How cold is the universe?Physics behind the temperature of the universe
In science fiction movies, the universe is believed to be incredibly cold, but even below freezing, the universe itself is not necessarily cold. In fact, it doesn’t really have any temperature.
Temperature is a measure of the speed at which a particle moves, and heat is the amount of energy that an object’s particles have. Therefore, in a truly empty space, there are no particles, no radiation, and no temperature.
Of course, space is full of particles and radiation to generate heat and temperature. So how cold is the universe? Is there really an empty area? Also, is there a place where the temperature drops to absolute zero?
Related: Where is the coldest place in the universe?
How the stars are heating the universe
The hottest areas of the universe are in the immediate vicinity PerformerContains all the conditions for initiating fusion.
Things really warm up when the radiation from the stars reaches a spot in the universe with lots of particles.This gives radiation from stars like Sun Something that actually acts.
that’s why Earth It is much warmer than the area between our planet and that star. The heat comes from particles in our atmosphere that oscillate with solar energy and then collide with each other to distribute this energy.
However, being close to our stars and having particles does not guarantee warmth. Mercury —Closest to the sun — Extremely hot during the day and extremely cold at night. Its temperature drops to a minimum of 95 Kelvin (-288⁰Fahrenheit / -178⁰Celsius).
The temperature drops to -371⁰F (-224⁰C) UranusEven colder than the planet farthest from the Sun, NeptuneStill has an incredibly cold surface temperature of -353⁰F (-214⁰C).
This is the result of Uranus colliding with an Earth-sized object early in its existence, causing Uranus to orbit the Sun at an extreme tilt and become unable to be trapped by the heat inside it.
Particles far away from the stars are so widespread that no heat transfer other than radiation is possible. That is, the temperature drops sharply. This area is called the interstellar medium.
The temperature of the coldest and densest molecular clouds in the interstellar medium is 10 K (-505⁰F / -263⁰C or), while the temperature of the less dense clouds is 100 K (-279⁰F / -173⁰C).
What is Cosmic Microwave Background?
The universe Is very vast and filled with so many objects. It is impossible to give a single temperature to a space, as some are extremely hot and others are unimaginably cold.
Still, there is something that permeates the entire universe at a uniform temperature of 1 / 100,000. In fact, this difference is so small that the change between hotspots and coldspots is only 0.000018K.
this is, Cosmic Microwave Background (CMB) And it has a uniform temperature of 2.7K (-45⁰F / -270⁰C). This is only 2.725 degrees above absolute zero, as 0 K is absolute zero.
CMB is the remnant of an event that occurred only 400,000 times later. big bang It is called the last scatter.This was the point after the universe was no longer opaque Electronic It binds to protons to form hydrogen atoms, preventing electrons from scattering light endlessly and allowing photons to move freely.
Thus, this fossil relic “frozen” in space represents the last point where matter and photons are aligned in terms of temperature.
The photons that make up the CMB are not necessarily so cold, it takes about 13.8 billion years to reach us, and the expansion of the universe Redshift These photons lower the energy level.
It is estimated that the starting temperature of the radiation that makes up the CMB, which occurred when the universe was much denser and hotter than it is today, was about 3,000 K (5,000 ° F / 2,726⁰C).
As the universe continues to expand, it means that the universe is getting colder than ever, and it is getting colder and colder.
What if you are exposed to space?
If an astronaut is left to drift alone space After that, as is often depicted in science fiction novels, astronauts could not be frozen even when exposed to a vacuum close to space.
There are three ways to transfer heat: conduction generated by contact, convection generated when a fluid transfers heat, and radiation generated by radiation.
Due to the lack of material, conduction and convection do not occur in empty space, and heat transfer occurs slowly only in the radiant process. This means that heat is not transferred rapidly in space.
Because freezing requires heat transfer, exposed astronauts lose heat solely through the radiant process and die under reduced pressure much faster than they freeze and die due to the lack of air.
Additional resources
For more information on the nature of the universe, seeAstrophysics for people in a hurry (Opens in a new tab)“With Neil deGrasse Tyson”Origin of the Universe: Cosmic Microwave Background Exploration of Radiation and Quantum Gravity (Opens in a new tab)“By Keith Cooper.
References
- Harvard University, “Human body in space: The distinction between facts and fiction (Opens in a new tab)“, July 2013.
- NASA, “Fluctuations in cosmic microwave background radiation (Opens in a new tab)“, Accessed in July 2022.
- NASA, “Cosmic microwave background radiation (Opens in a new tab)“, July 2022.
- NASA, “Ryukotsuza Eta (Opens in a new tab)“, September 2020
- Paul Sutter, “You will not freeze to death in space (Opens in a new tab)“, Forbes, April 2019.
How cold is the universe?Physics behind the temperature of the universe
https://www.space.com/how-cold-is-space/ How cold is the universe?Physics behind the temperature of the universe
