Today I will tell you how to be just as annoying as a real physicist. And the easiest way to do that is to insist correcting people when it really doesn’t matter.

1. “The Earth Orbits Around the Sun.”

Well, actually the Earth and the Sun orbit around a common center of mass. It’s just that the location of the center of mass is very close by the center of the sun because the sun is so much heavier than earth. To be precise, that’s not quite correct either because Earth isn’t the only planet in the solar system, so, well, it’s complicated.

2. “The Speed of Light is constant.”

Well, actually it’s only the speed of light in vacuum that’s constant. The speed of light is lower when the light goes through a medium, and just what the speed is depends on the type of medium. The speed of light in a medium is also no longer observer-independent – as the speed of light in vacuum is – but instead it depends on the relative velocity between the observer and the medium. The speed of light in a medium can also depend on the polarization or color of the light, the former is called birefringence and the latter dispersion.

3. “Gravity Waves are Wiggles in Space-time”

Well, actually gravity waves are periodic oscillations in gases and fluids for which gravity is a restoring force. Ocean waves and certain clouds are examples of gravity waves. The wiggles in space-time are called gravitational waves, not gravity waves.

4. “The Earth is round.”

Well, actually the earth isn’t round, it’s an oblate spheroid, which means it’s somewhat thicker at the equator than from pole to pole. That’s because it rotates and the centrifugal force is stronger for the parts that are farther away from the axis of rotation. In the course of time, this has made the equator bulge outwards. It is however a really small bulge, and to very good precision the earth is indeed round.

5. “Quantum Mechanics is a theory for Small Things”

Well, actually, quantum mechanics applies to everything regardless of size. It’s just that for large things the effects are usually so tiny you can’t see them.

6. “I’ve lost weight!”

Well, actually weight is a force that depends on the gravitational pull of the planet you are on, and it’s also a vector, meaning it has a direction. You probably meant you lost mass.

7. “Light is both a particle and a wave.”

Well, actually, it’s neither. Light, as everything else, is described by a wave-function in quantum mechanics. A wave-function is a mathematical object, that can both be sharply focused and look pretty much like a particle. Or it can be very smeared out, in which case it looks more like a wave. But really it’s just a quantum-thing from which you calculate probabilities of measurement outcomes. And that’s, to our best current knowledge, what light “is”.

8. “The Sun is eight light minutes away from Earth.”

Well, actually, this is only correct in a particular coordinate system, for example that in which Planet Earth is in rest. If you move really fast relative to Earth, and use a coordinate system in rest with that fast motion, then the distance from sun to earth will undergo Lorentz-contraction, and it will take light less time to cross the distance.

9. “Water is blue because it mirrors the sky.”

Well, actually, water is just blue. No, really. If you look at the frequencies of electromagnetic radiation that water absorbs, you find that in the visual part of the spectrum the absorption has a dip around blue. This means water swallows less blue light than light of other frequencies that we can see, so more blue light reaches your eye, and water looks blue. 

However, as you have certainly noticed, water is mostly transparent. It generally swallows very little visible light and so, that slight taint of blue is a really tiny effect. Also, what I just told you is for chemically pure water, H two O, and that’s not the water you find in oceans, which contain various minerals and salt, not to mention dirt. So the major reason the oceans look blue, if they do look blue, is indeed that they mirror the sky.

10. “Black Holes have a strong gravitational pull.”

Well, actually the gravitational pull of a black hole with mass M is exactly as large as the gravitational pull of a star with mass M. It’s just that – if you remember newton’s one over r square law – the gravitational pull depends on the distance to the object. 

The difference between a black hole and a star is that if you fall onto a star, you’re burned to ashes when you get too close. For a black hole you keep falling towards the center, cross the horizon, and the gravitational pull continues to increase. Theoretically, it eventually becomes infinitely large.

How many did you know? Let me know in the comments.

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