Ships that existed before thug boats would not be considered large today, you could pull them with smaller boats that people rowed or buy using ropes to land or to an anchor that was stopped by a smaller boat.

The option that was commonly used was to drop anchor and load and unload via smaller bots and barges.

The fest steam-powered tug boat was made in 1801. If you look at the war ships of the Napoleonic war more specifically the Battle of Trafalgar HMS Victory, Lord Nelsons' flagship was one of the largest in the British fleet. It was 69 meters long and 16 meters wide and has a 3,500 tons displacement. The vast majority of ships om that fleet or in general was not that larg.

The largest passenger ship in 1831 was SS Royal William at 1,370 ton and 49 meters long.

In 1901 it was RMS Celtic at 20,904 ton and 214 meters.

Today it is Wonder of the Seas 236,857 ton and 362 meters.

All of these ships are after the invention of the steam-powered tugboat. So with today standard that war not large ships before tugboats.

It is because it is energy dense. Technically that is why it tastes good, what makes is taste good is the way it stimulates taste buds, the sensor of smell, and another sensory system, and our brains iteration of that stimuli

Humans and our ancestors have evolved in an environment where starvation and not getting overweight have been the primary cause of harm to use.

The one that likes and therefore preferred to eat and look for energy-dense food has a low risk of dying of starvation. So they passed on their genres to their decadence. Over time the taste becomes that we liked energy densed stuff.

It is in the 19th century that you had food manufacturing and cost in combination with changes in what we do for work that has resulted in being overweight is a problem for a large number of people in the developed world. But even today for the majority of humans starvation is still of more concern. So there have not been enough time of any change away from linking energy-dense food.

It is a legal requirement.

If you are a scammer there is another reason, If you us it they do know what mail address it it is from so they knew it is an account that is used and someone did read the mail and it did not just end up in a spam filter.

So they can validate that it is an account that is in use and it the address could be used for som phishing attack or just spam.

Not really. The has been a lion in Greece and the Balkans up to Hungary and Ukraine. The last one survives in part of Greece until 4th century AD.

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Northern Europe has quite recently been covered with ice and human migration has followed the retreat of the ice. The large ice cover had its largest extent 20 000 years ago when it ended in northern Germany.

The lynx is the largest feline, wolf, and bears are the largest predators.

Exactly what life was there before the last ice age is unknown. A kilometer-thick layer of ice even smooths out the bedrock so there is no evidence of what lived in Scandinavia before the ice retreated. That is lived recently before it, there is evidence od what lived millions of a year ago in for example sandstone formations.

A flame is the result of combustion and it needs a fuel and an oxidizer.

The oxidizer is usually oxygen and there the atmosphere is 21% oxygen.

The rest of the atmosphere 78% nitrogen 1% argon and 0.04% other gases. Neither nitrogen or argon can be the fuel and burn with oxygen.

If we list the other gases in how common the are until we get one that can burn: Carbon dioxide, Neon, Helium and Methane.

Methane is the most common gas in the atmosphere that works as a fuel and its concentration is 0.000187% That is simply not enough to sustain combustion and even if it was possible you only use need a bit less the 2/3x the amount of oxygen. The result is 0.0005% of all atmospheric oxygen will be used up when all methane has combusted.

How can you train for anything then? How do people play for any sports when training is not for real?

You need to learn how to handle your equipment, cooperate with others, and what tactics you should use. You need to learn that before real combat because if you do not know how to do it when you are not afraid you will for certain not know that when you are afraid.

If you do something it is second nature to you then you have a better chance to do it if you are afraid because you do not need to think about that. If you have learned to drive a car compared to how it was the first time you were in it compared to when you know how to drive. If you were in a car chase or another high-stress situation would you be better now than when you started to drive? The answer is you are better when you can use the equipment without thinking about it and the reduced amount of thinking you can do can be for the larger stuff like where should you turn not thinking about how to apply the gas, break, and turn the steering wheels.

Military war games are primarily what you call large-scale exercises they can be just on paper or with just communication between units commander and not everyone out on the fire, The can be with everyone out there too. It is not what individuals do in combat that is the most important but coordination and movement and cooperation between units.

How do you handle moments of there is a limited number of roads? How you maintain vehicles in the field, will break down even in training. How do you make sure units get fuel, ammunition, and anything else you need? Is the communication system working and a forward observer can get artillery support?

How do you coordinate so multiple units attack at the same time and maneuver to support each other?

Making sure everything that is not just individual soldiers fighting is extremely important. If your tanks do not get the fuel they quiclty end up as stationary metal boxes that do not have any electrical power and the only way to fire the gun is to manually crank it around. The ballistic computer and thermal sight will no longer work. The practical effect of a tank with no fuel is as if the tank was not there or destroyed.

It is a cooperation between units and logistics that you train in war games not primarily how individual soldiers do the fighting, that is something they should already know.

When you train troops both on the small and large scale you can use https://en.wikipedia.org/wiki/Multiple_integrated_laser_engagement_system or a similar system to simulate compart by fire lasers that vests on individual soldiers or system on vehicles detect. So you can get "killed" and it out of the fight temporarily.

People like to win and fake combat like that will be stressful even if you are not risking your life. Play paintball, Laser tag, or something similar and you will notice stress and the will not to be hit even if it is all just a game.

If you and your fellow soldiers can do what you should do first with no opponent and then with an opponent that does not kill you for real but take you out of the fight you have a lot better chance of doing that for real compared if you did not training.

Bullets fly in arches, they are pulled down by gravity. If you would fire a bullet horizontally over a flat surface and at the same time drop now from the same elevation it will hit the ground at the same time.

the result is the scope does not look parallel to the barrel, the barrel will point slightly upwards if you aim horizontally. It looks like https://qph.cf2.quoracdn.net/main-qimg-20f8f9b2aa7051df653d04e40e2233c2.webp The image uses rear and from irons sight, a scope will create a line of sight the same direction as an iron sight

You zero a sight so the bullet trajectory and the line of sight are at a specific distance. Sight for rifles usually have an adjustable rate setting that is calibrated for the rifles and ammunition so the line of sight is changing relative to the barrel the correct amount so they intersect at the new distance.

So if you zero the rifle with so, for example, the 100-meter setting hits the line of sight at 100 meters when you then change the setting to 200m the bullet should hit the line of sight too. If the range is incorrect the bullet will hit above or below where you are.

If you can hold a weapon vertically all the time the distance the optics are above the barrel does not matter for accuracy. If you need to turn the weapons sideways it is better if you have them closer to the barrel but that is something that is more likely you need to do with assault rifles than sniper rifles.

The main problem with a large offset is to avoid hitting something just in front of the barrel. If you are on the uneven ground something could be in front of the barrel but not in front of the sight. Lay down on the uneven ground and try to expose your body as little as possible to enemy fire then you risk just seeing over some dirt that is directly in front of the muzzle. This is the

the amount of oxygen we have used is minuscule compared to the amount in the atmosphere.

The mass of the atmosphere is about 5.5 quadrillion tons and 20% of that is oxygen.

You need to remember that it is only if we use it with carbon that is not part of the carbon cycle on earth that it is a net increase. So if we burn a tree for fuel and then a new tree grows up and replaces it the same amount of oxygen is released from it photosynthesis.

So it it primary fossil fuels from the ground that use up oxygen and produce CO2. The amount of CO2 is today 412 PPM an increase by 47% from the preindustrial age. let's say 200PPM.

1 PPM =0.0001% so an increase be 0.02%. Compare that to the atmospheric oxygen level of 20.95%. The result is we have used around 1/1000 of the oxygen in the atmosphere since the start of the industrial revolution

The asteroid belt is not like in movies. The average distance between objects is about 1 million km, a bit less the 3x the distance to the moon. If you were on an asteroid it is extremely unlikely you could see another with your naked eye.

If you could see another astroid you are likely to be close to one of the four larger asteroids Ceres, Vesta, Pallas, and Hygiea, they contain 60% of the total mass of the asteroid belt. The total mass of the asteroid belt is about 3% of the mass of the moon.

We do know where the planes in the solar system are and it was because of how they lined up that Voyager I and II were launched.

Voyager, I did flybys of Jupiter and Saturn and exploited their gravitational field to do a gravity boost and increase the speed.

Voyager II did flybys if Jupiter, Saturn, Uranus, and Neptune.

Both have thrusters that were used for small maneuvers so the flyby was exactly as what desired.

There are no unknown objects in the solar system that has enough gravity to capture an object that moves at the speed of the probers.

It it what they encounter in thousand, million or billion of year that is not exactly known

They did not build bridges over "deep and/or dangerous water" before diving equipment existed. That is bridges with support in the water. Rope bridges and other simple suspension bridges have been built over rapids if the distances were short enough.

If it is even shorter you can build a solid bridge that is just supported by the ground on the sides of the river.

In relatively shallow and nice water you do not need to go underwater you can still expose the bottom.

The simplest way to explain this is by building an alternative path for the water and then making a dam with dirt and rock in the river. The old river bed is now dry and you can work on it. Destroy the dam and fill in the digestion and you have a bridge. It might not be the simple thing to do for a large river but it was possible.

You do not need to do that for all of the river, build a cofferdam that encloses parts of the river remove the water from the side and you can work there. The wall of the dame can be large baskets you fill with rocks and dirt to keep the water, coffer is an old word for the base.

Or build a small coffer dam by driving wooden pillars into the river bottom to remove the water. It only needs to be just larger than the pillar you intend to build to support the bridge. This is still common we just use metal walls bridges and other stuff that need access to a river bed.

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

Another way is driving a wooden pillar into the bottom with a pile driver and letting that support a wooden bridge that extends a bit out in the air so you can drive down more wooden pillars. Ceasar's army built bridges like that over the Rhine River in 10 days. It looked something like

https://c8.alamy.com/comp/BA805M/architecture-bridges-roman-bridge-of-gaius-iulius-caesar-over-the-BA805M.jpg

https://en.wikipedia.org/wiki/Caesar%27s_Rhine_bridges

So they built bridges over rivers with support in the river since ancient times but it was not very deep or dangerous water where it was done. It was quite shallow

We do not know that, just that it will ake a very long time before it could because of the enormous distances.

Voyager, I do orbit something, the core of the galaxy just like the solar system. It is the combined effect of all matter in the solar syst.

>But for wireless speakers, the wireless signal does not transfert energy.

It does transfer energy is just not enough to power the amplifier or to directly drive the membrane.

RFID is an example of short-distance radio communication where the signal powers the tag. Contactless payment with credit and debit card use RFID to power chips that do encryption to make it safe.

You could have a transmission on one to power the headphones it would just be very wasteful of the phone battery. There is an audio transmission system that can and just that. You can build a crystal radio to receive AM radio and it does not need any power source.

>We have named a year to be the time it takes for 1 orbit of the sun.

That is not the case. The year we base our calendar on is the one cycle in the season on earth. You can pick the time between March Equinox and next March Equinox. This is a tropical year

It is it and the average solar day we try to make a calendar from. because there is not an integer fraction between the you need to add leap years

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An obit around the sun relative to a star far away is a sidereal year. It differs from the tropical year by around 20 minutes. It adds up to around 1 day of change in 72 years so not a lot but very relevant if you, for example, do celestial navigation.

Over a long time it has a larger effect, Compare the day that typically zodiac and when the sun really is in the sky, there is a difference of around 20 days because of the 20 minutes difference over more than millennia.

That is in large part the origin of new papers. The was primarily started by rich people or groups to give a voice to their political ideas. So most of them did not end up like that, most were intentionally started with that idea in mind.

The max theoretical efficiency for photosynthesis is 4.6% for C3 and 6% C4 plants, that is of incoming sunlight.

Cheap solar panels, the type used for example on building roofs have a practical efficiency of around 20%. The most efficient but a lot more efficient are 47% efficient, they are used on for example satellites. The max theoretical efficiency is 86%

So we have already lowe cost solar panels that are over 3x as efficient as the theoretical efficiency for plants. Copying photosynthesis is not a good idea for efficiency because we already have more efficient technology.

Plants have the advantage the grow from seeds and do not need to be made in a factory. They also produce sugar chains that are stable molecules we can extra energy from later. There is no need to copy plants we can just use plants and harvest them as an energy resource.

Energy forestry is something that is done. Humans have done it for centuries by letting trees grow used for firewood.

A kilogram is a unit of mass. Just read the definition of it

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>"The kilogram, symbol kg, is the SI unit of mass. It is defined by taking the fixed numerical value of the Planck constant h to be 6.62607015×10−34 when expressed in the unit J s, which is equal to kg m2 s−1, where the metre and the second are defined in terms of c and ∆νCs."[1]

The SI unit of force a 1Newton that in SI base unit is 1 kilogram meter / second ^2

Underwing versus on the back is not the same as why one on the vertical stabilizer or just the air intake there

If you have an odd number of engines you need to place one in the center line of the airplane and with a jet engine, you can put it in the front line with propellers.

You can but even the number of engines under the wing or on the body. 4 engines on the back have them placed side by side like a Vickers VC10

3 engines existed primarily because of ETOPS rating, you could fly longer over open water with 3 compared to 2 engines and the cost will be less than if you have 4 engines. A minor part is that it adds high-altitude takeoff performance in locations like Colorado which is at 1-mile altitude.

They have disappeared because engine performance and ETOPS regulations have changed so you are allowed to do the same flight with just 2 engines and it is a cheaper way to build and operate aircraft

Boeing 727 have all 3 engine in the rear, and McDonnell Douglas MD-11 had 2 under the wings and 1 in the back. So 2 engines under the wings or on the back are unrelated to the vertical stabilizer position of a third engine.

In science, a hypothesis is a proposed explanation for a phenomenon. That would be what you in everyday language likely call a theory.

A Scientific theory is to quote the beginning of https://en.wikipedia.org/wiki/Scientific_theory

>A scientific theory is an explanation of an aspect of the natural world and universe that has been repeatedly tested and corroborated in accordance with the scientific method, using accepted protocols of observation, measurement, and evaluation of results.

So in the 19th century, what caused diseases was not really known. That bacteria is what causes infection was not known, So you might have the hypothesis that bacteria is what caused the infection. After expiration and test like what https://en.wikipedia.org/wiki/Robert_Koch did that shows that bacteria it the cause of many diseases.

The result is what is called https://en.wikipedia.org/wiki/Germ_theory_of_disease that germs can cause diseases. It is not just bacteria and another living thing like fungi( for example mold), protists (for example amoebas) etc. It can alos be no loving thing like viruses, prions, viroids etc.

So everything about how germs cause disease is a theory. The hypothesis was the idea before it was tested and shown to match reality.

That do not mean that all diseases are because of germ, it can be your own cells that do not work as they should. Autoimmune disease is for example your own immune system attaching your own tissue.

Before that https://en.wikipedia.org/wiki/Miasma_theory obsolete medical theory, that bad air causes disease, so it was the smell that could cause it. It was proposed as early as 4th century BC by Hippocrates. If you look at https://en.wikipedia.org/wiki/Plague_doctor with masks with beaks that contain dried flowers, herbs, and other things to keep the smells away. It likely helped because it keep droplets with bacteria away just like the facemask that is used today but the smell was not the cause.

The name malaria if from Italia where "mal" is bad and "aria" is air, so the literary means bad air. It was believed that the smell in for example wetlands caused it, the real explanation is that is a parasite that is transferred by mosquitos. So it did not smell but the existence of mosquitos in some areas caused it.

So both are explanations of a phenomenon Miasma theory was believed in for centuries even if it was not correct. But getting rid of smells can also reduce exposure to germs, so in a way it worked but why it works was not correct.

>It may vary with location, but in the USA the lowest wifi frequency is 2.4GHz, and the highest cell frequency is 2.2GHz

That is not true. Look at https://en.wikipedia.org/wiki/Cellular_frequencies_in_the_United_States there cellular communication in use at 39GHz.

Voltage is originally not created using in the KMS system with kilo, meter, and second but a unit in the CGS system that has the base in centimeters, gram, and second. That were the customary units in science when the field was created.

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It is when International Electrical Congress (IEC) defined the unit in 1881 it was scaled up for the voltage in the MKS system, International Electrical Congress become International Electrotechnical Commission in 1906 still called IEC, and is still a standard organization for that field.

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So it is units that were very quickly defined within the international agreement before any large-scale adaptation.

This also shows there is no metric system, there are many metric systems. MTS(meter-tonne-second) was used industrially in France and the soviet union in the first half of this century.

What is commonly used today is the SI system which is A metric system, not THE metric system.

The CGS system is still used in for example magnetism. The usage have decreased with MKS standards in 1940 and the SI standards in the 1960s. It has been used longer in theoretical sciences compared to practical engineering.

You can steal and make a copy of the HTML and other code that is delivered to the web browser. If only that is stored on the web server you can make a copy of the website, at least all of it you have access too. If you need to log in what you have access to often is in part specific for you. You can access for example access my Reddit chats

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The problem is most website is not made by just static HTML files stored on a web server. Reddit, for example, uses phyton code that is executed on the server, and it access databases with all the post, comment, user preferences, etc that are used to create the HTML pages you get and your browser display right now. The website does not give you direct access to the phyton code or the database when you browse the website.

So making an exact copy is not as easy as it first looks like.

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Nothing says the code that generates the website can be published too, you do not need to but it looks like at least part of Reddit is available at https://github.com/reddit I am not sure what is included and if it is complete or not. But I doubt that Reddit provides a public copy of the database.

Imaginary number exit because we define them to exit. Maths is an internally consistent system that is based on a few unprovable axioms..

So we define the imaginary unit i as i^2 = -1 and the rest of the usage follows from that definition

If you look at the abundance of elements in earth's crust aluminum is #3. It we use the CRC number from https://en.wikipedia.org/wiki/Abundance_of_elements_in_Earth%27s_crust we have

• Oxygen 46%
• Silicon 28%
• Aluminium 8.2%
• Iron 5.6%

So there is an enormous amount of aluminum. Most of it we use are in the for mof bauxite that is aluminum o

Aluminum is also recycled to a high degree. The primary reason is not the availability of bauxite ore. The primary reason is that the energy required to of recycling is 5% of the energy required to make it from ore. Aluminum requires a huge amount of electric energy to refine.

36% of the aluminum produced in the US comes from scrap. Globally the recycling rate is around 76% and it is estimated that 75% of all aluminum ever produced is still in usage.

>The Taliban did the same to Al Quaeda and the US definitely did consider material support an act of war, and retaliated in kind.

That is not exactly what happened. The US demanded that the Taliban movement would extradite Osama bin Laden and other suspected terrorists. They also demanded that Al Quaeda bases and training camps should be shut down. That did not happen and the result was the invasion.

If they would have done that I doubt there would have been in invasion

>Thanks, I think this is starting to make sense. So when the car changes speed, it's applying work against the ground/earth and that's the frame of reference? I think that's what I was missing

The frame of reference is just what you define as being stationary for your calculations. It is something that just exists in the model you use for the calculation.

The speedometer of the car measures the speed of the car relative to what is rolling on. Let's assume that it is a day with no wind. let's say the speedometer shows 120, the unit does not matter, that is the relative speed between the car and the ground.

So you can use the ground as the frame of reference then the car moves forward at 120 or you can use the car then the ground and the air move backward at 120. So any calculation you do need to include both parts

So the situation is like if you drive a remote-controlled toy car on a treadmill and add a fan to get the air moving. Compare that car to a remote-controlled car on the floor beside it. From the behavior, it is quite clear that the moment of the treadmill has an effect on the behavior of the car.

So if you use a car that is more relative to the earth as the frame of reference you need to include that earth is moving backward just like if you drive on a treadmill and the frame of reference is the ground you need to include the motion of the band on the treadmill

For spacecraft or any other rocket engine, the propellant is moving at the same speed as it. They will both have the same speed regardless of what frame of reference is used. What speed at both moves depends on the frame of reference you use but it will always be the same.

The result is it works out the same regardless of what framer of reference you use, what can change it how hard the calculation is