Gravity is everywhere! Anything that has mass exerts a gravitational force, including you and me! Why can we not feel that force? We are in the presence of a massive object that pulls on us more than we could ever pull on each other, and leaves our personal gravitational pull negligible. That’s right, I am talking about the Earth! In the absence of a large object with mass however, even tiny specs of dust and atoms of gas can feel a force pulling them together.
What does gravity have to do with a stretchy vortex table? According to Einstein’s Theory of Relativity, the universe is not actually flat, but a stretchable fabric called spacetime. Gravity, in this theory, can be represented as curvature in the fabric of spacetime. In the diagram below, the Earth is causing the 2-Dimensional grid to stretch into the 3rd Dimension. In our 3-Dimensional universe, we can only imagine how gravity would stretch spacetime into the next dimension: the 4th Dimension!
Our Vortex Table is a great model for how gravity affects spacetime. Any mass in the center of the table causes a small curvature in the fabric, which automatically attracts any other object placed on the table. It is easy to see that the heavier the mass in the center, the greater the downward slope of the table, and therefore, the greater the gravitational pull on other objects.
The formation of stars is caused entirely by the gravitational force of attraction and can be modeled on the Vortex Table. Clouds of dust and gas in the universe, called nebulae, are where stars are formed. The gas in a nebula is pulled together by the force of gravity to form a dense patch of gas called a protostar, which attracts even more gas and dust to become a full star.
The formation of a star and its Solar System is not the only thing we can model on our awesome stretchy table. When an extremely massive star dies, it becomes a black hole. A black hole is a very dense and very massive, causing a huge curvature in spacetime. Black holes have so much gravity that light can’t escape, so we have difficulty detecting them directly. To find black holes, astronomers look for the stuff around it, such as stars orbiting something invisible, or material that is getting accelerated to very high speeds.
Simulating a black hole with fabric is difficult…Imagine the vortex table stretched so far down that the hole goes down into infinity! The resulting slope can affect stars and planets more than 50,000 lightyears away, about the radius of our galaxy. Scientists theorize that there is a supermassive black hole at the center of every galaxy, which is what holds everything together. Look familiar?