Tide question from my 6 year old - please help
Discussion
I have a very bright 6 year old who loves thinking about all sorts - I m not very bright so need help
The question was what would happen to a tennis ball if it was dropped off the back of the Dover Calais ferry half way
Would it quickly drift to nearest land
Would it depend on the wind
Would it just have a laugh and bob about
Would it deteriorate before it appeared at land
Would Matt Lucas put it up his bum
None of the above / other
Many thanks
The question was what would happen to a tennis ball if it was dropped off the back of the Dover Calais ferry half way
Would it quickly drift to nearest land
Would it depend on the wind
Would it just have a laugh and bob about
Would it deteriorate before it appeared at land
Would Matt Lucas put it up his bum
None of the above / other
Many thanks
Edited by Spare tyre on Sunday 19th April 21:03
Spare tyre said:
I have a very bright 6 year old who loves thinking about all sorts - I m not very bright so need help
The question was what would happen to a tennis ball if it was dropped off the back of the Dover Calais ferry half way
Would it quickly drift to nearest land
Would it depend on the wind
Would it just have a laugh and bob about
Would it deteriorate before it appeared at land
Would Matt Lucas put it up his bum
None of the above / other
Many thanks
likely be taken by the tide, so could go out to sea-ocean. But.. the churn from the propellors might give it a push back towards Dover. The question was what would happen to a tennis ball if it was dropped off the back of the Dover Calais ferry half way
Would it quickly drift to nearest land
Would it depend on the wind
Would it just have a laugh and bob about
Would it deteriorate before it appeared at land
Would Matt Lucas put it up his bum
None of the above / other
Many thanks
Edited by Spare tyre on Sunday 19th April 21:03
Great question!
Tennis balls are pretty tough so I’d guess it would probably reach the shore…, somewhere. It is not unusual to find tennis balls on the beach where I live, yet the nearest tennis court is miles away!
I think where it washed up would depend on the tide strength / direction (which you can find in a tidal atlas like tides planner) and the wind strength / direction.
Tides in the Dover straits can flow at 3 knots or more so it could go a long way in a few hours, but when the tide turns it might come straight back!
Sailors use the tidal ‘set’ and wind leeway to give an estimated position on a chart, like this:

So I guess if you could calculate how fast the tennis ball travels through the water at a given wind speed, you could use something similar to work out where the ball ends up.
Unless a playful dolphin nicks it, then it’s anyone’s guess!
I will ask my son, he is RNLI boat crew so should know this important stuff!
Tennis balls are pretty tough so I’d guess it would probably reach the shore…, somewhere. It is not unusual to find tennis balls on the beach where I live, yet the nearest tennis court is miles away!
I think where it washed up would depend on the tide strength / direction (which you can find in a tidal atlas like tides planner) and the wind strength / direction.
Tides in the Dover straits can flow at 3 knots or more so it could go a long way in a few hours, but when the tide turns it might come straight back!
Sailors use the tidal ‘set’ and wind leeway to give an estimated position on a chart, like this:
So I guess if you could calculate how fast the tennis ball travels through the water at a given wind speed, you could use something similar to work out where the ball ends up.
Unless a playful dolphin nicks it, then it’s anyone’s guess!
I will ask my son, he is RNLI boat crew so should know this important stuff!
Depends, apart from the tidal flow there are various semi localised current sets in operation in the Channel, add to that the effects of winds etc and it's anyone's guess. Best estimated is for it to land either southwest, possibly Cornwall, perhaps Northern lizard or northwest France not too far from where it was dropped. The sea's a funny old bugger.
Tennis balls are quite low density, so will float quite high and be influenced as much by wind as tide, with a wobbly vector down tide and wind governed by both. It will likely end up on a beach long before it disintegrates, where it would hopefully end up being enjoyed by a dog. Beaches are a regular source of free tennis balls for my parents' dog.
Great Question!
The ball will last months, if not years, before deteriorating and sinking.
The time and tide really matter.
https://montymariner.co.uk/tide-stream-charts/np25...
-Boring answer. It jumps off the ferry a few hours before High Tide at Dover. It will probably drift West and then towards the french coast and wash up on Boulogne beach.
-Better answer. If it jumps in near High Tide time then there is a stronger flow through the Channel heading East. It might have enough time to escape the bottleneck of the Channel and get into the Southern North Sea currents. This is much more exciting...
Messages in a bottle launched from the Kent coast have washed up in The Netherlands, Denmark and even Norway.
https://www.bbc.co.uk/news/articles/cn80rkjr39yo
-Best answer? An Easterly wind and just the right tide might take it West, out of the Channel and then the World is it's Oyster! A bottle launched from Bournemouth made it all the way to Australia
The ball will last months, if not years, before deteriorating and sinking.
The time and tide really matter.
https://montymariner.co.uk/tide-stream-charts/np25...
-Boring answer. It jumps off the ferry a few hours before High Tide at Dover. It will probably drift West and then towards the french coast and wash up on Boulogne beach.
-Better answer. If it jumps in near High Tide time then there is a stronger flow through the Channel heading East. It might have enough time to escape the bottleneck of the Channel and get into the Southern North Sea currents. This is much more exciting...
Messages in a bottle launched from the Kent coast have washed up in The Netherlands, Denmark and even Norway.
https://www.bbc.co.uk/news/articles/cn80rkjr39yo
-Best answer? An Easterly wind and just the right tide might take it West, out of the Channel and then the World is it's Oyster! A bottle launched from Bournemouth made it all the way to Australia
In a similar vein. The Friendly Floatees Spill is a popular story with inquisitive young ones.
https://en.wikipedia.org/wiki/Friendly_Floatees_sp...
In 1992 a container load of Plastic Toys went overboard in mid Pacific...
https://en.wikipedia.org/wiki/Friendly_Floatees_sp...
In 1992 a container load of Plastic Toys went overboard in mid Pacific...
Spare tyre said:
Marvellous chaps Thankyou.
Contemplating putting an AirTag in a ball on way to summer holiday and waiting, but naughty on the littering front though
Use a ball made of natural cork instead of a tennis ball - biodegradable.Contemplating putting an AirTag in a ball on way to summer holiday and waiting, but naughty on the littering front though
Obvs not 1:1 for a tennis ball for the purposes of the experiment.
Edited by TheJimi on Monday 20th April 13:30
M11rph said:
In a similar vein. The Friendly Floatees Spill is a popular story with inquisitive young ones.
https://en.wikipedia.org/wiki/Friendly_Floatees_sp...
In 1992 a container load of Plastic Toys went overboard in mid Pacific...
There is also the container load of Lego that went over the side near Cornwall in 1997 https://en.wikipedia.org/wiki/1997_Lego_spillhttps://en.wikipedia.org/wiki/Friendly_Floatees_sp...
In 1992 a container load of Plastic Toys went overboard in mid Pacific...
Spare tyre said:
Marvellous chaps Thankyou.
Contemplating putting an AirTag in a ball on way to summer holiday and waiting, but naughty on the littering front though
Good idea in principle, but don't bother wasting an AirTag (or similar device) on this. They rely on fairly close range 'connectivity' with an iPhone or iPad in order to send/receive it's location and hence be visible online. I strongly suspect it would never see connectivity in the English Channel (unless someone in a small boat passes directly adjacent - unlikely). In fact, my guess would be that the internal battery will die before it ever gets anywhere near a beach where it can 'ping' from a phone again.Contemplating putting an AirTag in a ball on way to summer holiday and waiting, but naughty on the littering front though
Another option, if you really were keen to do such a thing, would be one of those 'dog collar' tracker modules, which has its own internal GPS and GSM system....but likely a waste of money on that too sadly.
MattyD803 said:
Spare tyre said:
Marvellous chaps Thankyou.
Contemplating putting an AirTag in a ball on way to summer holiday and waiting, but naughty on the littering front though
Good idea in principle, but don't bother wasting an AirTag (or similar device) on this. They rely on fairly close range 'connectivity' with an iPhone or iPad in order to send/receive it's location and hence be visible online. I strongly suspect it would never see connectivity in the English Channel (unless someone in a small boat passes directly adjacent - unlikely). In fact, my guess would be that the internal battery will die before it ever gets anywhere near a beach where it can 'ping' from a phone again.Contemplating putting an AirTag in a ball on way to summer holiday and waiting, but naughty on the littering front though
Another option, if you really were keen to do such a thing, would be one of those 'dog collar' tracker modules, which has its own internal GPS and GSM system....but likely a waste of money on that too sadly.
As you say the likely good of getting a ping from a passing phone is very small
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