10 Scientific Facts That Sound Completely Made Up

1. Time dilation occurs when you are accelerated to high speeds or when you spend time in a large gravitational field. The first is from special relativity and the second is from general relativity. We know that time dilation in accelerated particles is real because elementary particles take longer to decay when they are accelerated to high speeds. We know that time dilation occurs in gravitational fields because GPS satellites have to take into account the difference in the way that time passes on the surface of the Earth compared to in orbit around it.

2. There is no beginning of time. Yes, the universe has only existed for 13.8 billion years but there is a catch: imagine going back in time in a time machine to "witness" the big bang. If you go back that far in time then the universe would be tending towards a singularity. However, a Stephen Hawking points out, if all the matter in the universe were concentrated on a single point it would be like a black hole and time would slow down to the point where you could continue to go back in time but never reach a beginning.

3. The Many Worlds Interpretation of Quantum Mechanics is real. Recent experiments (google "double-slit quantum eraser" or "delayed choice quantum eraser") have shown that interference patterns from double slit experiments only exist if we don't know which slit the electron passes through: it isn't that our consciousness is affecting the universe but rather that there must be different "worlds" for each possible outcome of the experiment and the case where we don't know which slit the electron passes through is a superposition of the two "worlds" in which we know that the electron passed through one slit or the other. This means that every one of us is like Schrodinger's cat, a superposition of mutually exclusive states even though each of us in any of those "worlds" can only perceive ourselves being in that particular "world".

4. Time can be treated as the fourth dimension of space. This is due to Einstein: in fact it is an extension of special relativity and part of general relativity. In Einstein's theories, if you accelerate from one speed to another then you experience a "space time rotation" which means that your measurements of distances and time have been altered. When applied to the universe as a whole, it means that the universe, in a sense, is not changing with time but just is. Imagine if the passing of time were like you looking out the window of your car as you drove down the highway: imagine you could only see the present and not the future or the past; you would get the impression that the universe were changing with time and the future was yet to be determined but, in reality, the past is still there behind us and the future is laid out in front of us.

5. Thermodynamics implies that entropy can never be zero so, again, there is no beginning of time. This is another argument from Hawking, from his book A Brief History of Time, for why there is no beginning of time. If there were a singularity at the beginning of time then entropy would be zero but the Third Law of thermodynamics says zero entropy is impossible so this implies that there would be no be beginning of time. The Second Law of thermodynamics also says that the entropy of the universe is always increasing which implies that the universe will expand forever and eventually decay into the smallest of elementary particles. Hawking's great insight was to point out that the Second Law of thermodynamics actually *defines* the arrow of time. Scientists had been thinking this way for some time but Hawking applied it to the universe as a whole to argue that the expansion and heat death of the universe is inevitable.

6. A positron (an anti-electron) is an electron travelling backwards in time. This is an idea from Dirac: in fact, he postulated the positron (a kind of anti-matter) from the idea that elementary particles should be able to travel in either direction in time and he speculated that anti-matter would exist and would appear to annihilate with matter when they came in contact. Sure enough, positrons (and anti-matter in general) is real and they do annihilate when they come in contact with electrons. Of course, how can this be? How can matter be destroyed like this? From Dirac's point of view, the electron does not disappear: it becomes the positron and travels back in time. Energy is conserved because an x-ray photon is released in the process.

7. Photons can be bent by a gravitational field. In fact, a sufficiently strong gravitational field can catch a photon in orbit. A photon that passes beneath this "event horizon" cannot escape. This is what is then called a "black hole".

8. Photons carry momentum. We learn in school that momentum is mass times velocity so how can a photon carry momentum? It turns out that this is only an approximation and that even massless particles have momentum.

9. X-ray photons can decay into electron-positron pairs. There is a catch though: when an x-ray photon decays it decays into two paricles (an electron and a positron) of equal mass moving in opposite directions. So what happens to the original momentum of the photon? Well, it turns out that this momentum needs to be transferred to something massive, such as an atomic nucleus through the emission and subsequent absorption of a virtual photon. This, of course, needs to happen after the decay occurs. This is a good example of how the quantum world does not care about our naive notions of cause and effect: in the quantum world, events can ultimately be their own causes.

10. Most of the mass of the universe is made up of matter we cannot see. We know this because we can see how galaxies are gravitationally attracted to each other to a degree that suggests there is more matter than we can see, even if we assume that the galaxies have enormous black holes at their cores. Most likely this dark matter consists of non-hadronic (ie neither leptons nor baryons) matter that does not interact electromagnetically or nuclearly, only gravitationally. This matter is believed to be more massive than even the Higgs Boson, which is why we haven't made one yet in a particle accelerator. There is actually a long standing theory called "supersymmetry" that actually predicts non-hadronic dark matter. If a particle accelerator were to produce a particle of dark matter then it would appear as though all the mass and energy that was put into an experiment had simply disappeared. This would be a big deal.