RE: Heavy Planet Hypothesis (was: RE: Burning the Cosmic Commons)

Billy Brown (
Thu, 11 Mar 1999 09:07:02 -0600

David Blenkinsop wrote:
> I'll refer you here to, and
> the comment at the end of that page related to stellar flaring and the
> for life-promoting stars to be more massive than M-class on that account.

Well, since they don't cite any details its hard to know what their concern is. I will say that NASA tends to be very conservative about that kind of estimate - i.e. their criteria is closer to "would we want to live there" than "could life exist". We really don't know much about how much radiation resistance is possible in large organisms.

A solar flare would blanket the facing hemisphere of the planet with intense radiation, which would kill most types of land life. You are correct in assuming that a denser atmosphere provides better shielding, and would thus allow land life to evolve under a more variable star than would otherwise be the case. However, a few yards of water will provide better shielding than even the densest atmosphere, so it is very hard for such events to kill off sea life.

> These are the very points that interest me about a planetary situation
> would be much tougher to launch out of than our own. Right at the outset,
> would appear that regular bulk scale chemical rocket technology simply
> not do the trick of launching satellites to twice the orbital speed that
> require. Because of this, the ET's in that situation would miss out on the
> "dawn of the Space Age" as we've experienced it.

Ah, no. They would be limited to much smaller payloads (in proportion to rocket size), which would mean you'd need 1980s technology to put up Sputnik. Communication satellites would become practical with technology only slightly more advanced than what we have now. From there the progression would continue on in the same way - their launch costs remain about an order of magnitude greater than ours, so their use of space at any given time is much more limited than ours. When our launch costs fall to $1,000/lb, theirs are $10,000/lb. When advanced technologies like laser launch or nanotech construction give us $100/lb launch costs, they get $1,000/lb. They aren't barred from space, they just need better technology for any particular use.

> At the same time, if they take awhile developing nanotech and any related
> technologies that might be helpful, it's difficult to say for certain what
> other problems might come about as a result of missing that early
> opportunity. For instance, suppose that some of the ET's make use of
> technology to boost their own reproductive capacity....

So, if "A" goes wrong, then "B" might go wrong, which could lead to a purely speculative problem "C", which under some conditions could combine with problems "D" and "E", perhaps leading to problem "F"....

This is a long chain of speculative problems, most of which are suspect in the first place. That's a fatal flaw for any attempt to explain the Great Filter. If we say each of your steps happens in 99.99% of all cases (which is far to generous), we still end up with a fairly modest number of races actually being trapped this way.

It seems to me that you don't really appreciate the magnitude of the numbers involved in this problem. That, or you implicitly assume that the most advanced technology that anyone can ever invent is only slightly better than what we currently have. Putting some numbers in, what you're suggesting is that:

  1. Virtually all advanced life (99.99999% or so) evolves on heavy worlds orbiting dim stars. Earth is a freak of nature that can never occur under any reasonable conditions.
  2. No possible technology can ever make space launches from such a world even reasonably cost effective.
  3. If space launches are expensive, a technological civilization will never, ever expand beyond its home planet. Not even over the course of hundreds of millions of years. No matter what kind of social structure they have. No matter what psychological drives they may have.

All three of these propositions seem extremely implausible to me.

Billy Brown, MCSE+I