Although named after Italian physicist Galileo Galilei, the Galilean thermometer was not invented by him. Galileo did invent a thermometer, called Galileo's air thermometer (more accurately termed a thermoscope), in or before 1603. The so-called 'Galileo thermometer' was invented by a group of academics and technicians known as the Accademia del Cimento of Florence, who included Galileo's pupil, Torricelli and Torricelli's pupil Viviani. Details of the thermometer were published in the Saggi di naturali esperienze fatte nell'Academia del Cimento sotto la protezione del Serenissimo Principe Leopoldo di Toscan e descrittedal segretario di essa Accademia (1666), the Academy's main publication. The English translation of this work (1684) describes the device ('The Fifth Thermometer') as 'slow and lazy', a description that is reflected in an alternative Italian name for the invention, the termometro lento (slow thermometer). The outer vessel was filled with 'rectified spirits of wine' (a concentrated solution of ethanol in water); the weights of the glass bubbles were adjusted by grinding a small amount of glass from the sealed end; and a small air space was left at the top of the main vessel to allow 'for the Liquor to rarefie' [i.e. expand].
3. The density of alcohol varies more with temperature than the density of water. This makes it more sensitive to temperature changes than water.
Comments from Our Readers
According to the Wikipedia article, Galileo did not invent this. His students did.
The numbers with degree sign on tags indicated that the imaqe was of a thermometer of some sort. Googled images of "glass thermometers". One image showed partial image similar to above image. It was a Galileo Thermometer. When I googled "Galileo Thermometer" many images similar to above came up. Wikipedia article on the Galileo Thermometer gives a very good explanation of how it works.
Tried many image names with no success. Glass balls in water brought up Galalio's Thermometer. Wikipedia explained device. Glass balls have constant density. Tags show temperature at which hey will be suspended. Lower temperature balls sink, higher temperature balls rise. Nothing suspended, temperature is between highest singer and lowest floater. Tags on lowest show 64 and 68 assume degrees, all tags probably 4 degrees apart. Highest sinker 72 lowest floater 76. Measured temperature probably around 74.
I'm taking a short break from trying to build ads for our orchestra's season program. Glad I recognized the device, so I didn't get distracted from my task for too long! Reminds me of why I always loved science, and gives me twinges of not regret, exactly perhaps wistfulness that I didn't pursue a science or two as a vocation. Ah, well, life has had its complications.
National Geographic model: "Displays temperatures in Fahrenheit in 2 increments from 68 to 80. Accurate to within 2. This would limit itself at my house. I like the temp lower then 68 in summer. I like a customer review:
Pros BEAUTIFUL Fun to watch. Tells The Temp
Cons NOT VERY STABLE, will break if dropped
Best Uses Tell Temp Very pretty
Comments about 17-inch Galileo Thermometer: This is a beautiful piece of art that also tells the temp. You just have to put it somewhere where it will not get knocked over and our of the reach of kids. I love the product and would purchase another one.
BOTTOM LINE Yes, I would recommend this to a friend
Buy for decorating more than function.
I was going to buy one of these for my son and wife for Christmas, but decided that it would not last long around a 6 year old and 2 cats. I don't think it would be too practical in my own home as the temps are only between 68 and 80. I just threw away the information last week. Quite a coincidence that you picked it for this week's quiz.
These thermometers can be very beautiful. Obviously they are not precision temperature instruments, but more decorative.
The density of alcohol varies more than water. Also the freezing level is lower so you wouldn't worry about it expanding and breaking the tube in Renaissance Italy. You could also make a cocktail if desperate.
N.B. Yes, just don't swallow the glass bubbles. - Q. Gen.
I just saw somewhere that the more accurate term for this device would be a thermoscope as opposed to a thermometer, as this device did not have a numerical temperature scale.
How could they put a scale on it without already having a thermometer to measure what temperature it was? Kind of like making pickles by soaking cucumbers in pickle juice. - Q. Gen.
My sister actually has one like this on her kitchen window sill!
Elaine C. Hebert
When I was in grade school, we covered temperature and thermometers, and were told that mercury was used in order to make them small, due to its extremely high density, and that water ones were better because they were more precise..... but huge.
This image somehow reminded me of that, and once I zoomed in and saw the numbers and the degree sign, I figured it had to be a water thermometer, so that's what I googled and voila. Turns out this one works in a different principle than the mercury one and uses buoyancy to indicate the temperature, and that Galileo didn't invent it. Looks like a great thing to have in my dream house
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What I find interesting is that the density of the glass bubbles doesn't change with temperature because they are fixed size. Only the density in the tube changes.
This means that the liquid in the tube (and hence maybe the tube itself) can expand and that the tube itself is not a fixed size.
I think the reason the bubbles don't change size but the tube does is because the tube is surrounded by air, but the bubbles are surrounded by a liquid. The slight changes in the size of the bubbles that would normally occur doesn't happen because the pressure of the liquid around them prevents it.
Colleen Fitzpatrick PhD Quizmaster General
was revived in the modern era by the National History Museum, London, which started selling a version in the 1990s.
A simple, fairly accurate thermometer, the Galilean thermometer it is mostly used today as decoration. The Galileo thermometer consists of a sealed glass tube that is filled with water and several floating bubbles. The bubbles are glass spheres filled with a colored liquid mixture. This liquid mixture may contain alcohol, or it might simply be water with food coloring. Since the density of alcohol is more affected by changes in temperature than the density of water, alcohol is commonly used as the liquid in a Galilean thermometer.
Attached to each bubble is a little metal tag that indicates a temperature. A number and degree symbol are engraved in the tag. These metal tags are actually calibrated counterweights. The weight of each tag is slightly different from the others. Since the bubbles are all hand-blown glass, they aren't exactly the same size and shape. The bubbles are calibrated by adding a certain amount of fluid to them so that they have the exact same density. So, after the weighted tags are attached to the bubbles, each differs very slightly in density (the ratio of mass to volume) from the other bubbles, and the density of all of them is very close to the density of the surrounding water. An object immersed in a fluid experiences two major forces: the downward pull of gravity and the upward push of buoyancy. It is the downward force of gravity that makes this thermometer work.
The basic idea is that as the temperature of the air outside the thermometer changes, so does the temperature of the water surrounding the bubbles. As the temperature of the water changes, it either expands or contracts, thereby changing its density. So, at any given density, some of the bubbles will float and others will sink. The bubble that sinks the most indicates the approximate current temperature.
Consider this example:
Let's say there are five bubbles in the thermometer: •A red bubble that represents 23 degrees •A green bubble that represents 24 degrees •A orange bubble that represents 25 degrees •A blue bubble that represents 26 degrees •A yellow bubble that represents 27 degrees
The red bubble (23 degrees) is the heaviest (densest) bubble, and each bubble thereafter
is slightly lighter, with the yellow bubble being the lightest. Now, let's say the temperature in the room is 25 degrees C. Since the surrounding air is 25 degrees, we know the water inside the thermometer is also about 25 degrees. The red and green bubbles (23 and 24 degrees, respectively) are calibrated so that they have higher densities than the water at this temperature, so they sink. The blue and yellow bubbles each have a density that is lower than the surrounding water, so they float at the very top of the thermometer. Since the orange bubble is calibrated to represent 25 degrees C, the same temperature as the water, it sinks slightly so that it is floating just below the blue and yellow bubbles -- thereby indicating the room's temperature!
It turns out that the eardrum is an extremely accurate point to measure body temperature from because it is recessed inside the head (just like your tongue). The problem with the eardrum is that it is so fragile. You don't want to be touching the eardrum with a thermometer.
This makes the detection of the eardrum's temperature a remote sensing problem. Granted, it is not very remote -- just a centimeter or so. But it's remote nonetheless! It turns out that the remote
sensing of an object's temperature can be done using its infrared radiation. This technique is a very good way to detect the temperature of a person's eardrum.
All of the objects around you are radiating infrared energy right now. Human beings don't have any sensors that can detect subtle differences in infrared, but our skin can detect objects radiating lots of infrared energy. When you warm yourself by standing close to a fire, the "warmth" is infrared energy that you are absorbing. The idea behind the temperature sensor in the ear thermometer is to create a device that is sensitive to very subtle changes in infrared emission. One common sensor is the thermopile, which can be accurate to a tenth of a degree. The thermopile sees the eardrum and measures its infrared emissions. The emission is converted into a temperature and displayed on an LCD.