Physics
Is the “Fabric of Spacetime” Actually a Fluid?
If you’ve studied fluid dynamics at all, you’ll know that there is still a lot to be discovered, especially as it applies to turbulent flow. But, what happens when a fluid is SUPER cold— as cold as outer space?
Well, we already know what happens to a fluid that is SUPER cold, right? I mean, outer space is only a few degrees above “Absolute Zero” (-460 degrees F) so any fluid out there would freeze almost instantly, right?
I mean there are entire comets that are made of ice formed from super cold fluids. Even some of the moons of Saturn are covered with ice!
However, there are certain fluids which will NOT freeze into a solid — even in the cold depths of our Universe. More specifically, liquid Helium is one of those fluids that will not freeze at those extremely low temperatures.
Rather, it becomes what we now call, a “Superfluid”.
Woah, What the Hell is a “Superfluid”?
The sarcastic answer is that it’s a fluid that exhibits some super properties.
While that is actually true, a superfluid is almost like an entirely new state of matter! In fact, to fully understand this exotic material, you should take some time and watch some of the videos linked in this article later on!
Now, let’s quickly review what actually happens to a regular fluid, like water, when it reaches its freezing point.
Under normal conditions, let’s say a glass of water on your kitchen table, the water is still in its liquid form. Its viscosity is rather low, and it’s neither hot nor cold.
Even if the surface of the water is perfectly still, there is a ton of activity happening on the atomic level.
The water molecules which make up the water itself are all moving freely, bumping into one another and into the sides of the glass. While there is some cohesion to their collective movement, each molecule moves and vibrates as an individual molecule.
If we were to decrease the temperature of the water by putting it in the freezer, the molecules would all slow down. The water is still a liquid and the molecules are still freely moving, but they are moving much more slowly than they were at room temperature.
As the water approaches the freezing temperature of 32F (0 degrees Celsius — because that actually makes sense) the molecules are slowed to the point where they actually stop moving around so freely. Rather, they group together and begin vibrating against each other.
The water physically freezes when all of the water molecules are so tightly packed together that they form a solid object. In this case, that solid object is ice!
Although not important for this article, the water molecules will inversely move faster and faster as the temperature increases until they begin to actually leave the water as vapor.
But what does any of this have to do with Helium?
Well, water isn’t the only liquid which can freeze, and liquids mostly freeze for the same chemical reasons. Liquid Helium, on the other hand, is not like most other liquids. When it “freezes”, something absolutely incredible happens.
The molecules do indeed slow down and vibrate together. However, rather than forming a solid and acting as one cohesive object, Helium remains a liquid while acting as one cohesive object.
On the atomic level, the molecules all vibrate at such an energy level that all of their wave forms become one. They all move and flow as if they were all one big molecule of water. The superfluid can still flow, just like water, but it can flow MUCH better than water.
Because the molecules act as one, there is no friction between them which means its viscosity is literally zero since there is absolutely no resistance to flow.
In fact, the superfluid can flow through any hole or crack in an object, regardless of how small it may be!
For a much more detailed explanation, check out this SciShow video!
However, there is another incredible phenomena which occurs thanks to vibrating molecules in a fluid!
Sonoluminescence — Light From Water
You’ve heard of bioluminescence and hopefully caught a fire fly or two as a kid (I never did and was hoping you could tell me about it!) on a summer night.
In fact, if you’ve ever seen a scorpion under a black light, they actually appear bright green as if they were glowing in the dark!
I didn’t believe it the first time a friend told me about this. Luckily they had a pet scorpion, and a black light to prove me wrong! Needless to say, I was pleasantly surprised.
The point is, there are more light sources in the world aside from stars, light bulbs, and fire. If you were able to go hang out at the bottom of the ocean, you’d meet a whole bunch of bright creatures down there!
But, I’d be willing to bet you never thought sound or water could ever be a light source. I mean, water puts out fire, right? How the hell can we make water a light source? And sound? That’s just crazy talk, right?
How could this possibly work?
The real answer is obvious; under very specific conditions in an experimental setting. But the technical answer is MUCH more fun!
Although it gets more complicated than this, all you need is a beaker of water, an eye dropper, and a very accurate ultrasonic frequency generator. What you get at the end is what some call the, “star in a jar”.
You use the eye dropper to drop some water into the flask which will form an air bubble. Typically the air bubble will float back to the top and pop, or stay submerged for a moment and pop for other reasons.
In this experiment, we have a very specific frequency of sound being played at a reasonable volume. The frequency will depend on the resonant frequency of the glass beaker so the specific one to use will vary. The point is, the glass beaker and the water itself are vibrating at a specific frequency.
Under those conditions, something rather amazing happens to the air bubble in the water. Rather than floating to the top and popping, it remains submerged in the water.
As if that were not strange enough, the bubble can also expand and contract as you adjust the frequency. As the bubble contracts, it actually starts to glow extremely brightly (for the relative size of the bubble and ambient lighting in the room) and can produce temperatures far beyond your wildest imagination (upwards of 20,000 F).
Now, those extreme temperatures obviously only exist for a split second, but as long as the frequency isn’t too high, the air bubble will continue to produce light. As you can see in this really cool video, it looks like a star has been plucked right out of the sky and plopped into a jar of water!
What Does Any of This Have to Do With Space?
At first I thought it was a coincidence that the vibrating air bubble looked just like a star in space. In fact, it wasn’t even being impacted by gravity! The bubble just stays in place and glows as if it actually were a star floating in space.
Then I remembered that there is no such thing as coincidence.
I thought about it for a minute and an idea came to me. What if space itself is a fluid? Not just any fluid, but a superfluid of some kind.
Okay, it wasn’t just that one single experiment that gave me that idea, but it was the one which caused me to think of it.
But, the question of gravity — that pesky gravity — was still going to get in the way. Although the air bubble in the experiment seemed unaffected by gravity, it’s still just a tiny air bubble in water.
The classic way we visualize gravity is a curvature of the fabric of spacetime.
That is a great way to visualize gravity if the fabric of spacetime were indeed… a fabric.
But what if spacetime were a fluid? “Curvature of fluid” doesn’t make any type of sense, does it? Sure, the meniscus of a graduated cylinder is curved, but that’s beside the point here.
Rather than curvature of the fabric of spacetime, what if it were all about the “flow of the fluid of spacetime”?
If space were a superfluid, then it would make intuitive sense that a flowing current would make a great analogy for gravity. But, what exactly does that mean? What would cause the fluid of spacetime to flow?
To fully visualize this analogy, you need to watch this very curious experiment/thought experiment.
In the video, the person demonstrates a great visualization of gravity using a bucket of water and a small ball with holes and a hose attached to the top. The water represents spacetime, and the ball represents matter in space.
While the ball is submerged in water, suction is put on the ball which causes water to flow through the holes. You don’t notice anything at first and it just looks like a ball in water. However, when he adds dye to the water, you can actually see the “flow of space”. That flow represents the visualization of gravity.
That video really got me thinking about space as a fluid. Then I did some research on Helium as a superfluid. There are a couple things about a superfluid that connects my thinking behind both of the experiments mentioned in this article.
Since a superfluid is frictionless, and acts as a single cohesive molecule, it can actually flow through any sized hole or crack large enough for a single Helium atom.
That is what made me connect the dots. If space were a superfluid, and the superfluid could flow through almost any hole, then it would make perfect sense to think of gravity as the flow of spacetime as it flows through matter (on the atomic level) itself.
On a microscopic level, practically any object is porous. Even a bar of steel is porous. Yes, metal can actually absorb moisture in the air. That’s precisely why some metals (not aluminum) oxidize, or rust.
Assuming all matter is somewhat porous, it makes sense that if space were a superfluid, it would flow through any piece of matter.
In that case, the more massive the object, the stronger the flow would be! That would coincide with a more massive object having a stronger gravitational field in the classical world!
So, is Space a Superfluid?
Well, it could be! Or maybe it isn’t! Maybe space is simply just a vacuum of void filled with electromagnetic radiation with nothing to discover but a few clouds of dust, rocks of liquid — frozen or otherwise, and giant gaseous spheres.
I’d like to think there’s more to it than just an empty void of space.
A light source can originate in a body of water, and that certainly means that heat and energy are present. If those elements can be created in a fluid, then a superfluid is a good candidate for the makeup of spacetime.
Just look at that picture (top of page) again! It looks like a star! If sonoluminescence can exist in a jar of water, then who knows what would be possible on a cosmic scale if space were a fluid!
Sure, sound doesn’t exist in space. That is because what we call sound is pressure waves in the atmosphere, and the atmosphere contains air molecules which collide with one another to form longitudinal waves.
At the end of the day, sound is just a pressure wave. A longitudinal pressure wave in water makes sound, right? Ever listen to whale songs?
So, wouldn’t it make sense that some form of pressure wave could be formed and transmitted through a Universe full of a fluid? If that were true, then it’s extremely rational to consider that stars may be formed by way of a similar process seen in the “star in a jar” experiment discussed earlier.
Or, just imagine if this could explain black holes! The gravity of a black hole is so great that not even light can escape. Maybe that is because the “flow of space” is so strong at a black hole that light cannot “swim” against the current.
That said, maybe space really could be a superfluid. What other things could possibly be explained if this turned out to be true? Could it help explain “dark matter”?
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What do you think? Do you think the “fabric of spacetime” could actually be a fluid? Perhaps a superfluid?
Let me know what YOU think in the comments!
