Five mysteries about our Universe
Our Universe is a mystery. It is a collection of mysteries. The more we learn, the more we realize that there is so much more we don’t know. Here are five great mysteries. CARD TITLE: Five mysteries about our Universe with cosmologist Carlos Frenk MYSTERY 1 There is no reason to believe that our Universe is unique. It is entirely possible that just as our universe was created, many universes were also created. If so, then we live, not in a single universe, but in a vast collection of universes that physicists call the multiverse. We can think of them as island universes – each with their own quirks, perhaps even each with their own laws of physics. For example, there could be one of these other universes where gravity is 100 times stronger than it is in our Universe. If we could somehow conclusively prove the existence of multiple universes, of the multiverse, that would be a real intellectual revolution – a complete shift in our cosmic thinking. MYSTERY 2 The dark side of the Universe is a very big mystery. Dark matter and dark energy represent no less than 96% of what the Universe contains. The stuff you and I, the Sun, the Earth, the stars, the galaxies are made of, is just the icing on the cake. It represents only 4% of what our Universe contains. The most likely explanation for dark matter is that it’s made up of an exotic fundamental particle that came into being just a tiny fraction of a second after our Universe was formed in the Big Bang. But it’s a mystery. We have irrefutable proof that it is there. We suspect it is a fundamental particle. But, frustratingly, it has yet to be discovered. MYSTERY 3 I think most people have heard of black holes. Fewer may have heard of white holes. White holes are kind of the opposite of a black hole. Black holes eat everything. White holes vomit everything. Nothing can come out of a black hole. Nothing can go into a white hole. Whether or not white holes exist is a hotly debated topic. Of course, if they exist, they are fascinating, and they may even raise the possibility that they act as tunnels to other universes, or even to other times in our own Universe. But they remain hypothetical objects. MYSTERY 4 The current view in cosmology is that everything we see in the Universe – everything – started life as something called a quantum fluctuation. It seems mysterious. Let me explain to you what it is. When the Universe was born, it expanded very rapidly in a very short period of time known as “cosmic inflation”. As the Universe expanded, these quantum fluctuations were stretched, and this stretching seeded the Universe with tiny ripples. These undulations are however at the origin of galaxies, clusters of galaxies, planets, Earth and humans. The mystery here is, is it really possible that a sub-microscopic entity like a quantum fluctuation could possibly develop in the Milky Way galaxies? If you had told me that a few years ago, I would have thought, “You really are crazy.” And yet today the standard model of cosmic structure formation is exactly what I have just described. MYSTERY 5 Time fascinates, not just physicists, it fascinates everyone. And yet, it is a relative concept. For example, if you travel faster and faster, time slows down more and more. If you travel at the speed of light, time simply stops. If you look at the equations of physics, it’s striking that time can go forward or backward – the equations of physics don’t discriminate. For this reason, many people believe that you can travel to the past, because nothing in the equations of physics prohibits you from doing so. It’s entirely possible that we can in principle time travel, as long as we don’t introduce any inconsistencies with the future. So there you have it, five great cosmic mysteries. But each mystery – as is always the case in science – leads to another, even greater mystery. And we haven’t even figured out the biggest mystery of all yet: are we alone in the universe? But this is a whole new story.
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