The dumb questions thread

[Shadowy Man]

Watching the NASA SpaceX launch earlier and now rewatching some of the live stream. How do they know 100% sure that none of those astronauts have COVID?

They were quarantined prior to launch.

 

[Angry Floof]

Watching the NASA SpaceX launch earlier and now rewatching some of the live stream. How do they know 100% sure that none of those astronauts have COVID?

They were quarantined prior to launch.

But they've since been exposed to other people throughout the preparation process, being touched and spoken to albeit through masks, and they can't always observe distancing such as when getting suited up.

 

[Shadowy Man]

Watching the NASA SpaceX launch earlier and now rewatching some of the live stream. How do they know 100% sure that none of those astronauts have COVID?

Watching the NASA SpaceX launch earlier and now rewatching some of the live stream. How do they know 100% sure that none of those astronauts have COVID?

They were quarantined prior to launch.

But they've since been exposed to other people throughout the preparation process, being touched and spoken to albeit through masks, but they can't always observe distancing such as when getting suited up.

I think I had heard that the whole team may have quarantined.

 

[Angry Floof]

Watching the NASA SpaceX launch earlier and now rewatching some of the live stream. How do they know 100% sure that none of those astronauts have COVID?

They were quarantined prior to launch.

But they've since been exposed to other people throughout the preparation process, being touched and spoken to albeit through masks, but they can't always observe distancing such as when getting suited up.

I think I had heard that the whole team may have quarantined.

Ah, so everyone who would come in contact with them was quarantined. That's a hell of a lot of people. But still there's a small risk when just before they go off to the launch pad, they visit with their families, who are masked, but the astronauts are not masked and distancing not observed. I guess still the risk is minimized as much as possible and still let them have time with their families before they go.

 

[bilby]

They were quarantined prior to launch.

But they've since been exposed to other people throughout the preparation process, being touched and spoken to albeit through masks, but they can't always observe distancing such as when getting suited up.

I think I had heard that the whole team may have quarantined.

Ah, so everyone who would come in contact with them was quarantined. That's a hell of a lot of people. But still there's a small risk when just before they go off to the launch pad, they visit with their families, who are masked, but the astronauts are not masked and distancing not observed. I guess still the risk is minimized as much as possible and still let them have time with their families before they go.

Back in the Apollo days, crews were strictly quarantined before launch, and were required to say goodbye to their families across the width of the Cape Canaveral perimeter road.

Ken Mattingley was famously selected as for Apollo 13, but dropped from the mission due to a brief contact with a possible case of Rubella (aka German Measles) three days before the launch (he never contracted the disease, and went to the Moon as CM pilot on Apollo 16).

 

[Loren Pechtel]

Watching the NASA SpaceX launch earlier and now rewatching some of the live stream. How do they know 100% sure that none of those astronauts have COVID?

It has been standard practice to quarantine astronauts before launch for a long time.

 

[James Brown]

Other than the sheer technical achievement of the thing, is there a practical purpose to calculating pi to hundreds or thousands of digits?

 

[skepticalbip]

Other than the sheer technical achievement of the thing, is there a practical purpose to calculating pi to hundreds or thousands of digits?

I think you will find that it is primarily mathematicians who get into such an exercise. I personally know of no physicists who find any practical purpose in concerning themselves with anything more than five or six decimal places. Generally four decimal places is more than enough.

 

[Shadowy Man]

Other than the sheer technical achievement of the thing, is there a practical purpose to calculating pi to hundreds or thousands of digits?

I think you will find that it is primarily mathematicians who get into such an exercise. I personally know of no physicists who find any practical purpose in concerning themselves with anything more than five or six decimal places. Generally four decimal places is more than enough.

A recently learned trick to a great approximation of pi is to remember the first three odd numbers and double them so you get 113355 then do;

Pi = 355/113 = 3.14159292

 

[bilby]

Other than the sheer technical achievement of the thing, is there a practical purpose to calculating pi to hundreds or thousands of digits?

I think you will find that it is primarily mathematicians who get into such an exercise. I personally know of no physicists who find any practical purpose in concerning themselves with anything more than five or six decimal places. Generally four decimal places is more than enough.

A recently learned trick to a great approximation of pi is to remember the first three odd numbers and double them so you get 113355 then do;

Pi = 355/113 = 3.14159292

An even easier way to remember an approximate value of pi, for use by physicists, is to remember '3'

 

[Wiploc]

'tis a favorite project of mine,
a new value of pi to assign.
i would fix it at 3,
for it's simpler, you see,
than 3 point 1 4 1 5 9.

​

--Idon'tknowwhowroteitbutIknowitwasn'tme
​

 

[Shadowy Man]

A recently learned trick to a great approximation of pi is to remember the first three odd numbers and double them so you get 113355 then do;

Pi = 355/113 = 3.14159292

An even easier way to remember an approximate value of pi, for use by physicists, is to remember '3'

That’s off by 4.5%, whereas 355/113 is good to dozens of parts per billion.

 

[Jokodo]

A recently learned trick to a great approximation of pi is to remember the first three odd numbers and double them so you get 113355 then do;

Pi = 355/113 = 3.14159292

An even easier way to remember an approximate value of pi, for use by physicists, is to remember '3'

That’s off by 4.5%, whereas 355/113 is good to dozens of parts per billion.

who *needs* dozens of parts per billion? mathematicians, that's who.

 

[Shadowy Man]

That’s off by 4.5%, whereas 355/113 is good to dozens of parts per billion.

who *needs* dozens of parts per billion? mathematicians, that's who.

22/7 is good to 0.04%

If you just need order of magnitude then pi=1 should be good enough. Pi^2=10.

 

[Bomb#20]

A recently learned trick to a great approximation of pi is to remember the first three odd numbers and double them so you get 113355 then do;

Pi = 355/113 = 3.14159292

An even easier way to remember an approximate value of pi, for use by physicists, is to remember '3'

Not really accurate enough for physicists. For physicists it's an empirical question. Follow:

1. Assume a spherical cow.
2. V = 4/3 pi r^3
3. m = V d
4. Cows are mostly water. Assume d = 1.0.
5. For the average cow, r = 74 cm, m = 680 kg. (Per Holstein Association USA (who used, inevitably, inches and pounds.))
6. 680000 = 4/3*pi*74^3*1.0
7. pi = 680000 / 540000
8. pi = 1.26

That '3' is easier to remember is neither here nor there. Physicists don't need to remember the value when we can easily derive it from first principles.

 

[Jokodo]

A recently learned trick to a great approximation of pi is to remember the first three odd numbers and double them so you get 113355 then do;

Pi = 355/113 = 3.14159292

An even easier way to remember an approximate value of pi, for use by physicists, is to remember '3'

Not really accurate enough for physicists. For physicists it's an empirical question. Follow:

1. Assume a spherical cow.
2. V = 4/3 pi r^3
3. m = V d
4. Cows are mostly water. Assume d = 1.0.
5. For the average cow, r = 74 cm, m = 680 kg. (Per Holstein Association USA (who used, inevitably, inches and pounds.))
6. 680000 = 4/3*pi*74^3*1.0
7. pi = 680000 / 540000
8. pi = 1.26

That '3' is easier to remember is neither here nor there. Physicists don't need to remember the value when we can easily derive it from first principles.

d = 1.0 only holds at 4° C. Sounds like a cow that's been floating in vacuum for too long...

 

[bilby]

A recently learned trick to a great approximation of pi is to remember the first three odd numbers and double them so you get 113355 then do;

Pi = 355/113 = 3.14159292

An even easier way to remember an approximate value of pi, for use by physicists, is to remember '3'

That’s off by 4.5%, whereas 355/113 is good to dozens of parts per billion.

So you're saying it's better than 95% accurate?

 

[Shadowy Man]

That’s off by 4.5%, whereas 355/113 is good to dozens of parts per billion.

So you're saying it's better than 95% accurate?

Which for practical applications is inadequate. Just for roughing things out, maybe.

 

[bilby]

That’s off by 4.5%, whereas 355/113 is good to dozens of parts per billion.

So you're saying it's better than 95% accurate?

Which for practical applications is inadequate. Just for roughing things out, maybe.

What do you mean, "inadequate"?

p>0.05 is the gold standard for statistical studies. Most practical applications of pretty much anything would consider plus or minus 5% an excellent degree of accuracy.

Obviously there are some applications that require much greater precision. But I would estimate* that that's fewer than five percent of real world applications.









*guess

 

[Shadowy Man]

Which for practical applications is inadequate. Just for roughing things out, maybe.

What do you mean, "inadequate"?

p>0.05 is the gold standard for statistical studies. Most practical applications of pretty much anything would consider plus or minus 5% an excellent degree of accuracy.

Obviously there are some applications that require much greater precision. But I would estimate* that that's fewer than five percent of real world applications.









*guess

If I were building something and I calculated the sizes of its parts to 5% then most things wouldn’t fit together.

If the figure error in my optics were 5% i would not be able to form a good image.

In my spectrograph if I only knew the wavelengths of each pixel to 5% then I’d never get a decent fit.

I could go on. But we may just travel in different circles. And use different levels of precision for our respective work.