Science
- Physics Problem Lab
5 questions
- MCAT Study Group
4 questions
- Mathematics Explorers
4 questions
- Psychology & Neuroscience
4 questions
- Environmental Science Hub
4 questions
- Fitness & Movement
3 questions
-
0Do we forget because memories decay, or because new ones interfere?My notes list decay theory and interference theory as two explanations of forgetting, then move on without saying which one the evidence supports. Are they competing explanations, and is there a way to tell them apart experimentally?3 OpenPsychology & Neuroscience · 8h ago
-
0Is working memory really seven items, and is that still accepted?The magical number seven plus or minus two appears in every introductory text. It also appears in a lot of design advice about menu lengths, which makes me suspect it has been stretched well past what the original paper said. Is the number still accepted, and what was actually measured?3 OpenPsychology & Neuroscience · 8h ago
-
0What does "statistically significant" actually mean in a psychology paper?I can apply the rule that p below 0.05 means significant, but I cannot say what has been established when a paper reports it. Some of my classmates read it as a 95 percent chance the hypothesis is true, and I am fairly sure that is wrong. What does the number actually claim?4 OpenPsychology & Neuroscience · 8h ago
-
0Why does the brain not feel pain when it processes all of our pain?Awake brain surgery keeps coming up in lectures as evidence that the brain has no pain receptors, which sounds like a contradiction given that the brain is where pain is experienced. If the brain generates the sensation, why does cutting it produce nothing?3 OpenPsychology & Neuroscience · 8h ago
-
0How is PV = nRT derived from molecules bouncing off the walls?I can use PV = nRT without trouble but it feels handed down. Our notes say it comes out of kinetic theory by considering molecules hitting a wall, then skip to the result. What are the actual steps? And where does temperature enter, given that a single molecule does not have a temperature?3 OpenPhysics Problem Lab · 8h ago
-
0If friction gives a rolling wheel its torque, why does it do no work?For a wheel rolling without slipping, static friction is what stops it sliding and my notes also say it supplies the torque that spins it up. Two lines later the same notes say that friction does no work. If it is exerting a torque and the wheel is spinning faster than before, energy has gone somewhere. Where is it coming from if not from the friction force?3 OpenPhysics Problem Lab · 8h ago
-
0How do you get v² = u² + 2as from the other two equations?We were handed the three constant acceleration equations and told to memorise them. Two of them I can see the sense of: v = u + at is just the definition of acceleration, and s = ut + ½at² comes from the average velocity. But v² = u² + 2as looks unrelated to either, and I cannot see why there is no t in it. Is it derived from the other two or is it separate?3 OpenPhysics Problem Lab · 8h ago
-
0Is centripetal force an extra arrow on a free body diagram?Every time I draw a free body diagram for something moving in a circle I get stuck on whether to add an inward arrow labelled centripetal force. Some of my notes draw it, others say it is already accounted for. When I draw both the tension and a centripetal force I get an answer that is too big by a factor of two, so clearly one of them should not be there. What is the actual rule?4 OpenPhysics Problem Lab · 8h ago
-
0Where does the ½ in ½mv² actually come from?Every textbook writes KE = ½mv² and moves on. Dimensional analysis tells me the m and the v² have to be there, but the ½ looks like it was put in to make something cancel later. Is there a derivation where the ½ falls out on its own instead of being chosen? I have done one calculus course, so an integral is fine. I just want to see the step it comes from.4 OpenPhysics Problem Lab · 8h ago
-
0Why do we need the Nernst equation if the resting potential is just given as -70 mV?Every source gives the resting membrane potential as about -70 mV, and then also asks me to calculate equilibrium potentials with Nernst, which give different numbers for each ion. If the answer is -70, what are all the other numbers for?3 OpenMCAT Study Group · 8h ago
-
0Why does the loop of Henle need to be a countercurrent arrangement?I can recite that the descending limb is permeable to water and the ascending limb pumps sodium, and that this multiplies the gradient. What I cannot see is why the hairpin shape is necessary rather than convenient. Could the same gradient not be built with a straight tubule?3 OpenMCAT Study Group · 8h ago
-
0What do Km and Vmax actually mean, beyond the equation?I can rearrange Michaelis Menten and read a Lineweaver Burk plot, but I could not explain to someone what Km is a measure of. Calling it the substrate concentration at half Vmax is a definition rather than a meaning. What are these two quantities telling me about an enzyme?3 OpenMCAT Study Group · 8h ago
-
0Why does haemoglobin bind oxygen more easily after the first molecule?The oxygen dissociation curve is sigmoid rather than hyperbolic, and my notes say this is because binding is cooperative. That is the name of the observation rather than an explanation of it. What physically changes in the molecule after the first oxygen binds, and why does that make the next one easier?3 OpenMCAT Study Group · 8h ago
-
0Why can you not divide by zero instead of just calling it infinity?Dividing by smaller and smaller numbers gives bigger and bigger answers, so calling 1/0 infinity looks like the natural extension rather than an error. Calculators refuse it, and my notes say it is undefined rather than infinite. What actually goes wrong if you define it?3 OpenMathematics Explorers · 8h ago
-
0Where does e come from, and why is it 2.718 and not some other number?π at least has an obvious job, it is the ratio of a circle. e just turns up in compound interest, in calculus, and in probability, and I have never understood what it is the ratio of. What is the actual definition, and why does that particular value fall out of it?3 OpenMathematics Explorers · 8h ago
-
0Why is a negative times a negative a positive?I was taught this as a rule to memorise and it has bothered me since. Every explanation I find is either "two wrongs make a right", which is not mathematics, or a debt analogy that stops working the moment I push on it. Is there a reason it has to be positive, or was it simply chosen because it is convenient?3 OpenMathematics Explorers · 8h ago
-
0Why does 0.999... equal 1 rather than just being very close?I keep being told that 0.999... is exactly 1, not approaching it. Every proof I have seen feels like a trick. The 10x one in particular looks like it assumes the answer, because you have to already believe the number behaves like an ordinary number before you can multiply it by ten. Is there a version that does not feel like sleight of hand?4 OpenMathematics Explorers · 8h ago
-
0How much protein does the evidence actually support for building muscle?Recommendations range from the official daily allowance of 0.8 grams per kilogram to gym advice of well over two, a difference of nearly three times. Both sides cite research. What does the actual evidence support, and where does the disagreement come from?3 OpenFitness & Movement · 8h ago
-
0Why does progressive overload matter more than varying the exercises?One half of the advice I read says to keep changing exercises so the muscles cannot adapt, and the other says to stick with the same lifts and add weight over time. These cannot both be right. Which one does the evidence support, and what is muscle confusion actually claiming?3 OpenFitness & Movement · 8h ago
-
0Is lactic acid actually what makes muscles burn during hard effort?Lactic acid gets blamed for the burning during a hard set and for the soreness two days later. I have since read that both attributions are wrong, and that lactate is a fuel rather than a waste product. What is actually causing the burn?3 OpenFitness & Movement · 8h ago
-
0Where does the 1.5 degree target come from, and why that number?1.5 degrees is treated as a line that must not be crossed, but a tenth of a degree either side cannot be a physical boundary. Nothing in the climate changes discontinuously at exactly that point. How was it arrived at, and what happens if it is passed?3 OpenEnvironmental Science Hub · 8h ago
-
0What is the actual statistical difference between weather and climate?"Climate is average weather" is the line everyone uses, but averages over what, and why thirty years specifically? It sounds like a convention rather than a threshold with meaning. Is there a real statistical reason for the separation?3 OpenEnvironmental Science Hub · 8h ago
-
0Why is planting trees not enough to offset emissions?Trees absorb carbon dioxide, so planting enough of them ought to cancel out what we emit. Every analysis I read says it cannot work at the scale required, then moves on without showing the arithmetic that rules it out. Where exactly does the idea break down, and is it the area, the time, or something else?3 OpenEnvironmental Science Hub · 8h ago
-
0How can CO₂ warm the planet when it is only 0.04% of the atmosphere?This is the objection I keep meeting and I cannot answer it properly. Carbon dioxide is a few hundred parts per million, while nitrogen and oxygen make up almost all of the air. Why does the trace gas control the temperature rather than the bulk of the atmosphere?3 OpenEnvironmental Science Hub · 8h ago
-
Alex Chen 65d ago
Microscopy footage of biological specimens. Cell bio hits different when you actually see the cells.
0 0 0 -
Emma Larsson 65d ago
Wildlife in its habitat. Biodiversity is not an abstract concept when you see it alive.
0 0 0 -
Yuki Tanaka 65d agoCell Membrane Transport
Cell Membrane Transport
Mini-courseCell Membrane Transport1 unit · 1 lesson · 3 questionsWhich type of transport requires ATP?0 0 0 -
Liam O'Donnell 65d ago
Strength training fundamentals. Compound movements that build real-world functional strength.
0 0 0 -
Emma Larsson 65d ago
Quick science visual for study breaks.
0 0 0 -
Yuki Tanaka 65d agoWhy you overestimate shark attacks
The availability heuristic: we overestimate the probability of events we can easily recall (plane crashes, shark attacks) and underestimate common risks (car accidents, heart disease). Media exposure literally distorts risk perception. Knowing this does not fully fix it.
0 0 0 -
Liam O'Donnell 66d ago
Lab chemistry happening. Titration, color changes, the whole beautiful mess.
0 0 0 -
Diego Fernández 66d ago
Breathtaking nature footage. These ecosystems are what we study and what we are trying to protect.
0 0 0 -
Liam O'Donnell 65d agoProgressive overload is everything
The only universal principle in strength training: progressively increase the demand. More weight, more reps, more sets, shorter rest, better ROM, or slower tempo all count. The body adapts to exactly what you ask of it. Nothing more.
0 0 0 -
Sofia Reyes 67d ago
The human mind at work. Every decision, perception, and memory is a process happening right now.
0 0 0 -
Liam O'Donnell 67d ago
Forest canopy. Carbon sinks, water filters, biodiversity hotspots. All at once.
0 0 0 -
Sofia Reyes 65d agoStop stretching before workouts
Static stretching before exercise does NOT prevent injuries. Meta-analyses consistently show this. Dynamic warmups (leg swings, arm circles, bodyweight squats) prepare muscles better. Save static stretching for after.
0 0 0 -
Alex Chen 67d ago
Human behavior captured vertically. Watch the micro-expressions.
0 0 0 -
Diego Fernández 68d ago
Quick movement drill. Save for your next gym session.
0 0 0 -
Liam O'Donnell 66d agoThe most beautiful equation
$e^{i\pi} + 1 = 0$. Five fundamental constants connected by three basic operations. Feynman called it "the most remarkable formula in mathematics." What makes it deep is not the beauty. It falls out naturally from the Taylor series of $e^x$ when you plug in $ix$. Beauty as a consequence, not a goal.
0 0 0 -
Emma Larsson 68d ago
Chemical reactions in real time. If your lab partner has ever said "is it supposed to do that?" you know the vibe.
0 0 0 -
Sofia Reyes 69d ago
Data visualization and mathematical modeling. Turning abstract equations into visible understanding.
0 0 0 -
Emma Larsson 66d agoClimate Science Essentials
Climate Science Essentials
Mini-courseClimate Science Essentials1 unit · 1 lesson · 3 questionsWhich gas contributes most to the enhanced greenhouse effect?0 0 0 -
Alex Chen 69d ago
Quick physics visual for your feed. Save this one.
0 0 0 -
Alex Chen 70d ago
Mathematical patterns in nature. Fibonacci spirals, fractal coastlines, geometry hiding in plain sight.
0 0 0 -
Sofia Reyes 67d agoCARS hack that actually works
Read the entire passage FIRST without looking at questions. Write a one sentence summary. Then tackle each question. It feels slower but you stop re-reading everything four times. Saved me about 40% of my CARS time.
0 0 0 -
Sofia Reyes 70d ago
Abstract geometric patterns. Pure mathematics made visual. Symmetry groups in motion.
0 0 0 -
Emma Larsson 71d ago
The way light refracts through different liquids at various temperatures. Physics is beautiful when you actually see it.
0 0 0 -
Omar Haddad 66d agoNumber Theory Basics
Number Theory Basics
Mini-courseNumber Theory Basics1 unit · 1 lesson · 3 questionsHow many prime numbers are there?0 0 0 -
Liam O'Donnell 71d ago
Mindfulness and focus. The neuroscience of attention is one of the hottest research areas right now.
0 0 0 -
Emma Larsson 71d ago
Ocean waves and marine life. 70% of the planet. Less than 5% explored.
0 0 0 -
Liam O'Donnell 67d agoThe most underrated formula
Hot take: $\tau = r \times F$ (torque) deserves more love. It bridges rotational and linear mechanics, and once you see a seesaw problem through that lens, angular momentum clicks immediately. Try it on your next problem set.
0 0 0 -
Liam O'Donnell 71d ago
Workout footage. Proper form is everything. Watch the controlled movement through full range of motion.
0 0 0 -
Diego Fernández 84d ago💡 Tip Draw the free-body diagram. Every. Single. Time.
90% of the mechanics mistakes I see in this group vanish if you draw the FBD first. No shortcuts, no 'I can see it in my head'. Forces you don't draw are forces you'll forget.
7 2 5 -
Sofia Reyes 67d agoCarbon cycle in 60 seconds
Fast loop: atmosphere ↔ biosphere (years to decades). Slow loop: atmosphere ↔ lithosphere (millions of years). Fossil fuels short-circuit the slow loop. We are releasing carbon that took millions of years to store in just decades. That is the whole problem.
0 0 0 -
Omar Haddad 71d ago
Yoga and mobility. Flexibility is not about touching your toes, it is about moving well through life.
0 0 0 -
Sofia Reyes 114d ago💡 Tip CARS: stop highlighting, start summarizing
Biggest jump of my prep (124→128): after every paragraph write a 5-word main-point note in the margin. It forces active reading and gives you a map to answer from. Highlighting is passive; it feels productive and isn't.
7 2 5 -
Sofia Reyes 67d agoConservation of Energy
Conservation of Energy
Mini-courseConservation of Energy1 unit · 1 lesson · 3 questionsA ball is dropped from 10 m. At what height is its kinetic energy equal to its potential energy?0 0 0 -
Alex Chen 67d agoWhy biodiversity actually matters
Not about saving cute animals. Ecosystem services (pollination, water purification, soil fertility, disease regulation) depend on species interactions. Lose the keystone species and the network collapses. See: wolves in Yellowstone.
0 0 0 -
Sofia Reyes 68d agoMemory Systems
Memory Systems
Mini-courseMemory Systems1 unit · 1 lesson · 3 questionsWhich memory system stores information for 15-30 seconds without rehearsal?0 0 0 -
Liam O'Donnell 70d agoAmino acid cheat sheet
Stop memorizing alphabetically. Group by property: nonpolar aliphatics (GAVLIP), aromatics (FWY), polar uncharged (STCMNQ), positive (KRH), negative (DE). The grouping reveals the functional patterns your professor actually tests.
0 0 0 -
Yuki Tanaka 69d agoThe replication crisis is a good thing
About 60% of psychology studies fail to replicate. This is not a reason to dismiss psychology. It is the field maturing. Pre-registration, larger samples, open data. Ask not "is this true?" but "how strong is the evidence?"
0 0 0 -
Alex Chen 71d agoWhy does math describe reality?
Wigner asked in 1960: why does math, a product of human thought, describe the physical universe so well? Group theory was pure abstraction, then classified elementary particles. Non-Euclidean geometry seemed useless, then became the language of general relativity. Nobody has a good answer.
0 0 0 -
Liam O'Donnell 70d agoNeuroplasticity is oversold
"You can rewire your brain!" Technically true. Wildly oversimplified. Plasticity is strongest in childhood, declines with age, and is constrained by genetics. You cannot become a new person by thinking differently. But targeted practice CAN strengthen specific neural pathways.
0 0 0 -
Omar Haddad 71d agoEinstein's best thought experiment
Imagine riding a photon. What does the universe look like? This is literally how Einstein started building special relativity. Not with equations. With imagination. The math came after the "what if."
0 0 0 -
Diego Fernández 71d agoProofs are explanations, not verifications
The proof of the irrationality of sqrt(2) does not just tell you it is irrational. It shows you WHY no fraction can ever equal it. That "why" is what distinguishes mathematics from computation. A calculator can verify. A proof can explain.
0 0 0 -
Marta Puig 85d ago❓ Question Intuition for why energy methods beat kinematics?
I can use both but I don't FEEL why work-energy is often cleaner. Is it just that it sidesteps time and direction? Looking for the mental model, not the formula.
5 6 0 -
Emma Larsson 105d ago💬 Discussion Anki vs handwritten notes for content review?
Team Anki here — spaced repetition on discretes is unbeatable for the sheer volume. But I still handwrite pathways (glycolysis, the nephron) because drawing forces understanding. What's your split?
6 7 0
