Recent comments in /f/askscience

Narwhal_Assassin t1_jb3mcuo wrote

Reply to comment by DevinVee_ in Does the age of the universe depends on where you are? by _bidooflr_

Imagine taking a picture of yourself and mailing it to your grandma. That picture shows how you look on the day you take it. It then travels through the postal system for a couple days (or weeks, or months, depending on how bad the system is). In that time, you could change a lot: you could shave your eyebrows, or dye your hair, or get a tattoo, or go tanning. However, the photo still shows the you from a couple days ago, so when your grandma sees it she only knows what you looked like then. The further away she lives, the more stuff can change in the meantime.

In the same way, photons are like pictures of the stuff that emitted them. When the Big Bang happened, a bunch of photons got shot out in all different directions. At the same time, space itself expanded, and it expanded a lot. The distance those photons had to travel went from almost zero to millions of light years faster than they could traverse it. Imagine if the postman was walking the 20 feet to your grandmas mailbox, when suddenly it grew into a 30 mile hike. He’d take a lot longer to bring her the mail. Eventually though, he would make it, and grandma would finally see your lovely face. In the same way, these photons would eventually make it to us, and we could see the early universe: it just takes 13 billion years to cross that gap, since space just keeps expanding while the photons move.

So yes, those photons are from the early early universe, because space itself expanded and made them travel for longer to reach us.

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dedokta t1_jb3l6sr wrote

Reply to Does the age of the universe depends on where you are? by _bidooflr_

Here's an analogy that's going to fall down if you think about it too much, but it's still valid.

Consider the universe as the surface of a spherical balloon. Don't consider the void in the centre, just the surface. As the balloon expands all parts of the surface move away from you in all directions. The universe expands. If you were to measure the circumference of the balloon and you knew the starting size and the rate of expansion then you'd know the age.

You could do this from any point on the balloon.

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Bunsen_Burn t1_jb3jo8m wrote

Reply to comment by amagicalwizard in Does galvanic corrosion take place when aluminum bronze is in contact with steel? by UserNo485929294774

Carbon fiber always gets people.

Got called in to consult with a development team that was having paint issues. Their brilliant plan which they had spent the last six months perfecting was changing out glass fibers for carbon fibers in an injection molding system. Which is fine and dandy except they also:

Vibromelted brass inserts into the plastic in order to secure the lid to the body with cadmium coated steel bolts and then sprayed the entire interior with an EMI coating witch was 92%wt silver.

It was hilariously bad. The piece was supposed to pass 168 hours salt fog with no visible signs of rust. The first check was 18 hours into the run and not only was there corrosion products running off the side, it was red rust from the steel.

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Chance_Literature193 OP t1_jb3h7l0 wrote

Reply to comment by perta1234 in Understanding Heritability (h^2) Statistic? by Chance_Literature193

Oh I see. You mean Bernoulli trial. Interesting, would call a something discrete qualitative too or just Bernoulli?

When I asking about the conditional probability of trait given parents have trait, I was really thinking of something like height (continuous), but figured find out if such statistic exists in the simpler situation where we consider a yes or no trait.

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