helium
esiegel | July 5, 2013"I see a lot of new faces. But, you know the old saying, 'out with the old, in with the nucleus.'" -The Simpsons
Looking around the Universe today, there's no doubt that there's plenty of hydrogen and helium around; after all, it's the nuclear fusion of hydrogen into helium that powers the vast majority of stars illuminating the entire cosmos!
Image credit: ESA/Hubble, NASA and H. Ebeling.
But here on Earth, hydrogen and helium are only a small part of the world we inhabit. By mass, hydrogen and helium combined make up far less than 1% of the Earth, and even if we restrict ourselves to the…
esiegel | December 12, 2012"I have this one little saying, when things get too heavy just call me helium, the lightest known gas to man." -Jimi Hendrix
Hendrix, as I told you once before, was almost right. We know of helium, conventionally, as the lighter-than-air gas that we fill balloons, blimps and zeppelins with in order to quickly and easily "defy gravity" here on Earth.
Image credit: Jonathan Trappe.
At least defying gravity is what it appears to do. But what's really going on is that helium is simply a very low-density gas. Our atmosphere, a mix of mostly Nitrogen (N2) and Oxygen (O2) gases, has an average…
gregladen | September 24, 2012Helium is rare. It is not produced in factories, and the places where it is found in the wild are unusual. When it gets lose, it tends to drift out into space. Simply put, it is a hard to find commodity with a limited availability. Helium is important in science. Big Science Projects like the Large Hadron Collider use Helium to cool magnets down to near absolute zero. Helium is also used in MRI machines, which have become an important part of medial research and diagnosis. Without a supply of Helium, a lot of important science projects would be in trouble.
From the BBC:
Prof Welton…
esiegel | August 19, 2012“If you want total security, go to prison. There you're fed, clothed, given medical care and so on. The only thing lacking... is freedom.” -Dwight Eisenhower
One of the greatest feelings is the freedom to travel, whether by your own power or a mechanical motor, far faster than your own legs can take you. Kimya Dawson understands how delightful this is (and how much is missing when you can't have it), as you can likely tell from her song,
My Bike
I've always loved the feeling of biking, fast, along a deserted road, feeling the wind rush past me and seeing the world go by.
Image credit: Flickr…
rallain | May 26, 2010I am still thinking about the Red Bull Stratos Jump. Sorry, but there is just tons of great physics here. Next question - how big of a balloon would you need to get up to 120,000 feet?
I am not going into the buoyancy details of Archimedes Principle - I think that was covered fairly thoroughly with the MythBusters floating lead balloon. However, in short, here is a force diagram for a floating balloon.
For a floating balloon, the buoyancy force must equal the weight of the whole thing. It turns out that the buoyant force is equal to the weight of the gas (or fluid) the object displaces…
esiegel | April 16, 2008Ahh, stars. Giant furnaces of nuclear fusion. Doing the stuff our Sun does, burning hydrogen fuel into helium (among other things) and emitting lots of visible light and energy in the process.
But when we take a look at brown dwarfs, they aren't like normal (i.e., main sequence) stars like our Sun. Instead of burning hydrogen into helium for their fuel, brown dwarfs don't generate enough pressure to make that happen; they can only burn hydrogen into deuterium.
Let's go over what the differences here are. A hydrogen nucleus is just a proton, with a mass of 938.272 MeV/c2. (I use these units…
esiegel | April 7, 2008What's going to happen to all the stars in the Universe as they get older? Well, just as nothing can live forever, stars can't live forever also. Why? Because they run on fuel: burning hydrogen into helium, for example. When they run out of fuel, something's gotta give. Barbara Ryden reminds us of an excellent and appropriate quote by Dylan Thomas:
Do not go gentle into that good night.
Rage, rage against the dying of the light.
But what exactly happens to the star depends very sensitively on what the mass of the star is.
If you've got a tiny little star, less than about 40% of the mass of…