[Veronica (OP)]

Is relativity a fact because isn't there something to do with uncertainty when considering any facts?

[Colin2B]

Is relativity a fact because isn't there something to do with uncertainty when considering any facts?

Yes, relativity is a fact.
There is always some uncertainty in measurements and observations which is why in science we are repeatedly testing and checking theories for consistency. Interestingly, relativity is one of the most consistent at being correct in its predictions.

[evan_au]

Is relativity a fact because isn't there something to do with uncertainty when considering any facts?

Galileo developed a somewhat different theory of gravity from most of his predecessors, based on experiments in his lab: That the distance traveled by a falling object increases as the square of the elapsed time. He knew that there was some uncertainty to do with air resistance. But his theory was valid (a fact) within the realm where he had tested it, in the lab.
- This law of motion is still taught in high school physics
- The error in Galileo's theory was that the strength of gravity gets measurably weaker if you get hundreds of kilometres from the Earth - which you can't detect if your lab is on the surface of the Earth.

Newton developed a somewhat different theory of gravity from Galileo, based on measurements of the motion of the planets: That objects follow the path of a conic section (circle, ellipse, parabola or hyperbola). He knew that there was some uncertainty to do with measurement of the position of the planets, and enormous uncertainty about the distance to the planets. But his theory was valid (a fact) within the realm where he had tested it, in the Solar System.
- Newton's laws of motion and law of universal gravitation is still taught in high school physics
- The error in Newton's theory was measurable within the Solar System, but only if you had centuries of accurate measurements of the motion of Mercury. This data was not available to Newton.

Einstein developed a somewhat different theory of gravity from Newton, based on deductions from the speed of light: That time is slowed in the presence of a gravitational field. Subsequent measurements had to deal with errors in measuring the position of stars during an eclipse, and uncertainty with the distribution of mass within the Sun. But his theory was valid (a fact) even beyond the realm where he had considered it, with application to black holes (as celebrated by the 2020 Nobel Prize) and the Big Bang.
- Einstein's relativity is still taught in university physics
- The error in Einstein's theory is that it falls down near a black hole. Without a convenient nearby black hole to study, the theoreticians can get little direction from experimenters.

Hawking developed a somewhat different theory of gravity from Einstein, based on deductions from quantum theory and the entropy of black holes. This is still a work in progress, beyond the death of Hawking.

I would say that Galileo, Newton and Einstein all discovered facts about the universe - which are accurate and incredibly useful within their applicable domain.
- Galileo & Newton didn't know the limits of their theory - these limits were only discovered long after their deaths
- Einstein & Hawking were both painfully aware of the limits of their theories. and spent the latter half of their lives trying (unsuccessfully) to resolve quantum theory & relativity.

[Bored chemist]

Relativity is an idea.
It is consistent with all the facts we know.

[alancalverd]

Be sure to distinguish between uncertainty (of measurements) and indeterminacy (a fundamental property, most significant in atomic and nuclear physics).

[evan_au]

Galileo, Newton and Einstein all discovered facts about the universe

I realize an asymmetry here - despite quoting Hawking as someone who improved on Einstein's Relativity, I didn't quote him as having discovered facts about the universe.

That is because the bar for promotion to a fact is that the predictions of the theory are verified by experimental results.
- Hawking predicted black hole evaporation
- But we have not yet been able to study a black hole closely enough to verify the prediction of black hole evaporation

In contrast, the existence of a more complete theory does not demote a simpler theory to non-fact.
- The simpler theory remains valid within its original domain, as a "special case" of the more general theory
- And it is often useful for making the calculations simpler (eg in high school)
- Provided that the users are aware that there is a more complete theory, and when they should start applying the more precise calculation...

[Bored chemist]

Be sure to distinguish between uncertainty (of measurements) and indeterminacy (a fundamental property, most significant in atomic and nuclear physics).

We might need to add ambiguity to that lis- or we might not.

[Veronica (OP)]

Is relativity a fact because isn't there something to do with uncertainty when considering any facts?

Yes, relativity is a fact.
There is always some uncertainty in measurements and observations which is why in science we are repeatedly testing and checking theories for consistency. Interestingly, relativity is one of the most consistent at being correct in its predictions.

Can we predict everything ?

The weather report isn't always accurate .

[evan_au]

Can we predict everything ?

In physics, if you have accurate measurements of all the components in a system, you can make fairly accurate predictions of what they will do.
- For large systems (like planets), you can predict their motions millions of years into the future (barring outside influences)
- But for "small" systems, quantum theory says that you can't measure the system accurately.

Some recent Nobel prizes in chemistry were awarded for the ability to predict the shape and behavior of simple molecules.

Biology is not a simple system. And it is not composed of small molecules.

The weather is not a simple system, either; just collecting information about what the weather is right now is a major challenge for a weather bureau. At the current state of the art, with sufficiently good data, sufficiently good models of some region, and a sufficiently powerful computer, it is possible to get a rough idea of the weather in 12 days.
- But weather is a "chaotic" system, and any errors in your measurements grow exponentially, quickly overwhelming the prediction.

So there are fundamental limits on how well we can predict the future.
- We can chip away at these limits by collecting more data, and by applying more powerful computers (and even quantum computers, some day)
- But the underlying limits will remain

[Colin2B]

As @evan_au says, weather is a chaotic system with lots of variables, but despite that we do find forecasts very useful.
I use the forecasts quite regularly and they give me a good idea what to expect. Often if the forecast is wrong for my immediate position I can see it’s because a depression has passes eg a few miles further north than predicted. However, my knowledge of that predicted route allows me to watch cloud formations, wind direction at surface and high, and pressure readings to help me understand where the depression is actually headed and what change of forecast that implies. Knowing how the weather, particularly wind, will change locally over the next few hours is far more use to me than a general “SE of England with get scattered showers and cloudy”.
So even something that is wrong can be really helpful if you know why it’s wrong.

[alancalverd]

With my pedant hat on, I'd say that relativity isn't a fact but a consistent, explanatory, and so far adequately predictive, model of observed facts.

It fits very neatly into the central part of "observe, hypothesise, test" and has survived all the tests up to date, so counts as "scientific knowledge" - the residue of explanatory and predictive hypotheses that have not been disproved by observation.

[evan_au]

Quite often our predictions are foiled by a variable we couldn't measure, or didn't think to measure.

Part of the art in science is knowing which variables are important in a given situation, and which variables can be safely ignored.