Can you tell us what the difference is between special and general relativity?

There's various differences, but the simplest one, the simplest differences that special relativity is relatively easy.

And general relativity is incredibly difficult.

Special relativity is to do with the idea that the speed of light is constant no matter which frame of reference you're in.

So if you're traveling on a train, the speed of light you'll measure will be the same as if you're stationary.

I started then realized that there's something funny in a gravitational field on Dhe.

It took him ages to work this out, but I mean, this was the greatest piece of work he ever did so again, classic example of people uses to talk about being in a lift, and you can't actually tell if you feel feel yourself pushed to the floor of the lift.

You can't tell if that's because the lift is accelerating upwards or whether it's because the pull of gravity is pulling you down with onto the floor.

The lift and general relativity is all about the equivalent of those two things special relativity.

You can't consider accelerations it all.

Everything has to be traveling at constant speed.

So you don't have these reference frames that accelerate.

You don't have things like lists accelerating.

You have to think about just things traveling constant speed.

And he realized that mass was equal to energy on energy.

Could be attracted to anything which has a math through the gravitational force.

So the idea was put in his head.

That light doesn't actually travel in a straight line at the speed of light.

It can actually travel in a curved path because it could be bent by the gravitational field.

And so he tried to incorporate into the theory of relativity the idea that you could have a distortion of space time and the light will then travel in the curved path on.

That's the field of general relativity.

Special relativity came first.

Einstein came up with special relativity on then.

Actually, you spent quite a long time dealing with general relativity coming up with general relativity.

And the reason is that actually, the mass you need to do special relativity is actually pretty trivial.

You need addresses theory in the square on the hypotenuse is equal to the sum of the squares on the two sides.

You know that you know all the math.

You really need to do special relativity.

Where is general relativity?

The matter you need is truly scary.

I look at all the math for that, and it's really frightening.

But he then predicted what should be seen.

And in about 1919 there was an expedition with Eddington that confirmed his predictions.

They were slightly suspect experiments, but this made a big headlines at the time because here, with German science being vindicated by British experiments, and so he became the first superstar of science because that to put things in perspective, we can teach special relativity activity to first year undergraduates on They love it because it doesn't use any mess that they haven't already seen.

But the results you get out of it are truly astounding.

The difficult thing about special relativity isn't the masses understanding what comes out of that matter at the end.

Where is general relativity?

Finally, undergraduate still struggle with it special is in designed for situations where there is no mass around and just like going around in a straight line.

General then tries to incorporate.

I cooperate the ideas of special relatives, the inner gravitational field.

So just general relativity sort of takes special relativity into the real world.

Yes, that's perfect.

That's a perfect also.

If you could change the value of any constant, what would it be and why?

I mean, it would be fun to see what would happen if I change the value of either of planks.

Constant news.

Constant.

I mentioned what the damage potential Turkish changing Newton's constant could be.

Don't change any of them, because if we change him too much, it may be very, very unfavorable for life times constants affecting things on the very small Newton's constant affecting things on the very large and so slight modifications of these could have dramatic effects on either of these scales.

So I think the world is not perfect, but let's not fiddle around with them too much.

I think we better even ask that question.

Uh um, well, it's tough because they're all combined with other things.

So you change one and you don't really know how the other things would get affected.

I guess it would probably be planks constant just because blanks constant is the thing that kind of dictates or quantum mechanics in the universe.

And the quantum universe is such a bizarre thing.

You know, this strange property that particles can be waived like and a single particle simultaneously passed through two different opportunities and also the weird things.

The trouble is, the only happens on the tiny microscopic scale.

So you never get to see it.

Probably clanks constant again, because then you could very hard waving Lee.

If you if we've talked blanks, Constance said it would be in 6.63 by 10 to the minus 34 June 2nd.

If we made it much, much larger than this sort of weird quantum effects that we experience right down at the scale of atoms and molecules would become apparent in the visible world.

See, I I don't think I'd go messing around with a good thing.

I think the universe is pretty interesting the way it is.

It's pretty fine tuned.

Um, so if we start messing about with something, even if we could do that, um, it's probably likely that we'd obliterate ourselves out of existence if I could mess around with thanks, constant.

So I could actually see some of those weird quantum effects, but actually just in the lab or on the table in front of me, that would be a great experiment to be able to do, being able to tow, walk through walls or tunnels, three walls and defrocked and interfere.

That might possibly not be the greatest thing.

It would certainly lead to a very different world, a very different set off physics.

If I could change anything, really, it would be directs constant use eight with a little line through it.

If you come across, that is planks constant divided by two pi.

Andi, I would put everything in those units and drive everybody else crazy because they Then you get these 10 to the 30 fours coming all over the place, or the ratio between the gravitational force and the electromagnetic force.

It's some ridiculously huge number, um, and and we don't know why or how so if that changed a bit, it would it would change whether or not stars could form and what their lifetimes would be So sure Shake things up.

Change that race.

You.

There are some people.

By the way, I believe the constants are not constant on that.

They have been changing over time On DSO there are lots of observational tests to see whether these constants in particular news constant on the charge of the electron changes.

That will be fun.

Change the charge on the electron a bit and see what happens to atoms if they get a bit bigger.

So, yeah, I'll stick with the universe as it is with fundamental constants that we have Thanks.