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Consider a large balloon of 100 metres in diameter. Imagine this large balloon in a football stadium. The balloon is so large that it lies on top of many members of the crowd. Because they are excited, these fans hit the balloon at different times and in different directions with the motions being completely random. In the end, the balloon is pushed in random directions, so it should not move on average. Consider now the force exerted at a certain time. We might have 20 supporters pushing right, and 21 other supporters pushing left, where each supporter is exerting equivalent amounts of force. In this case, the forces exerted towards the left and the right are imbalanced in favor of the left; the balloon will move slightly to the left. This type of imbalance exists at all times, and it causes random motion of the balloon. If we look at this situation from far above, so that we cannot see the supporters, we see the large balloon as a small object animated by erratic movement. Consider the particles emitted by Brown’s pollen grain moving randomly in water: we know that a water molecule is about 0.1 by 0.2 nm in size, whereas the particles which Brown observed were of the order of a few micrometres in size (these are not to be confused with the actual pollen particle which is about 100 micrometres). So a particle from the pollen may be likened to the balloon, and the water molecules to the fans, except that in this case the balloon is surrounded by fans. The Brownian motion of a particle in a liquid is thus due to the instantaneous imbalance in the combined forces exerted by collisions of the particle with the much smaller liquid molecules (which are in random thermal motion) surrounding it.
Basically, Brownian motion of a body is what happens when a very large number of similar forces act on the same body from all possible directions. If the forces were uniform and applied at the same time to the body then there wouldn’t be any movement but since there are slight differences in the direction, strength and time of application of the forces, the body begins to move like in the simulation below of a large dust particle (yellow) experiencing brownian motion due to collision with the smaller gas molecules around it.
The clever thing is that the same can be said of stock price fluctuations where millions of tiny trading exchanges between people (small brown gas particles) push the stock price (large yellow dust particle) into a form of Brownian motion called Geometric Brownian motion. Hundreds of billions of dollars are moving similar to the lowly dust in the air around you right now. Self-similarity, once again.
"Everything you’ve learned in school as “obvious” becomes less and less obvious as you begin to study the universe. For example, there are no solids in the universe. There’s not even a suggestion of a solid. There are no absolute continuums. There are no surfaces. There are no straight lines."
Windsweptis a wind-driven kinetic façade consisting of 612 freely-rotating directional arrows creating a large-scale observational instrument that reveals the complex interactions between the wind and the building. The wind arrows serve as discrete data points indicating the direction of local flow within the larger phenomenon.
Ross and Smith ended their paper by estimating their suit’s weight. It would, they calculated, have an Earth weight of 150 pounds. On the moon, however, where gravity pulls with about 15% as much force as on Earth, their suit would weigh only about 25 pounds.
Naturally, everyone reading this would assume that since 25 pounds is much, much lighter than 150 pounds, it woulbe much easier to move on the moon thanks to the lighter body.
Not so.
It is the “weight”, the force needed to keep the suit from falling to the ground, that has dropped from 150 pounds to 25; the “mass”, the amount of matter contained in the suit, still remains the same. What this means is that despite being lighter, it’s still harder to move than on earth. Why? Inertia. Inertia is due to mass and not weight.
So if you swing your arm fast, on Earth you’d be able to control the inertia of the swing and bring your arm to stop pretty quickly due to the higher gravity helping you. On the moon, you’d need 6 times the force needed to bring the fast-swinging arm under control because even though the arm has the same inertia as on Earth, the moon’s lower gravity means you’d have to generate almost all of the force required to stop the arm from spinning your entire body off balance. That’s why you see astronauts move on the moon as if in slow-mo. The lower gravity yet same inertia forces their movements to become more like floating around than walking around. They can’t control their inertia as well as on earth so once they start moving, they keep moving for a distance.
Amazing how such a simple change in a fundamental property can create such pronounced effects. Try imagining the opposite: what would it be like to move on a planet that has 6 times greater gravity than Earth.
Yesterday there was a huge consternation on Twitter when it came to light that the Physicist who presented the ground-breaking Higgs-Boson discovery used Comic Sans throughout her presentation.
While it was definitely awful looking, Comic Sans is quite the beautiful babe when used tastefully and in moderation. The talented folks at The Comic Sans Project bring you proof.
You know when there’s a story in the news that creates a great joke opportunity, but then you realize it’s a bit too great, as in, everyone else has already made the joke?
Like this Higgs boson thing. All the jokes have been done! Wouldn’t you know it—the Higgs boson was behind the sofa the…
Being three-dimensional, we are only able to see the world with our eyes in two dimensions. A four-dimensional being would be able to see the world in three dimensions. For example, it would be able to see all six sides of an opaque box simultaneously, and in fact, what is inside the box at the same time, just as we can see the interior of a square on a piece of paper. It would be able to see all points in 3-dimensional space simultaneously, including the inner structure of solid objects and things obscured from our three-dimensional viewpoint.
If you thought time travel was challenging, just think about travelling through dimensions. Blow your mind yet?
This is something that’s been bothering me for a while and it wasn’t until a few months back that I finally saw what it actually meant when they said “time stops when you travel at the speed of light”.
Lets do a simple thought experiment - imagine that you took a spaceship and travelled all the way to the Sun. There you got out of your spaceship and just as your watch strikes 10 a.m you hopped onto a beam of light that was just starting out from the Sun’s surface. You are now hurtling through space at the maximum possible speed - the speed of light, ‘c’ and you have an astronomer friend back on earth who’s watching you through his advanced telescope - he now sees something amazing - you are not moving at all. You are standing perfectly still on that beam of light speeding past Mercury at ‘c’.
Why are you still? Because you can’t move. Every atom of your body, no, every particle in every atom of your body, is frozen into place - they all remain fixed rock solid at the exact same place they were, the instant you jumped onto the beam of light back at the Sun. Because if the particles moved, their net speed is speed of light + their own motion, which is > c - this is impossible. The max speed possible is c, and since every single particle in your body is already moving at c, they can’t move.
So, as you shoot past Venus, your friend takes a closer look at you - you’re frozen still, your watch still says “10 a.m.” because the watch hands can’t move as that would violate the ‘c’ limit. At this point, your eyes won’t see anything because if the neurons in the eye fire that would violate the ‘c’ limit, your brain won’t be able to think, for the same reason, your heart isn’t beating, and blood isn’t pumping through your veins. Temporary death. You are paused. Time has stopped for you.
Your friend back on Earth glances at his watch - 10.07 a.m. 7 minutes have passed and you’ll soon be hitting Earth.
It’s 8 minutes and 17 seconds past 10 and your friend watches you slam into Earth - since this is a thought experiment you survive the crash and your friend runs over to you to ask you about the experience - you have nothing to say. Because to you it was all over in an “instant” - one moment you are at the Sun and the next thing you know your friend is running over to you asking you how you feel. Your body doesn’t feel stiff or tired - not an atom in your body has moved from the moment you started at the Sun to the moment you crashed into Earth. In short, atom for atom, you at 10:08 a.m are the EXACT same person you were at 10:00 a.m - nothing has changed - and since nothing has changed, it’s the equivalent of saying time has stopped for you.
Now that it’s over, fumbling with your watch to set it back to Earth time while silently vowing to use a digital watch in the next thought experiment, you realize the biggest takeaway from this experiment is the insight that time doesn’t actually stop - all the clocks on earth are still running as usual - but it’s the atoms in your body that stop and that’s what makes travelling at the speed of light seem like time has stopped for you. Why is this the biggest insight? Because knowing why it feels like time has stopped for you, tells us something important about time travel - Time Travel Is Not Instant!
In TV shows and movies** , they show people stepping into a Time machine and ~whoosh~ they are gone 500 years into the future - NO! WRONG! It feels like an instant ONLY to the travellers inside the Time Machine because their atoms and bodies and brains have been “paused” by the ‘c’ limit. Observers outside the Time Machine will see the Time Machine continue to “pause” the bodies day after day for the full 500 years, which is its way of actually doing the “time travel”. People will grow old and die and new people will come, grow old and die all around the Time machine and at the end of 500 years the Time Machine would “unpause” the atoms of the travellers and they will emerge, atom for atom, the exact same people with the exact same memories in the exact same state as they were 500 years ago - if they were in the middle of exhaling as they stepped into the machine 500 years ago, they would finish the exhale as they step out from the machine 500 years later, in one continuous flow - 500 years will truly be an instant for the travellers, but not for the observers.
Driving home the biggest insight of the experiment once again - Time travel doesn’t have anything to do with manipulating time or manipulating the speed of light - it’s simply “pausing” the atoms in place, the side-effect of travelling at ‘c’, that leads to Time travel. It feels like an instant only to the travellers, it’s normal life for everyone else. Understanding these two things is the key to making Time travel a reality, because travelling at the speed of light is impossible - that approach is a dead end. But now that we know time travel is nothing but pausing the atoms in place for the duration of travel, we can explore other approaches that let us do that - cryostasis being one of them.
So, no, Time doesn’t actually stop when you travel at the speed of light. What stops is change - things travelling with you stop moving, your watch stops running, your body stops aging - so it’s only the equivalent of time having stopped and ONLY YOU, the traveller, experiences this. Everyone else who is not travelling at the speed of light will still keep seeing the “paused” version of you for the entire duration of your travel.
P.S:
Conceptually, Time travel involves going back and forward, but only forward travel is even remotely plausible. Even if we someday find a way to reverse the direction of each and every particle of each and every atom of the traveller, along the paths they had taken to reach their respective present states, we can’t restore the atoms that used to be a part of the traveller but are currently lost ( like, if the traveller lost a finger in an accident some years ago, there’s no way to restore that finger and trace back the history of those lost atoms as well, by tracing the history of the atoms in the present body of the traveller.) ** Movies and TV shows, of course, use creative freedom with their time travel sequences. The point is not to criticize them but to change how they have shaped the public perception of how time travel would happen using the current theories put forth by the scientific community.
Since I’m on the topic of interesting materials, just came to know that Diamond has not been the hardest material for at least half a decade now. First came Aggregated Diamond Nanorods (ADNR), and those were surpassed by w-BN (Wurtzite Boron Nitride) which itself has been surpassed by the current champ - a pure lab generated sample of Lonsdaleite with a value of 15.8 on the Mohs scale of hardness (Diamond is at 10).
on making hand shadows by Henry Bursill.
