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Can science ever discover the absolute truth about reality? Is science absolute? Its truths and discoveries guide us toward the nature of reality, but we must always remain open-minded to revisions. existence of God The truth about reality is written on the face of the Universe itself, and can be discerned via the process of scientific inquiry. At least, that's the assumption we make, and it's been quite fruitful so far. But this, like all other scientific ideas, is always subject to being overturned with new observations and experiments. (Credit: adimas/Adobe Stock) Key Takeaways

In order for a hypothesis, idea, or even a fact or law to become a scientific truth, it must clear an immense standard of evidence and pass a series of scrutinous tests to get there. But what we call a "scientific truth" is very different from our colloquial idea of true vs. false or right vs. wrong. Although science always seeks the truth, none of its conclusions can ever be considered absolute. Nevertheless, despite this limitation, it's the best guide to reality that we have. 

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In many ways, the human endeavor of science is the ultimate pursuit of truth. By asking the natural world and Universe questions about itself, we seek to gain an understanding of what the Universe is like, what the rules that govern it are, and how things came to be the way they are today. Science is the full suite of knowledge that we gain from observing, measuring, and performing experiments that test the Universe, but it’s also the process through which we perform those investigations. Top Stories

It might be easy to see how we gain knowledge from that endeavor, but how do scientists arrive at the idea of a scientific truth? And when we do get there, how closely related to our notions of “absolute truth” are these scientific truths? What are the grounds upon which we, scientifically, determine something to be true or untrue?

When we’re speaking scientifically, the notion of a “truth” is something very different than how we colloquially use it in our everyday speech and experience. Here’s how to understand the scientific uses of the word truth, including what it does and doesn’t mean for our reality. One of the great puzzles of the 1500s was how planets moved in an apparently retrograde fashion. This could either be explained through Ptolemy’s geocentric model (left), or Copernicus’ heliocentric one (right). However, getting the details right to arbitrary precision was something neither one could do. Both models have little predictive power; they could not detail the orbital properties of a hypothetical additional planet the way a more concrete physical theory, like Newtonian or Einsteinian gravity, would later do. Credit: E. Siegel/Beyond the Galaxy

Let’s consider the following statement: “The Earth is round.” If you’re not a scientist (and also not a flat-Earther), you might think that this statement is unimpeachable. You might think of this as being scientifically true. In fact, stating that the Earth is round is a valid scientific conclusion and a scientific fact, at least if you contrast a round Earth with a flat Earth.

But there’s always an additional nuance and caveat at play. If you were to measure the diameter of the Earth across our equator, you’d get a value: 7,926 miles (12,756 km). If you measured the diameter from the north pole to the south pole, you’d get a slightly different value: 7,900 miles (12,712 km). The Earth is not a perfect sphere, but rather a near-spherical shape that bulges at the equator and is compressed at the poles. The diameter of the Earth at the equator is 12,756 km, while at the poles it’s only 12,714 km. You are 21 kilometers closer to the center of the Earth standing at the North Pole than you are at the equator. This difference is largely due to Earth’s rotation on its axis and shows up as an important effect in Earth’s gravitational field varying with latitude. Credit: NASA/GSFC/GOES-13/NOAA

To a scientist, this illustrates extremely well the caveats associated with a term like scientific truth. Sure, it’s more true that the Earth is a sphere than that the Earth is a disc or a circle. But it isn’t an absolute truth that the Earth is a sphere, because it’s more correct to call it an oblate spheroid than a sphere. And calling it an oblate spheroid isn’t the absolute truth, either. Featured Videos

There are surface features on Earth that demonstrate significant departures from a smooth shape like either a sphere or an oblate spheroid. There are mountain ranges, rivers, valleys, plateaus, deep oceans, trenches, ridges, volcanoes, and more. There are locations where the land extends more than 29,000 feet (nearly 9,000 meters) above sea level, and places where you won’t touch the Earth’s surface until you’re 36,000 feet (11,000 meters) beneath the ocean’s surface. From a depth of over 7,000 meters in the Mariana Trench, the submersible vehicle ‘Jiaolong’ works to image living plants and animals along the ocean floor in the western Pacific Ocean. The Mariana snailfish is the deepest-living fish in the world, extending all the way down to depths of 8145 meters. The Mariana Trench contains the deepest part of the world’s oceans. (Credit: SOI/HADES/University of Aberdeen (Dr. Alan Jamieson))

This example highlights a few important ways of thinking scientifically that differ from how we think colloquially.

There are no absolute truths in science; there are only approximate truths.
Whether a statement, theory, or framework is true or not depends on quantitative factors and how closely you examine or measure the results.
Every scientific theory has a finite range of validity: inside that range, the theory is indistinguishable from true, outside of that range, the theory is no longer true.

This represents an enormous difference from how we commonly think about fact vs. fiction, truth vs. falsehood, or even right vs. wrong. According to legend, the first experiment to show that all objects fell at the same rate, irrespective of mass, was performed by Galileo Galilei atop the Leaning Tower of Pisa. Any two objects dropped in a gravitational field, in the absence of (or neglecting) air resistance, will accelerate down to the ground at the same rate. This was later codified as part of Newton’s investigations into the matter, which superseded the earlier notions of a constant downward acceleration, which apply only to the surface of the Earth. (Credit: juliaorige/pixabay)

For example, if you drop a ball on Earth, you can ask the quantitative, scientific question of how it will behave. Like everything on Earth’s surface, it will accelerate downward at 9.8 m/s² (32 ft/s²). And this is a great answer, because it’s approximately true.

In science, though, you can start looking more deeply, and seeing where this approximation is no longer true. If you perform this experiment at sea level, at a variety of latitudes, you’ll find that this answer actually varies: from 9.79 m/s² at the equator to 9.83 m/s² at the poles. If you go to higher altitudes, you’ll find that the acceleration starts to slowly decrease. And if you leave the Earth’s gravitational pull, you’ll find that this rule isn’t universal at all, but is rather superseded by a more general rule: the law of Universal gravitation. The Apollo mission trajectories, made possible by the Moon’s close proximity to us. Newton’s law of universal gravitation, despite the fact that it’s been superseded by Einstein’s General Relativity, is still so good at being approximately true on most Solar System scales that it encapsulates all the physics we need to travel from Earth to the Moon and land on its surface, and return. (Credit: NASA)

As far as scientific laws go, this one is even more generally true. Newton’s law of universal gravitation can explain all the successes of modeling Earth’s acceleration as a constant, but it can also do much more. It can describe the orbital motion of the moons, planets, asteroids and comets of the solar system, as well as how much you’d weigh on any of the planets. It describes how the stars move around inside galaxies, and even allowed us to predict how to send a rocket to land humans on the Moon, with extraordinarily accurate trajectories.

But even Newton’s law has its limits. When you move close to the speed of light, or get very close to an extremely large mass, or want to know what’s occurring on cosmic scales (such as in the case of the expanding Universe), Newton won’t help you. For that, you have to supersede Newton and move on to Einstein’s General Relativity. An illustration of gravitational lensing showcases how background galaxies — or any light path — is distorted by the presence of an intervening mass, but it also shows how space itself is bent and distorted by the presence of the foreground mass itself. When multiple background objects are aligned with the same foreground lens, multiple sets of multiple images can be seen by a properly-aligned observer, or even an “Einstein ring” in the case of perfect alignment. If a transient event, like a supernova, occurs in the background galaxy, it will appear with time delays in the various images. Credit: NASA, ESA & L. Calçada

For the trajectories of particles moving close to the speed of light, or to obtain very accurate predictions for the orbit of Mercury (the Solar System’s closest and fastest planet), or to explain the gravitational bending of starlight by the Sun (during an eclipse) or by a large collection of mass (such as in the case of gravitational lensing, above), Einstein’s theory gets it right where Newton’s fails. In fact, for every observational or experimental test we’ve thrown at General Relativity, fro