So I started uni a couple of weeks ago, and along with work+personal projects+writing for the student magazine+social life, it’s been sucking up a whole lot of my time. When I am actually home, usually I’m so exhausted or so laden with homework that I don’t have time to write for you guys.
BUT, I’ve been learning a lot of cool things that I want to write about, so I’m going to try and manage my time better and post at least a couple of articles per week!
Anonymous asked: HOW EXCITED ARE YOU FOR COSMOS
I’ll be a 100x more excited when I can legally watch it in my country.
Anonymous asked: Hey in concurrence with the C14 question, could you then explain what type of dating is used for things older than 60000 yrs old (fossils for example)?
Carbon-14 isn’t the only radioactive element found naturally in living beings—there are a whole host of other useful radioisotopes with longer half-lives so we can date much older biological and geological samples with accuracy. For example, Potassium-40 is found naturally in living bodies and has a half-life of 1.26 billion years; Uranium-235 has a half-life of 704 million years; Uranium-238 has a half-life of 4.5 billion years; Thorium-232 has a half-life of 14 billion years; Rubidium-87 has a half-life of 49 billion years, etc…
One of the most well-known is Potassium-40, which forms argon gas as it decays. Argon doesn’t normally combine with other elements, so when minerals form they are originally argon free. But if the mineral contains Potassium-40, then the decay will create fresh argon gas that will be trapped inside. If a geologist simply measures the argon gas inside the mineral, they can calculate how much the Potassium-40 has decayed and therefore when the mineral was formed.
j-mcshane asked: So I understand the concept of carbon dating, but since all matter is as old as the universe, how does it really give an "age?" Love your blog and look forward to your posts btw! :D
Okay, cool question! I’ll give a quick rundown of the concept of carbon dating first, for those who are a bit hazy on the matter.
Carbon dating is a way of determining how old certain biological artifacts are by measuring the amount of Carbon-14 in them. Carbon is a basic building block of life so it’s in all living things, but the normal molar mass is 12. Carbon-14 is an isotope (atoms with the same proton count but different number of neutrons) and is rarer, and it’s manufactured in the upper atmosphere by the collision of cosmic rays in the upper atmosphere, turning ordinary nitrogen atoms into Carbon-14. These atoms combine with oxygen to form carbon dioxide, which is absorbed naturally by plants, and eventually makes its way into all living organisms.
But Carbon-14 isn’t a stable element—like many isotopes, it’s radioactive. It decays, with a half-life of approximately 5,730 years, meaning that every 5,730 years, the amount of Carbon-14 has reduced by half. While the organism is alive, its Carbon-14 atoms are decaying but it’s also taking in new carbon all the time, so the percentage of Carbon-14 in its body is always constant. All living organisms have the same percentage—but as soon as they die, they stop taking in new carbon.
Essentially, in carbon dating we measure the amount of Carbon-14 in a body and use its half-life to calculate how long it’s been since the organism died. For example, if the percentage of carbon-14 is half of what it should be in living organism, then the organism has been dead for 5,730 years. We can measure all kinds of objects that once had living material in them—not just fossils or bones that were once living organisms, but also wood, cloth, plant fibres…anything with organic origin.
This measurement is only accurate for organisms that lived up to around 60,000 years ago, because then the amount of carbon gets so small it’s insignificant.
So, to answer your question more clearly: carbon dating measures the levels of Carbon-14 to determine how long since the living organism died and stopped taking in new Carbon-14.
So I am now in possession of a frankly adorable ipad mini, courtesy of my uni, and I intend to use the gift in good faith. Tell me, science enthusiasts and purveyors of good taste: what are the best science and educational apps?
I’ll compile them into a list for everyone to see once I’ve checked them out!
hit me nerds
Anonymous asked: So I've always wondered this when I watch an airplane pass in the day: why do they leave a trail of water vapour in their wake? Does it have to be very humid air? Or cold air?
Those trails are actually called contrails, which is short for “condensation trails.” They’re formed when the hot humid air thrust out of jet exhaust collides with the wet, cold air of the upper atmosphere, condensing into little water droplets that quickly freeze into ice crystals.
Essentially, contrails are a type of cirrus cloud!
The air definitely has to be damp and cold—that’s why sometimes planes don’t leave contrails, or leave contrails that break off and restart again, because in dry air they don’t form, and the sky is a layered mix of air of different moisture levels.