Recent comments in /f/explainlikeimfive

Phage0070 t1_j8y56ff wrote

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Gnonthgol t1_j8y504h wrote

In the 1980 movie "Airplane!" the cause of the disaster was some bad fish served on the flight which incapacitated both pilots. Even though this scenario was not realistic in reality most airliners introduced a policy of not having the pilots eat the same food in order to please public opinion. In practice this policy have not been enforced very hard and a lot of airliners have removed it by now.

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StupidLemonEater t1_j8y33cw wrote

Have you ever seen the movie Airplane!? If you haven't, go see it, it's the funniest movie of all time.

Anyway, in that movie, the pilot, co-pilot, and flight engineer (from back when commercial planes still had engineers) all become deathly ill from food poisoning from eating the same in-flight meal, and the plane has to be landed by one of the passengers. And although it may all be a big joke in the movie, that is the exact situation that rule is meant to prevent. It's not actually mandated by law (at least not by the FAA) but it is policy for most airlines.

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l__Scarecrow__l t1_j8y2nlx wrote

Not being a dick, but why does this sub sometimes have REALLY obvious questions & answers that can be Googled in 2 seconds. Type "Why does a pilot and his co-pilots not eat the same food on a flight?" as per the title into Google right now and see what I mean. You don't even have to click a link to see the answer.

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stairway2evan t1_j8y1y5a wrote

Airline food is prepared in big batches, and then split between multiple trays. So if something bad got into, say, the chicken meal, it could possibly make everyone who ate that meal very sick. If both pilots get very sick at the same time, it might get very dangerous.

It's a longshot, but it's a possibility that they want to avoid no matter what. So just to be extra safe, they always eat separate meals, so that even if the chicken meal is contaminated, the beef meal, or the vegetarian meal is probably safe, for example.

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left_lane_camper t1_j8y0hpo wrote

The speed of light is directly related to the permittivity (ε_0) and permeability (μ_0) of free space, via

c = ( ε_0 μ_0 )^1/2

as a consequence of building the wave equation from Maxwell's equations. Though whether this answer is in any way satisfying depends on whether one considers the speed of light or these other EM properties of free space to be more fundamental (and, in general, we usually define ε_0 and μ_0 with c as well, simply by re-arranging the equation above). But changing c would require changing one or both of these other fundamental constants as well.

My personal favorite answer, though, is when you ask someone who does GR or cosmology research about why the speed of light is what it is and they look at you like you have three heads and say "I don't know what you mean, the speed of light is exactly dimensionless 1".

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explainlikeimfive-ModTeam t1_j8xzike wrote

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Your submission has been removed for the following reason(s):

  • Rule #2 - Questions must seek objective explanations

  • Straightforward or factual queries are not allowed on ELI5. ELI5 is meant for simplifying complex concepts (Rule 2).


If you would like this removal reviewed, please read the detailed rules first. If you believe this submission was removed erroneously, please use this form and we will review your submission.

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Safe_T_Cube t1_j8xyzdo wrote

As far as we know the universe is infinite, so anything moving any speed will be miniscule in comparison.

What you're thinking of is probably the observable universe, which itself is defined by the speed of light. You can only see light that has had enough time to travel from its source to your eye.

This means what you think of as the universe is defined as speed of light * the age of the universe. If that were the only factors it would always take you the lifetime of the universe to reach the edge of the observable universe while traveling the speed of light.

However the universe is also expanding, the universe is constantly moving away from you, faster then the speed of light for things far enough away. Because of that the universe is much bigger than just the speed of light times the age of the universe, it's roughly the speed of light * the age of the universe * the rate of expansion, so big that you will never be able to reach all that you can see (as far we understand).

It's kind of like asking why a second is so short in comparison to your entire life. Your life is constantly getting one second longer for every second that passes, but at the beginning there was a point where one second was your entire life. Not accounting for expansion, the radius of the observable universe gets one light second bigger every second, but at one point the "observable" universe was only one light second across.

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breckenridgeback t1_j8xx4is wrote

Expansion of the Universe aside, the size of the observable Universe (the only "size of the Universe" we can really observe) is approximately the age of the Universe times the speed of light. (Expansion has increased it well beyond this value - it's about four times that - but it's still on roughly the same order of magnitude.) So a simple answer to your question is "the Universe is old, so light has had a long time to travel, so the most distant parts we can see are very far away".

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rasa2013 t1_j8xqxwu wrote

It's a good question! This type of question (about the size of the universe and the speed of light) is one of the reasons why we developed a theory that the universe had a growth period we refer to as cosmic inflation.

In the very early universe, the universe expanded faster than the speed of light to become quite big. This doesn't break any laws of physics because space isn't a "thing" the way a photon or a calcium atom is a thing. It can expand faster than light moves. That is one of the reasons light speed is dwarfed by the size of the universe. The other reason, of course, is that the universe is very old. Billions of years is an amount of time our brains just don't comprehend.

https://en.wikipedia.org/wiki/Inflationary_epoch

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