Jump to content

For Questions That Don't Merit Their Own Thread


Recommended Posts

44 minutes ago, razark said:

So, if I don't want to wait for the next season of a show, I can jump in the time pod, set it for six minutes, and it's a year later and I can watch the show now?

Or I can get in, take an 8 hour nap, and wake up in 80 years?

I think getting to Mars quickly may be the less interesting effect of this invention.

Its an imperfect stasis pod. Imperfect in that it will not last millions of years. But you can store hot food or ice-cream an year without maintenance. 
Or as you say you can jump to 2100 in 8 hours. Nice if you are dying of some condition. And you can simply do an second jump if no solution yet. 
Now as its imperfect it also don't make you invulnerable. 

Link to post
Share on other sites

1. Watch the 8th season of Game of Thrones and stop loosing time on the previous ones.

2. Jump to the late 2022 to have a look at the KSP-2 release and... jump again to the late 2023

Edited by kerbiloid
Link to post
Share on other sites

Could tornadoes be dispersed by detonating a tactical nuke (or sufficiently large bomb) in the eye of it? I mean, the explosive shockwave displace large amount of air instantly that should, in theory disrupt tornado's vortex and causes it to dissipate

Link to post
Share on other sites

Tornados are caused by unstable atmosphere. You get a powerful enough convective flow, and it will make a vortex. A nuke only makes this worse. Sure, it might disrupt the existing tornado, but conditions will be ripe for a new one to form from the mushroom pretty much immediately, and this time you'll have a radioactive tornado. 

Link to post
Share on other sites
25 minutes ago, K^2 said:

... and this time you'll have a radioactive tornado

Fun! 

1 hour ago, ARS said:

Could tornadoes be dispersed by detonating a tactical nuke (or sufficiently large bomb) in the eye of it? I mean, the explosive shockwave displace large amount of air instantly that should, in theory disrupt tornado's vortex and causes it to dissipate

Another problem is how rapidly they form (part of what makes them deadly).  Try to predict and then fly to and identify the tornado in time to disrupt?  Good luck. 

Also can't do it to Hurricanes. 

Nuking weather just isn't that smart 

Link to post
Share on other sites
On 1/8/2021 at 9:45 AM, ARS said:

I mean, the explosive shockwave displace large amount of air instantly that should, in theory disrupt tornado's vortex and causes it to dissipate

We actually did a less-than-explosive test on this, the way we actually did it was that if we can create a new eyewall on the outside of a tight, small eyewall then the magnitude of the storm could be reduced due to the slightly weaker vorticity.

Unfortunately, that is exactly how eyewall replacement works, and you end up with a stronger storm soon after the process ends.

Seriously, if you want your nuke to undo a storm, it'd have to engulf the whole vortex region out (the bit that's visible as a storm), and this is like hundreds of kilometers in radius. You'd not only wipe out the storm, you'd wipe out the surface of the Earth with the size of the storm, too. Tornadoes are even worse because the supercell where it originated is almost always larger than the size of the destruction made by tornadoes, and the weather trough where the supercells form and goes extends for very long distances and you have to undo it all (it's like trying to undo the whole structure that makes hurricanes possible, ie. from west coast of Africa all the way to the Carribean, albeit much smaller in size).

Edited by YNM
Link to post
Share on other sites

For the off-road crowd:  Why don't we see great big tires/wheels (like HMMWV 37s) on 4WD trucks like the Silverado?  Or, in fact, even larger ones?

It seems to me that if you really want to make an Off Road beast, having large diameter tires would make things a whole lot easier - things like angle of attack, etc. should make a larger tire vehicle more capable than one with smaller tires.  Sure, you can see a dedicated rock crawling Jeep with tires fatter and taller than you get on your Ferrari, but they're not half-again taller than regular truck/Jeep tires.

... and yet, we see Industry keep using 'standard' sizes.  So this tells me there's a physics reason behind it... and google is not helping.

 

Link to post
Share on other sites
3 hours ago, JoeSchmuckatelli said:

For the off-road crowd:  Why don't we see great big tires/wheels (like HMMWV 37s) on 4WD trucks like the Silverado?  Or, in fact, even larger ones?

It seems to me that if you really want to make an Off Road beast, having large diameter tires would make things a whole lot easier - things like angle of attack, etc. should make a larger tire vehicle more capable than one with smaller tires.  Sure, you can see a dedicated rock crawling Jeep with tires fatter and taller than you get on your Ferrari, but they're not half-again taller than regular truck/Jeep tires.

... and yet, we see Industry keep using 'standard' sizes.  So this tells me there's a physics reason behind it... and google is not helping.

Street legality issues and a lack of need I guess also diminishing return. An serious off road car is seriously capable. For something larger I guess 3-4 axles are better. 
For military use you want an low profile.

Link to post
Share on other sites
12 hours ago, JoeSchmuckatelli said:

For the off-road crowd:  Why don't we see great big tires/wheels (like HMMWV 37s) on 4WD trucks like the Silverado?  Or, in fact, even larger ones?

It seems to me that if you really want to make an Off Road beast, having large diameter tires would make things a whole lot easier - things like angle of attack, etc. should make a larger tire vehicle more capable than one with smaller tires.  Sure, you can see a dedicated rock crawling Jeep with tires fatter and taller than you get on your Ferrari, but they're not half-again taller than regular truck/Jeep tires.

... and yet, we see Industry keep using 'standard' sizes.  So this tells me there's a physics reason behind it... and google is not helping.

Well, one problem is the increased leverage of the tire vs your suspension strength. When you start flexing the suspension, going over obstacles, etc, you place leverage on the tire that places excessive force on the axles, wheel bearings, steering gear, ball joints, tie rods, etc. The truck is engineered to withstand those forces at reasonable angles with the stock tire sizes. It can withstand them with slightly larger tire sizes because, well, things are generally over-engineered. But if you start putting really large tires (or really large lifts, or just about anything excessively large out of specification, actually) then you start to get excessive leverage that can easily exceed the strength of the suspension components and cause failures. You can (and some guys do) go ahead and start beefing up other parts in the suspension to try to compensate, but then you're kinda building your own truck from scratch at that point.

And, honestly, there really is a certain lack of need as well. My truck has a 1" lift, with tires that are 1" larger in diameter than stock. (Although when I put the lift and tires on, the truck had 194,000 miles on it, and the original springs were tired and riding about 3/4" low. So the improvement over the then current state was considerable.) But with all the off-roading I do, I have never once had to say, "I have to turn around because my truck can't handle this." I have had to say, "I have to turn around because I don't think any truck can handle this." I've said, "I have to turn around because the National Park Service can't handle this." I've said, "I have to turn around because my wife can't handle this." Multiple times. But I've never felt like I could have kept going and the truck could not. Sure, I could put a 3-4" lift and 37-38" tires on my truck, tub out the wheel wells, chop the fenders, etc, etc. But it isn't going to let me get to anywhere that I can't get to now. It's just going to look expo and cost me an arm and a leg. And, as I outlined above, possibly make my truck less capable.

Link to post
Share on other sites
On 1/10/2021 at 8:55 AM, JoeSchmuckatelli said:

So this tells me there's a physics reason behind it...

There is only the cost of building the brakes,steering, and suspension to handle the new tire size.  The cost of doing it right is too high for most. John Force (NHRA drag racer) once said the only limitation to speed is money. I tend to agree with him on most things in the automotive world.  But also consider nearly everything on a vehicle is a compromise. Going full off road makes for a terrible street vehicle.

Link to post
Share on other sites
1 hour ago, cubinator said:

Will the James Webb telescope sit exactly in Earth's shadow? Or is Earth too small/orbit too wobbly for that?

I think the sun is too big for that.  The L-2 is 1.5 million km away.  The umbra is a cone only about 1.4 million km long.  For reference, the moon is only about 384,000 km, and can be eclipsed.  Further, while they call it a Lagrange 'point' it's really an area of relative stability, so the observatory will still have to do some amount of station keeping to keep from falling out of that region.

 

The Webb has some pretty fancy sun shields on it, for this purpose.

Edited by JoeSchmuckatelli
Link to post
Share on other sites

Does the heat propagation (from hot object to cold object) affected by the temperature difference between the 2 objects? Does the greater the difference means the colder object more "receptive" towards the heat from hotter object? For example:

There's a hot iron rod with a temperature of 100 ºC. The temperature is uniform on the surface of this iron rod. Now we attach 3 iron rods at once (all touching the hot iron rod at the same time), but each of them has different temperature: rod A is at 70 ºC, rod B is at 35 ºC and rod C is at 0 ºC

Does the rod C more "receptive" with heat propagation because of  it's much larger temperature difference with the hot iron rod compared with the other 2? (in other words, rod C is prioritized more for heat flow than rod A and B)

Edited by ARS
Link to post
Share on other sites
19 minutes ago, ARS said:

Does the heat propagation (from hot object to cold object) affected by the temperature difference between the 2 objects? Does the greater the difference means the colder object more "receptive" towards the heat from hotter object? For example:

There's a hot iron rod with a temperature of 100 ºC. The temperature is uniform on the surface of this iron rod. Now we attach 3 iron rods at once (all touching the hot iron rod at the same time), but each of them has different temperature: rod A is at 70 ºC, rod B is at 35 ºC and rod C is at 0 ºC

Does the rod C more "receptive" with heat propagation because of  it's much larger temperature difference with the hot iron rod compared with the other 2? (in other words, rod C is prioritized more for heat flow than rod A and B)

Everything above 0k is emitting heat.

The question is, is it absorbing more heat than it emits.

If it's environment is warmer than it is, then it will generally be absorbing more heat than it emits.

The greater the difference, the greater the difference between what it is emitting and what it is absorbing.

The 0, 35, and 70 degree bars will all receive the same amount of heat from the 100 degree bar, but the 0 degree bar will be emitting less heat, so it's internal temperature will go up faster than the internal temperatures of the other bars.  

This is generally simplified by only looking at the temperature difference between two objects, as most of the heat given to the 70 degree bar is cancelled out by the heat given to the 100 degree bar from the 70 degree bar.

The different types of emission affect the rate(conduction is much faster than radiation, and convection is between them in the rate of transfer), but given enough time, everything that is not generating heat or receiving heat from another source will eventually reach 0K(the heat-death of the universe if not before)

Link to post
Share on other sites
23 hours ago, Terwin said:

Everything above 0k is emitting heat.

The question is, is it absorbing more heat than it emits.

If it's environment is warmer than it is, then it will generally be absorbing more heat than it emits.

The greater the difference, the greater the difference between what it is emitting and what it is absorbing.

The 0, 35, and 70 degree bars will all receive the same amount of heat from the 100 degree bar, but the 0 degree bar will be emitting less heat, so it's internal temperature will go up faster than the internal temperatures of the other bars.  

This is generally simplified by only looking at the temperature difference between two objects, as most of the heat given to the 70 degree bar is cancelled out by the heat given to the 100 degree bar from the 70 degree bar.

The different types of emission affect the rate(conduction is much faster than radiation, and convection is between them in the rate of transfer), but given enough time, everything that is not generating heat or receiving heat from another source will eventually reach 0K(the heat-death of the universe if not before)

Wait - isn't everything touching merely moving toward equilibrium?  The 70 degree bar won't just warm up toward 100, it will also cool the 100 bar down toward 70 (until they both meet in the middle), and just as the heating of the 70 propagates away through the bar from its point of contact with the 100, the cooling of the 100 should propagate from its point of contact with the 70.  If all bars are of the same steel, it should take the same amount of energy to change the 70 degree bar by one degree as it does the 0 degree bar, correct?  And if they're all of the same construction/ density - the propagation of heat change should be at about the same rate, right?

Link to post
Share on other sites
2 minutes ago, JoeSchmuckatelli said:

Wait - isn't everything touching merely moving toward equilibrium?  The 70 degree bar won't just warm up toward 100, it will also cool the 100 bar down toward 70 (until they both meet in the middle), and just as the heating of the 70 propagates away through the bar from its point of contact with the 100, the cooling of the 100 should propagate from its point of contact with the 70.  If all bars are of the same steel, it should take the same amount of energy to change the 70 degree bar by one degree as it does the 0 degree bar, correct?  And if they're all of the same construction/ density - the propagation of heat change should be at about the same rate, right?

The relative rate of heating depends on the relative temperature.

The zero degree bar will warm up faster than the 70 degree bar when both are put in contact with the 100 degree bar, due to the temperature differential.

I was just explaining it from a zero-temp starting point as the OP seemed confused as to why the lower temperature bar would be more 'accepting' of the heat of the higher temperature bar than the moderate temperature bar.(in short, they both get the same, but the lower temp bar gives less back so it heats up faster)

This is why you can freeze water in the desert by using a mirror lined hole that you cover by day and uncover by night.(I understand such holes have been traditionally used in the middle east since long before modern refrigeration)

Link to post
Share on other sites
5 minutes ago, Terwin said:

This is why you can freeze water in the desert by using a mirror lined hole that you cover by day and uncover by night.(I understand such holes have been traditionally used in the middle east since long before modern refrigeration)

Gotta source for this?  First I've ever heard of it, and I'm someone who is fascinated by Qanats!

 

Edited by JoeSchmuckatelli
Link to post
Share on other sites
27 minutes ago, JoeSchmuckatelli said:

Gotta source for this?  First I've ever heard of it, and I'm someone who is fascinated by Qanats!

Google has lots of hits for freezing water in the desert:

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

https://tecped.com/process-of-freezing-ice-in-the-desert-according-to-physicists/#:~:text=The technology called 'night sky,easily change the water temperature.

https://www.quora.com/What-is-the-science-behind-making-ice-in-the-desert

Looks like the technique is old enough to be referenced in the bible even...

Link to post
Share on other sites
22 hours ago, Terwin said:

I've read trough all of them, but I still don't understand how it works. How does something get below ambient without conventional compression and expansion systems?

Link to post
Share on other sites
9 minutes ago, lrd.Helmet said:

I've read trough all of them, but I still don't understand how it works. How does something get below ambient without conventional compression and expansion systems?

I believe evaporative cooling plays a large part, but radiation may play a part as well.

I understand that very dry air(like you find in a desert) has much lower thermal inertia than humid air, so deserts regularly get 'cold' at night, even in the summer, so it may not take much evaporative cooling.

According to NASA, the daily average temperature swing is a good 75f(42c): https://earthobservatory.nasa.gov/biome/biodesert.php#:~:text=During the day%2C desert temperatures,(about 25 degrees fahrenheit).

So baking and freezing on the same day looks like it may be normal.

Link to post
Share on other sites
37 minutes ago, lrd.Helmet said:

I've read trough all of them, but I still don't understand how it works. How does something get below ambient without conventional compression and expansion systems?

My interpretation of what I read suggests they actually transported ice to the Yakhchal during winter, lined the subterranean floor and walls with it and kept it cool via fresh water flowing in from the qanats (that run below ground from meltwater in the mountains) and the passive cooling / ventilation - such that they might still have ice during the summer.

The qanat system of Persia is fascinating.  Throughout that part of the world - in fact extending from Egypt, the Middle East and through Central Asia, folks way back when found very creative ways to deal with the heat and arid conditions.  Check out Wind Catchers Windcatcher - Wikipedia and Evaporative Cooling in the Ancient World  - Quilo - Smart Home Cooling Solutions (quilohome.com)

It's not too different from the ice houses used in the West.

Quote

The ice house was introduced to Britain around 1660. Various types and designs of ice house exist but British ice houses were commonly brick-lined, domed structures, with most of their volume underground. Ice houses varied in design depending on the date and builder, but were usually conical or rounded at the bottom to hold melted ice. They usually had a drain to take away the melt-water. It is recorded that the idea for ice houses was brought to Britain by travellers who had seen similar arrangements in Italy, where peasants collected ice from the mountains and used it to keep food fresh inside caves.[4] Ice houses were also known as ice wells, ice pits or ice mounds. Game larders and venison larders were sometimes marked on Ordnance Survey maps as ice houses. Bruce Walker, an expert on Scottish Vernacular buildings, has suggested that relatively numerous and usually long-ruined ice houses on country estates have led to Scotland's many legends of secret tunnels.[5]

 

Ice house (building) - Wikipedia  .

18 minutes ago, Terwin said:

I believe evaporative cooling plays a large part, but radiation may play a part as well.

I understand that very dry air(like you find in a desert) has much lower thermal inertia than humid air, so deserts regularly get 'cold' at night, even in the summer, so it may not take much evaporative cooling.

According to NASA, the daily average temperature swing is a good 75f(42c): https://earthobservatory.nasa.gov/biome/biodesert.php#:~:text=During the day%2C desert temperatures,(about 25 degrees fahrenheit).

So baking and freezing on the same day looks like it may be normal.

I've lived in several deserts during my lifetime.  The reality of 'cold' in the desert is quite relative.  When you have extremely dry air, the temperature difference between night and day can be stark.  If it's 120 in the sun during the afternoon, you will feel the need for a jacket during the 70 degree night.*  But the fact is, it's still 70 degrees; so while you feel cold, water is not going to freeze. 

The ground temperature is similarly above freezing - so when you described 'a mirror lined hole' freezing water, I was curious.  If you have support for this - I would really like to see it.  However what you linked above comports more with what I describe in my previous post about transported ice being kept relatively cool via passive cooling, as opposed to ice being generated within a structure attached to a qanat.

 

 

* I've seen folks really shivering hard at night, even acting a bit hypothermic, in the 'cold' desert air after a hot day filled with exertion.  Despite the fact that the same guy who was 'freezing' at 70 degree air temps in the summer, would be happily outside in shorts were it winter.

Edited by JoeSchmuckatelli
Link to post
Share on other sites
20 minutes ago, JoeSchmuckatelli said:

I've lived in several deserts during my lifetime.  The reality of 'cold' in the desert is quite relative.  When you have extremely dry air, the temperature difference between night and day can be stark.  If it's 120 in the sun during the afternoon, you will feel the need for a jacket during the 70 degree night.*  But the fact is, it's still 70 degrees; so while you feel cold, water is not going to freeze. 

The ground temperature is similarly above freezing - so when you described 'a mirror lined hole' freezing water, I was curious.  If you have support for this - I would really like to see it.  However what you linked above comports more with what I describe in my previous post about transported ice being kept relatively cool via passive cooling, as opposed to ice being generated within a structure attached to a qanat.

This link says nothing about mirrors, but says 'night sky cooling' can cause the surface of water to freeze in specially designed troughs with ambient temperatures as high as 41f:

https://www.realclearscience.com/blog/2018/07/09/how_people_created_ice_in_the_desert_2000_years_ago.html

Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

×
×
  • Create New...