The Swiss Cheese of the Universe
The Swiss Cheese of the Universe
This post originally appeared in the UO’s blog The Oxford Universe.
What does it mean to be a philosopher is to stand at the gate of a new domain and to be able to enter it from time to time and to go to the best of your ability? This might seem to go against the grain of many philosophers, who seem to think that their understanding of the world is a sort of divine revelation, but if any of my readers know the stories of Friedrich Nietzsche, Ludwig Wittgenstein, and Martin Heidegger, it’s easy to understand how those philosophers were able to enter into and live in the world. They were able to walk into the territory of the unknown world and to become what we would call “real”. To enter the territory of the unknown world is to be able to stand at the gate and to be able to see beyond the realm of the known. This is the kind of world-view that Friedrich Nietzsche, Ludwig Wittgenstein, and Martin Heidegger were able to step into. This is the kind of world-view that Friedrich Nietzsche, Ludwig Wittgenstein, and Martin Heidegger were able to step into.
It is a good idea to go to the best of your ability and to go to the best of your ability to enter into the new domain. This is a good idea for those who want to be good at something and for those who, like me, want to be a poet. To be a poet is to strive to become the best of the best. This is what I want for myself. To be a philosopher is to strive to understand the laws of the natural world, and to strive to understand the laws of the natural world is to be able to understand the laws of the natural world. This is a good definition of a philosopher — someone who enters the new domain from time to time and tries to understand what is in the new domain.
This post originally appeared in the UO’s blog The Cambridge Reading.
We are now entering a new domain: the new domain of the scientific world. That new domain is that of modern science and technology, and I am going to tell you about the new science and technology that is currently emerging. I should warn readers now, because I am going to use a kind of hyperbole when I describe modern science and technology.
Measuring the Extra Gravity in Galaxies
Brouwer and her colleagues chose over 259,000 isolated galaxies for which they were able to measure the so-called RAR (Radial Acceleration Relation). This RAR compares the expected amount of gravity based on the visible matter in the galaxy to the amount of gravity that is actually present – in other words : the result shows how much extra gravity is there in addition to that of normal matter. Until now, the amount of extra gravity was only determined in outer galaxies by monitoring the motion of stars and in a region about five times larger by measuring the rotational velocity of cold gas. Using the lensing effects of gravity, the researchers were now able to determine the RAR at gravitational strengths that were one hundred times smaller, allowing them to penetrate much deeper into the regions far outside the individual galaxies. This made it possible to measure the extra gravity extremely precisely – but this gravity is the result of invisible dark matter or do we need to improve our understanding of gravity itself?
Since the beginning of the Universe, we have been observing the very early Universe. It is a very special part of the universe, which is very hard to detect directly. But we have indirectly observed gravity in stars, in the interstellar medium, and in dark matter. From the very beginning, we have observed that the distribution of objects along the universe’s main axis is different in different regions. At the beginning (at about 380,000 years after the Big Bang), the mass of the average galaxy was much less than that of the entire universe. By the time of the Big Bang, the mass of the galaxy had increased enormously—by a factor of about 5 or 6 relative to its time of origin. The total mass of stars and galaxies in galaxies—the mass of the very early galaxies, in the case of the Milky Way—is about a million times greater than it was at the beginning.
This difference is called “extra gravity. ” In the time of the Big Bang, the galaxy was less dense than the rest of the universe. Then, as time went by, we got into a period of extremely high density. The ratio of the mass in stars today to the mass in stars at the top of the stars’ distribution, in the Milky Way, goes from a very small value of just a few percent to a large value, about half. (In this way, we found the missing mass. ) The total mass of the galaxy and of stars is about one billion times higher today than in the early times, and, in the time of the Big Bang, the galaxy and the stars were about two and a half times higher density.
We have now observed that there are dark matter particles that are gravitationally held together, so that they are distributed over a large area. Such dark matter particles could give the galaxy some gravity—and so we have observed the effect—but we do not yet know how gravity works.
Extra Gravity in Outer Regions of Galaxies
Until now, the amount of extra gravity had been determined only in outer regions of galaxies by the observation of the motions of stars and in a region about five times larger by measuring the rotational velocity of cold gas. Using the lensing effects of gravity, the researchers were now able to determine the RAR at gravitational strengths which were one hundred times smaller, allowing them to penetrate far deeper into the regions outside the individual galaxies.