10 Misconceptions Debunked

Hand Sanitizer

Hand sanitizers claim to kill ~99% of bacteria. How does this work? Well, alcohol kills bacteria exponentially. For example, after x amount of time, 90% are dead. After 2x that time, 99%, 3x, 99.9%, and so on. As you can see from that math, you'll never 100% sterilize something using alcohol - at least not in a practical way. However, as far as getting germs off your hands, 99.9% is good enough. You're not looking to sterilize your hands (which is impossible), you're looking to cut down the risk of infection.

The 10% survivors in each instance aren't resistant, they're just lucky. Maybe they didn't get the full exposure to the alcohol, they had a little extra water in them, or they were in a clump. The effectiveness of a sanitizer is always dependent on the surface to which it is applied. If the alcohol can't get to the bacterium, it can't kill it. As such, human skin provides a lot of nooks and crannies in which bacteria could not be reached by the alcohol very well. This is why alcohol based hand rubs are only recommended on non-soiled hands. They aren't designed to penetrate dirt and gunk. Just like the ratio of bleach to water has to increase depending on the amount of blood (or protein) in a spill.

Also, while alcohol kills everything, it doesn't efficiently kill everything. Bacterial spores, bacteria with thick capsules, and nonenveloped viruses are fairly resistant to alcohol. For this reason, alcohol is never used as the only method when something needs to be completely sterile - we use fire, 10% bleach, formaldehyde, gamma rays, or autoclaving instead. Labs also use the aseptic technique when surfaces need to be 100% sterile. Please see the CDC take on handwashing and hand sanitizer.

Methuselah

Methuselah is the oldest known living non-colonal organism in the world. It is 4,842 years old. It can be found in the Bristlecone Pine Forest near Death Valley. However, while it is open to tourists, nowhere does it say which tree is Methuselah; it's kept anonymous for its own security. According to the Wikipedia page, " Methuselah's exact location is undisclosed as a protection against vandalism." So while unlikely that the tree above is Methuselah, it is probably very similar to this one.

In 1964, when scientists were first beginning to realize just how old these trees were, they decided to do some core sampling. A graduate student doing the samples ended up getting his drill bit stuck in one of the trees. Rather than just leave it there, he decided to cut down the tree to retrieve it. Upon inspecting the age rings of said tree, it became apparent that the tree, nicknamed Prometheus, was well over 5,000 years old. This controversial felling is featured in an episode of Radiolab, appropriately titled "Oops."

Everytime I hear someone say global warming is fake

Source

Two-thirds of the people who have ever reached 65 are alive today

Can the above statement really be true? First of all, the common statement: "more people are alive today than have ever lived" is false. According to wolfram alpha, there have been about 100 billion people ever.

There is a possibility that we are are reaching older ages with the technology available to us today, and therefore the statement might be "more" true. I wouldn't discredit it right away, but I think it might be a little bit exaggerated, given facts such as:

In the United States the proportion of people aged 65 or older increased from 4% in 1900 to about 12% in 2000. [Citation] And in the entire world we are sitting at ~ 7.9% of 65 and older currently. So this would mean we have about 550 million seniors. This would require that out of the other 100 billion people who are not living anymore, only 250 million of them could have reached age 65. While this seems small, we have to look at what life expectancy has been historically. Curves of life expectancy in the past have looked like this:

The life expectancy curve is essentially unchanging, until the development of science and technology, and then it explodes. This gives more possibility to the "0.25% chance of reaching age 65" that is a requirement for the 2/3 statement. So as a whole, it may be viable but I would probably feel more comfortable with a statement such as "Most likely, 1/3 of the people who have reached 65 are alive today."

Finally, it is important to note that huge infant mortality rates were a large part of low life expectancy in the past. There is an interactive graph that showed age breakdown for each year, here. This graph represents some amusing data points, such as the claim that it’s impossible to die between the ages of 20 and 26.

Lunar Eclipse

You may have noticed, with Saturday's total lunar eclipse, a dark patch that became visible around the moon. This is caused by the Earth's shadow. The shadow, which includes the atmosphere, suppresses the Rayleigh and Mie scattering components in the atmosphere and causes a local darkening. (The Rayleigh effect is the same effect that causes the sky to turn red at sunset.) While this is actually happening all the time, it is only so pronounced when seen against a low light background.

An easy way to explain evolution

Credit goes to Sc-tech