>So to estimate heritability, you regress your height against the average of your parents' heights.

No, you can't estimate heritability that way, because this can't distinguish between genetic and environmental transmission of traits.

Traditionally, heritability is estimated with twin studies, using Falconer's formula. You compare the correlation between pairs of monozygotic twins to the correlation between pairs of same-sex dizygotic twins. You can exploit the fact that MZ twins are twice as genetically similar as DZ twins but MZ and DZ twins are raised in equally similar environments to determine heritability.

So if the MZ correlation is 0.7 and the DZ correlation is 0.4, this implies that 60% (2 * (0.7 - 0.4)) of the variation in the trait can be attributed to genetics, 30% (1.0 - 0.7) to non-shared environment (environmental factors that differ between twins) and the remaining 10% to shared environment (environmental factors that are the same for both twins).

There are some additional adjustments you can do for things like gene-environment correlation, but that's the simplified version.

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yes, fixed, thanks!

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The part that really gets me is that the oldest part of the universe that we can see, has changed and moved for over 13 billion years since it's original light left in our direction. Everywhere we look we are seeing ancient history with our telescopes. The actual distant universe is not visible as it exists now, even if it does exist. So many of those stars could have died by now, we only see their distant past.

>It means 100% of the phenotypic variation depends on genes, which is quite different.

More precisely, it usually refers to share of the variation within the specific population being studied. For example, when measuring the heritability of height in a wealthy country, you will get a very high heritability estimate, perhaps 0.8-0.9. When measuring the heritability of height in a global population, you'll get a lower heritability estimate, because a significant fraction of your sample will have had their growth somewhat limited by environmental factors like undernutrition or disease. Conversely, if you're studying a population of clones, the heritability will be zero, because there's no genetic variation and all variation must be due to environment.

None of these estimates is more correct than the other, because heritability can only be defined for specific populations with specific distributions of genetic and environmental factors. There is no "ideal heritability."

>There is such thing as a universal "now".

Is this missing a negation or did I miss something?

This was incredibly well stated, thank you.

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Is it contagious for humans the same way like mad cow disease?

Eating supplies energy for moving and protein for building muscles.

CWD makes the proteins not fold and build correctly and eating more protein does nothing if your body doesn't use it. The muscles and brain proteins are dying faster then they are replaced and they are slowly wasting away.

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When we say that the universe is 13.7 billion years old, this is actually in the rest frame of the cosmic microwave background, not that of the Earth. However, the difference due to gravitational time dilation (mostly due to the galactic potential) and kinematic time dilation (since we're moving at ~370 km/s with respect to the cosmic microwave background) is of order one part in a million, so any ambiguity in the age of the universe due to time dilation is much smaller than the measurement uncertainty in the "13.7 billion years" value.

More generally, the question of whether the age of the universe depends on where you are depends entirely on what convention you adopt. There is no such thing as a universal "now". If you wanted, you could define that "now" means the elapsed time, in the cosmic microwave background frame, is 13.7 billion years. This convention is called "synchronous gauge" and is commonly used in cosmology calculations. Under this convention, the age of the universe does not depend on position.

For other conventions, like the "Newtonian gauge" that is also commonly used in calculations, the age of the universe does depend on position.

Yes, however we’re also able to take the age of the universe with respect to the rest frame of the cosmic microwave background. This is the age commonly given when someone asks the age of the universe. From the perspective of Earth, the universe is about 250k years younger.

Ya I knew how lightning happened but never considered the need for warm air. Thanks for the answer.

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This is the answer. CWD can be sun-clinical for as long as 3 years. The deer appears perfectly healthy. It’s really at the final stages that the deer becomes skinny and their behaviors change dramatically.

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