The Scale of Everything - The Big, the Small and the Planck

There is something both calming and therapeutic about looking up at the night sky and even though the Milky Way makes for stunning views of the heavens it's easy to forget that what we see with the naked eye is an incredibly tiny tiny fraction of the universe and we need tools like the Hubble Space Telescope to see the farthest objects. When it comes to the vastness of space and the massive scales involved it's difficult to imagine not only the distance involved but also the time it takes for light to travel across them compared to our everyday human scale lives and as large as the scale of space is it's only half the story. We exist somewhere near the middle between the very large and the very small where there is an even greater range of scale going down to the very smallest unit of measurement we can currently practically use, a distance so small that if a meter were scaled down to that size the entire observable universe would be just a bit larger than an atom. This is a very simplified look at the scale of everything, the big, the small and the paradox that exists at the very bottom. This video is sponsored by Brilliant. As they say go big or go home so we will start with the size of the entire observable universe. Our best guess based on observations and allowing for the expansion of the universe since the Big Bang is that it's about 93 billion light-years across that's 8.8 times 10 to the 23 kilometers with the distance from the edge of the observable universe in any direction to us being 46.5 billion light-years and here we come across a unit of measurement which tries to make things a little bit easier to comprehend, the light year or how far light will travel in one year. One light year is equivalent to 9.46 trillion kilometers still not an easy distance to comfortably comprehend but for some sort of comparison the fastest spacecraft we have yet launched the Parker Solar Probe which will observe and fly through the upper part of the Sun's atmosphere in 2024 will reach a maximum speed of 690,000 kilometers per hour by using seven gravity assists on its way to the Sun. The Parker could fly the 5566 kilometers from London to New York in 29 seconds and yet it would take the Parker probe 1565 years to travel one light year at just 0.064% the speed of light. Our nearest star Alpha Centauri is 4.3 light-years away a one-way journey time of 6729 years for the Parker. If we cloned the earth and placed these copies side-by-side to the edge of the known universe we would have to make 34 million 300 thousand trillion copies. The farthest galaxy we've seen so far GNZ 11 is approximately 32 billion light years away or 10 to the 23 kilometers it's also the oldest at 13.4 billion years. If we tried to send a probe like the Parker to GNZ 11 it would take just over 50 trillion years to get there and that's assuming that the expansion rate of the universe was zero for its entire journey as 3228 times the age of the universe to date but in reality it would never get there because the rate of the expansion of the universe is accelerating far faster than our probe could ever fly a bit like a sprinter trying to catch up with a plane. There must also be some distance farther out than the observable edge but how much farther we just don't know some suggest it could be up to 250 cosmic horizons farther out though we will probably never know where the edge of the universe is because the light from there has not and may never reach us. So let's scale things back a little bit to the largest thing in the universe, the Hercules Corona Borealis Great Wall, a galactic filament made up of billions of galaxies bound together by gravity that's about 10 billion light years across and about 10 billion light years away from us. It's now thought they could be up to about 2 trillion galaxies in the observable universe, many are small contain just a few thousand stars but some are very large galaxies like our own Milky Way with 200 billion stars and others with many more. These two trillion galaxies aren't evenly scattered throughout the universe either they are clumped together by gravity into local clusters which then create superclusters which then make up the huge filaments like the Great Wall. There are thought to be about 200 billion stars in our galaxy the Milky Way and as far as galaxies go it's pretty big at a hundred thousand light years across or about 946 trillion kilometers but our nearest galactic neighbor the Andromeda galaxy which is 2 million light years away is about 220,000 light years wide and is thought to contain up to 1 trillion stars making it the largest in our local group of galaxies. As big as Andromeda may be there are even bigger galaxies out there, Malin 1 is a low surface brightness spiral galaxy and the biggest spiral type yet found at 640,000 light years across and 1.19 billion light years away from us. However one of the biggest galaxies yet found is IC 1101 a supergiant elliptical galaxy with a diameter of its halo stretching over 4 million light years. It's estimated to contain 100 trillion stars and at its center there is a bright radio source which is thought to be an ultra-massive black hole in a range of 40 to 100 billion solar masses making it one of the largest known black holes in the universe. For all the galaxies and stars black holes and other cosmic stuff out there, space in general is a very empty place. The interstellar void between the galaxies is an almost perfect vacuum and much better than any we can make here on earth. The stuff out there is mostly single atoms of hydrogen, helium, dust particles and metals expelled from supernovas but here matter can be so thinly spread that its density can be as low as 0.1 atoms per cubic centimeter of space. Even in the space at the center of galaxies it's only about a thousand atoms per cubic centimeter. In fact when Andromeda and the Milky Way galaxies collide in about four billion years it's highly unlikely that any of the stars in either galaxy will hit another star. The space between the stars is far, far greater than the size of the stars themselves. So whilst their orbits will be flung around by the collective effect of gravity, the stars and any planets they may have will just glide past each other at still enormous distances. Stars also vary greatly in size with the vast majority of them in the Milky Way being red dwarfs, the smallest and coolest stars in the main sequence. The smallest of these having the mass and size about 8% of our Sun and a surface temperature of about 2,000 Kelvin. Because they are so small and cool they are very difficult to see beyond about 300 light-years with our current technology. Of the 60 closest stars to our Sun, 50 are red dwarfs. Because they are so small and slow burners of their hydrogen fuel their lifespans will be measured in the trillions of years. At the other end of a scale are the red hypergiants like UY Scuti, currently the largest known star which is 1,700 times our Sun with a diameter of 2.3 billion kilometers but it's only 30 times the mass of our Sun. If you placed it where our Sun is in the solar system its outer edge would engulf the orbit of Jupiter but in the very early universe there was far more hydrogen in much denser clouds from which the first stars formed. This allowed massive blue giant stars of up to a thousand solar masses or more to exist but they had very short lifespans of maybe just a million years or so before be collapsing into supernovas and exploding out some of the heavier elements that went on to become the planets like the earth and eventually us. By the time our Sun was forming there could have been well over a thousand generations of these massive stars to seed the universe with the heavier elements required. But even our Sun which is a very average star is on a massive scale compared to the earth, its diameter is 1.3 million kilometers or 1.39 times 10 to the 9 meters. An average sunspot which appears like a dot on its surface could easily swallow the earth with room to spare and you could fit a million earths inside the Sun's interior. Even some of our local planets are on scales which are huge, Jupiter's diameter of a hundred and forty thousand kilometers is larger than the smallest star yet found and its largest storm system the red spot which has been raging for 340 years is 1.3 times the size of the earth. On Mars, Olympus Mons the tallest volcanic mountain in the solar system is two and a half times the height of Everest and the Mariner Valley is the largest canyon in the solar system that stretches over 3,000 kilometers and over 8 kilometers deep in places. You could lose our Grand Canyon in one of its side channels. And then we reach human scale, one meter. But we are not just one entity, the average human consists of about 30 trillion cells all working together, each one containing a strand of DNA consisting of 3.2 billion base pairs coiled around itself to form a double helix which is such an impressive piece of packaging but if you straightened it out it will be over two meters long and yet coiled up it's just six microns across, a micron being a thousandth of a millimeter or 10 to the minus six meters. Small as it may be if you took all the DNA in your body stretched it out and joined it end-to-end it would be over 60 billion kilometers long, enough to reach from the earth to Neptune and back about seven times. But life gets smaller. Mycoplasma genitalium is a parasitic bacterium that lives in the bladder and waste disposal organs of primates and is the smallest to be capable of independent growth and reproduction and is about two to three hundred nanometers in length, over ten times smaller than that of the coiled DNA. Viruses take this a stage further by dumping the need for a cell body altogether and instead hijack other cells to make copies of themselves. Viruses are the smallest living thing though technically they aren't alive as they cannot reproduce without a host cell to do the work for them and although their size is around 2 times 10 to the minus 7 or 20 nanometers across there are thought to be at least 10 to the 31 individual virus particles on earth, more than there are stars in the known universe by about a hundred million times and if you lined them up end-to-end they would stretch out a hundred million light-years. Moving down through molecules to atoms we reach what was thought to be the smallest building blocks of matter at 10 to the minus 10 meters. Most atoms are between 10 to 300 picometers but the nucleus of an atom is 10,000 times smaller in the range of 1 to 10 femtometers or 10 to the minus 15 meters. The nucleus of an atom is made up of protons and neutrons except for hydrogen which has no neutrons. Protons or neutrons are made up of smaller fundamental particles called quarks, leptons, gauge bosons and a Higgs boson. Here we're getting down to 10 to the minus 20 meters and you would think that we'd reached the end of our measurement scale but no there are another 15 orders of magnitude to go before we reach the Planck length. At these scales matter is described by quantum mechanics and becomes so strange that the physicist Richard Feynman said, if you think you understand quantum mechanics you don't understand quantum mechanics. Particles here are best thought of as excited states or quanta of an underlying quantum field and there are the very limits of our knowledge where you can never know the exact position of a quantum object. They can be waves or particles and randomly pop into and out of existence for a few billionths of a second but what of the Planck length and is it the smallest distance there is? Well basically it was conceived by the theoretical physicist Max Planck as an absolute frame of reference based on natural physical constraints rather than an arbitrary human-made measurement system like feet, inches, centimeters and meters. The Planck length is 1.6 times 10 to the minus 35 meters. To imagine this think of a dot that has the same diameter as a human hair, about 0.1 millimeters. This is about the smallest thing that we can see unaided. If that 0.1 millimeter dot were magnified to the size of the observable universe or 93 billion light years of it then the Planck length will be the size of a 0.1 millimeter dot in comparison. Down at this size and smaller we are into the so-called quantum foam where chaos reigns. The Planck length also marks the limit at which quantum gravity begins to have an effect and the laws of physics as we know them still work. Anything smaller than this is where our theories of space-time and general relativity as created by Einstein break down and become unworkable. If we tried to measure anything the size of a Planck length such as the strings in string theory the photon speed needed would be so high that the amount of energy required in such a small space would create a microscopic black hole and the more energy you put in the bigger the black hole will become. So there could be distances smaller than the Planck but we would need a theory of quantum gravity to make any sense of them which we don't currently have. And that's it we've reached the bottom of a rabbit hole covering 60 orders of magnitude from the size of the observable universe down to a point where it descends into chaos and we need new theories to try and figure out what's going on down there and yet everything in the universe that we know of including space-time itself is made from this stuff and therein lies the paradox. Trying to create the theory of everything, a theory that encompasses the very large with a very small has been the goal of theoretical physicists since Einstein but so far this has eluded the brightest and best including Einstein but who knows maybe someone out there watching this might be the person to find the answer and our sponsors of this video Brilliant can help you develop skills in critical and logical thinking and this Christmas you could give the gift of learning to maybe that special person. 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