I wonder if any of the more scientifically minded people on here could help me, please.

[Horsa]

Wow! Wasn't even aware of that, thanks for the info contained on the question, Horsa. I could guess something here and there but that is all is quite out of my scope actually.

I'm always hearing about geophysics when watching archaeology programmes. You're welcome, Mrzz. Other than the information I gave in the question & the fact that the archaeologists dig where the geophysics survey shows the man-made structures are to save time & find more artefacts quicker, I've no idea. You've more idea than me though I guess I could look & see if I could find out for myself something that more-or-less answers the question or a similar question like I did on the longevity questions.

 

[Horsa]

Wow! I'm amazed. I didn't realise that geophysics could be helpful in so many ways.
https://www.eegs.org/what-is-geophysics-
http://www.tv.com/shows/time-team/season-1/ I used to watch this T.V. programme every week. You should see the geophysicists doing a geophysical survey of the archaeological site on here before the location of trenches is decided on & the geophysical machine & geophysics print-out. I miss this T.V. programme. I even wrote a poem asking the T.V. company to bring it back. I hope you enjoy.

 

[Horsa]

I'm very sorry for doing your head in by asking lots of questions, guys. I just wondered & thought other people might be interested in the answers too, that's all.

 

[Chris Koziarz]

Wow! I'm amazed. I didn't realise that geophysics could be helpful in so many ways.
https://www.eegs.org/what-is-geophysics-
http://www.tv.com/shows/time-team/season-1/ I used to watch this T.V. programme every week. You should see the geophysicists doing a geophysical survey of the archaeological site on here before the location of trenches is decided on & the geophysical machine & geophysics print-out. I miss this T.V. programme. I even wrote a poem asking the T.V. company to bring it back. I hope you enjoy.

I've read one of your links. Truly fascinating science. It's rather obvious why such non-invasive ground mapping techniques are important in e.g. road construction, dam safety, forensics and groundwater exploration to name just a few. The variety of techniques are the most interesting for me. The most obvious is electromagnetic induction both high and low frequency (lateral coils as in popular metal detectors) but also ground penetrating radar, seismic refractions resistivity, polarisation etc.
No surprise archaeologists use such services before they dig. It's more than obvious you want to know as much as possible about the type of the ground and its contamination before you start to dig.
Geophysics just remind me an old and mysterious job of a dowser. Believe it or not, those guys still exists, e.g. in my backyard http://www.dowsingaustralia.com/ I met one guy who tried to show me how to find water with his little pendulum. He found it quickly and surely and encouraged me to "feel" this big stream flowing some 5m under our feet but I felt nothing. Oh well, dowsers were very revered in my native town before the age of water piping: everybody used the dowsers to figure out where to dig a well. Now, dowsers are replaced by geophysicists because a machine that sends seismic signals and reads the ground conductivity and micro-sounds of water flows, can map all underground water much better.

 

[Horsa]

I've read one of your links. Truly fascinating science. It's rather obvious why such non-invasive ground mapping techniques are important in e.g. road construction, dam safety, forensics and groundwater exploration to name just a few. The variety of techniques are the most interesting for me. The most obvious is electromagnetic induction both high and low frequency (lateral coils as in popular metal detectors) but also ground penetrating radar, seismic refractions resistivity, polarisation etc.
No surprise archaeologists use such services before they dig. It's more than obvious you want to know as much as possible about the type of the ground and its contamination before you start to dig.
Geophysics just remind me an old and mysterious job of a dowser. Believe it or not, those guys still exists, e.g. in my backyard http://www.dowsingaustralia.com/ I met one guy who tried to show me how to find water with his little pendulum. He found it quickly and surely and encouraged me to "feel" this big stream flowing some 5m under our feet but I felt nothing. Oh well, dowsers were very revered in my native town before the age of water piping: everybody used the dowsers to figure out where to dig a well. Now, dowsers are replaced by geophysicists because a machine that sends seismic signals and reads the ground conductivity and micro-sounds of water flows, can map all underground water much better.

I'm very sorry for the late response. I went to a Roman Day on Saturday & stayed over at my Sister's.

I'm glad you enjoyed. I found it fascinating too. Geophysical equipment is very useful. I wouldn't mind having a go at pushing 1 of those geophysical machines around an archaeological site.

How do radars work?

I agree. Archaeologists get geophysics teams in before they dig to find man-made structure anomalies so that it doesn't take them as long to decide where to dig so they can get more done more quickly & hopefully find more artefacts.

That's great. Geophysics is very useful. The machinery does a lot.

I remember hearing about them & what they did but didn't realise they still existed.

 

[Horsa]

@mrzz I'm now going to try to rise to your challenge of asking an easy question.

Do you know that the bone more commonly known as your funny bone, properly called the humerus which sounds like humourous meaning funny hurts more because it's near your ulnar nerve which connects your fingers to your neck & that cubital tunnel syndrome which is caused by having your elbows bent too long like when you text too long because the nerve gets trapped & sometimes you have to have an operation to free it off & cubital tunnel syndrome is also called mobile phone syndrome? N.B. Cubital tunnel syndrome is not to be confused with carpal tunnel syndrome which is caused by too much typing.

 

[Horsa]

What is the diameter of the sun?

 

[Horsa]

When I was younger everyone had cathode ray tube t.v.'s with 4 channels well until I was 15 then channel 5 came on air. I remember learning how cathode ray tube t.v.'s worked. Nowadays, most people, including us have l.c.d. t.v.'s. How do they work, please?

 

[Chris Koziarz]

How do radars work?

I presume you mean ground penetrating radar, in context of geophysics we're discussing here.
GPR send bursts of electromagnetic waves from about 100Mhz to several GHz. Hence the name "radar" because a typical air radar (used e.g. by police) operates using similar waves. But the difference is: while the radio waves in that range penetrate air to long distances, the ground can be penetrated by few metres. The longer waves (100Mhz) penetrate deeper (several metres up to 1000m in ice) while shorter waves penetrate less. But shorter waves can map smaller objects. So you have compromise depth and accuracy. For typical uses such as mapping sub-surface man contaminations, including historic artefacts, a mid-range of around 1GHz waves are used.
The "mapping" of the underground fractures between differing layers and buried objects is drawn by analysis of the reflected waves, given that electromagnetic wanes travel at different speeds in different materials and some materials conducts worse than the underlying ground.
I found a good and simple intro to GPR here:
http://www.splashcos.org/sites/splashcos.org/files/downloads/12_GPR.pdf
In essence, GPR works on identical principles as seismic refractions, except we use sound waves in seismic refractions. Obviously electromagnetic and sound waves have very different parameters like speed of travel & penetration (sound waves can penetrate much deeper and in the materials like salty clay, where electromagnetic waves cannot) but the data analysis to create the underground mapping is the same.

 

[Chris Koziarz]

What is the diameter of the sun?

Knowing our distance from the sun (150Gm), you can measure it yourself by creating an image of the sun using a pinhole lens, and calculating the unknown side of the triangle from the triangle proportionality theorem, the very basic theorem of Euclidean trigonometry (this is as simple as 7th grade knowledge!). The experiment is shown e.g. here:

The result of this experiment is 1.5Gm, close enough to the actual value of 1.4Gm.

 

[Chris Koziarz]

When I was younger everyone had cathode ray tube t.v.'s with 4 channels well until I was 15 then channel 5 came on air. I remember learning how cathode ray tube t.v.'s worked. Nowadays, most people, including us have l.c.d. t.v.'s. How do they work, please?

LCD screen is composed of "pixels": nowadays an array 1080*1920 of them (so called "High Resolution TV", but becoming pretty standard). In old days, CRT image consisted of 480 "lines". So, today's digital image is of better resolution than old analogue image.
Each pixel consists of three miniature dots: Red Green and Blue. The colour and intensity of any given pixel is obtained by the sum of the three RGB components. The intensities of said components are usually expressed as values from 0 to 255 in typical screens and TV signals.
As such, the totally black colour is represented as RGB triplet of (0,0,0) - no signal - while totally white colour by RGB triplet (255,255,255) - maximum signal. You can play with different RGB colour e.g. here:
https://www.rapidtables.com/web/color/RGB_Color.html
The LCD display operates by supplying the appropriate amount of energy to each of 3 dots (R G and B) of each pixel in 1024*1980 matrix, to set the brightness of each dot at the appropriate level 0 to 255 (0 - off 255 - maximum) according to the series of numbers received from the TV signal (or from the computer). That's a lot of numbers: 3*1024*1980 = 6millions only for one image. Video images are typically 25 frames/sec (from old analogue standard) but new digital standards are 60 or 100 or even 200 frames/sec. That's 6millions times 200 bytes, more than 1GB/sec.
There are some methods to compress said 1GB/sec of data (sometimes compromising the loss of quality) but that's a different subject. The bottom line is: even after compression, both sending TV station/computer and the receiving LCD screen must crunch these numbers pretty fast to show you the quality LCD image. Needless to say the hardware to display the video on LCD must be fast e.g.: the diodes displaying the RGB "dots" must have very fast response time to change their brightness anywhere from level 0 to 255 within at least 1/25sec if not 1/200sec.
This question is the very basis of my professional living. Like 2+2=4 (or more precisely a definition of a "plus" operation on natural numbers) for a mathematician.

 

[Horsa]

LCD screen is composed of "pixels": nowadays an array 1080*1920 of them (so called "High Resolution TV", but becoming pretty standard). In old days, CRT image consisted of 480 "lines". So, today's digital image is of better resolution than old analogue image.
Each pixel consists of three miniature dots: Red Green and Blue. The colour and intensity of any given pixel is obtained by the sum of the three RGB components. The intensities of said components are usually expressed as values from 0 to 255 in typical screens and TV signals.
As such, the totally black colour is represented as RGB triplet of (0,0,0) - no signal - while totally white colour by RGB triplet (255,255,255) - maximum signal. You can play with different RGB colour e.g. here:
https://www.rapidtables.com/web/color/RGB_Color.html
The LCD display operates by supplying the appropriate amount of energy to each of 3 dots (R G and B) of each pixel in 1024*1980 matrix, to set the brightness of each dot at the appropriate level 0 to 255 (0 - off 255 - maximum) according to the series of numbers received from the TV signal (or from the computer). That's a lot of numbers: 3*1024*1980 = 6millions only for one image. Video images are typically 25 frames/sec (from old analogue standard) but new digital standards are 60 or 100 or even 200 frames/sec. That's 6millions times 200 bytes, more than 1GB/sec.
There are some methods to compress said 1GB/sec of data (sometimes compromising the loss of quality) but that's a different subject. The bottom line is: even after compression, both sending TV station/computer and the receiving LCD screen must crunch these numbers pretty fast to show you the quality LCD image. Needless to say the hardware to display the video on LCD must be fast e.g.: the diodes displaying the RGB "dots" must have very fast response time to change their brightness anywhere from level 0 to 255 within at least 1/25sec if not 1/200sec.
This question is the very basis of my professional living. Like 2+2=4 (or more precisely a definition of a "plus" operation on natural numbers) for a mathematician.

That's very interesting. Thank you very much for the information.

 

[Horsa]

Knowing our distance from the sun (150Gm), you can measure it yourself by creating an image of the sun using a pinhole lens, and calculating the unknown side of the triangle from the triangle proportionality theorem, the very basic theorem of Euclidean trigonometry (this is as simple as 7th grade knowledge!). The experiment is shown e.g. here:

The result of this experiment is 1.5Gm, close enough to the actual value of 1.4Gm.

Thank you very much for the answer. I remember learning that theorem at school.

 

[Horsa]

I presume you mean ground penetrating radar, in context of geophysics we're discussing here.
GPR send bursts of electromagnetic waves from about 100Mhz to several GHz. Hence the name "radar" because a typical air radar (used e.g. by police) operates using similar waves. But the difference is: while the radio waves in that range penetrate air to long distances, the ground can be penetrated by few metres. The longer waves (100Mhz) penetrate deeper (several metres up to 1000m in ice) while shorter waves penetrate less. But shorter waves can map smaller objects. So you have compromise depth and accuracy. For typical uses such as mapping sub-surface man contaminations, including historic artefacts, a mid-range of around 1GHz waves are used.
The "mapping" of the underground fractures between differing layers and buried objects is drawn by analysis of the reflected waves, given that electromagnetic wanes travel at different speeds in different materials and some materials conducts worse than the underlying ground.
I found a good and simple intro to GPR here:
http://www.splashcos.org/sites/splashcos.org/files/downloads/12_GPR.pdf
In essence, GPR works on identical principles as seismic refractions, except we use sound waves in seismic refractions. Obviously electromagnetic and sound waves have very different parameters like speed of travel & penetration (sound waves can penetrate much deeper and in the materials like salty clay, where electromagnetic waves cannot) but the data analysis to create the underground mapping is the same.

I meant radars as a whole. Thank you very much for the information. It's fascinating.

 

[mrzz]

Knowing our distance from the sun (150Gm), you can measure it yourself by creating an image of the sun using a pinhole lens, and calculating the unknown side of the triangle from the triangle proportionality theorem, the very basic theorem of Euclidean trigonometry (this is as simple as 7th grade knowledge!). The experiment is shown e.g. here:

The result of this experiment is 1.5Gm, close enough to the actual value of 1.4Gm.

Questions like this one always make me think of people like Aristarchus and Eratosthenes, who, around two thousand years ago, were able to measure a lot astronomic distances and lengths (with astonishing precision!), while today, with all the technology we have, we have to listen to people telling that the earth is flat...

 

[Chris Koziarz]

Questions like this one always make me think of people like Aristarchus and Eratosthenes, who, around two thousand years ago, were able to measure a lot astronomic distances and lengths (with astonishing precision!), while today, with all the technology we have, we have to listen to people telling that the earth is flat...

Unfortunately, scientists are not good orators or good leaders in general. Their comfort zone is to be servants of societies (or those who lead societies). Technocracy never worked, so the popular reality is always dumber than known scientific facts. But dumbness like everything related to human mind and intellect has a continuous spectrum and some dumb people are affected by this disorder more than others and said disorder may be even fashionable at times. I have the same feelings, that 21st century we're living in, is marked my unusually high degree of dumbness among leading celebrities. Those celebrities not only think the Earth is literally flat but also e.g. that Sahara desert forms the south border of Spain. Bue worst of all, the dumb arses do not even realise their ignorance but think they are the most competent people...

 

[Horsa]

Questions like this one always make me think of people like Aristarchus and Eratosthenes, who, around two thousand years ago, were able to measure a lot astronomic distances and lengths (with astonishing precision!), while today, with all the technology we have, we have to listen to people telling that the earth is flat...

Wow! That's amazing. I guess if I wanted to go further I could ask the questions "what is the circumference of the sun?" & "what is the radius of the sun?". I wouldn't have thought that there were people today who still think the earth is flat.

 

[Horsa]

Unfortunately, scientists are not good orators or good leaders in general. Their comfort zone is to be servants of societies (or those who lead societies). Technocracy never worked, so the popular reality is always dumber than known scientific facts. But dumbness like everything related to human mind and intellect has a continuous spectrum and some dumb people are affected by this disorder more than others and said disorder may be even fashionable at times. I have the same feelings, that 21st century we're living in, is marked my unusually high degree of dumbness among leading celebrities. Those celebrities not only think the Earth is literally flat but also e.g. that Sahara desert forms the south border of Spain. Bue worst of all, the dumb arses do not even realise their ignorance but think they are the most competent people...

Scientists are always too busy trying to invent things & discover things that will change the world to talk to others or lead (with the exceptions of ex-science teachers of course). There are times I think I'm the dopiest person who ever lived & admit it & act like the dopiest person ever which upsets my friends & family members who keep telling me I'm not even dopey but I know better than those celebrities. You'll be telling me next that for some people the only galaxy they know is made of chocolate & the same goes for the milky way & mars & that they think Pluto is just a Disney character. In that case they'll believe what Dad tried to get me to believe when I was a child about the moon being made of green cheese. I'm very sorry guys. I take it back. I'm not the dopiest person who ever lived.

 

[Chris Koziarz]

Some people who speak AmE dialect (perhaps most) think that United States of America is a name of a continent. At the same time, when faced with a trivia question to name one country that starts with 'U', said people stumble and are unable to move their brains. Both of these cognitive problems are likely related. We can multiply such examples.
My answer to said trivia would be Uruguay, with a nod to mrzz, their neighbour. Similarly, I would name Uganda if speaking to a friend from Africa, or USSR to a friend from Europe. Well, the latter is a former country, so a bit old fashioned answer, with a promotion of old-fashioned, discredited ideology, but still better than the promotion of 'The Land of Dumbs-Up-Over' as Men at Work should have sung about certain country on American continent.

 

[mrzz]

Ha! Had a really good laugh with both your posts.

The USA name is a particular case, I would guess, as, differently from most countries, we use the "full name" to refer to it. For example, we don't say "Russian Federation", but Russia, we don't say "Federal Republic of Germany", but Germany. On the other hand, we do say "United States of America", or USA, or just "United States", while, I guess, just -- or mostly -- Americans say "America". Further confusion comes from the fact that "North America" and "South America" are (physical) continents, while there is still the (political) concept of "Central America". So it is in fact a bit hard to grasp exactly what "America" might mean in a given sentence.

Oh, and about Uruguay, lovely place, a lot of beautiful things to see there. Also, best meat in the world -- and this is a subject I really know about. To say something "scientific" about Uruguay, the "Rio de la Plata" (which divides Uruguay and Argentina) is largest estuary in the world -- and gives you a hell of sunset...