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This mysterious stuff is known as dark matter, which is really little more than a name for our ignorance. The name invisible matter would be more apt, since it looks transparent rather than dark, and can pass through your hand without your noticing. Indeed, dark matter from space that strikes Earth appears to typically pass unaffected through our entire planet, emerging unscathed on the other side.
For a theory to be falsifiable, we need not be able to observe and test all its predictions, merely at least one of them.
I’m going to argue that there is: the fact that our Universe appears highly fine-tuned for life. Basically, we’ve discovered that many of those knobs that we discussed appear tuned to very special values, and if we could change them even by quite small amounts, then life as we know it would become impossible. Tweak the dark-energy knob and galaxies never form, tweak another knob and atoms become unstable, and so on.
Another universe-creation mechanism, proposed by Lee Smolin, involves mutating and sprouting new universes through black holes rather than through inflation. This would produce a Level II multiverse as well, with natural selection favoring universes with maximal black-hole production.
In so-called braneworld scenarios, another three-dimensional world could be quite literally parallel to ours, a short distance away in a higher dimension. However, I don’t think that such a world (brane) deserves to be called a parallel universe separate from our own, since it can interact with it gravitationally much as we do with dark matter.
Everything we call real is made of things that cannot be regarded as real. —Niels Bohr
According to a recent estimate, more than a quarter of the U.S. gross national product is now based on inventions made possible by quantum mechanics, from lasers to computer chips.
The Austrian animal behaviorist Konrad Lorenz mused that important scientific discoveries go through three phases: first they’re completely ignored, then they’re violently attacked, and finally they’re brushed aside as well known.
A famous thorny issue in philosophy is the so-called infinite regress problem. For example, if we say that the properties of a diamond can be explained by the properties and arrangements of its carbon atoms, that the properties of a carbon atom can be explained by the properties and arrangements of its protons, neutrons and electrons, that the properties of a proton can be explained by the properties and arrangements of its quarks, and so on, then it seems that we’re doomed to go on forever trying to explain the properties of the constituent parts.
The distinction between past, present, and future is only a stubbornly persistent illusion. —Albert Einstein, 1955
when we think about the “present,” we mean the time slice through spacetime corresponding to the time when we’re having that thought. We refer to the “future” and “past” as the parts of spacetime above and below this slice.
time is not an illusion, but the flow of time is. So is change. In spacetime, the future exists and the past doesn’t disappear. When we combine Einstein’s classical spacetime with quantum mechanics, we get quantum parallel universes
This means that there are many pasts and futures that are all real—but this in no way diminishes the unchanging mathematical nature of the full physical reality.
