WhatHubble convincingly demonstrated by seeing the motion of those galaxies is thatthe universe is expanding.
Theoretically,an expanding universe must have started from a single point. By measuring howfast the universe is expanding, astronomers calculated backwards and figuredout when it burst into life.
Peopleask the question,“Howdo you know that the universe is 13.7 billion years old?” I mean, smartypants, you weren’t there 13.7 billion years ago. Well, when you watchtelevision on videotape, you hit the stop button when you see an explosion, andyou could run it backwards and see when it actually took place. The same thingtakes place with cosmology. We can run the videotape backwards and thencalculate when it all came from a cosmic explosion.
Youdon’t have to be an astronomer to look back in time. If you gaze up at thenight sky, you’re seeing stars that are millions of light years away, meaningit took the light from those stars millions of years to get here. So if youlook far enough, you should be able to see the beginning of the universe. Namedfor the ground-breaking astronomer, the Hubble Space Telescope, allows us tolook deep into the universe, back in time and closer to the moment of the bigbang. But for scientists, winding back the clock to the big bang was only thefirst step.
Whenpeople first hear about the big bang theory, they say：“Well, where didit take place? It took place over there? It took place over there? Where did ittake place?”Actually,it took place everywhere, because the universe itself was extremely small atthat time.
Theseare only some of the most abstract and difficult concepts there are. So here’sa mired-bender: What came before the big bang?
Thephilosophers in ancient times used to say,“How could something arise from nothing?”And what’samazing to me is that the laws of physics allow that to happen. And it meansthat our whole universe, everything we see, everything that matters to ustoday, could have arisen out of precisely nothing.
It’sone of the biggest hurdles to understanding the big bang. First, you have tobuy into the premise that something was created out of nothing.
It’simpossible to describe the moment of creation in human language. All we know isthat from what may have been nothing, we go to a state of almost infinitedensity and infinite temperature and infinite violence.
Understandinghow nothing turned into something may be the greatest mystery of our universe.But if you understand that, you start to understand the big bang, when time andspace began and a great big explosion created everything. At the dawn of time,the universe explodes into existence, from absolutely nothing into everything.But everything is actually a single point, infinitely small, unimaginably hot,a super dense speck of pure energy. The big bang was so immense that it broughtinto existence all of the mass and all of the energy contained in all of the400 billion galaxies we see in our universe, in a region smaller than the sizeof a single atom. The entire observable universe was a millionth of a billionthof a centimeter across at that time. Everything was compressed into anincredibly hot, dense region.
It’snot even matter yet, just a point of raging energy. It was the beginning of theuniverse and everything in it.
Everythingwas simple. All the forces that we know about today were one and the same. Theuniverse was amorphous. It had so structure.
Inthat instance of creation, all the laws of physics, the very forces thatengineer our universe began to take shape. The first force to emerge wasgravity. The fate of the universe, its size, structure, and everything in itwas decided in that moment. Carlos Frank studies how gravity shaped theuniverse by creating artificial universes in this supercomputer. He gives eachone a different amount of gravity. The first one he tried had too little,resulting in, well, nothing.
Gravityhas shaped our universe. But if gravity was weaker than it is, we would have avery boring universe in which everything would by flying apart so fast thatthere would be no galaxies forming.
Next,he programmed a universe with too much gravity.
Ifgravity was stronger than we think it is again, we’ll end up with a faileduniverse. Everything will end up in black holes. It has to be just so, it hasto be just right.
Luckyfor us, the big bang got it just right, the perfect amount of gravity. In theturmoil of forces after gravity emerged, still a fraction of a second after thebig bang, a Shockwave of energy erupted and expanded the universe in alldirections at incredible speed.
Allof space expanded by an unbelievably large factor in a fraction of a second. Wethink that in less than a millionth of a millionth of a millionth of amillionth of a second, space expanded by a factor bigger than a million,million, million, million times.
Andfor the record, that’s faster than the speed of light. But wait, doesn’t thatbreak one of the laws of physics?
Evenschoolchildren know that, quote, you can't go faster than the speed of light. Butactually, there’s a loophole there. You see, nothing can go faster than light, nothingbeing empty space.
Don'tworry, this idea gives even the best minds in science a headache. But it'scritical to understanding the early universe.
