Brian Cox
speaker
1,719 appearances
13 recordings
8 series
first heard Oct 2024
last heard 16 Jun
Brian Cox’s voice in public audio — every appearance, attributed to the second.
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recordings per month · last 12 monthsRecordings per month over the last 12 months — 9 in all, peaking in Jun 2026 with 3.
Appearances
You start with a theory and you make a load of observations and you can infer things and you get a consistent picture. But... very importantly, until you find it, until you really find that particle, then you don't know, right? So that's a good question.
Yeah. And we've inferred it. So you might say, how do you know it's there? You know, which is a good question, right? I mean, if we have not detected this stuff, how do you know? And it's from Einstein's theory, really. So it's from gravity. It's from looking at the way that galaxies rotate and the way that these sound waves move through the early universe and the way that the universe expands.
Because the way the universe expands is related to the stuff that's in the universe. So we can weigh the universe and find out what kind of different things are in there by looking at the way it's expanded and how that expansion history has changed over time. So what you do with science, which is why it's true that you can criticize any one bit of it, and people will.
So online you'll see in the comments under this, there'll be people saying, what about this, what about this, what about this? And it's true that you can pluck away and pick away any piece of it. But the way it tends to work is when you have this kind of consensus view of something, it's because you have multiple observations that all fit a particular hypothesis.
And by changing one of them, by changing the explanation of one of them, you tend to mess the whole other thing up. You mess the wider description of multiple phenomena up. You mess it all up. So it's quite hard to find other theories at the moment that will fit all of those different observations. I mean, another example would be the age of things.
It's interesting that you can look at, we can measure the age of the Earth, right? And you measure it from geological processes, radioactive dating and so on, and you can kind of measure the age of the Earth. You can measure the age of the sun in a different way. You can measure it by looking at what's called helioseismology. So you can measure how much helium is in the core of the sun.
And the sun shines by making helium from hydrogen. So by measuring the amount of helium in the core, by looking at basically sound waves, it's like an earthquake that sunquakes. You can measure how much helium is in there so you can get an estimate of the age of the sun. And then you can get an estimate of the age of the universe by measuring how it's expanding and using Einstein's theory.
The fact that they all fit with the picture of a universe that's 13.8 billion years old, a sun that's 4.5 billion years old, a planet that's 4.5 billion years old, the fact that it all fits is quite an intricate model. And so you could say, well, I argue with the measurements of the age of the Earth. Maybe I don't like the radioactive dating or something, and people will say that.
But the thing is, it's a consistent picture with multiple different observations. And same with dark matter. So the standard model of cosmology is you have, as I said, about 5% matter, 25% dark matter, 70% dark energy. It might be wrong, but it fits loads of different independent observations. So it's a consistent picture.
There are theories that people try to build where you modify our theory of gravity. So many of these observations, not all of them, so the cosmic microwave background are different observations, but many of them depend on gravity and how gravity works, Einstein's theory of general relativity. So you could try to modify that theory to say, well, our observation's wrong.
Maybe, because the way we measure how the expansion of the universe is, is to look at light from supernovae is one way, and see how it's stretched over time. Because the light, let's say you have a supernova, and it happened a billion years ago, then the light has been traveling for a billion years across the universe.
And so the universe has been expanding for a billion years, so the light will be stretched. And so you can measure how much stretch there is. You just measure the color of the light from the supernova. So you can argue that maybe if you go for light that's been traveling 12 billion years across the universe, then maybe there was something different. Maybe the light was emitted a bit different.
Maybe the speed of light changes over time or something. So you can invent theories that would allow you to change the data or the interpretation of the data. But what you always find, I think it would be fair to say, is that you can change a theory and explain one bit, but all the wheels come off the other bits. Got it. So that's why it's quite difficult.
Yeah. So it fits. Yeah. But then there are some mysteries. Not least, what is this stuff? Right. And so until you know what it is, you don't have a complete theory.
Yeah. Yeah. And so that's what I love about. One of the things I love about science is it often gets presented, you know, because I talk about science a lot in public and it can often seem arrogant. I think it can seem, you know, like these people are saying, well, this is the way the world is. And you might say, well, you know, how are you to say this?
The thing I like about it, personally, and the reason for its success, is that really you have to be delighted when you're wrong. It's the key to science. It's been said many times, Richard Feynman, the great physicist, said it. If your goal is to understand nature, so that's what you want to do, So you've not got an ego or anything. You don't want to prove right. You just want to understand.
Then being wrong. So if this idea of dark energy and dark matter turns out to be wrong, all scientists or good scientists will be absolutely delighted because it'd be tremendously exciting that we'd ruled out this picture. It'd be great to rule out this picture. So there isn't such a thing as dark matter. And dark energy. It's all nonsense.
We were barking up the wrong tree, looking in the wrong direction. It's something else, which should be more wonderful, undoubtedly, than that theory that we have. So I think it's a humble pursuit, ultimately, science. And that's the reason for its success, because you're just trying to understand how things work. You're not trying to, you know, you shouldn't be anyway.
Good scientists are not trying to be the person that got it right. You're not trying, you know, you're not trying to do it. There's obviously human failure. Everyone's got fragility and everyone's human, you know, an ego. But ultimately, you're just trying to understand how things work.
Yeah. So we had one of the reasons we built that telescope was to what it does, because it can see very distant things and because light travels at a finite speed, the further out into the universe you look, the further back in time you're looking.
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