I can get that we may have created something (quark-gluon plasma) at 4 trillion degrees Celsius that is hotter than a supernova, but…
How could we have created the coldest thing ever, at 100pK (less than 1 K), and that there is nothing colder? Might a single atom in deep space not have less energy? Apparently some nebula is the coldest thing out there.
In: Physics
>ever observed
This is the reason. It’s going to be hard for something to get much colder than that and it would be *really* hard to detect it with that little energy coming off of it. A single atom in deep space even more so.
The percentage of things in the universe which we have observed rounds very easily to zero.
As far as we can tell, the entire universe is filled with something called the Cosmic Microwave Background (CMB), which is sort of a leftover from the early universe when everything was much hotter and denser. Basically in the earliest moments of the universe, all space was taken up by huge amounts of hot plasma made up of subatomic particles. As the universe has expanded and become much much larger over billions of years, that energy has dissipated over the much larger volume of the current universe (compared to the early universe) and since temperature is basically the average amount of energy within a specified volume of whatever you’re measuring, that ‘background’ energy has cooled a lot since those early days, and now mainly exists as low energy radio waves. Primarily in the microwave part of the radio spectrum, hence the name Cosmic Microwave Background.
Anyways, the CMB is pretty darn uniform, and has an average temperature of about 2.725 K today. So basically everything in the universe is surrounded by ‘ambient’ energy levels of that temperature, so stuff in the universe can’t really radiate away energy to a lower temperature than that, because if it did, the CMB would radiate some its energy back into that object and warm it up to that temperature.
It does seem like there are some natural phenomena that can actively cool things below that temperature (for example in a nebula like you mentioned), but so far we haven’t seen anything as cold as what we can manage to do in purpose-built experiments.
The bulk of the universe, the near total vacuum of Space, is at approximately 2.7K due to Cosmic Microwave Background radiation, a remnant of the early moments of the Universe (aka the Big Bang).
Everything we see in space is either a star and so is hotter, or something in space (planets, satellites, etc) that even when not warmed by a star is still “warmed” by the CMB as it’s in a +/-2.7k environment so can’t cool lower than that.
To get lower, as far as we know, you need to actively cool something in an artificial environment, which we have only observed on earth.
Precisely because Earth is a easy place to conduct experiments because almost all humans and equipment are from there.
Few humans went to space for experiments (mainly in International Space Station) with limited amounts of equipment
A single atom doesn’t have a temperature. It has a velocity, which depends on your arbitrary reference: You can always define its velocity to be zero.
Temperature only exists as a property for a large set of objects, like a cloud of gas atoms. All of space is filled with some radiation, which is enough to prevent gas clouds or any other system from cooling down below ~2 K. Maybe there is a region that is at 1 K that we haven’t seen yet, but we don’t know how anything could get significantly colder naturally. “observed” means these regions wouldn’t count anyway because we haven’t observed them yet.
The question is what can we see or not see. What we see from space is based on energy effectively. Particles that have enough energy to emit gamma rays to something so little we are in the radioaves. The larger the difference from the cosmic backround radiation the easier it is to see. When looking at thongs that are really cold you have a hard time telling the signal (object(s)) from the noise (cosmic background radiation).
So while in the labs we have sensors that can detect far colder temperatures (current world record is 0.000000000038k) the boomerang nebula (you were think of) is a balmy 1K. K is the unit of measurement called kelvin. It has the same energy per unit as celcius (C). Just zero degrees C is shift up about 273.15 degrees K as that is the point when water freezes.
Could there be colder objects in the universe than the boomera ge nebual? Possibly. They will not be easy to find. Both based on our technology. And the fact where we live (on Earth and in the solar system) is a rather loud place from an electro-magnetic wavelegth or energy persoective. But the limits of what we can build here. Ine day we likely will be able to build radio telescopes that make what we have here look like a jome on the fringes of the solar system and in a quieter place further from the sun and see more than we do now. Who knows what we will see then. Sadly i will not be here during that fascinating time.
You cannot actually say a single atom has “temperature” really.
“Temperature” is really the measure of the average energy over a bunch of matter. If all you have is one atom you don’t even have “temperature” to measure or experience. Not the same as saying “zero” as a temperature just to be clear.
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