5 ms·

Why are we needing fusion reactors to see 100M+ degrees if the center of a basic bitch star is only 15m? (Serious question here)

donkarma 5y ago
From my understanding, stars get to cheat to get a lot of pressure by just being really big, whereas we have to do it with lots of fancy techniques
- speed_spread 5y ago
  Hum, aren't we the ones cheating, then?
  - anonytrary 5y ago
    There is no cheating in nature. If it works, it works.
    - thaumasiotes 5y ago
      I found a humorous essay years ago on the topic "should performance-enhancing drugs be allowed in math?" Can't find it now.
      - anonytrary 5y ago
        Whatever it takes for them! Nature will course correct if amphetamines hurt math professors to the point where they can no longer contribute to math. As of right now, it seems to be helping them.
ProjectArcturis 5y ago
It's not about temperature, it's about pressure. The only way to achieve the pressure needed for fusion on earth is to heat up the plasma much hotter than the sun.
- mgarfias 5y ago
  Copy, thanks. Knew there had to be something I didn’t understand
DuskStar 5y ago
Because a star like ours has a power density of a compost pile. You can run a generator from one, but you need a LOT of it to get any appreciable power. Ludicrous amounts, really. Thankfully for the viability of fusion, reactions scale with temperature to the 4th power (iirc), so you get 10000x higher power density by running things at 10x the temperature. Since the containment difficulty goes up at a far slower rate than this, it makes higher temperatures both more space efficient and power efficient, and eventually lets you extract more energy from the fusion reactions than you're spending on magnetic containment.
- throwawayzRUU6f 5y ago
  Or, to put it to intuitive human scale - a cubic meter from the very core of the Sun outputs 270W - about the consumption of a single gaming console, not enough to power even a vacuum cleaner. Coincidentally, it's roughly the power output of a square meter solar panel.
- Kliment 5y ago
  4th power of magnetic field strength, not temperature. Increasing magnetic field strength increases your density and your temperature, and that compounding is what gets you 4th power scaling.
noobermin 5y ago
They have nowhere near the density needed to do stellar levels of fusion. You need energy \times time \times areal density. For example, the inertial confinement fusion folks do very high densities but interactions that last for much less than a second.
bmitc 5y ago
The sun has a lot of material and thus a lot of gravity and pressure.
petters 5y ago
The sun has a power output per volume of a compost. Quite literally. We need more :-) Edit: Saw another comment explaining this now. The sun is really very slow. But it has been around for billions of years.

donkarma 5y ago

From my understanding, stars get to cheat to get a lot of pressure by just being really big, whereas we have to do it with lots of fancy techniques

speed_spread 5y ago
Hum, aren't we the ones cheating, then?
- anonytrary 5y ago
  There is no cheating in nature. If it works, it works.
  - thaumasiotes 5y ago
    I found a humorous essay years ago on the topic "should performance-enhancing drugs be allowed in math?" Can't find it now.
    - anonytrary 5y ago
      Whatever it takes for them! Nature will course correct if amphetamines hurt math professors to the point where they can no longer contribute to math. As of right now, it seems to be helping them.

ProjectArcturis 5y ago

It's not about temperature, it's about pressure. The only way to achieve the pressure needed for fusion on earth is to heat up the plasma much hotter than the sun.

mgarfias 5y ago
Copy, thanks. Knew there had to be something I didn’t understand

DuskStar 5y ago

Because a star like ours has a power density of a compost pile. You can run a generator from one, but you need a LOT of it to get any appreciable power. Ludicrous amounts, really. Thankfully for the viability of fusion, reactions scale with temperature to the 4th power (iirc), so you get 10000x higher power density by running things at 10x the temperature. Since the containment difficulty goes up at a far slower rate than this, it makes higher temperatures both more space efficient and power efficient, and eventually lets you extract more energy from the fusion reactions than you're spending on magnetic containment.

throwawayzRUU6f 5y ago
Or, to put it to intuitive human scale - a cubic meter from the very core of the Sun outputs 270W - about the consumption of a single gaming console, not enough to power even a vacuum cleaner. Coincidentally, it's roughly the power output of a square meter solar panel.
Kliment 5y ago
4th power of magnetic field strength, not temperature. Increasing magnetic field strength increases your density and your temperature, and that compounding is what gets you 4th power scaling.

noobermin 5y ago

They have nowhere near the density needed to do stellar levels of fusion. You need energy \times time \times areal density. For example, the inertial confinement fusion folks do very high densities but interactions that last for much less than a second.

bmitc 5y ago

The sun has a lot of material and thus a lot of gravity and pressure.

petters 5y ago

The sun has a power output per volume of a compost. Quite literally. We need more :-) Edit: Saw another comment explaining this now. The sun is really very slow. But it has been around for billions of years.