Research scientists rely on a few guidelines when trying to describe how nature and the universe in general work. Scientists almost always begin by looking for laws and theories.
What is the difference? A scientific law it can often be reduced to a mathematical statement, such as E = mc²; it is a specific statement based on empirical data, and its truth is usually limited to a certain set of conditions. For example, in the case of E = mc², c refers to the speed of light in a vacuum. Scientific law is often unobjectionable and it takes a lot of discoveries and also a paradigm shift for it to change.
For her part, one Scientific theory often seeks to synthesize a body of evidence or observations of particular phenomena. In general, though not always, it is a larger, testable statement about how natural phenomena operate. You can’t necessarily reduce a scientific theory to a concise statement or equation, but it does represent something fundamental about how nature works.
Both laws and theories depend on basic elements of the scientific method, such as generating a hypothesis, testing those premises, finding (or not finding) empirical evidence, and reaching conclusions. Eventually, other scientists must be able to replicate the results if the experiment is to become the basis of a widely accepted law or theory.
What is a scientific theory?
A theory is a set of accepted assumptions, propositions, or facts that attempts to provide a plausible or rational explanation of cause-effect (causal) relationships among a group of observed phenomena. The origin of the word theory (from the Greek thorós, spectator).
A theory is a plausible or scientifically acceptable general principle or body of principles offered to explain phenomena.
One theory is:
a: a hypothesis assumed for the sake of argument or investigation
b: an unproven assumption: conjecture
c: a body of theorems that presents a concise and systematic view of a topic
6 Examples of Scientific Theories
1. Light wave theory
In 1690, the scientist Christian Huygens published his wave theory of light. This theory was in contrast to the particle theory of light suggested by Isaac Newton and others.
Over time, different theories related to the composition and behavior of light have been proposed, modified, and abandoned. These include Newton’s corpuscular theory, Huygen’s wave theory, Maxwell’s theory of electromagnetic waves, and Planck’s quantum theory. Wave theory explained various characteristics of light, including phenomena such as color spectrum, diffraction, and polarization. But now we know that light has both particle and wave characteristics.
2. Theory of relativity
Albert Einstein’s theory of relativity remains an important and essential discovery because it forever changed the way we see the universe. Einstein’s greatest breakthrough was to say that space and time are not absolute and that gravity is not simply a force applied to an object or mass. Rather, the gravity associated with any mass, curves space and time itself (often called space-time) around it.
To conceptualize this, imagine that you are traveling the Earth in a straight line, heading east, starting somewhere in the northern hemisphere. After a while, if someone were to pinpoint your position on a map, it would actually be both east and south of your original position. That’s because the Earth is curved. To travel directly east, you must take into account the shape of the Earth and face slightly north. (Think of the difference between a flat paper map and a spherical globe.)
The space is more or less the same. For example, to the occupants of the shuttle orbiting Earth, it may appear that they are traveling in a straight line through space. In reality, the space-time around them is being bent by Earth’s gravity (as it would be with any large object with immense gravity, such as a planet or a black hole) causing them to move forward and appear that orbit around the Earth.
Einstein’s theory had tremendous implications for the future of astrophysics and cosmology. He explained a minor and unexpected anomaly in Mercury’s orbit, showed how starlight is bent, and laid the theoretical foundation for black holes.
3. Law of Gravity
We can take it for granted now, but over 300 years ago, Isaac Newton proposed a revolutionary idea: that any two objects, regardless of their mass, exert a gravitational force on each other. This law is represented by an equation that many high school students come across in physics class. It goes as follows:
F = G × [(m1m2)/r2]
F is the gravitational force between the two objects, measured in Newtons. M1 and m2 are the masses of the two objects, while r is the distance between them. G is the gravitational constant, a number currently calculated at 6.672 × 10-11 N m2 kg-2 [fuente: Weisstein].
The benefit of the law of gravity is that it allows us to calculate the gravitational attraction between any two objects. This ability is especially useful when scientists are, for example, planning to put a satellite into orbit or charting the course of the moon.
4. The theory of the evolution of species and natural selection
Now that we’ve established some of the fundamental concepts of how our universe began and how physics plays out in our daily lives, let’s turn our attention to the human form and how we came to be the way we are. According to most scientists, all life on Earth has a common ancestor. But to produce the immense amount of difference between all living organisms, some had to evolve into different species.
In a basic sense, this differentiation occurred through evolution, through descent with modification. Populations of organisms developed different traits, through mechanisms such as mutation. Those with traits that were most beneficial to survival, such as a frog whose brown color allows it to blend into a swamp, were naturally selected to survive; hence the term natural selection.
It is possible to expand on both theories in more detail, but this is the basic and groundbreaking discovery that Darwin made in the 19th century: that evolution through natural selection explains the tremendous diversity of life on Earth.
5. Big Bang Theory
How was our Universe created? How did it come to be the seemingly endless place we know today? And what will become of him in a few ages? These are the questions that have puzzled philosophers and scholars since the beginning of time, and have given rise to some pretty wild and interesting theories. Today, the consensus among scientists, astronomers, and cosmologists is that the Universe as we know it was created in a massive explosion that not only created most of the matter, but also the physical laws that govern our ever-expanding cosmos.
This is known as the Big Bang theory. For nearly a century, the term has been used by academics and non-academics alike. This should come as no surprise, as it is the most widely accepted theory of our origins. But what exactly does it mean? How was our Universe conceived in a massive explosion, what proof is there for this, and what does the theory say about long-term projections for our Universe?
The basics of the theory are quite simple. In summary, the Big Bang hypothesis states that all current and past matter in the Universe came into existence at the same time, approximately 13.8 billion years ago. At that time, all matter was compacted into a very small ball with infinite density and intense heat called the Singularity. Suddenly, the Singularity began to expand and the universe as we know it began.
Although this is not the only modern theory of how the Universe arose, for example, there is the Steady State Theory or the Oscillating Universe Theory, the Big Bang Theory is the most accepted and popular. The model not only explains the origin of all known matter, the laws of physics, and the large-scale structure of the Universe, but also explains the expansion of the Universe and a wide range of other phenomena.
6. Immune surveillance theory
The immune surveillance theory of cancer holds that everyone has had cancer in some way or another, as a healthy immune system fights off rogue cells as they appear. -Sallie Tisdale, Harper’s, June 2007