Here’s a question for the start of summer: why does exposure to the sun darken our skin but lighten our hair?
First let’s take a look at our skin. Human skin is the body’s largest organ, and acts as a barrier between our inner organs and the outside world. It’s made up of essentially two parts the epidermis and the dermis. The epidermis is the outer section and is comprised of a layer of living cells, topped by a layer of dead cells. The dead cells are the skin we see.
Even though the upper epidermis is just a lot of dead cells, it contains keratin, a tough protein that also makes up our hair and fingernails, Keratin is thicker on the bottoms of our feet and the palms of our hands for added protection against abrasions and other intrusions from the outside world.
Inside the dermis is where all the skin’s functioning equipment is located, These include nerves, sweat glands, hair follicles, blood vessels and special cells called melanocytes, which produce melanin, the material responsible for skin pigmentation, hair and eye color. Most humans have about the same amount of melanocytes, some just produce more melanin than others. Albinos, however, produce no melanin at all.
When our skin gets exposed to sunlight (particularly ultraviolet rays) melanocytes begin producing melanin to help protect the dermis, and keep the skin cells from getting fried. The melanin acts as an absorbing agent. So over time, as exposure to the sun continues, more melanin is produced and subsequently the skin becomes darker.
The hair is a different story. Hair color is also determined by melanin, but hair cells are dead, so sunlight doesn’t initiate melanin production but rather begins to break down the melanin already in the hair, and the hair’s color begins to fade or lighten.
I thought this last part was strange. The pituitary gland is tied to your optic nerve and is sensitive to sunlight. When light enters your eyes, it triggers your pituitary gland to produce a melanocyte-stimulating hormone (MSH) that activates your melanocytes to produce melanin. This means that wearing sunglasses can actually cause sunburn.
UK doctors have warned mobile phone users of the risks associated with mobile phone usage during thunderstorms. Metal found in mobile phones is able to send lightening currents directly into your body-possibly creating lots of damage!
The National Museum of American History is in the planning stages of building an exhibition displaying numerous Hurricane Katrina artifacts. The exhibit will be on display after the museum reopens in 2008.
Living in Minneapolis, I often ride my bike for exercise around the city lakes. The other day, while trying to get a ride in between rain showers, I was presented with a stunning rainbow. Actually, only a small portion of the arc was visible when I first saw it at Lake Harriet, but by the time I reached the west side of Lake Calhoun it had grown into a full blown double arced rainbow.
I stopped to admire it and regretted not having my camera with me because it was truly one of the best rainbows I had witnessed in a long time. A kid next to me, snapping a picture of it with his cell phone, wondered out loud, “How far away do you think that rainbow is?”
It was a good question and made me want to learn more about the atmospheric phenomenon.
Basically, rainbows are the result of sunlight being once reflected and twice refracted by raindrops. Certain conditions are required. First and foremost, the viewer needs to be located between the sun and rain clouds. A ray of sunlight enters an individual drop of water and is refracted (bent) as it enters, then reflected from the back of the drop, and refracted again as it exits the drop. The refractions cause the white sunlight to divide into separate colors. Each color refracts in slightly different amounts, red the least, and violet the most. A particular raindrop will reflect red light because it is positioned at just the right angle from your eye (42°). This is known as the “rainbow ray”. Another droplet located at a slightly different position will reflect blue light to your eye. Now multiply this by the innumerable suspended water droplets that make up a rain cloud, and you have a rainbow.
The main colors in a primary rainbow will have red at the top followed by orange, yellow, green, blue, indigo, and violet. An easy way to remember the order is to note that the first letter of each color spells out the name ROY G. BIV.
The rainbow I witnessed had a second, fainter rainbow just above the first. This is the result of some light being reflected twice, and at a higher angle. The colors in a secondary arc are reversed with red on the bottom and violet on top.
The inside of a rainbow is always brighter than the sky outside the arc. This is because other rays of light are reflected from individual raindrops at angles smaller than the rainbow ray. Since this scattered light is made up of all the other incidental colors the light inside the bow is white.
So, how far away is a rainbow? I’ll let you figure that out for yourselves. The answer may surprise you.
After all the rain we've had recently, parents of toddlers in the Twin Cities area surely have two questions on their minds:
I can't help with the first question.
But the second, that's a topic for Science Buzz!
I always thought that the worms came out of the ground when it rained to avoid being drowned in their burrows. Turns out I was wrong, wrong, wrong.
A series of Straight Dope articles, by Cecil Adams, have enlightened me.
Turns out that the worms are in no danger of drowning. They can actually survive underwater for quite a long time. They are out on the sidewalk after it rains to engage in, um, "amorous activity." For the slimy details, read the Adams' column!
Of course, that's not ALL the worms are doing. They're also trying to move safely to new areas; vulnerable to drying out as they are, they can only do this aboveground at night or after a rain.
My toddler will be blown away by all this. Her explanation is that worms come out because of some altruistic notion that robins are hungry...
For more information about earthworms, check out this JourneyNorth Q&A page.
Tornado season is here for those of us living in the Midwest. Tornadoes fascinate me – they’re so incredibly powerful and stunning and scary all at once. I used to have all sorts of elaborate emergency escape plans to the basement when I was a kid, and even had a pecking order for what prized possessions I would save and how. I also remember as a kid being told that if there was the threat of a tornado to open up a window a crack before heading to the basement so that the pressure inside the house would normalize with the pressure outside generated by the tornado thus preventing the roof from being blown off. I did this all the way up until last summer – but no more.
It turns out that a majority of damage to homes is the result of wind blowing into open (or broken) windows pushing up on the roof at the same time as winds are blowing over and under them, generating a lifting force, which increases the chances of the roof being blown off. So, all this time I’ve been making my house less safe, rather than safer. Doh.
Although it is likely wishful thinking on my part to hope that a single pane of glass is going to remain intact during a tornado, especially with all the debris that will be flying around. It makes more sense to close them to keep the rain out than to save the house from tornado damage, but it feels good to do something during those times when you have no real control. Better still to just forget the windows and get to the basement. With my most prized possessions.
Global warming has been in the news a lot lately. First, 60 scientists signed a petition asking the Canadian Prime Minister to open a scientific debate on the Kyoto Treaty. (The Kyoto Treaty is an international agreement to reduce global warming by reducing industrial emissions. Some people think the treaty has too many loopholes, and even if the loopholes were closed, it would still not be effective. The US has not signed the treaty. Science Buzz has had its own Kyoto debate.)
The scientists argue:
Much of the billions of dollars earmarked for implementation of the protocol in Canada will be squandered without a proper assessment of recent developments in climate science. …
It may be many years yet before we properly understand the Earth's climate system. Nevertheless, significant advances have been made since the protocol was created, many of which are taking us away from a concern about increasing greenhouse gases. …
The new Canadian government's commitment to reducing air, land and water pollution is commendable, but allocating funds to "stopping climate change" would be irrational. We need to continue intensive research into the real causes of climate change and help our most vulnerable citizens adapt to whatever nature throws at us next.
Next, a climate researcher in Australia has looked at current climate data and found that global temperatures have been holding steady since 1998:
Two simple graphs provide needed context, and exemplify the dynamic, fluctuating nature of climate change. The first is a temperature curve for the last six million years, which shows a three-million year period when it was several degrees warmer than today, followed by a three-million year cooling trend which was accompanied by an increase in the magnitude of the pervasive, higher frequency, cold and warm climate cycles. During the last three such warm (interglacial) periods, temperatures at high latitudes were as much as 5 degrees warmer than today's. The second graph shows the average global temperature over the last eight years, which has proved to be a period of stasis.
Finally, an atmospheric scientist at the Massachusetts Institute of Technology argues that there is a vicious circle between climate scientists who find evidence of global warming; environmental activists who use those findings to advance their cause; and policy makers who respond to the activists by giving more money to… the climate scientists.
(He also claims that scientists who raise doubts about global warming and human impact on climate are sometimes shut out of the debate. Science Buzz has had it’s own discussion on disagreements within the scientific community.)
So, what to make of all of this? I think the MIT professor said it well:
[L]et's start where there is agreement. The public, press and policy makers have been repeatedly told that three claims have widespread scientific support: Global temperature has risen about a degree since the late 19th century; levels of CO2 in the atmosphere have increased by about 30% over the same period; and CO2 should contribute to future warming. These claims are true. However, what the public fails to grasp is that the claims neither constitute support for alarm nor establish man's responsibility for the small amount of warming that has occurred.
This all illustrates the dynamic interaction between science and politics. Science is about facts. Politics is about opinion – what should we do in the fact of those facts? But the distinction is not always clear. Science influences political debate; and political decisions influence what science gets support. The best thing to do is to keep an open mind, remembering that most people have some sort of agenda, and that new information is coming out all the time.
(The Science Museum of Minnesota did an exhibit on global warming. You can find the website here.)
Have you ever wondered how to rate a snowstorm? Meteorologists classify earthquakes, tornadoes, and hurricanes…so why not snowstorms?! This past January, the American Meteorological Society released a new scale ranking snowstorm severity. Criteria include snowfall amount, size of region blanketed, and lastly the population of the affected area.
Scientists focused their research on thirteen states in the Northeast. Region selection was based on frequency of snowstorms. They classified snowstorm severity in five levels: notable, significant, major, crippling, or extreme. So the next time we get blasted with a wintry-wonderland, keep in mind the new snowstorm classification.
Resource: How to rate a snowstorm. (2006, February 18). Science News, 169, 7
Overnight, hurricane Wilma became a Category 5 storm with sustained 175-mile-per-hour winds and the lowest recorded barometric pressure of any Atlantic hurricane. Meteorologists expect it to weaken over the next few days, although it could dump huge amounts of rain on Bermuda, the Cayman Islands, and Cuba.
The current forecast has Wilma dropping to a Category 3 storm before it makes landfall somewhere in southwestern Florida over the weekend. (Florida has been hit by six—count 'em! Six!—hurricanes since August 2004, and many people are still in the process of rebuilding from the last storm.) Wilma is the third Category 5 hurricane this year (after Katrina and Rita). The National Hurricane Center doesn't know if that's a record because they don't track the number of Category 5 storms in a season. Wilma does tie two other records, though—the most hurricanes in a season: 12; and the most named storms in a season: 21. And Wilma is the last name on the National Hurricane Center's list of names for 2005 storms. The hurricane season doesn't end until November 30; if any other tropical storms or hurricanes develop this year, they'll be named using letters from the Greek alphabet, starting with Alpha. (If that happens, it would be the first time since we started naming storms in 1953.)