In many ways, the human search for science is the ultimate search for truth. By asking the natural world and the universe questions about themselves, we try to understand what the universe is like, what rules govern it, and how things got to be the way they are today. Science is all the knowledge we gain by observing, measuring, and conducting experiments that test the universe, but it is also the process by which we conduct these investigations.
It may be easy to see how we gain knowledge from this effort, but how do scientists arrive at the idea of scientific truth? And when we get there, how closely related are these scientific truths to our notions of "absolute truth"? What are the bases on which we scientifically determine if something is true or false?
When we speak scientifically, the term "truth" is very different from what we use colloquially in our everyday language and experience. Here's how to understand the scientific use of the word truth, including what it means and what it doesn't mean for our reality.
One of the great mysteries of the 16th century was the apparent retrograde motion of the planets. This could be explained by Ptolemy's geocentric model (left) or Copernicus' heliocentric model (right). However, getting the details right with arbitrary precision would require theoretical advances in our understanding of the rules underlying the observed phenomena, leading to Kepler's laws and eventually Newton's theory of universal gravitation.
Consider the following statement: "The earth is round." If you are not a scientist (and you arenot flat earth), one might think that this statement is unquestionable. You might think that this is scientifically true. In fact, the statement that the earth is round is a valid scientific fact and conclusion, at least when comparing a round earth with a flat earth.
But there is always an additional nuance and caveat at play. If you were to measure the diameter of the earth across our equator, you would get a value: 7,926 miles (12,756 km). If you were to measure the diameter from the North Pole to the South Pole, you would get a slightly different value: 7,900 miles (12,712 km). The earth is not a perfect sphere, but rather a nearly spherical shape that bulges out at the equator and is compressed at the poles.
Planet Earth seen in its entirety (as much as can be seen at one time) from the GOES-13 satellite. In this image, the planet may appear perfectly spherical, but its equatorial diameter is slightly larger than the diameter of its pole: Earth looks more like an oblate spheroid than a perfectly round sphere.
For a scientist, this nicely illustrates the caveats associated with a concept like scientific truth. It is certainly more true that the earth is a sphere than that the earth is a disk or a circle. But it is not an absolute truth that the earth is a sphere, because it is more correct to call it a flattened spheroid than a sphere. And calling it an oblate spheroid is not the absolute truth either.
There are surface features on Earth that show significant deviations from a smooth shape, such as a sphere or oblate spheroid. There are mountain ranges, rivers, valleys, plateaus, deep oceans, trenches, ridges, volcanoes, and more. There are places where the earth extends more than 29,000 feet (almost 9,000 meters) above sea level and places where you don't touch the earth's surface until you are 36,000 feet (11,000 meters) below the sea. sea level.
From a depth of more than 7,000 meters in the Mariana Trench, the Jiaolong submersible is working to image living plants and animals along the seafloor in the western Pacific Ocean. The Mariana snailfish is the deepest living fish in the world, with depths of 8,145 meters. The Mariana Trench contains the deepest part of the world's oceans.
This example highlights some important types of scientific thinking that differ from our everyday thinking.
- There are no absolute truths in science; There are only approximate truths.
- Whether or not a statement, theory, or framework is true depends on quantitative factors and how closely you examine or measure the results.
- Every scientific theory has a limited range of validity: within this range the theory is indistinguishable from the truth, outside this range the theory is no longer true.
This is a big difference from how we commonly think of fact vs. fiction, truth vs. falsehood, or even right vs. wrong.
According to legend, the first experiment showing that all objects fall at the same speed, regardless of their mass, was performed by Galileo Galilei on the Leaning Tower of Pisa. Any two objects falling into a gravitational field will accelerate toward the ground at the same velocity in the absence (or neglect) of air resistance. This was later codified as part of Newton's studies of matter, replacing earlier notions of constant downward acceleration that applied only to the earth's surface.
For example, if you drop a ball on the ground, you can ask the quantitative and scientific question of how it will behave. Like everything on Earth's surface, it is accelerating downward at 9.8 m/s² (32 ft/s²). And that's a great answer because it's more or less true.
In science, however, you can begin to look deeper and see where that approach no longer holds. If you perform this experiment at sea level at different latitudes, you will find that this answer actually varies: from 9.79 m/s² at the equator to 9.83 m/s² at the poles. As you get to higher altitudes, you will find that the acceleration slowly decreases. And when you leave the gravitational attraction of the earth, you will find that this rule is not universal at all, but is replaced by a more general rule: the law of universal gravitation.
The trajectories of the Apollo mission, made possible by the proximity of the Moon to us. Newton's law of universal gravitation, even though it has been superseded by Einstein's general theory of relativity, is still good enough to be approximately true on most scales of the solar system that contains all the physics that we need to know about Earth in order to travel to the moon and land on its surface and return.
As far as scientific laws are concerned, this applies even more generally. Newton's universal law of gravitation can explain all the success of modeling the acceleration due to gravity as a constant, but it can do much more. You can describe the orbital motion of the solar system's moons, planets, asteroids, and comets, as well as how much you would weigh on any of the planets. It describes how stars move in galaxies and even allowed us to predict, with remarkably accurate trajectories, how to send a rocket to take humans to the moon.
But even Newton's law has its limitations. If you're traveling close to the speed of light, or getting very close to an extremely large mass, or want to know what's going on on the cosmic scale (as in the case of the expanding universe), Newton won't help you. For that you need to replace Newton and move on to Einstein's general theory of relativity.
An illustration of gravitational lensing shows how background galaxies, "or any light paths," are distorted by the presence of intermediate mass, but also shows how space itself is bent and distorted by the presence of primer mass. flat. When multiple background objects are aligned to the same foreground lens, a properly aligned viewer can view multiple sets of multiple images.
For the trajectories of particles moving close to the speed of light, or for very accurate predictions of the orbit of Mercury (the closest and fastest planet in the solar system), or for the gravitational bending of light from stars by the Sun (during a solar period). eclipse) to explain. or through a large buildup of mass (as in the case of gravitational lensing above), Einstein's theory picks up where Newton's theory fails. In fact, all of the observational or experimental tests we've put on general relativity, from gravitational waves to space frame crawl itself, have passed with flying colors.
Does this mean that Einstein's general theory of relativity can be considered a scientific truth?
If you apply it to these specific scenarios, absolutely. But there are other scenarios we can apply it to, all of which have yet to be adequately tested, where we fully believe that there will be no quantitatively accurate predictions.
Even two merging black holes, one of the strongest sources of a gravitational signal in the universe, leave no observable signature for quantum gravity to probe. For this we need to set up experiments that investigate the strong field regime of relativity, i. h near the singularity, or that take advantage of ingenious laboratory setups.
There are many questions we can ask about reality that require us to understand what happens where gravity is important or where the curvature of spacetime is extremely strong: exactly where Einstein's theory wants it to be. But if the distance scales you're thinking of are also very small, you expect quantum effects to be important as well, and general relativity can't explain them.This includes questions like the following:
- What happens to the gravitational field of an electron when it passes through a double slit?
- What happens to the information of the particles that make up a black hole when the final state of the black hole is to decay into thermal radiation?
- And how does a gravitational field/force behave in and around a singularity?
Einstein's theory will not only answer these answers incorrectly, it will offer no reasonable answers. We know that in these regimes we need a more advanced theory, like B. a valid theory of quantum gravity that tells us what will happen in these circumstances.
Bits of information proportional to the surface of the event horizon can be encoded on the surface of the black hole. As the black hole decays, it decays into a state of thermal radiation. Whether or not this information survives and is encoded in the radiation, and if so how, is not a question our current theories can answer.
Yes, the masses on the Earth's surface are accelerating downward at 9.8 m/s², but if we ask the right questions or do the right observations or experiments, we can find out where and how this description of reality is no longer a true one. good approximation to the truth. is . Newton's laws can explain this phenomenon and many others, but we can find observations and experiments that show us where even Newton falls short.
Even replacing Newton's laws with Einstein's general theory of relativity leads to the same story: Einstein's theory can successfully explain everything that Newton's can, plus additional phenomena. Some of these phenomena were already known when Einstein formulated his theory; others had not yet been tested. But we can be sure that even Einstein's greatest achievement will one day be obsolete. If this is the case, we assume it will happen in exactly the same way.
Quantum gravity attempts to combine Einstein's general theory of relativity with quantum mechanics. Quantum corrections to classical gravity are visualized as loop diagrams, like the one shown here in white. If you add gravity to the standard model, the symmetry that CPT describes (the Lorentz symmetry) can become only an approximate symmetry that allows injury. However, to date no such experimental lesions have been observed.
Science is not about finding the absolute truth of the universe. No matter how much we want to know what the fundamental nature of reality is, from the smallest subatomic scales to the largest cosmic scales and beyond, science cannot provide. All our scientific truths are preliminary, and we must recognize that they are only models or approximations of reality.
Even the most successful scientific theories imaginable are, by their very nature, limited in scope. But we can theorize whatever we want, and if a new theory meets the following three criteria:
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- achieves all the achievements of the prevailing pre-existing theory,
- succeeds where current theory is known to fail,
- and makes novel predictions for hitherto unmeasured phenomena, other than prior theory, that eventually pass critical observational or experimental tests,
will replace the current one as our best approximation to scientific truth.
All of our cosmic history is well understood theoretically, but only because we understand the gravitational theory behind it and because we know the current expansion rate and energetic composition of the universe. We can trace the timeline of the universe with exquisite precision, despite the uncertainties and unknowns surrounding the beginning of the universe. From cosmic inflation to the dominance of dark energy today, the outlines of our entire cosmic history are known.
All of our current scientific truths, from the Standard Model of elementary particles to the Big Bang, dark matter and dark energy, cosmic inflation, and beyond, are only tentative. They are extremely accurate in describing the universe and succeed in regimes where all previous frameworks have failed. However, they all have limitations on how far we can extend their implications before we reach a point where their predictions no longer make sense or end up not describing reality. They are not absolute truths, but approximate, provisional ones.
No experiment can ever prove that a scientific theory is true; we can only show that their validity does or does not extend to the regime in which we test them. The failure of a theory is actually the ultimate scientific success: an opportunity to find an even better scientific truth that approximates reality. Anytime we find our current understanding insufficient to explain everything that's out there, yes, it's wrong: wrong in the best way imaginable.