Why can’t anything go faster than the speed of light? | The History of the Speed of Light Part II

Figuring out that the speed of light was the ultimate speed limit of the universe is part of the late 19th-century and early 20th-century history of Physics. This is part 2 of my “history of the speed of light” series.

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👩🏽‍💻 Dr Becky Smethurst is an astrophysicist researching galaxies and supermassive black holes at Christ Church at the University of Oxford.

[DrBecky]

Forgot to say photons (particles of light) are a special case - they have no mass. Hence why they can travel at the maximum speed with no trouble!

[somedaypilot]

Please do more "history of ..." videos. It's fascinating to hear about how we figured these things out, and you're a wonderful teacher.

[keithmayes]

I love your style of presentation, your enthusiasm for your subject shines through and your explanations and analogies are so good my eyes hardly ever glaze over. Please keep ‘em coming!

[handsfree]

I’ve been increasing in mass lately, guess I must be travelling too fast!

[stevenbaumann]

I’m so glad you showed how scientific failures can sometimes lead to the best discoveries. Us scientists should should really embrace our failures. Their experiment was only a partial failure., like you said, it paved the way for Einstein.

[joelvirolainen]

The momentum has the relativistic correction term, so it's the momentum term increasing to infinity preventing the speed reaching light speed.
The equation has two parts, the energy of the mass (staying the same), and energy of the movement (the momentum part).

[dungeonseeker]

YouTube recommended this (actually part one) and I'm an instant sub. Fascinating topics presented clearly & factually. I'll be binge watching most of your back catalogue this weekend.

[UkDave]

If only I'd had a physics teacher like you back in the 1980s, someone who explained the subject in an engaging way rather than just attempting to force the equations into our heads by making us repeat them over and over

[Michel-rhnj]

Your Enthusiasm and clarity in explaining physics is amazing. For me, your videos are continuation of Richard Feynman lectures on physics, I’m hooked. Please keep those videos and books coming (audiobook is super)

[JoeJumps]

The brilliance of your mind coupled with your lovely accent and a dash of your beauty. Makes you an absolute doll. I love how passionate you are about your work. You definitely got another subscriber out of me. Looking forward to more videos.

[Valdagast]

The only thing known to go faster than the speed of light is a cat who hears the treats bag.

[ecospider]

I had two Epiphany’s in just an eight minute video. You are truly amazing. I have enjoyed understanding this at a high school level for 30 years. Randomly reading thing to see if I get something new but don’t find anything. 8 minutes of your video, my mind is blown and now I want to go do some math.

[DavidFMayerPhD]

"Empty Space" is filled with fields whose values are (close to) zero. Nonetheless, the fields are quite real and measurable to great precision.
In his original paper, Einstein did NOT invoke the Michelson & Morley experiment. His rationale was this: In Classical Mechanics, coordinates transform according to "Galilean Transformation". In Maxwell's Electromagnetism, coordinates transform according to "Lorentz Transformation". It is absurd to imagine that natural coordinates transform differently for different phenomena. Hence, one of the two transformations must be incorrect. Since Maxwell predicts the speed of light correctly, he decided that the "Lorentz Transformation" must be correct. The "Lorentz Transformation" preserves the speed of light in all inertial frames.


Also, in using the equation E^2=M^2*C^4 + P^2*C^2 (where ^ denotes exponentiation), Dr Becky mixed up REST MASS with TOTAL MASS. The equation is better written E^2 - P^2*C^2 =M^2*C^4 which is a Lorentz invariant, where M is the REST MASS which does not change with motion. In Einstein's equation E = M*C^2, M refers to the TOTAL mass even when the particle is moving relative to the observer. This also answers the frequently asked question, when one changes coordinate systems, energy changes. Where does the change in energy come from or go? This question is based on the false assumption that energy is a scalar. The answer is that E is NOT a scalar, but the time coordinate of a Lorentz 4-vector which transforms according to the "Lorentz Transformations". Sorry to be so pedantic.

[daisyxfaith]

Dr. Becky, I'm absolutely obsessed with your channel! The way you present a topic is so engaging and is somehow simultaneously approachable without oversimplifying or dumbing anything down. You rock! :)

[erictaylor]

I had a teacher explain it to me like this:
According to Einstein, if we have two objects moving relative to each other, we can say that object 1 (O1) is moving and Object 2 (O2) is stationary or we can say O2 is moving and O1 is stationary. Both are correct, even though they seem mutually exclusive.
So we could say that that matter is stationary and light is moving, or we could say light is stationary and matter is moving.
So, imagine that light is stationary in space-time while matter moves through the combined space-time at the speed of light. If a bit of matter wants to move through space, it can only do so by using some of her velocity through time. This is why time slows down when you move through space. And it is why you can't go faster than light. Your total velocity through space-time must always equal 1C.
There is a weird consequence to this. From the perspective of a photon, it never exists. A photon is created and absorbed at exactly the same time, even if that photon existed for billions of years from our perspective.

[theCodyReeder]

Oh another one of thees videos?! Happy day!

[Robert-kxmp]

Having been a physics major, I’ve heard the story many times, and whenever hearing it again I’m always amazed at Einstein.

[connorwicks]

The increase of energy with velocity comes from the geometric properties of space-time itself and not mass. Mass is an invariant quantity, being the magnitude of the 4-vector, and shouldn't be applied to the time component of a 4-vector.

[goukisan]

hi becky, great video.
i am a big science enthusiast who randomly just discovered your channel.
the bit at end when you go off-the-rail and start talking about your jewelry is so ridiculous, and yet the most enjoyable part of this video ( i subbed as soon as i saw it)
Scientists have the bad habit of making it seem that we only have passion for advanced math, physics and cosmology.
we need more people who can bridge the gap between science and our jewelries .

[Doones]

Dr. Becky, you are very clear when explaining physics and much appreciated.