B Swimming at the Same Reynolds Number as Sperm: A Reflection on Purcell's Talk

AI Thread Summary
The discussion reflects on a talk by Purcell regarding swimming at low Reynolds numbers, specifically comparing it to the conditions experienced by sperm. Participants express admiration for the clarity of Purcell's presentation, despite its complexity, noting the challenge of recalling the detailed arguments afterward. The conversation highlights the significance of understanding fluid dynamics in biological contexts, particularly in how small organisms navigate their environments. The impact of Purcell's insights on the field of biophysics is acknowledged, emphasizing their lasting relevance. Overall, the discussion serves as a nostalgic reminder of the intellectual engagement sparked by Purcell's work.
Physics news on Phys.org
I remember hearing a great talk by Purcell with the same title about 40 years ago. It was of the kind that you understand everything perfectly as it was being said, yet one hour later you would be hard pressed to reconstruct the logical sequence of the arguments. Thanks for the memories.
 
Thread ''splain this hydrostatic paradox in tiny words'

Thread ''splain this hydrostatic paradox in tiny words'

This is (ostensibly) not a trick shot or video*. The scale was balanced before any blue water was added. 550mL of blue water was added to the left side. only 60mL of water needed to be added to the right side to re-balance the scale. Apparently, the scale will balance when the height of the two columns is equal. The left side of the scale only feels the weight of the column above the lower "tail" of the funnel (i.e. 60mL). So where does the weight of the remaining (550-60=) 490mL go...
View full post »

Thread 'The Effect of Linear and Rotational Motion on Measured Weight'

Consider an extremely long and perfectly calibrated scale. A car with a mass of 1000 kg is placed on it, and the scale registers this weight accurately. Now, suppose the car begins to move, reaching very high speeds. Neglecting air resistance and rolling friction, if the car attains, for example, a velocity of 500 km/h, will the scale still indicate a weight corresponding to 1000 kg, or will the measured value decrease as a result of the motion? In a second scenario, imagine a person with a...
View full post »

Thread 'Coulomb gauge implies instantaneous radial electric field?'

Scalar and vector potentials in Coulomb gauge Assume Coulomb gauge so that $$\nabla \cdot \mathbf{A}=0.\tag{1}$$ The scalar potential ##\phi## is described by Poisson's equation $$\nabla^2 \phi = -\frac{\rho}{\varepsilon_0}\tag{2}$$ which has the instantaneous general solution given by $$\phi(\mathbf{r},t)=\frac{1}{4\pi\varepsilon_0}\int \frac{\rho(\mathbf{r}',t)}{|\mathbf{r}-\mathbf{r}'|}d^3r'.\tag{3}$$ In Coulomb gauge the vector potential ##\mathbf{A}## is given by...
View full post »

Similar threads

Chaos & Scales in Turbulent Flows
Replies
2
Views
2K
Calculating Reynolds number for a wind tunnel
Replies
9
Views
6K
Project Orion Revisited: Is Nuclear Propulsion the Future of Space Travel?
Replies
13
Views
2K
About Taylor & Wheeler 3-1 practice problem
Replies
5
Views
2K
Question about the Reynolds number and fluid drag
Replies
1
Views
3K
B Is information the 5th state of matter?
Replies
18
Views
3K
A How Does U(1) Double-Cover SO(2) for a Specified Angle?
Replies
2
Views
2K
A Inference from fine-tuning to a multiverse
Replies
5
Views
3K
Image Charges Purcell Discussion
Replies
4
Views
2K
B How can hyperreal numbers make infinitesimals logically sound in calculus?
Replies
24
Views
6K

Hot Threads

Recent Insights

Back
Top