Weird happenings in spacetime

Matthames

Über Member
Location
East Sussex
On my commute there is something weird that happens. I cycle the exact same distance going there and coming back, yet the journey home is 1/10th of a mile longer ;)

What is going on? Although there is a possible explanation in that I have to negotiate a couple of roundabouts, however it is difficult to actually see that it would add that much of a difference.
 

GrasB

Veteran
Location
Nr Cambridge
if you actually think about it around 150 meters isn't that far & you'll be surprised how much of a difference being on the inside & outside of a long sweeping bend will make.
 

GrasB

Veteran
Location
Nr Cambridge
Dayvo said:
You're on the other side of the road, so if you ride on a curvy, crescent-shaped road, your distance will differ!
Very true, the difference between using the offside rather than the nearside lane (ie flowing in the traffic as the road is marked rather than keeping to the nearside) for about 3/4 of a mile results in around 0.1 mile difference in the journey distance. Then the difference between taking a free line over the flyover or keeping to secondary, when there are cars about, is another 0.05 miles.
 

Arch

Married to Night Train
Location
Salford, UK
Matthames said:
I cycle the exact same distance going there and coming back, yet the journey home is 1/10th of a mile longer :biggrin:
Doesn't the second half of that sentence automatically deny the first half?:thumbsup:

Like others said, it's down to being on the inside/outside of bends and so on. Not wierd at all. After all, anything more than a 100m race in athletics, they take the bend of the track into account with the starting positions.
 

Davidc

Guru
Location
Somerset UK
It's global warming - the earth's expanded while you've been at work!
 

ColinJ

Puzzle game developer
Arch said:
Like others said, it's down to being on the inside/outside of bends and so on. Not wierd at all. After all, anything more than a 100m race in athletics, they take the bend of the track into account with the starting positions.
I used to think that it wouldn't make that much difference but then I did the calculations.

A 400 metre athletics track effectively consists of a big circle with four 90 degree arcs separated by 2 long straights and 2 short straights (which could be of zero length). The straights are the same length no matter what lane you are in. Athletics track lanes are 1.22 metres in width so if r is the radius of your lane then the radius of the next one out is (r + 1.22). That means that the second lane is 2 * pi * 1.22 metres longer than the inside lane or 7.67 metres - near enough 2% longer. That's quite a difference!

A 200 metre race is run in lanes and so is a 400 but the 200 only goes round 1 bend so the lane stagger would have to be 3.83 metres for a 200 metre event and 7.67 metres for a 400 metre event.
 

dondare

Über Member
Location
London
This is a logic problem.
The explanation is that the calibration of your measuring-device changes between morning and evening. It depends on the circumference of the wheel with the sensor, which can change with tyre pressure.
So logic dictates that you must have a slow puncture.
 
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