Risu nodded. "This is true. Mars, for example, almost certainly had an atmosphere similar to the Earth's once."
Risu nodded and tapped the blackboard. "Number of hospitable planets that develop any kind of life," he read out. "This is, obviously enough, one of the more important milestones that we need to pass in our equation."
"Very good point, and that is indeed something we need to take into account. Any kind of life needs to develop to the point that it can send out detectable signals such as radio waves." He glanced at the blackboard. "I will add this momentarily, let's her what your classmates have to say first. Yes." He pointed at he next student.
"I definitely agree, Miss, er, Carlisle, correct?" He glanced at the girl questioningly. "The origin of life is, of course, a speculative subject, and one I'm not exceedingly familiar with, but we can suspect that after that initial point, the development of life proceeds in evolutionary terms all over the Universe as it does here on Earth. Of course, the results might well look very different. There is no reason to think that an extraterrestrial looks like a human but with, say, large eyes and green skin. We might very well have to discuss this later, though, as there are one or two important details to this argument."
"Stars in and of themselves cannot, as far as anyone knows," Risu said, "but they are, of course, very important to planets as a source of heat and energy. And there are many types of stars that do not lend themselves to support life on planets surrounding them. For example..." He paused and considered. "For example. A lot of stars in our galaxy are bound with a partner star. These are called binary systems. Two stars orbiting each other. Such a system would not be very good for the development of life on any surrounding planets because orbits tend to be very unstable. Planets will get too close or too far, they might be ejected out of the system into deep space, they might fall
into the stars... Generally a single star of a certain type, such as our Sun, is thought to be a requirement for life to develop, especially to the point of a civilisation, not just bacteria."
He picked up his wand and tapped the blackboard once more. "To recap briefly, the most important thing to add is that once life has begun on a planet, this life needs to develop to a point where it is advanced enough to be noticeable to other life. And allow me to reorder this list quickly." The words changed position on the blackboard.
Calculating the number of extraterrestrial civilisations we can communicate with- Rate of star formation
- Number of stars with planets
- Number of hospitable planets
- Number of hospitable planets that develop any kind of life
- Number of planets with life where the life becomes advanced enough to send out signals
He turned around. "Looking at our little list, it seems like we have a pretty good grasp on what our own Drake equation would have to include already. There is one last factor to add, and I will just do this for you: We need the
length of time that any civilisation sends those signals into space. Any advanced civilisation that only sent out signals for, say, a few seconds would most likely not be noticed."
Calculating the number of extraterrestrial civilisations we can communicate with- Rate of star formation
- Number of stars with planets
- Number of hospitable planets
- Number of hospitable planets that develop any kind of life
- Number of planets with life where the life becomes advanced enough to send out signals
- Length of time the advanced life spends on sending signals
"And here we have our very own equation. Now, are there any questions?" He looked around.
OOC: MissFeenella, I'll include your post in the next one. This one is super huge already. ^^
Same with you, Chris.