Tag: coldest

Coldest Spot in The Universe

By Anupum Pant

Where do you think is the coldest spot in the universe. Like many would have guessed, somewhere in the deepest places in space, the temperature would be coldest than anything else. After all, space being so massive, the probability that happening is so high outside of Earth. Probably the Boomerang Nebula is the coldest. At least that is what Google says:

At a positively frigid one Kelvin (that equates to –458 degrees Fahrenheit or –272 degrees Celsius), the Boomerang Nebula in the constellation Centaurus is officially the coldest known place in the entire Universe. It’s even colder than the background temperature of space!

No!

Behold, the coldest temperature ever recorded anywhere in the universe is in a laboratory, here on Earth – at MIT! It is extremely close to what the coldest temperature can be theoretically.

They call it the Bose-Einstein condensate (BEC). and the temperature reached has held a record since the year 2003 and in numbers, it is 10 trillionths of a degree F above absolute zero.

And the process ironically involves heating up to 700 degrees celsius to obtain a lots of free sodium atoms. Then, ironically again, they are hit with a laser to make them move lesser. And finally a special kind of evaporative cooling is done to reach nano-kelvin levels. That is how, extremely cold temperatures are reached.

The Coldest Place on Earth

By Anupum Pant

A couple of days back I wrote about the hottest place on earth. That made me think of how cold the coldest place would be. I was sure it’d be somewhere in one of the poles, but I wasn’t sure where exactly it was.

This is what Google said:

Aerial photograph of Vostok Station, the coldest directly observed location on Earth. The lowest natural temperature ever directly recorded at ground level on Earth is −89.2 °C (−128.6 °F; 184.0 K), at the Soviet Vostok Station in Antarctica, on July 21, 1983.

After a little more digging, I found that his was the old record. Turns out, the coldest place on earth now, not counting the laboratories, is still in the high ridges of the East Antarctic plateau close to Vostok station. It’s called the Dome B. And the coldest times happen when all the conditions are perfect.

When the conditions are right, the temperatures during winters can reach minus 92 degrees Celsius!

Why is a Metal Plate “Colder” Than a Plastic Plate?

by Anupum Pant

No, it isn’t!

What is Cold?

According to the dictionary, a body at a relatively lower temperature, especially when it is compared to the temperature of a human body is described as a colder one. So, any object below the normal human body temperature – about 37 degrees Celsius – is a cold thing. But wait a minute!

When you touch an object, what does it tell you about the temperature of the object? Can you really judge if it is a cold one or a hot one? Unfortunately, our bodies aren’t thermometers, we are not so smart when it comes to judging the temperature. Consider the following case.

A book and a steel plate kept in the same environment for a long time attain the same temperature eventually (it is called thermal equilibrium). This can be checked by using a thermometer on both the objects. But, when people are asked to touch a metal plate and a book, they find the former to be much cooler. You can try this out yourself by touching different materials around you. You’ll see how some things ‘feel colder’ while the others feel warmer. A YouTube channel Vertasium conducted a social experiment to record this on camera. See the video below:

There is no cold – only heat

So, in the video, ice melts faster, if kept on steel plate than on a plastic plate, even when the steel plate ‘feels colder’. Common sense dictates that the colder thing is supposed to sustain the ice block for a longer time, just like your refrigerator does. So why does the opposite happen?

A better way to understand this ‘contradiction’ (not really a contradiction) can be this:

According to thermodynamics, simply put, everything has heat in it. So, even a cold ice block has some amount of heat stored in it (say, around 273.15 Kelvin or 0 degree Celsius). When one object comes in contact with other object, it loses or gains heat till their temperatures get equal or till they attain ‘thermal equilibrium’. Which object loses heat and which one gains it, is decided by their relative temperatures. In case of ice and steel, ice has a lower temperature than steel (assuming it isn’t already freezing out there). Therefore, here, ice gains heat from steel till they attain the same temperature and ice melts.

Side note: The ice is also in contact with a relatively ‘hotter’ atmosphere. Hence, it gains heat from there also. In this case, we are only concerned about the steel and ice interaction.

Why does it melt faster on steel?

There is a particular property which depends on the kind of material and is called thermal conductivity. This is the parameter which decides which objects lose heat quicker and which ones do it slower.

Here, for instance, steel has a higher thermal conductivity than plastic. Hence, the steel plate gives away heat to the ice block faster than a plastic block does. As a result, ice melts faster on a steel plate than on a plastic one.

Incidentally, this effect can also be used to explain why one plate feels colder than the other, in our hands. Think of it like this, the ice is replaced by our hand. So, a steel plate, due to its better thermal conductivity, draws heat faster from our hand than a plastic plate. This makes us feel that the steel plate is colder than the plastic one.

As checked by a thermometer, both the plates have the same temperature, our bodies are only fooled into believing that the thing we feel is temperature; it isn’t. None of the plates is actually colder than the other (according to the dictionary – see first paragraph). We don’t feel the temperature. What we feel is actually the rate of heat being drawn away from our hand. Faster an object draws heat, the colder it feels.