasal cavity. If something comes in contact with one of those nerves, you are sensing it directly – actually touching it with your brain! But how can something get into your nasal cavity in the first place?

If you have ever had to dust a shelf, you already know most of the answer. House dust is made almost completely of skin cells that we shed every day. Almost everything in the world “sheds” molecules – the smallest pieces of anything – all the time. The reason you can smell a flower is because tiny pieces of the flower have come loose and floated through the air and up your nose. Inside your nasal cavity, the flower molecules touch your olfactory nerves, and your brain gets a signal.

But why does a flower smell stronger than a piece of wood, or a brick? This is because some objects, like flowers, “shed” molecules more easily than others. Things like bricks and pieces of wood are stuck together more tightly – their molecules do not come apart very much, so not many of them get into your nasal cavity where you can smell them. Try to smell a clean dinner plate. It is very hard, smooth, and dense, and has no smell at all. Not enough molecules are getting up your nose for you to be able to smell it. Some things are made to come apart in great clouds of molecules – like a skunk’s spray. You can smell a skunk from a long way off, because the skunk releases a huge number of molecules (which also have a very unique smell of their own).

Why does a skunk smell differently then a flower? It is not just the intensity of the smell; the scent itself is different. This is because, in different kinds of matter, the molecules have different shapes. You and I cannot see the difference – individual molecules are too small for us to see – but the different shapes of the molecules make our olfactory nerves send different signals to our brains. And that is how the sense of smell works!

Did Scientists Pickle Leonardo da Vinci's Brain?

Adrian asks: “Did scientists put Leonardo da Vinci’s brain in a jar like they did with Albert Einstein?”
Aha – you know about the strange fate of Einstein’s brain! In case some of our other readers haven’t heard, Albert Einstein died in 1955 in Princeton, New Jersey, where he had worked for many years at the Institute for Advanced Study. Immediately afterwards, a scientist at the University of Pennsylvania named Thomas Harvey removed Einstein’s brain from his body, preserved it with formaldehyde, dissected it into small cubes, and finally encased the cubes in surgical gel. Twenty-three years later, in 1978, a reporter discovered that Thomas Harvey still had Einstein’s brain, now stored in two glass jars full of alcohol.
The reason for all this pickling was so that scientists could examine the brain of such a wonderful and unique person, and maybe discover if there was anything special about the brain that could explain Einstein’s genius. The results are uncertain. There seem to be some things about Einstein’s brain that are a bit unusual, but it is impossible to tell whether those details have anything to do with his intelligence or personality.

So, what about Leonardo da Vinci? He was definitely one of the greatest geniuses in history; it would surely be the dream of any scientist to have a chance at examining da Vinci’s brain – perhaps even comparing it to Einstein’s! Unfortunately, that will never be possible. Leonardo da Vinci died in 1519, long before formaldehyde or surgical gel were discovered. Of course, if you have read my article on pickling, you know that people have been preserving food in salt water or vinegar for thousands of years. But that kind of pickling would probably not have kept da Vinci’s brain in good condition long enough for us to be able to learn anything from it, even if anyone had thought of preserving it – which no one did. Leonardo da Vinci was buried (in one piece) in the chapel of St. Hubert, in the Château d’Amboise, a castle in the Loire region of France. The house where he spent his final years is called Clos Lucé. It is now a Leonardo da Vinci museum!

Even though we never got to pickle Leonardo da Vinci’s brain, you can “pick his brain” by reading his notes (although you might need a mirror!), admiring his artworks, or studying his mechanical inventions. If you are really lucky, you might even get to visit the museum at Clos Lucé someday!