Why Do the Sun and the Moon Appear to be the Same Size?

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It’s just kind of a strange coincidence. The diameter of the Sun is about 400 times larger than the Moon's, but it is also roughly 400 times farther away from Earth. These two qualities almost cancel each other out, and the Sun usually winds up looking either the same size or just a wee bit bigger than the moon to us.

How do we know how far away and how big the Sun and Moon are in the first place?

Since we can’t just wrap a giant measuring tape around a celestial body, we have to get a little creative.

Look up at the sky and imagine it as a big dome, which goes all away around the Earth, with the Sun, Moon and stars projected onto its surface. This is a neat little hypothetical that astronomers call the celestial sphere. If we think of the sphere as being 360 degrees, like a circle, we can talk about the things we see on the dome in terms of angular size (that is, the “visual diameter” of the object measured as an angle) and angular distance (the distance separating two objects measured as an angle).

We’ve been able to get a better handle on the actual distance thanks to spaceflight and laser and radar technology. For the Moon, Apollo astronauts left retro-reflectors on its surface, which we bounced lasers off of from 1969 to 2009. By timing how long it took for the laser beam to make the trip there and back, astronomers could work out the Moon’s physical distance.

For the Sun, we tried the same sort of thing and bounced radio waves off it, but the star’s outer atmosphere scattered the waves too much for accurate measurements. Astonomers switched to a more reliable method that uses German astronomer Johannes Kepler’s Third Law of Planetary Motion, observations of the other planets’ movements, and radar measurements of their distances to work out an indirect, but accurate, measurement for the distance of the Sun.

Once we have the angular size of something in the sky and its actual distance, we can use them to calculate the object’s physical diameter.

But don't get used to them looking this way

The Sun and Moon didn’t always look so close in size from Earth, though, and they won’t continue to do so forever. The Moon is moving away from Earth at a rate of about 4 centimeters per year. In a few billion years, our descendants won’t be looking up at the same sky we are, and the size difference between the Sun and Moon will be much more noticeable.

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What’s the Difference Between Prison and Jail?
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Many people use the terms jail and prison interchangeably, and while both terms refer to areas where people are held, there's a substantial difference between the two methods of incarceration. Where a person who is accused of a crime is held, and for how long, is a factor in determining the difference between the two—and whether a person is held in a jail or a prison is largely determined by the severity of the crime they have committed.

A jail (or, for our British friends, a gaol) refers to a small, temporary holding facility—run by local governments and supervised by county sheriff departments—that is designed to detain recently arrested people who have committed a minor offense or misdemeanor. A person can also be held in jail for an extended period of time if the sentence for their offense is less than a year. There are currently 3163 local jail facilities in the United States.

A jail is different from the similarly temporary “lockup”—sort of like “pre-jail”—which is located in local police departments and holds offenders unable to post bail, people arrested for public drunkenness who are kept until they are sober, or, most importantly, offenders waiting to be processed into the jail system.

A prison, on the other hand, is usually a large state- or federal-run facility meant to house people convicted of a serious crime or felony, and whose sentences for those crimes surpass 365 days. A prison could also be called a “penitentiary,” among other names.

To be put in a state prison, a person must be convicted of breaking a state law. To be put in a federal prison, a person must be convicted of breaking federal law. Basic amenities in a prison are more extensive than in a jail because, obviously, an inmate is likely to spend more than a year of his or her life confined inside a prison. As of 2012, there were 4575 operating prisons in the U.S.—the most in the world. The country with the second highest number of operating prisons is Russia, which has just 1029 facilities.

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What Do Morticians Do With the Blood They Take Out of Dead Bodies?
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Zoe-Anne Barcellos:

The blood goes down the sink drain, into the sewer system.

I am not a mortician, but I work for a medical examiner/coroner. During an autopsy, most blood is drained from the decedent. This is not on purpose, but a result of gravity. Later a mortician may or may not embalm, depending on the wishes of the family.

Autopsies are done on a table that has a drain at one end; this drain is placed over a sink—a regular sink, with a garbage disposal in it. The blood and bodily fluids just drain down the table, into the sink, and down the drain. This goes into the sewer, like every other sink and toilet, and (usually) goes to a water treatment plant.

You may be thinking that this is biohazardous waste and needs to be treated differently. [If] we can’t put oil, or chemicals (like formalin) down the drains due to regulations, why is blood not treated similarly? I would assume because it is effectively handled by the water treatment plants. If it wasn’t, I am sure the regulations would be changed.

Now any items that are soiled with blood—those cannot be thrown away in the regular trash. Most clothing worn by the decedent is either retained for evidence or released with the decedent to the funeral home—even if they were bloody.

But any gauze, medical tubing, papers, etc. that have blood or bodily fluids on them must be thrown away into a biohazardous trash. These are lined with bright red trash liners, and these are placed in a specially marked box and taped closed. These boxes are stacked up in the garage until they are picked up by a specialty garbage company. I am not sure, but I am pretty sure they are incinerated.

Additionally anything sharp or pointy—like needles, scalpels, etc.—must go into a rigid “sharps” container. When they are 2/3 full we just toss these into one of the biotrash containers.

The biotrash is treated differently, as, if it went to a landfill, then the blood (and therefore the bloodborne pathogens like Hepatitis and HIV) could be exposed to people or animals. Rain could wash it into untreated water systems.

This post originally appeared on Quora. Click here to view.

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