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xkcd: Sea Level
https://xkcd.com/3135/

Yup, constantly changing with enormous energies expended.

Explained at:
https://www.explainxkcd.com/wiki/index.php/3135:_Sea_Level

Lynn

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From Newsgroup: rec.arts.sf.written

On 2025-08-30, Lynn McGuire <lynnmcguire5@gmail.com> wrote:

xkcd: Sea Level
https://xkcd.com/3135/

Yup, constantly changing with enormous energies expended.

Somewhat related: Larry Niven, "There Is a Tide".

(Jurer Ybhvf Jh ernyvmrf gung gvqrf ba n zbbayrff cynarg zrna gung
gur guvat va beovg gung rirelobql nffhzrq gb or na napvrag fgnfvf
svryq shyy bs Fynire gernfher vf ab fhpu guvat, naq lbh qba'g jnag
gb trg pybfr gb vg.)

The previous one...

Wavefunction Collapse
https://xkcd.com/3134/

... directly ties in with Greg Egan's _Quarantine_.

(Jurer gur fbyne flfgrz unf orra ybpxrq vagb na negvsvpvny rirag
ubevmba ol fbzr cbjreshy nyvra ragvgl orpnhfr jura uhznaf ybbx ng
guvatf, yvxr gur fgnef, jr pbyyncfr gur jnir shapgvba, rssrpgviryl
qrfgeblvat gur pbfzbf. Bbcf.)
--
Christian "naddy" Weisgerber naddy@mips.inka.de
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From Newsgroup: rec.arts.sf.written

Lynn McGuire <lynnmcguire5@gmail.com> writes:

xkcd: Sea Level
https://xkcd.com/3135/

Yup, constantly changing with enormous energies expended.

Approximately 3TW.

Unfortunatly, uniformly distributed across the planet,
which means it would be difficult to capture that energy
and convert it to something useful (e.g. electricity).

The "Capacity Factor" for capturing that energy is
about 24% (tidal power can only be captured half
the time). Cost is approximately $9 per average
watt, about the same as Nuclear.

It is a niche player, and always will be.

(source: section 16.2, https://escholarship.org/uc/item/9js5291m#page=182)

Later on in the chapter:
"The foregoing text already worked out that P/l for these wave pa-
rameters is 3,750 W/m. Now we just need to multiply by a coastline
length. The Pacific coast of the U.S. is approximately 2,000 km long.
Multiplying 3,750 W/m by 2,000,000 m yields 7.5 GW.
Getting 7.5 GW on the Pacific coast, and maybe a similar amount on the
Atlantic coast for a total of 15 GW is nothing to sneeze at. But consider
that the U.S. electricity demand is about 450 GW, and various alternatives
already top the upper limit of wave potential, as shown in Table 16.3.27

Note that wind and solar are growing
year by year, so their ultimate numbers will
be significantly higher, still.

Also, to get 15 GW from waves would require extracting all the wave
energy from the U.S. coasts. Sorry surfers. Sorry marine life who depend
on the waves for stirring nutrients and other functions a physicist can
only guess. The point is that when a fully developed wave energy resource
only provides a few percent of demand, while a promising thing like
solar is already roughly matching it and has ample room to grow, we
can be pretty confident that wave power will not become an important
player.
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From Newsgroup: rec.arts.sf.written

On 8/31/2025 10:35 AM, Scott Lurndal wrote:

Lynn McGuire <lynnmcguire5@gmail.com> writes:

xkcd: Sea Level
https://xkcd.com/3135/

Yup, constantly changing with enormous energies expended.

Approximately 3TW.

Unfortunatly, uniformly distributed across the planet,
which means it would be difficult to capture that energy
and convert it to something useful (e.g. electricity).

The "Capacity Factor" for capturing that energy is
about 24% (tidal power can only be captured half
the time). Cost is approximately $9 per average
watt, about the same as Nuclear.

It is a niche player, and always will be.

(source: section 16.2, https://escholarship.org/uc/item/9js5291m#page=182)

Later on in the chapter:
"The foregoing text already worked out that P/l for these wave pa-
rameters is 3,750 W/m. Now we just need to multiply by a coastline
length. The Pacific coast of the U.S. is approximately 2,000 km long.
Multiplying 3,750 W/m by 2,000,000 m yields 7.5 GW.
Getting 7.5 GW on the Pacific coast, and maybe a similar amount on the
Atlantic coast for a total of 15 GW is nothing to sneeze at. But consider
that the U.S. electricity demand is about 450 GW, and various alternatives
already top the upper limit of wave potential, as shown in Table 16.3.27

Note that wind and solar are growing
year by year, so their ultimate numbers will
be significantly higher, still.

Also, to get 15 GW from waves would require extracting all the wave
energy from the U.S. coasts. Sorry surfers. Sorry marine life who depend
on the waves for stirring nutrients and other functions a physicist can
only guess. The point is that when a fully developed wave energy resource
only provides a few percent of demand, while a promising thing like
solar is already roughly matching it and has ample room to grow, we
can be pretty confident that wave power will not become an important
player.

You seem to be confusing wave power and tidal power. The cartoon is
about tides, as is Lynn's post.

Tidal power is already a (very) small player in energy generation, but
it is limited to coastal areas with favorable geographies. Tidal barrage
system are most common at the moment, but tidal stream systems
(essentially underwater windmills) are probably usable in more places.

pt
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Cryptoengineer <petertrei@gmail.com> writes:

On 8/31/2025 10:35 AM, Scott Lurndal wrote:

Lynn McGuire <lynnmcguire5@gmail.com> writes:

xkcd: Sea Level
https://xkcd.com/3135/

Yup, constantly changing with enormous energies expended.

Approximately 3TW.

Unfortunatly, uniformly distributed across the planet,
which means it would be difficult to capture that energy
and convert it to something useful (e.g. electricity).

The "Capacity Factor" for capturing that energy is
about 24% (tidal power can only be captured half
the time). Cost is approximately $9 per average

You seem to be confusing wave power and tidal power. The cartoon is
about tides, as is Lynn's post.

I was responding to the "enormous energies expended", but as you
note, wave and tidal are two different classes of generation.

Tidal power is already a (very) small player in energy generation, but
it is limited to coastal areas with favorable geographies. Tidal barrage >system are most common at the moment, but tidal stream systems
(essentially underwater windmills) are probably usable in more places.

Indeed. Also covered by Dr. Murphy, amounts to another niche player.
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