Three Most Common Misconceptions About the Big Bang
The idea of an expanding and accelerating universe is a very hard one to fully visualize. We try anyway because that’s how humans make sense of ideas; visualizing is our way of trying to understand.
Nothing is more satisfying than thinking we understand our place in the universe. We don’t of course. At least not yet, but we’re getting closer. Walking our path towards understanding, especially when it comes to cosmology, is fraught with peril. We run the risk of getting too simplistic in our visualizations.
Below is a list of mistakes we make when thinking about the big bang. It comes from questions and comments I regularly receive after someone watches the Hubble Deep Field video.
- The Big Bang was an explosion. This is a very common idea, and it’s understandable because we talk of an expanding universe, and we commonly run the universe ‘backward’ in time to make sense of it at various stages in its history. Cosmologists also talk of a time when the universe was smaller than the head of a pin, with all matter and everything the universe is to become all contained in a singularity. The Big Bang is not an explosion, it is an inflation of space-time that is driven by the repulsive effect of dark energy (or vacuum energy - which may BE dark energy, but I digress). The best one can do with the explosion analogy is to think of the explosion as little explosions happening everywhere, all at once, throughout spacetime. AND, that it’s still going on.
- The universe is expanding INTO something. Almost immediately after you visualize that the universe is expanding, it’s very natural to ask, “What’s it expanding into?” As we’ve already established, all of spacetime is expanding, everywhere is getting bigger all the time. Note the word ‘everywhere’. Our backyard is getting bigger every minute, there is nothing outside the fence, at least that has ANYTHING WHATSOEVER to do with us. IF there is something outside of our expanding universe, we have no hope of ever measuring it or in any other manner interact with that ‘region’; the laws which govern our existence make it a worthless question.
- If the universe is expanding, so is everything in it. Again, it is SPACETIME that is expanding, not stars, planets, moons, galaxies, you, me (except for my waistline, but that’s not the universe’s fault), the living room, indivdual atoms, etc. The expansion affects the fabric of spacetime, anything bound by gravity or the other fundamental forces of nature do NOT follow this expansion. So you can forget about marketing that diet that puts people in a non-expanding bubble of spacetime which prevents further expansion.
When thinking about our bubble of spacetime we call the universe, you need to remember that we have no hope of getting any information from anywhere outside of it, that is, if there is one. So while you may be delirious with joy over the idea of extra dimensions, spacetime warps and other really cool sci-fi ideas, unless the laws of physics changes radically (or you become a scientologist), those ideas will always remain science fiction.
Besides, we have our hands full understanding the universe we can interact with, and the bitch of it is, over 95% of THAT won’t have anything to do with us.
Image Credit: psoup216
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POSTED IN: cosmology, dark energy
3 opinions for Three Most Common Misconceptions About the Big Bang
Tom
Apr 7, 2008 at 4:51 pm
The narrator in the linked Hubble Deep Field video repeats the figure “78 billion light years” a few times, while the currently accepted age of the universe is a mere 13.7 billion years. If we look that far away in opposite directions, we can say the visible universe is 27.4 billion light years across, at a maximum. I’m not sure where his figure came from.
Tony
Apr 7, 2008 at 5:01 pm
Hi Tom,
I’m the narrator and I got that number from a paper that used wmap data to get a topology and size of the universe. I had to revise that number to half that figure after I read another paper. I outlined all of this on my deepastronomy site:
http://www.deepastronomy.com/hubble-deep-field.html
rey
Apr 10, 2008 at 10:57 am
Hi Tony,
I’ve got a question about your big bang myths.
You state up there that the stuff IN the universe isn’t expanding along with the universe itself… but what makes us so sure of that?
My 5th grade science teacher demonstrated the concept of a vacuum to the class by putting a few marshmallows into a big glass vacuum-jar and sucked all the air out… no, not her, Tony… a pump! ;) Let’s say in this example she had actually managed to create a true vacuum, without rupturing the marshmallows - and they got to be about 3 inches in diameter each at the point of true vacuum. (whether or not this is acutally the size of the marshmallows in a vacuum, I don’t know, I’m not much into sweets). Suppose then, she was able to increase the size of the vacuum jar. Wouldn’t the marshmallows continue to expand to and eventually burst while compensating for the increasing void?
If the walls of the ‘bubble’ around the vacuum of spacetime are constantly getting larger as the universe expands, and vacuum is a constant, wouldn’t everything in it eventually expand over the billions of years (at varying rates depending on their composition and gravity) to compensate and maintain equilibrium for the increasing void of negative pressure and vacuum?
If even at an atomic level this you state this expansion is occuring. And I quote you from a prevoius post:
“… Why aren’t the galaxies, stars, planets, the atoms in my body, also flying apart? Shouldn’t we all be slowly disintegrating as space and time expands?
After all, there is space and time in between protons and electrons, isn’t that space increasing all the time as well?
The answer is yes, but there are other forces at work at closer distances that fight against the expansion of the cosmos.” (1)
So… if the space between protons and electrons is constantly expanding, everything else should be expanding, right?? And presumably at a steadily increasing rate, consistent with the expansion rate of the universe. Seems like, luckily for us, there’s enough matter in the universe to allow this expansion to happen on such a small scale that we don’t even notice. Or gravity does a better job at holding some things together while others ‘fly apart’ more easily (more dense, less willing to expand - less dense, opposite). Couldn’t the nuclear reaction that initially lights the stars and keeps them lit be at least partially, a result of this negative pressure and expansion of spacetime between the electrons and protons allowing fusion to take place?
Please follow up with your thoughts on this, Tony, as there is a little more to this, I would like to share with you at some time in the future - maybe in an e-mail.
Thank you for your time, Tony
- rey
(1) The Big Bang Was an Explosion OF Space, Not IN Space - http://www.astronomybuff.com/the-big-bang-was-an-explosion-of-space-not-in-space/
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