Science
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Nov4_Tide_slides_solar_system2.pptThe gravity of the moon can pull up the ocean
Tides
- The cyclic rise and fall of ocean levels based on gravitational forces.
- Can be high and low
- Height of high and low tides varies based on lunar phases (moon’s revolution) and rotation of the Earth
- Tides are not the same as currents!!
- But can produce weathering and erosion
- And maybe……. Life on a moon of Jupiter (!?)
Gravity is stronger if you’re closer to the object
Moon’s gravity is strongest here. Ocean levels pulled up towards the moon
Moon’s gravity is weakest
here. Ocean levels can rise
away from earth (think of
the solid Earth shifting to
the right by a couple of feet)
earth gets stretched! (by a couple of feet). Water flows to
compensate for the difference in gravity
Stronger gravity on one side, weaker on the other
Numerical calculation of tidal force
Tides: Spring vs. Neap
When the Sun, Moon,
and Earth are aligned, the
gravitational pull on the Earth
is greatest and water levels
respond by rising.
The highest tides occur at the
New Moon and the next
highest at the Full Moon.
These are called spring tides.
When the Moon is at right
angles to the Sun and Earth,
(whats the name of the phases?)
the pull is less and the tides
are lower. These are termed
neap tides.
Strongest spring tide at new moon
2nd strongest at full moon
Tides and phases of the moon
C
Earth
A
B
D
E
F
Questions:
1. What letter(s) have the strongest tides. What phases are they?
2. What letter(s) have the weakest tides. What phases are they?
3. How long does it take for the moon to go from C F ??
4. If the little smiley face is at F at 6 AM. What time of day will he be
when he faces A?
Tides and phases of the moon
C
Answers:
- A&D (new, full),
- 2. C&F (1st & last quarter),
3. 2 weeks,
4. noon (i.e. 6 hour = ¼ day)
Earth
A
B
D
E
F
Questions:
1. What letter(s) have the strongest tides. What phases are they?
2. What letter(s) have the weakest tides. What phases are they?
3. How long does it take for the moon to go from C F ??
4. If the little smiley face is at F at 6 AM. What time of day will he be at
A?
Midnite noon midnite noon midnite noon midnite
Tides cycle about twice/day
Time of high tide on a given day depends upon where the
moon is in its orbit
If the moon is full, about what time should we
get a high tide?
About midnight, but this can vary a lot due to local variations
in coastline geometry
May 6
May 11
May 21
May 27
Tidal strength cycles about twice per month
(note this is not the identical to the homework)
So back to the moon pulling up the sea.
OK, the moon is still pretty small
Suppose the moon were a lot bigger!?!?
Suppose we were the moon orbiting something big?
What do you think would happen?
What would this do to our oceans, our crust, our mantle?
So does this ever happen in the solar system? Yes!!
What’s the biggest planet in the solar system?
Jupiter causes huge tides on its satellites. What do you think happens?
A real photo from the Voyager 1 spacecraft of a plume
Jupiters gravity stretches the innards of Io, melting rock into
magma which erupts and makes Io the most volcanically active
object in the solar system
The other moons are further away and have more ice-
so no volcanoes.
But wait a second………. What might happen to ice??????
Europa: The 2nd ocean in the solar system!
Icy crust
Ocean under the ice- the melting is
From the flexing of the ice and rocky core
due to the enormous tides from Jupiter
We are pretty sure there is an ocean under the ice. (this is why
when we say earth is unique- it’s the liquid water on the surface.)
But how thick is the ice? Is there life in the ocean? No one knows.
NASA will send a mission to Jupiter and Europa in 5-10 years
Rocky core with magma keeping the water warm
Tides in the rest of the solar system?
https://www.youtube.com/channel/UCBTwJSnAqZZczK7stBaYq5w/videos
Go to Video #9 of Charles Cockell’s Life in the Universe Pandemic Series
“Why is everyone so excited about Europa”?
Small object approaches big object: What happens?
Side near big object feels more gravity
Side near big object starts getting stretched
Stretching is so big, object gets destroyed!
Debris encircles the planet.What is
This?
The white circle (distance where destruction occurs)
is called the Roche limit
All planets have a Roche limit, but for small ones (like Earth)
You have to get so close, it doesn’t mean much
But all the Jovian planets have ring systems.
The same process which causes high tides at Rehoboth causes
Volancoes on Io, a likely ocean on Europa and
Saturns rings- its just a matter of degree.
Stretching is so big, object gets destroyed!
The same process which causes high tides at Rehoboth, Ocean
City etc. and in the Chesapeake Bay causes volancoes on Io,
a likely ocean on Europa and
Saturns rings- its just a matter of degree.
