Inside the Search for Extra Dimensions, with Lara Anderson
A string theorist walks a Daily Show comedian through the hardest unsolved problem in physics — why the math only works in ten dimensions, why gravity leaks, and whether dimensions are even real.
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Anderson explains that string theory requires ten dimensions because quantum anomalies — bookkeeping errors that break conservation laws at the quantum level — cancel out exactly only when the theory is formulated in ten dimensions.
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String theory requires exactly ten dimensions because quantum anomalies — which break conservation laws — cancel out precisely only at D equals ten.
Anderson says calling strings one-dimensional is 'a cheat'; they are better described by a two-dimensional world sheet, and the theory also includes higher-dimensional membranes.
Experiments at the LHC set bounds on extra dimension size: if they were large, mass and energy would visibly disappear into them during particle collisions, which is not observed.
Anderson suggests gravity may be weaker than other forces because it can leak into extra dimensions, diluting it — and says dark matter from an adjacent universe is a fair but unconfirmed hypothesis.
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Either that solution is not waiting for us, or it's too hard for our species to figure out, or the string theorists working on it are just too dumb — and we need all of the above.
Anderson lists the only three explanations for string theory's failure to unify physics, then concedes all three may apply simultaneously.
In context
that's fair, right? >> Yeah. We're trying to describe all the forces and particles that we see in nature. >> Okay. And you haven't done it yet. So >> this is true. Either that solution is not waiting for us or it's too hard for our species to figure out or the strength theorists working on it are just too dumb to to figure it out and we need all OF THE ABOVE. I MEAN ACTUALLY WHAT YOU JUST DESCRIBED there this this question of like you know where's this going am I going to make a breakthrough is it worthwhile that's something that researchers in any form of research really have to ask
Either that solution is not waiting for us, or it's too hard for our species to figure out, or the strength string theorists working on it are just too dumb to to figure it out — and we need all of the above.
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These quantum anomalies cancel exactly when you have 10 dimensions — that's where the theory becomes robust, rigid, and starts making predictions. That's where D equals 10 comes from.
Ten dimensions are not arbitrary; anomaly cancellation forces that number as the unique point where string theory becomes self-consistent and predictive.
In context
line of research. And what they found is that all of this quantum uncertainty, this sort of wiggling and violation of these these principles that we think should hold magically cancels out when you have 10 dimensions. Um these quantum anomalies cancel exactly. So the theory becomes really robust and really rigid. It starts making all these, you know, sort of theoretical structure and predictions at that point. And then you can ask questions. You can say, well, what does this predict? What does it mean? Can it work? And we're still
dimensions. Um These quantum anomalies cancel exactly So when you have 10 dimensions — that's where the theory becomes really robust, and really rigid, It and starts making all these, you know, sort of theoretical structure and predictions. That's where D equals 10 comes from.
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Gravity could seep into those other directions and be diluted compared to the rest of the forces — which is one explanation for why gravity is the weakest force we know.
Extra dimensions offer a geometric mechanism that would explain one of physics' deepest puzzles: why gravity is so much weaker than other forces.
In context
people have considered is you know if some forces in nature interact with the extra dimensions and some don't um that could explain why gravity is weaker than the other forces for example. for example, if you know, gravity could seep into those other directions, it's sort of diluted compared to the rest of the forces. So, there are lots of of potential experiments that could in our lifetimes um shed light on those scales. In string theory, I'd say the the best bet is actually going to be not that, but a more indirect argument either for
know, Gravity could seep into those other directions it's sort of and be diluted compared to the rest of the forces — which is one explanation for why gravity is the weakest force we know.
Receipt
The measurement of time is embedded in repeated phenomenon. If you go to a world where nothing repeats, there would be no measurement of time.
Repeated phenomena are the prerequisite for any clock, so time measurement is a physical relationship, not just a number we read off.
In context
>> Wait, explain that to me. You have >> Earth rotates once a day and it keeps doing it. Earth goes around the sun once a year and it keeps doing it. We have we have a day and a year. >> Okay. We got a clock that that we got atoms that vibrate. Everything is repeating. >> The measurement of time is embedded in repeated phenomenon. >> So if you go to a world where nothing repeats, there would be no measurement of time. >> Doesn't mean there isn't time still existing, but you couldn't measure it in any meaningful way. Are we good with
The measurement of time is embedded in repeated phenomenon. >> So If you go to a world where nothing repeats, there would be no measurement of time.
Receipt
Dimensions could just be a construct — a tool for how we try to describe physics and make predictions. We don't measure forces; we just measure acceleration. 'Force' is a construct too, and a very useful one.
Dimensions belong to the same category as force—useful human constructs for organizing predictions, not directly observed features of reality.
In context
of freedom of how things move in our universe. And so that's where we, you know, you see that you can move forward, backward, side to side, up and down, and those are different. But labeling them as dimensions, labeling them as different, that's just a tool for how we try and describe physics and make predictions. Just like things like, you know, a force when you say something pushes on something else, that's a a construct, too. Turns out a very useful one. Um, but, you know, we don't measure forces, we just measure acceleration. So yeah, I I would say it could be viewed
Dimensions labeling them as different, that's could just be a construct — a tool for how we try and to describe physics and make predictions. We don't measure forces; we just like things like, you know, a measure acceleration. 'Force' when you say something pushes on something else, that's a is a construct too, Turns out and a very useful one. Um, but, you know, we don't measure forces, we just measure acceleration.
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