pavelcherepan

21 hours ago, Eise said:

There is no way to solve the question if electric fields just seem to be real or are real

As MigL has correctly pointed, there is another way of looking at it. Is it likely that our understanding of space-time or electric fields will change significantly in time?

Since electromagnetism or GR are both theories, we are meant to update and change those if conflicting evidence shows up. Therefore, our understanding of what those phenomena are can, and most likely will change over time. New theories based on new observations can show it in completely different light. At the same time observable effects of space and time or electric fields, or electrons, will still stay the same. Therefore, I would consider those as 'real', but any theory or model can only be 'real' at one particular point in time.

9 hours ago, beecee said:

I'm not sure if those statements are correct. Why don't we ask ourselves is a magnetic field real?

Feynman famously said the following about electron:

Quote

The electron is a theory we use; it is so useful in understanding the way nature works that we can almost call it real.

So by following his line of thought - electromagnetic field is a theory, so long as it conforms to what we expect of it, we can consider magnetic field to be almost real. But in the real world that we can experience what's real are charged particles moving along predictable routes and other effects.

Otherwise, magnetic field is just a matrix describing strength of magnetic force in any given point in space. Can't bring myself to think of it as being 'real'.

10 hours ago, MigL said:

A single particle can decay immediately today, yet repeat the same experiment tomorrow and it can take ten years for a like particle to decay.
And since it can be different every time, a single particle's behaviour is not time dependent.

Are they 'like' particles or different if they have different lifetimes? On a statistical level we can group them together and have a half-life defined that on a statistical level particles conform to, but if you look at them in separation, they are different, because they have different lifetimes. 

1 hour ago, Markus Hanke said:

First of all, distance does not require any “objects”, I do not see any issue defining separations between points in a completely empty space.

What you describe is an abstraction, just as @Eise said in his/her comment. Just like any mathematical abstract solution - your calculations may be self-consistent, but you can't apply those to the real physical world without introducing objects.

1 hour ago, Markus Hanke said:

As for time, consider an elementary particle with a finite lifetime - while it is in existence, there is no notion of “change”, since it is elementary without any internal structure or mechanisms. Yet there clearly is some notion of time here, because otherwise it would not end up eventually decaying.

Well, the 'change' for this particle would be becoming a completely different particle via decay. If said particle is not the only one in the universe, 'change' would involve interactions with other particles.

On the other hand, your comment brought me onto something: imagine a universe with same physics laws as ours but populated by only one photon. Photons don't experience time and there will be no interactions with anything else. Would such a universe have a notion of time, or space for that matter too?

Well, if maximum intensity is zero, it seems like there's definitely something wrong with your data. Can you look at it in plain text? Can you see any responses whatsoever? 

On 7/12/2018 at 12:39 AM, thecynicalmonk said:

But how would hydrologists tackle the enormous task of getting rid of ocean floodwater in these circumstances? If a hydrologist were charged with removing floodwater in an entire city, or even an entire affected coastline, are there any methods available to achieve this apart from the kind of land reclamation systems used in Holland? 

I would say, it's hard to 'remove' the floodwater as long as the source of it is still present. You'd first need to build a dam of some description to stop new water coming in, and only then will you think about pumping the water out or you could dig canals to drain water to lower-lying area.

On 6/15/2018 at 3:45 PM, dstebbins said:

Now, the frozen part makes perfect sense. But why the poles? Why that location in particular that caused the water to gravitate towards it?

Even despite the very low temperatures on the surface of Mars, the lack or atmospheric pressure still allows for frozen water to slowly sublimate. Once in gaseous form and with Mars lacking magnetic field, water molecules get destroyed by electromagnetic radiation and then free oxygen and hydrogen easily escape martian gravity. Earth has been losing water due to this, albeit much slower.

At the poles, temperatures are much lower, so sublimation doesn't go as fast and also ice there gets covered by seasonal CO2 ice caps (and dust as well). This reduces the exposure to the direct sunlight and further reduces the sublimation rate. 

On 6/30/2018 at 12:31 PM, Anopsology said:

Not the exact temperature but.. I've been wondering

If these springs are produced by groundwater sources then the temperature of the water in them should be roughly equal to the year-round average temperature for the particular area. This is a handy trick in climate science, where instead of constantly measuring temperature to find averages, you can just measure groundwater temperature and it will give you a very close result with only minor changes with seasons. This is due to thermal insulation provided by overlying rock formations. 

But then you can go other way around - if you know year-round average temperature for your area, you can predict what temperature ground water would be. For example, in Southern-Central Europe during the last ice-age, you'd probably be looking at somewhere between 2 and 5 degrees C year-round temperatures, so spring water Neanderthals and Cro-Magnons drank was probably quite chill. 

On 7/11/2018 at 8:42 AM, Moontanman said:

On Earth it is thought in some circles that plate tectonics occurs on Earth due to the interaction of water making subduction easier if not the key to making it happen. This results in various minerals like granite which make up large portions of the Earth's continents and cannot occur without the interaction of magma and water. What role does being exposed to an atmosphere have in this? Would a world with no dry land have plate tectonics and or rocks like granite? 

Overall, there is no reason not to have plate tectonics on a water world. Tectonics is assisted by presence of water, but is driven mostly by variations in density of material and mantle material convection. At the same time there are no definite signs of plate tectonics in any other rocky bodies of the solar system and there is no dominant theory of it's origins on Earth (the based on current knowledge the planet did exist for almost a billion years without it). 

As far as granite is concerned, I don't think presence of water is truly required for it to occur. Water can help it in subduction zones as it considerably reduces the melting temperature, but it's not essential. 

4 minutes ago, DrP said:

Maybe you could say it was perpendicular to the circumference at the point it meets it?   

Yeah, that was what I was going for. Is that the case?

25 minutes ago, DrP said:

It doesn't connect to the perimeter. It is perpendicular to the plane of the circle through the centre.

Sorry, I don't follow. Could you elaborate please?

5 minutes ago, LaurieAG said:

An axle is perpendicular to the plane of a circular wheel but it is not quite a radius.

Why is the axle not quite radius if it does connect the center of a circle to its perimeter?

Hi everyone! Stupid question in the topic. Obviously, radius is perpendicular to a tangent at a point of intersection, but can it be said that radius is perpendicular to the circle itself? Does such statement even make sense?

I'm not great at maths, but it seems like you can express sum of factorials as an integral and then I guess, you can just go with sum rule in integration. Not sure what you do afterwards, though. Good luck anyway.

On 3/21/2018 at 7:38 PM, Strange said:

Influenza is a disease of humans.

Nit-picking, but this is not correct.

https://en.wikipedia.org/wiki/Influenza#Other_animals

21 minutes ago, Ten oz said:

He has been arrested for protests and rallies:

But that's not what ultimately dismissed him from running for president.

6 minutes ago, MigL said:

Google 'V Putin net worth' to see how many credible sources you get ( and not one Daily Mail ).

Well, I'm reading and seeing things like:

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Bill Browder, a former fund manager in Russia and major critic of Putin, estimated the president's net worth at $200 billion,

On the other hand:

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Forbes, the premier chronicler of the world’s wealthiest, doesn’t include Putin on its list of billionaires. In 2015, the magazine said it couldn’t verify enough assets.

Forbes is a very credible source for wealth figures so if they can't verify assets, this argument is not very solid. I don't doubt that in ~20 years in various high offices Putin did make a nice chunk of money, but $200 billion? Such wealth would be really hard to hide.

12 minutes ago, Sensei said:

Fear of nationalist uprising.. I should better not comment..

Well, maybe not an uprising, but it would be a political suicide. If any president gave Crimea back to Ukraine, they most certainly wouldn't be re-elected. Most Russians consider and have always considered Crimea to be an inherent part of Russia, it would be really hard to convince them otherwise.

Would sanctions be lifted? Possibly. But how long would that take? US lifted cold-war era trade restriction (Jackson-Vanek amendment) over twenty years after dissolution of USSR.  No reason to assume that largely anti-Russia senate would go and lift sanctions immediately, but people would want immediate positive outcomes if Crimea was ceased.

7 minutes ago, MigL said:

I find that laughable, since the 'orchestrator' of his conviction, V Putin, has used the office of Presidency to make himself the reputed richest man in the world, with an estimated net worth of 200 Billion dollars.

It's really hard to prove that, unless you want to use a tabloid such as Daily Mail as a reputable source.

28 minutes ago, Sensei said:

He would not attack Crimea, nor attack Donetsk nor Lugansk.. There would be no sanctions (and counter-sanctions, restrictions on food import)...

It already happened... Had Navalny withdrawn from Crimea, there might be an uprising. Overall, people are extremely supportive of taking back Crimea, or whatever else you wish to call it.

22 minutes ago, Ten oz said:

The justice system wasn't acting in Putin's interest?

I said "technically". By constitution, Justice is an independent branch of Russian government.

22 minutes ago, Ten oz said:

Navalny has been arrested multiple times for holding rallies and protests,

False. He's been arrested and tried for business fraud.

1 hour ago, Ten oz said:

What part of the McCain quote do you think is uncalled for?

There's a difference between "denying right to vote in a free and fair election" and having a free and fair election that you're certain to win. Technically speaking, it was not Putin who denied Navalny a right to go for president, but Justice system and constitution.

1 hour ago, Strange said:

I didn't know that. (I had provisionally guessed Polish possibly, just based on "Pavel". Sorry about that!)

Oh, no worries, I have Russian/Ukrainian/Polish roots.

1 hour ago, Strange said:

It seems odd that this doesn't seem to cause very much criticism within Russia. It seems to be just accepted as more evidence of his strength.

Well, historically, Russians do love a strong hand, but more than that after decades of turmoil, Russians love stability. Had someone like Navalny come to power, there would be drastic changes and no one is certain it would be for the better.

45 minutes ago, Sensei said:

Better drunkard, than murderer....

Not sure which country you're from but few presidents/PMs of major countries don't have blood on their hands.

Well, that last quote is a bit uncalled for. I'm Russian and I was very certain that the result would be as we saw. I didn't vote myself, I was in the middle of nowhere and couldn't get to Melbourne in time to cast my vote, but for the lack of better options, and "against all" option for that matter, I guess I'd vote for Putin as well.

Thing is that Putin didn't really have any opponents worthy of mention. I know a lot of people in Russia, who support Navalny and would vote for him, but he was not allowed to run for president. This is one of Putin's strengths, he's very good at getting rid of anyone who might challenge his authority and as a result has no need to forge election results, even though, if need be, he could.

There are some other politicians in Russia who are held in very high regard in public opinion and could be worthy contenders, namely the Foreign Minister Sergey Lavrov and the current Defense Minister Sergey Shoigu. Both of Sergeys are very popular; Lavrov is held in high esteem for his intelligence and pro-Russia political views, even if not as nationalist as Putin is. Shoigu was for a long time Emergency Services minister and was highly popular in this role and in the current role also gets a lot of pro points from Russia's involvement in Syria among others. 

Thing is, though, the reason these two are successful government officials is that they know their place. They will not challenge their boss, even though they could put up a good fight. I would certainly vote for Lavrov, had he gone for president. Maybe they will go for the next presidency, when Putin won't be able to enter the lists. We'' have to wait and see... six more years.

Can't remember who said it, but the quote goes something like - "Here in US we had many bad presidents, but when it happened we sort of just waited for them to not be our president any more". In essence, that's the state of things in Russia nowadays. Mind you, Putin is not the worst it could be, we could have another drunk for a president.

On 3/20/2018 at 4:59 PM, Jack Zalesskiy said:

Since in nature, everything is connected to everything I can imagine that one requires tremendous amounts of data for the research to see how much individual events may affect the changes in populations, habitats or biomes.

As Area54 pointed, science theories usually look into a small subset of data, that's why we have a very old physics joke about "spherical chickens in vacuum".  Also for many complex systems (or even relatively simple like 3-body problem) there are no analytical solutions, but only numerical models, and the more conditions you take to describe the system, the higher the computing power required to model such system, which grows exponentially with each new condition. So I'd say it's not that we don't have enough data, it's finding a way to model ecosystems with all the data we currently have available. Hopefully, developments in quantum computing will help.

3 hours ago, Bender said:

The arguments presented are easily countered by the fact that cattle eats lots of crops, and growing those crops takes land that could otherwise be nature.

...which in turn is easily countered by saying that removal of meat will require turning large if not all of that pasture land to grow monocultures. Also, the largest amount of pasture land are used by "free range" cattle, sheep, etc., which is much closer to the "nature" than, say, a corn field. The biggest change these areas experience is removal of most of trees to improve grass growth with usually no herbicides/pesticides and other chemicals being used on regular basis. On the other hand, animals being produced in confined enclosure, such as most pork, take very little space for a very large calorific output and very efficient use of space.

It seems like the best course of action would be to make "free range" meat produce illegal.

On 3/12/2018 at 8:03 AM, TakenItSeriously said:

transponder is pinging 3 times per second

I'm confused about this part the most. If the transponder on the Earth is pinging at 1 Hz, the twin on the ship in his own FoR should experience 1 ping per second, although at a higher frequency than the source due to blue shift. Why would the ship twin actually experience time as going 3x faster?

1 hour ago, StringJunky said:

4 years feels about right and if they have a meaningful policy they'll likely get 2 or 3 terms to try and see it through. If it's too long they might get stagnant and complacent.

I would agree if results of elections were in any way related to the policies a candidate is proposing, but as we have clearly seen in last US elections, policy plays very little role in the final result. It's usually just populist promises by accomplished demagogues which in most cases never get fulfilled.

Say we have a very capable leader, who is looking at a long-term scenario, which includes making some sacrifices in short term. This leader essentially has 2.5 years to set these plans in motion, because come election time they can get another Trump as main opponent with little policy ideas, but great skills of raising popular support. As a result all the good ideas can be abandoned.

Wouldn't it be better, for example, for the president/PM to be elected for, say, 8 years and mid-way through the term, people would have a vote of confidence, with no actual opposition. If president loses the vote, proper election starts. 

I was just wondering what you guys think about the duration of presidency or prime minister term. Is it adequate? 

Say, with 4-year term in US and many other countries, when a new leader comes to the office it takes time to get a grasp on things and form the government, say it takes 6 months. Then at 3-year mark the next presidency campaign kicks off and now they are distracted from actually trying to do their thing and instead have to appease the public, travel all around the country and defend themselves against the attack of political opponents (or go on attack of their own). That leaves something like 2.5 years out of 4 to actually try and govern the country and implement whatever plans they had before entering the office. Seems like a lot of time being wasted on other things.