THANK YOU!

I released an article on Time Dilation.
http://www.aliceinphysics.com/#web/mathematics/en/tin_soldiers1.html

Han Erim

[[***“In order for human-alien reproduction to be possible, both species would have to have”***

None of these are impossible, nor is any combination of them. Do they sound implausible? Yes, but only because you strongly weighted your descriptions to make them sound that way.

Do you want a quantitative estimate? For all conditions to be met is implausible, pal. Low-probability.

[[Honestly, I’m not inclined to believe it myself,]]

But you couldn’t resist a chance to yank my chain anyway, right?

[[ but that doesn’t make it bad physics or even bad biology. I could even be wrong. After all, I have no idea what I’m talking about. ]]

I have to agree with you there.

[[A key point here (and the one I made earlier) is that there are no known examples of alien life. This makes even the probabilities impossible to determine.]]

No, it does not. We may not be able to determine them exactly, but we can make pretty darn good order of magnitude estimates.

[[Consequently, Carl Sagan and Larry Niven don’t have the slightest clue what they’re talking about, and neither do you.]]

Don’t get me confused with you. You have no idea what you’re talking about. I do have an idea what I’m talking about. See the difference?

“In order for human-alien reproduction to be possible, both species would have to have”

None of these are impossible, nor is any combination of them. Do they sound implausible? Yes, but only because you strongly weighted your descriptions to make them sound that way.

Honestly, I’m not inclined to believe it myself, but that doesn’t make it bad physics or even bad biology. I could even be wrong. After all, I have no idea what I’m talking about.

A key point here (and the one I made earlier) is that there are no known examples of alien life. This makes even the probabilities impossible to determine.

Consequently, Carl Sagan and Larry Niven don’t have the slightest clue what they’re talking about, and neither do you.

I think that worrying about sound in space is as pointless as wondering where that orchestra playing the rousing battle theme is at.

[[Point #5 is a matter for exobiology and, like that fledgling field, remains entirely hypothetical. Easy human-alien reproduction SEEMS quite implausible, but is by no means impossible, especially PHYSICALLY.]]

In order for human-alien reproduction to be possible, both species would have to have

1) The same set of nucleic acids. Note that over 1,000 varieties of RNA have been found.

2) The same set of amino acids. We use 20 out of several times that number.

3) The same optical activity for three types of chemicals — nucleic acids, amino acids, sugars. We have left-handed aminos and right-handed sugars. I forget which chirality nucleic acids have.

4) The same genetic code. Not all organisms have exactly the same genetic code even on Earth.

5) The same mitochondrial genetic code. See above. If the mitochondria don’t work, the embryo will be a cancerous mass, not a viable descendant.

6) The same or a close number of chromosomes. Human-ape interbreeding is impossibly, and one reason for that is that great apes have 48 chromosomes and humans have 46. Donkeys have 62 and horses have 64, but although they can reproduce, it only works for one generation. Mules and hinneys are sterile.

7) The same sex-determination mechanism (XX-XY). Many other types are known; e.g. birds and lizards have ZZ-ZW, where the heterozygote is male. Spiders have systems involving up to five chromosomes (e.g. XXYYY).
The same mode of pregnancy — placental pregnancy as opposed to marsupial pregnancy, cleidoic eggs or amphibian eggs.

9) Roughly the same genital pH. If the alien babe has a vaginal pH of 5, Captain Kirk’s sperm are going to get denatured before they get anywhere useful.

10) That neither partner will become allergic to the alien proteins of the other. That would abort the pregnancy pretty fast.

I’ll leave out similar methods of copulation, since we can assume artificial insemination. That might take care of objection #9, as well.

Human beings can’t reproduce with chimpanzees, and we share 95% of our genome with chimpanzees. To expect that we could reproduce with someone who came from a planet where evolution went on for billions of years out of touch with the Earth is just not very likely.

Carl Sagan: “Such matings are as reasonable as the mating of a man with a petunia.”

Larry Niven: “LL could more likely mate with an ear of corn than with Kal-El.”