Space questions from my son

  1. What happens when you shoot air into the space?
  2. If there’s no oxygen in space, how can the sun burn?
  1. The air spreads out through the empty space.

  2. The sun doesn’t burn. The sun is undergoing a massive fusion reaction.

Thanks. What’s a fusion reaction, by the way?

Take two hydrogen atoms, smash them together really hard, and you get light, heat, and a little helium. The convenient thing is that the heat produced by the reaction is enough to start nearby hydrogen atoms smashing into each other, and you end up with a lovely big ball o’chain-reacting hydrogen.

  1. the air explodes outward from the point of origin in all directions equally.

  2. The sun “burns” Hydrogen atoms into Helium atoms (Fusion). Simply Two Hydrogen atoms become one helium atom. It takes a lot of pressure to cause this to happen - the kind you only find at the center of really massive objects like stars. No Oxygen is required. This happens deep within the sun, but releases enough energy outward to heat the rest of the sun into a glowing ball of hydrogen gas.

Under conditions of high enough pressure and temperature, hydogen atoms can stick together to make heavier atoms. This releases a little bit of energy each time it happens. When you have as much hydrogen in one place as you do in the Sun, all thos elittle bits of energy add up to a lot of light and heat.

It is the same reaction as in an H-bomb. We use an ordinary atomic bomb as the primer to detonate an H-bomb.

More than you ever need to know about Main Sequence stars.

Actually you take four hydrogen atoms and smush them together to make a helium atom.

As noted the sun does not “burn”. Burning usually implies a chemical reaction (burning wood is a chemical reaction that releases heat) using an oxidizing agent (usually oxygen). Fusion is a nuclear reaction.

In the sun, if you measure the mass of the four hydrogen atoms, you will find they mass a bit more than the resulting helium atom. The mass that is “lost” (quotes because nothing is actually lost) is released as energy. That energy makes the sun shine.

It takes colossal temperatures and pressures for fusion to happen. In the case of the sun that is in the core. Fusion does not occur anywhere in the sun except the core.

Also, when we say there is no air in space, we mean that there is no appreciable atmosphere in between the various bodies of the solar system. Each planet (except for Mercury and Pluto) has an atmosphere (their own air) and even the Sun, since it is a ball of exploding gas, could be considered to be all air, just not the type of air we can breathe.

The Sun is a mass of incandescent gas
A gigantic nuclear furnace
Where hydrogen is built into helium
At a temperature of millions of degrees.

Fun fact for your son: pound for pound, he produces more heat than the Sun.

On this topic, the OP’s son may like the album from They Might Be Giants, called Here Comes Science. They include this song, and then the rebuttal called “Why Does the Sun Really Shine,” which features the line, “The sun is a miasma of incandescent plasma.”

Actually, the most common reaction in the Sun requires 6 Hydrogen atoms. (You end up with a Helium nucleus and 2 protons at the end. But the 2 extra are a must.) And they’re not really atoms, just naked protons and some free floating electrons.

Your son, by the way, produces that heat by oxidation.

And here’s the video:

http://www.youtube.com/watch?v=3JdWlSF195Y

I can’t find a link, but I recall that a Victorian-era scientist calculated the possible range of lifetime of the Sun based on it actually burning (Oxidizing), and got answers that were clearly too small. He then realized that some other process must be generating the energy, but didn’t know what it could be.

And more poop.

You may be wondering how pressing Hydrogen together into Helium can create so much energy. Matter (what we’re made of) can be thought of as frozen energy. Einstein discovered that the total energy in matter is equal to the amount of the mass times the square of the speed of light: E=mc^2. The square of the speed of light means that even a tiny amount of matter contains a HUGE amount of energy! In the core of the sun, the helium molecule that is produced by fusion weighs less than the sum of the hydrogen molecules that were pressed together to make it. The lost mass is converted directly to energy which is the source of the heat in the sun.

Here’s another fun fact for your son. As the sun exhausts its usable hydrogen it will start to push the helium molecules together to form carbon. If the star is large enough it will keep pressing heavier and heavier molecules together creating all of the heavier elements that we see around us. When those stars finally run out of fuel they explode in giant supernova explosions which scatter those molecules into space. Our solar system condensed out of one of those clouds, and thanks to the heavier elements that were in there, our planets formed. In fact, every molecule in your body was, at one time, in the center of a giant star!

Wouldn’t it just fall back to Earth, just like everything else you shoot into space?

I once asked here how big a bomb an adult human would be if they had their mass converted to energy. The answer was around 6,750 megatons (for comparison the largest nuclear bomb ever built was 100 megatons).

A bit more detail here I think is needed.

As the sun runs low on hydrogen in the core it will fuse helium into carbon going on up. Eventually you get kind of an onion-like aspect to the sun. An outer ring fuses hydrogen, ring below that fuses helium, ring below that fuses carbon and so on.

However, once you reach iron fusion will no longer occur. Fusing iron is a net energy loss. Our sun is not big enough to reach iron however.

The heavier elements past iron get formed in the supernova that occurs when the nuclear engine in big stars turns off. With no outward pressure from fusion occurring the star collapses in on itself. Temperatures and pressures in the core soar to stupendous levels and iron and heavier elements are fused. This results in a truly massive release of energy in a very short time and the star explodes seeding the area with a nebula that someday may recollapse and form a new solar system with planets and all that.

The process is called nucleosynthesis.